Abstract
The magnetic diagnosis of iron-based materials was performed by using three kind of tools. Those are a triplefold coil for ac resistivity detections, a small Hall element for leakage flux observations after polarizations of the material and a magnetic Barkhausen noise pick-up coil combined with the excitation yokes. We found the first derivatives of the normal component of the leakage flux along the polarized direction well coincided with intensities of residual strains for ferromagnetic samplcs of A533B and S25C etc. Fur paramagnetic SUS304 samples, the polarity of the derivative was just reversed and was proportional to the induced martensitic transformations. An index derived by the magnetic noises well described the residual stress with its directions. All the parameters obtained by these electromagnetic tools were properly combined to judge the material degradations with high reliability.
