Difference between hot and cold rolled steel

Have you ever wondered how rail tracks are made? Or how sheet metal is made with such uniform thickness? Rolling is an important metalworking process that flattens and shapes steel into anything from I‑beams to reinforcing bar and even beer cans.

Roll bending, roll forming, profile rolling, flat rolling and ring rolling are all examples of rolling processes. However, fundamental to these processes is temperature. Hot rolling and cold rolling produces steel that’s different in appearance, quality and use.

So, what is the difference between hot rolled and cold rolled steel?

Hot rolled steel

The process involves heating steel to above the recrystalisation temperature and deformed between rollers. Hot rolling makes shaping and forming much easier, and it is even typically cheaper and quicker to manufacture. However, hot rolled steel shrinks during the cooling process, making the size and shape less predictable (dimensional tolerances are usually 2-5% of the overall dimension).

Appearance and Use: Hot rolled steel often has a rough, blue-grey finish. Products produced by hot rolling are used in the welding and construction trades to make items like rail tracks, pipes, I-beams and guard rails, where exacting tolerances are not required.

Cold rolled steel

Rolling at room temperature, or below steel’s recrystalisation temperature, is known as cold rolling. This process actually increase strength by up to 20 per cent through strain hardening. Cold rolled sheets can be worked into various thicknesses, while shapes require sizing, roughing and finishing. Cold rolled steel is superior in tolerance, strength, straightness and finish when compared to hot rolled steel.

Appearance and Use: Cold rolled steel is grey in appearance and is smooth to the touch. Products commonly cold-rolled include strips, sheets, bars and rods, which are usually smaller than their hot rolled counterparts.

For more information on the difference between hot and cold rolled steel, or to find out more about our steel profile cutting services, contact ShapeCUT today on 1800 ShapeCUT (1800 742 732). ShapeCUT delivers fast, reliable and precision profile cutting, Australian rolled steel and metal processing in Brisbane.