The analysis of several types of butt connection quality can be used as a reference for the situation of the curled edges at the connection points of pipes.
Visual inspection: The welded edge is round and of good quality
The narrow and high welding edge is caused by excessive welding pressure
The welding edge is too low, which is caused by too little welding pressure.
There is a deep groove in the middle of the welding, and the depth of the groove is equal to the welding end face. This is caused by the welding temperature being too low and the switching time being too long.
The different melting temperatures or heating times of the two tubes result in one high and one low edge seam at the ends of the two tubes.
The connection at the ends of the two pipes is severely misaligned, with the maximum misalignment not exceeding 10% of the pipe wall thickness.
The comprehensive judgment criteria for edge rolling combined with other indicators
1.Requirements for rolled edge shape：
Qualified: The rolled edge is uniform and full, free of cracks, bubbles, and charred black, and continuous along the circumference without any breaks.
Unqualified: The rolled edge is too thin (< 2mm), too thick (> 1.5 times the wall thickness of the pipe), locally missing, broken or carbonized.
2.Core testing indicators to be matched:
Roll edge removal test: Use a special tool to remove the roll edge and observe whether the internal welding surface is flat, free of gaps and impurities.
Tensile/burst test: Conduct mechanical tests on the welded joint, and the strength should reach more than 90% of the strength of the base material.
Pressure test: After welding, a water pressure/air pressure test is conducted. If there is no leakage or deformation, it is considered qualified.