Development of Estimation Procedure of Contact Heat Transfer Coefficient at the Part-Tool Interface in Hot Stamping Process

Energy efficiency, a high level of passenger safety, and weight reduction of the vehicles still constitute the main functional elements for the design of modern car body structures. Toward this objective, the usage of advanced sheet-metal forming technologies like hot stamping of quenchable boron manganese steel is developing nowadays. Hot stamping is a combination of hot forming and simultaneously quenching and hardening of the blank. In this article, an experimental procedure developed to estimate the thermal conductance at the part-tool interface during a hot stamping procedure is presented. The tools set (punch and die) has been designed to form omega-shaped samples. This work represents the first stage of the procedure development where the standard experiment is a simple compressive load of sample in the bottom of the omega-shape die, considering the real hot-stamping conditions. Tests are carried out under different contact pressure values for two different blank materials (Usibor 1500P and a material B). The results show that the thermal conductivity increase contributes to the reduction of the thermal contact resistance and therefore to a more rapid cooling of the part.