A Study of TIG Welds of Small Diameter STS 316L Tubes

Autogenous GTA circumferential butt joint welds were conducted on fluid distribution system components with diameters of 1/2 and 1/4 inches. The welds demonstrated excellent surface quality, although variations in microstructure were observed depending on the weld position. The 316L stainless steel base material, subjected to bright annealing and electrical polishing, exhibited a stable austenitic microstructure. The weld metal exhibited proper solidification structure and heat-affected zone (HAZ) formation, characterized by both columnar and equiaxed grain zones. In the HAZ, no significant microstructural changes were observed, which can be attributed to the effects of localized melting, rapid cooling, and the inherent properties of the austenitic microstructure. Thermal flow analysis was effectively utilized in the tube automatic welding process, playing a crucial role in predicting the weldability and overall quality of the welds. The weld metal consisted of columnar and equiaxed zones, with approximate widths of 2.3 mm and 1.8 mm, respectively. These results indicate that thermal flow analysis is an essential tool for predicting welding outcomes, including solidification structure and HAZ formation, which is vital for ensuring high-quality welds and predicting weld performance.