NONDESTRUCTIVE INSPECTING METHOD FOR CENTER SEGREGATION OF STEEL MATERIAL

摘要

PURPOSE:To speedily and quantitatively grasp the extent of the center segregation by scanning the surface of the steel material to be inspected with a probe which has an exciting coil and an induced current detection coil and finding the difference of an induced current with the position of the steel material. CONSTITUTION:The steel material 1 is an intermediate blank material which is expected to be worked by cold multistage front extrusion, cold drawing, or center-part long-hole boring after the inspection of the center segregation, etc. While the probe 4 is brought into contact with the surface 2 to be inspected, the surface is scanned along a probe scanning line 3, an area range of phi2mm is AC-magnetized by the exciting coil 5, and the induced current generated by the magnetism is detected by the induced current detection coil 6. The differences DELTAI between the induced currents at and nearby the center part 7 and a reference value which is the value of the induced current at a part where a constant value is obtained is found to find the maximum value of DELTAI, thereby grasping the extent of the center segregation quantitatively.