Partial Tempering of Press Hardened Car Body Parts by a Premixed Oxygen-Methane Flame Jet

Due to the ambitious efforts in the field of automotive light weight construction the press hardening technology has gained in importance during the last years. The use of press hardened car body parts provides the opportunity of producing ultra high strength components with a tensile strength of more than 1500 MPa and low sheet thickness at the same time, that is why these parts are preferably used in the body in white for side-collision protection components. Because of the low ductility of these hot stamped parts several manufacturing approaches are researched with the focus on manufacturing hardened components with partial adjusted mechanical properties, in order to prevent an acute collapse of the part in the case of forcible deformation. Besides the directed deformation in the loading case, which marks a considerably enhancement of the passive safety, the integration of partial soft zones prevents the crack growth and spreading. The partial tempering of hot stamped parts can be implemented independent of the preceded process chain, steel grade and its coating. Besides the well-known tempering strategies by induction or laser, the use of a premixed oxygen-methane-flame jet offers, at the status of current basic research results, a significant potential regarding the rate of heating and the process stability. Therefore this manufacturing approach is absolutely an alternative to the well-known Tailored Properties strategies.