1. Bubbles
Bubbles mostly occur in the center of the weld bead, and hydrogen is still hidden inside the weld metal in the form of bubbles. The main reason is that the welding wire and flux have moisture on the surface and are used directly without drying. Also, the current is relatively high during the welding process. Small, the welding speed is too fast, and this will also happen if the solidification of the metal is accelerated.

2. Undercut
Undercut is a V-shaped groove appearing on 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 inappropriate. Among them, the welding speed is too high and the current is inappropriate. It is easy to cause undercut defects.

3. Thermal cracks
The cause of hot cracks is when the weld stress is very high, or when the SI silicon element in the weld metal is very high, there is another kind of sulfur cracking, the blank is a plate with a strong sulfur segregation zone (belongs to soft boiling Steel), cracks caused by sulfides entering the weld metal during the welding process.

4. Insufficient welding penetration
The metal overlap of the inner and outer welds is not enough, and sometimes the welding is not penetrated.
Calculation method for welded steel pipe: (outer diameter – wall thickness) * wall thickness * 0.02466 = weight per meter of welded steel pipe {kg
Galvanized steel pipe calculation: (outer diameter – wall thickness) * wall thickness * 0.02466 * 1.06 = weight of welded steel pipe per meter {kg