Prevention of weld decay in TIG-welded AISI 304 steel pipes

Abstract

Weld decay occurs due to chromium carbide precipitation at grain boundaries in the heat-affected zone (HAZ) during tungsten inert gas (TIG) welding of austenitic stainless steels. This issue is particularly significant concerning the welding of AISI 304 steels, commonly used in the food industry. Although this problem can be overcome with different methods, there are some restrictions. A novel technique for welding AISI 304 steel pipes is introduced to reduce weld decay and improve their mechanical properties. The use of this technique, which includes faster cooling after welding, significantly minimizes the time of precipitation of chromium carbide. Temperature measurements and microstructural analyses monitored precipitation, and the impact of the technique on the mechanical characteristics of AISI 304 steel pipes was assessed through hardness and hoop tensile tests. There was a 6% increase in hardness values observed in the HAZ region, as well as a 16.7% increase in maximum load and a 127.4% increase in elongation. The reduction in chromium carbide precipitation observed in the microstructural analysis was confirmed through the double-loop electropotentiokinetic reactivation test, specifically for assessing intergranular corrosion. With the novel method, there were a 25% increase in corrosion resistance in the HAZ and a 40% increase in the weld zone.