Causes and preventive measures of stainless steel welded pipe defects

Stainless steel welded pipes will have some defects in the welding process. The defects of stainless steel welded pipes will lead to stress concentration, reduce bearing capacity, shorten service life and even cause brittle fracture. General technical regulations stipulate that cracks, incomplete penetration, unfused and surface slag are not allowed; defects such as undercut, internal slag and pores cannot exceed certain allowable values, and must be thoroughly removed and welded for excessive defects. Make up. The causes, hazards and preventive measures of welding defects of common stainless steel welded pipes are briefly described below.


　　First, the weld size does not meet the requirements


　　The weld seam size does not meet the requirements mainly refers to the weld height and residual height difference, the weld width and width difference, the wrong side amount, the post-weld deformation and other dimensions that do not meet the standard requirements. The weld seam is uneven, uneven and deformed. Great. The weld width is inconsistent, in addition to causing the weld bead to be unsightly, it also affects the bond strength between the weld and the base metal; if the weld height is too large, causing stress concentration, and the weld is lower than the base metal, there is not enough Joint strength; if the wrong side and deformation are too large, the force transmission will be distorted and stress will be concentrated, resulting in a decrease in strength.


　　Causes: improperly angled or unblind edge of stainless steel welded pipe and uneven assembly gap; unreasonable selection of welding process parameters; low skill level of welders.


　　Precautionary measures: select the appropriate groove angle and assembly clearance; improve the assembly quality; select the appropriate welding process parameters; improve the welder's operating technology level.


　　Second, undercut


　　Due to incorrect selection of welding process parameters or incorrect operation process, the grooves or depressions formed by burning along the base material of the weld toe are called undercuts. The undercut not only weakens the strength of the welded joint of the welded pipe, but also causes cracks due to stress concentration.


　　The cause is: the current is too large, the arc is too long, the angle of the electrode is not correct, and the method of transporting the strip is improper.


　　Preventive measures: When welding arc welding, it is necessary to select the appropriate welding current and welding speed, the arc can not be pulled too long, the angle of the electrode should be appropriate, and the method of transportation should be correct.