Electric resistance welded steel pipes, referred to as ERW pipes , have many advantages such as high productivity, low cost, high dimensional accuracy and beautiful appearance. In recent years, countries are actively researching the use of ERW pipes instead of seamless pipes and SSAW pipes 1. The outer surface defects of the blank used in the seamless pipe cannot be eliminated by the hot rolling process, and can only be polished after the finished product is made. The helical path remaining after perforation can only be partially eliminated during wall reduction. ERW steel pipes are made of hot-rolled coils. The surface quality of the coil is that of the ERW steel pipe. The surface quality of hot-rolled coils is easy to control and the target quality is high. Therefore, the surface quality of ERW steel pipe is better than that of seamless steel pipe2. The seamless steel adopts hot rolling forming process. The raw material composition of the steel pipe, the cooling conditions and the cooling state of the roll have a great influence on its outer diameter, so it is difficult to accurately control the outer diameter and the fluctuation range is large. ERW steel pipe is formed by cold bending, so the outer diameter is controlled accurately and the fluctuation range is small.3. The tensile performance indicators of seamless steel pipes and ERW pipes meet API standards, but the strength of seamless steel pipes is generally at the upper limit and the plasticity is at the lower limit. In contrast, the strength index of ERW pipe is in the best state, and the index of plastic parts is 33.3% higher than the standard.4. The raw material of ERW pipe, hot-rolled coil, has extremely high precision in the rolling process, which can ensure the uniform performance of each part of the coil.5. ERW steel pipe is due to the characteristics of its raw material and pipe making process. Its wall thickness uniformity and ellipticity are far superior to seamless steel pipes, which is the main reason why its anti-collapse performance is higher than that of seamless steel pipes.Due to the different forming, welding and process of ERW steel pipe and SSAW pipe in the pipe making process, there are certain differences in the performance of the two steel pipes.1. The surface quality of ERW steel pipe is better than that of SSAW pipe. The surface of ERW steel pipe is smooth, flat and beautiful. SSAW pipe has internal and external weld reinforcement.2. The welding seam of ERW steel pipe is shorter than that of SSAW pipe. The seam of ERW steel pipe is as long as the length of steel pipe, while the length of weld seam of SSAW pipe is generally 1.4-1.7 times the length of steel pipe. The longer the weld, the higher the chance of weld defects.3. In the standard, the geometric dimensions of ERW steel pipes and spiral SSAW pipes are basically the same, but in terms of physical objects, ERW steel pipes have sizing and straightening processes, so the geometric dimensions are more accurate than SSAW pipes.4. There are fewer types of weld defects in ERW steel pipes than in SSAW pipes. SSAW pipe adopts deposition welding, and there are many types of defects. In addition to volume defects, there are also line sinks. The weld seam of ERW steel pipe has only line defects, and the weld seam is straight, which is easy to track during the inspection process, and the eye defect is at the maximum reflection point. Once a defect occurs, the ultrasonic reflection is strong and easy to detect.5. The residual stress of ERW steel pipe is lower than that of SSAW pipe. Due to the sufficient deformation of the ERW steel pipe during the deformation process, coupled with the subsequent changes in the sizing flat ellipse, vertical ellipse and diameter reduction, the residual stress of the ERW steel pipe becomes smaller. The actual test shows that after the ERW steel pipe of the same specification and material is cut along the axis, the axial and transverse incision displacements are smaller than that of the SSAW pipe.6. The overall performance of ERW steel pipe is consistent. SSAW pipes allow repair welding, but the performance of the repair welding is not consistent with the overall performance of the steel pipe, and stress corrosion cracking is prone to occur at the repair welding place.7. The coating quality of ERW steel pipe is higher than that of spiral submerged arc welded pipe.

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