Distortion Analysis of Air Hardened Deep Drawn Parts of the Air-Hardenable Steel LH800

Requirements of the automotive industry result in the development of new sheet materials that combine good plasticity to form complex geometry parts as well as high strength properties. One of such materials is the low-carbon air-hardenable steel LH800. Technological processing of such sheets includes the operations of deep drawing, cutting, air quenching and welding. The initial annealed ferritic microstructure features an elongation at fracture of about 30%. Due to air quenching tensile strength can be increased up to 1000 MPa. However, implementation of carriage elements is limited due to distortion caused by the mentioned treatments. To evaluate distortion caused by air quenching investigations by means of axis-symmetric deep drawn cups and its segments were carried out. The geometry of the selected parts before and after air quenching was measured optically. Distortion at various parts positions was analyzed and quantified. Furthermore, a mathematical model was developed and implemented into the finite-elements software ABAQUS to predict distortion of sheet metal products caused by thermal treatment.