고주파 열처리된 0.2wt.%C-Cr 선조질강의 피로 특성에 관한 연구

A Study on the Fatigue Properties of the Pre Heat-Treated 0.2wt.%C-Cr Steel by Induction Heating

The material studied in this paper that is an alloy of 0.2 percent carbon and a few Cr was heat-treated by high frequency induction coil. The heat treatment processes is quenching and tempering at about 980℃ and 510℃ for 15 second respectively. During the heat treatment, the carbides were precipitated in the tempered martensite matrix. As a result, high tensile and yield strength was achieved because of small Cr carbide precipitates. Also at room temperature, high cycle fatigue(HCF) test carried out for this steel at 20Hz and R=0.1. The mechanism of fatigue crack initiation from surface and propagation to subsurface was investigated. A few large precipitate with a size lower than the critical threshold leads to a surface initiation crack. It seems that fine microstructure and carbides improve resistance to crack propagation.