Effect of cooling system in hot stamping process

Abstract

Hot stamping process is used to produce automotive components that give a high strength-to-weight ratio, therefore it reduces fuel consumption and improves crashworthiness. Hot stamping is a non-isothermal process where forming and quenching takes place simultaneously. One of the major factors affecting the mechanical properties of components is the cooling rate which is controlled by the cooling systems. Direct cooling and indirect cooling (cooling channel) are the two cooling methods used in this process. In direct cooling, water is used as the cooling medium that gives higher cooling rate, however it induces large residual stress in the final component. In indirect cooling, cooling channels are used in die and punch for cooling purpose. In indirect cooling system residual stresses are not developed, but thinning occurs in wall region of the blank due to inhomogeneous contact between blank and die. Therefore, in this work, a new method has been proposed with the combination of direct and indirect cooling. In this combined cooling method, different coolant like spray water, air mist and compressed air was used for direct cooling. Simulation of the proposed approach was done by using PAMSTAMP software. The effect of the combined cooling system with various cooling medium was investigated and it was found that the air mist cooling with indirect cooling system resulted in 7% improvement in thickness distribution and 20% improvement in temperature distribution compared to the conventional method.

Development of rapid die cooling technology using the Groove Pressing method in hot stamping process

“…Maeno et al improved the cooling rate of the component sidewall by filling the lower die with water, which allowed water to flow to the sidewall during forming [8]. Narayanasamy et al studied a cooling system that sprays water onto the surface of the component through flow paths connected to the cooling channel [9]. Eiichi et al prevented local wall-thinning by spraying water or air on the sidewall of the sheet before forming and improved the cooling rate of the component [10].…”