Stainless Steel, Precipitation HardeningAMS5643/04/22 (17-4) Bar

Martensitic precipitation hardening stainless steel with 17% chromium and 4% nickel.

The most well known precipitation hardening steel is 17-4. The name comes from the additions 17% chromium and 4% nickel. It also contains 4% copper and 0.3% niobium. 17-4 is also known as stainless steel grade 630.

Precipitation hardening stainless steels are chromium and nickel containing steels that provide an optimum combination of the properties of martensitic and austenitic grades. Like martensitic grades, they are known for their ability to gain high strength through heat treatment and they also have the corrosion resistance of austenitic stainless steel.

The high tensile strengths of precipitation hardening stainless steels come after a heat treatment process that leads to precipitation hardening of a martensitic or austenitic matrix. Hardening is achieved through the addition of one or more of the elements copper, aluminium, titanium, niobium, and molybdenum.

The advantage of precipitation hardening steels is that they can be supplied in a “solution treated” condition, which is readily machinable. After machining or another fabrication method, a single, low temperature heat treatment can be applied to increase the strength of the steel. This is known as ageing or age-hardening. As it is carried out at low temperature, the component undergoes no distortion.

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Product FormConditionImperial SizesMetric Sizes
Round BarCondition A38" - 12"45mm
Round BarCondition H1150D38" - 12"45mm
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Related Specifications

This is similar to, but may not be a direct equivalent:

  • 17/4 PH
  • UNS S17400
  • Grade 630
  • 1.4548


Chemical Composition


Due to the high strength of precipitation hardening stainless steels, most applications are in aerospace and other high-technology industries.

Applications include:

  • Gears
  • Valves and other engine components
  • High strength shafts
  • Turbine blades
  • Moulding dies
  • Nuclear waste casks
  • Intricate machined parts
  • Medical instruments
  • Paper mill equipment


  • Excellent corrosion resistance
  • High strength & hardness
  • Readily machined and fabricated
  • Good mechanical properties at high temperatures
  • High yield strength

Additional Information


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