Controlling Grain Sizes of 42CrMo Steel by Pre-Stress Hardening Grinding.

Yushi Wang,Shichao Xiu,Shengnan Zhang

doi:10.3390/ma12193124

Yushi Wang, Shichao Xiu + Show 1 more

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https://doi.org/10.3390/ma12193124

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Abstract

The dynamic recrystallization behavior of 42CrMo steel during the pre-stress hardening grinding (PSHG) process was investigated at temperatures ranging from 850–1150 °C and pre-stress from 0 MPa to 167 MPa. A coupled grain size model considering different grinding conditions was constructed to research the grinding process. Microstructure analyses showed that the hardening layer exhibits the typical features of dynamic recrystallization (DRX), and the evolution process of microstructure and grain size can be predicted properly by the model. The volume fraction of DRX grains increases with increasing pre-stress and grinding temperature. The critical condition for DRX grains occurring is that with a grinding depth of 150 µm, pre-stress is larger than 67 MPa, while most of the DRX grains occurred when pre-stress is larger than 100 MPa. Furthermore, the relationship between pre-stress and flow stress has been derived. The result shows that flow stress shows a linearly increasing trend, with the increase of pre-stress at the stage of lower strain.

Highlights

Pre-stress hardening grinding (PSHG) is a compound grinding technology which can harden a workpiece surface, and control residual stress [1]
The effects of pre-stress and grinding temperature on DRX behavior in 42CrMo steel were investigated though PSHG tests
The kinetic equations of the dynamically recrystallized process and the relationship between pre-stress and grain size were investigated based on a series of experimental and simulated results

Summary

Introduction

Pre-stress hardening grinding (PSHG) is a compound grinding technology which can harden a workpiece surface, and control residual stress [1]. The results of experiments indicated that the workpiece surface can obtain a hardening layer with excellent surface integrity after the PSHG process, and has an advantage over traditional grinding and heat treatment [2,3,4]. Microstructure evolution in the grinding deformation region, possibly under the influence of temperature, pre-stress and grinding force, creates tiny grains, which are called DRX grains. There have been varied theoretical, mathematical, and numerical methods to model DRX behavior, but most of them are conducted based on hot plastic deformation process. Much of the existing literature [5,6,7]

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