Rolled steel can be made via two different processes – hot rolled or cold rolled. Hot rolled steel is rolled at extremely high temperatures while cold rolled steel is hot rolled steel that is processed again at cooler temperatures. Knowing the difference between the two is essential to understanding which type works best for certain applications based on your needs.
Hot rolling steel involves pressing it at temperatures above 1700˚F as this surpasses its recrystallization temperature, making it malleable and easier to work with. However, as it cools down it tends to shrink creating challenges in controlling its final shape. That is why hot rolled steel is more often used in projects that do not require extreme precision. This includes structural parts such as beams or railroad tracks as well as auto parts and frames. Hot rolled steel is typically characterized by a scaly surface, malleability, low internal stress, and minor distortions. Hot rolled steel is also less expensive than cold rolled steel since there is less processing involved and few delays (it does not have to be reheated like cold rolled steel does).
Cold rolling steel involves taking hot rolled steel a step further by processing, or re-rolling it, at a cool temperature. The product of cold rolling is steel that has a greater precision, resistance, strength, and range of finishes. Cold rolled steel has a smooth, shiny finish as opposed to a scaly one and is far harder and more durable than hot rolled steel (as a result of using strength hardening). These beneficial properties mean that cold rolled steel is more appropriate for use in applications that require high precision (it does not shrink after processing like hot rolled steel does), closer tolerances, aesthetic finishing, and superior strength. While this method of rolling steel requires more labor and money, it provides higher quality and exactness in its results. Cold rolled steel products can include appliances, metal furniture, auto and aerospace parts, and more.
At Bulldog Steel, we specialize in cold rolling steel and offer a variety of projects to suit numerous steel applications. Contact us today for more information on steel products and processing!