ERW carbon steel pipe vs Spiral pipe

First, the difference in production process
ERW straight seam electric resistance welded steel pipe is made by continuous roll forming of hot rolled coil, using the skin effect and proximity effect of high frequency current, so that the edge of the coil is hot melted, and pressure welding is performed under the action of the squeeze roller force. Achieve production. Therefore ERW straight seam resistance welding steel

The residual stress of the tube is small, and the residual stress is further released and reduced by heat treatment of the weld, sizing, straightening, water pressure and the like. Practice has proved that the residual stress of the ERW straight seam electric resistance welded steel pipe during storage and use does not affect the steel pipe. Without any welding wire, the weld is physically and chemically identical to the sheet. The quality of ERW straight seam resistance welded steel pipes depends on the quality of the plates.

The steel plates for spiral steel pipes are welded together by the spiral rotating wire of the unit. The steel plates are spirally rotated to make the geometric stress more complicated, and some even reach the yield limit of the steel plate. After the spiral tube is formed, there is a large residual stress, and the residual The stress is tensile stress. When the steel pipe is subjected to internal pressure, the pipe wall also generates a circumferential tensile stress, and the two are superimposed to weaken the bearing capacity of the steel pipe. It is even more insecure during use. The steel sheets are welded together by a welding wire containing chemical components, and bubbles and weld bead cracks are easily generated during the welding process. The weld seam and the base metal are clearly different in physical properties and chemical composition. It is extremely easy to generate a large concentrated stress at the joint between the weld and the base metal. In the process of welding, the heat influence is large and the hardness is high.

Second, the difference in raw materials
The raw materials used in ERW steel pipes are hot rolled coils produced by regular large factories, and their chemical composition and physical properties are relatively stable.

Most of the raw materials used in spiral tube mills are low-grade hot-rolled strips, which are unstable in chemical composition and physical properties, and have many internal defects and impurities. 

Third, procurement costs and procurement difficulties
The spiral steel pipe produced by the large steel pipe plant of the petroleum and petrochemical system has its advantages mainly concentrated on the manufacture of large-diameter steel pipes, and the manufacturing cost is relatively low. However, for small and medium-sized calibers (¢114mm~¢355.6mm), the manufacturing cost is higher, and the average is 8%~15% higher than that of ERW steel.

Large spiral steel pipe plants often do not produce spiral steel pipes of medium and small diameter, which is difficult to purchase. Small and medium-sized ERW steel pipes are very easy to purchase due to the large number of manufacturers.

Fourth, the geometric size of the steel pipe
1. The geometrical dimensions of the ERW steel pipe are of high precision; while the geometrical accuracy of the spiral welded pipe is low, which makes it difficult to dock the welded seams on site.

2. The weld coefficient of the ERW steel pipe is 100%; the weld seam coefficient of the spiral welded pipe is 130%-200%. The weld length of the spiral pipe is much longer than that of the ERW steel pipe, and the defect occurrence rate is also increased simultaneously.

3. The inner weld height of the ERW steel pipe is almost close to zero and is invisible to the naked eye; the inner and outer surfaces of the spiral steel pipe must have a residual height of about 0.3 mm (this is determined by the production process). The weld seam is so high that there is a gap between the steel pipe's anti-corrosion layer (3PE) and the pipe body, which makes the corrosion resistance of the steel pipe greatly reduced.

4. Due to the high weld seam height of the spiral steel pipe, there will be a large disturbance to the high-speed fluid conveyed, increasing the flow resistance and reducing the pipeline transportation efficiency. The inner wall of the ERW steel pipe is smooth, so there is no such problem.

Five, other differences
The anti-squashing performance of ERW steel pipes is higher than that of spiral steel pipes.

Sixth, application comparison
General oil and gas long-distance pipeline design specifications stipulate that spiral submerged arc welded pipes can only be used in Class 1 and Class 2 areas. The United States, Japan, and Germany generally reject SSAW, and think that SSAW should not be used in the main line; SSAW is used in Canada and Italy, SSAW is used in Russia, and SSAW is used in small quantities. Due to historical reasons, most of the domestic trunk lines still use SSAW. .

Urban gas trunk lines generally use ERW steel pipes. For example, Chongqing Gas Group, Foshan Gas Group, Hainan Minsheng Gas Company, Hangzhou Gas Group, Guangzhou Gas Group, Shenzhen Gas Group, Xinao Gas, China Gas, China Resources Gas, Hong Kong and China Gas, Kunhua Gas, Ningbo Chengguang Gas, etc. ERW steel pipes are widely used as pipes for high- and medium-pressure mains of city gas.

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