What Is Cold Rolling

The plastic deformation of the metal is lower than the temperature of the rolling process. Cold rolling production scale, high production efficiency, high degree of mechanization automation, is one of the most important cold processing methods. Since the surface of the raw material is processed before rolling, there is no effect of the production of the scale and the temperature fluctuation of the rolling material during the rolling process. Therefore, the cold rolled product has high dimensional precision, smooth surface and can be rolled out of small size Products and other advantages. In addition, cold rolling results in the work hardening of the material, which improves the strength of the material. The combination of cold rolled material and heat treatment process can improve the comprehensive mechanical properties of the product. Compared with the hot rolling production, cold rolling production process complex, deformation of the energy consumption, high production costs. Cold-rolled products can be divided into cold-rolled strip, cold-rolled pipe and cold-rolled profiles according to the cross-sectional shape. Which is the most widely used cold-rolled strip.

Cold rolling is usually done by longitudinal rolling. Cold rolling production processes generally include raw material preparation, rolling, degreasing, annealing, finishing and so on. Cold rolling to hot-rolled products as raw materials, raw materials before cold rolling to be descaled to ensure that the surface of cold-rolled products clean. Rolling is the main process of deformation of the material. The purpose of degreasing is to remove the rolling oil attached to the rolling material, so as not to contaminate the surface of steel contamination, stainless steel also to prevent carbon. Annealing includes intermediate annealing and finished heat treatment. Intermittent annealing is achieved by recrystallization to eliminate the work hardening caused by cold deformation to restore the plasticity of the material and to reduce the deformation resistance of the metal. The purpose of the finished product heat treatment is to eliminate hardening by recrystallization. But also in accordance with the technical requirements of the product to obtain the required organization and product performance. Finishing includes inspection, cutting, straightening, printing, sorting and packaging. Cold rolled products have a high packaging requirements to prevent the product from being scratched during transport. In addition to the above process in the production of some special products, there are their own special processes. Such as rolling silicon steel plate, in the cold before the decarburization annealing, rolling after the film, high temperature annealing, stretching straightening and tempering.

The rolling mill for cold-rolled strip steel has two-high rolling mill, four-high rolling mill and multi-roll mill. The most widely used is the four-roll mill. Rolling thinner products will use multi-roll mills. Many types of multi-roll mill, such as six-roll mill, eight-roll mill, twelve rolling mill, twenty-roll mill. With the improvement of the board shape requirements, the development of a number of improved plate-shaped technology, such as bending roll technology, roll roll technology and cross roll technology. Cold-rolled strip mill according to the rack can be divided into stand-alone reversible or irreversible and multi-machine continuous two categories. The former is suitable for multi-species, small batch or alloy steel products, the proportion of large cases. It invests low, builds fast, but yields low, metal consumption is large. Multi-rack continuous rolling is suitable for product varieties than single or little change in the situation, it has high production efficiency, the advantages of large output, but the investment is greater. Compared with hot-rolled strip, cold-rolled strip rolling process has the following characteristics: (1) the use of process lubrication and cooling to reduce the deformation resistance during rolling and cooling roll; (2) the use of large tension rolling, To reduce the deformation resistance and to maintain the stability of the rolling process. Using the average unit tension value of the material yield strength of 10% to 60%, generally not more than 50%; (3) the use of multi-rolling rolling. As the cold rolling of the material to produce hardening, when the total deformation of 60% to 80%, continue to become difficult to deformation. For this to be intermediate annealing, so that the material softened after rolling to continue. In order to obtain the required strip steel, such an intermediate annealing may be carried out several times. Rolling between the two intermediate annealing is called a rolling process. The annealing of the cold-rolled strip is carried out in a continuous annealing furnace or a hood-type annealing furnace with a protective gas. The minimum thickness of the cold rolled strip can now reach 0.05mm, cold rolled foil can reach 0.001mm.

Cold rolling is to obtain high-precision thin-walled tube, thick-walled tube and special thick-walled tube and shaped pipe, variable cross-section pipe and other important production methods. Cold rolled steel pipe in a variety of rolling mill unit, the most widely used is the two-roll and multi-roll cycle cold-rolling machine.

Dimensional accuracy or strength requirements of high profile products can be hot-rolled materials as raw materials used to produce cold-rolled method.

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