Cold roll forming process is that when the metal strip passes through several pairs of rollers with holes in sequence, the strip is fed forward as the rollers rotate. At the same time, it is continuously bent to obtain a desired cross-sectional shape. It can be seen that roll bending is a continuous bending method.
Cold Roll Forming is a plastic processing method in which the entire length of the strip passes through several different holes in sequence, gradually bending and deforming locally, and the full cross-sectional shape is gradually close to the finished cross-sectional shape, and finally a product with a uniform full-length cross-section is obtained. The pass shape is surrounded by the contours of two or more forming rollers with a certain shape. The cold forming rollers may be horizontal rollers or vertical rollers.
Hole pattern is one of the important factors affecting product quality and productivity. The cold forming roller is installed on the frame. The forming roller responsible for driving the strip forward is driven by the motor through the transmission system. Generally, only the horizontal roller is the active roller, and the vertical roller is often the passive roller. Each machine base is called a cold roll forming machine, each roll forming machine is equipped with two or more forming rollers, and each row of forming unit is composed of more than two forming machines.
In the bending deformation zone of the cross section during the cold roll forming, the outer layer fiber of the bending piece is elongated by the pulling surface, and the inner layer fiber is compressed and shortened. Between the shortening and elongation, there is a layer of fiber with the same length, called the neutral layer, and the arc formed on the cross section is called the neutral line.
As the outer layer is strained to be pulled and compressed, it is easy to cause thinning and deformation. The inner layer is compressive strain, which is not conducive to plastic flow. Besides, the rigid contact of the convex corners of the forming roller makes the metal nowhere to flow, so the neutral layer has to move inward, so the thickness of the bending part is reduced, and the amount of thinning is generally Very small. When determining the thickness and width of the blank, it is considered that the thickness of the strip before and after molding is unchanged, and the sum of the unfolded lengths of the neutral lines in each part (line segment) after molding is equal to the width of the blank.
The material of the corner of the section of the cold-formed steel is cold-work hardened due to the plastic deformation of bending, that is, the strength is increased and the plasticity is decreased. This phenomenon is called the cold-bending effect. If the cold bending effect is used to increase the strength of the component design, 10% to 15% of steel can be saved, and it can also be used as a safety reserve for improving the strength of cold-formed steel components.
Due to the roll forming process, the strip is fed by the active forming roll. Therefore, cold bending forming can be combined with other processes such as welding, perforating, printing, cutting to length, iron wire and paperboard, etc. to form a joint continuous production line.