Hot rolling, the process used to make hot rolled steel, involves rolling steel at high temperatures (typically over ˚F). These high temperatures are above steel&#;s recrystallization temperature, allowing the steel to be easily shaped, formed, and made in larger sizes. As it cools, hot rolled steel tends to shrink non-uniformly, giving less control on the size and shape of the finished product when compared to cold rolled steel.
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Hot rolled steel tends to have a scaly finish which can be removed by pickling, grinding, or sand-blasting. This steel is essentially normalized, meaning free from internal stresses that can arise from quenching or work-hardening processes, because it is allowed to cool at room temperature. Other properties may include:
Hot rolled steel tends to be cheaper than cold rolled steel because it is manufactured without any delays in the process and does not 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.
One of the many differences between hot and cold rolled steel is price. Hot rolled steel tends to be cheaper than cold rolled steel because it is manufactured without any delays in the process and does not require reheating like cold rolled steel. It can be used in applications where precise shapes and tolerances are not required, such as:
Cold rolled steel is essentially hot rolled steel that has been further processed by being allowed to cool at room temperature and annealed or temper rolled. Cold rolling produces steel with closer dimensional tolerances and a wider range of surface finishes than hot rolling. It is also up to 20% stronger than hot rolled through the use of strength hardening.
Cold rolled steel typically results in a product with a better, more finished surface with closer tolerances. It also yields smoother surfaces that are oily to the touch. Other advantages include:
Cold rolled steel is used in applications where tolerances, surface conditions, concentricity, and straightness are factors. It also offers a more aesthetic and visually appealing surface. Other applications include:
Rolling is a metal forming process that employs the use of a series of rollers to alter the shape, improve the uniformity, and/or enhance the mechanical properties of materials. Rolled steel can be categorized into two types&#;hot rolled steel and cold rolled steel&#;which demonstrate distinct characteristics that make them suitable for different applications. When choosing a rolled steel material for a project, it is important to be aware of the differences between the two types and how they affect their performance.
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Hot rolled steel is steel that has undergone the rolling process at a temperature above its recrystallization temperature (usually ° F or greater). Compared to unprocessed steel, the processed material exhibits greater formability and workability, making it easier to work with in subsequent processing operations.
The hot rolling process starts with a large, rectangular slab of metal referred to as a billet. First, the billet is heated and compressed into a large roll. While still hot, it passes through a series of rotating rollers to achieve the desired dimensions. In sheet metal production operations, the rolled steel is then wound into coiled rolls and left to cool. In production operations involving other forms, the processed material is cut into the specified units and packaged.
Hot rolled steel offers several manufacturing advantages, such as:
Since hot rolled steel shrinks slightly during the cooling stage, there is a lesser degree of control over its final shape. For this reason, it is typically used in applications that do not require extremely tight tolerances, such as:
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Cold rolled steel is hot rolled steel that has undergone additional processing to improve its dimensional and mechanical properties. During the cold rolling process, cooled hot rolled steel passes through another series of rollers at room temperature. Since the material is no longer hot and malleable, a significantly higher amount of pressure is required to compress it into the desired shape. While this process can be more labor-intensive and expensive than the hot rolling process, it can achieve tighter dimensional tolerances and better surface qualities.
Compared to hot rolled steel, cold rolled steel offers a variety of advantages, such as:
Cold rolled steel is often used for applications that require tighter tolerances and better surface finishes. Typical parts and products include:
As indicated above, the main difference between hot rolled steel and cold rolled steel is the temperature at which they are processed. Hot rolled steel is rolled above the material&#;s recrystallization temperature, whereas cold rolled steel is rolled below the material&#;s recrystallization temperature. Beyond this quality, there are a few other distinctions between the two materials, including in regard to the following:
These two steel types should not be confused with the technical specifications or grades used to classify steel by composition or physical characteristics. Steel can be hot rolled or cold rolled regardless of its metallurgical specifications or grade.
When evaluating steel options for a project, it is important to keep in mind that some materials will work better than others for certain purposes. Understanding which type of steel offers the right properties for a given application can prevent overspending on raw materials and save time in the long run.
Cold forming is an umbrella term that encompasses several forming processes that occur at or near room temperature, such as bending, drawing, and rolling. At Grob Inc, we specialize in cold rolling specialized profiles onto bar stock.
Our team manufactures cold rolled parts and products from a variety of metals, such as aluminum, naval brass, stainless steel, and other steel alloys. The finished components demonstrate higher tensile strength, greater material hardness, tighter dimensional tolerances, and a better surface finish than ones produced through high-heat forming methods. Additionally, since the cold rolling process involves the displacement of material&#;rather than the removal of material&#;our production operations occur with a better material usage to waste ratio.
Some of the parts and products we regularly produce in these operations include:
For additional information about our cold forming capabilities, check out our cold forming process page.
When considering the use of steel for a project, it is essential to be aware of the differences between hot and cold rolled steel. Both materials exhibit characteristics that make them suitable for different use cases, but cold rolled steel offer numerous advantages over hot rolled steel, including, but not limited to, better strength, dimensional tolerance, and surface finish. For customers looking for a cold rolling partner, the Grob team is here to help.
By partnering with us for their cold rolled metal needs, our customers benefit from our:
To find out more about our standard and custom cold rolling capabilities or discuss your next project with one of our experts, contact us today.
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