Overview of welding processes, study of welding arc characteristics, metal transfer during arc welding, heat flow during welding, gas-metal and slag-metal reactions, weldpool solidification, effect of welding process parameters on the macro- and micro-structure of weld metal. Thermal cycles in the heat affected zone. Phase transformations in the weld metal and the heat affected zone. Phenomena of hot-cracking and cold cracking. Residual stresses and distortion during and after welding. Application of above principles to welding of carbon and alloy steels, cast rions, stainless steels, aluminium and titanium alloys. Fatigue and fracture of weldments.