SOME ASPECTS OF POSSIBLE BEARING STEEL MICROSTRUCTURE MODIFICATIONS

Microstructural changes and mechanical properties with Mn-Cr steel (0. 65 % C) under effect of cold rolling, rapid austenitizing, immediate o il quenching and low temperature tempering were investigated. Compared to properties of conventionally treated standard Cr-C bearing steel, higher ultimate strength, increased fracture toughness and enhanced ro lling contact fatigue life were observed at comparable yield stress le vels. The increased stress relaxation ability of the lath martensite m atrix, and the absence of transformation microcracks, both due to the reduced carbon content in steel and also in gamma-solid solution, are the main reasons of the properties' improvement. The double transfer o f substructural defects from cold worked ferrite to austenite and back into martensite, and the austenite heterogeneity control, both enable d by rapid austenitizing followed by quenching, was the key for obtain ing the effects mentioned.