PROCESS FOR DETECTING DEFECTS ON A SURFACE BY EDDY CURRENTS AND DEVICE FOR CARRYING OUT SAID PROCESS

摘要

PCT No. PCT/FR85/00258 Sec. 371 Date May 20, 1986 Sec. 102(e) Date May 20, 1986 PCT Filed Sep. 20, 1985 PCT Pub. No. WO86/01896 PCT Pub. Date Mar. 27, 1986.A magnetic field is produced by way of an emitter placed close to the surface of a product to be controlled and a receiver separate from the emitter is placed, with respect to said emitter, on the one hand, in such a way as to be aligned with the emitter in a direction corresponding to the general orientation of the defects to be detected on the surface of the product, and on the other hand, so as to avoid any substantial direct influence from the eddy currents generated by the emitter when the product surface is defect-free, so that a significant signal is only picked up by the receiver in the case of a deviation of said eddy currents in its direction due to a discontinuity in the surface of the product. The invention finds an application in the detection of surface defects in semi-finished metallurgical products and in particular continuously cast steel products.