Effect of Pulse Width in Pulsed Nd:YAG Dissimilar Laser Welding of Austenitic Stainless Steel (304 L) and Carbon Steel (st37)

Abstract

In the recent development of the automobile, power generation and petrochemical industries the application of dissimilar welds are gaining importance. In the present work, pulsed Nd:YAG laser welding of austenitic stainless steel (304 L) and carbon steel (st37) of 1.4 mm thickness for butt joint configuration have been investigated for automotive industries. The effect of pulsed width on weld bead width (top bead width (TBW) and bottom bead width (BBW), depth of penetration (DOP) and heat affected zone (HAZ) and fusion zone area have been studied. The microstructure characterization of the fusion zone, HAZ and base metals have been compared at varying pulse width using optical microscope. DOP decreases with increase in pulse width beyond 5 ms and fusion zone area decreases with increase in pulse width. Bottom weld bead width decreases with increase in pulse width and HAZ width of st37 side decreases with increase in pulse width. The mechanical properties such as microhardness and tensile strength of the welded joints at varying pulse width have been investigated. Ultimate tensile strength of all the welded joint at different pulse width was equal to the base metal st37 and fracture location was away from the fusion zone. The average microhardness of the fusion zone decreases with increase in pulse width due to the presence of martensite at low pulse width.