The effects of preheating, post weld heating and arc welding parameters on the microstructures and mechanical properties of SAILMA 300 HI steel welds in comparison to normal welds were experimentally determined. The results show that when preheating and/or Post Weld heat temperature increases the yield strength, ultimate tensile strength, and hardness of welds slightly decreases, on the other hand percentage elongation, percentage reduction in area and toughness increases as compared to normal welds.The combined condition of pre- and post- heating of welds showed best improvement in...