What is Differences Between Hot Rolled and Cold Rolled Steel

This article guides the differences between hot rolled and cold rolled steel. Let’s read about that differences.

Steel products are manufactured for a wide variety of functions with different types, grades, chemical compositions and manufacturing processes. The manufacturing process of steel also significantly influences and differentiates the steel products.

One such important distinction we can make among pre-fabricated steel products is the differences between hot rolled and cold rolled steel. Steel comes in different types, grades, shapes and finishes having different specifications and unique properties.

So steel can be widely used in variety of applications such as: construction of structures, infrastructures, appliances, vehicles, wind turbines and many more applications.

Differences Between Hot Rolled and Cold Rolled Steel

The main differences between hot rolled and cold rolled steel is the temperature value at which they are processed. Hot rolled steel is rolled above its recrystallization temperature, whereas cold rolled steel is rolled below its recrystallization temperature. However, cold rolled steel is rolled at high temperature but further processed in cold reduction material.

In general, hot rolled steel has better mechanical properties than cold rolled steel. The hot rolled steel has improved tensile strength, yield strength, ductility and toughness.

But cold rolled steels are typically harder and stronger than standard hot rolled steels. As the steel is shaped at the lower temperatures; it's hardness, resistance against tension breaking and deformation are all increased due to work hardening.

Hot Rolled Steel

Hot rolled steels are prepared when steel are rolled at high temperature over 1700˚F, which is above the steel’s recrystallization temperature. These high temperatures are allowing the steel to be easily shaped, formed and made in much larger sizes. As hot rolled steel cools, it tends to shrink non-uniformly and allows less control over the size and shape of the finished product compared to cold rolled steel.

Hot rolled steel is typically cheaper than cold rolled steel because it does not required the reheating process like cold rolled steel and is therefore produced without much delay in the process.

Characteristics of Hot Rolled Steel

Hot rolled steels often have the following characteristics:

• Hot rolled steels tend to have scaled surface (a remnant of cooling from extreme temperatures).
• They have slightly rounded edges and corners for bar and plate products (due to shrinkage and less precise finishing).
• Slight distortions in their shape.
• They are more malleable and can easily turned into various shapes.
• They have increased ductility and toughness.

Advantages of Hot Rolled Steel

Hot rolled steels are cheaper than cold rolled steels because of the manufacturing process. Hot rolled steels are required only heating process and doesn't require reheating like cold rolled steel. It is also essentially normalized as it is allowed to cool at room temperature; this means it’s free from internal stresses that can arise from quenching or work-hardening processes.

Applications of Hot Rolled Steel

Hot rolled steels can be used in applications where precise shapes and tolerances are not required, such as:

• Structural Components (Railroad Tracks, I-Beams, Sheet Metal)
• Agricultural Equipment
• Metal Buildings
• Stampings
• Automotive Frames

Cold Rolled Steel

Cold rolled steels are essentially hot rolled steels that have been further prepared by heating process which is then re-rolled at room temperature to achieve more exact dimensions and better surface qualities. Cold rolling produces steel with closer dimensional tolerances and a wider range of surface finishes than hot rolling which is up to 20% stronger than hot rolled through the use of strength hardening.

Due to the additional processing, cold rolled steel products come at a higher price. But they are harder and stronger than hot rolled and can be used in precise applications.

Characteristics of Cold Rolled Steel

Cold rolled steels often have the following characteristics:

• Cold rolled steels have more finished surfaces with closer tolerances.
• They have smooth surfaces that are often oily to the touch.
• Cold rolled steel bars are true and square, and often have well-defined edges and corners.
• Cold rolled steel tubes have better concentric uniformity and straightness.

Advantages of Cold Rolled Steel

The advantages of cold rolled steels include following:

• Cold rolled steels are harder and stronger than hot rolled steels.
• They can be used in precise applications.
• Cold rolled steels have increased hardness, resistance against tension breaking and resistance against deformation due to work hardening.
• They have aesthetically pleasing finish with a wider range of surface finishes.

Applications of Cold Rolled Steel

Cold rolled steel has better surface characteristics than hot rolled steel and therefore offers a more aesthetic and visually appealing surface. Cold rolled steel is used in applications where tolerances, surface conditions, concentricity and straightness are factors that includes the following applications:

• Home Appliances
• Metal Furniture
• Aerospace Structural Components
• Automotive Parts

Conclusion

Hope that you like this guide. Understanding the differences between hot rolled and cold rolled steel can help you determine the best type of steel for your needs.

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