Therefore, in summary, high-frequency welded pipe is included in ERW welded pipe, which is a kind of ERW welded pipe produced by high-frequency welding process. ERW straight seam welded pipe is a steel pipe with advanced product performance, leading quality and relatively economical performance in the field of oil and gas storage and transportation.
Submerged arc weld of high quality,high production efficiency, arc and smoke a few characteristics of submerged arc welded pipe is widely used in pressure vessels, pipe manufacturing, beams, low pressure fluid, steel works.
ERW Steel Pipe VS SAW Steel Pipe
Carbon steel welded pipes can be divided into three types: straight seam submerged arc welded steel pipes, spiral welded steel pipes, and high-frequency straight seam welded steel pipes (Electric Resistance Welded Steel Pipe) according to the forming method of the weld seam. In manufacturing processes, we can see ERW steel pipes and SAW steel pipes (LSAW, SSAW) have completely different forming and welding methods.
1) ERW steel pipe manufacturing method
When ERW steel pipe welding process, two electrodes, usually made from copper, are used to apply pressure and current. The electrodes are disc shaped and rotate as the material passes between them. This allows the electrodes to stay in constant contact with the material to make long continuous welds.
As ERW steel pipe and SAW steel steel pipe in the pipe during forming, welding and process is different, so that two kinds of steel pipe in the performance there are some differences:
1. The surface quality.
Though both SAW pipes and ERW steel pipes all have weld seam.The welding seam of ERW pipe is flat, smooth and better than SAW (LSAW, SSAW) pipes. In most of the SAW pipes, it is mainly about the weld reinforcement internally and externally.
2. ERW steel pipe weld defect types is less than the SAW steel pipe.
Because of the solvent deposited in SAW, in addition to volume defects it results in more defects.The defects found in ERW welded steel pipes are only straight welds and wire-line and are easy to inspect. The defects can be noticed easily and the ultrasonic reflection on the surface makes it easier to detect.
3. The residual stress ratio in ERW is lower than SAW steel pipes.
ERW steel pipe related to SAW steel pipe in residual stress ratio is low. Since ERW welded pipe deformation in the deformation process more fully, coupled subsequent sizing flat oval,elliptical vertical changes and necking, making ERW steel pipe residual stress becomes smaller. Physical testing showed that the same specifications, the same material ERW welded pipe after incision along the axis, the axial and transverse incisions smaller displacement than the SAW welded pipe.
4. The overall performance.
Although the overall performance of both ERW steel pipe and SAW steel pipe are the same, when the pipe becomes defective,the steel scrap and welding can be done on ERW welded pipe, while it is not the same in case of SAW, which would result in cracking or corrosion. So ERW steel pipe are more durable than SAW steel pipe.
2) SAW welded steel pipe manufacturing process
In the single-seam SAW steel pipe, submerged arc welding process is used for welding. In this method, a welding arc is submerged in welding flux. A continuous solid filler wire is input from the outside. The pipe is double-welded, first is inside and then welding from the outside.
In the case of double seam SAW steel pipe, the first two halves are connected by tack welding, which is called fit-up. Double seam saw steel pipe has two opposite weld seam. Both seams are welded from inside and outside of the pipe.
In a spiral SAW steel pipe, steel plate from the de-coiler is formed in a spiral loop.This spiral loop is then welded from inside and outside of the pipe.Because of the method of manufacture, a wide variety of diameters can be produced. SSAW steel pipes are used for low-pressure services.
Whereas LSAW steel pipes are used for medium to high-pressure services. SSAW steel pipes are less costly compared to LSAW steel pipe.
