Microstructure and properties of weld by high-speed tandem TIG welding of thin 304 stainless steel plate

Compared with the welding of stainless steel at the conventional welding speed, the microstructures and properties of joint can be affected by the solidification process, which would be changed in high-speed welding. The butt welds with good weld appearance were obtained by tandem tungsten inert gas (tandem TIG) welding 304 stainless steel plate of 1.2 mm thickness at the welding speed of 3.0 m/min. And compared with the conventional single TIG welded joint, the properties of welds by tandem TIG welding were studied by nonstandard tensile specimens, and the microstructures were analyzed. The experimental results showed that the equiaxed grains formed in the weld center, the directions of dendrite grains on both side of weld center were not the opposite in tandem TIG weld, and the tensile strength and elongation of tandem TIG weld were slightly lower than that of base metal. Compared with the conventional single TIG welding, the average diameter of the grain in heat affected zone of tandem TIG joint decreased by 10.3 %, but the average diameter of the grain in weld center increased by 12.9 %, the tensile strength and elongation of tandem TIG weld increased by 4.3 % and 23.2 %, respectively. The micro-hardness in weld center of tandem TIG welded joint were slightly higher than that of base metal.