MAGNETIC POWDER FLAW DETECTING METHOD OF STEEL TUBE

摘要

PURPOSE:To improve the accuracy of detection by insertig a copper pipe which has a slit part and incorporates an iron core into a steel pipe placed between two series coils in the same direction, feeding a rectified wave current to electrode plates at both ends, and supplying an alternating current to the coils. CONSTITUTION:The two coils 4 and 4' connected in series in the same winding direction are added to both ends of the steel tube 1 to be inspected, and the copper pipe 2 which has the slit part 2a bored axially and incorporates the iron core 3 is inserted. Then, the alternating current is flowed to the coils 4, 4' to supply alternating magnetic flux to the iron core 3, and the material 1 to be insepcted is magnetized with an induced current to detect a circumferential defect. Further, the electrode plates 5, 5' are brought into press contact with both end parts of the copper pipe 2 and a single-phase half-wave rectified current is fed from the same three-phase AC power source with the coils to detect an axial defect of the material 1 to be inspected. Consequently, defects in the inside of the material 1 to be inspected in all directions are detected at the same time speedily and accurately.