Influence of Beam Power and Traverse Speed in Fibre Laser welding of Dual phase steel (590) on Depth of weld zone penetration, Microstructure and Hardness

Abstract

The influence of heat input on microstructure, microhardness, and mechanical properties of welded structures of DP 590 (Commercially known as DP 600 grade) grade steel of 1.6 mm thickness sheet has been investigated. The investigation was carried out by using Nd: YAG fibre laser source at a beam power of 1.5 kW and 3.0 kW at a traverse speed of 2 m/min, 4 m/min, and 6 m/min in bead on plate weld configuration. Except at lower beam power and lower traverse speed, at all other combinations of beam power and traverse speed a complete weld penetration has been observed. The weld zone microstructures have been transformed into predominantly martensitic phase due to rapid solidification. The width of the Heat Affected Zone and Weld Zone decreased as the heat input decreased. Hardness values of weld zone has increased to 350 -380 HV from 180-200 HV due to formation of martensite.