What is the recrystallization temperature of steel

Difference Between Hot Rolled and Cold Rolled Steel

Key difference - hot rolled vs cold rolled steel

Steel is a metal alloy that, along with other elements, is made from iron. Steel is widely used around the world due to its high strength and low cost compared to other types of metals and metal alloys. Steel can be found in various shapes and names according to the elements it contains, according to the production method, application, etc. Hot rolled steel and cold rolled steel are two types of steel named according to the production method. Rolling is a type of processing method used in mills that make steel. The rolling is carried out in order to reduce the thickness of the steel and to make this thickness uniform. The main difference between hot rolled and cold rolled steel is that hot rolled steel is made at high temperatures while cold rolled steel is made at room temperature.

Key areas covered

1. What is hot rolled steel?
- Definition, production and use
2. What is cold rolled steel?
- Definition, production and use
3. What is the difference between hot rolled and cold rolled steel?
- Comparison of the main differences

Key Terms: Cold Rolled Steel, Hot Rolled Steel, Metal Alloy, Mills, Rollers, Steel

What is hot rolled steel?

Hot rolled steel is a type of steel made by rolling steel at very high temperatures. In the manufacture of this steel, the steel is passed through rollers at temperatures in excess of 1700 ° F. This temperature is the recrystallization temperature of most steels. Recrystallization of steel is the replacement of deformed steel grains with flawless grains.

At temperatures higher than the recrystallization temperature of steel, the steel can be easily manufactured; the products made from this steel are also easy to process. Hot rolled steel is usually cheap. This is because hot rolled steel requires less processing and is made with no delays in the process. However, when the steel cools, it shrinks slightly. Then the size of the final product cannot be easily controlled. Therefore, hot rolled steel is used when slight differences in shape and size are not taken into account.

Figure 1: Production of hot rolled steel

When making hot rolled steel, the starting material is a large metal cube called a billet. This block is first heated and passed through a roller to make a large steel roller. Then this large steel roller is passed through several rollers while its temperature is kept above the recrystallization temperature. Different forms of hot-rolled steel can also be produced here by slightly changing the process. For example, in order to obtain the steel as incandescent strands, steel is pushed through the rollers at high speed.

What is cold rolled steel?

Cold rolled steel is a type of steel made by rolling steel at temperatures as low as room temperature. Cold-rolled steel is manufactured at temperatures below the recrystallization temperature of steel.

Cold rolled steel is mostly made from the further processing of hot rolled steel. Here the steel is further processed in cold reduction mills. When hot rolled steel is cooled to room temperature, these steel rolls are compressed between rolls.

Cold rolling is the process of forming steel with more precise sizes and shapes. In the manufacture of steel bars, steel is not fed through rollers, but drawn and can include other processing steps such as turning, grinding or polishing.

Figure 2: Cold rolled carbon steel

Cold rolled steel therefore gives a perfectly finished surface with correct dimensions. However, cold rolled steel products are more expensive than other steel products due to complicated processing methods. However, cold rolled steel products are more preferred for several reasons. For example, bars made by this process are square with well-defined corners and edges, and the products are smooth and oily to the touch.

Difference between hot rolled and cold rolled steel

definition

Hot rolled steel : Hot rolled steel is a type of steel made by rolling steel at very high temperatures.

Cold rolled steel: Cold rolled steel is a type of steel made by rolling steel at temperatures as low as room temperature.

temperature

Hot rolled steel : Hot rolled steel is made at temperatures in excess of 1700 ° F.

Cold rolled steel: Cold rolled steel is produced at temperatures such as room temperature or below.

costs

Hot rolled steel : Hot rolled steel is comparatively cheap.

Cold rolled steel: Cold rolled steel is expensive compared to hot rolled steel.

Services

Hot rolled steel : Hot rolled steel is used when precise dimensions of the final product are not required.

Cold rolled steel: Cold rolled steel provides the exact dimensions and precisely defined edges.

disadvantage

Hot rolled steel : Hot rolled steel yields products with sizes slightly different from the required dimensions.

Cold rolled steel: The Production costs are high due to advanced processing methods.

Conclusion

Hot rolled steel and cold rolled steel have different uses depending on their properties. Both are types of steel, but differ from each other in terms of the production process. The main difference between hot rolled and cold rolled steel can be stated as hot rolled steel is made at high temperatures while cold rolled steel is made at room temperature.

References:

1. Done, Brad. Reliance Foundry, Reliance Foundry Co. Ltd., July 26, 2017 bollard, available here. Accessed September 25, 2017.
2. "Rolling (metalworking)". Wikipedia, Wikimedia Foundation, September 11, 2017, available here. Accessed September 25, 2017.

Image courtesy:

1. "1568604" (Public Domain) via Pixabay
2. “Carbon Steel Cold Rolled Sheet Coil” by Jatinsanghvi - Own work (CC BY-SA 3.0) via Commons Wikimedia