In metallurgy, cold forming or cold working is any metalworking process in which metal is shaped below its recrystallization temperature, usually at the ambient temperature. Such processes are contrasted with hot working techniques like hot rolling, forging, welding, etc. The same or similar terms are used in glassmaking for the equivalents; for example cut glass is made by "cold work", cutting or grinding a formed object.
Cold forming techniques are usually classified into four major groups: squeezing, bending, drawing, and shearing. They generally have the advantage of being simpler to carry out than hot working techniques.
Unlike hot working, cold working causes the crystal grains and inclusions to distort following the flow of the metal; which may cause work hardening and anisotropic material properties. Work hardening makes the metal harder, stiffer, and stronger, but less plastic, and may cause cracks of the piece.
The possible uses of cold forming are extremely varied, including large flat sheets, complex folded shapes, metal tubes, screw heads and threads, riveted joints, and much more.
The following is a list of cold forming processes:
Squeezing:
Rolling
Swaging
Extrusion
Forging
Sizing
Riveting
Staking
Coining
Peening
Burnishing
Heading
Hubbing
Thread rolling
Bending:
Angle bending
Roll bending
Draw and compression
Roll forming
Seaming
Flanging
Straightening
Shearing
Sheet metal shear-cutting
Slitting
Blanking
Piercing
Lancing
Perforating
Notching
Nibbling
Shaving
Trimming
Cutoff
Dinking
Drawing
Wire drawing
Tube drawing
Metal spinning
Embossing
Stretch forming
Sheet metal drawing
Ironing
Superplastic forming
Advantages of cold working over hot working include:
No heating required
Better surface finish
Superior dimensional control
Better reproducibility and interchangeability
Directional properties can be imparted into the metal
Contamination problems are minimized
Depending on the material and extent of deformation, the increase in strength due to work hardening may be comparable to that of heat treating.