Laser Beam Welding of Advanced High-Strength Steels (Dual Phase Steels)

Abstract

Presently, Dual Phase (DP) steels are highly accepted steels by the automotive manufacturers as structural materials. Microstructural features of these steels resulted special properties. Welding is an inevitable in automobile manufacturing. Nd:YAG fiber laser welding was used to produce Beads on plate on Dual Phase steel of 780 grade. Welding Beads were produced by varying the heat input from 17 to 24 J/mm2. Complete Depth of Penetration of weld beads was observed at all heat inputs. With increase in the heat input, weld zone dimensions were increased. Fusion zone was transformed by liquid to solid transformations, up on cooling. Heat Affected Zone was formed by solid–solid phase transformation, and the proportion of Martensite was decreased with increasing the distance from Fusion Boundary. The microhardness of the fusion zone was 370 ± 10 HV0.5 and that of the base materials was 270 ± 19 HV0.5. The increase in hardness in the fusion zone was due to the phase transformation in this zone.