New Approaches for Improved Efficiency and Flexibility in Process Chains of Press Hardening

Abstract

In the last decade, press hardening has become a fully established technology in both science and industry for the production of ultra-high-strength structural components, especially in the automotive industry. Beside the improvement of car performance such as safety and lightweight design, the production process is also one focus of trends in technology development in the field of press hardening. This paper presents an overview about alternative approaches for optimized process chains of press hardening, also including pre- and post-processing in addition to the actual forming and quenching process. Investigations on direct contact heating technology show new prospects regarding fast and flexible austenitization of blanks at compact device dimensions. By applying high speed impact cutting (HSIC) for trimming of press hardened parts, an alternative technology is available to substitute the slow and energy-intensive laser trimming in today’s press hardening lines. Combined with stroke-to-stroke control based on measuring of process-relevant parameters, a readjustment of the production line is possible in order to produce each part with individual, optimal process parameters to realize zero defect production of property-graded press hardened components with constant high part quality. Significant research in the field of press hardening was carried out at Fraunhofer Institute for Machine Tools and Forming Technology IWU, in the hot forming model process chain which enables the running of experiments under conditions similar to industrial scales. All practical tests were prepared by design of experiments and assisted by thermo-mechanical FE simulations.

Flexibility in metal forming

“…In addition, various heating methods such as induction heating and contact heating are employed on the hot stamping in order to heat the sheet metal effectively [137]. Landgrebe et al [101]. developed a contact-heating device of sheet metal for hot stamping In the case of hot stamping, Kolleck et al [87] employed induction heating which brings in the benefit of high heating rates in order to avoid grain coarsening while heating in a short time.…”

Influence of surface pressure and tool materials on contact heating of aluminum

“…Direct contact heating is a relatively new approach (suggested in [14]) with high potential to overcome these limitations. In this technology, the contact plates (typically made of metal or ceramics) that are heated by a heat source (e. g. induction coils [14], gas burners [15], cartridge heaters [16]) serve as energy storage and transfer the heat to the workpiece via thermal conduction. Compared to furnace heating, contact heating excels due to extremely high heating rates, which significantly reduces heating time [17].…”