Forging welding was the first form of welding and for many centuries the only one in general use. Briefly, the process consists of heating the metal in a forge to a plastic condition and then uniting it by pressure
Hardening is a process of heating and cool steel to increase its hardness and tensile strength, to reduce its ductility, and to obtain a fine grain structure. The procedure includes heating the metal above its critical point of temperature, followed by rapid cooling. As steel is heated, a physical and chemical change takes place between the iron and carbon
Annealing: The primary purpose of annealing is to soften hard steel so that it may be machined or cold-worked. This is usually accomplished by heating the steel to slightly above the critical temperature to form austenite, holding it there until the temperature of the piece is uniform throughout, and then cooling at a slowly controlled rate so that the temperature of the surface and that of the center of the piece are approximately the same.