MECHANICAL AND FATIGUE PROPERTIES OF 17Cr-15Mn-0.4N-1.2Ni, HIGH-MN, N AUSTENITIC STAINLESS STEEL STRENGTHENED BY GRAIN REFINING

摘要

Work-hardened high-Mn,N austenitic stainless steel is often used as a high strength material. The strength of this steel can be increased further by grain refining. In this work, mechanical and high cycle fatigue properties of the high-Mn,N austenitic stainless steel strengthened by grain refining was investigated for cold rolled and aged conditions. Also, the effect of the carbon content was examined by comparing specimens with 0.05 percent and 0.13 percent carbon. (low-C and high-C, respectively.) As a result, the strength of the steel was increased by grain refining for both carbon contents. The grain refinement obviously leads to higher fatigue-limit. The strength was increased by aging but the fatigue property was not, and the difference in the carbon content seemed to have little influence on the fatigue property. In the cold rolled condition, the ratio of (fatigue limit)/(tensile strength) of the grain refined specimens was approximately 20 percent higher than that of the normal-grain. This fact clearly shows that grain refining improves fatigue property. According to the observation of specimen surface before fracturing, it was confirmed that microcracks were initiated at the slip bands that had been formed during cold rolling. On the other hand, the initiation of such microcracks was inhibited in the grain-refined specimens.