Common defects in welding area of spiral welded pipe

The common defects of spiral pipes include pores, slag inclusions, incomplete penetration, incomplete fusion and cracks, etc. The carbon steel pipe manufacturers will introduce the causes of these defects below.

The defects that are prone to occur in the submerged arc welding zone of the spiral welded pipe are:

1. Involvement of welding slag
Weld slag is a part of 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 along the centerline of the weld, and the undercut is produced under improper conditions such as welding speed, current, and voltage. Among them, if the welding speed is too high, it is more likely to cause undercut defects than if the current is not suitable.
   
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 weld 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 tubes, 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 points, and at the end of the coil butt welding, the spiral steel tube can be reversed and the Welding into stitch welding. Hot cracks are most likely to occur when the weld stress is high, or when the temperature in the weld metal is high.

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