Evaluation for Electromagnetic Non-destructive Inspection of Hardened Depth Using Alternating Leakage Flux on Steel Plate

Many surface hardening steels are used for the crankshaft or machine parts, etc. in the automobile engine. The inspection of surface hardening depth is important in the quality assurance of the strength or their parts. Particularly, in order to raise the productivity of these parts, the non-destructive inspection method is needed for the evaluation of the hardened depth. The permeability and the conductivity of the hardened domain are smaller than the non-hardened domain in surface hardening-steel. Evaluation of the surface hardening depth is possible by detecting of difference of these electromagnetic characteristics. In this paper, the electromagnetic inspection method using the detecting of the leakage flux on the surface of the steel material is investigated. The leakage flux and flux density in steel material are estimated by 3D nonlinear finite element method (FEM). The usefulness of this proposal inspection method is shown also from comparison with a experimental verification.