Advantages and features of ERW pipes

Electric resistance welded steel pipes, referred to as ERW pipes, have many advantages such as high productivity, low cost, material saving, high dimensional accuracy, easy automation, beautiful appearance and excellent welding quality. In recent years, countries have been actively studying the use of ERW pipes to replace seamless pipes (SMLS) and spiral submerged arc welded pipes (SSAW).

Advantages of ERW pipes:
‌1. High production efficiency‌: The production process of ERW steel pipes is highly automated, which can quickly complete the welding and forming of steel pipes, greatly improving production efficiency.
‌2. Low cost‌: Since the production process of ERW steel pipes is relatively simple and highly automated, the cost is low and suitable for large-scale production.
‌3. Material saving‌: In the production process of ERW steel pipes, the material utilization rate is high, which can effectively save raw materials.
‌4. Easy to automate‌: The production line of ERW steel pipes is easy to automate, which can reduce manual intervention and improve the consistency and stability of production.
‌5. Excellent welding quality‌: The welding of ERW steel pipes is carried out after the forming is completed, with excellent welding quality, short welds, and low probability of defects, ensuring the intrinsic quality and geometric dimensional accuracy of the pipe body.

6. Good surface quality: The surface of ERW steel pipe is smooth, flat and beautiful in appearance.

Comparison of the characteristics of ERW pipe and SMLS pipe:

1. The outer surface defects of the blank used for seamless pipe cannot be eliminated by hot rolling process. It can only be polished after the finished product is made. The spiral track left after perforation can only be partially eliminated when the wall is reduced. ERW steel pipe is made of hot-rolled coils. The surface quality of the coils is the same as that of ERW steel pipes. The surface quality of hot-rolled coils is easy to control and the target quality is high. Therefore, the surface quality of ERW steel pipes is better than that of seamless steel pipes.

2. Seamless steel pipes are formed by hot rolling. The raw material composition, cooling conditions and cooling state of the steel pipe have a great influence on its outer diameter, so the outer diameter is difficult to control accurately and has a large fluctuation range. ERW steel pipes are formed by cold bending, so the outer diameter is accurately controlled and the fluctuation range is small.

3. The tensile performance indicators of seamless steel pipes and ERW pipes meet the 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 plasticity index is 33.3% higher than the standard.

4. The raw material of ERW pipe, hot-rolled coil, has extremely high precision during the rolling process, which can ensure the uniformity of the performance of each part of the coil.

5. Due to the characteristics of its raw materials and pipe making process, the strength and plasticity of ERW steel pipe are better than other steel pipes. Its wall thickness uniformity and ovality are far better than seamless steel pipes, which is the main reason why its anti-collapse performance is higher than that of seamless steel pipes.
 

Comparison of the characteristics of ERW pipe and SSAW pipe:

Due to the differences in forming, welding, and processes between ERW steel pipe and SSAW pipe during 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, while SSAW pipe has internal and external weld excess height.
2. The weld of ERW steel pipe is shorter than that of SSAW pipe. The weld of ERW steel pipe is the same length as the length of steel pipe, while the weld length of SSAW pipe is generally 1.4-1.7 times the length of steel pipe. The longer the weld, the higher the probability of weld defects.
3. In the standard, the geometric dimensions of ERW steel pipe and spiral SSAW pipe are basically the same, but from the actual point of view, ERW steel pipe has sizing and straightening processes, so the geometric dimensions are more accurate than SSAW pipe.
4. There are fewer types of weld defects in ERW steel pipe than in SSAW pipe. SSAW pipe adopts surfacing, and there are many types of defects. In addition to volume defects, there are also linear depressions. The weld of ERW steel pipe has only linear defects, and the weld is straight, which is easy to track during the inspection process. Visually, the defect is at the maximum reflection point. Once a defect occurs, the ultrasonic reflection is strong and easy to find.
5. The residual stress of ERW steel pipe is lower than that of SSAW pipe. Due to the full deformation of ERW steel pipe during the deformation process, coupled with the changes of flat ellipse, vertical ellipse, and diameter reduction during the subsequent sizing, the residual stress of ERW steel pipe becomes smaller. Actual tests show 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 those of SSAW pipe.
6. The overall performance of ERW steel pipe is consistent. SSAW pipe allows 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.

7. The quality of the anti-corrosion layer of ERW steel pipe is higher than that of spiral submerged arc welded pipe.

Read more: SAW vs ERW and EFW Welded Steel Pipe or Matters needing attention when purchasing welded steel pipes

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