Investigation of microstructure and mechanical properties of gas metal arc welded aisi 304 austenitic stainless steel plates

Austenitic stainless steels exhibit very good properties such as very good formability even at low temperatures, good mechanical properties and high corrosion resistance. Austenitic steels are the grades which are produced the most in quantity among all stainless steels and AISI 304 is the most widely used grade among the austenitic stainless steel grades. They are used widely in several industries such as chemistry and petro-chemistry industries, food processing industry, machinery and manufacturing industry, medical and dental equipments and kitchenware. However, several difficulties such as carbide precipitation along the grain boundaries in heat affected zone, and hot cracking and formation of brittle sigma phase in the fusion zone are encountered in fusion joining of these steels. High heat inputs involved in arc welding may even increase the occurrence of these problems. Thus, successful joining of these alloys using conventional fusion welding methods is rather important. This study aims at investigating the influence of heat input on microstructural evolution in the weld region and the mechanical properties of the welded joints in gas metal arc welding of AISI 304 austenitic stainless steel plates. For this purpose, AISI 304 austenitic steel plates with a thickness of 5 mm were joined using different heat input values. The microstructures in the weld region and mechanical properties of the welded plates were investigated by detailed optical microscopy investigations, micro-hardness measurements, tensile and bending tests. Thus, it was attempted to determine the optimum heat input required for obtaining sound welded joints in gas metal arc welding of these steels.