Effects of Welding Speed on Microstructure and Mechanical Properties of CO2 Laser Welded Dissimilar Butt Joints between Low Carbon Steel and Austenitic Stainless Steel

Abstract

ABSTRACT Austenitic stainless steel (AISI316) and low carbon steel (AISI1018) sheet joints are a popular dissimilar metal combination used in power generation applications. The 4 kW CO2 laser welding has recently been used for the production of dissimilar metal joints with appropriate mechanical and metallurgical properties. In this study, the influence of laser welding process parameters of dissimilar weld joints was investigated with the varying laser powers, welding speeds and constant shielding gas flow rate. The variation of mechanical properties and microstructures of the dissimilar weld zone and heat-affected zones were investigated and resulted. The microstructure of the weld zone was predominantly fine columnar dendrites along with carbides were observed. The stainless steel heat-affected zone consists of coarser austenite grains with twin structure and little carbide precipitation. The low carbon steel heat-affected zone results, the mixed structure of acicular ferrite, pearlite, bainite, and martensite structure along with enriched iron. The chemical composition of the weld zone and phase structure of the dissimilar weld zone was examined through chromium and nickel equivalents. The higher hardness value was obtained in the weld zone and heat-affected zone of low carbon steel.