Welding is a manufacturing process where the union of two or more pieces of a material, (usually metals or thermoplastics), usually achieved through coalescence (fusion), in which the pieces are welded by melting, It is possible to add a material of contribution (metal or plastic), which, when melted, forms a puddle of molten material between the pieces to be welded (the soldering bath) and, when cooled, becomes a fixed union to which it is called cord.