In the production of CV graphite cast iron, CV treatment alloy with high rare earth content is used. It has been reported to work as a substrate for graphite crystallization in spheroidal graphite cast iron and flaky graphite cast iron. In this study, the effect on graphite morphology was investigated by changing the amount of Mg and rare earth added. In addition, the graphite morphology during the cooling process was also clarified. The nucleus of primary graphite was qualitatively analyzed by water cooling at the primary temperature. The chemical composition of graphite nuclei changed with the amount of Mg and rare earth addition. Furthermore, the graphite morphology changed depending on chemical composition. It was also found that the appropriate amount of rare earth should be added according to the amount of Mg in the CV treatment alloy.

  Influences of carbides on three body abrasive wear behavior were investigated for carbon tool steels (SK85 and SK105), alloy tool steels (SKS3, SKD61, SKD11 and SKH51) and alloyed white cast irons (Ni-hard, 16%Cr and multi-component cast irons) by means of rubber wheel wear test using SiO₂ abrasives with 240μm in average diameter. Wear loss of the materials (SK85, SK105, SKS3 and SKD61) without crystallized carbides increased once up to the maximum hardness of 650 to 700HV30, and then, decreased. In the case of materials (SKD11, SKH51, Ni-hard, 16%Cr and multi-component cast irons) with crystallized carbides, the wear loss decreased gradually with an increase in hardness. It was clarified from the results obtained that the carbides crystallized in the materials played important roles in the behavior of the three body abrasive wear. Furthermore, in the steel materials without crystallized carbides, those containing secondary complex carbides with higher hardness and less retained austenite showed better wear resistance compared to the materials with secondary carbides with lower hardness and with some retained austenite. It was also found that the cast iron materials containing crystallized carbides such as MC, M₂C and M₇C₃ with higher hardness than M₃C carbide showed more outstanding wear resistance.

  Spheroidal graphite cast iron is a material with excellent mechanical strength and strong resistance to corrosion. However, shrinkage cavities may be generated inside this material during manufacturing. In this research, we propose a non-contact measurement method for detecting shrinkage cavity inside the cast iron using electromagnetic force vibration. In this proposed method, electromagnetic vibration is generated inside the cast iron from the static magnetic field, and the eddy current by the alternating exciting coil. When the cast iron is vibrated, the spatial magnetic field between the proposed sensor and the cast iron fluctuates. The fluctuation of the spatial magnetic field is detected by the Hall element. If there is a shrinkage cavity inside the cast iron, it presence will change the vibration intensity as well as the fluctuation intensity of the spatial magnetic field subsequently. Therefore, the shrinkage cavity is estimated by the fluctuation intensity of the spatial magnetic field between the sensor and cast iron. In this paper, the electromagnetic vibration and displacement inside the cast iron are calculated by 3-D nonlinear electromagnetic FEM analysis and displacement FEM analysis. The phenomenon of this proposed method is clarified using these FEM analysis methods and verification experiments. These calculations and verification experiments show that the shrinkage cavity can be evaluated from the fluctuation intensity of the spatial magnetic field.