Modeling of the Evolution of the Microstructure and the Hardness Penetration Depth for a Hypoeutectoid Steel Processed by Grind-Hardening

Grind-hardening processing is an emerging approach that combines the grinding and surface quenching process. During the process, the hardened layer—mainly martensite—is produced on the surface of the workpiece to achieve the purpose of surface strengthening. Above all, the surface temperature field of the hypoeutectoid-1045 steel workpiece was determined by finite element method for fully revealing the formation mechanism of the hardened layer. Further, the cellular automata approach was applied to dynamically simulate the transformation of both austenitization and martensitization from the initial microstructure. The hardness penetration depth was also predicted. Finally, a grind-hardening experiment was conducted to assess the theoretical study. Results showed that a combination of the finite element method and the cellular automata approach can effectively simulate the microstructure transformation of hardened layer. The microstructure and the hardness penetration depth were affected by the maximum grinding temperature and the heating rate. Research on the influence of grinding parameters showed that the hardness penetration depth increased as the depth of the wheel cut and feeding speed increased. Experiments revealed that the difference between predicted value and experimental value of the hardness penetration depth varied between 2.83% and 7.31%, which confirmed the effectiveness of the predicted model.

Effect of Annealing on Hardness Penetration of Caliber Rolled Mg-3Al-1Zn (AZ31) Alloy

–Mg-3Al-1Zn (AZ31) alloy was caliber rolled isothermally at the temperature of 300 °C to develop fine grains of 3.6 μm. Annealing was carried out at various times and temperatures. Along with microstructure, annealing affects the hardness and hardness penetration depth. The hardness penetration depth of caliber rolled bar during annealing at 300 to 450 °C was investigated for 5 to 60 minutes. The change in hardness penetration depth were analysed and the mechanisms involved were discussed.

Numerical Simulation of Temperature Field for Rack Grind-Hardening

Grind-hardening is a new integrated machining technology which utilizes grinding heat to quench the non-quenched steel directly. In this paper, the technology is applied in the process of rack form grinding. A comprehensive numerical model is developed to simulate the temperature distributions of the rack under the dry grind-hardening conditions with finite element method(FEM). The temperature dependency of the thermal properties, the triangular heat distribution of the heat flux, latent heat and the air convection are taken into account. The simulated hardness penetration depth(HPD) is deduced from the local temperature distribution, time history of workpiece according to martensitic phase transformation theory. This provides a reliable method for the proper selection of process parameters in order to produce enough heat at the contact zone, enabling the treatment of the rack.

Simulation and Prediction Studies on Harden Penetration Depth of AISI 5140 Alloy Steel in Surface Grinding

The grinding heat is utilized to induce martensitic phase transformation and strengthen the surface layer of AISI 5140 alloy steel by raising surface temperature higher than austenitic temperature and cooling quickly. The grinding temperature field is simulated by using finite element method (FEM). Then, the hardness penetration depth (HPD) is predicted from the temperature history and martensitic phase transformation conditions in surface grinding. The experiments of different grinding parameters are performed in surface grinding lathe. The hardness and hardness penetration depth of work piece surface layer are measured to validate the simulation and prediction. This method can be used to predict the HPD and optimize the grinding parameters forwardly.