The forming process methods of large-diameter longitudinally welded pipes（LSAW) mainly include: UOE forming method, JCOE forming method, CFE row roll forming method, RBE roll forming method and C forming method, etc. They are briefly introduced as follows:

1. UOE forming method: After planing or milling the wide and thick steel plate (welding the pilot arc plate before milling), pre-bend the edge on a pre-bending machine, press it into a U-shape on a U-shaped press, and then It is pressed into an O-shaped tube on an O-shaped press. After pre-welding, the tube is sent to several welding lines to weld the inner and outer grooves to form steel pipes. The steel pipe is expanded and sizing, and the dimensional accuracy is improved. After the welding seam passes various inspections, the inner and outer surfaces are coated with an anti-corrosion layer. UOE process equipment chooses steel plate milling machine, pre-bending machine, U-shaped press, O-shaped press, pre-welding machine, internal and external welding machine, pipe expanding machine, non-destructive testing equipment, hydraulic testing machine and internal and external coating of pipe and tube Equipment etc.

2. JCOE forming method: After the steel plate is pre-bent at the end by the pre-bending machine, half of the steel plate is gradually pressed from one side into a J-shape, and then the other half is gradually pressed into a C-shape from one side. After the middle pressing An O-shaped open tube blank is formed, which is welded by a steel pipe welding pre-welding machine, and then welded by an automatic submerged arc welding internal and external welding machine to form a steel tube.

3. CFE row-roll forming method: the row-roll forming machine is composed of a pre-forming frame, a flat roll frame, an edge bending roll and a small-row roll frame. Since many small rows of the same rollers are set, the steel plate is formed during the forming process. The trajectory of the edge is almost straight, avoiding the phenomenon of "edge stretching". The forming quality of CFE method is good, and its product quality is no different from UOF method. This method uses hot rolled strip steel coils as raw materials, which is different from other forming methods. It is mainly used for the production of large-scale, single-quality steel pipes, but it is difficult to produce high-strength thick-wall steel pipes and large-diameter steel pipes.

4. RBE roll forming method: During roll forming, the steel plate is rolled between three or four rolls for many times. The welded pipe produced by this method is close to UOE welded pipe in terms of performance and reliability. RBE method The investment is small, the output is moderate and the flexibility is large, and it is adaptable to the market.

5. C forming method: replace the U press and O press in the UOE production line with two C forming machines. The forming process is: the pre-bent steel plate is first formed into half of the steel plate on the first press, and then The other half of the steel plate is formed on the other side of the press to obtain an O-shaped round tube. The welded pipe produced by C forming method is of suitable size, moderate output, and the production line price is low.

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