Shrinkage cavities and flaws sometimes occur inside spheroidal graphite cast iron during the manufacture process. It is necessary to detect these flaws to guarantee quality. Generally, ultrasonic testing is used to detect opposite side flaws in the spheroidal graphite cast iron. However, because it is a contact testing method using media such as water, it takes a long time. On the other hand, electromagnetic testing is a high speed non-contact useful method for detecting flaws in cast iron.
In this paper, electromagnetic testing using alternating (AC) and static (DC) magnetic fields was proposed for detecting opposite side flaws in spheroidal graphite cast iron. The proposed method was investigated by experiments and 3-D non-linear electromagnetic field analysis using finite-element method (FEM) taking into account magnetic characteristics with minor loop curve and eddy current in spheroidal graphite cast iron. The results showed that opposite side flaws in spheroidal graphite cast iron can be detected by using the synthetic magnetic field of DC and AC magnetic fields.
