1. FFX molding (flexible molding).
New technology improved based on FF molding technology by Japan's Nakata Machinery Manufacturing Research Institute. The deformation is focused on the edge of the rough forming section so that the edge bends to about 30% of the width of the steel strip, and at the same time, more than 80% of the total deformation of the steel strip is uniformly completed in the rough forming section, and each forming roll in the rough forming section The pass patterns adopt a set of continuously changing multi-curvature curves, which contain the pass patterns that can be produced for welded pipes so that only one set of forming rolls can produce products of different specifications, which reduces the number of forming stages and roll changing time.
2.TPF three-point bending forming.
According to the law of transformation of longitudinally welded pipes, the partial forming method is adopted. The first step uses "W" to shape the edge of the strip; the second horizontal roll bends the middle of the strip to make the strip a "U" shape; the third horizontal roll is curved "U" The two straight sides of the ”shape make it close to the double-radius section and send the strip steel to the vertical roll formation for rounding deformation.
The edge of the steel plate is pre-bent as required and then molded by a U-forming machine and O-forming machine twice. The circumferential compression deformation (0.2%~0.4%) occurs in the O forming so that the circumferential residual stress of the open pipe is evened. Then the O-shaped tube blank is welded and then cold expanded. It is characterized by large production capacity, with an annual production capacity of 300 to 1 million tons, which is suitable for single-scale mass production and a relatively large investment.
The progressive bending pressure forming first presses one half of the steel plate into a J shape and then presses the other half of the steel plate into a J shape. After multiple compressions, a C shape is formed, and finally, an open O-shaped tube is formed from the middle. Then expand the diameter of the O tube after cooling. The steel pipe has great flexibility in production, which is especially suitable for the production of medium-diameter thick-walled pipes with less investment.
5. RB forming (roll forming).
The steel plate is rolled and bent many times between three rollers and four rollers, and finally bent into the required cylindrical shape. This process appeared earlier and is mostly used to produce pressure vessels, structural pipes, and water pipes with larger outer diameters (up to 4500mm) and shorter lengths (3~6m), with poor dimensional accuracy and lower productivity.
6. Spiral welded pipe is formed in front swing type.
The steel belt in front of the former swings as a whole to adjust the forming angle. The unit does not have loops and occupies a small area, but it can only produce intermittently (roll-to-roll or stop at opposite ends).
7. Spiral welded pipe back swing forming.
The steel pipe bridge swings after the former to adjust the forming angle. Usually, there are loopers to ensure continuous production, occupying more land, and more equipment.