The surface layer work hardening of cold-rolled 40Cr

To reveal the work hardening behaviour during 40Cr cold-rolled forming, cold-rolled simulation experiment was adopted. The relationships among the dislocation density, the half width of X-ray diffraction peaks and the surface hardness of cold-rolled parts, were investigated. To accomplish this, a microscopic mathematical model of the surface layer hardness based on dislocation density was established. After the 40Cr cold-rolled experiments were conducted, the structure of the specimens was characterised using an X-ray diffractometer, and the surface layer microhardness was measured with an MH-3 microhardness tester. Based on the established mathematical model, the surface layer hardness values of the cold-rolled specimens were calculated and the influence of the different cold-rolled conditions was analysed. Based on the X-ray diffraction spectra under various cold-rolled conditions, the surface layer work hardening behaviour was microscopically analysed.