First, in the
ssaw steel pipe production test, there had been no detection of spiral steel pipe through the wall with a large hole phenomenon MFL method. Management and human factors aside, technically should probe into the scoreboard and to guard against. For the method can be used MFL stuck deep surface defects, there has been no clear conclusion. It has a relationship with the instrument and probe performance and defect size and shape. Since the detection of high speed through the coil ET method is widely used for many years to detect spiral steel quality, especially its compactness.
Second, the use of proven, it is difficult to ferromagnetic spiral pipe stuck in the crack-like defects, so the high standards of ET, using the probe coil ET method. In addition, the ET method can actually stuck his face hidden deep lack of such a simple question, it seems so far not formed a clear consensus.
Third, spiral pipe often produced "outside the fold" such defects, a lot of eddy current probe instrument and often can not be found. Often outside off to the naked eye visible, but not the only instrument ET alarm embarrassing phenomenon. Since the emergence of sector-type vortex phase alarm device, this situation has been fundamentally changed.
Fourth, select the appropriate instrument with the probe and adjust it correctly, it is still an important issue can not be ignored. Another important factor is the reliability of the natural angle of the tube surface defects. Theoretical and experimental studies have shown: When the orientation of artificial groove along the thickness direction of the outer surface of the tube angle is 30 degrees, that can not be detected by MFL parallel to the surface defects, such as class stratification defect.
