Forge welding is the first kind of welding that ever was used . The process is commonly used for welding dissimilar materials , such as the welding of aluminum with steel in ship hulls or compound plates . Other solid-state welding processes include friction welding ( including friction stir welding ) , electromagnetic pulse welding , co-extrusion welding , cold welding , diffusion welding , exothermic welding , high frequency welding , hot pressure welding , induction welding , and roll welding .