Spiral welded pipe restrictions in welding zone

Common restrictions of spiral welded pipe in welding zone are found with porosity, hot cracks, and undercuts.
1. Bubbles. Bubbles occur mostly in the center of the weld bead of welded steel pipe. The main reason is that hydrogen is still hidden in the weld metal in the form of bubbles. Therefore, the measure to eliminate this defect is to first remove the rust, oil and moisture of the wire and weld. And substances such as moisture, and secondly, the flux must be dried 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 the molten metal. In addition to the defects, it is necessary to first remove the rust, oil, moisture and moisture of the welding wire and the weld, and secondly, it is necessary. The flux is well dried to remove moisture. In addition, it is also effective to increase the current, reduce the welding speed, and slow down the solidification speed of the molten metal.

2. Sulfur cracking (crack caused by sulfur). A crack generated by the sulfide in the sulfur segregation zone entering the weld metal when the sulfur is segregated with a strong plate (especially soft boiling steel). The reason for this is that hydrogen sulfide is present in the sulfur segregation zone containing iron sulfide having a low melting point and steel. Therefore, in order to prevent this from happening, it is also effective to use semi-killed steel or killed steel with less sulfur segregation belt. Secondly, it is also necessary to clean and dry the surface of the steel pipe and the flux.

3. Hot cracks. In submerged arc welding, hot cracks can be generated in the weld bead, especially in the arcing and arc extinguishing craters. In order to eliminate such cracks, a shim plate is usually provided at the arcing and extinction arc, and at the end of the coil-to-welding end, the spiral welded pipe can be reversed to be welded into the lamination. Hot cracks are easy to occur when the weld stress is high, or when the si in the weld metal is high.

4. The welding slag is involved. Involving the welding slag is to leave a part of the welding slag in the weld metal.

5. Poor penetration. Internal and external weld metal overlap is not enough, sometimes not welded. This situation is called insufficient penetration.