Hot rolling vs. cold rolling

The lamination process is carried out by two methods – hot or cold. And it is done by forcing the material (steel) through the gap between two cylinders. The two types of lamination, hot and cold, differ in three major aspects: lamination temperature, thickness and material properties.

Types of lamination – descriptions and differences

Hot rolling is carried out above the recrystallization temperature of the steel. While cold rolling takes place at a temperature below that of recrystallization. The temperature at which the steel is processed affects the molecular structure of the material differently. Hot rolled steel loses its hardness once it has been heated to a high temperature. While cold rolled steel becomes harder.

Ductility is measured by elongation testing. Cold rolled steel has an elongation percentage between 40% and 46%, while in the case of hot rolled steel the percentage is between 30% and 36%. By cold rolling, the thickness of the worked material is reduced. Also, stricter thickness tolerances are achieved than by hot rolling.

There is also a difference regarding the surface of the resulting steel. In the case of hot lamination, the result is a material with a rough surface and rounded corners. But in the case of cold lamination, the surface is glossy and the corners are straight.

The type of steel (hot or cold rolled) is chosen depending on the intended use.

Hot rolling is more suitable for processes where you need more ability to form the steel, such as automotive applications, pipes, water heaters, heavy agricultural equipment, metal constructions and wagons.

Cold rolling

It lends itself better to applications where you need better surface finish, flatness, improved tolerance. This is often used for household appliances, such as refrigerator doors, washing machines, as well as some auto parts that need greater strength, such as roofs, hoods and fenders. These are also the exposed parts of an automobile that will often be painted. Cold rolling allows the steel to be painted, making it a good choice for many different applications.

The rolling process is used especially for obtaining long pieces with a constant section.