Potentials of single stage induction heating for press hardening of steel blanks

Abstract

Due to growing challenges regarding crash-performance, CO2 emission as well as increasing demand for lightweight construction, hot metal forming of car body parts has risen to one of the most important technologies for saving weight of a car body. During hot forming shaped blanks of steel are heated and austenitized at around 950°C and subsequently quenched for martensitic formation. Currently the heating is realized in roller hearth furnaces which allow only a slow heating and, therefore, a limited production rate. Induction heating of the blanks offers a big potential to increase the production rate dramatically and also to improve the energy efficiency. Only due to the fact, that the heated blanks typically are already pre-shaped with holes and cut-outs induction heating becomes a very complex task. The paper compares different possible induction heating methods (longitudinal heating, transverse flux heating, single stage induction heating, hybrid heating by induction and conventional heating). For the case of single stage induction heating a detailed numerical and experimental investigation in the frame of a recently completed research project is presented.