Under the action of welding arc heat, the moisture absorbed by the welding flange electrode becomes gas, decomposing hydrogen, resulting in the formation of welding cracks and pores. Alkaline electrodes are especially bad. When the welding flange welding rod is packed with polyethylene plastic bags, it can not guarantee long-term thorough moisture-proof.
The mechanical properties are low.
Simple way to check moisture condition of butt welding flange on site:
(1) Check the packaging of the welding flange electrode, the packaging is damaged, and the welding electrode must be serious.
(2) Check the manufacturing date of the electrode, and the surface of the electrode stored for a long time after manufacturing is prone to white mildew marks.
(3) Roll a few welding rods in your hand, and the electrode loses its crisp metal sound after absorbing moisture.
(4) Take a electrode slightly bent 10-15 degrees, if the bending emit obvious brittle sound, it indicates that the electrode is relatively dry.
(5) Take a electrode vertically and land on the ground to observe its bounce force, the dry electrode has better bounce force and higher rebound.
(6) The butt welding flange electrode is connected to the welding circuit for a few seconds. If there is water vapor on the surface of the coating, it is a non-dry electrode.
(7) Take a electrode directly for test welding. If the electrode is damp, the coating will burst or fall off in the welding process, and produce more water vapor.
(8) Observe the surface of the end of the weld core to see if there is rust.
(9) Take a beam of electrode and check with the naked eye: if there are black spots on the surface of the coating, it indicates that the welding core inside the electrode has been corroded. You can also knock off the coating and directly check whether the welding core is corroded.
(10) In the butt welding flange welding operation during the inspection, the process performance of the damp electrode will appear the following changes:
At the same current value, the arc blowing force increases and the melting depth increases.
The number of spatter increases and the particles become larger;
For acid electrode, the slag cover is poor, and the weld deformation is poor;
For low-hydrogen electrode, many small holes appear on the inner side of the slag (the side in contact with the weld).
From: Chongqing Giant Pipe Fittings Co., LTD
