SUS440C Stainless Steel: Premium Hardened Stainless Steel Grade

Key Characteristics

High Hardness & Strength: Achieves very high hardness (up to 60 HRC) and tensile strength after proper heat treatment, making it extremely durable.

Wear Resistance: Excellent resistance to abrasive wear, suitable for high-friction parts.

Corrosion Resistance: Offers good corrosion resistance for a martensitic steel, especially when tempered below 400°C, but not as high as austenitic grades.

Composition: High carbon (0.95-1.20%) and chromium (16-18%) content.

Common Applications

Ball bearings and races

Cutting tools (knives, surgical instruments)

Valve parts and seats

Molds and dies

Heat Treatment & Machinability

Hardening: Heat to 1010-1070°C and quench (oil for heavy sections).

Tempering: Temper at low temperatures (150-400°C) for maximum hardness; avoid 425-565°C range for better impact/corrosion resistance.

Machinability: Relatively poor when hardened; often machined in the annealed state or with carbide tools.