Comparison of Hot Rolling and Cold Rolling of Rolling Mill

Rolling mill refers to the equipment that completes the whole process of rolling material production, including main equipment, auxiliary equipment, lifting, and transportation equipment and auxiliary equipment. However, the so-called rolling mills are often referred to only as of the main equipment.

At present, China’s rolling mill production is divided into hot rolling and cold rolling. The rolling deformation of the rolling equipment below the metal recrystallization temperature is called cold rolling. Generally, the strip steel is directly subjected to rolling processing at room temperature without heating. The strip after cold rolling may be hot, but it is still called cold rolling. The cold rolling production of rolling mill equipment can provide a large number of steel plates and strips with high precision and excellent performance. The most important feature is the low processing temperature.

The main difference between hot rolling and cold rolling of rolling mills is that cold-rolled steel allows partial buckling of the section, so that the bearing capacity after buckling of the bar can be fully utilized; and hot-rolled steel does not allow local buckling of the section. The residual stresses of 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.

Compared with hot rolling production, cold rolling has the following advantages: cold-rolled strip products are accurate in size and uniform in thickness, and the strip thickness difference generally does not exceed O.01-0.03 mm or less, which can meet the requirements of high precision tolerance. Very thin strips (up to 0.001 mm or less) that cannot be produced by hot rolling are available. The surface quality of cold-rolled products is superior, there are no defects such as pitting, hot-pressed iron oxide, etc., which are often found in hot-rolled strip steel, and can produce strips with different surface roughness according to user requirements (gloss or matte surface, etc.) so as to facilitate the processing of the next process. Cold-rolled strip steel rolling equipment has good mechanical properties and process properties (such as higher strength, lower yield limit, good deep drawability, etc.). High-speed rolling and full-continuous rolling can be achieved with high productivity.