Spiral pipes and Carbon ERW steel pipes are currently widely used in our country. Spiral pipes (SSAW steel pipe) and longitudinal electric resistance welded pipes (ERW) are widely used for oil and natural gas transportation. There is a difference between these two types of pipes, which are generally the difference between the production process and the difference between the raw materials. These two differences make the spiral pipe and the longitudinal resistance welded pipe have a big difference in the scope of use. Next, the spiral pipe manufacturer will talk to you about the specific difference between spiral pipe and ERW pipe.
1. The difference in production process
The ERW longitudinal resistance welded pipe is a hot-rolled coil formed by successive rolls, using the skin effect and proximity effect of high-frequency current to melt the edge of the coil, and pressure welding is performed under the effect of the squeeze roller force. produce. Therefore, the residual stress of ERW straight seam electric resistance welded steel pipe is relatively small. After welding seam heat treatment, sizing, straightening, and hydraulic pressure, the residual stress is further released and reduced. Practice has proved that the residual stress of ERW straight seam resistance welded pipe does not affect the steel pipe during storage and use. Without any welding wire, the physical properties and chemical composition of the weld are completely consistent with the plate. The quality of ERW pipe depends on the quality of the sheet.
The steel plates for spiral pipes are welded together with welding wire through the spiral rotation of the unit. After the steel plates are spirally rotated, the geometric stress is more messy, and some even reach the yield limit of the steel plate. The spiral pipe will have a larger residual stress in the future, and its residual stress Is tensile stress. After the steel pipe is subjected to internal pressure, the pipe wall also has a circumferential tensile stress, and the two superimposed, which weakens the steel pipe's bearing capacity. It is even more insecure during use. The steel plates are welded together by welding wires containing chemical components, and bubbles and hot cracks in the weld bead are prone to occur during the welding process. Make the weld and the base metal have obvious differences in physical properties and chemical composition. It is very easy to cause great concentrated stress at the joint of the weld and the base metal. During the welding process, the heat influence is great and the hardness is high.
2. Material difference
The raw materials used in ERW steel pipes are all hot-rolled coils produced by regular large factories, and their chemical composition and physical properties are relatively stable.
3. Acquisition cost and difficulty of acquisition
The advantages of spiral pipes produced by large steel pipe plants in the petroleum and petrochemical system are mainly concentrated in the production of large-diameter steel pipes, and the manufacturing cost is relatively low. However, for steel pipes with small and medium diameters (￠114mm~￠355.6mm), the forming cost is higher, which is even 8%~15% higher than ERW steel pipe.
Large-scale spiral pipe factories often do not produce small and medium-caliber spiral pipes, which makes it difficult to purchase. The small and medium diameter ERW steel pipes are very easy to purchase because of the large number of manufacturers.
The above is the difference between spiral pipe and ERW pipe. These two kinds of steel pipes have made great contributions to my country's oil and natural gas transportation. Not only in China, but also abroad, these two types of pipes are also widely used.
