Recent progress in the compound magnetic field inspection systems

Newly developed inspection systems using the compound magnetic field method are now operating for the detection of surface flaws in seamless tubes and pipes. In this method, the material to be tested is magnetized in various directions, and any surface flaws cause magnetic leakage fields and reaction fields due to induced eddy currents. Both spatial magnetic fields can be detected by magnetic sensors. This method also evaluates quantitatively surface flaw size, classifys several types of flaws and is applicable not only to ferromagnetic metals but also to non-magnetic metals. Several types of inspection systems using these features have been developed. In this paper, an outline of newly developed inspection systems for cold forged automobile steel parts, steel bars and austenitic stainless steel tubes is described.