Potential Clients often ask us about the differences between hot rolled steel and cold rolled steel. There are a few fundamental differences between these two types of metal rolling. The differences between hot rolled steel and cold rolled steel relates to the way the metals are processed at the mill, and has nothing to do with the product specification or grade. Hot rolled steel requires rolling the steel at extremely hot temperatures, where as cold rolled steel is processed further in cold reduction mills where the material is cooled followed by annealing and/or tempers rolling.
Hot Rolled Steel
Hot steel rolling is a mill process which involves rolling the steel at a high temperature (typically at a temperature over 926 Celsius, which is above the steel’s recrystallization temperature. When steel is above the recrystallization temperature, it can be moulded and shaped easily, and the steel can be formed in much larger sizes.
Hot rolled steel is normally cheaper than cold rolled steel due to the fact that it is often supplied without any delays in the manufacturing process, and therefore the re-heating of the steel is not required as it is with cold rolled. When the hot rolled steel cools off it will shrink somewhat thus giving less control on the size and shape of the completed product when compared to cold rolled.
Cold Rolled Steel
Cold rolled steel is typically hot rolled steel that has had further processing. The steel is processed more in cold reduction mills, where the steel is cooled at room temperature, followed by annealing and tempers rolling. This manufacturing process will produce steel with closer and accurate dimensional tolerances and a wider range of surface finishes. The term Cold Rolled Steel is mistakenly used on all products, when actually the product name refers to the rolling of flat rolled sheet and coil products.
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