Difference between saw and erw pipe

First, difference between the production process
ERW 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 plate edge of the hot melt, squeezing the roller pressure to the role of pressure welding achieve production. Therefore, the residual stress of the erw pipe is small, and the residual stress is further released and reduced through the processes of heat treatment, sizing, straightening and water pressure of the weld. Practice has proved that, erw pipe in the storage and use of residual stress on the pipe does not affect. Without any wire, the weld is physically and chemically identical to the plate. The quality of the erw pipe depends on the quality of the sheet.

SAW pipe through the unit screw spiral welding together, the plate through the spiral rotation, so that the geometric stress more complex, and some even reached the yield limit of the steel, spiral pipe after the formation of a larger residual stress, the residual stress is tensile stress. The steel by the internal pressure, the wall also produces a circumferential tensile stress, the two superposition, so that steel can withstand capacity weak. More insecure during use. Steel plates are welded together by a wire with a chemical composition that is prone to air bubbles and weld bead cracks during the welding process. So that the weld and base metal in the physical properties and chemical composition of the apparent difference. Easily in the weld with the base metal joints have a great concentration of stress. In the welding process, thermal effects, and high hardness.

Second, difference between raw materials
The raw materials used by erw pipe are all hot-rolled coils produced by regular manufacturers with relatively stable chemical composition and physical properties.

Most of the raw materials used in the spiral pipe mill are low-grade hot-rolled steel strip, with unstable chemical composition, physical properties and internal defects and impurities. 

Third, the procurement costs and procurement difficulties
Spiral steel pipe production of large-scale steel pipe plant of petroleum and petrochemical systems, the advantages are mainly concentrated in the manufacture of large-diameter steel pipe, the manufacturing cost is relatively low. However, for small and medium caliber (Φ114mm ~ Φ355.6mm) steel pipe, the manufacturing cost is higher, averaging 8% ~ 15% higher than ERW pipe.

Large-scale spiral pipe plant often do not produce small and medium-sized spiral pipe, procurement more difficult. Medium and small diameter erw pipe, due to the large number of manufacturers, is very easy to purchase.

Fourth, pipe geometry
1, ERW pipe geometry of the higher accuracy; and spiral welded pipe geometry accuracy is low, resulting in the construction of the site weld girth difficulties.
2, ERW pipe weld coefficient is 100%; spiral welded pipe weld coefficient of 130% -200%. The weld length of spiral pipe is much longer than that of erw pipe, and the incidence of defects also increases synchronously.
3, ERW pipe weld height remaining close to zero, the naked eye is not visible; spiral steel pipe on the outside surface must leave about 0.3 mm height (which is determined by the production process). The weld seam is so high that there is a gap between the steel pipe coating (3PE) and the pipe body, which makes the corrosion resistance of the steel pipe greatly reduced.
4, Due to the spiral welded pipe remaining high, the transmission of high-speed fluid there will be a greater disturbance, increase the flow resistance and reduce pipeline delivery efficiency. ERW pipe wall smooth, then there is no such problem.

Five, other differences

ERW pipe compression performance is higher than the spiral pipe.