Surface Integrity And Experimental Research On Grind-hardening Process Of 42CrMo Steel

The grind-hardening is a new combined machining technology that integrates grinding and surface quenching, which has advantages of turning grinding heat from the harm into a benefit and realizing green machining. Because of its wide prospect of engineering application, the research and technology application of grind-hardening has been attached great importance to manufacturing engineering experts and scholars at home and abroad.Based on the grind-hardening processing of 42 CrMo steel, the influences of grinding parameters on grinding force and the distribution of grind-hardening temperature field were studied. The effects of grinding conditions on the surface integrity of grind-hardening processing were systematically discussed, which further revealed the formation and the change law of residual stress and burr. The main research work is as follows:(1) By constructing the test system of grind-hardening processing, the grinding force and grinding temperature during the grind-hardening process were measured online, and the influences of grinding parameters on grinding force and the distribution and change of temperature field in the grinding process were studied.(2) The formation and change law of grind-hardening processing hardened layer of42 CrMo steel and residual stress were researched. The Box-Behnken response surface method and the single factor method were carried out to analyze the influences of grinding parameters, grinding methods and original structure on the micro-hardness and depth of grind-hardened layer. The predictive regression equation of grind-hardened layer depth was established, which can find out the main factors and the secondary factors affecting the grind-hardened layer depth, and further reveal the relationship between hardened layer depth and grinding parameters. Finally, the properties and its distribution state of residual stress in hardened layer and along with depth were systematically researched, and the relationship between residual stress in the grind-hardened layer with the depth and the structure of hardened layer.(3) The variation and formation mechanism of burr(edge) in grind-hardening processwere studied. To optimize grind-hardening processing parameters of 42 CrMo steel, the Box-Behnken response surface methodology was used to establish the predictive regression model of two-side direction burr in grind-hardening process. In addition, the change law of burr height size and burr root thickness size in the grinding direction were analyzed.According to the effects of grinding parameters on two-side direction burr, the main methods to control the burr size were given.The research is a significant part of the project of the National Natural Science Foundation of China(No.51075192). This study further enriches the grind-hardening theory,and set a theoretical and experimental foundation for improving the practicality and reliability of grind-hardening machining technology.