Posted in | Steels

Nitriding Engineering Steel - EN40B (722M24)

EN40B (722M24) is a chromium-molybdenum based engineering steel grade from Thames Stockholders which is often delivered in the hardened and tempered condition. It benefits from good wear resistance and high fatigue strength. This can increase a tensile strength of up to 1075 N/mm². Nitriding yields a hard and wear resistant casing resulting in an engineering material which delivers good fatigue and shock resistance. The nitriding process is usually performed at a comparatively low temperature which brings about a scale-free surface with minimal distortion.

EN40B (722M24) can function in atmospheres of up to 500 °C before any loss in surface hardness is noticed. EN40B is delivered in the hardened and tempered ‘T’ condition. This nitriding steel also offers a good combination of toughness and ductility. When supplied in the ‘T’ condition, EN40B is ideal for applications necessitating high creep resistance and high tensile strength.  

EN40B (722M24) has become a widely used engineering material in industries such as automotive, textiles, and aerospace. It is also widely used by billet crankshaft manufacturers.

Benefits of Nitriding and Carburizing

Both the heat treatments are thermomechanical and performed at low temperatures which support minimal distortion. Nitriding boosts a high surface hardness with resistance to wear and galling and at the same time fatigue strength is also increased. Carburizing is a thermomechanical heat treatment which diffuses carbon in the surface of the steel forming a hard casing. This boosts the overall strength of the material and promotes better wear resistance. EN40B (722M24) is especially suited for both heat treatment types which results in a high wearing, high strength engineering steel.

Welding of EN40B (722M24) is not advisable but it is readily machinable using conventional machining techniques and in keeping with the machine manufacturer's instructions.


EN40B (722M24) is delivered in the ‘T’ condition. Examples of commercial application are listed below:

  • Crankshafts and gears
  • Spindles and pins
  • Gear wheels
  • Compressor discs
  • Cams, pinions, and gudgeon pins
  • Used in aerospace, automotive, textile, and general engineering applications

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