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.
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Basic Differences Between Hot Rolled Steel and Cold Rolled Steel
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.
Visual Difference
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.
When to Use Hot Rolled Steel
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.
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Hot Rolled Steel Applications
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. Hot rolled steel applications include:
- Square tubing
- Rectangle tubing
- Sheet & plate
- Flat bar
- P&O strip bar
When to Use Cold Rolled Steel
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.
Cold Rolled Steel Applications
Within the cold rolling process, steel sheet is cooled at room temperature (after hot rolling) and is then annealed or tempers rolled. Although “cold rolled steel” is a specific type of steel, the term is often used to mean all kinds of carbon steel materials. Cold rolled steel applications include:
- Sheet & Plate
- round bar
- rectangle bar
- square bar
- hex bar
As a side note, while shopping around for options, sometimes cold-rolled steel is also called cold-finished or cold-drawn steel. These names are ubiquitous when referring to bars.
Cold Rolled or Hot Rolled Steel, Which is Better?
Ultimately, there is no right or wrong answer on which one is better. Both have benefits and drawbacks that make the ideal option change from project to project. Whichever product suits your needs, Industrial Metal Supply is here to help.
Contact IMS for Premium Cold Rolled or Hot Rolled Steel Today
In general, hot rolling (
hot rolled seamless pipe) has better mechanical properties than cold rolling. The hot rolled steel has improved tensile strength, yield strength, ductility and toughness. In addition, it is important that heat treatment eliminates residual stresses. While cold rolling refers to the processing of steel sheets or strips into various types of steel by cold drawing, cold bending, cold drawing, etc. At normal temperature, which may result from uneven deformation of the steel and
esidual stress during processing, this residual stress has a great influence on stability. Both hot rolling and cold rolling are processes of forming steel or steel sheets, which have a great influence on the microstructure and properties of steel. The rolling of steel is mainly hot rolling, and the cold rolling is only used for producing small steel and thin steel.
Hot rolling
Advantages:
The cast structure of the ingot can be destroyed, the grain of the steel can be refined, and the defects of the microstructure can be eliminated, so that the steel structure is compacted and the mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer isotropic to a certain extent; bubbles, cracks and looseness formed during casting can also be welded under high temperature and pressure.
Disadvantages:
1. After hot rolling, non-metallic inclusions (mainly sulfides and oxides, as well as silicates) inside the steel are pressed into thin sheets, and delamination (sandwich) occurs. The delamination greatly deteriorates the tensile properties of the steel in the thickness direction, and it is possible to cause interlayer tearing when the weld is shrunk. The local strain induced by weld shrinkage often reaches several times the yield point strain and is much larger than the strain caused by the load.
2, Residual stress caused by uneven cooling. The residual stress is the internal self-phase equilibrium stress without external force. The hot-rolled steel of various sections has such residual stress. The larger the section size of the general steel, the larger the residual stress. Although the residual stress is self-phase-balanced, it still has some influence on the performance of steel members under external force. Such as deformation, stability, fatigue and other aspects may have adverse effects.
Cold rolling
Advantages:
The molding speed is fast, the output is high, and the coating is not damaged, and various cross-section forms can be formed to meet the requirements of the use conditions;
Cold rolling can cause a large plastic deformation of the steel, thereby increasing the yield point of the steel.
Disadvantages:
1. Although there is no hot plastic compression during the forming process, residual stress still exists in the section, which inevitably affects the overall and local buckling characteristics of the steel.
2. The cold-rolled steel profile is generally an open section, so that the free torsional stiffness of the section is low. It is easy to twist when being bent, and it is prone to bending and torsion buckling when pressed, and the torsion resistance is poor. + Third, the wall thickness of the cold-rolled steel is small, and there is no thickening at the corners where the plates are joined, and the ability to withstand localized concentrated loads is weak.
The main differences between hot and cold rolling are:
1. Cold-rolled steel allows partial buckling of the section, so that the bearing capacity of the bar after buckling can be fully utilized; and the hot-rolled steel does not allow local buckling of the section.
2. The causes of residual stresses in hot-rolled and cold-rolled steels are different, so the distribution on the cross-section is also very different. The residual stress distribution on the section of the cold-formed thin-walled steel is curved, while the residual stress distribution on the section of the hot-striped steel or welded steel is a film type.
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