Numerical Prediction of Microstructure and Mechanical Properties During the Hot Stamping Process

Abstract

Numerical simulation and prediction of microstructures and mechanical properties of products is very important in product development of hot stamping parts. With this method we can easily design changes of hot stamping products’ properties prior to the manufacturing stage and this offers noticeable time and cost savings. In the present work, the hot stamping process of a U‐channel with 22MnB5 boron steels is simulated by using a coupled thermo‐mechanical FEM program. Then with the temperature evolution results obtained from the simulation, a model is applied to predict the microstructure evolution during the hot stamping process and mechanical properties of this U‐channel. The model consists of a phase transformation model and a mechanical properties prediction model. The phase transformation model which is proposed by Li et al is used to predict the austenite decomposition into ferrite, pearlite, and bainite during the cooling process. The diffusionless austenite‐martensite transformation is modeled using the Koistinen and Marburger relation. The mechanical properties prediction model is applied to predict the products’ hardness distribution. The numerical simulation is evaluated by comparing simulation results with the U‐channel hot stamping experiment. The numerically obtained temperature history is basically in agreement with corresponding experimental observation. The evaluation indicates the feasibility of this set of methods to be used to guide the optimization of hot stamping process parameters and the design of hot stamping tools.