Cold Bending Properties of Three Kinds of 22MnB5 Steel Hot Stamping Parts

The bending samples with various width and non-standard tensile samples were cut from three kinds of 22MnB5 steel hot stamping parts (domestic A pillar, impute B pillar and door beam made from impute steel plate), the width of bending sample should be more than 20 times thickness. Bending test was carried out according to German standard VDA 238-100, and cold bending properties of various hot stamping parts were compared. In addition, tensile test was carried out, and tensile fracture morphology and bending fracture morphology were observed. The results show that the microstructure of three kinds of hot stamping parts all were lath martensite, their tensile properties were about the same. Tensile fracture can divide three domain: fiber area, radical area and shear lip. The radical zone is infrequent strip and band structure. The measured bending angles of three hot stamping parts were about the same and less than 60°, this related to their same microstructure. The morphology of fracture for bending samples was dimple structure with different morphology.