Cold-rolled sheets and hot-rolled sheets are both coils, but the difference is still big. Generally speaking, cold-rolled coils are made by rolling hot-rolled coils at room temperature and below the recrystallization temperature, including plates. And rolls. Hot-rolled coil: It uses slab (mainly continuous casting billet) as raw material, and after heating, it is made into strip steel by rough rolling mill and finishing mill. Let me introduce the difference between the two!
The difference between cold rolled coil and hot rolled coil
In fact, it is easy to distinguish between the two rolled plates. We can detect the difference with our hands. The surface of the cold-rolled coil has a certain degree of gloss. It feels smooth to the touch, and it feels a bit like a steel cup that we often use to drink water. However, if the hot-rolled coil has not been pickled, its surface and feel are very similar to ordinary steel plates bought in the market. If the surface is rusted, the color of the surface is red, if there is no rust, the color of the surface is purple-black.
In terms of accuracy, the thickness of cold-rolled steel strip is thinner than that of hot-rolled steel strip, and the precision is more precise. Can be accurate to one digit after the decimal point. In terms of size, the thinnest thickness of cold-rolled coils can be made into steel strips of 0.001 mm. The surface quality of cold rolling is superior to that of hot rolling. Cold rolled strip steel can now produce a mirror surface.
Cold rolling refers to rolling below the recrystallization temperature. It is usually rolled under normal temperature conditions. The reason for cold rolling is that when the thickness of the thin strip steel is small to a certain limit (for example, <1mm), it is difficult to maintain and uniform the temperature, and it is also difficult to achieve hot rolling. It is also very difficult to ensure a good shape under the hot rolling conditions, and cold rolling can solve this problem. First of all, cold-rolled coils do not have some problems that require cooling and temperature unevenness, so they can produce coils that are thin and have strict tolerances. In addition, the surface finish of the cold rolled coil is also very high, and it can be given different surfaces according to different requirements.
The biggest advantage of cold rolled coil is that its surface quality and dimensional accuracy are very high. Through the cooperation of cold rolling deformation and heat treatment, it is not only easier to meet the requirements of users for various product specifications and comprehensive performance, but also is particularly beneficial to the production of some important products with special texture and performance.
Due to the hardening during processing, the metal is deformed during the rolling process, the resistance is also increased, and the rolling pressure is also increased. At the same time, the plasticity of the metal is reduced and cracks are easily generated. When the steel type is under certain conditions, the degree of hardening during processing is related to the degree of cold rolling deformation. When the amount of deformation increases, after work hardening exceeds a certain level, rolling cannot be continued. Therefore, after the plate is subjected to a certain amount of total cold rolling deformation, it is often subjected to a softening heat treatment to restore its plasticity and reduce the resistance to facilitate the continued rolling. Under certain rolling conditions, the harder the quality of the steel, the thinner the finished product, and the more rolling process required. Due to work hardening, cold-rolled coils generally require a certain amount of heat treatment before they leave the factory.
