pipeline welding defect analysis
When arc blowout, the protective effect of the arc and slag is weakening, and it is easy to be prone to porosity and other defects in the crater. The defects can be removed when the next track weld joints. And eliminating the effects depend on the joint when the melting possible. The power station boiler heating surface is mostly calandria disorder, the disorder in the form of a joint decision more on the road when the joints of the crater of the weld short duration of action, it is difficult to overcome the defects, could easily lead to discharge pipe welded joints appear groups hole.
When manual arc welding, tilt angle of electrode has great protective influence to welding line. If not keep right angle always in the welding process, this will lead to invading into harmful gases from outside. With the increasing of incorrect angle welding length, it will form strip holes. The level of large diameter pipe fixed the position welding, due to the height restrictions, the welder must be in different welding position to take a different posture to keep stretch angle. Therefore, it is easy to appear the strip holes for the welding joint. While for small diameter tube, the defect is mainly without ideal welding frame build-up. The speed and swing amplitude of electrode manipulation determine the thickness of single bead. Rapid speed of electrode manipulation makes electrode angle to change quickly, otherwise it cannot form effective joint of slag gas protection.
Fins pipe welding joints is often tending to rows counterpart, with welding shrinkage deformation, leading to much more difficult to keep proper clearance counterparts. When the argon arc welding backing on groove melting degree reduces, resulting in lack of penetration easily. Large diameter pipe with wall thick wall, when the argon arc welding joint incomplete fusion, will cause lack of penetration. In addition, bigger blunt for large diameter pipe is easy to cause lack of penetration.
When welding, the thickness of filler metal will affect the buoyancy of the molten slag and overflow. If the slag cannot overflow, it will result in the formation of slag defects. Large diameter thick wall pipe often adopts the big electric current when welding, single welding thickness is larger, slag completely rise is more difficult, to form slag defects.