Chrome Vanadium Micro-alloy Axle Steel Grain Coarsening And Deformation Resistance,

Metal materials'deformation resistance, an elementary quatity of their plastic properties, is the capability to resist plastic deformation per unit cross-sectional area under certain deformation conditions. It is an important parameter of rolling force calculating, reasonable rolling process establishing and equipment checking. As a main cause of axle failure, austenitic grain coarsening should be paid enough attention during heat treatment.Cr-V micro-alloy axle steel, a new kind of axle steel, is developed by Panzhihua Iron & Steel Research Institute according to the axle technology of railway freight cars proposed by Ministry of Railways. Its mechanical properties are superior to those of axle steel LZ50. In this thesis, the grain coarsening experiment was designed based on its influence on axle failure. And the deformation resistance experiment was prepared to study whether heavy rolling reduction, able to eliminate center porosity, segregation and other defects of Cr-V micro-alloy axle steel casting billet, has negative effects on rolling equipment's normal operation. Appropriate coarsening temperature was determined through grain coarsening experiment, which is important to make reasonable heat treatment process and prevent performance degradation caused by grain coarsening during heat treatment. In this subject, the study on deformation resistance of micro-alloy axle steel, conducted on Gleeble-3500, has a reference significance for understanding the stress-strain curves'characteristics of new axle steel and optimizing onsite rolling process.The grain coarsening results show that austenite grain coarsening temperature of new axle steel is about 1150℃,200℃higher than ordinary steel. The stable second phase formed by Vanadium and other elements is the main reason for the increase of grain coarsening temperature.The deformation resistance results show that deformation resistance increases with the increase of deformation rate and extent, and decreases with the increase of deformation temperature; the deformation temperature and resistance follow a linear relationship in semi-logarithmic coordinate, so do the deformation rate and resistance in double logarithmic coordinate. Based on the characteristics of stress-strain curves, the effects of deformation temperature and extent on recrystallization were analyzed. It is found that recrystallization happens easily under high temperature and low deformation rate, but not under low temperature and high deformation rate. With mat lab software, multivariate non-linear simulation was carried out, and the mathematical model of Cr-V micro-alloy axle steel was obtained.A further study on deformation resistance was made among Cr-V micro-alloy axle steel,40SiMn2,30MnTiB and 42CrMo. The results show that under common rolling temperature and same deformation conditions, micro-alloy axle steel, whose deformation resistance is slightly lower than other steels', can completely meet the needs of rolling process and normal production.