Hot rolled steel coil is steel that has been roll-pressed at very high temperatures—specifically over 1,700˚F, which is above the re-crystallization temperature. This makes the steel easier to create and resulting in products that are easier to work with.
To create hot rolled steel, manufacturers initiate the process with a large rectangular length of metal, called a billet. This billet is heated and then flattened into a large roll. From there, it its state is maintained at a high temperature and then run through a series of rollers to achieve its initial shape. The white-hot strands of steel are run through the rollers at high speeds. To attain sheet metal, rolled steel is spun into coils and left to cool. For other forms, such as plates or bars, the materials are sectioned and packaged.
On cooling steel slightly shrinks, however, in this method of manufacturing it is allowed to do so without controlling the final shape. Which makes the resulting steel less suitable for precision applications. Hot rolled steel is often used in applications where minutely specific dimensions are not crucial such as railroad tracks and construction projects.
Hot rolled steel can often be identified by the following characteristics:
- A scaled or rough surface which is a remnant of cooling from extreme temperatures
- Slightly rounded edges and corners for bar and plate products (due to shrinkage and less precise finishing)
- Slight distortions, where cooling may result in slightly different shapes and forms
Hot rolled steel typically requires much less processing than cold rolled steel, which makes it a lot cheaper. Because it is allowed to cool at room temperature, the steel is essentially normalized—meaning it is free from internal stresses that can arise from quenching or work hardening processes.
Hot rolled steel is ideal where accurate dimensions and shape are not as important as overall material strength. Where surface finish is not a key concern either. However where surface finish is a concern, scaling can be removed by sand blasting, grinding, or acid-bath pickling. The process involves passing the steel through an acidic solution, which helps in neutralizing the surface oxides and subsequently oiling the surface to make it corrosion-resistant.
Some of its features include
- Choice of customization as per customers’ requirements
- Finding use in fabrication of container vessels, boiler, vehicle
- Choice of surface treatment like zero spangle, chromate treatment, oiled and regular
- Excellent stamping properties