The annealing method and bearing steel has excellent cold workability and machinability

摘要

PROBLEM TO BE SOLVED: To provide a method for annealing a high-carbon chromium bearing steel in which the grain size of carbides is made high, the number of carbides is made small and hardness is regulated to a degree suitable for machinability and cold working by one time heating pattern without requiring a special heating furnace and to produce a high-carbon chromium bearing steel by this method. ;SOLUTION: A high-carbon chromium bearing steel contg., by weight, 0.8 to 1.2% C and 0.9 to 2.0% Cr is rapidly heated to the temp. range of 700 to 730°C, is thereafter gradually heated from this temp. range to 760°C at a heating rate of ≤7°C/hr, is furthermore rapidly heated from 760 to 790°C and is held to 790°C. Then, this steel is cooled from 790°C to the temp. range of 740 to 720°C at a rate less than that in air cooling, is furthermore gradually cooled from this temp. range to the temp. range of below the end of the Ar₁ transformation part at ≤10°C/hr and is thereafter cooled at a rate less than that in air cooling to obtain the high-carbon chromium bearing steel in which the number of carbides in the structure is regulated to ≤10.0×10⁵pieces/mm² and hardness to 90 HRB and excellent in machinability and cold workability.;COPYRIGHT: (C)1997,JPO