Analysis of cracks and pores in butt welding flange welding

The moisture absorbed by the welding rod of the butt welding flange turns into gas under the action of the welding arc heat, decomposing hydrogen, resulting in the formation of welding cracks and pores. This is especially true for alkaline electrodes. Butt welding flange welding rod is sealed with polyethylene plastic bag, which cannot guarantee long-term and complete moisture-proof.

　　The various indexes of mechanical properties are low.

　　A simple way to check the moisture of the welding rod of the butt welding flange on site:

　　 (1) Check the packaging of the welding rod for the butt welding flange. The packaging is damaged and the welding rod must absorb moisture seriously.

　　 (2) Check the manufacturing date of the welding rod. The surface of the welding rod stored for a long time after manufacturing is prone to white mold-like spots.

　　(3) Put a few welding rods in your hands and roll them, and the welding rods lost the crisp metallic sound after absorbing moisture.

　　(4) Take a welding rod and bend slightly by 10-15 degrees. If there is a clear cracking sound when bending, it means that the welding rod is relatively dry.

　　(5) Take a welding rod to the ground and observe its bounce force. The dry rod has better bounce and higher rebound.

　　(6) Connect the welding rod of the butt welding flange to the welding circuit and short-circuit for a few seconds. If water vapor appears on the surface of the coating, it is a non-drying electrode.

(7) Take a welding rod for trial welding directly. If it is a damp welding rod, the coating will burst or fall off in blocks during the welding process, and produce more water vapor.

　　(8) Observe the surface of the core end to see if there is rust.

　　 (9) Take a bunch of welding rods and check with the naked eye: if there are black spots on the surface of the coating, it indicates that the core of the welding rod has been rusted. You can also knock off the coating and directly check whether the welding core is corroded. 

　　(10) Check during the welding operation of the butt welding flange, the process performance of the damp electrode will have the following changes:

　　At the same current value, the arc blowing force becomes larger and the penetration depth increases;

　　The number of splashes increases and the particles become larger;

　　 For acid electrodes, the slag coverage is poor, and the weld shape becomes poor;

　　  For low-hydrogen type electrodes, there are many small holes on the inner surface of the slag (the side in contact with the weld).