AISI 440B Martensitic Stainless Steel
AISI 440B (UNS S44003) — mid-carbon 440 grade, HRC 56–58. Compare with 440A and 440C for industrial knives and bearings.
AISI 440B (UNS S44003, DIN 1.4112) is the mid-carbon 440-grade martensitic stainless steel — hardened to HRC 56–58, with corrosion resistance between 440A and 440C. It is specified for industrial knives and bearings where 440A lacks wear life but 440C is over-specified for toughness.
Standard composition: C 0.75–0.95 %, Cr 16.0–18.0 %, Mo ≤ 0.75 %, Mn ≤ 1.00 %, Si ≤ 1.00 %, Ni ≤ 0.75 %, balance Fe
Hardness: Annealed HB 220–250; hardened HRC 56–59
Heat treatment: Austenitise 1,010–1,050 °C, oil or gas quench, temper 150–200 °C
Properties: The middle member of the 440 family. Slightly higher hardness than 440A, similar corrosion resistance.
Applications: Industrial cutting tools, bearings, valve components, surgical instruments.
Cross-reference: ≈ JIS SUS440B, DIN 1.4112, GB 8Cr17.
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