MAGNETIC INSPECTING METHOD AND DEVICE THEREFOR

• Main Authors: SEIGO ANDO, YASUHIRO MATSUFUJI
• Format: Patent
• Language: English
• Published: 07.09.1992
• Edition: 5
• Subjects: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES; MEASURING; PHYSICS; TESTING

In the method and device, a magnetizer (4) is so provided that its paired magnetic poles (4a, 4b) face a material (10) to be inspected, a magnetic field is generated in the material (10) by the magnetizer (4), a magnetic sensor (7a) is provided at the nearly central part of the line segment, by which the twin magnetic poles (4a, 4b) are connected, or of a line segment parallel with it, and shielding bodies (22a, 22b, 23a, 23b) of low coercive forces are provided respectively on the sides of the magnetic sensor (7a), which face the magnetic poles respectively. Magnetic leakage fluxes caused by defects in the inside or on the surface of the material (10) are sensed by the magnetic sensor (7a). In the device, the distance (2A) between the shielding materials (22a) and (22b) is so set as to be more than 2.2 times and less than 2.8 times as long as the distance (L) between the magnetic sensor (7a) and the material (10). Each of the shielding bodies (23a, 23b) comprises a vertical part (24a) and a horizontal part (24b) both forming an L-shape in cross section. The width (2A) of the horizontal part (24b) in the direction, in which the magnetic poles (4a, 4b) are arranged, is so set as to be more than 0.4 times and less than 0.6 times as long as the distance (B) between the magnetic poles.