ERW (electric resistance welding) pipes have the following major disadvantages while being widely used, which directly affect their performance and safety of use:
High risk of weld defects
- Common defects such as lack of fusion and cold welding, which appear as black/grey oxides in the macroscopic view and dimples or mesh-like oxides in the microscopic view.
- Defects can lead to abnormal distribution of metal flow lines, reduce strength, and are prone to crack propagation, especially under high pressure environments.
- Insufficient welding heat input or poor edge shape of the strip are the main causes, and the residual iron oxide formed at high temperature directly affects the fusion quality.
Limited corrosion resistance
- The weld area is susceptible to corrosion and requires additional anti-corrosion treatment. It is more prone to local corrosion failure than seamless pipes.
- Corrosion products (such as manganese oxide and silicon dioxide) accumulate in the cold welding area, which accelerates material degradation.
Limited use conditions
- Not suitable for high pressure (>10MPa), high temperature (>300℃) or cyclic load conditions. There have been incidents of cracking of girth welds in oil and gas transportation, and failures are often related to improper welding processes, misalignment and other factors.
- Strict quality control requirements
- High-frequency welding processes are required to accurately control temperature (error ±50°C), extrusion volume (wall thickness 5% ±0.5mm) and opening angle.
- Impurities or burrs on the edge of the plate can cause high-frequency short circuits and cold welding defects, which require water pressure/ultrasonic testing.
