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April 22, 2020

What is the Difference between Hot Rolled and Cold Rolled Steel?

What is the Difference between Hot Rolled and Cold Rolled Steel

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

  1. Production of hot rolled steel
  2. Advantages of hot rolled steel
    • Cost-effective
    • Large reduction
    • Manufacture of a wide range of shapes
  1. Production of cold rolled steel
  2. Advantages of cold rolled steel
    • Good finish
    • High production rate
    • Fast molding speed

 

When it comes to manufacturing steel, there are many different kinds of processes involved. One of these methods is called rolling which branches out into two types: hot and cold rolled steel. The debate between hot rolled vs cold rolled steel persists to determine which process is the more desirable.

Simply put, rolling is a metal fabrication process that involves the formation of molten metals, or other kinds of materials into products such as sheets, wires, bars, and the like. This process is most commonly used for mass steel production where the final steel products can enjoy usage in automotive, construction, or residential industries.

If you want to learn more about the differences between hot rolled and cold rolled steel, then continue reading.

 

Production of hot rolled steel

Production of hot rolled steel

Hot rolled steel refers to a process by which steel is subject to high temperatures in order to create the finished sheet product. As a metal fabrication process, this is done in the mill, where temperatures of around 926 degrees Celsius is applied to the metal. Typically, the temperature range applied falls above the material’s recrystallization temperature or the temperature at which the coarser-grained crystalline structure of steel is replaced by finer-grained crystals, creating products which are easier to form.

In hot rolled steel manufacturing, the process begins with a large and rectangular-shaped length of metal which is referred to as a billet. After which, the billet is subjected to high temperatures, and then it is flattened into a large roll. This is only the pre-processing phase though, as the billet is still subjected to constant heat and is run under several industry-grade rollers. The purpose of this is so that the desired finish may be achieved. For convenience, sheet metals are wound into coils and are left to cool. 

Since the steel sheet is left to cool after being subjected to high temperatures, this process may result in more irregularities in the shape of the product. As such, it is deemed to be more useful in applications where precision in dimension isn’t really critical, particularly construction projects, beams, simple cross-sections, or other kinds of railroad track applications.

 

Advantages of hot-rolled steel

Now that you’ve learned about the production of hot rolled steel, it’s now important to understand the many benefits it provides. Knowing the advantages of this process can help one determine why they should prefer this process, over cold rolled steel, for example.

While there are many other benefits of hot rolled steel, the focus will be on the following three: cost-effective, large reduction, and can be manufactured in a wide range of shapes.

Cost-effective

One of the benefits involved in the production of hot-rolled steel is that it is cost-effective for the manufacturer. One of the main reasons for this is that the dimensions of the resulting steel sheet aren’t really crucial in the production process. This means that less millwork is required in order to produce the desired shape. After the steel has undergone high temperatures, it is already allowed to cool on its own, meaning there is less focus on dimensional precision.

Large reduction

The hot rolling process also results in a larger reduction. Generally, reduction refers to a process that involves the reactions utilized in order to obtain metals from their oxides. This process involves the use of substances that have a greater attraction for oxygen than the metal. By having a large reduction in hot rolled steel, this type of chemical reaction can take place in much larger-scale scenarios.

Manufacture of a wide range of shapes

Finally, hot rolled steel can result in the production of other materials such as wires, steel sheets, and the like. The resulting varying shapes can make steel materials produced from this kind of process, useful in many more industries.

 

Production of cold rolled steel

Cold rolled steel production involves a more physically-intensive process. Cold rolling typically begins after a steel material has undergone hot rolling. Steel which has been allowed to cool on its own is subject to further milling processes. The resulting product has more accurate dimensions and more precise shapes. By cold rolling steel, many of the previous surface irregularities will have been smoothed out. 

It’s fairly easy to differentiate a steel product that has undergone cold rolling. They’re typically shinier in appearance and have an oil-like quality when touched as their texture is highly smooth. For example, resulting steel tubes are more uniform in shape, while steel bars have finer and less coarse edges.

Advantages of cold rolled steel

Some of the advantages of cold rolled steel definitely have to do with regards to product precision. Furthermore, cold rolled steel is considered to be more durable, compared to hot rolled steel.

Nevertheless, other advantages of cold rolling include a good finish, a high rate of production, and a fast molding speed.

Good finish

Having a good steel finish is highly essential, especially for aesthetic purposes. There are many instances where steel tubing enjoys use in exposed construction or residential work. The smooth finish of any steel material which has undergone cold rolling allows for a more attractive appearance. Furthermore, it can complement many other elements in a particular structure, or in whatever constructional usage.

High production rate

Considered to be a secondary process to hot rolling, cold rolled steel will undoubtedly result in a higher rate of production. The reason for this is that much of the mill processing has already been conducted on the steel during the hot rolling process. Cold rolling simply aims to further smoothen out edges, create glossier finishes, and further take out the irregularities in the steel product.

Fast molding speed

Cold rolling is also deemed a faster way of molding metal. There is no need for further complexities in this kind of processing, as much of the molding-intensive work has already been done through the hot rolling process. From the perspective of the manufacturer, this quality gives them more time to focus on other kinds of steel manufacturing processes. Anyone who might require a wholesale supply of more accurately molded steel tubing, for example, would be easily able to get it in no time.

 

Key Takeaway

Knowing the difference between hot rolled vs cold rolled steel is as simple as understanding the processes which are involved behind each of these methods of metal fabrication. To reiterate, hot rolling steel is a more physically intensive process as it involves the primary deformation of raw steel material, into desired shapes — albeit with less attention to accurate dimensions. On the other hand, cold rolling is done in order to smoothen out the rough edges in hot rolled steel, creating steel products that have more precise dimensions.

The guide above has hopefully helped you understand these two kinds of metal fabrication processes.

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