Eddy Current Testing (ECT) was applied to non-destructive evaluation of artificial cracks, 0.25 mm in width made by electro discharge method, and internal defect, 1.6 mm diameter drill hole under the surface, in cast iron. It is important to select suitable frequency and coil for measurement to receive higher SIN signal, because small skin depth caused by ferromagnetism of a matrix limits measurable depth and inhomogeneous structure produces strong noise signal. Measurable crack depth was less than 3 mm when using two coil method. Direction of the crack could be determined from Lissajous patterns of the ECT signal. The signal changed linearly when two coils set in right angle to the crack, but showed curve when two coils set parallel with the crack. On the other hand, detection of internal defect of cast iron was difficult because change in Lissajous patterns of the ECT signal by a drill hole under 0.5 mm from the ground surface was weak as compared to higher noise signal induced by inhomogeneous matrix.

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  Since electric conductivity and permeability of spheroidal graphite cast irons depend on their matrices such as ferrite, pearlite and cementite : ledeburite and free cementite, there is a possibility that eddy current method can characterize matrices of spheroidal graphite cast irons. In this study, electromagnetic properties of spheroidal graphite cast irons were examined in order to discuss the possibility of detection of cementite in spheroidal graphite cast irons using eddy current method, and consistency between electromagnetic properties and eddy current signals was discussed. For the purpose, three kinds of specimen groups were prepared : (1) 8 specimens of a 5-step bar type, (2) 10 specimens cut from actual casting products and (3) 4 specimens of 2 to 6 mm thickness. Results of measurement of electromagnetic properties showed that both conductivity and permeability of cast irons decrease as cementite content increases, respectively. The eddy current method was applied to characterize specimens of different contents of ferrite, pearlite and cementite. It was found that inclusion of cementite can be detected through eddy current signals on the complex plane of impedance, in addition to ferrite and pearlite ratio. It is consistent with the results of electromagnetic measurements, and supports for the fact that the eddy current method has a capability to detect cementite nondestructively.

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  A magnesium alloy was adopted to an evaporative pattern casting (EPC) process to combine each advantages of the magnesium alloy and the EPC process. In the present study, with the aim of developing complete EPC process for the high productivity of magnesium alloy castings, the foam patterns were cast at top gating system under atmosphere and reduced pressure for evaluating casting characteristics of AZ91D. Filling time and temperature of molten metal were measured during mold filling. It was recognized that an average filling velocity was affected by difference of the coating material and the degree of reduced pressure. The grain size of the magnesium alloy was slightly dependent on the degree of reduced pressure. It was considered that the application of the high reduced pressure, which changed the shape of melt surface from convex to concave, was related to the occurrence of internal defects such as a cold shut lap or a fold of the casting.

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  To obtain the grain refined structure of Cu-Ni alloy, Cu-1.5, 3.0, 6.0, 9.0 and 12.0 mass%Ni were melted and poured onto an inclined cooling plate and into a graphite crucible. After leaving for 5, 15 and 30 seconds in the crucible, semisolid slurries were cast into a permanent mold. Influences of Ni content, casting temperature, holding time of the semisolid slurry in the preheated crucible on the grain refinement and the hardness of the ingot were examined. When the inclined cooling plate was not used, dendrite crystal structures were found to appear. Quenched samples taken at the inclined cooling plate indicated fine primary crystals. This suggests that the inclined cooling plate is effective for generating fine crystal and semisolid slurry. The most grain-refined structure was obtained by the addition of 12 mass%Ni and casting at the lowest liquidus temperature of 1443 K and the shortest holding time of 5 seconds. The highest hardest semisolid cast ingot was obtained with the ingot with the finest grain structure.

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  Since cast iron is a compound material of steel and graphite, its mechanical properties change according to the amount, form and distribution of the graphite. In this paper, the effects of graphite on the mechanical properties were kept constant. That is, the eutectic graphitization ability (EGA) in gray cast iron was limited to approximately 50%, and in the case of spheroidal graphite cast iron, the nodularity was maintained above 80%.
  This paper presents a method of determining the mechanical properties from the hardness. First, the relationship between hardness and tensile strength was established and then the relationship between tensile strength and various mechanical properties was determined. From the data thus obtained it was possible to determine the various mechanical properties only from the hardness.

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