When it is necessary to produce several profiled tubes and the size of the strip used allows unification (eg several types of flat steel window tubes), only one set of profiled rolls is required and then a roll changeover is performed on the shaping frame (tube sizing frame) to get different sections, so that the replacement of the species is very simple and can greatly reduce the roll processing and reserves.
After welding, the process of the rectangular tube
production process is mainly completed by the sizing frame, sizing machine is generally two-roll mill, which has a horizontal rack and vertical roll rack. At present, there are two main types of rectangular tube hole design:
One is the horizontal frame according to the box hole design, the first frame is oval hole, the other frame is approximately rectangular hole, the hole section is composed of circular arc, and the arc radius increases by the rack, all the side walls of the hole. The fillet radius at the bottom is equal to the fillet radius of the finished section. The total extension factor of the rectangular tube is about 1.05, which is mainly distributed on the flat roller. The deformation of the vertical roller is very small. Its function is to depress the short side of the rectangular tube. Using this design method, the calculation is more complex, and the calculated value is not precise enough, the need to constantly modify the perimeter of the hole.
The other is to use the design of deformation angle, from the tube to the rectangular tube can be seen as a 180 ° to 90 ° angle of bending deformation, so the deformation angle θ can accurately reflect the corner and the edge of the degree of deformation. In the design process, considering the dimensional accuracy and the influence of metal work hardening, the distribution of deformation angle is usually larger than the middle pass, and then gradually decreases. In the intersection of circular arc directly formed in the hole type, the rounded part of the tube can not fill the hole, so the perimeter of the perforation and the perimeter of the tube unequal. In order to ensure the dimensional accuracy, the hole fillet part needs to be corrected and calculated. So this method has higher design accuracy than other methods. However, due to the large amount of iterative computation, this method is more suitable for computer-based pass design. If the use of horizontal and vertical deformation of the universal rack, the deformation angle can be directly used for hole design.