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Hot stamping is a high-temperature forming operation in which the blank is heated to austenitization temperature, and subsequent forming and quenching operations are done simultaneously. In the current research, forming limits were determined using a thickness gradient-based criterion. For this purpose, the tensile and plane strain mode of deformation were considered. The study was carried out in a wide range of temperatures, viz. 750 °C,800 °C and 850 °C at a constant strain rate of 0.01/s. The experiments were carried out in the thermomechanical simulator (Gleeble-3800), and subsequent measurement of thinning evolution for all the deformed specimens were carried out. It was observed that with the increase in temperature, thickness reduction was less and the distribution of thickness was uniform in tensile specimens and at the point of necking thickness gradient ratio is below 0.92 at various temperatures.

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.

Hot stamping is a high temperature and high strain rate deformation process, which is widely used in automotive industries because of the advantages associated with the process like higher formability, no spring back, higher specific strength to weight ratio etc. When strain rate increases, the formability of materials decreases but in some conditions reversal behavior was also observed, therefore in this work, the focus is to find the effect of strain rate on thickness distribution, thickness gradient evolution and formability of 22MnB5 Steel. To capture the effect of strain rate, a wide range of high-temperature tensile tests were conducted in the thermomechanical simulator (Gleeble-3800) for different strain rates (0.01, 0.1, 1/s) under uniaxial and plain strain conditions. It is found that formability of 22MnB5 steel increases with increase in strain rate in the drawing region.

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