4.2.3 Martensitic Grades

Martensitic stainless steels usually contain a maximum of 14% chromium, except types 440A and 440B, which contain 16% to 18% chromium. Carbon is added in sufficient amounts to promote hardening. Other elements, when present, are usually restricted to 2% or 3%. They exhibit excellent strength, and, unlike most other stainless grades, they are magnetic. Martensitic stainless steels are hardened and tempered using processes similar to those used for as alloy steels. Typical tempering temperatures range from 540 to 620^°C (1000 to 1150^°F).

Commonly used martensitic forging grades include:

 

SAE No	AMS No	Percent Composition
		C		Cr	Mo	Ni	S1	Si
403	A4732	0.2		12
410	5613	0.12		12				1
416	5610			13	0.6		0.15
420	5621	0.2		13
431	A4732	0.2		16		2
440A	5631	0.7		17	0.7
440C	5630	1.1		17	0.7

¹Sulphur reduces forgeability
²ASTM specification

SAE grades include several others that have special purposes and, while not commonly forged, are just as forgeable as these listed grades.