Compacted vermicular graphite cast irons including different amounts of pearlite were cast to attain a relation between the amount of pearlite and the mechanical properties. Ferritizing annealing and pearlitizing normalizing were also tested to improve the ductility. The tensile and impact properties depend on the amount of pearlite in the matrix. A transition phenomenon is found at the pearlite content about 40%. The graphite morphology also depends on the structure of the as-cast matrix. Both the graphite morphology and the matrix structure shall be examined prior to the heat treatment to control the ferritic or pearlitic matrix by heat treating.

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  Assuming that graphite nuclei originate prior to bulky solidification and don't originate after that time, and that the liquid immediately cools down to the eutectic temperature and maintains the eutectic isotherm once solidification starts, two equations are derived.
        N_A^1/2⋅r_p = K_RX_t^1/3
        N_A⋅t = f (X_t) / K_r D_m
where r_p is the graphite radius; N_A, the number of graphite nodules; t, the time; X_t, the extent of primary reaction; K_R and K_r are constants as a function of various graphite concentrations; and D_m, the diffusion coefficient of carbon in the melt. The numerical calculation for cast irons with certain chemical compositions indicates that the primary graphite grows at an extremely rapid rate compared to the actual and ordinary casting. Cast iron with the composition of 3.5% C and 4.5% Si having N_A 1,000mm⁻² or more, for example, will finish its primary solidification within approximately 0.1 sec.

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  The graphite structure in cast iron was analysed on the basis of mathematical morphology using the texture analysis system. A graphite image was eroded by a couple of points and a linear segment of one dimensional structuring element. The area fraction of the eroded graphite image was measured. The covariance given from the eroding process by a couple of points shows the shape, size, distribution, anisotropy and presence of clusters, of complicated graphite structures on the same coordinate. The erosion by a linear segment shows the mean, maximum size and anisotropy. Although the method of quantitative analysis of various types of graphite has not been established, the use of covariance is worthwhile.

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  The influence of silicon content and number of graphite nodules on the continuous heating transformation of cast irons was studied by dilatometric and metallographic methods. The continuous transformation temperature Ac₁ rises with increasing rate of heating. The Ac₁ temperature rises greatly at higher rates of heating with decreasing the number of graphite nodules. When the silicon content is within the range of 1 to 3%, the Ac₁ temperature is shifted slightly upward as the silicon content increases both in ferritic and pearlitic initial matrices, and rapidly upward with still more silicon content. The Ac₁ temperature is higher in ferritic matrix than in pearlitic. The transformation time is shorter at higher heating rates and is somewhat affected by the silicon content.

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  The preceding paper described that manganese in liquid high-manganese cast steel makes a smooth semifused shell at the metal-mold interface and prevents burning of olivine sand mold. A comparison was made between olivine and silica sands, and the effect of manganese coating on olivine sand on burning was investigated in the present work. No burning takes place between olivine sand and low carbon cast steel, but a small quantity of manganese from the steel diffuses into the olivine sand at the metal-mold interface. The low carbon cast steel penetrates into the silica sand mold. The low carbon steel and silica sand are combined into fayalite containing a small quantity of manganese at the metal-mold interface. Manganese in liquid high manganese cast steel diffuses into the mold, and manganese and silica sand are combined into molten 2MnO⋅SiO₂. But the high-manganese cast steel does not penetrate into silica sand because of low pressure of the molten metal. Manganese coating of olivine sand prevents the burning of low carbon cast steel.

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  A mixture of P₂S₅ and NaCl was tried to use as a grain refiner for primary silicon in the hypereutectic Al-Si alloys. The primary silicon crystals in the alloys are refined by addition of P₂S₅ and NaCl. The maximum refining is achieved when the alloys are treated with 0.6% P₂S₅ and 0.4% NaCl at 850°C. The refining effect of the mixture is independent of the holding time of the melt after addition. NaCl promotes the refining effect of P₂S₅. The average size of primary silicon crystals decreases with increasing NaCl content.

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