Rolling is a metalworking technique used to improve the grain orientation and strength of a material to facilitate future fabrication operations and applications. At its most basic, the process involves passing the material through a pair of rollers to achieve the desired shape and thickness. However, it can be adapted to prepare metal for various applications.
Rolling operations can be classified into two main categories: hot rolling or cold rolling. As suggested by the name, hot rolling involves working with metals that are heated above their recrystallization temperature, while cold rolling involves working with metals that are below their recrystallization temperature. The difference in material temperature at the time of rolling results in processed materials with distinct properties that make them suitable for different applications.
One of the most commonly rolled materials is steel. Below, we highlight the typical steps in a steel hot rolling operation and discuss how hot-rolled steel compares to cold-rolled steel.
Understanding Hot-Rolled Steel
Steel hot rolling operations typically require processing temperatures over 1,700° F since that is the recrystallization temperature for most steels. These high temperatures make the material easier to form and work, allowing for greater freedom in creating shapes. It can be shaped into bars, sheets, tubes, and more.
The basic steps in a steel hot rolling process are as follows:
- The billet—i.e., a large, square or rectangular piece of metal—is heated and flattened to prepare it for the rollers.
- The heated and flattened material is pushed through a series of rollers at high-speed to achieve the desired dimensions.
- Once the material is the right size and thickness, it is further processed depending on its form. For sheet metal products, the material is rolled into coils and allowed to cool. For other product forms (e.g., bars and plates), the material is divided into sections and packaged for delivery.
Advantages of Hot-Rolled Steel vs. Cold-Rolled Steel
While hot-rolled steel has a few disadvantages, such as scaled surface textures (due to the material cooling from high temperatures), it also offers many advantages over cold-rolled steel. For example:
- It requires less energy to make. The high-temperature conditions in hot rolling operations reduce the deformation resistance of the steel material, making it easier, faster, and, consequently, cheaper, to work.
- It accommodates a wider range of sizes and shapes. Unlike the cold rolling process, the hot rolling process can handle various material sizes and shapes. It can perform small and large reductions and work the material into different forms, including, but not limited to, bars, billets, slabs, sheets, and tubes.
Hot-Rolled Steel Products at McDonald Steel
Hot-rolled steel is used in a wide range of applications where dimensional tolerances and surface finish quality are equally as important as strength and cost, with typical industries that utilize the material including construction and railroad, bridges and infrastructure, automotive, and many more.
Need a hot-rolled steel supplier for your next project? McDonald Steel has you covered. Equipped with tooling for over 500 symmetrical and asymmetrical hot-rolled steel shapes, we can provide materials for a variety of applications across multiple markets.