Defects Control of Welded Steel Pipe

When steel pipe manufacturer producing welded steel pipe, it is unavoidable that some welding slag inclusion and stomata defects may appear if workers don't control very well during operation. So we will talk about the causing reason of welding slag inclusion and stomata defects here, and then we will give preventive measures for you. More details are as follows.

Causing reasons of welding slag inclusion:

1) Back chipping after backing welding is halfway, which results in the root slag did not completely overflow when heat welding rapidly.
2) The way to backing weld back chipping may be wrong, so that the groove on both sides of root pass is too deep, and shows "W". In the rapid heat welding, the slag flowing into the deep trough is too late to overflow and form slag.
3) At 6 o'clock position, arc too fast is also easy to produce slag.

Preventive measures:

1)Using grinding wheel to remove slag after the backing weld, back gouging must be thoroughly, each joint point must be flat.
2)When back chipping the root weld bead will be clear into the "U" shaped groove, and avoid to be the "W" shaped slot.
3)When retreating the arc at 6 o'clock we need to fill the molten pool, and then move arc to the forming of the weld to collect arc, and use flat swing method to extinguish the arc.

Causing reasons of stomata defect:

1) The molten pool is overheating when cosmetic welding, and adsorb a lot of ambient air.
2) The amplitude of swing of welding rod is too large when cosmetic welding, the molten pool is be protected badly.
3) the root gap is too small, which is easy to produce root needle bubble.
4) The electrode is not used for a specified period of time or prolonged exposure to air.

Preventive measures:

1) The current should not be too large when capping, we should use the small current, short arc, and welding with fast welding speed to avoid overheating and prevent surface pores.
2) We should use the appropriate transport technology to weld, otherwise it will make the molten pool ahead, and easy to cause long short circuit and the electrode stick on the weld, which is unfavorable to deoxidize and easy to produce pores. But the width of electrode swing should not exceed twice the diameter of the electrode, otherwise it is easy to produce pores.
3) We should prevent the group on the gap is too small, if the group on the gap is too small, it will cause overlarge base metal dilution effect in the welding, and impede the exhaust, which will results in the root of bubbles.
4) Electrode should be stored in the electrode insulation tube in the use of the process. It is strictly prohibited that welding rod is exposed outward, we need to prevent the welding rod damp.