Microstructural parameters which govern fracture toughness of spheroidal graphite iron castings such as graphite nodularity and size of the castings 480mm in wall thickness were studied. The fracture toughness of ferritic spheroidal graphite iron castings is related to the graphite size irrespective of nodularity. The elongation strongly depends on graphite nodularity. No relation lies between fracture toughness and elongation. A mechanism is described in terms of the spacing and notch effect of graphite nodules in the matrix to explain these correlation.

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  A packed bed model was used to clarify fundamental conditions on the heat transfer in a preheating zone of cupola. The apparatus consisted of a cylinder 160mm in inner diameter installed with iron grating on which a layer of steel ball packed bed 100 to 200mm in thickness had been charged. Steel balls were 20 to 40mm in diameter. Hot gas was blown into the bed from the bottom at flow rates 4 and 6m/s. The diameter of balls has the most significant effect on heat absorption of the bed. The heat is accumulated in the bed faster as the ball diameter is smaller and a difference of temperatures of balls and gas is rapidly lost. The heat transfer coefficient h is represented as : h = W^0.83 T^0.3/D^1.03 where W is flow rate, T gas temperature and D ball diameter. The values by the use of this equation are in good agreement with those in other works.

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  Dispersed porosities in Na-treated Al-Si alloy castings are caused by retained gases absorbed in the molten metal during Na-treatment. Degassing after Na-treatment can eliminate dispersed porosities in the castings and the shrinkage behavior varies from porosity dispersion type to concentrated shrinkage porosity type. When Na is added to Al-Si alloys, they have greater limiting solid fraction of feeding and can be fed until they have higher solid fractions. The Na-treated alloys can produce sound castings free from concentrated shrinkage and dispersed porosities, even if small risers are applied.

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  Changes in structure and distribution of carbon in austenite were measured quantitatively of spheroidal graphite cast irons quenched at different stages of heat treating. The austenitizing reaction rate rises significantly with increasing pearlite in the initial structure of the iron. Austenitization of ferritic ductile cast iron is controlled by diffusion of carbon through austenite. Homogenizing results in continued transfer of carbon from nodules until carbon saturates in austenite. Pearlitic ductile iron transforms to austenite in which carbon almost saturates. The bainite transformation of ductile iron proceeds in the mechanism similar to that in high carbon and high silicon steel except that transformation of the former delays and larger volume of austenite (γ pool) remains in intercellular regions even at the final stage of reaction. Austenite transforms at first to ferrite, and carbon supersaturated in ferrite diffuses to surrounding austenite at high temperatures, while it precipitates in the form of carbide at low temperatures. Carbon distiributes nonuniformly in untransformed austenite with the lowest carbon in γ pool. Changes in amount of retained austenite and nonuniform microhardness of the matrix reflect heterogeneous distribution of carbon in austenite at isothermal transforming temperatures.

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  Spheroidal graphite cast irons containing four levels of Ni 0 to 3.5wt% and ones containing five levels of Mo 0 to 0.6wt% were prepared by the use of an induction furnace and cast. The iron into which Ni has been separately added has improved tensile strength and hardness because of solution hardening in the matrix. The impact transition temperature rises with condensation of Ni, while the upper shelf absorbed energy reduces. Separate addition of Mo has little effect on tensile strength and impact properties. Mechanical properties of spheroidal graphite cast iron can be improved by combined addition of Ni and Mo. The irons containing 1% Ni-0.1%Mo and 2.5%Ni-0.4%Mo show the lower impact transition temperature and have high toughness.

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  Gray cast iron and high strength and heat resistant silicon carbide fibers were used as a base metal and composite component respectively. Composite materials were prepared by immersing at different temperatures and succeeding holding for different times by the use of specially designed jig. Some composites were heat treated. Immersing at 1,200°C without holding before cooling ensures the optimum microstructure. Some intermetallic Fe-Si compounds are formed by mutual diffusion of Fe from molten metal and Si from SiC. This reacted layer thickens with prolonged holding times both in composite processing and in post heat treating. A structural model is proposed for the forming process of reaction layers at composite interfaces.

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  Molten Cu alloys were cast into spheroidal graphite cast iron molds 180mm in inner diameter 300mm in outer diameter and 350mm in height and were pressed under pressures from 0 to 98MPa for 0 to 4min. The ratio of equiaxed grain zone in a micrograph of each ingot takes up about 65%. Remarkabiy fine equiaxed grains only form near the center of the ingot solidified under a light pressure 9.8MPa. When an ingot is pressed at a pressure over 40MPa for 4min, shrinkage defects significantly decrease. It is important to prevent shrinkage defects to keep the pressure higher than the strength of the ingot at relating temperatures till the ingot completely solidifies. The resultant ingot has excellent mechanical properties.

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