Rolled steels are obtained through the rolling process, which is the most basic process to obtain important characteristics of the steel that is going to be used.
Rolling is a mechanical process by which material’s thickness is reduced. The process consists in two opposing cylindrical rollers rotating on themselves and shaping the material as desired. The material, forced under tension, tends to shrink dramatically, i.e., to laminate. Rolling therefore generates elongation and widening of the material.
The process usually consists of several steps in which the rolls are placed close together; this is necessary in order to decrease the frictional forces that are generated during the processing, and which, if too high, compromise the outcome and waste too much energy.
How rolled steels are made?
There are different types of rolling:
- hot rolling
- cold rolling
- longitudinal rolling
- transverse rolling
- oblique rolling
There are usually several processing stages from the foundry product to the finished one, going through the first stage of roughing semi-finished product, an intermediate semi-finishing rolling, and last the finishing processing.
There are differences between hot and cold rolling. Cold rolling allows a thickness reduction of up to 70/80% of the starting thickness, increasing its strength, but with a greater labor and energy waste. However, you obtain more finished and precise parts.
Products made through cold rolling are:
- seamless pipes
- box sections
- rolled products in general
In hot rolling, the material undergoes less work hardening, thanks to the higher rate of the structure’s recrystallization, resulting in less labor and energy waste. Conversely, due to the presence of shrinkage phenomena, processing tends to be less precise and with a poor surface finish.
Examples of creations through hot rolling are:
- metal sheet strips
- railroad tracks
- small “I” beams
- seamless pipes
Rolled steels have different applications based on their properties when considering the manufacturing process.