Causes of formation of single double-sided undercut of submerged arc welded steel pipe

Welding wire joint

Due to changes in the diameter and smoothness of the wire joint, the wire feed speed will suddenly change when the wire joint passes through the wire feed wheel, thereby causing an instantaneous change in the welding voltage and melting speed, a sudden widening of the weld pool and molten metal Insufficient supplementation can result in a single double undercut at this solder joint.

Welding specification

Under normal circumstances, there will be no major changes in welding specifications during continuous production. Therefore, undercuts will not occur during normal production. However, under the influence of the external power supply, the welding current and voltage may also be abrupt, and the result of the abrupt change will eventually lead to the occurrence of undercuts.

Instant short circuit

Sometimes due to the burr on the edge of the board or the metal burr mixed in the flux, an instant short circuit will occur at the contact tip during the normal welding process. The instantaneous short circuit will cause the welding current and voltage to change instantaneously, which will eventually lead to undercut. The treatment of a single double undercut is the same as the treatment method of a single single undercut, which can be processed by grinding or repairing.