ERW carbon steel pipe
vs spiral pipe
First, 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.
Second, the difference between raw materials 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.
The spiral pipe is welded together by the spiral rotating wire of the unit spiral, and the steel plate is rotated by spiral, which makes the geometric stress more complex, and some even reach the yield limit of the steel plate. The residual stress is larger after the spiral tube is formed and the residual stress is tensile stress. When the steel pipe is subjected to internal pressure, the tensile stress will also be generated on the wall, and the two will superimpose, thus reducing the capacity of the steel pipe. The use of the process is more unsafe. The steel plate is welded through the welding wire containing chemical components, and bubbles and weld cracks may occur during welding. So the physical properties and chemical composition of the weld and base metal are obviously different. It is easy to produce high concentration stress at the joint with the base metal. During the welding process, the heat effect is large and the hardness is high.
Second, the difference between raw materials
The raw material used for ERW carbon steel pipe is produced by ordinary hot rolled coil, and its chemical composition and physical properties are more stable.
Most spiral steel pipe mills are used for low-grade hot-rolled steel strip. Their chemical composition and physical properties are unstable, internal defects and impurities are more. Only large spiral steel pipe manufacturers in petroleum and petrochemical systems can use common hot rolled coil to make steel pipes to ensure quality and safety.
Three is the cost of purchasing and the difficulty of purchasing
The advantages of large steel pipe spiral steel pipe produced by petroleum and petrochemical system are mainly concentrated in the manufacture of large diameter steel pipe, and the manufacturing cost is relatively low. But for medium and small diameter (114mm ~ 355.6mm) steel pipe, the manufacturing cost is higher, the average is 8% to 15% higher than that of ERW steel pipe.
Large spiral steel pipe factories often do not produce small diameter spiral steel pipes, so procurement is difficult. Because of the large number of manufacturers, small and medium diameter ERW carbon steel pipes are very easy to purchase.
Four, the geometry of steel tube
1, the geometric accuracy of the ERW carbon steel pipe is higher; and the geometric accuracy of the spiral welded pipe is low, resulting in the difficulty of butt welding on the spot.
2, the weld coefficient of ERW carbon steel pipe is 100%, and the weld coefficient of spiral welded pipe is 130%-200%. The length of the spiral tube is much longer than that of the ERW steel tube, and the defect rate also increases.
3, the ERW carbon steel pipe in the weld is close to zero, and the naked eye is not visible; the spiral steel tube inside and outside the surface must have a height of about 0.3mm (this is determined by the production process). The weld is so high that there is a gap between the coating (3PE) and the pipeline, which makes the corrosion resistance of the steel pipe greatly reduced.