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Method of welding steel pipe forming 1


1.Single radius forming method.

The single-radius roll forming method has three types: circumferential bending forming method, edge bending forming method, and center bending forming method. The single radius forming method is: the hole pattern is composed of a single radius, the horizontal rollers and vertical rollers of the forming machine are alternately arranged, and the strip steel Passing between the horizontal roller and the vertical roller, the flat plate is gradually bent into a round tube.


2.Circumferential bending forming method.

The entire width of the strip is bent and deformed at the same time, and the bending radius of each frame is gradually reduced; the edge bending method is to bend from the edge of the strip, with a constant bending radius, and gradually increase the deformation angle to reduce the middle part of the strip. The width until the steel strip is closed in a circle; the central bending forming method starts from the central part of the strip to be bent and deformed, with a constant bending radius, and gradually expands to the edges on both sides until it is closed in a circle.


3. Double radius forming method (comprehensive bending forming method).

Two or more basic deformation methods are used for combined deformation, but edge forming method + circumferential forming method is more widely used. The forming method of comprehensive deformation of the edge and the circumference of the tube blank uses the squeeze roll hole radius or the radius of the finished tube as the edge bending radius to bend the edge of the steel strip to a certain deformation angle, and the subsequent forming orders remain unchanged. The bending forming of the middle part of the strip is distributed according to the circumferential bending forming method. The method has a relatively stable molding process, uniform deformation, relatively small edge elongation, and good molding quality.


4.W molding method.

The first frame or the first frames of the rough forming section are formed by W reverse bending. The edge part of the strip is bent forward, and the middle part is reversely bent, which increases the arc length of the edge part so that the edge is fully deformed. The tube blank is in the forming process The height difference is small, which greatly reduces the relative extension of the edge, avoids bulging caused by the longitudinal extension of the edge, and reduces the difference in circumferential speed.


5.Roll forming.

To avoid the relative extension and longitudinal spring back deformation of the strip steel during strip forming on the general continuous forming unit, many small rollers are continuously arranged between the horizontal forming rolls to replace the general horizontal forming rolls, so that the strip edges can be Follow a smooth natural deformation path. These small rollers mounted in a cage frame become row rollers. The general roll forming machine consists of one pre-bending roll, one set of roll arranging devices, and two finishing rolls. Suitable for forming thinner-wall steel pipes.


6.CTA molding.

It is a kind of roll forming. Developed by the Austrian Steel Union in 1987. The tube forming system is composed of 4 general pre-bending frames, a bending frame, and a special CTA device. The CTA device consists of many rows of rollers. After passing through the forming machine, the steel strip is continuously and smoothly rolled into a slotted tube with an opening of about 32°. This is the row-roll forming process and finally enters the finishing rolling stand. Finish forming is completed in the finishing pass with guide ring. The high degree of automation of frame adjustment is a method of straight edge forming technology. The first three parts can be shared, which can save roll changing time, reduce roll consumption, and improve production efficiency.


7.FF molding.

In the mid-1980s, it was developed by Japan's Nakata Machinery Manufacturing Institute. The rough forming section always shares a set of cold-formed forming rolls to complete various specifications produced by the unit. The precision forming section is the same as the traditional precision forming frame. The rough forming longitudinal deformation adopts the downhill method. The first frame of the horizontal frame is of the Whole type, and the subsequent frames are of double radius hole type. The bending of the edge and its vicinity is realized by forming rolls with involute curvature, that is, steel pipes with different outer diameters are rolled with the same set of forming rolls with different radii of curvature. Both the horizontal frame and the vertical roll frame have 3 degrees of freedom so that the tube blank always maintains a good edge bending during the forming process, and the middle bending is realized by the edge bending force and the middle assist roller. This method has low deformation pressure, good forming quality, and easy welding. 




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