Bubbles
Bubbles often occur in the center of the weld bead, where hydrogen remains trapped within the weld metal in the form of bubbles. The primary reasons for this include moisture on the surface of the welding wire and flux, which are used without prior drying. Additionally, using a low welding current or an excessively fast welding speed can accelerate metal solidification, leading to the formation of bubbles.
Undercut
Undercut refers to the V-shaped groove that appears along the edge of the weld bead centered on the weld line. This defect primarily arises due to inappropriate welding conditions such as welding speed, current, and voltage. Among these, an excessively high welding speed is more likely to cause undercut than an unsuitable current.
Hot Cracking
Hot cracking occurs when the weld stress is high or when the silicon (Si) content in the weld metal is excessively high. Another type of hot cracking is sulfur cracking, which happens when the billet is made from a plate with strong sulfur segregation (belonging to soft rimmed steel). During welding, sulfides enter the weld metal, leading to the formation of cracks.
Insufficient Penetration
Insufficient penetration refers to inadequate overlapping of the inner and outer weld metal, sometimes resulting in incomplete fusion.
Calculation Methods for Welded Pipes:
Welded Pipe Weight Calculation (per meter, in kilograms):
(Outer Diameter - Wall Thickness) * Wall Thickness * 0.02466 = Weight of Welded Pipe per Meter (kg)
Galvanized Pipe Weight Calculation (per meter, in kilograms):
(Outer Diameter - Wall Thickness) * Wall Thickness * 0.02466 * 1.06 = Weight of Galvanized Pipe per Meter (kg)
Note: The factor 1.06 in the galvanized pipe calculation accounts for the additional weight of the zinc coating.
