Manufacturing Technology of Large Diameter LSAW Steel Pipe

Large-diameter LSAW steel pipes are mainly responsible for the pipeline transportation of marine and terrestrial oil and gas, oil and natural gas, coal and ore pulp, etc., especially suitable for the "West-East Gas Transmission" project currently under construction in China, and can also be used for export and substitute imports . Germany SMSMEER (formerly famous international Mannesmann) company, Japan NKK company, Japan OTK (Osaka Special Steel Tube Plant), India WELSPVN pipe manufacturing company, South Korea Hyundai Heavy Industries and Seiya company all have their own unique pipe making technology, They are all elites in the international management industry.

Process methods and characteristics of international pipe-making technology. The forming methods for producing large-diameter LSAW steel pipes abroad include: UOE forming method, CFE row roll forming method, RBE roll forming method, JCOE forming method, C forming method, PFP gradual folding Bending forming method, etc. A brief introduction is as follows:
1. UOE molding method
First, the pre-bent steel plate is pressed into a U shape in the forming die of the U press, and then pressed into an O shape in the forming die of the O press, and then welded into a tube and then the overall diameter is expanded. The UOE method is one of the most advanced forming methods in the world today. So far, there are nearly 30 sets of such forming welded pipe units in the world. The UOE method is known for its high production efficiency and good product quality, but it is not expensive and has a large investment scale.

2. CFE molding method
The row roll forming machine is composed of a pre-forming stand, a flat roll stand, an edge bending roll and a small row roll stand. Due to the installation of many small rows of the same rolls, the trajectory of the edge of the steel plate during the forming process is almost straight. Avoid "edge stretch" phenomenon. CFE molding method has good molding quality, and its product quality is no different from UOF molding method. This method uses hot rolled strip steel coils as raw materials, which is different from other forming methods. It is mainly suitable for the production of large-scale, single-variety steel pipes, but it is difficult to produce high-strength thick-wall steel pipes and large-diameter steel pipes.

3. RBE roll forming method
The steel plate is rolled into several times between three or four rolls. 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 plant construction, moderate output and greater flexibility, and is highly adaptable 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 roll formed by this forming method, due to its rigidity, the diameter of the formed steel pipe cannot be less than 508mm (20in), which reduces the market share. Many pipelines in China have a diameter below 508mm.

4. JCOE molding method
First, the steel plate is pressed into a J shape on a hydraulic press. After pressing the edges on both sides, it is stamped into a C shape by several times. Finally, it is pressed into an O shape by a semi-O shape upper die. 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 its production efficiency is low.

5. C molding method
Use two C forming machines to replace the U and O presses in the UOE unit. 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 steel plate is formed on the other press The other half to get an O-shaped round tube. The welded pipe produced by C forming method is of suitable size, moderate output, and low price of production line.

6. PFP stepwise bending method
The steel plate with the end pre-bent is gradually bent on the press with smaller steps and more times, and finally formed into a round pipe by a steel pipe seam welding machine. The PFP method has a small tonnage due to the small amount of reduction per time, so the tonnage of the press is not large, so 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 welded pipe produced is better. Good, moderate yield.

Tips: Straight seam steel pipe is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. Straight seam steel pipes can be divided into high-frequency straight seam steel pipes (ERW) and submerged arc welded straight seam steel pipes (LSAW) according to the production process. Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development.

In case ASTM A53 Grade B in ERW (electric resistance welded) pipe, the weld seam of A53 ERW pipe shall be done the heat treatment with a minimum 1000°F [540°C]. In this way the no untempered martensite remains.
In case ASTM A53 B pipe in cold expanded, then expansion should not exceed 1.5% of the required OD.