1. Involvement of welding slag: Welding slag is a part of the welding slag remaining in the weld metal.

2. Poor penetration

The metal overlap of the inner and outer welds is not enough, and sometimes there is no penetration. This situation is called insufficient penetration.

3. Undercut

The undercut is a V-shaped groove on the edge of the weld along the center line of the weld. The undercut is produced when the welding speed, current, voltage, and other conditions are not appropriate. Among them, the welding speed is too high to be more suitable than the current It is more likely to cause undercut defects of spiral welded steel pipe.

4. Bubbles

Most of the bubbles occur in the center of the weld bead. The main reason is that hydrogen is still hidden in the welded metal in the form of bubbles. The measure to eliminate this defect is to first remove the rust, oil, moisture, and moisture of the welding wire and weld, secondly, the flux must be dried well to remove moisture.

5. Sulfur cracking

Sulfur cracking is a crack caused by sulfur. When welding a plate with a strong sulfur segregation zone, the sulfide in the sulfur segregation zone enters the weld metal. The reason is that the sulfur segregation zone contains iron sulfide and steel with a low melting point. hydrogen gas is present.

6. Hot crack

In the submerged arc welding of spiral welded steel pipe, thermal cracks can be generated in the weld bead. In order to eliminate such cracks, backing plates are usually installed at the arc starting and extinguishing places, and when the coil butt welding is completed, the spiral welded steel pipe can be reversed and the weld into the stitch weld.