1. Reasons for the formation of submerged arc welded steel pipes
① Welding wire joint: Due to the change in the diameter and smoothness of the welding wire joint, the wire feeding speed will change suddenly when the welding wire joint passes through the wire feeding wheel, which will cause the instantaneous change of welding voltage and melting speed, and the sudden change of welding pool The widening and insufficient replenishment of molten metal can result in a single double-sided undercut at this weld.
②Welding specification: Under normal circumstances, the welding specification will not change greatly during the continuous production process, so there will be no undercut in the normal production process. However, under the influence of the external power supply, the welding current and voltage may also undergo sudden changes, and the results of the sudden changes will eventually lead to undercutting.
③Momentary short circuit: Sometimes due to the burr on the edge of the board or the metal burr mixed in the flux, an instantaneous short circuit will occur at the contact tip during the normal welding process. The instantaneous short circuit will cause instantaneous changes in welding current and voltage, and eventually lead to undercutting. The treatment of a single double undercut is the same as that of a single undercut and can be processed by grinding or repairing.
2. Preventive measures for submerged arc welded steel pipes
①Properly handle the welding wire joints: For welding wire manufacturers, heat treatment should be performed on the joints to make their hardness consistent with the hardness of the entire welding wire. When welding wires are butt welded in the continuous production process of submerged arc welded steel pipes, the joints should be ground after the butt joints are completed to achieve a smooth transition and uniform true diameter, and the front and rear welding wires at the joints should be roasted with an oxyacetylene gun and allowed to cool naturally, to achieve the purpose of consistent hardness.
②Strictly control the welding specifications: pay attention to the changes in current and voltage during the welding process. If the changes are too large, find out the cause of the power supply and the power supply outside the system, so that the changes in the specifications are controlled within the allowable range.
Post time: Jun-14-2023