What is Cold Working? Results and Advantages explained
Cold working refers to the deliberate, plastic deformation of metals at temperatures notably below the recrystallization point of the respective material. The unintentionally induced and uncontrollable deformation is known as cold deformation. In the process, the strength of materials is determined by the increase of dislocations within the crystal structure. Upon movement, they can interfere to each other. In some cases, the material is heat treated to achieve better surface properties.
Cold-working operations are classified as squeezing, bending, shearing and drawing.
Results of Cold Working
The result of the procedure is called work hardening. This process describes the alternation and increase of dislocations within the crystal structure. Work hardening improves the mechanical properties of the workpiece, especially tensile strength, yield point, and hardness increases. At the same time, it can also become more brittle and the internal stress can increase.
Other side effects of cold working are the changes in electric conductivity as well as ferromagnetic properties. Electric conductivity can be negatively influenced, while ferromagnetic properties can improve. For instance, permanent magnetization can occur in steel, such as tool steel.
Work hardening is caused intentionally to increase hardness and strength of the material. In the steel industry, however, unintentional cold deforming can occur when materials are exposed to challenging conditions. Work hardening is most widely used for the processing of copper. Due to its ductile nature, copper can be cold worked and then work hardened, to increase hardness. This is often the case with too soft copper wires.
Distinction from Hot Working
Hot working is the intentional deformation of a material at a temperature above recrystallization point.
The differences between the two metal working processes are as follows:
- Temperature: The most obvious difference between warm and cold working is, of course, the temperature. While cold working operates at temperatures far below recrystallization temperature, how working operates at temperatures slightly above.
- Shape change: Due to the high temperature, materials can be made more malleable when it comes to hot working. Cold working, on the other hand, only allows small shape changes. However, the primary intent of cold working is the change of material property, not shape.
- Size tolerance: Size tolerances are smaller for materials that are cold worked, which is why they can be processed more precisely.
- Hardening: The main objective of cold working is the hardening of materials. In contrast, hardness is removed when it comes to hot working.
Advantages of the process
Advantages of the metalworking procedure include:
- The process requires no heating.
- Results are easy to reproduce.
- During the process, directional properties can be added to the metal.
- Contamination is minimized
- Depending on the plastic deformation, the improvement in the strength of a material can be similar with work hardening as with heat treatments.
The cold working process is almost wasteless. These metal savings are particularly important for expensive metal such as gold or copper. In addition to these raw savings, time is also saved during machining when cold forming. Therefore, production cycles are shorter when cold working, which is essential for large production runs.
FURTHER POSSIBILITIES FOR INCREASING HARDNESS
As a result of work hardening, massive deformation of the microstructure takes place. One consequence of this is a deterioration of the corrosion resistance. To avoid this, you can use the patented BORINOX® PROCESS FOR HARDENING STAINLESS STEEL. The treatment produces an extremely hard and wear-resistant outer coating. The corrosion properties of the material remain unaffected. If you have any questions, you can contact our materials specialists today for expert advice.