EXPERIMENTAL PLATFORMS AND DIE DESIGN FOR THE HOT STAMPING PROCESS
Fuh-Kuo Chen1; Tzu-Hao Hung1; Jeng-Shiun Cheng-Shun Lee1; Ping-Kun Lee2
1 National Taiwan University; 2 China Steel Corporation
doi:10.20906/CPS/CILAMCE2015-0876
Resumo
In order to develop a lightweight vehicle for carbon exhaustion reduction, the hot stamping process has been widely used in the automotive industry to manufacture structural parts. In the hot stamping process, the boron steel sheet is first heated up to about 930 ℃ with phase changed into austenite microstructure. The hot steel sheet is then formed and subsequently quenched in the stamping dies. In the quenching process, the hot steel sheet is cooled rapidly in the closed dies, and the microstructure is transferred from austenite to martensite as the cooling rate reaches the critical cooling rate. Because of the complex manufacture process which couples the mechanical-thermal-metallurgy mechanism, it is difficult to predict the forming defects and the final product strength. Therefore, applying the finite element analysis to facilitate the tooling design for the hot stamping process is required, and the effects of the process parameters on the formability and strength of the product parts can also be examined. In this paper, a finite element model for simulating the hot stamping process was constructed to investigate the influence of the process parameters on the product formability. In order to construct the hot stamping finite element model, the material properties of boron steel at various high temperatures with different strain rates were first obtained by the empirical approach with the use of the JMatPro software. An experimental apparatus for measuring the contact heat transfer coefficient and an experimental platform for the determination of friction coefficients at elevated temperatures were both developed in the present study. The values of the contact heat transfer coefficient and friction coefficient under various die contact forces and at different temperatures, which are required in the hot stamping finite element model, were then obtained from the experiments conducted with the developed experimental platforms. With the constructed finite element model, the die design for hot stamping of a U
Palavras-chave: hot stamping; experimental platform; finite element analysis; die design; friction; heat transfer coefficient