Classification of steels by application

Stainless steels:

AISI has established three-digit system for the stainless steels:

2XX series – chromium-nickel-manganese austenitic stainless steels;

3XX series – chromium-nickel austenitic stainless steels;

4XX series – chromium martensitic stainless steels or ferritic stainless steels;

5XX series – low chromium martensitic stainless steels;

Tool and die steels:

Designation system of one-letter in combination with a number is accepted for tool steels.

The letter means:

W - Water hardened plain carbon tool steels;

O - Oil hardening cold work alloy steels;

A - Air hardening cold work alloy steels;

D -Diffused hardening cold work alloy steels;

S – Shock resistant low carbon tool steels;

T – High speed tungsten tool steels;

M - High speed molybdenum tool steels;

H – Hot work tool steels;

P – Plastic mold tool steels.