Designed to be a quick reference guide for customers, the Righton Blackburns glossary provides definitions of the latest metal industry terms.

Just use the index or select the material type you are looking for.


Abnormal Steels (Metallurgical)
  • Carbon steels showing relatively poor low deformation creep behaviour usually as indicated by abnormally high creep rates. This usually occurs when high aluminium additions are made and is thought to be associated with removal of nitrogen from solid solution as AIN.
  • A name given by McQuaid and Ehn to carburizing steels which tended to show soft spots on quenching after carburizing. The cause is low hardenability associated with fine grain size.
Acid Steel (Metallurgical)

A steel melted in a furnace with an acid lining, i.e., consisting of a siliceous refractory such as ganister or sand, and under a siliceous slag. Neither sulphur nor phosphorus is removed to any appreciable extent during the process and for this reason a higher grade of raw material is required than in the basic process. Acid steel may be produced either by the open hearth, Bessemer or electric processes.

Admiralty Brass (Copper)
A nominal 70% Copper / 30% Zinc Brass with 1% Tin added to improve corrosion resistance.
Ageing (Carbon & Alloy Steels)

(Age Hardening). A process causing structural change which may occur gradually in certain metals and alloys at atmospheric temperature (natural ageing), or more rapidly at higher temperatures (artificial ageing). As a result of ageing, the proof stress, maximum stress and hardness values are increased, with some reduction in ductility. These effects are caused by precipitation from a supersaturated solid solution so that the ageing treatment is usually preceded by a solution treatment at a much higher temperature. The precipitate may be sub-microscopic. There is a tendency to apply the term "ageing" to steels; "age hardening" to non-ferrous alloys. Where the ageing is produced by heating at elevated temperatures, i.e., artificial ageing, the effect is often referred to as precipitation hardening.

Ageing, Age Hardening, Precipitation Hardening (Aluminium)

The second stage in the process (solution treatment and ageing) for those aluminium alloys that respond to heat treatment as a means of increasing their mechanical properties. It entails the precipitation of a constituent from a supersaturated solid solution. The rate of precipitation, and hence ageing, is both temperature and time dependent, with some alloys ageing at room temperature. It is more usual to perform ageing at higher temperatures. It should be noted that routinely operating aged alloys at unusually high ambient temperatures will permit further ageing and even over ageing leading to loss of properties.

Related Terms: Aluminium Alloy Classifications
Air Hardening Steels (Carbon & Alloy Steels)

(Self Hardening). Strictly the term refers to a steel which becomes martensitic, i.e., fully hardened, on cooling in air from above its critical point, and does not require rapid quenching in oil or water, but it may also be applied to varying degrees of non-martensitic hardening, e.g., where the steel, although not wholly martensitic, attains adequate hardness on cooling in air. Such steels are produced by the addition of certain alloying elements which lower their critical range on cooling; a typical example contains 0.30% carbon, 1.3% chromium and 4.5% nickel. It should be noted that sufficiently rapid air cooling can be obtained only if the mass of the steel does not exceed a certain section which varies according to the composition.

All-Over Marking (Aluminium)

A method of identifying sheet, plate and strip by printing at close intervals over the surface the name or symbol of the manufacturer, the relevant specification number and, in some cases, the temper and thickness of the material.

Allotropy (Metallurgical)

The property possessed by some elements of existing in two or more states (allotropes), differing widely in properties and each stable within certain limiting conditions of temperature and pressure, e.g., carbon has three allotropic varieties, diamond, graphite and amorphous carbon. The allotropy of iron modifies the solubility of carbon, and it is due to this fact that steel can be hardened. Pure alpha iron (ferrite) exists up to 910oC and pure gamma iron (austenite) from 900oC-1405oC Above 1405oC and up to the melting point of 1537oC it exists as delta iron. These temperatures are modified by alloy additions so that in certain steels, e.g., Staybrite and 14% manganese steel, the austenitic condition is stable at room temperature. The lattice of the alpha and delta iron is body centred cubic whilst that of gamma iron is face centred cubic.

Alloy (Aluminium)
A combination of two or more metals, or of metals and other elements. An alloy is formed by adding the 'alloying elements' to the 'parent' metal in the molten state. The parent metal usually accounts for more than 50% of the resultant mixture. Stainless Steel is an alloy of Iron plus Chromium (minimum 10.5%) with a small amount of Carbon plus various other elements (such as Nickely, Molybdenum, Titanium, Manganese) depending upon the grade.
Alloy Steel (Carbon & Alloy Steels)

A steel to which one or more alloying elements other than carbon have been deliberately added with the object of conferring particular properties upon it, such as strength, ductility and hardenability.

Alloying Element (Aluminium)

An element intentionally introduced in controlled quantity into a base metal or an alloy.

Alocroming, Chromating, Alocrom (Aluminium)
A family of proprietary chemical conversion coating processes based on chromate (hexavalent chromium) solutions that act as a surface pre-treatment before painting or insulation foaming. This also increases the corrosion resistance. More environmentally benign processes based on trivalent chromium are being introduced.
Alpha Brass (Copper)
A Brass whose microstructure consists only of the 'alpha phase' in which the Zinc is in solid solution within the Copper matrix. This occurs in the range from pure Copper to about 64% Copper - 36% Zinc. Alpha Brasses have good cold-working properties.
Alpha Iron (Metallurgical)

The allotropic form of iron, which in pure iron is stable below 910o C., the atoms being arranged in a body centred cubic space lattice. It is magnetic below the magnetic change point, which, in pure iron, occurs at 770o C. Above the magnetic change point, it was formerly known as beta iron.

Alpha-Beta Brass (Copper)
A Brass containing over 36% Zinc, or with other additions, that has both alpha and beta phases present in its microstructure.
Related Terms: Duplex Brass
Alumina (Aluminium)

Aluminium Oxide – A white powder that is produced from the aluminium ore Bauxite and then smelted to produce aluminium metals.

Related Terms: Hall Heroult Process
Aluminium Alloy (Aluminium)

A metallic substance, consisting of an intentional admixture of elements, the predominant element being aluminium.

Aluminium Alloy Classifications (Aluminium)

Wrought aluminium alloys are specified in British, European and other National standards and are classified in an agreed 4 digit system.

They fall into 2 distinct sub groups:-

1xxx, 3xxx and 5xxx series that develop strength by cold working, the number will be followed by the digit H and other numbers referring to the degree of annealing or cold work, e.g. 3105H22.

2xxx, 6xxx, 7xxx and 8xxx alloys that develop properties by solution treatment and precipitation hardening. The number is usually followed by a T and a number, defining the heat treatment condition of the alloy, e.g. 6082T6.

Thus the 4 digits, the letter and following digits for a product clearly define the chemical composition and the mechanical properties of that material.

Related Terms: Temper Designations
Aluminium Bronze (Copper)

Not true Bronzes as they contain no Tin, Aluminium Bronzes are alloys of Copper with 5 - 12% Aluminium, some having additions of Iron, Nickel, Manganese and Silicon. They are available in cast and wrought form with designations such as CA104, Defence Standard (NES) 83. Aluminium Bronzes combine high strength with excellent corrosion and shock resistance. Widely used for stressed components in corrosive environments they are, in particular applications, frequently technically sound, cost effective, alternatives to Stainless Steels and Nickel Alloys.

Angle (Aluminium)

The relative orientation of two adjacent faces of a section generally measured over the full length of both.

Annealing (Carbon & Alloy Steels)

Heating steel and holding it at a suitable temperature followed by cooling at a suitable rate, with the object of improving softness, machinability, and cold-working properties or of removing stresses and obtaining a desired structure. Usually (full annealing) the steel is heated to a temperature at which the carbide is wholly or partly taken into solution; subsequently the steel is slowly cooled, generally in the furnace. Sub-critical annealing is done at a temperature just below that at which carbide commences to be taken into solution.

Annealing (Stainless Steel)

A heat treating operation wherein the metal is heated to a temperature above its critical range, held at that temperature long enough to allow full recrystallization, then slowly cooled through the critical range. Annealing removes working strains, reduces hardness, and increases ductility.

Annealing (Aluminium)

Thermal treatment intended to soften a metal or alloy hardened by cold work or artificial ageing.

Annealing (Copper)

Full Annealing is a heat treatment process for fully softening Copper and Copper Alloys. It involves heating to 500-550oC and holding for an appropriate time.

Partial annealing is used to leave some residual temper such as quarter hard or half hard.

Anode (Stainless Steel)
The electrode in an electrochemical, or corrosion, cell from which a current flows into the cell. In corrosion processes material is dissolved at the anode.
Anodic Protection (Stainless Steel)
Electrochemical corrosion protection, achieved by increasing the electrode potential of the steel.
Anodising (Aluminium)
An electrochemical method for artificially thickening the naturally occurring oxide surface film on Aluminium and Aluminium Alloy surfaces ti improve appearance and/or corrosion resistance. Not all alloy grades are suitable for decorative anodising, with the general rule being the purer the aluminium, the better it will anodise. The thickness and other film characteristics can be controlled to meet varied requirements for improved corrosion resistance, improved abrasion resistance, electrical insulation or as a pre-treatment for subsequently applied coatings. Colour can also be applied using dyes. Anodising film thickness is typically 5 to 25 microns.
Related Terms: Anodising Quality Material
Anodising Quality Material (Aluminium)
Material with characteristics that make it suitable for decorative anodising after a suitable preliminary treatment
Anodising Test (Aluminium)

A non-destructive test for detecting certain defects in material that is anodized and rinsed. If cracks or other superficial flaws are present in the material they retain some of the chromic acid solution which subsequently seeps out and stains the anodic film

Architectural Anodising (Aluminium)

Anodizing to be used in permanent, interior, exterior and static situations where both attractive appearance and long life are essential.

Architectural Bronze (Copper)
A confusing, loose, but widely used term used to describe a number of brasses. • Those, whose colour mimics that of Bronzes, that are used in architectural applications, such as decorative shop fittings, window frames, etc, • The Manganese containing brass CZ136, which is also incorrectly called Manganese Bronze, is a High Tensile Duplex Brass which extrudes well and has a warm 'chocolate' colour. • The term is also applied to Gilding Metals which have been chemically toned to give a 'bronze' finish.
Related Terms: Manganese Bronze
Arrested Mandrel (Aluminium)

A mandrel attached to an auxiliary extrusion ram. As the main ram moves forward the mandrel is held stationary in the die, resulting in a product of uniform wall thickness along the length.

Arsenical Brass (Copper)
A 70% Copper/30% Zinc alpha brass that contains Arsenic, and frequently Aluminium. It has better corrosion resistance than cartridge brass, but similarly excellent forming properties.
Artificial Ageing, Precipitation Treatment (Aluminium)
The thermal treatment of an alloy that increases the hardness and strength by precipitation of constituents from the super-saturated solid solution at above room temperature.
Related Terms: Ageing
As-Quenched Condition (Aluminium)
The condition of an alloy during the time immediately following the quench and before the mechanical properties have been significantly raised by precipitation hardening (ageing).
As-welded (Stainless Steel)
Tubular products made by continuously welding formed strip that were not subject to a heat treatment such as annealing after welding.
ASTM (Copper)
The American Society for Testing and Materials. ASTM produces Standards for materials and test methods that are widely used other than in the USA.
Austempering (Metallurgical)

An interrupted quenching process which consists essentially of heating steel to an appropriate temperature above the critical range to render it austenitic and then, instead of cooling it to room temperature in one of the conventional cooling media, transferring the steel to a hot quenching bath maintained at a predetermined, constant temperature below the critical range, but above the martensitic change point (Ms point) usually between 260o and 370oC; the steel is held at this temperature for a certain time to ensure the complete direct transformation of the austenite in the final products (e.g., pearlite and/or bainite), after which the material may be cooled to atmospheric temperature in any convenient manner. (See also Critical Cooling Rate).

Austenite (Stainless Steel)
A face centred cubic (FCC) phase found in all steels. In most carbon and low alloy steels it is present only above 760oC. In austenitic stainless steels their chemical composition stabilises austenite to room temperature and even cryogenic temperatures. Austenite is non-magnetic.
Austenite (Metallurgical)

The allotropic form of iron (gamma iron) which has a face centred cubic lattice, the parameter of which increases with increasing carbon content. Austenite, containing only carbide of iron in solution, is not stable at ordinary temperatures, nor can it be completely retained in solution by quenching, but its stability is greatly increased by the addition of certain alloying elements.

Austenitic Stainless Steel (Stainless Steel)
Stainless Steels that contain a minimum of 18% Chromium and sufficient Nickel, or a combination of Nickel, Manganese and Nitrogen, to stabilise the face centred cubic (FCC) phase austenite down to cryogenic temperatures – This phase is normally present only above 760oC in most steels, These steels are, except in very particular circumstances, non-magnetic and have good ductility but relatively high work hardening rates. They have excellent corrosion resistance to most environments, although susceptible to stress corrosion cracking (SCC) above 60oC. Pitting and crevice corrosion can occur in chloride environments except with Type/Grade 316 where the Molybdenum content inhibits, but cannot always fully prevent, these problems. They cannot be hardened by heat treatment - The mechanical properties can only be increased by cold working.
Austenitic Steels (Metallurgical)

Steels consisting of austenite, which, owing to the presence of high percentages of certain alloying elements such as manganese and nickel, are stable, for most practical purposes, at normal temperatures. Typical examples of austenitic steels include 14% manganese steel, and the corrosion-resistant type containing about 18% chromium and 8% nickel, e.g., Staybrite.


B/H Loop (Metallurgical)

(Magnetic hysteresis and hysteresis curve). A closed figure formed by plotting magnetizing force against flux density for a magnetic material when the magnetizing force is taken through a complete cycle of increasing and decreasing values. The area of the figure is proportional to the magnetic hysteresis loss.

Back Extrusion (Aluminium)

A process in which a heated ingot in an enclosed container is extruded backwards over the mandrel and supporting stem.

Back-End Defect (Aluminium)
A defect found in extruded products due to incorrect extrusion procedures at the mill.
Bainite (Metallurgical)

An acicular aggregate of ferrite and carbide particles formed when austenite is transformed at temperatures in the intermediate range, i.e., above the martensite range and below the pearlite range. The structure of bainite varies with the composition of the austenite from which it is formed and with the temperature of its formation. (See Austempering).

Balanced Steel (Metallurgical)

Steel in which the deoxidation is so controlled that the evolution of gas during solidification approximately balances the shrinkage normally occurring. Thus no pipe cavity is produced and a high yield of usable metal can be obtained on rolling the ingot.

Banded Structures (Metallurgical)

Light and dark parallel bands revealed by etching and formed by the elongation of segregated areas during rolling or forging.

Bar (Aluminium)

A round, rectangular or regular polygonal solid section supplied in straight lengths. The term is applied to materials of not less than 6mm diameter or minor dimension.

Barrelling (Aluminium)

The treatment of articles in a rotating tumbling container in the presence of abrasives and water for deburring or to produce a variety of surface textures.

Base Metal (Metallurgical)

(a) A metal which becomes oxidized when heated in air, e.g., copper, lead, zinc, and tin, as distinct from a noble metal such as gold and platinum.

(b) In electro-metallurgy, a metal at the lower end of the electro-chemical series.

(c) The preponderant metal in an alloy.

(d) The metal to be welded or cut.

Basic Steel (Metallurgical)

Steel produced in an open hearth or Bessemer or electric furnace in which the hearth consists of a basic refractory such as rammed magnesite or dolomite. A slag, rich in lime, is produced and the sulphur and phosphorus pass into the slag during the working of the charge. The charge of the basic open hearth furnace consists of pig iron and scrap. In the hot-metal process, iron from the blast furnace goes through the mixer to the open hearth furnace, and constitutes 75% or more of the charge, the rest being scrap. In the scrap process, the basis of the charge is scrap steel. This may be up to 85% of the charge, the remaining 15% being pig iron. In either case, however, the refining of the metal consists of the removal of some of the carbon and the partial elimination of sulphur and phosphorus, the manganese changes which occur being incidental to the process.

Batch (Aluminium)

Consignment, or a part thereof, comprising products of the same grade or alloy, temper and thickness or cross section, processed in the same manner.

Bauschinger Effect (Metallurgical)

The decrease in compressive yield strength and increase in tensile yield strength obtained when a metal is plastically strained in tension beyond its yield point.

Bauxite (Aluminium)
The main ore of aluminium, found in great abundance in the earth’s crust, near the surface. It is mined using open cast mining and has a yield of 25%.
Bayer Process (Aluminium)
A chemical process used to refine the aluminium ore bauxite into alumina (aluminium oxide) from which the aluminium metal can be extracted by smelting
Becking (Carbon & Alloy Steels)

Increasing the diameter of a steel ring or drum by forging on a becking bar, or mandrel, the forging being worked radially between the bar and the upper tool.

Bend Radius (Aluminium)
The radius of curvature of the former around which a specimen is bent.
Bend Test (Aluminium)
The bending of a specimen to conform with a predetermined radius and angle, to assess bending characteristics and ductility.
Bend Test (Metallurgical)

A test in which a standard specimen is bent through a specified arc to determine the degree of ductility and the soundness of internal structure.

Beryllium Copper (Copper)
Copper alloys with 1.5 to 2% Beryllium additions that have the highest strengths of all Copper Alloys by both heat treatment (solution treatment and age hardening) and cold working.
Beta Brass (Copper)
A brass with very high Zinc content. It will have a predominantly beta phase microstructure, be brittle and used only as a brazing filler alloy.
Beta Phase (Copper)
A phase in the microstructure of brasses that contain more than about 36% Zinc. Beta phase adversely affects the cold formability of brasses and hot working processes, such as hot stamping, are preferred.
Related Terms: Alpha-Beta Brass, Duplex Brass
Billet, Bloom (Stainless Steel)
A rolled or forged semi-finished product intended for further working by re-rolling or forging. Billets are usually square with chamfered or radiused corners.
Related Terms: Slab
Billet, Bloom (Aluminium)
Cast aluminium in the form of large round (or occasionally square) bars.
Bite Mark (Aluminium)

A mark on the roll coating caused by the initial feeding of the ingot, which is subsequently transferred to the hot rolled slab.

Blank (Aluminium)
A work-piece prepared for subsequent processing e.g. by forming, bending, cupping, drawing, impact extrusion, pressing, etc.
Blanking (Aluminium)

The production of circles and other shapes by shearing on a blanking press.

Blanking Die (Aluminium)

A die used for shearing circles and other blanks.

Blanking Press (Aluminium)

A press used for shearing blanks from plate, sheet or strip.

Blast Cleaning (Aluminium)

The projection of abrasive grit, sand, small grit blasting particles of steel, glass or other materials, sand blasting or a mixture of abrasive grit, water and air, shot blasting to strike the surface of an article in order vapour blasting to clean it. A matt or satin finish is produced, depending upon the particle size used.

Blister (Aluminium)

A raised area on the surface of the metal caused by the expansion of a gas enclosed in a sub-surface void.

Blister Copper (Copper)
Copper of about 98% purity obtained by 'converting' copper matte.
Related Terms: Copper Matte, Converting Process
Blowholes (Carbon & Alloy Steels)
  1. Round or elongated smooth walled gas-filled cavities in solid metals formed either by the trapping of gas evolved during solidification of the metal or by steam or gas from the mould surface.
  2. Gas Pocket). A cavity in a weld caused by the entrapment of gas
Blue Annealing (Carbon & Alloy Steels)

A process of softening iron-base alloys in the form of hot-rolled sheet, in which the sheet is heated in the open furnace to a temperature within the transformation range and cooled in air; the formation of a bluish oxide on the surface is incidental.

Blue Brittleness (Metallurgical)

The loss of ductility found on testing steel in the blue heat range which varies between about 200oC and 400oC according to the composition of the steel. This embrittlement is shown by the increase in maximum strength and decrease in the elongation, reduction of area and impact value. If steel is deformed at room temperatures, heated in the blue heat range and then tested at normal temperatures, the loss of ductility is revealed by the impact test rather than by elongation. The term blue brittleness is derived from the fact that blue oxide films are formed on polished steel within the range of temperature in question.

Blueing (Carbon & Alloy Steels)

A treatment of the surface of iron-base alloys usually in the form of sheet or strip, on which, by the action of air or steam at a suitable temperature, a thin blue oxide film is formed on the initially scale-free surface. It is used to improve the appearance and to increase resistance to corrosion

Body Centred Cubic Lattice (Metallurgical)

A lattice in which atoms are present at the corners of each cube or rectangular prism, with one atom in the centre of such cube or prism. The unit cell contains two atoms, because each corner atom is shared by seven other cubes

Bond Blister (Aluminium)

A blister at the interface between the coating and the core of clad products.

Bore Test (Aluminium)

A test on tube to verify freedom from constriction by passing a metallic bob or wire of specified dimensions through the tube.

Bored Extrusion Ingot (Aluminium)

An extrusion ingot with a central bored extrusion billet longitudinal hole produced by machining.

Bow (Aluminium)
The deviation of the edges from the true longitudinal axis of a product seen as an arc.
Brass (Copper)
Any alloy of Copper and Zinc.
Related Terms: Alpha Brass, Alpha-Beta Brass, Duplex Brass, Architectural Bronze, Cartridge Brass
Brazing Rod (Aluminium)

Rod of an alloy with a low melting range for use as filler metal in brazing.

Brazing Sheet, Strip & Wire (Aluminium)

Sheet of a low melting range alloy or clad with a low melting range alloy, used for brazing.

Strip of a low melting range alloy or clad with a low melting range alloy, used for brazing.

Wire of an alloy with a low melting range for use as filler metal in brazing.

Bright Annealing (Carbon & Alloy Steels)

A process of annealing which is usually carried out in a controlled furnace atmosphere (i.e., non-oxidizing) so that surface oxidation is reduced to a minimum and the surface remains relatively bright.

Bright Annealing (Stainless Steel)
Annealing performed in a furnace with an inert atmosphere so that no scale is formed and the resulting surface has a bright finish.
Related Terms: Annealing
Bright Anodising (Aluminium)

Anodizing with brightness as a primary objective.

Brinnel Hardness (Metallurgical)

The measurement of a metal hardness (or the ability to resist penetration). A steel ball is forced into the surface of the material tested under a specific load. The diameter of the depression is measured, and the hardness is the ratio of the load to the spherical area of the impression.

Bronze (Copper)
Any alloy of Copper and Tin.
BSP, BSP Thread , Whitworth Thread (Stainless Steel)
British Standard Pipe Thread, also called Whitworth Thread, with 14 threads per inch.
Buckle, Ripple (Aluminium)
The variation in flatness represented by alternate bulges and hollows along the length of a rolled product, the edges of which remain reasonably flat.
Bull Block (Aluminium)

A machine for drawing rod, bar and tube in coil form through one die.

Burnt Steel (Metallurgical)

The term is usually applied to a condition in which visible oxide films are formed at the crystal boundaries of the steel. This denotes that the steel has been heated almost to the solidus temperature and is, therefore, permanently damaged.

Burr (Aluminium)

A thin ridge of roughness on an edge left by a cutting operation such as slitting, trimming, shearing, blanking, sawing etc.

Busbars (Aluminium)
Bar or section for use as a common junction between electrical circuits.


Carbide (Stainless Steel)
A compound formed when an element, usually a metal, combines with Carbon. The carbides of metals are usually very hard. Both Iron and Chromium readily form carbides – Chromium has the greater affinity so will form its carbide in preference to Iron. This is a significant disadvantage in stainless steels as any carbide formation depletes the amount of chromium available to form the protective oxide layer. This is one reason why stainless steels have very low Carbon content (maximum 0.03% in low Carbon grades).
Related Terms: Sensitisation, Carbide, Stabilised Grades, Inter-granular Corrosion
Carbide (Metallurgical)

A chemical combination of carbon with iron or any other elements, e.g., Fe C (cementite). Metallic carbides are hard and brittle; certain of them, of which the principal are tungsten carbide and titanium carbide, are the chief constituents of the hard metals used for cutting tools.

Carbide Precipitation (Stainless Steel)
This occurs in an alloy when the thermal conditions and processing allow one or more of the constituents react with any available Carbon to form discrete particles within the microstructure. Usually this is undesirable in austenitic and ferritic stainless steels as chromium carbide is formed preferentially and compromises the corrosion resistance.
Carbon Case Hardening (Carbon & Alloy Steels)

A steel whose properties are determined primarily by the percentage of carbon present. Besides iron and carbon, such steels may contain a maximum of manganese up to 1.5%, silicon up to 0.5%., sulphur and phosphorus up to 0.1%, nickel up to 0.40%, chromium up to 0.30%, molybdenum up to 0.15%, copper up to 0.25%, tungsten, cobalt, aluminium up to 0.10, and niobium, tantalum, titanium, vanadium, zirconium up to 0.05%. These alloying elements in such quantities are regarded as residual elements, but their deliberate addition in substantial amounts will put the steel in the alloy steel category. (see also Carbon-"Influence of Elements in Steel").

Carbon Steel (Metallurgical)

A steel whose properties are determined primarily by the percentage of carbon present. Besides iron and carbon, such steels may contain a maximum of manganese up to 1.5%, silicon up to 0.5%, sulphur and phosphorus up to 0.1%, nickel up to 0.40%, chromium up to 0.30%, molybdenum up to 0.15%, copper up to 0.25%, tungsten, cobalt, aluminium up to 0.10% and niobium, tantalum, titanium, vanadium, zirconium up to 0.05%. These alloying elements in such quantities are regarded as residual elements, but their deliberate addition in substantial amounts will put the steel in the alloy steel category.

Carbonitriding (Metallurgical)

A case hardening process in which steel is heated in an atmosphere containing both carbon and nitrogen. Steels of the case hardening type are normally used, and since the absorption of nitrogen depresses Ac and increases hardenability the temperature and alloy content need not be so high as those used in case carburizing. A typical treatment would be: heat at 825oC for two hours in a carburizing gas to which about 10% anhydrous ammonia has been added, and quench in oil: but many variations of these conditions can be employed to give the required depth and hardness of case.

Carburizing (Metallurgical)

The introduction of carbon into the surface layer of a steel having a low carbon content (case hardening steel). It may be effected by heating in a solid, liquid or gaseous carbon-containing medium, which at high temperatures provides a supply of carbon for absorption by the material being carburized. By controlling the temperature and time of treatment, the concentration of carbon in the surface of the steel and the depth of penetration may be varied over wide limits. In the original process of box- or pack-carburizing, the steel is heated to the necessary temperature in a solid carburizing compound, usually a mixture of hardwood charcoal and an oxide or carbonate of the alkalies or alkaline earths. Gas carburizing is finding increasing use because it gives better control over the carbon content of the case.

Cartridge Brass (Copper)
A 'straight' 70% Copper / 30% Zinc brass with excellent cold forming and deep-drawing properties. So called because it was originally used deep-draw cartridge cases it now has a wide range of industrial applications, particularly if severe deformation, such as spinning or flanging, in involved. Arsenical Brass may be preferred because of its superior corrosion resistance.
Cast (Aluminium)

Metal taken from the same melt in a furnace or crucible, or of several melts mixed in the same furnace or crucible before pouring, or metal taken from a furnace without subsequent addition (when a continuous melting process is used). In the case of continuous or semicontinuous casting procedures this is also regarded as the product of a cycle up to 24hr where the same alloy and shape is cast.

Cast Iron (Metallurgical)

Iron with a total carbon content varying between about 1.8 and 4.5%, the carbon being present in excess of the amount which can be retained in solid solution in austenite at the eutectic temperature. In addition to carbon, there are also present, varying amounts of silicon, manganese, sulphur and phosphorus. These irons can normally be divided into the following types:- Grey cast iron, in which all or part of the carbon content is in the form of graphite distributed through the metal as flakes which are responsible for the inherently poor shock-resistance and relatively low mechanical properties of the material; White cast iron, in which practically the whole of the carbon is retained in chemical combination with the iron as carbide of iron, Fe C. This compound has a silver-white colour and the fractures of the cast iron are white. White iron is very hard and brittle and practically unmachinable, and is used chiefly as an intermediate product in the production of malleable iron castings or a thin hard layer on the surface of a softer iron casting; Malleable cast iron is cast white and then annealed at about 850oC to remove carbon (White-heart process) or to convert the cementite to rosettes of graphite (Black-heart Process). It is distinguished from grey and white cast iron by exhibiting some elongation and reduction of area in a tensile test; Spheroidal Graphite cast iron, in which, as the name implies, the graphite is in spheroidal form instead of flakes, as found in grey cast iron. The production of this iron involves the addition of an appropriate amount of either magnesium or cerium to the molten iron shortly before casting. The mechanical strength is doubled and such castings show measurable ductility and greatly increased shock resistance. Alloy Cast Iron contains a specially added element or elements in amounts sufficient to produce a measurable modification of the physical properties.

Cast Steel (Metallurgical)

(a) A term, originally applied to crucible steel to distinguish it from shear steel, and still used for high carbon tool steel;

(b) The term also covers steel which has solidified from the molten condition in a mould and hence undergoes no further change of shape, e.g, by forging or rolling, except for such minor modifications as may be involved in machining.

Cast, Heat, Melt (Aluminium)
These terms are used interchangeably to refer to the product of a single melting furnace charge. Sometimes the furnace contents are tapped into two or more ladles when the product of each ladle may be called a separate cast. It is always assumed that the chemical composition of an entire cast will be uniform. This is described as the “cast analysis” on a Certificate of Conformity etc.
Cast, Heat, Melt (Stainless Steel)
These terms are used interchangeably for the product of a single melting or refining furnace charge. Occasionally, if the furnace contents are cast into a number of different forms, these may be called separate casts.
Casting, Ingot Casting (Copper)
The pouring of molten metal into a mould or die where it is allowed to solidify. When solidified, the resultant 'casting' takes on the shape and approximate dimensions of the mould. Examples • Ingot for forging or other hot working • Intermediate uses include extrusion billets, slabs for rolling, forging blanks. • End use: valve body.
Cathode (Stainless Steel)
The electrode in an electrochemical cell, through which positive electric current leaves an electrolyte. The electrode reaction at a cathode is a reduction of ions or molecules in the electrolyte by electrons emitted from the cathode. In corrosion processes, reduction of dissolved oxygen and emission of hydrogen are two common reactions. The current flow causes positive ions to migrate towards the cathode.
Cathode Copper, Copper Cathode (Copper)
The Copper, of at least 99.9% purity, produced by electrolytic refining. It is the feedstock for melting most Copper alloys and their subsequent manufacturing processes.
Cathodic Protection (Stainless Steel)
Electrochemical corrosion protection achieved by lowering the electrode potential.
Caustic Embrittlement (Metallurgical)

A type of intercrystalline stress corrosion cracking produced below the liquid level in mild steel and low-alloy steel boilers. Failure is at riveted joints or crevices where concentration of caustic can occur associated with a high internal or external stress. Welded boilers are normally free from this type of attack.

Cementation (Metallurgical)

(a) The process of introducing elements into the outer layer of metal objects by means of high temperature diffusion.

(b) (Converting process). In this process, best quality Swedish wrought iron bars were packed in layers separated and surrounded by charcoal in pots, which were slowly heated to a temperature of about 1100o C. and maintained at that temperature for a period of 7 to 10 days according to the desired carbon content, and then allowed to cool slowly, the whole process occupying about three weeks. During this operation, carbon provided by the charcoal, diffused into the iron, and some of it, reacting with the slag content of the wrought iron, liberated carbon monoxide which formed blisters on the surface of the bar, hence the name blister bar, and blister steel; or converted or cemented bar, or cemented steel, or plated bar. Some six of these were then piled together, placed in a clip, raised to a white heat, and hammered into a faggot or small bloom. This was known as single shear steel. For the production of double shear steel, the faggot was nicked, bent back on itself, reheated and hammered down again to its original size. The process is now obsolete; the last cementation furnace in the country is now preserved at the Sheffield laboratories of BISRA.

Cementite (Metallurgical)

The iron carbide (Fe C) constituent of steel and cast iron. It is hard, brittle and crystalline and contains 6.67% of carbon by weight.

CEN (Copper)
Comité Européen de Normalisation, aka European Committee for Standardisation. The body responsible for developing European Standards, often referred to as ‘Euro-Norms or EN for short.
Centrifugal Casting (Carbon & Alloy Steels)

Casting process that consists of pouring molten metal into the cavity of a rotating mould, which can be made of various metals.

Centrispinning (Carbon & Alloy Steels)

The introduction of liquid metal into a rapidly rotating mould so that the metal is directed by centrifugal force to take up the shape of the mould.

Chalcocite (Copper)
A Sulphide ore of Copper with the chemical formula Cu2S. It is a highly valued ore since it approaches 80% Copper by weight.
Chalcopyrite (Copper)
An important ore of Copper. It is a Copper Iron Sulphite with the chemical formula CuFeS2.
Charpy Test (Metallurgical)

A notched-bar impact test in which a beam usually 10 mm. x 10 mm. in section supported at both ends, and having a notch in the middle of its length, is struck behind the notch by a striker carried on a pendulum. The energy absorbed in fracture is obtained from the height to which the pendulum rises. A notch with a depth of 2 mm. and rounded at the bottom to a diameter of 2 mm. is known as a Mesnager notch. A notch produced by drilling a hole usually 2 mm diameter and centre 4 mm. below one face with a saw cut from that face to the hole, is known as a keyhole notch. Other notches may be used, such as the Izod V-notch.

Chatter Marks (Aluminium)

Chatter marks

Regularly spaced superficial transverse markings produced by vibration between the metal and the working surface during fabrication.

Chemical Brightening (Aluminium)
A chemical treatment to improve the specular reflectivity of a surface.
Chemical Conversion Coating (Aluminium)
The treatment of material with chemical solutions by dipping or spraying to increase the thickness of the natural oxide film on the surface or to build up an oxide film bearing chromates or phosphates
Chill Casting (Aluminium)

A process in which molten metal is poured into a permanent mould and solidified.

Chromizing/Chromating (Metallurgical)

The production of a corrosion- and heat-resisting surface layer by the high temperature diffusion of chromium into iron or steel.

Circumscribing Circle (Aluminium)
A circle that will just contain the cross section of an extrusion, usually designated by its diameter.
Clad Material (Aluminium)
Material that has a thin layer of Aluminium or Aluminium alloy metallurgically bonded to it usually by rolling, extruding or drawing. Most often it is used to provide a more corrosion resistant surface or to facilitate anodising.
Clad Steels (Metallurgical)

Two dissimilar types of sheets or plates bonded together. The covering metal usually possesses greater corrosion resistance, as when mild steel is clad with stainless steel.

Cleavage Planes (Metallurgical)

Planes of easy fracture where cleavage usually occurs when the crystal is subjected to stress parallel to one or more of the faces of the system to which the crystal belongs. They are not necessarily related to the boundaries of the crystal, and are found in both minerals and metals.

A large crack in a block of metal caused by uneven contraction or expansion during cooling or heating.

Close Packed Hexagonal (Metallurgical)

An arrangement of atoms in crystals. (See Space Lattice).

Cold Compression (Aluminium)

Working of forged material at room temperature under compression through the thickness in the solution treated condition immediately after quenching to relieve internal stresses caused by quenching, and to minimize distortion during machining.

Cold Drawing (Stainless Steel)
Drawing hollow or solid products through a hardened steel or tungsten carbide die at room temperature. Cold drawing reduces the O.D. or wall thickness, or both. It produces smooth surface finishes and develops closer tolerances. Cold drawing increases hardness and mechanical properties. In welded hollow products it promotes weld area recrystallisation during subsequent annealing. Cold drawing of hollow sections is usually done with a mandrel in the bore (drawn over mandrel).
Cold Drawing (Carbon & Alloy Steels)

The process of reducing the cross-sectional diameter of tubes or wire by drawing through dies without previously heating the material.

Cold Rolling (Stainless Steel)
Passing sheet or strip at room temperature between a pair of rotating rolls. The reduction in thickness may be very light, as in the finishing process applied to hot rolled sheets, or heavy as in the cold rolling of narrow strip. Cold rolling improves surface finish, increases hardness and mechanical properties and develops tighter dimensional tolerances.
Cold Rolling (Carbon & Alloy Steels)

Rolling of metal or steel at room temperature to provide a smooth surface finish and/or enhanced tensile strength. (See Cold-Working).

Cold Working (Carbon & Alloy Steels)

A method of conferring strength by means of plastic deformation below the annealing or recrystallization temperature. This treatment may consist of cold rolling, hammering, drawing, pressing, heading, spinning, or swaging, usually at room temperature. The hardness and tensile strength are progressively increased with the degree of cold work, whilst the ductility and impact values are lowered. Where this increased hardness is not desired, the material is annealed at various stages between the cold working operations or it may be subjected to a final annealing. Steels containing 0.7-0.85% carbon are often cold worked until they possess a tensile strength of 120 tons/square inch, while piano wires may attain 150 tons/square inch or higher.

Cold Working (Aluminium)
The permanent alteration of shape or dimensions by plastic deformation at room temperature by, e.g., cold rolling, cold reduction, drawing, pressing, forming, bending, swaging, etc.. Cold working increases strength and hardness but reduces ductility.
Cold Working (Stainless Steel)
Changing the shape, dimensions, mechanical properties and surface finish of a work-piece by mechanical deformation at room temperature. It may be accomplished by rolling, forging drawing, pressing, forming, bending, swaging, etc.
Colour Anodising (Aluminium)
Incorporation of colouring matter (dyes) into the film of anodised Aluminium during the anodising process.
Common Brass (Copper)
A very widely used brass containing 63% Copper plus 37% Zinc. It is also known as CZ108, Basis Brass and 63/37 Yellow Brass. It can be hot or cold worked, has good ductility permitting cold heading of wire and rods and cold presswork but not deep drawing.
Concavity (Aluminium)

An inward curvature across the width of a surface of a rolled or extruded product.

Concentricity (Aluminium)
Strictly, this is the shift between the centres of the circles that are the Outside Diameter (OD) and Inside Diameter (ID/ Bore) of a round tube. Any such shift will cause a variation in wall thickness around the circumference of the tube, hence the tolerance on concentricity is determined by the wall thickness tolerance.
Concentricity (Stainless Steel)
In tubular products this describes how closely the centres of the two circles that respectively describe the outside diameter and bore coincide. The separation of these two centres causes variation in wall thickness around the tube and eccentricity.
Related Terms: Eccentricity
Container (Aluminium)
The key part of an extrusion press into which the billet is placed before extrusion. It is a hollow cylinder which is closed at one end by the die and at the other by the extrusion ram. It has to contain the substantial pressures generated during extrusion.
Continuous Casting (Carbon & Alloy Steels)

A method of producing cast slabs or billets in long lengths using a single water-cooled copper in crucibles holding about 56 lbs. It was the first process to produce steel in a molten condition, hence the product was called cast steel. It has been replaced by the high frequency process.

Contraction Cavities (Metallurgical)

Voids formed when the supply of molten metal fails at certain points. In well designed castings, the bulk of the contraction that accompanies the solidification is concentrated in the feeder heads and risers, from which molten metal flows to compensate for contraction in the casting proper. In steel ingots the contraction may result in the formation of pipe if feeding is inadequate.

Controlled Stretching (Aluminium)
Stretching, under controlled tension, of plate and shate products to a specified extension (percentage permanent set). It relieves internal stress and minimises distortion during machining as well as improving flatness and straightness.
Converting Process (Copper)
The process which transforms Copper Matte into Blister Copper. By reacting the Matte with Oxygen enriched air and silica slags both the Iron and Sulphur are removed leaving Copper metal of 98% purity known as Blister Copper.
Related Terms: Chalcopyrite
Cooling & Heating Curves (Metallurgical)

Graphs obtained by plotting time against temperature for a metal cooling or heating under constant conditions. Changes of rate resulting from the absorption or evolution of heat indicate phase changes.

Copper Matte (Copper)
The mixture of Copper and Iron Sulphides which is the feedstock to the Converting Process that turns Chalcopyrite ore into Blister Copper.
Related Terms: Converting Process, Chalcopyrite, Matte
Copper-Nickel, Cupro-Nickel (Copper)
Alloys of Copper and Nickel, with between 10% - 45% Nickel, and usually small quantities of Iron and Manganese. Copper Nickels have outstanding resistance to sea-water corrosion.
Coring (Metallurgical)

The microscopic segregation developed by the progressive freezing of zones successively richer in one metal when a liquid solution of two metals is solidifying to form a solid solution.

Corrosion (Stainless Steel)
Degradation of a material by chemical or electrochemical reaction with its immediate environment.
Corrosion Fatigue (Stainless Steel)
Cracking, possibly initiated and certainly accelerated, in a work-piece subjected to alternating or cyclic stresses in the presence of a corrosive medium. It will cause premature, often unexpected, failure.
Related Terms: Fatigue
Corrosion Fatigue (Metallurgical)

Corrosion combined with alternating or repeated stress accelerates the fatigue. The severity of the action depends upon the range and frequency of the stress, the intensity of the corroding conditions, and the time. The fracture is akin to a fatigue fracture, but may exhibit a characteristic discolouration, dark at the origin and grading away to a lighter shade with increasing distance from it.

Corrosion Product (Stainless Steel)
The residue, or product, that is formed when a corrosion reaction occurs.
CPP Plate (Stainless Steel)
CPP is short for Continuously Product Plate - CPP is hot rolled plate up to 12mm thick and will have been coiled up during the production by hot rolling as compared to Quarto Plate over 12mm thick that will not have been coiled during production by hot rolling. For more information and the stock range please click on the link below.
Related Terms: Quarto Plate
Creep (Copper)
The tendency of a metal to flow or deform permanently at under an applied load that is lower than its yield point. It is time and temperature dependent, the rate always increases with temperature.
Creep (Stainless Steel)
The tendency of a metal to flow or deform permanently under an applied load that is lower than its yield point. It is time and temperature dependent, the rate always increases with temperature.
Creep Test (Metallurgical)

A method of determining the plastic deformation of metals under a definite load at a definite temperature. Various criteria are used for assessing the behaviour of materials in a creep test, namely

(i) as a definite creep rate, e.g., between x and z hours (e.g., 24-72 or 25-35) or creep rate at 1000 hours.

(ii) total deformation in a certain period of time.

Owing to the lengthy nature of such testing where the service may extend to 10 years, or longer, considerable use is made of the extrapolation of creep test results obtained for relatively short times.

Crevice Corrosion (Stainless Steel)
Localised corrosion that occurs in narrow crevices where stagnant, non-aerated, liquid can accumulate. It is a particular problem with alloys, such as stainless steels, that rely on a passive film to protect them as these films are unstable in the presence of high concentrations of Chloride Cl- and Hydrogen H+ ions. The lack of aeration prevents the passive film from regenerating so attack can proceed. Good design is the key to preventing crevice corrosion.
Crevice Corrosion (Metallurgical)

(Shielding). This type of attack occurs in crevices as formed by washers, sleeves or bearings, etc., or at the edge of a protective coating. It is due to a concentration of corrosive media or by a depletion in oxygen resulting in an aeration cell.

Critical Cooling Rate (Metallurgical)

The term, as applied to steel, represents the slowest rate of cooling which allows the formation of martensite. In many cases this amounts to the rate of cooling which will just suppress the austenite/pearlite transformation. (See also Transformation Range).

Critical Points (Metallurgical)

The points of temperature at which changes of phase occur in steel. They are marked by the liberation of heat, recalescence, during cooling, and by absorption of heat, decalescence, on heating, thus resulting in halts or arrests on the cooling or heating curves. In steel there are several such points, the temperature for which depends largely on the composition of the steel. (See also Transformation Range).

Critical Quencing Rate (Aluminium)
The minimum mean cooling rate from the solution treatment temperature necessary to retain the alloying constituents in solid solution and thus permit the alloy to meet specified mechanical property requirements in the precipitation hardened (aged) condition.
Critical Temperature (Metallurgical)

(a) The temperature at which some change occurs in a metal or alloy during heating or cooling, i.e., the temperature at which an arrest or critical point is shown on heating or cooling curves.

(b) The temperature at which alpha iron loses its magnetic properties, i.e., about 770oC.

(c) The temperature above which a given gas cannot be liquefied.

Crystal Boundaries (Metallurgical)

The surfaces of contact between adjacent crystals in a metal. Anything not soluble in the crystals tends to be situated at the crystal boundaries, but in the absence of such a phase, the boundary between two similar metals is simply the region where the orientation changes.

Cup & Cone (Metallurgical)

A type of fracture occurring in tensile test pieces from steels possessing reasonable ductility, and containing no local abnormality where the necking occurs after maximum stress. The fracture gives one surface with a cup-like contour, and the other in the form of a cone, fitting the cup. This is accepted as evidence of toughness and uniformity of structure.

Cuppiness (Metallurgical)

An internal defect in wire-drawing which leads to fracture of the cup and cone type. It may be caused by excessive cold work (overdrawing) without adequate intermediate annealing or by segregation where the hard centre, being less ductile than the surface, tears and starts the fracture.

Cyaniding (Carbon & Alloy Steels)

(Cyanide Hardening). The process consists of introducing carbon and nitrogen into the surface of steel by heating it to a suitable temperature (e.g., 760-845oC) in a molten bath of sodium cyanide, or a mixture of sodium and potassium cyanide, diluted usually with sodium carbonate, and quenching in water or oil. The process is used where a very thin case of high hardness is required. An immersion of 5 to 10 minutes usually suffices.


Damping Capacity (Metallurgical)

This has been described as "elastic hysteresis" and "internal friction", but the word damping more suitably indicates the effect obtained when a material having the property in question is subjected to vibrations which are not maintained by external energy, e.g., if a steel bar supported at one end is struck with a hammer it will vibrate for varying lengths of time depending upon the stress imposed and the composition and condition of the steel, but at a uniformly decreasing rate owing to the internal friction of the material which dissipates the energy as heat and sound.

Decarburization (Carbon & Alloy Steels)

The loss of carbon at the surface of steel as a result of heating in an atmosphere which converts the carbon of the steel to a gaseous form.

Deep Drawing (Copper)
A cold deformation process that uses a punch and die to produce hollow cylindrical components with a high length to diameter ratio (such as cartridge cases). It imparts significant cold work to the work piece.
Deep Drawing (Aluminium)
The forming of deeply recessed parts (such as beverage cans and hollow-ware) by means of plastic deformation of the material. As deep drawing does not uniformly cold work the blank there will be variations in the hardness and annealing response around the final part.
Deep Drawing Sheet (Aluminium)
Sheet produced with specific characteristics that permit deformation by deep drawing – such as softness, high ductility and low tensile strength.
Deformation (Stainless Steel)
The change in dimensions and/or shape of a material or work-piece due to applied forces. Deformation can be elastic or permanent. Elastic deformation happens when the work-piece returns to is previous dimensions or shape when an applied load below the yield point is removed. Loads above the yield point cause permanent deformation when the change in shape or dimension is not reversed when the load is removed.
Related Terms: Yield Point
Defence Standards
Delayed Ageing, Delayed Age Hardening (Aluminium)
Retarding natural ageing by holding the alloy below room temperature. If the alloy is raised to room temperature then natural ageing will proceed at the expected rate.
Related Terms: Ageing
Delta Ferrite (Metallurgical)

The allotropic form of iron which in the pure metal exists between 1405oC and the melting point, 1535oC. It is non-magnetic, and the atoms are arranged in the body centred cubic structure as in alpha iron. It is often present in high chromium stainless steels at room temperature as a separate phase.

Dendrite (Metallurgical)

A tree-like crystal formation. Metal crystals grow by branches developing in certain directions from the nuclei. Secondary branches are later thrown out at periodic intervals by the primary ones and in this way a skeleton crystal, or dendrite, is formed. The interstices between the branches are finally filled with solid which in a pure metal is indistinguishable from the skeleton. In many alloys, however, the final structure consists of skeletons of one composition in a matrix of another, giving what is called a cored structure. (See Coring).

Deoxidation (Metallurgical)

The final operation in the production of "killed" steel, when elements such as silicon or aluminium are added to stabilize the dissolved oxygen. This prevents it reacting with the carbon to form carbon monoxide which would form blowholes during subsequent solidification.

Deoxidised Copper (Copper)
Copper with a deoxidiser added to reduce Oxygen. Phosphorus is usually added but other elements such as boron or magnesium may be used. Welding and brazing properties are improved, but conductivity is somewhat impaired.
Descaling (Carbon & Alloy Steels)
  1. The removal of scale from the surface of steel by mechanical or chemical means, e.g., by sand- or shot-blasting, tumbling, flame descaling, or pickling.
  2. The removal of scale from the inner surface of boilers and tubes.
Descaling (Stainless Steel)
The removal of surface scale from hot worked or heat treated products by acid pickling or mechanical means such as grit or shot blasting. Caution is advised if stainless steels are mechanically descaled as blasting media can be embedded in the surface and act as corrosion initiation sites. It can also refer to the removal of scale formed during hot working processes by the application of water, coal dust, brushwood, oil, etc.
Dezincification (Copper)
The selective corrosion of the beta phase of Duplex Brass. The result is a Copper residue with a porous layer of Zinc Oxide.
Dezincification Resistant Brass, DZR (Copper)
Duplex Brass (CW602N, CZ132) that has an Arsenic addition and a special heat treatment to prevent dezincification by soft, acidic, domestic water supplies. Sometimes the term is applied to Arsenical, Aluminium or Admiralty Brasses that also have Arsenic additions. These alloys need no special heat treatment as no beta phase is present.
DGS (Copper)
Director General Ships. An obsolete prefix for British Naval material standards, in turn became NES (Naval Engineering Standards), in turn replaced by DSTAN or DEFSTAN (Defence Standards).
Diamond Pyramid Hardness Test (Metallurgical)

An indentation hardness test in which the indenter, a square diamond pyramid with an angle between opposite faces of 136o, is forced under a standard load into the surface of the specimen under test. The hardness is determined by measuring the diagonal of the indentation produced. The diamond pyramid hardness number is the number obtained by dividing the applied load in kilogrammes by the surface area of the impression in square millimetres computed from the measured diagonal of the impression. It is assumed that the impression is an imprint of the undeformed penetrator.

Die Casting (Carbon & Alloy Steels)
  1. The process of pouring metals into final shapes in metal moulds. If the metal is forced into the mould the process is known as pressure die casting, but otherwise it is known as gravity - or permanent mould-die casting. The process is usually applied to alloys having relatively low melting points, e.g., tin, zinc, lead and aluminium or magnesium base alloy. The advantages of this process are the high precision of the castings so produced and the high rates of production which may be achieved.
  2. The product of the die casting process.
Die Drawing (Aluminium)
A CAD Drawing of the extrusion die showing exact detail of the shape of the profile.
Die Lines (Aluminium)
Continuous longitudinal lines that are formed on extruded and drawn products by minor irregularities, or pick up, on the bearing surfaces of the die.
Die, Extrusion Die (Aluminium)
The hardened steel aperture through which a heated extrusion billet is pushed to form an extruded profile shape. There are 3 types of die: Flat Die – For extruding solid shapes Porthole Die – For extruding hollow shapes – This leaves one or two ‘weld’ seams along the length of the extrusion so tube produced in this way is called Welded Tube. Flat Die with Mandrel – For extruding seamless hollow shapes and seamless tube
Differential Annealing (Aluminium)
The localised heating of part of a blank so that only specific areas are annealed.
Diffusion (Metallurgical)

The process whereby the molecules in a solution move from regions of high concentration until complete homogeneity is attained. This process is rapid in gases, and moderate in liquids. The migration of atoms within a solid is brought about by thermal activation. Examples of this include nitriding, carbon case hardening and cementation which involve diffusion into the surface of a solid whilst decarburization involves diffusion from the surface.

Diffusion (in clad material) (Aluminium)
The migration of alloying elements from the core into the cladding layer during thermal treatment. This can be detrimental to the properties and behaviour of both the core and cladding.
Diffusion Staining (Aluminium)
Patchy surface discolouration that can occur as a result of diffusion in clad material.
DIN (Copper)
The prefix for German National Standards, also the German National Standards Organisation.
Direct Extrusion, Extrusion (Aluminium)
The extrusion process in which a preheated billet is placed in the container and is pushed by the ram through the stationary die to form the extruded section.
Related Terms: Container
Directional Properties (Aluminium)
Deformation by cold working causes changes to the grain structure and, sometimes, variations in mechanical properties across and along a work-piece. Properties measured along the direction of deformation are described as longitudinal, whilst those measured at a right angle to the direction of working are called transverse.
Dislocation (Metallurgical)

A discontinuity in the crystal lattice of a metal. The movement of such discontinuities under stress may be used to explain slip, creep, plastic yielding, etc.

Drawing (Copper)
A process carried out at room temperature where extrusion is pulled through a die to improve tolerances, surface finish and mechanical properties.
Drawing (Carbon & Alloy Steels)
  1. Drawing out metal rods into wire, in the cold state, by pulling through a series of consecutively smaller holes (dies) in steel plates (draw plates).
  2. Forging to produce the greatest movement in the longitudinal direction.
  3. In the solidification of castings, the production of shrinkage cavities by reason of improper design, insufficient feeding, too low a casting temperature.
  4. In the U.S.A. synonymous with tempering.
Drawing, Cold Drawing (Aluminium)
The pulling of a work-piece through a fixed die at room temperature. It can reduce the size, change the cross section or shape, improve surface finish, improve tolerances or work-harden the material.
Drawn Tube (Aluminium)
A hollow product of uniform wall thickness, produced by cold drawing.
Related Terms: Drawing, Cold Drawing
Drift Test, Flaring Test (Aluminium)
A test for the weld integrity of a welded tube, usually carried out to BS1139. All batches of Scaffolding Tube undergo this test.
Related Terms: Scaffolding Tube
Drop Forging (Carbon & Alloy Steels)
  1. A forging operation in which a metal shape is formed by repeated blows from a drop or steam hammer on to a bar or billet placed between a pair of dies. The upper die containing half the impression of the desired shape is fixed in the tup whilst the lower die, containing the other half of the impression, is in the stationary anvil. The force exerted by the hammer causes plastic flow in the metal which imparts a tough fibrous structure to the steel, the die being designed to ensure the most advantageous plastic flow of the material so that the grain follows the contour of the forging with as little interruption as possible. The process is economical only when a large number of reproductions are required, as the cutting of the dies is expensive. Where a change, not only of form but of the section of the material takes place, the product is a drop forging; if only a change of form occurs the product is a drop stamping.
  2. The metal shape made by the drop forging process. In such forgings the grain flow or fibre is of importance.
Dry Cyaniding (Carbon & Alloy Steels)

A process for case hardening steel by heating it to a temperature of between 625o and 850oC. in an atmosphere containing a carburizing gas with ammonia added in controlled amounts. The combined action of the carbon and nitrogen thus added to the steel permits a wide range of case and core characteristics by direct quenching or by cooling slowly in the atmosphere as required.

DTD (Copper)
Director of Technical Development. The prefix for material standards used by the British Army, RAF and other defence applications.
Ductility (Copper)
The ability of a metal or alloy to deform without cracking or failing under tensile loads. Materials with low ductility exhibit brittle behaviour and fail at more modest loads.
Related Terms: Malleability
Ductility (Stainless Steel)
The ability of a metal or alloy to deform without cracking or failing under tensile loads. Materials with low ductility exhibit brittle behaviour and fail at more modest loads. Ductility typically decreases at lower temperatures and most materials will become brittle below a certain temperature called the Ductile-Brittle Transition.
Ductility (Metallurgical)

The property of metals which permits deformation to occur without fracture. Ductile metals show considerable elongation under tensile stress and ultimately fail by necking, with consequent rapid increase in stress locally.

Duplex Ageing (Aluminium)
A two stage age-hardening heat treatment conducted at different temperatures.
Duplex Brass (Copper)
Brasses with composition ranging from 58% to 62% Copper with 38% to 42% Zinc that have both alpha and beta phases present in their microstructure. Duplex Brasses are superior to Alpha Brasses for hot working, but inferior for cold working.
Duplex Stainless Steels (Stainless Steel)
Duplex stainless steels have a two-phase microstructure consisting of grains of ferritic and austenitic stainless steel. The proportions are approximately 50% of each phase. Duplex stainless steels: •are stronger, by a factor of up to 2, than the austenitic and ferritic grades •are tougher and more ductile than the ferritic grades •have better stress corrosion resistance than the austenitic grades.
Related Terms: Austenite, Austenitic Stainless Steel, Ferritic Stainless Steels, Ferrite
Dye Penetrant Inspection (Metallurgical)

Used for detecting surface porosity or cracks, more particularly in non-magnetic substances. The part to be examined is cleaned and coated with a dye which penetrates any small cracks or openings. The surface is then wiped clean and coated with a white powder. The dry powder soaks up the dye which is still held in the defects and thereby indicates their position.

Dye Penetrant Test (Aluminium)
A non-destructive test for surface defects and flaws. A clean and degreased work-piece is dipped in, or otherwise coated by, a fluid containing a brightly coloured dye. This fluid is often called dye penetrant ink. After a predetermined time the ink is removed, usually by washing, and a, usually white, developer applied. The dye seeps out from any flaws and cracks, thereby making them easily visible.
Dynamic Strength (Metallurgical)

Resistance to loads suddenly applied or to pulsating loads.


Eccentricity (Stainless Steel)
This occurs in tubular products when the centres of the circles that describe the outside diameter and the bore do not coincide. It manifests itself as a variation in wall thickness around the tube.
Related Terms: Concentricity
Elastic Limit (Metallurgical)

The highest stress that can be applied to a metal without producing a measurable amount of plastic (i.e., permanent) deformation. Usually assumed to coincide with the limit of proportionality.

Elasticity (Metallurgical)

The tendency of a body to return to its original size and shape, after having been stretched, compressed or deformed. The ratio of the stress called into play in the body by the action of the deforming forces to the strain or change in dimensions or shape is called the coefficient or modulus of elasticity.

Electric Steel (Metallurgical)

Steel made by one of the electric processes where the heat required for melting the steel is provided either by an electric arc usually made to pass between the metal itself and a carbon electrode, i.e., the arc process, or by eddy currents induced by a high frequency current. In each process the furnace lining may be either acid or basic.

Electrical Conductivity (Metallurgical)

Rate at which electrons move through atoms causing current to flow.

Electrochemical Corrosion (Stainless Steel)
Corrosion, or metal dissolution, caused by the reaction M ? M+ + e- at the anode.
Electrochemical Protection (Stainless Steel)
The prevention of corrosion in an electrolyte by manipulation of the electrode potential of steel.
Electrode (Stainless Steel)
There are two electrodes in an electrochemical or corrosion cell, the anode and cathode. They are the electron conductors, through which electrons can enter and leave an electrolyte permitting reactions such as dissolution at the anode and deposition at the cathode to occur.
Electrode Potential (Stainless Steel)
The potential difference in a solution between the test electrode and a reference electrode, e.g. a saturated calomel electrode.
Electrode Reaction (Stainless Steel)
A chemical half or partial reaction that occurs at an electrode surface. It is called a half or partial reaction as only either the oxidation or the reduction part of the overall cell reaction occurs at any one electrode.
Electrolyte (Stainless Steel)
An electrically conducting medium, such as a salt solution or a molten salt through which an electric current is transported by ions.
Electrolytic Polishing (Stainless Steel)
An electrochemical method of imparting brilliance to the surface of a metal. The work-piece is made the anode and by careful selection of electrolyte and processing parameters a thin, uniform, surface layer is removed. It may be regarded as the opposite of electro plating.
Electron Microscope (Metallurgical)

An instrument for the examination of structures, the details of which are too fine to be resolved by the use of either visible or ultra-violet light. In it a stream of electrons and an electromagnetic field replace the light rays and optical lenses of the ordinary microscope.

Element (Aluminium)
A pure chemical substance that consists of just one type of atom as defined by its atomic number (the number of protons in its nucleus). Elements combine to make compounds, e.g. Copper Sulphate which contains Copper, Sulphur and Oxygen. An Alloy, e.g. Brass, is a solid solution of two or more elements.
Element (Copper)
A pure chemical substance that consists of just one type of atom as defined by its atomic number (the number of protons in its nucleus). Elements combine to make compounds, e.g. Copper Sulphate which contains Copper, Sulphur and Oxygen. An Alloy, e.g. Brass, is a solid solution of two or more elements.
Element (Stainless Steel)
A pure chemical substance that consists of just one type of atom as defined by its atomic number (the number of protons in its nucleus). Elements combine to make compounds, e.g. Copper Sulphate which contains Copper, Sulphur and Oxygen. An Alloy, e.g. Brass, is a solid solution of two or more elements.
Elongation (Metallurgical)

(a) The total extension produced in a tensile test are determined after fracture by holding the pieces of a fractured tensile test piece together and measuring between pop marks applied before starting the test. It is expressed as a percentage of the original gauge length, which should also be given, and in this country is usually 4 A, where A is the cross-sectional area of the test piece. It is a measure of the ductility of the steel.

(b) The extension produced, for example, in rolling.

EN (Copper)
Euro Norm, European Standard.
Endurance Limit (Metallurgical)

In fatigue testing, the value of the applied alternating stress which will produce fracture after a given number of reversals. (Cf. Fatigue Limit).

Energiser (Metallurgical)

A substance added to carburizing mixtures to accelerate the carbon case hardening process. The energisers most generally used are barium or sodium carbonates whose action is similar to a catalyst. It is believed that the energiser provides carbon dioxide, which in turn reacts with incandescent carbon to form an additional supply of carbon monoxide.

Engraving Brass (Copper)
CW612N / CZ120 Brass formulated to be best suited for engraving - For example of nameplates and pet’s collar identity discs.
Equilibrium Diagram (Metallurgical)

(Constitutional Diagram). A diagram constructed from thermal and other data showing the limits of temperature and composition within which the different constituents and phases of the alloy system in question are stable. From this, the changes of structure and the composition of the constituents in equilibrium at any specified temperature can be determined.

Erichsen Test (Metallurgical)

The standard cupping test, using a tool with a spherical end of 20mm. diameter to deform the test piece, which is held between annular jaws of 27mm. internal diameter. The test sheet, which is 3 1/2 in. square, is first clamped between the jaws to measure the thickness; the jaws are then moved apart by 0.05mm. and clamped in that position, to allow the metal to be drawn into the cup as the test progresses. The tool is pressed into the metal until a crack appears in the cup, and the depth of cup at this instant is taken as a measure of the ductility of the metal.

Etching (Aluminium)
The production of a uniform matt, surface finish on a work-piece by controlled chemical or electrochemical attack. The etching agent can be either acid or alkali in nature.
Etching (Metallurgical)

A process of revealing the structure of metal by selective chemical attack of the structure. This is rendered possible by the fact that the differently orientated crystals have different rates of solution in the etching reagents.

Etching Pits (Metallurgical)

Small cavities formed on the surface of metals during etching.

Etching Test (Aluminium)
The use of a chemical reagent to reveal the macrostructure of a sample from a work-piece. The test is usually made on a cross section from the work-piece so is destructive.
ETP (Copper)
Electrolytic Tough Pitch, high conductivity, Copper, CW004A (C101).
Eutectic (Metallurgical)

A mixture of definite composition, consisting of two or more constituents, which solidifies simultaneously out of the liquid at a minimum freezing point. This point occurs at the intersection of two descending liquidus curves in a binary system or three descending liquidus curves in a ternary system.

Eutectic Change (Metallurgical)

The transformation from the liquid to the solid state in a eutectic alloy. It involves the simultaneous crystallization of two constituents in a binary system and of three in a ternary system.

Eutectic Point (Metallurgical)

The point in the binary or ternary constitutional diagram indicating the composition of the eutectic alloy, or mixture of minerals, and the temperature at which it solidifies.

Eutectic Structure (Metallurgical)

The characteristic arrangement of the constituents in a eutectic resulting from their simultaneous crystallization from the melt.

Eutectoid (Metallurgical)

A mixture of two or more constituents which forms simultaneously on cooling from a solid solution and transforms again on heating, e.g., pearlite. The essential difference between a eutectic and a eutectoid is that the eutectic is formed from the melt whereas the eutectoid is formed from a solid.

Eutectoid Steel (Metallurgical)

Steel having the same composition as the eutectoid point in the iron-carbon system (0.83% carbon), and which, therefore, with suitable cooling conditions, consists entirely of pearlite at temperatures below 710oC.

Extensometer (Metallurgical)

An instrument for measuring minute extensions of the test piece during a tensile test. This is necessary when determining the Limit of Proportionality or Proof Stress.

Extrusion (Copper)
The process in which a preheated billet is constrained within a strong container in a press and then pushed by a ram through a shaped die. The product, also called an extrusion, has the shape of the die along its whole length. Angles, rectangles, rounds and hexagons are common shapes of extruded bar, whilst tubes are frequently hollow extrusions. With Copper Alloys, extrusion is very often followed by cold drawing to improve tolerances, surface finish and mechanical properties.
Extrusion (Stainless Steel)
The process in which a preheated billet is constrained within a strong container in a press and then pushed by a ram through a shaped die. The product, or extrusion, has the shape of the die along its whole length. Although some simple shapes are extruded in Stainless Steel, this process is most commonly used for Aluminium.
Extrusion (Carbon & Alloy Steels)

The term, as applied to metals and alloys, comprises essentially the application to a relatively massive billet or blank, of sufficient pressure to cause the metal to flow through a restricted orifice, thereby forming a greatly elongated section. In hot extrusion, the metal is above its recrystallization temperature and thus continuously recrystallizes and is not work hardened during the process. In cold extrusion, the metal does not reach the temperature of recrystallization and may, therefore, be considerably work hardened by the process. In the production of seamless tubes from a hot billet, the latter is forced to flow through a die over a mandrel positioned centrally in the die.

Extrusion Ratio (Aluminium)
The ratio of the cross-sectional area of the extrusion container to that of the extruded product.


Face Centred Cubic Lattice (Metallurgical)

An arrangement of atoms in crystals in which the atomic centres are disposed in space in such a way that they may be supposed to be situated at the corners and the middle of the faces of a set of cubic cells, i.e., the lattice possesses half an atom in the middle of each face of the cubic lattice, the corners each sharing one atom with seven other cubes. Thus, each unit cell contains four atoms.

Fatigue (Metallurgical)

The effect on a metal of repeated cycles of stress. Fracture results from the development of a crack which progresses across the section, with repeated stress. (See also Fatigue Limit and Corrosion Fatigue.)

Fatigue (Stainless Steel)
The localised, progressive and permanent damage or structural change that occurs to a material subjected to repeated, fluctuating, loads that are lower, often much lower, than the static yield strength of the material. Good design is the key to minimising or mitigating fatigue problems.
Fatigue Limit (Metallurgical)

The maximum value of the applied alternating stress which a test piece can withstand indefinitely. (Cf. Endurance Limit).

Fatigue Range (Metallurgical)

The maximum range of stress which a metal will withstand indefinitely. When the maximum stress in tension equals that in compression, the fatigue range is twice the fatigue limit. The mean stress, i.e., half the range, must be stated to define the fatigue conditions.

Fatigue Resistance (Metallurgical)

The ability of a metal to withstand repeated and varying loads.

Feedstock (Copper)
A semi-finished material that is used to 'feed' the next process. For example continuously cast billet is the feedstock for extrusion and continuously cast rod or bar may be the feedstock for wire making.
Ferrite (Stainless Steel)
A body centred cubic (BCC) phase found in most carbon and low alloy steels. It is magnetic and is why most steels themselves are magnetic. It transforms above 760°C into the non-magnetic, face centred cubic (FCC) phase austenite.
Ferrite (Metallurgical)

A term once restricted to pure alpha iron but now extended to include any solid solutions of which alpha or delta iron, as distinct from gamma iron, is the solvent. Alpha ferrite forms from the gamma, austenitic phase, in slowly cooled hypo-eutectoid steels, and unless hardened by cold work it is soft and ductile. It may contain, in solid solution, many of the special elements, e.g., up to 30% chromium, or 15% silicon, but very little carbon, i.e., less than 0.03%. Pure iron consists of 100% ferrite and ferrite is the principal constituent in low carbon steels. When etched with nital, the grain boundaries appear as dark lines surrounding the white ferrite.

Ferritic Stainless Steels (Stainless Steel)
Ferritic stainless steels are iron chromium alloys that contain a minimum of around 10.5% Chromium. They have a body centred cubic (BCC) ferrite microstructure. They contain little or no Nickel and hence are less expensive than austenitic stainless steels. They generally have somewhat better mechanical properties than the austenitic grades but have inferior corrosion resistance except, importantly, they do have superior stress corrosion cracking resistance.
Ferro Alloys (Metallurgical)

A term used for alloys of iron with another metal such as chromium, manganese, silicon, tungsten, molybdenum or vanadium. These alloys are used as a means of introducing the alloying element into steel or cast iron, or as deoxidisers. Ferro alloys are produced by electric smelting or by reduction with aluminium, an exception being high carbon ferro manganese which is normally produced in blast furnaces.

Ferro Manganese (Metallurgical)

The form in which manganese is generally used in the steel industry. The ordinary qualities contain 70 to 80% manganese and about 7% carbon. Spiegeleisen may contain from 12 to 30% manganese and about 5% carbon. These alloys are produced in small blast furnaces of standard type except that they are often fitted with special cooling devices, owing to the high temperatures involved in the reduction of manganese oxides. Low carbon ferro manganese is an electric furnace product and is available in several grades, of which the highest quality may contain as much as 90% manganese with a maximum carbon content of 0.07%.

Finstock (Aluminium)
Narrow strip in the thickness range 0.2mm to 0.4mm used for finning of heat exchanger tubes in applications such as air conditioning.
Firecracks (Metallurgical)

(a) Cracks found, for example, on the surface of rolls of hot rolling mills, or metallic bodies which have been subjected to repeated heating and cooling.

(b) (Chill Cracks). Marks on the surface of a hot rolled product which appear periodically, having been produced by a crack or cracks on the surface of the roll.

Fixed Mandrel (Aluminium)
A device for producing hollow extrusions of regular cross section. The tapered mandrel is attached to the main extrusion ram and passes through the hollow billet. As the ram moves forward the mandrel passes, with the billet, through the die giving a product slightly tapering in wall thickness along its length. The mandrel is tapered to facilitate its removal when extrusion is complete.
Flakes (Metallurgical)

(Hair Line Cracks, Snow Flakes). Fine internal fissures which may be found lying in various directions in the interior of steel. They occur most frequently in large alloy steel sections but may also be found in carbon steels. Flakes in the heads of rails are known as Shatter Cracks. They are caused by hydrogen in the steel and may be prevented by appropriate heat treatment or by casting in a vacuum.

Flash Annealing (Aluminium)
Annealing of a work-piece by rapid heating and a short dwell time at the appropriate temperature.
Flatness (Aluminium)
The property of having a horizontal surface without any slope, tilt, or curvature, i.e. that of a flat plane. In practice a perfectly flat surface is probably unobtainable so there will be a flatness tolerance.
Related Terms: Flatness Tolerance
Flatness Tolerance (Aluminium)
A three-dimensional geometric tolerance that controls how much a product surface can deviate from a flat plane. The permitted deviation will depend upon the thickness of the sheet or plate varying between 0.2% and 0.5% of its width and length, usually measured over a 1 metre length.
Floating Mandrel (Aluminium)
A tapered mandrel that is inserted into the hollow extrusion billet. It is not attached to the extrusion ram so is left free to centre itself in a hollow billet as it moves forward through the die as the ram advances and extrusion proceeds. The resulting product tapers slightly in wall thickness along the length.
Related Terms: Fixed Mandrel
Flotation (Copper)
A mineral beneficiation technique used to concentrate ore by blowing air through a tank in which ore particles are suspended in water that contains additions that make the ore more hydrophilic. The ore clings to the bubbles and is scraped off as 'froth'.
Flow Lines (Fibre) (Metallurgical)

(a) The fibrous appearance of hot-worked steel caused by local differences in composition and the presence of inclusions which are drawn out in the direction of working. Flow lines are important in many stamped parts since the fibre habit results in directional properties.

(b) Striations visible on etching cold-worked steels. They are caused by local electrolytic differences of potential produced by the varying degrees of local distortion, and indicate the principal directions in which movement of the metal has taken place.

Foil, Tin Foil, Kitchen Foil, Cooking Foil (Aluminium)
Cold rolled aluminium flat product less than 250 microns in thickness. Usage includes kitchen foil (cooking foil) and foil trays for food. Kitchen Foil is often incorrectly referred to as Tin Foil.
Forging (Aluminium)
Hot working using a forge with shaped tools that ‘hammers’ the work-piece into a predetermined shape.
Forging (Carbon & Alloy Steels)
  1. Working metal parts to a finished shape by means of hammering or pressing after the material has been rendered plastic by heating to a high temperature. Forging may be carried out by hammer forging, press forging and drop forging or stamping. Hammer forging is carried out by steam or pneumatic hammers and deformation is brought about by a number of sharp successive blows of short duration, i.e., by shock. Press forging is done by hydraulic presses and the deforming pressure is applied for longer periods.
  2. The product of the forging operation. (See also Drop Forging).
Related Terms: Drop Forging
Fracture Test, Impact Test, Charpy Test, Izod Test (Aluminium)
A test in which the test piece is notched and broken. The fracture surface examined to assess grain structure and freedom from defects. Also used to determine toughness, often at varying temperatures to establish at what reduced temperature the material becomes brittle.
Free Cutting Steels (Carbon & Alloy Steels)

Steels to which special additions have been made to promote machinability. Sulphur, lead or selenium are elements usually added for this purpose.

Free Machining Alloy (FMA) (Aluminium)
An alloy designed to give, when machined, small broken chips, lower power consumption, better surface finish and/or longer tool life. Chemical composition and microstructure both influence this property.
Free Machining Stainless Steels (Stainless Steel)
Many standard compositions of stainless also have a “free machining” variant with enhanced machinability. This is achieved by adding small amounts of certain alloying elements to the steel during melting. These added elements produce inclusions in the microstructure that act as chip breakers and can also lubricate the cutting action, increasing cutting speeds by approximately 75% on stainless steel. Sulphur is particularly good for heavy machining because of the large and fairly continuous inclusions. Selenium additions have also been used, especially in the USA, but are not available from European suppliers. Unfortunately addition of these elements has a negative effect on other properties, notably Corrosion Resistance in the case of added Sulphur. For this reason the more recently developed IMA grades are preferred.
Related Terms: IMA - Improved Machinability Alloy
Free Machining, Free Cutting, High Speed Machining (Copper)
Terms that are used interchangeably to describe materials that can be turned, drilled or otherwise machined using high cutting speeds and feeds to leave a good surface finish with low tool wear and no appreciable build-up of swarf around the cutting tool. The addition of Lead to Copper alloys usually improves machinability. The brass CW614N (CZ121 Pb3) has one of the fastest rates of metal removal, but ductility is compromised. This brass sets the machinability standard against which the machinability of all other alloys are measured.
Full Annealing (Carbon & Alloy Steels)

A softening process in which the steel is heated to and held for a suitable length of time at a temperature, which for hypo-eutectoid steel is above the transformation range, and for hyper-eutectoid steel within the transformation range, followed by slow cooling to 600oC or below.

Full Heat Treatment (Aluminium)
For alloys in the 2xxx, 6xxx, 7xxx and 8xxx series this is the heat treatment cycle consisting of solution treatment followed by artificial age hardening.


Gauge Length (Aluminium)
In a tensile test this is the prescribed part of the cylindrical or prismatic portion of the test piece on which elongation is measured at any moment during the test. In particular, a distinction should be made between the following: ~ The original gauge length, i.e. the gauge length before the test is started. ~ The final gauge length – The gauge length after the test is completed and the test piece has fractured. The broken pieces are carefully fitted together to lie in a straight line so that it can be measured.
General Corrosion (Stainless Steel)
Corrosion in which the whole exposed surface is attacked by the corrosive medium at a broadly uniform rate. All corrosion is deleterious but general corrosion is more predictable and may be readily monitored and so managed. This is in contrast to the localised forms of attack such as pitting corrosion, crevice corrosion, inter-granular corrosion and stress corrosion cracking where the attack in very localised and can be intense causing unexpected, premature, failure.
Related Terms: Inter-granular Corrosion, Pitting Corrosion, Crevice Corrosion, Stress Corrosion Cracking
Gilding Metals (Copper)
Alpha Brasses with 80% to 90% Copper content and no other alloying constituents apart from Zinc. They have good ductility and are easily brazed or enamelled. They are used for decorative purposes such as jewellery and architectural hardware.
Grain Flow (Aluminium)
Elongation of the grain structure in the direction of cold working.
Grain Growth (Aluminium)
Coarsening of the grain structure that occurs under certain conditions of heating. It is generally undesirable and is deleterious.
Grain Size (Aluminium)
A measure of the area or volume of grains in polycrystalline material. Grain size is reported in a number of ways 1. number of grains per unit of area or volume, 2. average diameter, 3. as a grain size number derived from area measurements and comparison with a standard chart.
Grain Size (Stainless Steel)
A measure of the area or volume of grains (crystals) in polycrystalline material. Grain size is reported in a number of ways:- • Number of grains per unit of area or volume, • Average diameter, • As a grain size number derived from area measurements and comparison with a standard chart.
Grain Size Control (Metallurgical)

A special deoxidation technique producing steel having an austenitic grain size within a specified range in accordance with the McQuaid Ehn grain size scale. It is achieved by the addition of aluminium to the liquid steel.

Grain Structure (Stainless Steel)
The shape, size, distribution and disposition of metal crystals and their crystal structure within a solid metal or alloy.
Guillotining (Stainless Steel)
The cutting of plate, sheet or strip to size or length using guillotine shears. For the guillotining of stainless steels, as compared to mild/carbon steels, the shearing blades need to be sharper and have a reduced clearance.
Gunmetal (Copper)
A Casting Bronze alloy of Copper with Tin (10%) and Zinc (2%). Historically it was used to cast cannons so it is sometimes called Admiralty Gun Metal. It has excellent corrosion resistance in seawater and steam. Leaded Gunmetal containing slightly less Tin, more Zinc and up to 7% Lead is a very useful plain bearing metal.


Half Hard (Copper)
Material in the Half Hard Condition, sometimes refetrred to as H02 is at an intermediate strength and hardness netween Soft and Full Hard
Hall Heroult Process, Smelting (Aluminium)
The main process used for the production of Aluminium metal whereby Alumina is dissolved in a salt bath of molten cryolite and subject to an electrolysis process. Often referred to as Smelting, this process uses very large amounts of electricity. Named after two scientists who developed the process independently of each other at around the same time.
Hall-Heroult Process (Aluminium)
The main process used for the production of Aluminium metal whereby Alumina is dissolved in a salt bath of molten cryolite and subject to an electrolysis process. Often referred to as Smelting, this process uses very large amounts of electricity. Named after two scientists who developed the process independently of each other at around the same time – Hall, English and Heroult, French.
Related Terms: Smelting
Hard Facing (Carbon & Alloy Steels)

A method of improving wear resistance by suitable application of a hard protective coating to a metal. Examples are the deposition by welding of Stellite or metal carbide.

Hard Metals (Carbon & Alloy Steels)

(Cemented Carbides). Powdered carbides of tungsten, tantalum or titanium, cemented into solid masses by mixing with powdered cobalt or nickel, then compressing and sintering. Used for cutting tools, wire-drawing dies and parts subjected to heavy wear or abrasion.

Hardenability (Metallurgical)

The property that determines the depth and distribution of hardness induced by quenching, i.e., it represents the resistance to transformation. It is generally expressed in relative terms and is related to the critical cooling rate, i.e., the rate at, or above which wholly martensitic structures are formed. This critical cooling rate, or hardenability, is largely a function of composition, although steels of apparently similar composition can have different hardenabilities and the same cast of steel may show fairly wide variations. There is a limit to the section size which can be completely hardened upon quenching. Plain carbon steels are shallow hardening, and alloy additions increase the depth of hardening. The Jominy Test is a method of assessing hardenability.

Hardening (Carbon & Alloy Steels)

Increasing the hardness by heat treatment. This usually implies heating to a temperature slightly above the critical range, i.e., for hypo-eutectoid steels above the AC point and for hyper-eutectoid steels above the AC point, maintaining at that temperature until diffusion is complete, and by quenching in water, oil or air cooling at a rate sufficiently rapid to prevent or retard the austenite-pearlite transformation, and to form a martensitic or bainitic structure.

Hardness (Metallurgical)

Signifies, in general, resistance to deformation. It is usually measured by determining the resistance to indentation, as in the Brinell, Diamond Indenter, Rockwell and Shore tests. The values of hardness obtained by the different methods are to some extent related to each other, and to the ultimate tensile stress of non-brittle metals. In Moh's scale comparative hardness is determined by testing against ten standard minerals: (1) talc, (2) gypsum, (3) calcite, (4) fluorite, (5) apatite, (6) orthoclase, (7) quartz, (8) topaz, (9) corundum, (10) diamond. Thus, a mineral with "hardness 5" will scratch or abrade fluorite, but will be scratched by orthoclase.

Hardness Test (Aluminium)
A test conducted to measure Hardness. A load is applied to an indenter to press it into the surface of the test piece. The indenter can be either a ball of various standard diameters or a diamond of one of several specified geometric profiles. The result of the test is reported as a Hardness Number which is derived from either a measurement of the depth to which the indenter penetrates or from the surface area of the impression left by the indenter.
Related Terms: Hardness
Hardness, Vickers Hardness, Brinell Hardness, Rockwell Hardness (Aluminium)
The resistance of a metal to plastic deformation usually by indentation using a diamond or a hardened steel ball. There are various recongnised hardness scales including Vickers (VPN), Brinell and Rockwell. N.B. The empirical, but robust, relationship between hardness and tensile properties that applies in steels does not apply, and the steel tables must not be used for aluminium and its alloys. A less rigorous relationship has been established for some aluminium alloys but it is not widely used.
Hardometer (Metallurgical)

The principle embodied in this instrument is similar to that of the Brinell machine in which a hard steel ball is pressed, by means of a known load, into the specimen to be tested, the hardness being determined by measurement of the impression. Owing to the limitations of the hardened steel ball, for testing harder materials a pyramid diamond indenter is used. The hardness numbers are obtained by dividing the load in kilograms by the area of the impression in square millimetres; this applies both to the steel ball and to the diamond indenter. In the latter case, the hardness numbers obtained should be referred to as the diamond hardness numbers. The scale of ball impression diameters and Brinell hardness numbers corresponds exactly to that used with the 10mm. ball Brinell machine, provided both machines are used with the same ratio of load to square of ball diameter.

Hatfield Time Yield (Metallurgical)

A short time creep test criterion. The specimen placed under the time-yield stress should not show an extension exceeding 0.50% of the gauge length in the first 24 hours, and during the next 48 hours should show no further extension, within a sensitivity of measurement of 1/10,000th inch on a 2 inch gauge length, which is approximately equivalent to a rate of creep of a millionth of an inch per inch per hour during this period.

HDHC (Copper)
Hard-Drawn High-Conductivity Copper CW004A/C101
Heat Exchanger (Stainless Steel)
A device that facilitates the efficient transfer of heat energy from one fluid to another. The fluids are often kept apart by solid barriers, either the walls of tubes, or the formed sheets of clam shell type heat exchangers. Typically a heat exchanger will have many tubes or clam shells assembled in either bundles or stacks connected by manifolds. One fluid flows outside the assembly whilst the other flows inside.
Heat Treatable Alloy (Aluminium)
Any of the 2xxx, 6xxx, 7xxx and 8xxx series of wrought aluminium alloys whose mechanical properties can be increased by a solution treatment and age hardening heat treatment cycle.
Heat Treatable Alloy (Copper)
The description applied specifically to a Copper Alloy whose mechanical properties can be increased by heat treatment, typically solution treatment and age hardening e.g. for Beryllium Copper.
Related Terms: Beryllium Copper, Heat Treatment of Copper and its Alloys
Heat Treatment (Aluminium)
The thermal processing of a work-piece specifically to alter its mechanical properties. It includes:- 1. Annealing to soften and improve ductility. 2. Solution treatment and precipitation hardening to increase strength. It does not include heating before hot rolling, forging or extrusion etc.
Heat Treatment (Carbon & Alloy Steels)

A process in which steel in the solid state is taken through one or more temperature cycles for the purpose of obtaining certain desired properties. Heating for the sole purpose of hot-working is excluded from the meaning of this definition.

Heat Treatment of Copper and its Alloys (Copper)
A range of heat treatment processes are applied to copper and it alloys including • Homogenising • Annealing • Stress Relieving • Solution Treatment and Ageing • Quench and Temper Hardening It is important to recognise that not all processes are appropriate for all alloys. Homogenising in which prolonged soaking at elevated temperature is used to reduce solidification chemical segregation in castings particularly in Phosphor Bronzes, Copper Nickels and Silicon Bronzes that have long freezing ranges. Annealing is used to soften and increase ductility and toughness in wrought alloys. Stress relieving is used to relieve internal stresses without significantly affecting mechanical properties. Solution Treatment and Ageing is used on Beryllium Copper, Copper/ Chromium, Copper /Zirconium and Copper/Nickel/Silicon/Chromium alloys to increase mechanical properties. Quench and Temper Hardening is applied to certain Aluminium Bronzes, Nickel Aluminium Bronzes and some cast Manganese Bronzes to increase their mechanical properties.
Heyn's Reagent (Metallurgical)

An etching reagent containing 10% copper ammonium chloride in water.

High Speed Steel (Metallurgical)

A high alloy steel, capable of intense hardening, used for metal-cutting tools. It retains its hardness at a low red heat, and hence the tools can be used in lathes, etc., operated at high speeds. It usually contains 12-22% tungsten, up to 5% chromium, up to 1% carbon, and varying amounts of other elements (vanadium, cobalt, etc.) Part or all of the tungsten may be replaced by half its weight of molybdenum.

High Speed Steel (Carbon & Alloy Steels)

A high alloy steel, capable of intense hardening, used for metal-cutting tools. It retains its hardness at a low red heat, and hence the tools can be used in lathes, etc., operated at high speeds. It usually contains 12-22% tungsten, up to 5% chromium, up to 1% carbon, and varying amounts of other elements (vanadium, cobalt, etc.). Part or all of the tungsten may be replaced by half its weight of molybdenum.

High Tensile Brasses (Copper)
An important group of brasses whose strength has been increased by modifications to their chemical composition by additions of Iron, Nickel, Manganese and/or Aluminium. Aluminium or Tin additions also improve corrosion resistance, Silicon additions are beneficial to wear properties.
Hollow Forging (Carbon & Alloy Steels)

A method of producing hollow bodies, e.g., steel tubes or pressure vessels, in which a comparatively small hole, trepanned in a solid forging, is expanded on a mandrel under a forging press or on a becking bar.

Hollow, Tube Hollow (Stainless Steel)
Interchangeable terms for a hot finished semi-finished product from either an extrusion or piercing process. They are the feedstock for cold drawing or cold reduced tube production.
Homogenistation (Aluminium)
The structure of as cast semi finished products e.g. slab, extrusion billet or forging blanks is invariably chemically segregated - that is the alloying elements are concentrated locally rather than uniformly distributed within the microstructure. Homogenising is a way of mitigating this as the work-piece is held at a suitably high temperature for sufficient time to eliminate, or at least decrease, chemical segregation by diffusion of the alloying elements.
Homogenizing (Metallurgical)

A process of heat treatment at high temperature intended, by means of diffusion, to eliminate or decrease segregation.

Hooke's Law (Metallurgical)

This law states that "within the limits of elasticity the strain produced by a stress of any one kind is proportional to the stress producing it". The value of the stress at which a material ceases to obey Hooke's Law is known as the limit of proportionality.

Hot Shortness (Metallurgical)

Brittleness in metal at certain ranges above normal room temperature. It is manifested by loss in ductility and a liability to crack under stress at that particular temperature.

Hot Work (Carbon & Alloy Steels)

The mechanical working, by rolling, forging or extruding, of a metal or alloy at a temperature above its recrystallization point. This temperature varies according to the composition of the material.

Hot Working (Aluminium)
Plastic deformation, e.g. hot rolling, extrusion or forging, of a work piece in a temperature range and at a rate such that strain hardening does not occur.
Huey Test (Stainless Steel)
A corrosion test for evaluating the inter-granular corrosion resistance of stainless steels by boiling in refluxed 65% nitric acid for five consecutive 48-hour periods, each period starting with fresh acid.
Hysteresis Curve (Metallurgical)

A curve showing the relation between the magnetizing force and flux density in a sample of iron or steel, the curve being taken with ascending and descending values of magnetizing force, in order to illustrate the magnetic hysteresis loop.


IACS (Copper)
International Annealed Copper Standard - a measure of electrical conductivity agreed in 1913 with “pure” Copper set as 100%. Advances in copper refining mean that now the pure Copper can attain 103% IACS. The minimum requirement for High Conductivity Copper now is 101% IACS.
IMA - Improved Machinability Alloy (Stainless Steel)
Enhanced machinability grades that achieve the improved machinability without the addition of elements like Sulphur that have a negative effect of other properties.
Related Terms: Free Machining Stainless Steels
Immunity (Stainless Steel)
In corrosion terms a thermodynamically stable condition. In other words there is no corrosion attack.
Impact Test (Metallurgical)

A test to determine the resistance of a material to a suddenly applied stress, i.e., shock. A notched test piece is normally employed and the testing machines in general use are the Izod and Charpy. The resistance is usually reported as the energy in ft.-lb. or kg. m. required to fracture or bend the test piece, or as kg. m. per square centimetre of section behind the notch.

Inclusion (Stainless Steel)
Non-metallic particles within the microstructure. Some, sulphides and selenides, are deliberately formed in the metal during its manufacture, others are an inevitable result of melting and casting. Good practice dictates that the second type be kept to minimal levels as they are deleterious.
Related Terms: Free Machining Stainless Steels
Indirect Extrusion, Backwards Extrusion (Aluminium)
The extrusion method in which there is no relative movement between the billet and the container. This is accomplished by:- Either pushing the die held on the end of a long, hollow, stem through the billet. Or moving the billet and container together over the die, again held on the end of a long, hollow, stem. As there is no movement between the billet and container the friction, and hence extrusion loads, are reduced by up to 30% compared to direct extrusion and grain structures can be improved. The process is limited by the size, length and strength of the stem which holds the die.
Ingot (Aluminium)
A cast product that may be various shapes including slab, billet, bloom or more complex shapes. Produced by pouring liquid aluminium into a shaped mould and allowing it to cool.
Integral Colour Anodising (Aluminium)
Coloured surfaces developed either by anodising certain Aluminium alloys and/or by using special organic electrolytes that produce colours during anodising.
Inter-granular Corrosion (Stainless Steel)
Preferential, concentrated, corrosion attack at the grain boundaries. It is highly deleterious and usually caused by the precipitation of carbide particles in the grain boundaries after welding or incorrect thermal processing.
Related Terms: Sensitisation, Sensitised, Weld Decay
Intercrystalline Corrosion (Metallurgical)

(Intergranular Corrosion). (Weld Decay). A defect occurring in chromium-nickel austenitic steels when submitted to chemical attack after heating within the range 500o -800oC. At this temperature the carbon is precipitated at the grain boundaries as chromium carbide, thus impoverishing the chromium content of the austenite adjacent to the boundaries and rendering them susceptible to corrosion. In welding, the material near the weld is heated in this range of temperature. For such zones, or in steel otherwise heated in this range, corrosion may produce complete disintegration of the steel at the crystal boundaries. The defect may be prevented by adding to the steel a carbide-forming element such as titanium or niobium which acts as a stabilizer. It is added in an amount sufficient to form a stable carbide and thus prevent the carbon from combining with the chromium. The alternative to adding the carbide-forming element is to maintain the carbon content of the steel at a very low level, e.g., <0.03%.

Intercrystalline Corrosion Tests (Metallurgical)

Of various methods for determining susceptibility of stainless steels to intercrystalline corrosion, the two most commonly used are the sulphuric acid-copper sulphate test (Hatfield or Strauss test), and the boiling 65% nitric acid test (Huey test).

Internal Stress (Aluminium)
Stresses within a work-piece caused by previous treatments, e.g. casting, thermal treatment or fabrication.
Inverse Segregation (Metallurgical)

(Negative Segregation). A concentration of certain alloy constituents that have lower melting points in the region corresponding to that first solidifying; caused by interdendritic flow of enriched liquid through channels where the pressure drops with contraction of dendrites. The internal evolution of hydrogen may also give a positive pressure, aiding this flow and causing a liquated surface.

ISO (Copper)
The International Standards Organisation responsible for the ISO range of standards.
Isothermal Quenching (Aluminium)
A procedure in which the work piece is quenched, and held for some time, in a fluid which is held at a constant temperature between the solution treatment temperature and room temperature. This permits precipitation hardening.
Izod Impact Test (Metallurgical)

A test piece of 10mm. square in section is notched transversely by a V-cutter, to a depth of 2mm. and an angle of 45o. The radius at the bottom of the notch is 1/4mm. The piece is fixed vertically in the vice of the machine by the lower end with the notch at the level of the face of the vice. When the pendulum of the machine is released it swings freely, and a knife edge carried in the tup of the machine strikes the piece at a distance of 22mm. above the notch, on the same side as the notch. The angle of swing of the pendulum beyond the vertical after breaking the test piece is indicated by a pointer which should have been previously set to zero. From the amount by which the angle falls short of the angle to which the pendulum would have swung if there had been no test piece, the amount of energy absorbed in breaking the test piece is known, and is indicated by the pointer in ft.-lb. The height of fall of the centre of mass of the pendulum is 2 1/2 ft., and the capacity of the machine 150 ft.-lb., or 120 ft.-lb., the distance from the pivot to the striking edge being 4 feet. The striking velocity, when using the full capacity of the machine, is 13.6 ft. second.


Jominy Test (Metallurgical)

A hardenability test in which a standard test piece, 1 inch diameter x 4 inches long, is heated to a predetermined temperature, rapidly transferred to a jig fixture and quenched, under standard conditions, by a jet of water impinging on one end. When the specimen is sufficiently cool, hardness determinations are made along the specimen from the quenched end; the diagram relating hardness to distance from the quenched end of the specimen is known as a hardenability curve.


Killed Steel (Metallurgical)

Steel that has been completely deoxidized by the addition of manganese, silicon, and sometimes aluminium, before casting, so that there is practically no evolution of gas during solidification, and sound ingots are obtained. The shrinkage cavity or pipe is limited to the upper portion of the ingot or in the feeder-head with which such ingots are usually provided.


Latent Heat (Metallurgical)

Thermal energy expended in changing the state of a body without raising its temperature, e.g., ice to water at 0oC, or water to steam at 100oC, or alpha to gamma iron at the A point.

Lateral Curvature, Edge Curvature (Aluminium)
The lateral departure, in arc form, of an edge from linear straightness.
Ledburite (Metallurgical)

The eutectic of the iron/iron carbide system. It freezes at about 1130o C. and is composed of austenite and cementite containing about 4.3% carbon. During cooling, the austenite may transform to ferrite and cementite. It is typically found in cast iron.

Limit of Proportionality (Metallurgical)

The stress (load divided by original area of cross-section of the test piece) at which the strain (elongation per unit of gauge length) ceases to be proportional to the corresponding stress. In practice it is determined by inspection of a load-elongation diagram, obtained by plotting extensometer readings, and is the stress at which the load-elongation line ceases to be straight.

Limiting Creep Stress (Metallurgical)

A term used somewhat loosely to denote the maximum stress at which a material will not creep by more than a certain amount within the working life of the part. It is also used in some of the short-time creep tests, as, for example, the Hatfield Time Yield.

Limiting Range of Stress (Metallurgical)

The greatest range of stress that a metal can withstand for an indefinite number of cycles without failure. If exceeded, the metal fractures after a certain number of cycles which decrease as the range of stress increases. When the mean stress is zero, half this range is the fatigue limit.

Liquidus (Metallurgical)

A line in a binary phase diagram or a surface on a ternary phase diagram, representing the temperatures under equilibrium conditions at which freezing begins during cooling, or melting is completed on heating, i.e., the line or surface above which all the alloys in the system are completely molten.

Load Extension Curve (Metallurgical)

A line plotted from the results of a tensile test, with loads as ordinates and elongations of the gauge length as abscissae, thus relating the extension of the material under test to the applied load. (See also Stress-Strain Curve).

Localised Corrosion (Stainless Steel)
A general term for, often high rate, corrosion attack affecting restricted, specific, parts of the surface.
Related Terms: Pitting Corrosion, Crevice Corrosion, Stress Corrosion Cracking
Lüders Lines (Aluminium)
Surface marks caused by localised flow that appears on some alloys after light straining. They run parallel to the direction of maximum shear stress i.e. at 45° to the direction of the deforming stress.


Machinability (Copper)
An important, but difficult to quantify, property of a material. It relates to the ease by which material can be removed from a work-piece by a cutting tool, in turning, drilling, shaping or milling, etc., to leave a satisfactory surface finish. Materials with good machinability permit fast cutting speeds, high feeds with low tool wear and produce a bright, smooth surface. Free Machining Brass CW614N (CZ121 Pb3) has one of the fastest rates of metal removal and sets the machinability standard against which the machinability of all other alloys are measured.
Macrograph (Metallurgical)

A low power reproduction, usually by photography, of the coarse structure of, for example, a metal as shown by a polished and, as a rule, etched section or surface.

Macrostructure (Metallurgical)

The general crystalline structure of a metal or alloy and the distribution of impurities as seen on polished and etched surfaces, either by the naked eye or under magnifications of less than 10 diameters.

Magnetic Change Point (Metallurgical)

The temperature at which iron becomes non-magnetic on heating (Ac ) and conversely that at which it becomes magnetic on cooling Ar). This temperature, also known as the Curie or magnetic transformation point, in pure iron is 770oC.

Magnetic Crack Detection (Metallurgical)

The part to be examined is magnetized either by passing a heavy current through it or by making it the core of a coil through which a heavy current is passed. Small cracks, or non-magnetic phases such as inclusions, cause the magnetic flux to break the surface thus forming small magnets. When the part is sprayed with a suspension of iron oxide particles in paraffin, the particles cling to the small magnets and thus show the presence of defects.

Magnetic Etching (Metallurgical)

A method in which a polished surface is covered with a thin colloidal suspension of magnetic particles and a magnetic field applied. A visible concentration of the colloid results wherever there are free poles, e.g. at cracks and non-metallic inclusions.

Magnetic Flux (Metallurgical)

A term used to denote the amount of magnetism induced in a piece of magnetic material when it is placed in a magnetizing field.

Magnetic Flux Density (B) (Metallurgical)

(Magnetic Induction). The normal magnetic flux induced by a magnetizing force H, measured in lines or gauss per sq. cm.

Magnetic Hysteresis Loop (Metallurgical)

A closed figure formed by plotting the magnetizing force (H) against the magnetic flux density (B) when the former is taken through a complete cycle after initial magnetization, the magnetic hysteresis loss being proportional to the area of this loop.

Magnetostriction (Metallurgical)

The change in dimensions of magnetic materials brought about by magnetization or conversely the changes in magnetic properties brought about by strain.

Malleability (Copper)
The ability of a metal to deform into a useful shape, without breaking or cracking, under a compressive load. It is therefore the analogue of ductility which measures these effects in tension. A ductile material is invariably malleable and, hence, ductility and malleability are, incorrectly, often used interchangeably. Malleability is improved by annealing.
Malleability (Metallurgical)

The property which enables a metal to be mechanically deformed under compression, as in hammering or rolling into thin sheets without cracking. (See Ductility).

Manganese Bronze (Copper)
A frequently, but incorrectly, used term to describe the duplex, high tensile, Brasses (e.g. CW721R / CZ114) that contain Manganese.
Manipulation Tests (Stainless Steel)
Tests performed on full section or sector specimens to evaluate the ability of the work-piece to withstand possibly severe manipulation. Crush, flare, bend, flare and flange, flatten, reverse flatten, reverse bend and Van Stone flange tests may be used.
Martempering (Metallurgical)

In this method of heat-treatment, the ideal is to quench the part at such a rate that it reaches the Ms temperature in the fully austenitic condition. After equalization of temperature, the part is cooled slowly, so that the temperature gradients are negligible and the resulting thermal stresses are at a minimum. In practice, this ideal is only approached in so far as it is necessary to prevent cracking, reduce distortion and to obtain a given hardness. As the Ms point is usually in the region of 250oC, the quenching must be done in salt or metal bath. The quenching and time available for the equalization of temperature limits the section size that can be successfully martempered to somewhat less than that permissible with conventional quenching. Similarly, the minimum carbon or alloy content for a given section is higher. The outstanding advantages of martempering are the prevention of cracking and the minimizing of distortion, these both resulting from the reduction of thermal stresses.

Martensite (Stainless Steel)
A non-equilibrium, hard, phase that can exist in some steels. It is formed if a steel with sufficient Carbon content, usually above 0.35 to 0.4%, is heated into the austenite temperature range above 760°C, held at that temperature for a period and then quenched rapidly to room temperature. The Carbon, which is present in the lower temperature ferrite phase as carbides, dissolves in the austenite and, on quenching is trapped in, and strains, the lattice increasing the hardness. This reaction is the mechanism by which all Carbon and most alloy steels are hardened.
Martensite (Metallurgical)

A microconstituent of steel characterized by its acicular structure. Essentially a non-equilibrium condition of alpha iron formed directly from undercooled austenite. It is produced typically when steel is cooled from the hardening temperature at a speed greater than its critical cooling rate so that the transformation of austenite occurs at 400oC or below. It is the hardest of the decomposition products of austenite and is brittle but when tempered becomes softer and tough.

Martensitic Stainless Steels (Stainless Steel)
Martensitic grades of stainless steel are corrosion resistant, although less so than the austenitic grades, but can be hardened by heat treatment. They are straight Chromium steels containing little or no Nickel. They are magnetic and are mainly used where hardness, strength, and wear resistance along with corrosion resistance are required. Typical applications include cutlery, surgical instruments, fasteners, valves, pumps, springs and components for food processing.
Matrix (Metallurgical)

As used in metallography the term applies to the principal constituent in which the other constituents are embedded.

Matte (Copper)
The mixture of Copper and Iron Sulphides produced by smelting the concentrated ore
McQuaid Ehn Grain Size Test (Metallurgical)

A method of assessing austenitic grain size which was first developed to determine the cause of soft spots on case hardened steels. A specimen of steel from which all scale has been removed is carburized in a solid medium for 8 hours at 925o C. The size of the pearlite crystals, which indicates the size of the original austenite grain, is easily seen by the surrounding membranes of excess Fe C (cementite). The grain size is

measured at 100 diameters and compared with standard charts. The figures range from No.1, very coarse, to No.8, very fine.

Mean Diameter (Aluminium)
The sum of any two diameters at right angles divided by two.
Mean Wall Thickness (Aluminium)
For a tube this is the sum of four wall thickness measurements, made at 90o intervals around the diameter, divided by four.
Mechanical Properties (Stainless Steel)
The properties of a material that reveal its elastic or plastic behaviour under an applied load. They govern its suitability for any mechanical application. The usual properties considered are modulus of elasticity, yield or 0.2%/1.0% proof strength, ultimate tensile strength, elongation and fatigue limit.
Related Terms: Tensile Strength
Meehanite (Metallurgical)

A trade name applied to certain pearlitic cast irons in which the molten metal has been treated with calcium silicide resulting, it is claimed, in increased tensile strength.

Mega Pascals (Copper)
The SI unit for measuring the strength of a material and is abbreviated to MPa. Numerically it is exactly equivalent to Newtons/square millimetre (N/mm2 or Nmm-2). An approximate, rule of thumb, conversion to the Imperial measure of ton/in2 is: 1 ton/in2. = 15 MPa.
Melting Point (Metallurgical)

(Fusion Point). The temperature at which a solid begins to liquefy. Pure metals, eutectics and some intermetallic constituents melt at a constant temperature. Alloys generally melt over a range.

Metallographic Examination (Metallurgical)

The study of the microscopic features of material surfaces that have been specially prepared by cutting, grinding, polishing, and etching.

Metallurgical (Metallurgical)

Science of metals and alloys devoted to the study of engineering materials.

Microhardness (Metallurgical)

Hardness as measured with an indenter under the application of a low load, usually between 1 gram and 200 grams. Owing to the small size of the impression, the hardness of an individual phase in a microstructure can be determined.

Micron (Metallurgical)

A unit of length equal to a millionth of a metre (0.001 mm.) 0.000039 in. It is used for expressing minute distances of wave-lengths of light, and is denoted by the Greek letter µ.

MIL (Copper)
The prefix given to U.S. military specifications.
Mill Coil (Stainless Steel)
The hot rolled strip product of a single cast billet or slab.
Mill Edge (Stainless Steel)
The edge produced when sheet or strip is rolled on the flat surfaces only.
Modulus of Rigidity (Metallurgical)

In a torsion test, the ratio of the unit shear stress to the displacement caused by it per unit length in the elastic range. This modulus corresponds to the modulus of elasticity in the tension test.

Moneypenny-Strauss Test (Stainless Steel)
A corrosion test that uses copper sulphate solution containing sulphuric acid to determine the susceptibility to inter-granular corrosion of stainless steel.
Muffler Grade (Stainless Steel)
Muffler Grade stainless steel is a term sometimes used for Grade 409 (1.4512) stainless steel since the major bulk usage of this grade is for automotive exhaust systems including the catalytic converters.
Multi-Hole Die (Aluminium)
An extrusion die, with more than one hole, allowing multiple extrusions to be made simultaneously from one billet.


Natural Ageing (Aluminium)
The process that can alter the hardness and strength in some alloys after a period of time at ambient (room) temperature. It is caused by the spontaneous precipitation of constituents from a super-saturated solid solution. Generally it increases mechanical properties but can also, in some circumstances, cause loss of properties by over-ageing.
Related Terms: Ageing, Over-ageing
A nominal 62% Copper / 37% Zinc Brass that has a 1% Tin addition to improve its corrosion resistance in marine environments.
NES (Copper)
The prefix for the, now obsolete, Naval Engineering Standards. It replaced DGS and in turn was replaced by Defence Standards.
Related Terms: DGS
Neumann Bands (Metallurgical)

Narrow bands differently oriented within a grain of ferrite. Ordinarily these bands are formed only on deformation by impact, but in some alloys (silicon ferrite, for example), and particularly at low temperatures, the bands are formed more readily, as in ordinary cold-working processes. It is suggested that the Neumann band is primarily a shearing or faulting movement operating along the pre-existent planar disjunctions of the mosaic structure, and as a secondary operation, twinning may be completed, as is known to be possible in ferrite.

Nickel Silver (Copper)
Copper, Nickel and Zinc alloys. Their Copper content is similar to that of Brasses but up to 20% of the Zinc is replaced by Nickel. Silvery white in colour they have good corrosion resistance and remain “springy” at moderate temperatures.
Nitriding (Carbon & Alloy Steels)

A process for producing a hard surface on special types of steel by heating in contact with partly dissociated ammonia or other suitable medium for periods of 10 to 90 hours at a temperature of about 500 C. A hard surface can be obtained on steels containing elements such as Al, Cr, Mo, V, W, etc., which form stable carbides. The original Nitralloy steels range between 0.50 and 0.20% carbon, with about 1.5% chromium, 1.10% aluminium and 0.2% molybdenum, but other grades have been developed which contain no aluminium and are characterized by possessing a case of lower intrinsic hardness and greater ductility and toughness. Together, the various types of Nitralloy steel embrace, when nitrided, a range of surface hardness from 600-1100 diamond number.

Noble (Copper)
A term used to indicate the corrosion resistance, or the lack of it, of a material. If metals are listed in order of their general corrosion resistance, most resistant at the top and going down to the least at the bottom, the higher a metal is in the list the more “noble” it is said to be. When two different metals are connected in a corrosive environment then the least “noble” will be attacked preferentially. This effect can be used to protect structures from corrosion buy using a “sacrificial anode” of a less noble metal.
Noble Metals (Carbon & Alloy Steels)

Metals such as gold and platinum which are resistant to corrosion by all but the most powerful acids, such as aqua regia, i.e., a mixture of 3 parts hydrochloric acid and 1 part nitric acid.

Non-Ageing Steel (Metallurgical)

Low carbon steel to which is added an element (usually aluminium, less commonly titanium or vanadium) which stabilizes the active nitrogen or carbon to prevent strain ageing.

Non-Destructive Test (Stainless Steel)
Any test method, including eddy current, ultrasonic and dye-penetrant, used to detect surface and subsurface defects without damaging or destroying the product.
Non-Destructive Testing (Metallurgical)

Any form of testing which does not result in permanent damage or deformation to the part being tested. Examples are ultrasonic inspection, X-ray inspection, gamma radiography, magnetic crack detection and dye penetrant inspection.

Non-Ferrous (Metallurgical)

Metals that do not contain iron as the major alloying element.

Non-Heat Treatable Alloy (Aluminium)
An alloy, from the 1xxx, 3xxx and 5xxx series that are incapable of being strengthened by thermal treatment. These alloys gain their strength from cold-working.
Non-Magnetic Steels (Metallurgical)

Austenitic steels, such as 14% manganese-, 25% nickel-, and 18/8 chromium-nickel steels, under normal conditions.

Normalizing (Carbon & Alloy Steels)

Heating to, and if necessary holding at, a suitable temperature, i.e., about 50oC above the transformation range followed by cooling in still air so that moderately rapid cooling occurs, the object being to eliminate internal stresses, refine the grain size, render the structure more uniform, and improve the mechanical properties. It is used specially for large forgings or castings which cannot be quenched and tempered, and to produce a more uniform structure than exists in untreated pieces.

Normalizing (Metallurgical)

Commonly used heat treatment that decreases the pearlite interlamellar spacing and refines grain size. The process consists of hearting steels above the transformation temperature range, holding at temperature, and then cooling in air.


Oil Staining (Aluminium)
Surface staining caused by the partial decomposition during thermal treatment of residual lubricant.
Orange Peel (Aluminium)
A roughening, on subsequent cold deformation, of the surface of sheet or strip when the grain size is too coarse. Has the appearance of an orange skin.
Orange Peel (Stainless Steel)
The surface roughening of sheet or strip that develops on subsequent cold deformation if the grain size is too coarse. The appearance is similar to the skin of an orange.
Orange Peel Effect (Carbon & Alloy Steels)

An effect which arises from the roughening of the surface due to the coarse grain size, when steel sheets are stretched beyond their elastic limit. Also applied to the roughening of the surface of hard rolls arising from differential wear.

Ore (Aluminium)
Bauxite - A red rock found in the earth's crust, close to the surface. Extracted by open-cast mining it is a very rich ore with a 25% yield.
Ore (Copper)
A mineral that contains a metal, in combination with other elements, which is mined as a source of that metal.
Related Terms: Chalcopyrite, Chalcocite
Ovality (Aluminium)
Any variation from a true circle of the cross section of a round tube, bar or wire.
Ovality (Stainless Steel)
Any difference between the maximum and minimum outside diameters of a tube.
Over-ageing (Aluminium)
Artificial ageing treatment at too high a temperature, or for too long a time, after the maximum hardening effect has been achieved. It causes some loss of properties. In some cases it may be a deliberate act, e.g. to improve resistance to stress corrosion or to minimise any further loss of properties in alloys operating at higher temperatures.
Oxide Film, Passive Film (Stainless Steel)
Generally it is the oxide layer spontaneously formed on the surface of a metal or alloy by its reaction with the oxygen in the atmosphere. Specifically in stainless steels it is the protective chromium oxide film that forms on alloys containing more than 10.5% chromium that is impervious to many corroding media. It is why stainless steels are “stainless”.


Partial Annealing (Aluminium)
Thermal treatment, after cold working, of a work-piece to reduce its strength to a controlled, but not fully softened, level.
Passivation (Stainless Steel)
Treatment in oxidising acids to remove light surface contamination by iron based materials left by machining or wire brushing and to enhance the naturally occurring chromium oxide film. Any residual contaminants can act as sites for corrosion cells. Heavy contamination or other contaminants (mill scale, etc.) should be removed by acid pickling before passivation.
Patina (Copper)
The greenish layer that naturally develops on Copper exposed to the atmosphere. Chemically it is a complex mixture of Chlorides, Carbonates and Sulphides. Pre-patinated sheet is used for roofing applications.
Pearlite (Metallurgical)

The lamellar conglomerate of ferrite and cementite which constitutes the eutectoid in the iron-carbon equilibrium system. It results from the transformation of austenite at or below Ar , and is so called from the mother-of-pearl lustre given by an etched surface when viewed under the microscope. This pearly appearance is due to the fine and regular alternation of the two constituents. The lamellar arrangement of ferrite and cementite produces a tough structure and is responsible for the mechanical properties of the unhardened steels. Pearlite is present in small quantities in low carbon steels and increases in quantity as the carbon increases, until in a plain carbon steel, containing about 0.83 per cent of carbon, the structure consists entirely of pearlite.

Peeled Bar (Metallurgical)

A round bar that has been centreless machined to remove its outer surface. The peeling process takes less than one fourth the time of conventional lathe turning operations.

Percentage Elongation after Fracture (A) (Aluminium)
The gauge length elongation after fracture expressed as a percentage of the original gauge length.
Peripheral Coarse Grain, Peripheral Grain Band (Aluminium)
An effect shown in extruded products and also forgings made from extruded stock. It is an area of recrystallised grains at the periphery which has lower properties than the non-recrystallised core.
Permanent Set (Metallurgical)

(a) An extension remaining after the load has been removed from a test piece when the elastic limit has been exceeded (see Elastic Limit).

(b) Permanent deflection of any structure after being subjected to a load.

Permeability (Metallurgical)

(a) The ratio B/H for a magnetized material, where B is the flux density produced and H is the magnetizing force.

(b) In sand, a measure of that physical property which permits gas to pass through the moulded mass of sand.

Phase (Stainless Steel)
Any constituent part of an alloy, e.g. elemental metal, solid solution, or inter-metallic compound, that is physically and chemically homogeneous and distinct within the microstructure.
Phase Diagram (Metallurgical)

(Thermal Equilibrium Diagram). A graph showing the limits of composition and temperature of the various phases present in an alloy system under equilibrium conditions. A phase is the name given to a constituent which can be distinguished from the remainder of an alloy by physical and chemical methods such as etching, and in the solid may be a solid solution, an element or an intermetallic compound.

Phosphor Bronze, Leaded Phosphor Bronze (Copper)
Hard and strong cast and wrought Copper/Tin alloys with small, deliberate, Phosphorus additions. Wrought alloys such as PB102 contain 4% to 8% Tin, whilst cast alloys contain 9% to 12% Tin. Leaded Phosphor Bronzes, with Lead contents up to 20% ,are usually available only as castings – Examples are PB1 and SAE660.
Photoelasticity (Metallurgical)

A property of transparent substances which enables the presence of strain to be detected by examination in polarized light. If models of engineering structures are made of such a substance, the stress distribution in the structures may be deduced.

Photomicrograph (Metallurgical)

A photographic reproduction of a microstructure.

Physical Properties (Stainless Steel)
The intrinsic properties of a material, e.g. density, electrical conductivity, thermal conductivity, thermal expansion that govern its behaviour and potential for use in an application.
Pick-up (Aluminium)
Irregular surface roughness or damage caused by adhesion and subsequent fracture or tearing between the forming tools and the work piece.
Pickling (Carbon & Alloy Steels)

The process of chemically removing scale or oxide from metal objects to obtain a chemically clean surface. This is usually effected by immersion in an acid bath. For steel, the acids generally employed are sulphuric and hydrochloric to which is added an inhibitor (restrainer).

Pickling, Acid Pickling (Stainless Steel)
The removal, by immersion in a solution containing nitric and hydrofluoric acids, of the scale left after hot working or annealing. It leaves a matt grey finish.
Related Terms: Passivation
Pinch Passing, Skin Passing (Stainless Steel)
A cold rolling pass, with minimal reduction of thickness, of annealed sheet or strip. It reduces the tendency to kinks, flats and stretcher strains on subsequent manipulation. Flat material so treated is described as 'skin passed', 'pinch passed', 'non-kinking', 'non-flatting' or 'killed'. The material will also be brighter and have closer tolerances.
Pipe, Pipes (Stainless Steel)
Tubular products made to Nominal Bore and Schedule Wall Thickness dimensions specified by ANSI/ASTM standards. Sizes specifically for Stainless Steel Pipe are to ANSI B36.19 where the Schedule Wall Thickness has an S after the number to denote Stainless – e.g. Schedule 40S. Stainless Steel Pipe can also be made to the ANSAI B36.10 sizes intended for carbon/mild/alloy steels where the schedule has no S after it.
Pips, Pip Lines, Pip Marks, Ident Pips (Aluminium)
A marking on an extrusion (on a non-visible surface) placed there by the extrusion mill’s die to allow the mill to identify extrusions produced by that mill.
Pit (Stainless Steel)
A corroded hollow in a metal surface, caused by localised corrosion (pitting).
Pitting Corrosion (Aluminium)
Non uniform corrosion of the surface that causes small pits or craters to develop.
Pitting Corrosion (Stainless Steel)
Concentrated, localised, corrosion attack that can reach considerable depths and cause premature failure.
Pitting Corrosion (Metallurgical)

Passive metals are resistant to a wide variety of corrosive media but under certain conditions breakdown of the passive film may occur at various points. Depending on the conditions, this may lead to a complete breakdown of the passive film or the attack may concentrate at these initial areas, leading to rapid failure by pitting.

Plastic Flow (Metallurgical)

The deformation of metals by the mechanism of slip along definite geometric planes within the crystals.

Plate (Aluminium)
A hot rolled flat product of rectangular section, typically over 10mm thick. Control of surface finish is less rigorous than for sheet.
Related Terms: Sheet, Shate
Poling (Metallurgical)

Stirring molten metal, either in a furnace or in a ladle, with a pole of green wood, the heat distilling off the volatile products which stir up the metal, and, together with the charcoal formed, help to reduce any oxide present.

Porthole Dies (Aluminium)
Dies that produce extruded hollow products from solid extrusion ingots. They incorporate a mandrel as an integral part of the die assembly and leave one or two ‘weld’ seams along the extrusions.. Bridge, spider, duo and self-stripping dies are particular types of porthole die.
Powder Coating (Aluminium)
Application of an even layer of colour to aluminium extrusions by spraying powdered paint using an electrostatic process then baking on (stove enamelling).
Powder Metallurgy (Metallurgical)

The art of producing metal powders and forming them into coherent objects. Individual, mixed, or alloyed metal powders, with or without the inclusion of non-metallic constituents, are pressed or moulded into objects which may be simultaneously or subsequently heated to produce a coherent mass, either without fusion or with the fusion of a low melting constituent only.

Pre-Ageing (Aluminium)
A thermal treatment after quenching and before the end of the precipitation incubation period.
Precipitation Annealing (Aluminium)
The heating of a quenched and precipitation hardened work piece for some time at a temperature between the artificial ageing temperature and the solution treatment temperature. It produces significant softening by coalescing the hardening precipitates.
Precipitation Hardening Stainless Steels (Stainless Steel)
Precipitation hardening stainless steels are Iron, Nickel, Chromium alloys that also contain precipitation hardening additions such as Aluminium, Titanium, Copper, Niobium and Molybdenum. They offer higher mechanical properties than the austenitic grades, with lower toughness and do have comparable corrosion resistance.
Pressure Test (Aluminium)
A hydraulic or pneumatic test for tubes to prove that they material can withstand a specified pressure for a specified time without leakage or rupture.
Pressure Test (Stainless Steel)
A hydraulic or pneumatic test for tubes to prove that the material can withstand a specified pressure for a specified time without leakage or rupture.
Process Annealing (Carbon & Alloy Steels)

A process, commonly applied in the sheet and wire industries, in which an iron-base alloy is heated to a temperature close to, but below, the lower limit of the transformation range, and subsequently cooled. This process is applied for the purpose of softening for further cold-working.

Proof Strength (Stainless Steel)
The tensile load required to extend a sample of material by 0.2% (RP0.2) or 1% (RP1.0). Measured in Newtons per square mm (Nmm-2) or Mega-Pascals (MPa).
Proof Stress (Metallurgical)

The stress which is just sufficient to produce a permanent elongation equal to a specified percentage of the original gauge length. It can be determined :-

(a) By direct measurement of the gauge length after various loads have been applied to the test piece and removed; Or

(b) From the load-elongation curve by drawing a line parallel to the straight portion of the curve and distant from it by an amount representing the required permanent elongation, thus determining the load at which the line cuts the curve.

Proof Stress (Rp) (Aluminium)
The stress or applied load which produces a permanent elongation equal to a specific percentage of the original gauge length. In alloys that do not exhibit a yield point it is used as an equivalent to the elastic limit. If a proof stress is specified, the non-proportional elongation must be stated. The most common values used in specifications is 0.2% or 1.0% and the RP symbol used for the stress will be supplemented by an index giving this prescribed percentage of the original gauge length, e.g. RP0.2 = 0.2% Proof Stress


Quarto Plate (Stainless Steel)
Quarto Plate is hot rolled plate over 12mm thick that will not have been coiled during the production by hot rolling as compared to CPP plate, which is up to 12mm thick and will have been coiled up during the hot rolling. For more information and the stock range please click on the link below.
Related Terms: CPP Plate
Quenching (Aluminium)
The rapid cooling a metal or alloy from the solution treatment temperature by contact with a solid, a liquid or a gas to retain the hardening constituents in solid solution. Quenching is often carried out by immersion in cold water. Extrusions are quenched after extrusion by air blasts.
Quenching (Metallurgical)

Rapid cooling of a heated metal generally by immersion in liquids, to increase strength and hardness. Quenching is always followed by a temper to increase ductility.

Quenching (Carbon & Alloy Steels)

Rapid cooling from an elevated temperature, generally carried out by immersion in a liquid bath of oil or water. The usual effect is to confer hardness as the sudden abstraction of heat suppresses the phase transformation of austenite to pearlite, forming instead the harder constituents bainite and/or martensite. The austenitic steels such as Staybrite and 14% manganese steel are not hardened by quenching.

Quenching Crack (Metallurgical)

Rapid cooling of a heated metal generally by immersion in liquids, to increase strength and hardness. Quenching is always followed by a temper to increase ductility.


Radiography (Metallurgical)

A non-destructive method for internal examination of a metallic body exposed to a beam of X-ray or gamma radiation. Differences in thickness, density or absorption caused by internal defects or inclusions are apparent in the shadow image, either on a fluorescent screen or on a photographic film placed behind the object.

Recrystallisation (Stainless Steel)
The change in crystal structure of a cold worked metal that occurs when heated through a specific temperature range.
Recrystallisation Annealing (Aluminium)
A heat treatment that softens a cold worked metal or alloy by complete recrystallisation.
Rectification (Aluminium)
Work done to correct dimensional errors.
Red Shortness (Metallurgical)

Brittleness in a metal when red hot, causing it to crack when under the hammer or during rolling. It may be caused by the presence of a high sulphur content which exists in the form of sulphide.

Reduction of Area (Metallurgical)

(a) The percentage decrease in the cross-sectional area of a tensile test piece caused by the waisting or necking of the specimen. It is expressed as a percentage of the original area of the test piece and is a measure of ductility.

(b) The percentage decrease in cross-sectional area of bar or wire after rolling or drawing.

Refining (Copper)
The further purification of Blister Copper by removal of its Oxygen content and recovery of any rare or precious metals that were present in the ore by either: a) fire refining in a furnace b) electrolytic refining, in which the blister Copper is cast into anodes, suspended in an acid solution and deposited on to plates at the cathode by electrolysis.
Residual Stress (Aluminium)
Any stress in a finished product after fabrication (mainly cold work) which exists without the presence of any service or external loads, even after stress relieving.
Resilience (Metallurgical)

A general term for the power of an elastically strained body of spring back on removal of the load. Strictly it is the potential energy stored up by an elastically strained body and given out when the load is removed. It is expressed in energy units such as foot pounds per cubic inch. The proof resilience is the greatest amount of energy that can be stored up by a body strained only elastically.

Riveting Brass (Copper)
CW606N / CZ131 Brass formulated to be most suitable for riveting.
Rockwell Hardness Tester (Metallurgical)

Rockwell hardness numbers are based on the additional depth to which an indenter is driven into a metal by heavy load beyond the depth to which the same indenter has been driven by a light load, the conditions under which this happens being arbitrary but definite. For the inspection of hard steel parts the sphero-conical diamond Brale penetrator is used with a major load of 150 kg. The number indicated on the black scale of the dial is observed and is prefixed invariably by the letter C, as C-62. For the testing of rolled, drawn, extruded and cast metal, with the exception of very soft metals or very thin pieces, the penetrator employed is the 1/16 in. diameter steel ball with the other standard load, 100 kg. The readings are then taken from the red calibration on the dial and the prefix is the letter B, as B-68. Tests can also be made with other load penetrator combinations than are required for the standard "B" and "C" scales, for example, a 60 kg. major load with a Brale penetrator is used for the "A" scale.

Roll Marks (Stainless Steel)
Periodic surface marks on a work-piece caused by imperfections on the surface of a roll.
Rolled-in Scale (Stainless Steel)
A surface defect caused by patches of scale that were pressed into the surface of the work-piece during rolling.
Roller Levelling (Stainless Steel)
The process of flattening sheet metal by passing it through a roll train of staggered rolls. Levelling is achieved by precisely bending metal strip back and forth as it is passed through a the series of small-diameter offset rolls.
Roller Levelling, Tension Levelling (Aluminium)
Flattening of sheet, strip or coil metal by passing it through a roll train staggered rolls. Levelling is achieved by precisely bending metal strip back and forth as it's passed through a series of small-diameter offset rolls. The material is usually also under tension loading.
Roller Straightening (Aluminium)
The straightening of extrusions by passage through a series of small diameter, staggered, rolls.
Rolling (Carbon & Alloy Steels)
  1. The process of shaping steel by passing it between two rolls revolving at the same peripheral speed and in opposite directions.
  2. The preparation of a cylindrical forging by rounding stock between swaging tools prior to the drop forging operation.
  3. An operation similar to tumbling, in that the metal parts and abrasives are loaded in a barrel or similar mechanism, but differing in that the work and abrasives are rolled in such a way that the load rolls over and over upon itself in a continuous flowing motion in relation to the rotating barrel. Such rolling removes flash, rough spots and scale, and cuts down a metal surface to an even and uniform condition.
Rotary Furnace (Carbon & Alloy Steels)

A furnace having a hearth, circular in plan view, which is slowly rotated, the walls and roof being stationary. The workpieces are charged through a door on to the hearth and are carried round for one revolution during which they pass various burners adjusted to complete the required temperature cycle.


SAE, SAE600 (Copper)
The US Society of Automobile Engineers -the body that develops standards and specifications for the U.S. motor industry. The value and applicability of SAE standards is widely appreciated and they are now used in other industries and countries. For example, Cast Leaded Gunmetal to specification SAE660 is popular in the UK.
Scaffolding Tube (Aluminium)
A ‘welded’ tube, size 1 29/32 inch O/D x 7 swg wall thickness (7swg = 0.176 inch / 4.47mm) used for scaffolding that has been Drift Tested
Scalping (Aluminium)
Mechanical removal of oxide and contamination from surface of a cast slab prior to hot rolling.
Sealing of Anodic Coatings (Aluminium)
A post anodising treatment to close layer porosity and reduce absorbency.
Season Cracking (Copper)
So called because it was first observed, in the rainy season in India, on deep drawn 70/30 brass cartridge cases that had been stored in horse stables where the atmosphere contained Ammonia.
Related Terms: Stress Corrosion
Season Cracking (Metallurgical)

Cracking resulting from combined corrosion and internal stress. It occurs in severely cold-worked materials. The term is usually applied to the stress corrosion cracking of brass.

Segregation (Aluminium)
The non uniform distribution in the microstructure of alloying elements during the solidification of an ingot, billet or slab. Some non metallic impurities may also be segregated during solidification.
Segregation (Metallurgical)

The non-uniform distribution of impurities or alloying elements. The phenomenon depends not only on the chemical composition of the alloy, but also on the rate of cooling, both of the ingot as a whole, and of each individual point within the mass. For example, and referring more particularly to piped ingots, near the walls, where the rate of cooling is rapid, the segregated impurities are trapped in the rapidly growing crystals. Further inside the ingot, where the cooling is slower, the segregates will collect together and produce the so-called ghosts, or they may tend to rise to the surface and collect in the scrapped ingot head. In normal segregation, the constituents with the lowest melting points concentrate in the last portions to solidify, but in inverse segregation this is reversed. The segregation tends to form in bands sloping inwards to the top of the ingot (A segregate) and at the same time, due to shrinkage, it takes a V shape (V segregate) along the upper part of the ingot axis.

Self-Quenching Alloy (Aluminium)
An alloy whose critical quench rate from its solution treatment temperature is slower than the rate of cooling in still air. This means that the alloying elements will be held in solid solution even after cooling in still air.
Sensitisation (Stainless Steel)
Sensitisation occurs because Chromium has a higher affinity for Carbon than does Iron. Welding and some heating cycles provide the thermal energy for chromium carbides form in preference and these precipitate within the microstructure. This process causes the steel to become susceptible to corrosion as the matrix areas around the carbide are depleted in Chromium and cannot form the protective oxide film.
Related Terms: Sensitised, Carbide, Stabilised Grades, Inter-granular Corrosion
Sensitised (Stainless Steel)
This describes the condition of a stainless steel that, having been welded or otherwise thermally processed, now has chromium carbide particles present in the grain boundaries. In this condition the steel becomes susceptible to corrosion as the matrix areas around the carbide are depleted in chromium and cannot form the protective oxide film.
Related Terms: Sensitisation, Carbide, Stabilised Grades, Inter-granular Corrosion
Shate (Aluminium)
A term used for rolled material where the thickness lies between that of cold rolled sheet and hot rolled plate, typically 4 to 10 mm. the finish may be hot or cold rolled.
Shear Strength (Aluminium)
The maximum stress that a material can sustain when loaded in shear. As a very rough guide for aluminium alloys the maximum shear strength is about 60 to 65% of the ultimate tensile strength and the yield strength in shear is 50 to 55% of the 0.2% Proof Stress.
Shear Test (Aluminium)
A test in which the test piece is progressively loaded to fracture in shear to measure its shear strength.
Sheared Edges (Stainless Steel)
The cut edges that are produced when a wide sheet or coil is sheared or slit, by rotary cutters or a guillotine, into narrower widths/lengths.
Shearing (Stainless Steel)
The operation of cutting sheet or strip to the required size with a guillotine.
Sheet (Aluminium)
Usually defined as cold rolled flat product in the thickness range 0.25mm to 3.25mm.
Shore Sleroscope (Metallurgical)

An instrument which consists essentially of a small diamond-tipped hammer which falls freely down a graduated glass tube from a constant height on to the surface of the sample under test. The hardness, or the elastic quality, is measured by the height of the rebound. In one form of the instrument the rebounding hammer actuates the pointer of a scale so that the height of the rebound is recorded.

Short Transverse Direction (Aluminium)
The minor axis at right angles to the major, longitudinal, axis.
Shot Blasting (Carbon & Alloy Steels)

A method of cleaning the surface of metals by abrasion, as in sand-blasting, the sand being replaced by broken shot or steel grit. It is less effective than sand-blasting, as the peening effect of the shot tends to drive the unwanted deposit, e.g., oxides, into the surface of the metal.

Shot Peening (Carbon & Alloy Steels)

Superficial cold working by directing a stream of metal shot on to the surface of a metal article. The fatigue strength is improved since the surface becomes slightly work hardened and acquires a residual compressive stress.

Sigma Phase (Metallurgical)

Originally a phase in iron chromium alloys containing essentially the compound FeCr, but the term has subsequently been extended to include similar related phases in other systems. It is stable at temperatures of the order of 900 C. and may occur in stainless steels where, because of its hard brittle nature, it is undesirable.

Silver Steel (Carbon & Alloy Steels)

A name given to bright drawn carbon steels, containing about 0.95-1.25% carbon with low sulphur and phosphorus and normal silicon and manganese. It has no silver in its composition.

Single-Hole Die (Aluminium)
An extrusion die with one hole, therefore capable of producing just one extrusion per cycle.
Related Terms: Multi-Hole Die
Sinking, Sink Drawing (Stainless Steel)
The cold drawing of a tube without a mandrel in the bore to control bore dimensions. It enables closer tolerances to be achieved on the outside diameter and increases mechanical properties.
Related Terms: Cold Drawing
Slab (Stainless Steel)
A hot rolled or forged primary feedstock for rolling or forging. The cross-section is rectangular, typically with a width more than twice the thickness.
Slab, Rolling Slab (Aluminium)
A cast product that will be used for hot rolling. Size up to 300mm thick, 2000mm wide and 10/15 metres long with weight up to 15 tonnes.
Slip (Metallurgical)

The mechanism of cold deformation wherein one part of a crystal glides over another part along certain planes known as slip planes.

Slip Bands (Metallurgical)

A series of parallel lines showing across the individual crystals of a deformed polished surface.

Slitting (Aluminium)
The simultaneous cutting of a coil or wide strip into a number of narrower strips by means of rotary cutters.
Slitting (Stainless Steel)
The operation of continuously cutting a wide coil of strip into a narrower strips by rotary cutters. The narrower strips are usually re-coiled after slitting.
Smelting (Copper)
A stage in the extraction of Copper from its ores. The ore concentrate is melted, with a flux, in a reverberatory furnace to produce Copper Matte, a mixture of Copper and Iron Sulphides that contains 30% to 40% Copper.
Related Terms: Copper Matte, Matte
Solid Solubility (Metallurgical)

The extent to which one metal is capable of forming solid solutions with another. This capacity varies considerably: some metals are almost insoluble in each other, whilst others are mutually soluble in all proportions.

Solid Solution (Copper)
If alloying elements are retained in the lattice of the parent metal instead of forming a different phase they are said to be in solid solution. Alloys which that are multi-phase at room temperature can usually be made single phase by heating to a suitable temperature below the melting point, by holding at this temperature, then quenching in water, oil or cold air. The alloying element(s) have been taken into solid solution by the heating and retained there by the rapid cooling. They can be precipitated out by heating again, to a lower temperature, a process called ageing. The two stages are a useful heat treatment cycle for many alloys including Beryllium Copper.
Solid Solution (Stainless Steel)
The name given to an alloy, e.g. Iron Chromium, phase which appears, in the microstructure, to be one material. In Iron Chromium solid solutions the Iron is the major constituent and the Chromium, the “alloying element”, atoms occupy places within the iron lattice and modify its properties. Solid solutions are fundamental in metallurgy. Pure metals have definite melting and freezing points, solid solutions have a melting and freezing range.
Solid Solutions (Metallurgical)

A homogeneous solution of two or more crystallized bodies in the solid state.

Solidus (Metallurgical)

A line or surface in a constitutional diagram indicating the temperatures at which solidification is completed or melting begins in alloys and other melts of different composition, i.e. the line or surface below which the alloys are in a solid condition (Cf. Liquidus).

Solution Heat Treatment (Metallurgical)

A treatment in which an alloy is heated to a suitable temperature and held at this temperature for a sufficient length of time to allow a desired constituent to enter into solid solution, followed by rapid cooling to hold the constituent in solution. The material is then in a supersaturated, unstable state and may subsequently exhibit age hardening.

Solution Treatment, Solution Annealing (Stainless Steel)
A heat treatment process to dissolve precipitated carbides followed by quenching or rapid cooling to retain the carbon into solid solution. This restores the chromium content of the matrix and hence the corrosion resistance.
Related Terms: Sensitisation, Inter-granular Corrosion
Space Lattice (Metallurgical)

The dimensional geometric pattern in which the atoms of a metal arrange themselves, and upon which a crystal is built. There are several known lattice configurations, but most metals crystallize in one of three types:

(1) Face centred cubic;

(2) Body centred cubic; and

(3) Close packed hexagonal.

Spark Testing (Metallurgical)

A method of determining the approximate composition of steel by holding a sample on a grinding wheel and producing sparks. An experienced operator can detect differences in the carbon content of steels of 0.05% in the range up to 0.35% and 0.10% in the range from 0.35 to 0.60%. The effects of alloying elements such as tungsten molybdenum, chromium, nickel, silicon and manganese are also recognizable.

Springback, Spring Back (Stainless Steel)
The tendency of a metal work-piece that has been deformed to not stay exactly in the shape to which is has been manipulated, but instead to spring back a little. Stainless steels spring back more than mild/carbon/alloy steels and thus need to be over-bent to a greater degree.
Stabilised Grades (Stainless Steel)
Stainless Steels whose composition has been modified by additions of Titanium or Niobium to overcome sensitisation and its consequent problems. The mechanism is that these elements have a higher affinity for Carbon than does Chromium so their Carbides form in preference. The Chromium content of the matrix is therefore not reduced so it corrosion resistance is retained.
Stabilizers (Carbon & Alloy Steels)

Elements added to austenitic stainless steels, of the type containing 15 to 20% chromium and 12 to 8% nickel, for the purpose of forming a stable carbide, thus preventing any tendency to intercrystalline corrosion or weld decay. The stabilizers in most common use are titanium and niobium. (The titanium should be added to the extent of 4 to 5 times, and niobium 8 to 10 times, the carbon content.)

Stainless Steel (Stainless Steel)
Stainless Steel is the term used to describe an extremely versatile family of engineering materials, which are used primarily for their corrosion and heat resistant properties. All Stainless Steels are alloys of Iron and Chromium, with a minimum Chromium content of about 10.5%, and with varying Carbon content. This Chromium content develops a self-repairing Chromium Oxide surface film which prevents the surface rusting typical of many other types of steel. Higher Chromium content will further enhance corrosion resistance and some stainless grades also contain other alloying elements including Nickel and Molybdenum. Most commonly you will see reference to “austenitic stainless steel”, “ferritic stainless steel”, “martensitic stainless steel”, “duplex stainless steel” and “precipitation hardening stainless steel”.
Stainless Steel Designations (Stainless Steel)
Stainless steels are governed by a wide range of Proprietary, National, European and International standards. This range of standards has led over time to the use of a number of designation systems. Many people are familiar, and comfortable with, the 3-digit system that originated in the USA and was adopted into former British Standards in which 2xx and 3xx designations were applied to austenitic grades (e.g. 201, 304, 304L) 4xx designations were applied to ferritic and martensitic grades (e.g. 410, 430) In Europe these have now been replaced by BSEN numbers of the type 1.4xxx (e.g. 1.4301) although the American 3-digit system is still widely used.
Stamping Brass, Hot Stamping Brass (Copper)
CW617N / CZ122 Brass formulated to be most suitable for hot stamping.
Stop Mark (Aluminium)
A transverse peripheral ridge on a product arising from a stoppage during rolling, extrusion or drawing.
Straightness Tolerance, Camber (Stainless Steel)
The permitted deviation from a true straight line, or bow, within a specified length of a product. The usual methods to determine such a deviation are with a straight edge and dial gauge or a flat plate and feeler gauges.
Strain Hardening, Work Hardening (Aluminium)
The increase in strength and hardness with a general loss of ductility that results from cold working of a work-piece.
Related Terms: Cold Working
Streching, Stretcher Levelling (Aluminium)
A term used to describe both the levelling of rolled materials and the straightening of extruded and drawn materials by imparting sufficient permanent extension to remove distortion.
Stress (Stainless Steel)
Stress is the measure of the forces acting within a deformable body or work-piece when it is under load. These forces will seek to resist any permanent change in shape of the body or work-piece until the yield point strength of the material has been exceeded.
Stress Corrosion (Aluminium)
This is the frequently rapid, sudden, failure of normally ductile alloys when experiencing tensile stresses in certain and specific corrosive environments. These stresses may be residual internal stresses or from external loading.
Stress Corrosion (Copper)
Stress Corrosion is the rapid and often abrupt failure of a normally ductile metal or alloy caused by residual or other stresses in the work-piece and in the presence of specific corroding agents. It is temperature dependent. Alpha Brasses are susceptible in atmospheres that contain Ammonia. The effect can be mitigated to some extent by a stress relieving heat treatment but, if the service conditions pose any risk of stress corrosion, an alternative alloy such as Aluminium Bronze is preferred.
Stress Corrosion (Metallurgical)

The term implies a greater deterioration in mechanical properties of material through the simultaneous action of static stress and exposure to corrosion than could occur by the separate but additive action of those agencies. It is often accompanied by cracking.

Stress Corrosion Cracking (Stainless Steel)
Stress Corrosion Cracking (SCC) is the rapid and often abrupt failure of a normally ductile metal or alloy caused by residual or other stresses in the work-piece and in the presence of specific corroding agents. It is temperature dependent. Austenitic stainless steels are susceptible in chloride environments temperatures above 60°C. Ferritic grades are immune to this form of attack.
Stress Relief Heat Treatment (Carbon & Alloy Steels)

(Stress Relieving). A process of reducing residual stresses in a metal object by heating to a suitable temperature, e.g., 600o to 650o C. and holding for a sufficient time for the internal stresses to be released by creep. After soaking, the structure is allowed to cool slowly. This treatment may be applied to relieve stresses induced by casting, quenching, normalizing, machining, cold-working or welding.

Stress Relieving (Stainless Steel)
An annealing heat treatment used to reduce internal stresses in steel after fabrication.
Related Terms: Annealing
Stress Strain Curve (Metallurgical)

A graph similar to a load extension curve except that stress (load divided by the original cross-sectional area of the test piece) is plotted against strain (the extension divided by the length over which it is measured).

Stretcher Grip Marks (Aluminium)
Transverse indentations left by the gripper jaws of the stretching machine on the ends of a product.
Stretcher Strain Markings (Aluminium)
These are permanent surface distortions that can occur on stretching. They can appear as either flamboyant patterns or Lüders lines. Their onset and extent depends on the type of material and the degree of stretching.
Stretcher Strains (Metallurgical)

(Lüders Lines). Irregular lines appearing on the surface of some materials, particularly mild annealed steel sheet or strip, on cold working. The markings can be prevented by temper rolling the sheet after annealing.

Sub-Critical Annealing (Carbon & Alloy Steels)

(Process Annealing). Heating to, and holding at, some temperature below the transformation range. Subsequent cooling may be in air.

Sulphur Print (Metallurgical)

A macrographic method of examination for the distribution of impurities in which a sheet of bromide paper, after being soaked in dilute sulphuric acid, is placed upon the plane polished surface to be examined. The sulphides in the steel react with the acid, liberating hydrogen sulphide which again reacts with the silver salt in the paper, leaving a dark brown stain, thus indicating the distribution of the sulphur.

Super Annealing (Aluminium)
An annealing cycle for heat treatable alloys that utilises a slow, controlled, cooling rate to produce a structure with maximum ductility and the minimum tendency to natural ageing.
Surface Bloom (Aluminium)
A general term for any surface discolouration caused by thermal treatment or from exposure to moist atmospheres.
Swaging (Stainless Steel)
A cold forging process in which the dimensions of a tube are altered by blows delivered rapidly against its outside diameter. An internal mandrel is usually used.
Swaging (Carbon & Alloy Steels)

A process by which metal is worked into the desired shape by a series of blows rapidly applied by suitably shaped dies in order to produce close tolerances in cylindrical or tapered bars or tubes. In hand swaging, the bar or tube is rotated whilst the dies are stationary. In machine or rotary swaging, the dies, usually two in number but sometimes four on large machines, reciprocate rapidly as the spindle on which they are mounted rotates. This means that the finished work must be round, but within this limitation swaging can be applied to a wide variety of pointing, tapering, sizing and reducing operations.


Temper (Metallurgical)

Heat treatment process performed after quenching or normalizing. The forging is heated to a temperature below the critical range and cooled at a suitable rate. Tempering steel after hardening to relieve quenching stresses ensures dimensional stability and obtains specified mechanical properties.

Temper (Copper)
A term used to describe the degree of work hardening in a cold worked, usually rolled, material. The range is from “fully annealed” to “fully hard”. For Alpha Brasses the intermediate quarter hard or half hard tempers are usually achieved by temper annealing fully hard material. Copper sheet and strip can be given the correct temper by temper rolling, starting with fully annealed material.
Related Terms: Annealing
Temper (Carbon & Alloy Steels)
  1. The operation of tempering.
  2. The degree of hardness left in a steel after quenching and tempering.
  3. The amount of carbon present in a steel, e.g., razor temper 1.5% C, file temper 1.3%C, die temper 0.75% C.
  4. The percentage increase in length of a sheet after cold rolling.
  5. The degree of hardness of cold rolled low carbon steel strip as controlled by heat treatment and cold deformation. Strip is produced in a series of tempers from full hard or hard temper (in the U.S.A No.1 temper), which is the most heavily cold rolled condition, to soft or dead soft (No.5 temper U.S.A.) which is the annealed condition.
  6. The moisture content of a sand at which any certain maximum physical test value is obtained.
  7. (verb) The process of mixing sand with sufficient water or other liquid to develop its moulding properties.
Temper (Aluminium)
The characteristic structural and mechanical properties produced by mechanical working and/or thermal treatments.
Related Terms: Temper Designations
Temper Designations (Aluminium)
There are two systems of letters and digits used, after the alloy designation number, to define and describe the temper of an aluminium alloy. The following is only an outline guide to these systems. For the strain hardening alloys of 1xxx, 3xxx and 5xxx series the following is used:- O = Annealed, soft F = As Fabricated H1x = Strain Hardened only H2x = Strain Hardened and partly annealed. H3x = Strain Hardened and stabilised H4x = Strain Hardened and organically coated with an oven cure. The second number shown as x above indicates the final degree of hardness or strength. 2 = quarter hard 4 = half hard 6 = three quarter hard 8 = fully hard. For the heat treatable alloys of the 2xxx, 6xxx,7xxx and 8xxx series the following applies. T1 = cooled from a high temperature forming process and naturally aged. T2 = cooled from a high temperature forming process cold worked and naturally aged. T3 = solution treated, cold worked and naturally aged. T4 = solution treated and naturally aged. T5 = cooled from a high temperature forming process and age hardened by heat treatment. T6 = solution treated and age hardened. T7 = solution treated and deliberately overaged T8 = solution treated, cold worked and age hardened T9 = solution treated, age hardened then cold worked. Additional numbers may also appear to indicate variations in treatment that can significantly influence the condition of the alloy.
Temper Rolling (Aluminium)
A controlled cold rolling procedure performed to develop specific mechanical properties in a work piece.
Tensile Strength (Metallurgical)

(Maximum Stress). (Ultimate Tensile Stress). The highest load applied in breaking a tensile test piece divided by the original cross-sectional area of the test piece.

Tensile Strength, Ultimate Tensile Strength (UTS) (Aluminium)
The maximum load, in tension, that a material can withstand before breaking. It is calculated as a breaking load for a standard cross section area.
Tensile Test (Aluminium)
A procedure to measure the mechanical properties of a representative test piece in tension. The test piece is progressively loaded in tension and its gauge length plotted against the applied load generally to the point of fracture. The Proof Stress (Rp) and Tensile Strength (Rm) values are then determined.
Tensile Test (Metallurgical)

A test in which specimens are subjected to an increasing tensile pull, until they fracture. A stress-strain curve may be plotted and the limit of proportionality, proof stress, yield point, tensile strength, elongation and reduction of area determined.

Tolerance (Stainless Steel)
The permissible limit, or limits, of variation to a specified parameter such as a dimension or weight per unit length usually expressed as 'plus' or 'minus' value on that quantity.
Tolerance (Aluminium)
The permissible limit, or limits, of variation to a specified parameter such as a dimension or weight, usually expressed as 'plus' or 'minus' value or percentage on that quantity.
Torsion Test (Aluminium)
A test in which a sample is twisted axially for a given number of revolutions. It may be conducted to destruction or to demonstrate that the material can withstand a specific amount of twisting.
Tough Pitch Copper (Copper)
An obsolete term for Copper that has been cast with a deliberate Oxygen addition (typically 0.01 % - 0.05%) to improve electrical conductivity. The metal may have first been either the electrolytically or fire refined.
Toughness Testing (Metallurgical)

Test used to assess the resistance of metals to brittle fracture propagation in the presence of stress raisers.

Traffic Marks, Fretting (Aluminium)
Abrasions, usually dark in colour, resulting from relative movement, or rubbing, between contacting metal surfaces during transit.
Transformation Range (Metallurgical)

(Transformation Temperature Range). The temperature interval within which austenite forms while ferrous alloys are being heated. Also the temperature interval within which the austenite transforms while ferrous alloys are being cooled. The range on cooling is lower than the corresponding range on heating: this phenomenon is known as thermal hysteresis. The limiting temperature of the ranges depends on the composition of the alloy and on the rate of change of temperature, particularly during cooling. If the transformation temperatures under conditions of equilibrium are plotted against carbon content of the steel, a diagram similar to the one shown in Figure 1 is obtained. On progressively heating hypo-eutectoid steels through the transformation range, ferrite dissolves in the austenite and on reaching the A point, solution is complete. In hyper-eutectoid steels, cementite progressively dissolves in the austenite. Eutectoid steels transform completely to austenite at a fixed temperature. The addition of alloying elements may profoundly modify the transformation ranges. The limits of the transformation range may be determined by measuring the temperatures at which evolution of heat (on cooling) or absorption (on heating) occurs. Other methods of determination include the measurement of the change in length with temperature or the rapid quenching from various temperatures in order to inhibit transformation with subsequent examination of the specimens, for example, either metallographically, by X-ray crystallography, or by hardness measurements. (See also Transformation Temperature).

Transformation Temperature (Metallurgical)

The temperature at which a change in phase occurs. The term is sometimes used to denote the limiting temperature of a transformation range. In order to distinguish between the critical points on heating and on cooling, those on heating are known as the Ac points (c chauffage or heating) and those on cooling as the Ar points (r refroidissement or cooling). The following symbols are used for iron and steel:

Ac cm. In hyper-eutectoid steel, the temperature at which the solution of cementite in austenite is completed during heating.

Ac1. The temperature at which austenite begins to form during heating. Ac3. The temperature at which transformation of ferrite to austenite is completed during heating.

Ac4. The temperature at which austenite transforms to delta ferrite during heating.

Ae1, Ae3, Ae cm, Ae4. The temperature of phase changes at equilibrium.

Ar cm. In hyper-eutectoid steel, the temperature at which precipitation of cementite starts during cooling.

Ar1. The temperature at which transformation of austenite to ferrite or to ferrite plus cementite is completed during cooling.

Ar3. The temperature at which austenite begins to transform to ferrite during cooling.

Ar4. The temperature at which delta ferrite transforms to austenite during cooling.

Ms. (or Ar' '.) The temperature at which transformation of austenite to martensite starts during cooling.

Mf. The temperature at which martensite formation finishes during cooling.

All these changes, except the martensite transformation, occur at lower temperatures during cooling than during heating, and depend on the rate of change of temperature. The martensite change is not reversible and is not affected by the rate of cooling.

Transition Joint, Triplate (Aluminium)
An explosively bonded bimetal flat bar that comprises a layer each of steel and marine-grade aluminium (alloy 5083) usually with an interlayer of pure aluminium. It is used for the on site welding of aluminium to steel, especially in shipyards and for offshore structures.
Transition Temperature (Metallurgical)

The temperature at which, in steel, a transition from ductile to brittle fracture takes place. It is commonly determined by making a series of Charpy impact tests at various temperatures; the transition temperature is usually taken as the point where 50% of the fracture surface shows cleavage. There are other methods of assessing the transition temperature, e.g., by bend tests, and each method gives a different value.

Transverse Test (Metallurgical)

A test usually applied to cast iron in which a bar is supported at its ends and loaded in the centre of the span until fracture occurs.

Twinning (Metallurgical)

Well-defined bands in crystals in which the orientation of the atoms in the crystal lattice is the mirror image of that of the remainder of the crystals. It may be a result of heat treatment following cold-work, as in the austenitic 18/8 stainless steels.


Ultimate Tensile Strength, Tensile Strength (Stainless Steel)
The maximum load, in tension, that a material can withstand before breaking. It is calculated as a breaking load for a standard cross section area and measured in Newtons per square mm (Nmm-2) or Mega-Pascals (MPa).
Ultrasonic Inspection (Metallurgical)

Owing to the piezo-electric effect certain crystals can be made to vibrate when influenced by an oscillating electric current. For ultrasonic inspection the crystal is made to vibrate at frequencies between 1/2 and 10 megacycles per second and when held against a piece of steel causes the vibrations to travel through the steel and be reflected back from the opposite side or from any intervening defects. The echoes are made visible on a cathode ray tube.

Ultrasonic Test (Aluminium)
A non-destructive test method using ultra high frequency sound waves to locate and assess the size of internal material defects.
Under-Ageing (Aluminium)
An artificial ageing treatment that fails to achieve maximum or optimum increase in mechanical properties/hardening. It is caused either by processing for an insufficient time or at too low a temperature.
Upper Critical Strain (Aluminium)
The minimum amount of cold work needed prior to annealing or solution treatment to produce a fine recrystallized equiaxed grain structure by eliminating the cold worked structure of elongated grains.


Vacancy (Metallurgical)

An empty atomic site within the crystal lattice. Vacancies can move about within the crystal under the application of stress.

Vickers' Diamond Hardness Tester (Metallurgical)

A small impression machine, suitable for testing metals of a high degree of hardness, finished parts and very thin sheets. The diamond impression is square. Angularity of pyramid 136 . The duration of the application of the load is controlled automatically and is always applied and removed in exactly the same manner. The machine may also be used with a ball indenter and thus give regular Brinell impressions. (See also Diamond Pyramid Hardness Test).


Water Staining (Aluminium)
A residue left on aluminium that has been wet and allowed to dry naturally. This is very difficult to remove and cannot be improved by polishing or anodising.
Weld Decay (Stainless Steel)
This describes the condition of a stainless steel that, having been welded or otherwise thermally processed, now has chromium carbide particles present in the grain boundaries. In this condition the steel becomes susceptible to corrosion as the matrix areas around the carbide are depleted in chromium and cannot form the protective oxide film.
Work Hardening (Copper)
The process of increasing the strength and hardness of a metal or alloy by cold deformation e.g. cold rolling, deep drawing, cold forging, hammering or cold extrusion. Work-hardening is sometimes referred to as 'cold work'.
Wrought Product (Aluminium)
A product made by hot, or hot and cold, plastic deformation by the rolling, extruding or forging of a cast product.
Wrought Product (Copper)
A product that has shaped, after casting, by either hot or cold deformation such as rolling, forging or extrusion.


X-Ray Crystallography (Metallurgical)

Max von Laue in 1921 showed that the planes of atoms in crystals act as a diffraction grating to X-rays, which are scattered by them and provide an accurate means of determining the details of the internal atomic structure. X-ray photographs of metals provide information which in many cases cannot be obtained by ordinary microscopic methods. The lines produced by each element, or phase, are characteristic, and their general pattern enables the crystalline structure to be identified. The scale of the pattern can be used to determine accurately the size of the unit cell and, therefore, the distance apart of the individual atoms; and from the relative intensity of the lines can be deduced the distribution throughout the unit cell of the various types of atoms in an alloy, or the degree of preferred orientation in the material. In addition, the sharpness of the lines provides information on both the state of strain and the grain size of the material.


Yield Point (Metallurgical)

The stress in a material at which there occurs a marked increase in strain without an increase in stress.

Yield Point, Yield Strength (Stainless Steel)
The tensile load above which a material ceases to behave elastically and will undergo permanent deformation. Measured in Newtons per square mm (Nmm-2) or Mega-Pascals (MPa).
Yield Stress (Metallurgical)

The lowest stress at which extension of the tensile test piece increases without increase in load. Practically it is determined by observing a fall of the testing lever and checked by a pair of dividers on the original gauge length. Many materials do not indicate a defined yield stress and in such cases the proof stress is used.

Young's Modulus (Metallurgical)

(Modulus of Elasticity). The ratio within the limits of elasticity of the stress to the corresponding strain, i.e., the stress divided by the resulting strain. Assuming a material to be perfectly elastic, the modulus of elasticity would be the stress applied to extend the test piece to double its length. For steel, Young's Modulus is of the order of 13,000 tons per square inch, and is only very slightly affected by composition and heat treatment.