There are many grades, specifications, shapes and surface treatments of steel-the World Steel Association lists more than 3,500 different grades of steel, each with unique properties. Various types mean that steel can be widely used in infrastructure, electrical appliances, vehicles, wind turbines and more applications. However, optimizing the performance of steel for each application is more than just changing the chemical composition. The manufacturing process of steel can also have a significant impact on steel products-even if the grades and specifications are the same. One of the main differences between precast steel products is the difference between hot rolled steel and cold rolled steel.
Hot rolled steel
Hot rolled steel is steel rolled at very high temperatures. Over 1,700˚F, which is higher than the recrystallization temperature of most steels. This makes the steel easier to shape and results in the product easier to use. To process hot-rolled steel, manufacturers first start with a large rectangular piece of metal called a billet. The billet is heated and then sent for pretreatment, where it is flattened into a large roll. From there, it is kept at high temperature and passed through a series of rollers to reach its final size. The white-hot steel strands are pushed through the rollers at high speed. For sheet metal, rolled steel is spun into coils and cooled. For other forms, such as bars or plates, the material is segmented and packaged. Hot rolled steel and cold rolled steel shrink slightly when cooled. Cold rolled steel is hot rolled steel that is further processed. Since hot-rolled steel is cooled after processing, it has less control over its final shape, so it is not suitable for precision applications. Hot rolled steel is generally used for applications where specific dimensions are not important. Railroad tracks and construction projects usually use hot rolled steel. Hot rolled steel can usually be identified by the following characteristics: Scaled surface-cooling residue from extreme temperatures. The edges and corners of bar and sheet products are slightly rounded (due to shrinkage and less precise finishing). Slightly twisted, cooling may result in a slightly trapezoidal shape instead of a perfect square angle.
Cold rolled steel
Cold-worked steel is generally harder and stronger than standard hot-rolled steel. Cold rolled steel is hot rolled steel that is further processed. After the hot-rolled steel is cooled, it is re-rolled at room temperature to obtain more precise dimensions and better surface quality. Cold "rolled" steel is usually used to describe a series of finishing processes, but technically speaking, "cold rolled" only applies to plates that are compressed between rollers. The steel mold being pulled, such as a bar or tube, is "drawn", not rolled. Other cold finishing processes include turning, grinding and polishing-each process is used to transform existing hot-rolled blanks into more refined products. Cold rolled steel can usually be identified by the following characteristics: a better, more refined surface with tighter tolerances. Smooth surfaces are usually greasy to the touch. The strip shape of cold rolled steel is real and square, usually with clear edges and corners. Cold rolled steel has better concentric uniformity and straightness.
The difference between hot rolled steel and cold rolled steel
It is important to note that the difference between hot rolled steel and cold rolled steel lies in one of the processes. "Hot rolling" refers to heat processing. "Cold rolling" refers to a process performed at or near room temperature. Cold rolled steel is hot rolled steel that is further processed. Although these technologies affect overall performance and applications, they should not be confused with official specifications and steel grades related to metallurgical composition and performance levels. Different grades and specifications of steel can be hot-rolled steel and cold-rolled steel-including basic carbon steel and other alloy steels. This may seem obvious, but certain types of steel are more suitable for certain applications. Knowing which to use helps avoid overspending on raw materials. It can also save additional processing time and money. Understanding the difference between hot rolled steel and cold rolled steel is a necessary condition for choosing one of them.
Manufacturing and product design
Depending on what you are building, different materials have their own advantages and disadvantages. For ordinary projects or one-off production, hot-rolled steel and cold-rolled steel materials can provide building blocks for any imaginable structural configuration. For more information about steel, or to request a quotation for a customized project, please contact us.
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