Defects on the welding surface of ERW steel pipes

In the production of electric resistance welded (ERW) steel pipes, the internal weld surface is typically treated using one of two methods: incomplete scraping (retaining some weld reinforcement) or complete scraping (which forms a groove on the inner surface). The effectiveness of these methods can significantly impact the overall performance of the steel pipe.

Methods of Internal Weld Surface Treatment:

Incomplete Scraping:

Description: This method leaves a certain amount of burrs on the inner surface of the weld, with specifications often allowing burr heights up to 0.8 mm. While incomplete scraping avoids damage to the base material and does not significantly weaken the weld’s structural integrity, it can lead to reflections during ultrasonic testing. Residual burrs can cause interference in ultrasonic flaw detection, resulting in a higher rate of false alarms.

Complete Scraping:

Description: This method involves thoroughly removing all internal burrs, creating a smooth transition between the base material and the weld. This approach helps eliminate burr-related interference in ultrasonic flaw detection, leading to more accurate testing results. However, complete scraping can pose challenges, such as stability issues during the scraping process. Problems like vibration or system failures can cause local scratches, which may damage the base metal and deform the welded area, potentially compromising the structural strength.

Challenges and Considerations:

Burr Formation:

After welding, excess metal in the welding area results in burrs on both the inner and outer surfaces of the ERW pipe. Typically, scrapers are used to remove these burrs. While outer burrs are often effectively managed, inner burrs are more challenging and may leave high or uneven surfaces if not properly addressed.

Strength and Reliability:

The thickness of ERW pipe welds and the effectiveness of ultrasonic testing are influenced by the chosen scraping method. Incomplete scraping may result in higher false alarms during testing, while complete scraping requires careful handling to avoid damage that could affect the pipe’s strength and reliability.

Summary:

The internal weld surface treatment of ERW steel pipes involves balancing the need for thorough burr removal with the risk of causing damage during the scraping process. Incomplete scraping may lead to inaccuracies in ultrasonic testing, while complete scraping can affect the pipe's structural integrity if not performed correctly. Choosing the appropriate method depends on achieving optimal performance and reliability for the steel pipes in their intended applications.