FLAW DETECTION OF CAST IRON TUBE

摘要

PURPOSE:To enable accurate detection of cracks free from scale by magnetic saturation of only surface scale with a fine d.c. magnetic field in the flaw detection. CONSTITUTION:When a specified magnetizing current is applied to an excitation coil 7 of an eddy flaw detector 1 being guided on the surface of a cast iron tube 2 with a roller 3, a fine d.c. magnetic field is generated between magnetic plates 5 and 6 to magnetically saturate on scale immediately under a flaw detection head 4. This prevents the generation of an induction current due to changes in the magnetic line of force of a magnetic scale thereby enabling the detection of cracks free from scale.