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

Abstract

Abstract 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 influencing sidewall fusion. The tendency to develop undercutting and incomplete fusion at the weld toes increased with increasing wire feed rate. Narrow gap welds are prone to porosity with built-in shielding. Microstructure of welded joints was mostly represented by twin crystals in HAZ and columnar dendrites in the weld. Under high heat input, solidification sub-boundaries form between dendritic crystal clusters in the middle of weld, resulting in severe regional segregation and crystalline cracks that extend along sub-grain boundaries. The microhardness of weld and HAZ was greater than that of base material. The tensile strength of welded joints was comparable to that of base material. Defect-free tensile specimens fractured in the base material and welded joints with good mechanical properties were obtained.