Influence of Bending Stress on Microstructure of Tempered High Chromium Steel

Abstract

Transformation plasticity is an irreversible strain observed when metallurgical transformation occurs under small external stress lower than the yield stress of the weaker phase. This paper is devoted to an experimental analysis of that phenomenon in high chromium steels. The article deals with the results of the investigation of steel microstructure during bending at 520 °C temperature for 15 min, 30 min or 1 h. The tests were carried out using the specimens made from steel X12, X12Ф1 (GOST 5950-73) and 95X18 (GOST 5949-75), which were exposed to the bending stress (210 MPa or 450 MPa) during tempering. The methods of self-deformations, digital metallography, eddy currents and X-ray analysis were used. There was determined different influence of compression and stretch stress on the tempering transformations: the segregation of carbon and chromium from the solid solution, the dissociation of austenite, second martensitic transformation. There was indicated that these processes are also related to steel hardening temperature, which defines the structural and chemical composition of the steel.