Autogenous Nd:YAG laser welding of 6nm thick dissimilar steels

In the power generation, nuclear, chemical and transportation industries, there is a need for joints involving dissimilar material combinations. Laser welding has proved to be advantageous for welding dissimilar material combinations, due to its characteristics such as narrow fusion zone, low heat input, concentrated heat intensity and the ability to align the beam to a specific position with respect to the joint line. In this study, procedures have been developed for the autogenous Nd:YAG laser welding of 6 mm thick carbon-manganese steel to stainless steel and carbon-manganese steel to duplex stainless steel. The welds have been characterised by optical microscopy and mechanical testing. Sound welds have been produced and no undercut or suck-back has been observed in the 400 mm length welds. Distributed delta ferrite has been observed in the weld microstructure of carbon-manganese steel to stainless steel, while ferrite in the form of needles was more predominant in the carbon-manganese steel to duplex stainless steel weld microstructure. The hardness distribution map showed regions with maximum hardness values of up to HV350. High integrity welds in both combinations that meet the mechanical property requirements have been produced.