Hot deformation behavior and processing maps of BG801 bearing steel

Abstract

The hot deformation behavior and processing maps of BG801 bearing steel were studied by isothermal compression test on temperatures ranging from 900 to 1150 °C and different strain rates varying from 0.01 to 2 s−1. The results showed that unstable regions with flow localization and microcrack appear on microstructure at low temperature and high strain rates. The mixed grain and large grain were observed at relatively high temperatures (1090–1150 °C) and low strain rates (0.01–0.05 s−1). The true stress-strain curves exhibit serrated flow behavior when the strain rates of 1 s−1 and 2 s−1. It may be due to the interaction effect of dislocation and solute atoms atmosphere such as the high content of Co and Mo element. Using the dynamic material modeling (DMM), the 3D processing map was constructed using flow stress data to reveal the hot workability. It reveals that the two available hot processing parameter ranges were at a temperature of 1060–1150 °C with a strain rate of 0.1–0.63 s−1 and 970–1080 °C with a strain rate of 0.01–0.23 s−1. However, the carbides in BG801 steel will dissolve in the matrix at a temperature of 1090 °C leading to a grain growth sharply and a poor mechanical property. Combine with the size of grain size and production processing, the most optimized processing conditions for BG801 steel can be defined as the temperature of 970–1080 °C and strain rate of 0.01–0.23 s−1.