Method of detecting surface dfect of non-magnetic material

Abstract

Abstract PURPOSE: To detect surface defects, by impregnating the surface openings of non- magnetic materials (austinite stainless steel, copper alloy, etc.) with a liquid containing fine magnetic powder and by detecting the amount of magnetism of the magnetic material remaining in the openings by the electromagnetic induction or magnetic field detection method. CONSTITUTION: Magnetic colloid solution is made of fine magnetic powder of 1 to 100mμ suspended in water or oily solvent. A penetration test method is applied for impregnation. Excess liquid may be wiped off with dry clth or by the application of an emulsifier and water spray. Thus the defective surface openings are impregnated with magnetic colloid solution. Next, defective openings are detected by the electromagnetic induction or magnetic field detection method. Here, the electromagnetic induction method will be explained. DC current of oscillator 5 is fed to test coil 3 via detector circuit 6 and cable 4, and eddy currents are produced by the magnetic field of the test coil on specimen 1. Their variation is converted into an electrical signal by detector circuit 6. Signal processing circuit 7 operates noise processing and others, and the results of the test are displayed by display 8. COPYRIGHT: (C)1980,JPO&Japio

Inventors

• 👤 Hideyuki Ito
• 👤 Ichizo Uetake
• 👤 Yoshinori Kuwae

Bibliographic Details