Common defects in the welding area of SSAW steel pipes

In the production of SSAW (Spiral Submerged Arc Welded) steel pipes, welding is a critical process that directly impacts the quality and performance of the final product. However, various defects can occur in the welding area, affecting the integrity of the welds. Understanding these defects and how to address them is crucial for maintaining the quality of the steel pipes.

1. Bubbles

Bubbles primarily occur in the center of the weld bead and are typically caused by hydrogen trapped in the welded metal. The hydrogen forms gas bubbles during the welding process, leading to defects.
Solution: To prevent this, ensure that the welding wire and weld area are thoroughly cleaned to remove rust, oil, water, moisture, and other contaminants. Additionally, the flux should be properly dried to eliminate moisture. Increasing the current, reducing the welding speed, and slowing down the solidification rate of the molten metal can also help minimize bubble formation.

2. Sulfur Cracking (Cracks Caused by Sulfur)

Cracking due to sulfur occurs when welding plates that have a high concentration of sulfur in their segregation zones, especially in low-quality steel (such as soft boiling steel). The sulfur segregation zone contains low-melting-point iron sulfides, which, when combined with hydrogen in the steel, can cause cracks.
Solution: To prevent sulfur cracking, use semi-killed or killed steel with less sulfur segregation. It is also essential to clean and dry the weld surface and flux to reduce the chances of sulfur-related defects.

3. Thermal Cracks

Thermal cracks, or hot cracks, often occur in the weld bead, especially in the arc starting and arc extinguishing areas. These cracks are usually caused by high thermal stress or a high silicon content in the weld metal.
Solution: To reduce the risk of thermal cracking, install backing plates at the arc starting and arc extinguishing points. For coil butt welding, consider reversing and switching to stick welding at the end of the plate. Reducing stress in the weld area and controlling the silicon content in the weld metal can also help prevent these cracks.

4. Inclusion of Welding Slag (Bad Involvement)

The inclusion of welding slag occurs when part of the slag is trapped within the weld metal, creating defects that can weaken the weld.
Solution: To minimize slag inclusion, ensure proper slag removal between passes and use the correct welding techniques to avoid trapping slag in the molten pool.

5. Poor Welding Penetration

This defect occurs when the metal thickness of the internal and external welds is insufficient, sometimes resulting in a lack of full penetration.
Solution: To avoid poor penetration, adjust the welding parameters such as current, voltage, and speed. Proper heat control and ensuring the correct welding angle can also help achieve deeper penetration and stronger welds.

6. Undercut

Undercut refers to the V-shaped groove that appears along the edge of the weld, usually caused by improper welding conditions such as incorrect speed, current, or voltage.
Solution: Undercut is most commonly caused by high welding speeds, so reducing the welding speed and ensuring that the current and voltage settings are appropriate can help prevent this defect.