Cold rolling is usually carried out by means of longitudinal rolling. Common products include cold-rolled steel sheets and Cold Rolled Steel Coil. The cold rolling production process generally includes raw material preparation, pickling, rolling, degreasing, annealing (heat treatment), finishing, and the like. Cold rolling uses hot rolled products as raw materials. Before cold rolling, the raw materials must be dephosphorized to ensure the surface of the cold rolled products is clean. Rolling is the main process of deforming materials. The purpose of degreasing is to remove the lubricating grease attached to the rolled material during rolling to avoid contamination of the steel surface during annealing, and to prevent carbonation in stainless steel. Annealing includes intermediate annealing and finished heat treatment. Intermediate annealing is to eliminate the work hardening caused by cold deformation by recrystallization to restore the plasticity of the material and reduce the deformation resistance of the metal. The purpose of heat treatment of the finished product is to eliminate hardening by recrystallization. It also depends on the technical requirements of the product to obtain the desired tissue (such as various textures, etc.) and product properties (such as deep drawing, electromagnetic properties, etc.). Finishing includes inspection, cutting, straightening (flattening), printing, sorting and packaging. Cold rolled products have high packaging requirements to prevent the surface from being scratched during transport. In addition to the above procedures, there are special processes for producing some special products. For example, when rolling a silicon steel sheet, decarburization annealing is performed before cold rolling, and after coating, coating film, high temperature annealing, stretch straightening (see tension straightening), and tempering are performed.
Cold Rolled Steel Coil
The rolling mill for cold rolled strip has a two-roll mill, a four-roll mill and a multi-roll mill. The most widely used is the four-high mill. Rolling thinner products requires a multi-roll mill. There are many types of multi-roll mills, such as a six-high mill, a partial eight-roll mill, a twelve-roll mill, a twenty-roll mill, etc. (see rolling mill). As the requirements for the shape of Cold Rolled Steel Sheet have increased, many techniques for improving the shape of the plates have been developed, such as bending roll technology, roll rolling technology and cross roll technology. Cold-rolled strip mills can be divided into two types: single-machine reversible or irreversible and multi-machine continuous. The former is suitable for large varieties, small batches or large proportions of alloy steel products. It has low investment and fast construction, but its output is low and metal consumption is large. Multi-stand continuous rolling is suitable for the case where the product variety is relatively single or has little change. It has the advantages of high production efficiency and large output, but the investment is large.
Compared with hot rolled strip (see hot strip rolling steel production process, hot rolled narrow strip steel production), the cold rolling strip rolling process has the following characteristics:
(1) Using process lubrication and cooling to reduce deformation resistance during rolling and cooling the rolls;
(2) Use large tension rolling to reduce deformation resistance and maintain the stability of the rolling process. The average unit tension value used is 10% to 60% of the yield strength of the material, generally not exceeding 50%;
(3) Multi-roll rolling is used. Since cold rolling causes work hardening of the material, when the total deformation amount reaches 60% to 80%, it becomes difficult to continue the deformation. For this purpose, an intermediate annealing is carried out to soften the material and the rolling is continued. In order to obtain the required thin strip, such intermediate annealing may be performed multiple times. The rolling between the two intermediate anneals is called a rolling pass. The annealing of the cold rolled strip is carried out in a continuous annealing furnace or a bell annealing furnace with a protective gas (see cold rolled strip annealing). The thickness of the cold-rolled strip can be as low as 0.05 mm and the cold-rolled foil can reach 0.001 mm.
The above is the Galvanized Steel Sheet Manufacturer's description of the cold rolling process, I hope to help everyone.