Study Of Process Parameters Optimization And Numerical Simulation During Internal Grind-hardening

Grind-hardening is a process that can be use the generated heat for partially heating the workpiece in order to increase its surface hardness,and use the self-cooling of the workpiece matrix for achieving surface quenching in the grinding process.This technology combines the grinding processing with the surface heat treatment,which is in line with the increasingly promoted concept of process integration and green manufacturing in engineering work.Based on the single-factor and orthogonal internal grinding experiment with "the radial feeding+the circumferential feeding",this paper discusses the influence of the depth of cut αp,the workpiece feeding speed vw and the grinding speed vs on the macro-morphology,microstructure,micro-hardness distribution,hardness penetration depth(HPD)and arc length of the softening zone(ALSZ)of a steel GCr15 component.Orthogonal experiments was conducted to analyze the arc length of softening zone and hardness penetration depth of the steel GCr15 in internal grinding.The optimal grinding parameters combination of the minimum arc length of softening zone and maximum hardness penetration depth has been obtained.A regression model of the arc length of softening zone has been established,applying ANSYS to establish the internal grind-hardening temperaturoe field and simulate the hardness penetration depth of the internal surface.The main innovations and contributions are as follows:(1)The workpiece is divided into the cutting-in-cutting-out zone and the circumferential feed zone along the circumferential direction.The cutting-in-cutting-out zone is divided into the circumferential cutting-out zone,radial cutting-in zone and circumferential cutting-in zone,from left to right in different zones of the circumferential surface layer.(2)There is a certain length of tempering softening zone in the cutting-in-cutting-out zone of the workpiece,due to the influence of grinding heat during the circumferential cutting-in and cutting-out of the grinding wheel.The softening zone is mainly composed of the radial cutting-in zone,the circumferential cutting-in transition zone and the circumferential cutting-out transition zone of the grinding wheel.The structure of softening zone in the radial cutting-in zone is mainly tempered sorbite or tempered troostite.With increasing the depth of cut,the circumferential micro-hardness curve of the softening zone gradually transitions from the "hard-soft-hard"U-shaped feature to the "hard-soft-hard-soft-hard" W-shaped feature.The effect of the workpiece feeding speed and grinding speed on the macroscopic morphology of the grind-hardening workpiece and the circumferential micro-hardness distribution of the cutting-in-cutting-out zone were insignificant.(3)An increase of the depth of cut,workpiece feeding,speed or grinding speed,leads to a shorter arc length of the softening zone.With increasing the depth of cut and workpiece feeding or decreasing the grinding speed,the hardness penetration depth increased.The arc length of the softening zone and hardness penetration depth were affected primarily by the effect of the depth of cut.The optimal grinding parameters combination is the depth of cut ap=0.3 mm,workpiece feeding speed vw=0.2 m/min and grinding speed vs=30 m/min.The regression model of the arc length of the softening zone can be expressed as:y=18.835-31.617x1-16.033x2.(4)The simulation results of the temperature field distribution of the starting point of the circumferential cutting-in zone,circumferential feed zone and the terminal point of the circumferential cutting-out zone were basically consistent with the microstructure formation temperature.Simultaneously,the simulation of the hardness penetration depth of the internal surface is carried on to verify the accuracy of the model.This research work provides a foundation of experiments and simulation for the engineering application of internal grind-hardening.This paper was supported by the Science and Technology Project of Fujian Province(Study of Process Parameters Optimization and Numerical Simulation during Internal Grind-hardening,Grant no:2018J01489).