Metal forming is the process of fashioning or shaping metal objects using mechanical means. It works upon the scientific principle of plastic deformation, which allows the physical shape of the material to remain permanently deformed without adding to or taking away from the material and without changing its mass. Cold forming is one of the most common metal forming processes.
What is Cold Forming?
In contrast to hot forming, which involves heating metal to a molten state before applying mechanical processes for shaping, cold forming mechanically reshapes material at room temperature or slightly above room temperature. Cold rolling is the primary process used for cold forming metal. It involves introducing strip or coil stock between two rollers that apply constant pressure to compress the metal into a thinner sheet.
Altering hardness and other material properties is possible by varying the amount of strain applied to the workpiece. The primary benefits produced by cold rolling include a better surface finish and improved dimensional accuracy.
What is the Cold Rolling Process?
Before cold rolling can take place, metal that has gone through hot rolling must go through the process of pickling. The pickling process is necessary to remove the scale caused by hot rolling, which interferes with the process of cold rolling.
To be successful, cold rolling deformation must occur at temperatures below the metal’s recrystallization temperature. This is necessary to increase the yield strength and hardness of the metal. Cold rolling introduces defects into the material’s crystalline structure, reducing the grain size of the metal or micro-restructuring of the crystals to produce Hall-Petch hardening.
Rolling mills include gauges used to determine the thickness of the metal after it passes through the rollers. These gauges determine whether the material has reached the desired thickness or requires further processing. There are two types of mills used in cold forming:
- Reversing mills will push the metal back and forth through the rollers by reversing material feed after each pass. Reducing the distance between the rollers and gauges on each pass reduces thickness until the workpiece reaches the desired thickness and is ejected from the rollers.
- Multi-strand mills have three to six rollers in a series. As the workpiece passes along the line, each roller further reduces its thickness by a specified percentage until the piece reaches the desired thickness.
Each pass of the workpiece, whether in a reversing or multi-strand mill, produces a 50% to 90% reduction of material thickness. Due to friction, the temperature of the material increases up to 250° C on each pass, making it necessary to apply water or oil to keep it cool.
Finished thicknesses of cold-rolled metal range from 0.010 to 0.188 inches, making rolled metal ideal for manufacturing and assembling products that require lightweight strength and hardness. At these thicknesses, tolerance becomes a critical factor in cold roll finishing, requiring cross-sectional tolerances of ±0.003 inches, angular dimensional tolerances at ±0.25° or tighter, and straightness and twist accuracies of less than ±0.015 inches.
Premier Products of Racine Premier Cold Rolling Manufacturers
Obtaining the necessary strength, hardness, and dimensional tolerances to meet the unique specifications of various applications is a critical component in cold forming. Premier Products of Racine is a premier cold rolling manufacturer located in Southeastern Wisconsin near the shore of Lake Michigan.
The experience and expertise we’ve developed since our founding in 1999 have positioned us as leaders in providing custom cold-formed products for a variety of industries. We commonly provide cold-rolled materials for use in office furniture, barbeque grills, appliances, and tankers.