Weldability process and post-weld mechanical and microstructural analysis of different steels

Dissimilar materials with different properties can be joined by various welding methods under different boundary conditions. Gas metal arc welding (GMAW) is one of the most widely used welding methods among the melting-based welding processes. GMAW has many advantages in terms of applicability and extensively used in the metal manufacturing industry. In practice joining dissimilar steel sheets frequently conducted however weld quality strongly dependent to boundary conditions during the welding process. Joining dissimilar alloy steels by GMAW finds applications various industries such as manufacturing, aviation, defense and automotive. Therefore, in this study 10 mm thick dissimilar steel sheets are joined by GMAW under various boundary conditions. Post weld mechanical and microstructural behaviors are investigated in detail. For the process in experimental design three level variables of parameters i.e., welding speed, welding current and welding voltage were used for the Taguchi L9 orthogonal array where tensile, impact and hardness tests were conducted, and microstructural properties investigated in detail. Frequently used dissimilar St37 and St52 steel sheet materials with a thickness of 10 mm were joined with 'V' butt weld and SG-2 electrode wire. In terms of mechanical strength, the contribution of each variable was evaluated in detail and optimum welding parameters were clarified with gray relational analysis as 35 V, 330 A and 250 mm/min. Tempering processes with three level were applied to the optimum materials to increase the mechanical strength. Then, the effect of tempering process on mechanical properties and microstructure was investigated in detail.