AISI M50 High-Speed Steel for Bearings
AISI M50 (UNS T11350) — Cr-V-Mo HSS for bearings, HRC 64–66, low distortion. Compare with M2 for high-RPM cutting tools.
AISI M50 (UNS T11350) is a Cr-V-Mo high-speed steel originally developed for aerospace bearings — hardened to HRC 64–66 with good dimensional stability during heat treatment. Used in precision bearings and high-RPM cutting tools where M2 wear life is sufficient but M2 distortion at hardening is a problem.
Standard composition: C 0.78–0.88 %, Cr 4.00–4.50 %, Mo 4.00–4.50 %, W ≤ 0.20 %, V 0.80–1.25 %, Mn ≤ 0.40 %, Si ≤ 0.50 %, balance Fe
Hardness: Annealed HB 248–269; hardened HRC 62–65
Heat treatment: Austenitise 1,090–1,120 °C, oil quench, double temper 510–530 °C
Properties: A low-W HSS designed for bearings. Very high dimensional stability and compressive strength. Lower hot hardness than M2/M42 but excellent for high-load, high-temperature applications where dimensional stability matters.
Applications: Slitter blades for fine film, bearings for high-temperature applications, machine-tool spindles.
Cross-reference: ≈ DIN 1.3551 (close).
See also.
