2020-02-27
Hot rolling and cold rolling are the two main process for the most steel or steel plate making, which have great influences on the structure and properties of the steel. A better rolling mill roll will bring more superior quality steel. Which one is better between the hot rolled steel and cold rolled steel? And what’re the differences and how to distinguish? These questions are always people being concerning about.
Firstly, we introduce some information about the hot rolled steel and cold rolled steel
Hot Rolled Steel
Definition
Hot rolled steel is the finished product through directly processed on the steel mold in the steel furnace with exceptionally high temperatures, rolling with the hot mill roller which can make sure the dimensions of the steel sheet according to the requirements., then coiled and cooling. The main steel rolling type is hot rolling.
Advantages
Compact the steel structure and improve the mechanical properties.
Disadvantages
1.After hot rolling, delamination occurs, when the non-metallic inclusions in the steel are pressed into thin sheet. Delamination greatly deteriorates the tensile properties of the steel.
2. Residual Stress caused by uneven cooling. Residual stress is an internal self-phase equilibrium stress without external force. Hot rolled steel may have negative effects on deformation, stability, fatigue resistance, etc.
Cold Rolled Steel
Definition
The cold rolled steel bar is obtained by cold working of the hot-rolled steel, such as cold drawing and stretching at a normal temperature. Cold rolling is often used for the production of small sections and steel sheets.
Advantages
Cold rolled steel bar has fast forming speed and high output. It can be made into a variety of cross-sectional forms to meet the requirements of the different use conditions. Cold rolling can make the steel have a large plastic deformation.
Disadvantages
Torsion is prone to occur under bending. Bending and torsional buckling is easy to occur under compression. So the torsional performance of cold rolled steel is poor, and the ability to withstand concentrated loads is weak.
How to Distinguish Hot Rolled Steel From Cold Rolled Steel
1. Carbon Content
The carbon content of hot-rolled steel can be slightly higher than that of cold-rolled steel. The density is the same when there are little differences in the components
2.Density
The density and composition of hot rolled steel can be checked through looking for various steel to find the specific one.
Cold rolled steel has high hardness and relatively has difficult for processing, but it is not easy to deform and has high strength.
3. Production Process
The production process of hot-rolled steel and cold-rolled steel is different. Hot rolling steel is rolled at high temperature and cold rolling steel is processed from hot rolled steel at normal temperature. Generally speaking, cold rolled steel has better strength and hot rolled steel has better ductility.
What Are The Differences Between Hot Rolled Steel And Cold Rolled Steel
1.The Surface
The cold steel plate is cold rolled and the surface has no oxide scale with good quality. The hot steel plate uses hot rolled processing technique with oxide scale on the surface.
2. Toughness & Stretchability
Hot rolled steel has poor toughness and the price is low, while cold rolled steel has good stretchability and toughness, but the price is more expensive
3.Mechanical Properties
The cold rolled steel has much better mechanical properties than hot rolled steel.
4. Formability
Since the surface of cold rolled steel is better than hot rolled one, the forming effect also better than that of hot rolled steel.
5. Torsion resistance
Hot rolled steel has higher free torsional stiffness than cold-rolled steel, so the torsional properties of hot-rolled steel are better.
6. Smoothness
The smoothness of cold rolled steel sheet is better than that of hot rolled sheet.
Overall, cold rolled steel has better performance than hot rolled steel, but cold rolling process will cost more and the cold rolled steel has higher price than that of hot rolled one. People should choose the suitable one according to their needs. No matter what types of the rolling is, the mill rolling process plays an important role in steel making and mill roll is essential for the perfect dimensions.
Maybe different people have different views on hot rolled steel and cold rolled steel. Hope the simplified explanation will help people learn more about the two types of steel or steel plate.
