There is a wide range of processes that steel may undergo to achieve its desired physical outcomes. Hot rolling and cold rolling steel are two common methods of manipulating steel’s physical properties. Our team of steel experts has broken down the key differences between these two methods to help you better understand what you may need for your project.
The Rolling Process
Like their names suggest, all types of hot and cold rolled steel are passed through a series of rolls, typically two or four rolls. The rolls squeeze the steel and apply pressure to flatten or shape it into the desired shape, which changes the physical properties of the steel. The steel is almost always passed through rolls more than once until the desired shape or approximate shape is achieved. For a more detailed explanation, check out our article on the processes of hot and cold rolling.
Hot Rolled Steel Overview
The process of hot rolling involves rolling steel at a temperature above the steel’s recrystallization temperature, which takes place at over 1,700 degrees Fahrenheit. Steel above the recrystallization temperature can be shaped and formed much more easily than colder steel, and it can start in much larger sizes. It is also typically cheaper to manufacture than cold rolled steel. Because manufacturers can produce hot rolled steel without pauses or delays, the steel doesn’t need to be reheated, thus saving in labor costs and time spent manufacturing. During the cooling process, hot rolled steel will shrink, and the size and shape of the steel will be less predictable than cold rolled steel.
Cold Rolled Steel Overview
Cold rolled steel is manufactured at temperatures below its recrystallization temperature, typically at room temperature (around 68 degrees Fahrenheit). Because the steel is manufactured at a much lower temperature, there’s no need to worry about the steel shrinking or changing form or appearance.
Appearance
Hot rolled products will have a scaly gray finish and more rounded, less precise corners than cold rolled steel. This makes hot rolled steel more ideal for applications where higher quantities are needed and extremely precise dimensions are not of the utmost concern. Sometimes, the scaly finish is preferred for the end product in machining or metalworking, as this can help reduce wear and friction over time.
Conversely, cold rolled steel has a very smooth texture and surface, making for an arguably more appealing appearance. Because of its smoothness, cold rolled steel can be produced with more accurate dimensions and finishes.
Mechanical Properties
The mechanical properties of steel often depend on its grade, or chemical makeup. For that reason, it is never safe to make assumptions about the mechanical properties of hot rolled vs cold rolled steel unless they are the same steel grade. Using the very common 1018 as an example, the chemical properties of 1018 steel will be the same as that cannot be altered by either rolling method. However, we can see there are key differences between cold rolled and hot rolled in terms of the steel’s mechanical properties post-treatment.
| Mechanical Property | Hot Rolled 1018 Steel | Cold Rolled 1018 Steel |
| Tensile Strength | 67,000 psi | 85,000 psi |
| Yield Strength | 45,000 psi | 70,000 psi |
| Reduction of Area | 58 | 55 |
| Elongation in 2″ | 36 | 28 |
| Brinell Hardness | 137 | 167 |
As demonstrated in the table above, cold rolled steel is tougher and can withstand more pressure. However, hot rolled steel is more flexible and cost-effective.
Common Applications
You’ll find hot rolled products like hot rolled steel bars in the welding and construction trades, such as making railroad tracks, I-beams, and other steel construction materials that don’t require super-precise shapes.
Cold rolled steel products are preferred in applications where higher durability and appearance are of greater concern. Some common uses of cold rolled steel include automotive parts, household appliances, and structural beams in construction.
Hot Rolled vs Cold Rolled Steel Summary
The following are some of the key differences in hot rolled vs cold rolled steel:
- Hot rolled steel is rolled or shaped at a high temperature, while cold rolled steel is rolled at room temperature.
- Cold rolled has a smooth and shiny finish, while hot rolled has a grey and scaly finish.
- Cold rolled has sharper corners and more precise dimensions than hot rolled.
- In general, cold rolled has better mechanical properties than hot rolled.
- Hot rolled steel is more cost-effective than cold rolled steel due to reduced labor costs.
Questions? Connect with Capital Steel
In general, neither hot rolled nor cold rolled steel is “better” than the other; the better choice solely depends on your project needs. That’s why Capital Steel proudly manufactures and supplies both types of treated steel across the nation. Have any lingering questions about which type of steel would be best for your project? Contact our team of steel experts today. We’re ready and eager to assist you every step of the way.
