Common defects in the submerged arc welded zone of spiral submerged arc welded steel pipes include porosity, hot cracking, and undercut.
1. Air bubbles in spiral submerged arc welded steel pipes. Air bubbles often occur in the center of the weld bead. The main reason is that hydrogen gas remains hidden inside 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 of the spiral submerged arc welded steel pipe, and secondly, to thoroughly remove moisture from the spiral submerged arc welded steel pipe using a drying flux. In addition, increasing the current, reducing the welding speed, and slowing down the solidification rate of the molten metal are also very effective.
2. Sulfur cracks (cracks caused by sulfur) in spiral submerged arc welded steel pipes. These cracks occur when welding plates with strong sulfur segregation bands (especially soft boiling steel), causing sulfides in the sulfur segregation bands to enter the weld metal. The reason is that spiral submerged arc welded steel pipes contain low-melting-point iron sulfide in the sulfur segregation zone and hydrogen in the steel. Therefore, to prevent this, using semi-killed or killed steel with less sulfur segregation is also effective. Secondly, the cleaning and drying of the weld surface and flux of spiral submerged arc welded steel pipes are also essential.
3. Hot cracking in spiral submerged arc welded steel pipes. In submerged arc welding, hot cracks can occur in the weld bead of spiral submerged arc welded steel pipes, especially at the arc initiation and extinguishing craters. To eliminate these cracks, backing plates are usually installed at the arc initiation and extinguishing points, and at the end of the plate-coil welding, the spiral submerged arc welded steel pipe can be reversed to weld into the lap weld. Hot cracking is prone to occur when the weld stress is high or when the weld metal has a high internal temperature.
4. Slag entrapment in spiral submerged arc welded steel pipes. Slag entrapment refers to the presence of residual slag in the weld metal.
5. Poor weld penetration in spiral submerged arc welded steel pipes. The overlap between the inner and outer weld metals of the spiral submerged arc welded steel pipe is insufficient, sometimes resulting in incomplete penetration. This condition is called insufficient weld penetration.
6. Undercut in spiral submerged arc welded steel pipes. Undercut in spiral submerged arc welded steel pipes is a V-shaped groove appearing along the weld centerline at the edge of the weld. Undercut in spiral submerged arc welded steel pipes occurs when welding speed, current, voltage, and other conditions are inappropriate. A welding speed that is too high is more likely to cause undercut defects than an unsuitable current.
Post time: Apr-02-2026