Tool steels are varieties of steel, that because of their hardness, grindability, ability to hold an edge, and wear resistance, are excellent for tool making. These tool steels are often used in applications such as stamping dies, metal cutting tools, shear blades, punches, etc.

There are six general categories of tool steel:

  • Water hardening – also referred to as W-type steel because they are water quenched.
  • Cold-work – further divided into these groups:
    • Oil hardening – also referred to as O-type steel because they are oil quenched.
    • Medium alloy air hardening – also referred to as A-type steel because they are air hardened.
    • High carbon-chromium¬†– also referred to as D-type steel, typically containing 12% chromium and more than 1.5% carbon.
  • Shock resisting – also referred to as S-type steel because of their ability to withstand shock.
  • High speed – also referred to as T-type and M-type steels, ¬†including CPM powder metal, are used in high-speed applications.
  • Hot-working ¬†– also referred to as H-type steel because they are able to resist softening and heat checking at high heat for extended periods of time.
  • Special purpose – include these and others:
    • Plastic mold steels – also referred to as P-type steel
    • Low alloy special purpose – also referred to as L-type steel