What are the common defects of line pipe welding

1. Air bubbles. Air bubbles mostly occur in the center of the weld bead. Hydrogen is still hidden in the weld metal in the form of bubbles. The main reason is that the welding wire and flux have moisture on the surface, so they can be used directly without drying, and welding In the process, the current is small, the welding speed is too fast, and the accelerated solidification of the metal will also happen.

2. Undercut is a V-shaped groove at the edge of the weld along the center line of the weld. The main reason is that the welding speed, current, voltage and other conditions are not appropriate. The welding speed is too high. It is more likely to cause undercut defects than unsuitable current.

3. Hot cracks. The cause of hot cracks is when the stress of the weld is very high, or when the SI silicon element in the weld metal is very high, there is also a sulfur crack, and the billet has a strong sulfur segregation zone. Plate (belonging to soft boiling steel), during the welding process, sulfide enters the weld metal and produces cracks.

4. Insufficient penetration, insufficient overlap of the inner and outer weld metal, sometimes incomplete penetration. Welded pipe calculation method: (outer diameter-wall thickness) * wall thickness * 0.02466 = weight per meter of welded pipe {kg galvanized pipe calculation: (outer diameter-wall thickness) * wall thickness * 0.02466 * 1.06 = weight of welded pipe per meter { kg