Narrow gap welding of 316L thick-section steel with cold metal transition pulsed arc swing

Narrow gap welding of 316L stainless steel thick plate was carried out using the cold metal transition pulsed wire-arc swing method. The effects of heat input, arc swing, and shielding mode on weld shaping and lack of fusion were investigated, and microstructure and tensile properties of welded joints were analyzed and characterized. The results indicate that arc swing amplitude was the primary factor affecting sidewall fusion. The tendency of undercut and incomplete fusion at the weld toe increased with the increase of wire feeding speed. Narrow gap weld with built-in shielding was easy to produce pores. The microstructure of welded joints was mostly represented by twin crystals in HAZ and columnar dendrites in the weld. Solidification sub-boundaries were produced between dendritic crystal clusters in the middle of the weld under high heat input, resulting in severe regional segregation and crystalline cracks that extended along subgrain boundaries. The microhardness of the weld and HAZ was greater than that of the base material. The tensile strength of welded joints was comparable to that of base material with good mechanical properties.