Stainless Steel, Martensitic1.4021 (420) Bar

A martensitic machining bar with machinability enhanced through the addition of sulphur.

As with most other free-machining stainless steels the improvement in machinability is achieved by addition of sulphur which forms manganese sulphide inclusions; this sulphur addition also lowers the corrosion resistance, weldability and formability to below that of its non-free machining equivalent Grade 410.

Martensitic stainless steels are optimised for high hardness, and other properties are to some degree compromised. Fabrication must be by methods that allow for poor weldability and usually also allow for a final harden and temper heat treatment. Corrosion resistance is lower than the common austenitic grades, and their useful operating temperature range is limited by their loss of ductility at sub-zero temperatures and loss of strength by over-tempering at elevated temperatures.

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Related Specifications

1.4021 is similar, but may not be a direct equivalent to:

  • 420
  • UNS42000
  • 1.4021, 1.4024, 1.4028, 1.4029, 1.4030, 1.4034


Chemical Composition


  • Valve parts
  • Pump shafts
  • Automatic screw machined parts
  • Motor shafts
  • Washing machine components
  • Bolts and nuts
  • Studs
  • Gears
  • Shear blades
  • Cutlery (blades)
  • Surgical instruments


  • Good corrosion resistance similar to 410 plus increased strength and hardness
  • It is magnetic in both the annealed and hardened conditions
  • Maximum corrosion resistance is attained only in the fully hardened condition
  • It is never used in the annealed condition

Additional Information


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