ERW carbon steel pipe vs Spiral pipe

ERW carbon steel pipe vs spiral pipe:

1. the difference between the production process

ERW carbon steel pipe is the hot rolled coil through the continuous roll forming, the use of high-frequency current skin effect and proximity effects, so that the edge of the coil heat fusion, pressure in the squeeze roller under pressure welding to achieve production. Therefore, erw carbon steel pipe residual stress is small, through the weld heat treatment, sizing, straightening, water pressure and other processes, the residual stress to further release and reduce. Practice has proved that erw carbon steel pipe in the storage and use of residual stress on the steel pipe does not affect. Without any welding wire, the weld in the physical properties and chemical composition with the plate exactly the same. The quality of the erw carbon steel pipe depends on the quality of the sheet.

Spiral steel pipe through the unit spiral rotary welding wire welding together, the steel plate through the spiral rotation, so that the geometric stress is more complex, and some even reached the yield limit of the steel plate, the spiral tube after the formation of a larger residual stress, the residual stress is tensile stress. And the steel pipe by the internal pressure, the wall also produce ring tensile stress, the two superimposed, so that the ability to weaken the steel pipe. The use of the process more insecure. The steel plate is welded together by a wire containing chemical composition, and bubbles and weld bead cracks are likely to occur during the welding process. So that the weld and the base metal in the physical properties and chemical composition is clearly different. It is easy to produce great concentration stress in the joint with the base metal. In the welding process, the heat effect is large, and the hardness is high.

2. the difference between raw materials

ERW carbon steel pipe used in the raw materials are produced by the regular hot-rolled coil, chemical composition and physical properties are more stable. 

Most of the spiral pipe plant used for low-grade hot-rolled strip, chemical composition and physical properties and instability, internal defects and impurities more. Only in the oil and petrochemical system within the large spiral pipe manufacturers using regular hot rolled coil to manufacture steel pipe in order to ensure quality and safety.

3. the procurement costs and procurement difficulties

Oil and petrochemical system of large steel pipe production of spiral steel pipe, its advantages are mainly concentrated in large diameter steel pipe manufacturing, manufacturing costs are relatively low. However, for small and medium diameter (Φ114mm ~ Φ355.6mm) of the steel pipe, the manufacturing cost is higher, the average higher than the ERW steel pipe 8% to 15%.

Large spiral steel pipe plant often do not produce small diameter spiral steel pipe, procurement more difficult. Small and medium diameter erw carbon steel pipe, due to the large number of manufacturers, very easy to purchase.

4. the steel pipe geometric size

1) ERW carbon steel pipe geometric size of the higher accuracy; and spiral welded pipe geometry accuracy is low, resulting in on-site construction of the weld weld docking difficulties. 
2) ERW carbon steel pipe weld coefficient is 100%; spiral welded pipe weld coefficient of 130% -200%. The length of the spiral pipe is much longer than that of the ERW steel pipe, and the defect rate is also increased. 
3) ERW carbon steel pipe within the weld is relatively close to zero, the naked eye is not visible; spiral steel pipe inside and outside the surface must be left about 0.3 mm high (which is determined by the production process). The weld is so high that there is a gap between the coating (3PE) and the pipe, which makes the corrosion resistance of the steel pipe greatly reduced. 

4) Due to the existence of spiral steel pipe gap, the transmission of high-speed fluid there will be a large disturbance, increase the flow resistance, reduce the transport efficiency of the pipeline. ERW carbon steel pipe wall is smooth, there is no such problem.