| 摘要 |
A medium-hard to hard thin steel sheet and a strip cut or stamped therefrom, both having an increased fatigue strength, are prepared by cold rolling a soft steel sheet, carburizing or carbo-nitriding the soft thinned sheet until a medium-hard to hard thin steel sheet is obtained and subjecting the resulting sheet or strip cut or stamped therefrom to a threepart heat treatment, which heat treatment involves first and second different austenizing operations, each followed by an identical two-step cooling operation, and a third lesser reheating and cooling operation. |
