INVESTIGATION OF HARDNESS PROFILES AND MICROSTRUCTURE CHANGE IN THE WELD NUGGET AND HAZ OF RESISTANCE SPOT WELDED LOW CARBON STEEL
Metallurgical changes in weld nugget and heat affected zone (HAZ) during resistance spot welding of low carbon steel sheets is very important factor that determines final mechanical properties of welded joint. Thus, effect of spot welding parameters (current, welding time, holding time) on the mechanical and microstructural properties of weld nugget and heat affected zone were analysed in this work. Hardness was measured using Vickers method, while results were presented in the form of hardness distribution over a cross section of weld nugget and HAZ, for different welding parameters. It was observed that hardness in heat affected zone and melting zone is very dependent on welding parameters. Also, tensile tests showed that strength of the joint is very susceptible to welding parameters and thickness of the parent material. Microstructural changes in the weld nugget zone and heat affected zone were examined and analysed for some specific samples.