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:
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.
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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.
You may have heard of both hot rolled steel and cold rolled steel, but do you know the difference between them? If not, we’re here to help.
Production of both hot rolled steel and cold rolled steel starts with the same steps. They're both initially processed at extremely high temperatures. However, once the treated steel is ready, cold rolled steel goes through a few extra steps. The mill lets the metal cool off until it's room temperature, then draws it through rollers or puts it through annealing treatment. This additional labor makes it more expensive than hot rolled steel.
There are three main visual differences between hot rolled steel and cold rolled steel. Hot rolled steel has rounded edges, a rough surface texture, and no grease on its finish. Alternatively, cold rolled steel has sharp edges, a very smooth surface texture, and an oily or greasy feel to it.
The pros and cons of hot rolled steel come down to strength versus price. Hot rolled steel is weaker than cold rolled, but it’s also cheaper since it doesn’t go through the second production process. However, this doesn't automatically mean cold is better just because it's stronger and more expensive.
The more significant difference in how to use it is how specific your material needs are. Hot rolled steel is perfect for welding, railroad tracks, and I-beams because there is less concern for smooth finishes and precise shapes. The tolerance range is also wider because the metal shrinks during the cooling process, so you can't be as exact with the measurements.
While hot rolled steel has a rougher surface, the aesthetic difference is fixable if that's your only reason for avoiding it. It will add to the total cost, but you can grind or sandblast the steel to a smooth finish.
Cold rolled steel is going to cost more, but it may be worth the higher price tag if it fits your needs. You're going to pay for tight tolerance, smooth finish, and consistency between pieces.
So when should you splurge on the higher-cost option? In addition to the visual benefits of a smooth surface, cold rolled steel is best when you need consistency and tight tolerances on a project. Workers shape the steel at room temperature, so there's no risk of shrinkage during the cooling process. You'll know the exact dimensions you're getting, and every piece is uniform.
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