Effect of Argon Shielding-Gas Flow Rate on the Quality and Mechanical Performance of TIG-Welded AISI 316L Joints

Abstract

Gas tungsten arc welding (GTAW), commonly known as TIG welding, is one of the most reliable techniques for joining stainless steel, producing clean joints with few defects under a gas-shielded arc. AISI 316L austenitic stainless steel, prized for its corrosion resistance and mechanical strength, is used extensively across the petrochemical, food-processing, and aerospace sectors, which makes the quality of its welded joints a matter of practical importance. This work examines how argon shielding-gas flow rate affects the mechanical performance of manually TIG-welded 316L joints. Six flow rates were tested 5, 10, 15, 17, 19, and 22 L/min with all other welding parameters held fixed, and each condition was assessed through visual inspection, liquid-penetrant testing, radiography, tensile testing, bend testing, hardness testing, and metallographic examination. A flow rate of 10 L/min gave the best overall performance among the six conditions tested, with the highest tensile strength recorded (616.1 MPa); the lowest flow rate produced lack of root fusion, while the two highest flow rates produced undercut and excess root penetration, respectively, along with a marked drop in tensile strength. Hardness, bend strength, and microstructure showed little variation across the flow rates studied, whereas tensile strength proved by far the most sensitive property to changes in flow rate. Each reported value is the average of three replicate welds, demonstrating that a flow rate of 10 L/min is best treated as a strong candidate for overall mechanical performance among the conditions tested.