Hot-Rolling and Cold-Rolling Steel Pipe
The differences between hot-rolled and cold-rolled steel relate to how the metals are processed at the mill and not the grade or specification of the product. Steel pipe manufacturing significantly impacts how and for which application many industries will use. With their different properties, cold-rolled and hot-rolled steel products determine their impact on the end product. Steel with varying specifications or grades can be manufactured through either cold-rolled or hot-rolled processes.
Quick Reference For The Differences Between Hot-Rolled Steel And Cold-Rolled Steel
| Hot-Rolled | Cold-Rolled |
|---|---|
| Used For Agricultural Equipment, Automobile Parts, Construction Materials, Railroad Equipment, Anything Requiring A Lesser Degree Of Precision | Used For Aerospace Structures, Home Appliances, Metal Furniture, Structural Parts, Anything Requiring High Precision |
| Lower Tensile Strength (~67,000 PSI) | Higher Tensile Strength (~85,000 PSI) |
| Less Control Over End Result, Lower Dimensional Accuracy | High Dimensional Accuracy |
| Rougher Surface Characteristics | Smoother, Shiny Surface Characteristics |
| High-Temperature Process (Above 1700 Degrees Fahrenheit), Less Control When It Cools Down | Room Temperature Process, More Control Over Shape Since It Does Not Have To Cool Down |
| Less Expensive To Manufacture | More Expensive To Manufacture |
Hot-Rolled Steel Manufacturing Process
Hot-Rolling steel is the process of steel manufacturing through very high heat, generally separated into low, medium, and high-pressure boiler steel pipes. Hot-rolled steel has been roll-pressed at high temperatures of over 1,700 degrees Fahrenheit. During this process, the metal is more malleable and easier to work with. Manufacturing begins with a large, rectangular piece of metal called a billet. The billet is heated and formed into a roll. While it is at a high temperature, it is run through a series of rollers until the desired dimensions are reached. Hot-rolled steel is cooled with water after it has been processed and will shrink slightly while it cools, meaning its final form is not as precise as cold-rolling is.
Identifying Hot-Rolled Steel
- Scaly Surface due to the sudden change in temperature during the cooling process
- Rounded Edges Or Corners due to cooling process and shrinkage
- Slightly Distorted due to cooling process and shrinkage
Cold-Rolled Steel Manufacturing Process
Cold-rolling steel is technically done below 1,700 degrees Fahrenheit, but most of the time it is done at room temperature. The steel is compressed through rollers at room temperature, increasing the metal's strength and hardness. Cold-Rolled steel often improves corrosion resistance along with improving its surface finish. This process takes longer because the steel is originally Hot-Rolled before being processed further, i.e., Cold-Rolled. This means that Cold-Rolled Steel takes about double the time Hot-Rolled Steel does.
Identifying Cold-Rolled Steel
- Smooth And Shiny Surface due to rolling happening at room temperature; thus no cooling process is required afterward
- Well-Defined Corners And Edges due to rolling happening at room temperature
- Closer Tolerances due to lack of cooling process and shrinkage
