Microstructures and bulging formability of laser welded tailored blanks for high strength steel with unequal thickness

Tailor welded blanks (TWB) of laser weld is adopted to weld high strength steel sheets SAPH440 with 1.8 mm thickness and DP600 with 2.2 mm thickness.The microstructures and microhardness of the welded joint for TWB are studied,and the cupping tests are carried out to study the bulging formability of TWB,which is compared with that of the original sheet blanks.The results show that the microstructures of the joint are acicular ferrite and lath martensite,the microhardness of the joint is higher than that of the base metal.And the cupping experimental values of TWB are lower than that of the original sheet blanks.Eventually,the weld location has some influence on the bulging formability of TWB,the bigger the proportion of the thin blank is,the better the bulging formability of TWB is,and the weld will move to the side of the thick blank during bulging formation.