Mechanical properties of the spheroidal graphite cast iron are dependent on the spheroidized graphite. In the field of casting, rare earth (RE) is used in a spherical shape of the graphite. However, domestic production of RE is small, I rely on imports. Therefore, reduction of the RE elements is an issue. In this experiment, as compared to the previous studies were produced spheroidal graphite cast iron by using a sphering agent unified element other than RE, we were subjected to fatigue tests. From the results, RE in spherical agents is I have investigated the effect on the test specimen. Test specimen the RE content of 0%, 0.3%, 0.5%, using a 1.0% four types of smooth test specimen were subjected to fatigue tests by a plane bending fatigue tester. Decreased fatigue strength is about 20-33% in the RE0% test specimens were compared with RE-containing test specimens. Result of cross-sectional observation of the fractured test specimen by the test, a large casting defects were observed inside the RE0% specimens. Thus the fatigue strength it is believed to have significantly reduced.
