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Analysis of pipeline welding defect

At the time of the extinction, the protective effect of the arc and sla is weakening and easy to be prone porosity and other defects in the crater.

Groups hole
The extent of the defects can be removed when the next track weld joints, eliminating the effects of good or bad depends on the joint when melting, melting the extent possible, the more completely eliminate such defects. Power station boiler heating surfaces are 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 holes.
Strip holes
When manual electric arc welding affect the tilt angle of the protective effect of weld large, if not in the welding process always maintain the correct angle, will inevitably cause harmful gases outside intrusion, with no increase in the correct angle welding seam length, will forming a strip vent. When the level of the large diameter pipe is fixed for all position welding head for welding, due to the height so that the welder must take the welding positions are different at different positions in order to maintain operation of the angle bar. In the oblique oblique flat welding and overhead welding positions, welder in posture more difficult, it is difficult to maintain the correct angle bars shipped, so the weld these locations prone to strip holes. Small diameter pipe welding defect occurs mainly due to the shelf erection is not ideal. Speed and swings transport determines the thickness of the single bead, shipped fast speeds make the electrodes need to quickly change the angle, or can not form an effective slag = gas joint protection. After bottoming thin-walled tube welding requirements cover thin, hand welding should keep fast transport speeds, there would strip holes.
Incomplete penetration
Fin tube welded joints tend to think in a row counterpart, plus welding shrinkage deformation, resulting in more difficult to maintain proper clearance counterparts, when welding backing of melting degree bevel weakened, resulting in lack of penetration. Stainless steel welding consumables molten metal flow is poor, and the heat quickly, the heat is not easy to concentrate, which resulted in the arc heating and melting of the base metal or weld metal is more difficult to fill, the formation of incomplete penetration defects. Often large diameter thick wall pipe, joints when welding backing if not root penetration, is caused by lack of penetration; large diameter thick-walled tube blunt edge is large, are likely to cause incomplete penetration.
Slag
When soldering, the thickness of the filler metal will affect the slag floating overflow, slag defects can not be completely overrun if the slag is formed. Large diameter thick-walled pipe welding is often used when a large current, the larger the thickness of the single-pass welding slag completely floating more difficult to form a slag defects. Liquidity filler metal slag has great influence on the generation of defects. Stainless steel material of the molten metal poor mobility, coupled with the use of a small current narrow weld operation, the weld metal solidification, difficult to fully surfaced weld slag, slag formation of defects. Horizontal welding, soldering oblique welding head adopts lane, lane number as handled badly, can cause weld "dead", have a greater chance of slag defects.
Crack
TIG hit bottom as thin, stress will make it happen when filling tear caused by the formation of cracks; not timely sub-layer backing weld after welding, but also the cause of cracks. Preheat temperature and improper welding rod storage, improper use, will increase the chance of cracks.

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