When it comes to steel, there are two main types: Hot rolled steel and cold-rolled steel. Both have unique benefits and drawbacks, which is why deciding which type of steel is right for your project can be confusing. In this blog post, we will discuss the differences between hot-rolled and cold-rolled steel, so you can decide which type of steel is best for you.
What is Hot rolled steel?
Hot rolled steel has been heated to high temperatures, making it easier to shape and mould. Hot rolled steel is often used in construction projects because it can be bent or shaped without breaking. However, hot rolled steel is not as strong as cold rolled steel, so it is not ideal for projects that require a lot of strength or durability.
Hot rolled steel is plasticity; welding is very good, so we are more commonly used; Hot rolling is processed at a high temperature above 1000 degrees. Recrystallize the steel inside. Make it better material. But hot rolling does not change the structural properties of the metal.
Properties of hot rolled steel:
The following attributes will help you identify hot-rolled steel：
- Scaly surface: Cooling at high temperatures can leave a residue on the surface of the steel, making it appear scaly.
- Slight deformation: Cooling will produce a slightly trapezoidal shape with no perfect Angle.
- The corners and edges are slightly rounded: due to shrinkage and reduced finishing accuracy.
- Softer: Hot-rolled steel is not as strong as cold-rolled steel.
Advantages of Hot Rolled Steel
- Scaly surface: Cooling at high temperatures can leave a residue on the surface of the steel, making it appear scaly.
- Slight deformation: Cooling will produce a slightly trapezoidal shape with no perfect Angle.
- The corners and edges are slightly rounded: due to shrinkage and reduced finishing accuracy.
- Softer: Hot-rolled steel is not as strong as cold-rolled steel.
Disadvantages of Hot Rolled Steel
- Less Accurate Sizes: Hot-rolled steel is less accurate in terms of size than cold-rolled steel.
- Inferior Surface Finish: Hot rolled steel has a scaly surface finish that is not as smooth as cold rolled steel.
- More Brittle: Hot rolled steel is more brittle than cold rolled steel and is not ideal for projects that require a lot of strength.
Application of hot-rolled steel
Applications for hot-rolled steel are typically those that do not require strict tolerances and include:
Ships, automobiles,
Bridges, buildings,
machinery,
pressure vessels
What is Cold rolled steel?
Cold-rolled steel is steel whose metal material is cooled to a low temperature by a cold reduction mills,which makes it harder and more brittle. Cold rolling steel is often used in projects that require a high degree of strength or durability, such as bridges or buildings. However, cold-rolled steel is not as easy to shape or mould as hot-rolled steel, so it is not ideal for projects that require a lot of flexibility.
Properties of cold rolled steel:
The following attributes will help you identify cold-rolled steel：
- Smooth and shiny surface – Cold-rolled steel has a smooth, shiny surface free of scaly residue.
- Angular corners and edges – Cold-rolled steel has sharp, angular corners and edges.
- More brittle – Cold-rolled steel is more brittle than hot-rolled steel and is not ideal for projects that require a lot of flexibility.
Advantages of Cold Rolled Steel
More Accurate Sizes:
The cold roll forming products are accurate in size and uniform in thickness, and the thickness difference of the roll is generally not more than 0.01-0.03mm or smaller, which can fully meet the requirements of high-precision tolerance;
Smooth Surface Finishes:
Cold rolling steel has a smooth, shiny surface free of scaly residue.
Stronger:
Cold-rolled steel is often used in projects that require a high degree of strength or durability.
Disadvantages of Cold Rolled Steel
More Expensive:
Cold-rolled steel is more expensive than hot-rolled steel.
Less Flexible:
Cold-rolled steel is not as easy to shape or mould as hot-rolled steel. The cold-rolled section is usually an open section, which makes the free torsional stiffness of the section low. Torsion easily appears when bending or bending, and torsion buckling easily appears when compression and the torsional resistance is poor.
Residual stress:
There is no thermal plastic compression in the forming process, but there is still residual stress in the section, which will inevitably affect the steel’s global and local buckling characteristics.
Application of cold rolled steel:
Cold rolled steel is often used in industries with high machining accuracy requirements, and It is often used in the following areas:
Aerospace parts
Mechanical components
Home appliances
Rods, bars, strips, and sheet metal
Metal furniture structures
Hot-rolled steel Vs Cold-rolled steel
Hot rolled steel is less expensive than cold rolled steel because it does not require much processing. Hot rolled steel is also more malleable and can be moulded to your desired shape. However, hot rolled steel is not as strong as cold rolled steel, so it might not be the best choice for projects that require a lot of strength or durability.
Cold-rolled steel is more expensive than hot-rolled steel because it requires more processing. Cold-rolled steel is also harder and less malleable, so it cannot be moulded to your desired shape. However, cold rolled steel is stronger than hot rolled steel, so it might be the best choice for projects that require a lot of strength or durability.
So, which type of steel is right for you? It depends on your project requirements. Cold rolled steel is better if you need a strong and durable material. However, hot rolled steel is the better choice if you need a material that is easy to shape and mould. Whichever type of steel you choose, make sure you partner with a reputable steel supplier who can provide high-quality materials for your project.
After examining their forming process and various properties, you may get an idea of the difference between hot and cold rolled steel. The differences in mechanical properties are summarized in the following table:
| Properties | Hot Rolled Steel | Cold Rolled Steel |
| Tensile Strength | 67,000 psi | 85,000 psi |
| Yield Strength | 45,000 psi | 70,000 psi |
| Elongation in 2” | 36 | 28 |
| Reduction of Area | 58 | 55 |
| Brinell Hardness | 137 | 167 |
The following details are the main differences between cold and hot rolled steel:
1.Appearance and Surface Quality
As the name suggests, cold-rolled steel has a smoother and shinier finish than hot-rolled steel. Hot rolled steel has a dull greyish appearance and often leaves scaly residue. Cold rolled metal also has a sharper finished surface due to the rolling process.
Hot rolled steels typically have a dark-coloured scale visible on the surface, often removed by pickling processes. Once Hot rolled steel has cooled, it is passed through a set of rollers to achieve its final dimensions. During the cold rolling process, Hot rolled steel is compressed at room temperature. Cold-rolled steels are typically produced in higher quantities and go through several more processing steps compared to Hot rolled steel.
The surface quality of Hot rolled steel is often not as good as Cold rolled steel. The hot rolling process leaves behind scaly residue on the surface of the metal. Hot rolled steel is often pickled in acid to achieve a smoother and brighter finish. Cold rolled steels typically have a much cleaner appearance and are often used in applications where aesthetics are important.
2.Recrystallization Point
Hot rolled steels are typically recrystallized at around 1650 degrees Fahrenheit. Cold rolled steels are typically recrystallized at around 1750 degrees Fahrenheit. Because Hot rolled steel is cooled at a lower temperature, it can be shaped and formed more easily than Cold rolled steel.
Hot rolled steels are usually used in applications where the material does not need to be very strong. Cold rolled steels are usually used in applications where the material needs to be stronger. Hot rolled steel is less likely to crack or tear than Cold rolled steel.
2.Recrystallization Point
Hot rolled steels are typically recrystallized at around 1650 degrees Fahrenheit. Cold rolled steels are typically recrystallized at around 1750 degrees Fahrenheit. Because Hot rolled steel is cooled at a lower temperature, it can be shaped and formed more easily than Cold rolled steel.
Hot rolled steels are usually used in applications where the material does not need to be very strong. Cold rolled steels are usually used in applications where the material needs to be stronger. Hot rolled steel is less likely to crack or tear than Cold rolled steel.
3.Steel Strength and Hardness
Hot rolled steel is typically softer and weaker than Cold rolled steel. Hot rolled steel is usually used in applications where the material does not need to be very strong. Cold rolled steel is usually used in applications where the material needs to be stronger. Hot rolled steel is less likely to crack or tear than Cold rolled steel.
Cold-rolled steels are typically harder and stronger than Hot rolled steel. Cold rolled steels are usually used in applications where the material needs to be stronger. Hot rolled steel is less likely to crack or tear than Cold rolled steel.
4.Internal Stresses
The strength and hardness of steel significantly influence the internal stress of materials. Therefore, cold-rolled steel with greater strength and hardness has greater internal stress than hot-rolled steel. It is essential to remove this stress before processing the material to prevent the warping of the final product.
In conclusion, Hot rolled steel is more flexible and can be used in various applications. Hot rolled steels are typically used in applications where the material does not need to be very strong. Cold rolled steel is usually used in applications where the material needs to be stronger. Hot rolled steel is less likely to crack or tear than Cold rolled steel. Thanks for reading!
FAQs
Q: What are the types of copper?
A: There are 4 types of copper, pure copper (also known as red copper), brass, bronze, and cupronickel.
Author
Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.