Simultaneous estimation cementite content and non-contact distance in spheroidal graphite cast iron using electromagnetic sensor

The cementite is often deposited on spheroidal graphite cast iron materials used in industrial machinery during manufacturing. Since the cementite is extremely hard and brittle, the cast iron may be damaged when the stress is impressed to the cast iron containing the cementite. Therefore, it is important to estimate the volume fraction of cementite contained in cast iron. However, at present, destructive inspection is generally performed to estimate the presence and volume fraction of cementite in the cast iron. In this research, an electromagnetic non-destructive inspection method to estimate whether the cementite is contained in spheroidal graphite cast iron is proposed. The surface of the cast iron is rough, so the distance (lift-off : Lo) between the electromagnetic sensor and the cast iron is changed slightly depending on the measurement position. By this method, lift-off (Lo) and the cementite content can be detected with an accuracy of less than about 10%.