There are various reasons for carrying out heat treating. Some procedures make the metal soft, while others increase hardness. They may also affect the electrical and heat conductivity of these materials.
Some heat treatment methods relieve stresses induced in earlier cold working processes. Others develop desirable chemical properties to metals. Choosing the perfect method really comes down to the type of metal and the required properties.
In some cases, a metal part may go through several heat treatment procedures. For instance, some super alloys used in the aircraft manufacturing industry may undergo up to six different heat treating steps to optimise it for the application.