PREDICTION OF WELD-ABILITY CHARACTERISTICS OF DUAL-PHASE STEEL HCT600X BY NUMERICAL SIMULATION

Dual-phase (DP) steel plates are characterized by very good absorption capacity, so they are used in the automotive industry for body deformation zone parts. They are attached to the frame of the car-body by welding. Laser welding of dual-phase steels is gaining increasing importance in the automotive industry. In the present paper, the possibility of predicting the strength and deformation characteristics of laser-welded HCT600X steel sheets was analyzed based on experiments and numerical simulations. Butt joints were formed by YLS-5000 laser in two variants, which differ by laser power input and welding speed. The HCT600X- HCT600X with welded joint was analyzed based on microstructure and mechanical tests. The tensile strength and hardness of the welded joints were greater than those of the base material (BM). The microstructure of the weld metal (fusion zone) consisted of martensite, austenite and bainite, in the heat-affected zone it consisted of a mixture of martensite, bainite, ferrite and residual austenite. In numerical simulation, the finite-element mesh was created by linear volume elements refined in the weld region, and the Gauss model of the surface heat source was applied when modelling laser welding. The results of numerical simulation of the microstructure and selected mechanical properties were correlated with the experimental results.