This monograph presents the outcome of our investigation that was conducted to correlate process variables in shielded metal-arc welding and post weld heat treatment on some mechanical properties of low carbon steel weld. From the results obtained we observed that welding current and post weld heat treatment temperatures influences the tensile strength, impact strength and hardness of welded low carbon steel. As the welding current increases the hardness and strength increases but impact strength reduces, while hardness and strength continuously reduces but impact strength increases as post weld heat treatment temperatures increases. This outcome will help to eliminate much of the “guess work” often employed by welders to specify welding parameters and help them to properly select them for a given task to provide a good weld quality. With this finding welder can now adequately select welding currents and post weld heat treatment temperatures for low carbon steel that will yield quality weld in shielded metal-arc welding without guess work.