Final answer:
Sheet metal processes are typically performed as cold working processes to shape metal at room temperature, reinforcing the material through strain hardening, without altering the metal's microstructure.
Step-by-step explanation:
The statement that sheet metal processes are usually performed as cold working processes is mostly true. Cold working refers to the process of shaping metal at room temperature, which increases the strength of the material through strain hardening. Examples of cold working include rolling, drawing, pressing, and bending metal sheets. These processes do not involve the metal being heated to its melting point, which is typical in hot working processes like smelting or the Bessemer process.
However, it's important to note that some sheet metal processes may involve heating but still stay below the recrystallization temperature of the metal, which can also be considered as cold working. Moreover, processes such as welding can require heat but are not used to shape the sheet metal itself, instead to join pieces together.
Situations where heat is applied, as in the Siemens-Martin process or forge welding, are separate from the typical cold working processes used to form sheet metal into the desired shapes without altering the metal's microstructure through the application of heat.