Which process involves heating a piece of metal prior to changing its shape?

The process that involves heating a piece of metal prior to changing its shape is forging. Forging typically requires the metal to be heated to a malleable state, making it easier to manipulate and shape through various methods such as hammering or pressing. This heating enhances the metal's ductility, allowing it to be shaped without cracking or breaking.

When metal is subjected to the forging process, its internal structure improves due to the deformation that occurs while it is heated and worked. This results in a product that has a finely aligned grain structure, leading to superior strength and durability compared to other shaping processes. The application of heat in forging is crucial to facilitate these benefits, distinguishing it from processes like welding, casting, and stamping, which do not primarily focus on the heating aspect to change the metal's shape.