from the conferences organized by TANGER Ltd.
Low carbon high-strength steel sheets are in scope of the material research mainly used as structural materials for automotive industry. Cold forming is the most prominent technology of achieving the final shape of the parts made of thin sheet. This requires sufficient plasticity of the material so that the forming procedure can be performed without sheet fracture. High strength steels are attractive due to possibility of weight saving; however, their higher strength comes with a reduction of plasticity. Especially widely used dual and complex phase steels, providing an exceptional combination of plasticity and strength, are not performing well during forming due to their susceptibility to an edge fracture. It emerged that this feature is caused by alternation of hard martensite and soft ferrite in their structure causing crack propagation by separation of these phases. This experiment is aimed at development of a high-strength low-carbon steel sheet of a homogeneous low-tempered martensite microstructure with a tensile strength in an interval of 1000-1200 MPa. This strength is comparable with the highest grades of dual and complex-phase steels. However, the homogeneous microstructure gives an advantage in the formability, which can be crucial factor for the cold forming operation. Influence of different concentration of Si and Mo was examined by tensile test and hole expansion test for 0.8 mm thick sheets.
Keywords: High strength steel, martensite, formability, hole expansion test© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.