Analysis of process limits for partial hot stamping with controlled pre-cooling by radiation exchange

Abstract

The increasing demands on part complexity and tailored properties in form of local strength and ductility cannot be achieved with conventionally manufactured hot stamped body components. To meet the requirements of safety-relevant body parts, partial hot stamping is increasingly used in the automotive industry. One approach to achieve tailored properties on hot stamped parts is based on controlled cooling of the blank prior to forming and quenching. The related furnace technology is based on a furnace chamber in which a cooled aluminum mask protects local areas of the blank from thermal radiation while simultaneously absorbing the blank’s own emitted radiation. The sheet thickness and utilized material significantly influence the controlled radiation exchange and present potential process limits. To analyse these lower process limits, blanks made of the materials 22MnB5 AS150 and 8MnB7 AS150 are partially pre-cooled and hot stamped with different sheet thicknesses. In addition, the process is simulated with AutoForm®R10 and validated by the obtained experimental results. The results show that the sheet thickness is a key influencing factor in the process and significantly affects the mechanical properties after partial hot stamping. Especially sheet thicknesses t0 of 2.25 mm can limit the process, as the effectiveness of the radiation exchange for controlled pre-cooling and phase transformation decreases.