In pipeline welding, it is necessary to handle the joints carefully. If the joint is not handled properly, there may be welding defects such as slag inclusion and poor fusion, which may lead to leakage during pressure test after the weld is completed.

After replacing covered electrode, there are generally two joint methods:

1, thermal connection method:

After the arc is turned off, quickly put on a new covered electrode. When the arc is still in a red-hot state at the arc-closing position, immediately start the arc from the front of the molten pool, and quickly pull the arc to the arc-closing position for welding, and the arc will be pressed down at the welding hole. When you hear the "poop-poop" sound when the arc melts the blunt edge of the groove, move it away immediately and use the normal welding method for welding.

The key is to quickly replace the covered electrode, and the welding process should be clever and flexible, which is a common welding method in welding production.

2, cold connection method:

Before starting the arc, clean the slag at the joint, polish it into a gentle slope when the arc is too high or burr, then start the arc at a distance of 10mm from the original arc pit, preheat it with a long arc, then swing the arc forward to the arc pit and press down the arc. When the arc breaks through the root of the groove and makes a "poop-poop" sound, it can be transferred to normal welding.

The advantage of cold welding method is that when the arc closing of the previous weld is not good (when there are shrinkage holes or the welding meat is too thick), it can be polished to eliminate defects, make the joint thinner and easily ensure the welding quality; At the same time, the difficulty is less than that of thermal connection; The disadvantage is that the efficiency is not as high as that of hot welding, especially when the joint is not allowed to be repaired and polished, such as in skill competitions, this method is not suitable.