Before making rolled aluminum, a rolling mill must decide if it will hot or cold work the stock. This decision largely depends on the material properties desired for a specific roll.
If the mill decides to cold work the aluminum, the material will not undergo a heating process before rolling. Cold working changes the microstructure of the aluminum to become harder and stronger. Some advantages of the cold working process include:
- The ability to maintain dimensional accuracy.
- There’s no need to wait for the aluminum to reach a specific temperature.
- Oxidation does not occur during the cold working process, leading to better surface finishes.
- The strength and wear properties of the aluminum increase.
The opposite of cold working is hot working. Hot working is when the mill decides to heat the aluminum before beginning the rolling process. The exact temperature in the hot working process will vary among alloys. For example, the hot working temperature of 3004 aluminum is between 260 degrees Celsius to 483 degrees C or 500 degrees Fahrenheit to 900 degrees F. The hot rolling process prevents materials from hardening and the aluminum remains ductile. Some additional advantages of hot working include:
- The size and shape of the aluminum are easily changeable.
- Workers can minimize stresses and other defects.
- The mechanical, physical and chemical properties of aluminum can undergo improvements.
- The hot working process is economical, fast and reliable.