Experimental analysis of TMT bar and cold-drawn plain carbon steel spot welded mesh

In this study, three TMT bars and one cold-drawn bar with diameters of 6 mm, 8 mm, 10 mm, and 6 mm, respectively, are spot welded. The hardness values of these welded samples are tested at three locations, i.e., base, welded zone, and heat-affected zone (HAZ). The mechanical properties of different areas of the welded samples change after welding. In all cases, the weld zone hardness increases the most, and in the HAZ, the hardness increases more than in the base metal zone. In the base area, more ferrite is present, resulting in lower hardness than pearlite. Moreover, Widmanstätten structure or Thomas structure is present in HAZ for TMT bars, which is likely near the fusion edge and tends to increase the hardness (212–238 HV) than that of the base metal (185–193 HV). The welded zone consists of a columnar dendritic structure of fused metal with more pearlite than ferrite, causing higher hardness (266–267 HV) than base metal and HAZ. On the contrary, a higher hardness for cold-drawn steel with more hardness variation is observed between weld (250–308 HV), HAZ (230–245 HV), and base (200–225 HV) than those of TMT bars. The tensile strength is predicted using forecast analysis in MS Excel based on the available literature data. Among the four experimental bars, 6 mm TMT and 6 mm cold-drawn wire show excellent weld joint characteristics with efficiencies of 97% and 77%, respectively regarding shear strength, good weld penetration, and hardness variation.