SUS440B

Alloy Steel

SUS440B

(JIS G4303). Nominal values—confirm mill certificate.

Chemical Composition (%)

C0.75
SI1
MN1
P0.04
S0.03
CR16
MO0.75

Mechanical Properties

Hardness(hardened):≥56 HRC

Chinese Standard

JIS G4303 SUS440B

Available Forms

Bar,Plate

Uses

Martensitic stainless steel combining moderate corrosion resistance with high strength and hardness after heat treatment. Used for cutlery, surgical instruments, turbine blades, valves, pumps, fasteners and bearings in mildly corrosive environments.

Heat Treatment

Annealing/quench from 980–1050 °C (oil or air) then temper 150–650 °C; lower temper gives higher hardness, higher temper improves toughness.

Precautions

Preheat and post-weld heat treat to avoid hydrogen cracking; soft anneal before heavy machining. Lower corrosion resistance than austenitic grades — not for strong chlorides.

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