Tensile properties of thin wall ductile cast iron containing chill structure were evaluated, and eddy current measurements were carried out to detect the chill structure which affect the tensile properties. Ten cast iron samples with six specimens were prepared. Tensile tests were performed on the four specimen of each sample and the eddy current measurement and the microstructure observation were carried out for one specimen. Tensile test results showed that chill structure shortens the elongation at break when the size or amount of the chill is large enough. Although the values of the elongation are different among samples that were cast in same mold, there is no difference on stress-strain diagram until braking. Eddy current signal indicates the difference of matrix and tensile strength. Chill structure can be distinguished with the signal distribution when the chill structure clusters, but it is difficult to find the small chill spread homogeneously. Sensitivity or resolution should be improved to evaluate various thin wall ductile cast iron samples.
