Rectangular tube hole design of rectangular tube

When it is necessary to produce several shaped tubes, and the size of the strips used is allowed to be uniform (such as several kinds of hollow steel window tubes), only one set of forming rolls is needed , and then the rolls are changed on the shaping frame (the sizing frame of the round tube). Different sections are available, making it easy to change the variety and reducing the processing and storage of the rolls.
　　The production process of the rectangular tube which is formed by welding first is mainly formed by the sizing frame, and the sizing machine is generally a two-roll mill, which has a horizontal frame and a vertical roll frame. At present, there are two main types of rectangular tube hole design:


　　One is that the horizontal frame is designed according to the box-shaped hole, the first frame is an elliptical hole, the other frames are approximately rectangular holes, the hole-shaped section is composed of an arc, and the radius of the arc is increased by frame, and the side walls of all the holes are The fillet radius at the junction with the bottom is equal to the fillet radius of the finished section. The total elongation coefficient of the rectangular tube is about 1.05, which is mainly distributed on the flat roller. The deformation of the vertical roller is small, and its function is to press down the short side of the rectangular tube. With this design method, the calculation is complicated, and the calculated value is not accurate enough, and the circumference of the hole type needs to be constantly corrected.


　　The other is designed by using the deformation angle. The circular tube to the rectangular tube can be seen as a bending deformation from an angle of 180° to 90°, so the deformation angle θ can accurately reflect the degree of deformation of the corner and the side. In the design process, considering the dimensional accuracy and the effect of metal work hardening, the distribution of the deformation angle is usually larger at the beginning and the middle, and then gradually decreased. In a hole type formed by directly intersecting a circular arc, the rounded portion of the tube blank may not be filled with a hole type, and thus the circumference of the hole type may be different from the circumference of the tube blank . In order to ensure the dimensional accuracy, the hole shape of the hole type needs to be corrected. Therefore, this method has higher design accuracy than other methods. However, due to the large amount of iterative calculations, this method is more suitable for the hole design with a computer. If you use a universal frame that is deformed horizontally and vertically, you can directly design the hole shape with the deformation angle θ.