Large-diameter straight seam submerged arc steel pipes are mainly responsible for the pipeline transportation of marine and land oil and gas, oil and natural gas, coal, and ore pulp.
The methods and characteristics of international pipe-making technology, the forming methods of large-diameter longitudinal submerged arc welded steel pipes abroad are the UOE method, CFE roll forming method, RBE roll forming method, JCOE forming method, C forming method, PFP step-by-step bending forming method, etc. A brief introduction is as follows:
1. The UOE method first presses the pre-bent steel plate into a U shape in the forming die of the U press, then presses it into an O shape in the forming die of the O press, welds it into a tube, and then expands the overall diameter. The UOE method is the most advanced forming method in the world today. So far, there are nearly 30 sets of such forming welded pipe units in the world. The UOE method is famous for its high production efficiency and good product quality, but it is not expensive and has a large investment scale.
2. The roll-forming machine of the CFE method is composed of a performing frame, a flat roll frame, an edge bending roll, and a small roll frame. Since many identical small roll rolls are set, the track of the edge of the steel plate during the forming process is almost It is straight and avoids the "edge stretching" phenomenon. The forming quality of the CFE method is good, and its product quality is no different from that of the UOF method. The raw material of this method is a hot roll strip steel coil, which is different from other forming methods. It is mainly suitable for the production of large-volume, single-species steel pipes, but it is difficult to produce high-strength thick-walled steel pipes and large-diameter steel pipes.
3. The RBE roll forming method rolls the steel plate between three or four rolls multiple times. The welded pipe produced by this method is close to the UOE welded pipe in terms of performance and reliability. The RBE method has low investment, fast plant construction, moderate output, high flexibility, and strong adaptability to the market. In recent years, this method has been applied in some developing countries. However, due to the lack of support in the middle of the upper roller formed by this forming method, the diameter of the formed steel pipe cannot be less than 508mm (20in) due to the limitation of its rigidity, which reduces the market share. The diameter of many pipes in my country is below 508mm.
4. JCOE forming method, first press the steel plate into a J shape on a hydraulic press, after pressing both sides, it is formed into a C shape by multiple stamping, and finally pressed into an O shape by a semi-O shape upper mold. The product quality of the JCOE method is close to that of the UOE welded pipe, and the price of the operation line is much lower than that of the UOE unit, but its production efficiency is low.
5. The C forming method uses two C forming machines to replace the U press and O press in the UOE unit. The forming process is: the pre-bent steel plate first forms half of the steel plate on the first press, and then presses another press to form half of the steel plate. The other half of the steel plate is formed on the machine to obtain an O-shaped round tube. The welded pipe produced by the C forming method is suitable in size, moderate in output, and low in production line price.
6. The PFP step-by-step bending forming method is to bend the pre-bent steel plate at the end of the press with a smaller step size and more times to gradually bend the sheet metal, and finally form it into a round pipe by a steel pipe seam welding machine. The PFP method has a small amount of reduction each time, so the tonnage of the press is not large, and the investment is also small. This method can form welded pipes with different pipe diameters and different wall thicknesses. The processed diameter can be less than 406mm, and the quality of the produced welded pipes is higher. Well, the yield is moderate.