Re-rolled steel: What is it?

Steel ingots are rolled in steel plants’ rolling mills to produce plates of the required thickness and enhance or obtain various mechanical and metallurgical properties, such as greater hardness. Rolled steel can be re-rolled for even greater material strength, improved dimensional accuracy, and a better surface finish.

This steel rolling process, also known as tempering, can be used instead of heat treatment. Re-rolling steel allows you to use it in applications where the metal needs to be bent or shaped to a certain degree without it breaking, as can be seen in our Equal Angles, Unequal Angles, and Tees.

What’s the difference between hot and cold rolled steel?

Two different types of this steel are available, namely hot rolled steel and cold or re-rolled steel. When you know the differences between the two, you will be better positioned to choose the type which best suits your needs. Let’s take a closer look at them.

Hot-rolled steel

Hot-rolled steel is steel that has been rolled at high temperatures, usually more than 927°C (1700°F). These temperatures are above the recrystallization temperature of steel, so the metal can be formed, shaped, and rolled into larger sizes with ease. However, the metal does not shrink uniformly as it cools, which means this process offers less control over the finished product’s size and shape.

Steel that has been hot-rolled usually has a scaly finish. This can be removed by grinding, pickling, or sandblasting. The metal is free from internal stresses that can occur from work-hardening processes or quenching. Products might have slightly rounded corners and edges as well as minor distortions. Hot-rolled steel is more malleable, and it offers better ductility and increased toughness. Cheaper than steel that has been cold rolled, this product is often used for structural components such as railroad tracks and sheet metal, as well as for agricultural equipment, automotive frames, metal buildings, and stampings.

Cold rolled steel

Cold rolled steel is produced by re-rolling steel that has been hot rolled for further processing by allowing it to cool at room temperature and then annealed or temper rolled. The result is steel with a wider range of surface finishes and closer dimensional tolerances, like our re-rolled Black Flats.

This type of steel is as much as 20% stronger than steel that has been hot rolled only, thanks to the use of strength hardening. Other advantages include being able to use this product in precise applications, increased resistance against tension breaking, deformation resistance, and an aesthetically pleasing finish with a greater variety of surface finishes. You can obtain more precise shapes after re-rolling steel through additional processes such as breakdown, semi-finishing, sizing, semi-roughing, and finishing. Take a look at our re-rolled Black Rounds.

This type of steel is an excellent choice for applications where concentricity, straightness, surface conditions, and tolerances are factors. This product is used for aerospace structural components, automotive parts, home appliances, and metal furniture. View our re-rolled Black Squares here.

The steel rolling process

The steel rolling process itself is relatively uncomplicated. The unrolled steel, usually known as rolling stock, is passed between two rolls turned at the same peripheral speed in opposite directions. One roll turns clockwise, while the other turns anti-clockwise. They are spaced so that the distance between them is less than the thickness of the rolling stock that enters the space between them. Find the right re-rolled Tapered Flange Channels.

The rolls grip the metal, pulling it between them. This increases the length and width and reduces the thickness of the steel, giving it constant cross section throughout its length. Steel sections are usually rolled in several phases. The ratio of the initial input material and final cross section of the finished product determines the number of rolling phases. Discover our Convex re-rolled products.

To recap, the four main steps of producing cold rolled steel or re-rolled steel include:

Reheating: The input material is heated in a reheating furnace until it reaches rolling temperature.

Rolling: The steel is passed through rollers in various phases: roughing, intermediate, and finishing.

Cooling: The steel is cooled at room temperature. This is where the steel rolling process for hot rolled steel ends.

Re-Rolling: The cooled steel is re-rolled (temper rolled) to produce cold rolled steel.