Obtaining ultrafine spheroidized carbides by combining warm deformation with divorced eutectoid transformation in GCr15 bearing steel

Abstract

In this work, the ultrafine spheroidized carbides were obtained by combining warm deformation with the divorced eutectoid transformation (DET) in GCr15 bearing steel. The results show that the temperature range of DET is approximately 730°C to 700°C at a cooling rate of 0.05°C s −1 . It is also found that excellent spheroidized microstructure can be obtained and less deformation resistance can be generated when the deformation is carried out at 720°C with a strain rate of 0.5 s −1 . This result could be ascribed to the fact that deformation provides the driving force for transformation, dynamic recrystallization (DRX) and reduced dislocation density through the coordination of warm deformation and DET. This suggests that the deformation at the initial temperature is more favorable to the spheroidization than that at the intermediate temperature of DET. In addition, it is also proved that the warm rolling forming in the actual production line can shorten the spheroidization time from at least 10 h to 2 h and obtain ultrafine spheroidized carbides with the roundness close to 1. This research may provide a novel pathway to obtain good spheroidization effect with less energy conservation.

Rapid Spheroidizing Annealing via Combining Warm Deformation with Divorced Eutectoid Transformation in M50 Steel

“…Since the deformation can accelerate the DET process and refine the microstructure, some scholars combined DET with warm deformation (WD) to simultaneously realize the SA and shape forming. Our previous work indicated that the fine and uniform spheroidized carbides could be obtained by combining DET and WD in GCr15 steel [17,18]. In addition, Han et al [19,20] investigated the impact of deformation conditions on the spheroidizing process in GCr15, and the optimum deformation temperature was determined at 800 • C with a total reduction of 30%.…”