Heat Input Effect on Microstructure and Mechanical Properties in Shielded Metal Arc Welding of Dissimilar AISI ۳۱۶L/St-۳۷ Steel

Joining of stainless steels to carbon steels is one of the most widely used types of dissimilar joints. In this research, the microstructure and mechanical properties of dissimilar shielded metal arc welding of austenitic stainless steel AISI ۳۱۶L to carbon steel St-۳۷ is studied. This joining has made by E۳۱۶L electrode and three heat inputs of ۰.۷۲, ۰.۸۴ and ۱.۰ kJ/mm. The microstructure of the joints was characterized by optical and scanning electron microscopy. The mechanical properties of the joints were evaluated by tensile and microhardness tests. The solidification microstructure of the weld metals contained mainly austenite and some skeletal delta ferrite. There was an epitaxial growth at the interface of the weld metal with the AISI ۳۱۶L steel HAZ, and at the interface of the weld metal with the St-۳۷ HAZ, there is an un-etched narrow area which is suggested to have austenitic-martensitic structure. The results of hardness tests showed that the hardnessof the interface of the weld metal with the St-۳۷ steel was maximum which is attributed to the formation of the martensitic narrow band. The longitudinal tensile results showed that the increasing of the heat input decreaes the tensile strength and increases the elongation of the joints.

Keywords:

St-۳۷ steel , AISI ۳۱۶L stainless steel , Dissimilar Welding , Microstructure , tensile properties