2060 – 09 – Varieties of Steel

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Not all steels are classified with a four-number system. Special types and varieties of steel have their own classification systems. Some examples include stainless steels and tool steels.

Chromium is found in a very high percentage of stainless steels. It lets the metal resist corrosion. AISI has a three-number system that identifies stainless steels. They are similar to alloy steels and that their numbering addresses a wide range of common alloy elements like chromium, manganese, and nickel.

Tool steels can be identified by their unique properties and their specific uses. Each grade of tool steel is given a corresponding letter that describes its normal uses. Tool steel grades add this letter to one or two numbers.