What are the common defects in welding area of SSAW spiral pipe

The common defects in the welding area of SSAW spiral pipe are porosity, hot crack, undercut, etc.

1. Bubbles. Bubbles often 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. Therefore, the measures to eliminate this defect are to first remove rust, oil, moisture and other substances from the welding wire and weld, and then to dry the flux well to remove moisture. In addition, it is also effective to increase the current, reduce the welding speed and slow down the solidification speed of molten metal.

2. Sulfur cracking (cracks caused by sulfur). When welding the plate with strong sulfur segregation zone (especially the soft boiling steel), the sulfide in the sulfur segregation zone enters into the weld metal and produces cracks. The reason is that there is hydrogen in iron sulfide and steel with low melting point in the sulfur segregation zone. Therefore, in order to prevent this, it is effective to use semi killed steel or killed steel with less sulfur segregation zone. Secondly, it is necessary to clean and dry the weld surface and flux.

3. Hot cracks. In the process of submerged arc welding, hot cracks can be produced in the weld bead, especially in the arc starting and arc extinguishing craters. In order to eliminate this kind of crack, a backing plate is usually installed at the arc starting and arc extinguishing points. At the end of the plate roll butt welding, the SSAW spiral pipe can be reversed and welded into the stack welding. Hot cracks are most likely to occur when the weld stress is large, or when the Si in the weld metal is high.

4. Involvement of welding slag. Involving welding slag is the residual part of welding slag in the weld metal.

5. Poor penetration. The overlap of internal and external weld metal is not enough, sometimes it is not fully welded. This is called insufficient penetration.

6. Undercut. The undercut of SSAW spiral pipe is a V-shaped groove along the weld center line. Undercut is produced when welding speed, current, voltage and other conditions are not appropriate. Among them, too high welding speed is more likely to cause undercut defects than unsuitable current.