PRECIPITATION HARDENING STAINLESS STEELS

The precipitation hardening stainless steels are iron–chromium–nickel alloys that develop high strength and toughness through additions of Al, Ti, Nb, V, and/or N, which form precipitates during an aging heat treatment. The base microstructures of precipitation hardening stainless steels can be either martensitic or austenitic depending upon composition and processing. Some selected grades are listed

below:

600 Austenitic grade with Mo, Al, Ti, V, and B added

630 Martensitic grade with Cu and Nb added

631 Austenitic grade with Al added

633 Austenitic grade with Mo and N added

635 Martensitic grade with Al and Ti added

The compositional ranges of the precipitation hardening stainless steels are listed in the aforementioned ASM table.

OTHER STAINLESS STEELS.

There are many stainless steels that do not fall within the AISI classification system. These steels have proprietary compositions and trade names. Details of many of these steels can be found in Chapter 2 and in the Bibliography at the end of this chapter.

Tool Steels. Tool steels are alloy steels that are used to cut or machine other materials. Tool steels contain various levels of Cr, Ni, Mo, W, V, and Co. The categories of tool steels are:

M series Molybdenum high-speed steels

T series Tungsten high-speed steels

Cr series Chromium hot-work steels

H series Molybdenum hot-work steels

A series Air-hardening medium-alloy cold-work steels

D series High-carbon high-chromium cold-work steels

O series Oil-hardening cold-work steels

S series Shock-resistant steels

L series Low-alloy special-purpose tool steels

P series Low-carbon mold steels

W series Water-hardening tool steels

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