Investigation of combining the 304L and S355J2C+N materials with TIG welding in terms of microstructure and mechanical properties

Abstract

This study reports the investigation of the joining of S355J2C+N and 304L steels by the TIG welding method in terms of microstructure and mechanical properties. The effects of the microstructure of the heat-affected zones, the weld zone formed by the combination of two base metals with different superior properties, on the mechanical properties were investigated. In the optical examination, optical microscope (OM), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analyses were applied. Mechanical tests were carried out using tests such as microhardness (HV 0.1), bending, Charpy V-Notch impact, and tensile test. A microstructure was detected in the welded joint, which affects the mechanical properties. Grain size distribution in area fraction was determined from the EBSD maps of S355J2C+N steel, welded zone, heat affected zone (HAZ), and 304L. Average grain size of S355J2C+N base metal was 5.35 ± 1 μm, mean grain size of 304L base metal was 35 ± 5 μm, mean grain size for 304L HAZ was 41 ± 6 μm, and for S355J2C+N HAZ 5.47 ± 1 μm. Vickers microhardness values were measured as 222 ± 10 H V for 304 L base metal and 187 ± 10 HV for S355J2C+N base metal. The hardness of the weld center has the highest hardness and was determined as 302 ± 10 HV. In the tensile test, the highest tensile strength observed in the specimens extracted from the transverse direction is 534.88 ± 10 MPa. In the tensile test, a rupture occurred in S355J2C+N metal. In the bending test, the bending forces of 304L and S355J2C+N base metals were measured as 27.175 ± 4 kN and 28.480 ± 2 kN, respectively. The bending force of the transverse welded samples was 28.245 ± 2 kN, while the bending force of the longitudinal welded samples was 31.380 ± 2 kN. Weld efficiency was obtained as 106%. Tungsten inert arc welding provided good properties such as strength, sealing, and toughness in the combination of stainless and carbon steel, and this welding method was determined to be suitable for the successful joining of these two dissimilar metals.