Effect of Laser Pulse Duration on Tensile and Electrochemical Behavior of Laser-Welded Dual-Phase Steel

Abstract

Dual-phase steels having excellent combination of strength and ductility are extensively used in automotive industry for the manufacture of car body structure involving welding and joining significantly. The present study assesses the tensile and electrochemical behavior of butt welded dual-phase 780 steel grade produced using pulsed Nd:YAG laser with varying pulse duration in the range of 1.5 to 3.6 ms. Numerical modeling has been done to know the temperature profile during welding. Systematic analysis of welded joint bead profile, microstructure, tensile test results, and fractographic features revealed the effect of pulse duration on the fusion zone, heat-affected zone softening, and also allowed the estimation of critical size of the soft zone near to the failure location under tensile loading. With an increase in pulse duration, welded joint concavity reduced from 35 to 6% which improved the mechanical performance of the welded joints. Welded joints with higher pulse duration enhanced the resistance against galvanic and pitting corrosion due to the formation of the oxide layer, finer martensitic microstructure in the fusion zone and a smaller amount of weld defects.