Learn more about the benefits of each type of steel and which one to choose for your project

What is the difference between hot rolled and cold rolled steel?

It is important to note that the main difference between hot rolled and cold rolled steel is the process. "Hot rolled" refers to processing performed with heat. "Cold rolled" refers to processes performed at a temperature close to room temperature. Although these techniques affect overall performance and application, they should not be confused with the formal
specifications and steel grades related to metallurgical composition and performance rating.

Steel of various grades and specifications can be hot rolled or cold rolled, including plain carbon steels and other alloy steels.

It may seem obvious, but some types of steel are for specific applications more suitable. Knowing which ones to use can help you avoid overspending on raw materials. You can also save time and money on additional processing. Understanding the differences between hot and cold steel is crucial in deciding between the two.

Hot rolled steel

Hot rolled steel is steel that has been rolled at very high temperatures.

Hot rolled steel is steel that has been roll pressed at very high temperatures in excess of 1700°F, which is above the recrystallization temperature for most steels. This makes the steel easier to form and results in products that are easier to machine.

To process hot rolled steel, fabricators first start with a large rectangular length of
- metal, called bill. The billet is heated and then sent to pre-processing where it is flattened into a large roll.

From there it is held at a high temperature and passed through a series of rollers to reach its final dimensions. Red-hot steel wires are pushed through the rollers at high speed. For sheet metal, rolled steel is spun into coils and allowed to cool. For other shapes, such as bars or plates, the materials are cut and packaged.

Steel shrinks slightly as it cools.

As hot rolled steel cools after processing, its final shape is less controllable, making it less suitable for precision applications. Hot rolled steel is often used in applications where tiny specific dimensions are not critical. Hot rolled steel is commonly used in railroad tracks and construction projects.

Hot rolled steel can often be identified by the following features:

A scaly surface - a remnant of cooling from extreme temperatures

Slightly rounded Edges and corners for bar and sheet products (due to shrinkage and less precise finishing)

Slight distortions where cooling can result in slightly trapezoidal shapes as opposed to perfectly square corners

What are the advantages of hot rolled steel?

Hot rolled steel generally requires much less
processing than cold rolled steel, making it much cheaper. Because hot-rolled steel is allowed to cool to room temperature, it is essentially normalized; H. it is free from internal stresses that can arise from quenching or work hardening processes.

Hot rolled steel is ideal when dimensional tolerances are not as important as the overall strength of the material and when surface finish is not of crucial importance. When surface finish is critical, scale can be removed by grinding, grit blasting or acid bath pickling.

Once the liner is removed, a variety of brushed or high gloss finishes can also be applied. Descaled steel also provides a better surface for paint and other surface coatings.

Cold Rolled Steel

Cold rolled steel is typically harder and stronger than standard hot rolled steels.

Cold rolled steel is essentially hot rolled steel that has undergone further processing. After the hot rolled steel has cooled, it is re-rolled at room temperature to achieve more accurate
dimensions and better surface qualities.

'Cold-rolled' steel is often used to describe a variety of finishing processes, although technically 'cold-rolled' only refers to sheets that are compressed between rollers. Drawn steel shapes such as rods or tubes are "stretched", not rolled. Other cold finishing processes include turning, grinding and polishing, each used to convert existing hot rolled material into more refined products.

Cold rolled steel can often be identified with the
with the following characteristics:

Better, more finished surfaces with tighter tolerances

Smooth surfaces that often feel oily

Bars are correct and square and have often well-defined edges and corners

Tubes have better concentric smoothness and straightness

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