Large Diameter LSAW Steel Pipe Manufacturing Technology

Large-diameter LSAW steel pipes are mainly responsible for pipeline transportation of marine and onshore oil and gas, petroleum and natural gas, coal and slurry. The manufacturing of Large Diameter Longitudinal Submerged Arc Welded (LSAW) steel pipes involves several key processes and technologies to produce high-quality, large-diameter pipes for various industrial applications.

This article will briefly introduce the process methods and characteristics of international large-diameter LSAW steel pipes pipe making technology.

1. UOE molding method

First, the pre-bent steel plate is pressed into a U-shape in the forming die of a U-shaped press, and then pressed into an O-shape in the forming die of an O-shaped press. Then it is welded into a pipe and the overall diameter is enlarged. The UOE method is one of the most advanced forming methods in the world today. Currently, there are nearly 30 such forming welded pipe units around the world. The UOE method is famous for its high production efficiency and good product quality, but the cost is not high and the investment scale is large.

2. CFE molding method

The row roller forming machine consists of a preforming frame, a flat roller frame, a bending roller and a small row roller frame. Due to the installation of many small rows of identical rollers, the movement trajectory of the edge of the steel plate during the forming process is almost straight. Avoid "edge stretching". The CFE molding method has good molding quality, and its product quality is the same as the UOF molding method. This method uses hot-rolled steel strip coils as raw materials, which is different from other forming methods. It is mainly suitable for producing large-scale, single-variety steel pipes, but it is more difficult to produce high-strength thick-walled steel pipes and large-diameter steel pipes.

3. RBE roll forming method

The steel plate is rolled multiple times between three or four rollers. The welded pipe produced by this method is close to UOE welded pipe in terms of performance and reliability. The RBE method has low investment, fast factory construction, moderate output, greater flexibility, and strong market adaptability. In recent years, this method has been used in some developing countries. However, due to the lack of support in the middle part of the upper roller formed by this forming method, the diameter of the formed steel pipe cannot be less than 508mm (20in) due to its rigidity, thus reducing the market share. The diameter of many pipes in our country is below 508mm.

4. JCOE molding method

First, the steel plate is pressed into a J shape on a hydraulic press. After the edges on both sides are pressed, they are punched into a C shape several times. Finally, it is pressed into an O shape through a semi-O-shaped upper mold. The product quality of JCOE method is close to that of UOE welded pipe, and the price of the operation line is much lower than that of UOE unit, but the production efficiency is lower.

5. C molding method

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

6. PFP step bending method

The steel plate with pre-bent ends is gradually bent on a press in smaller steps and more times, and finally formed into a round pipe by a steel pipe seam welder. The PFP method has a small pressing volume and small tonnage each time, so the press tonnage is not large, so the investment is also small. This method can form welded pipes with different diameters and wall thicknesses. The processing diameter can be less than 406mm, and the quality of the welded pipe produced is better. Yields are good and yields are moderate.