Comparison of TIG and MAG Welding Methods for Stainless Steel Milk Tanker

Welded parts of the milk tanker are the most sensitive areas. The surface roughness, microstructure and mechanical properties of the welded joint affect the reliability of the tank. In this study, traditional methods, Metal active gas welding and Tungsten inert gas welding, were compared for AISI 304 stainless steel tanker body. The microstructure and phase contents of welded joints were examined and interpreted using optical microscope, scanning electron microscope, Schaeffler diagram, ferrite measurement and pseudo binary diagram. Hardness and tensile tests were performed for mechanical properties. Bacterial adhesion on the surface was determined by swab test and surface roughness measurements. It is concluded that Tungsten ınert gas welding is preferable compared to Metal active gas welding due to its more homogeneous / fine-grained structure, delta ferrite (8.7%) + austenitic phase structure, superior mechanical properties (660 MPa tensile strength), low surface roughness and low bacterial density (360 CFU/ml).