Combination of different standard stainless steel and plain carbon steel pairs by friction stir welding method, examination of mechanical properties and microstructures

In this study, microstructure and mechanical properties of welded regions of different quality austenitic stainless steels (AISI 304 and AISI 316) and plain carbon steels (AISI 1010, AISI 1030, AISI 1050 and AISI 1070) combined with friction stir welding were investigated and the best welding pair was determined. Firstly, AISI 304 austenitic stainless steel and AISI 304 austenitic stainless steel were combined with different rotation speeds and travel speeds and the optimum welding parameters were determined by considering the mechanical and microstructure properties. Then, using the obtained optimum values, austenitic stainless steel and plain carbon steels were welded together with the friction stir welding. Likewise, AISI 316-AISI 316 austenitic stainless steels were combined with friction stir welding using different rotation speeds and travel speeds. As in AISI 304, optimum welding parameters were determined by looking at the mechanical and microstructure properties. The microstructure and mechanical properties of AISI 304-AISI 10X0 and AISI 316-AISI 10X0 pairs of steels, which are welded by optimum parameters, were investigated. Interfacial compatibility of these materials, which are combined under suitable welding conditions, was examined, and the best welding pairs were obtained. Friction stir welding of plain carbon steel and stainless steel were performed by shaping into a special form of hard metal tungsten carbide pin connected with collette. After the welding process, in order to examine the mechanical properties of joint parts, tensile test, notch impact test, micro hardness, shear test were performed. The microstructures of the welded region were analyzed by using XRD (X-ray diffractometry) to determine phase shifts and internal stresses, OM (optical microscope) for etch coarse microscopy, SEM (scanning electron microscopy) for morphological surface investigations. As a result of mechanical properties and microstructure investigations after friction mixing welding, within AISI 304-AISI 10X0 steel pairs were found to have the best strength and microstructure values of AISI 304-AISI 1050 steel pair. Likewise within AISI 316-AISI 10X0 steel pairs were found to have the best strength and microstructure values of AISI 316-AISI 1010 steel pair.