Small amounts of the following various elements were added to high purity white cast irons, whose chemical compositions were adjusted to 2.4%C, 1.1%Si, 0.01%P, 0.01%S. Three values of the Mn content were used: 0.04%, 0.15% and 0.3%Mn, (Mn/S ratio; 3∼5, 15∼25 and 25∼35). The elements were: Cu, Ag, Mg, Ca, Zn, Cd, B, Al, Ti, Sn, Pb, V, Nb, Ta, Ce, N, P, As, Sb, Bi, Cr, Mo, W, Co, Ni and Te.
  Melting of the specimens was carried out mainly by carbon resistance electric furnace (Kryptol). In the case of nitrogen, a vacuum high frequency induction furnace was used. Alloying elements were added as high purity ferro-alloys, pure metals or nitrogen gas.
  The required times for the first- and second-stage graphitization were measured by a dilatometric method, which was carried out at 950°C (first-stage) and about 700°C (second-stage), respectively.
  Mn up to 0.5% promotes the first-stage graphitization. Mn up to 0.15% promotes the second-stage graphitization, but Mn beyond 0.3% retards it.
  In the case of the first-stage graphitization, B(<0.01%), Ca and Mg are the strongest graphitizers, Ti(Mn/S ratio 4), Zr and Al are strong, and Ti(Mn/S ratio 20, 30), Ni, Co, Cu, Pb, Ag, As, P and Sn are weak graphitizers. Zn, Ta, W, Sb and Cd show almost no effect. Ce(<0.02%), Mo, Bi and Nb are moderate anti-graphitizers, Cr and V are strong and B(>0.01%), N and Te are the strongest anti-graphitizers.
  In the case of second-stage graphitization, the effects on the graphitization of cementite are similar to the first-stage graphitization, except for some elements. P(>0.06%), Sb, As and Sn show no effect or rather are weak graphitizer in the first-stage, but in the case of second-stage graphitization, these elements become strong anti-graphitizers.
  The graphitization of cementite is a function of the bond of cementite, the carbon activity, the diffusion rate of carbon atoms and the nucleation frequency of graphite. Further, it is necessary to consider the interaction between various elements and N or S, etc.
  Effects of various elements on as-cast and annealed structure were also studied.
  These results may be of use not only in malleable cast iron production, but also in the gravity diecasting technique of flake and spheroidal graphite cast iron.

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  Research on the drying process of moisture-condensed layer in the green sand mold was promoted on the basis of the behavior of moisture-condensed layer. The concept of heat transfer with the change of state was clarified.
  Boundary condition which changes from condensation zone to dry zone could be obtained from the change of state. Moisture is evaporated by the heat which passes the dry zone.
            λ ∂θ⁄(∂x) = Lρm dx⁄(dt)
 where  λ; thermal conductivity, Cal/cm.sec.°C
          θ; temperature, °C
          L; latent heat of vaporization of water, Cal/g
          ρ; mold density, g/cm³
          m; ratio of water content in the moisture-condensed layer
  Evaporation constant C which represents the movement of dry zone from boundary condition was calculated. This evaporation constant varied with thermal conductivity of dry zone, amount of moisture and pouring temperature. Temperature distribution in the dry zone can be calculated by introducing the evaporation constant.
            θ = 100-θ_ierfc(c/2√k)⁄(erf(c/2√k)) - 100-θ₀⁄(erf(c/2√k)) erfc (x⁄(2√kt))
 where  θ_i; metal/mold interface temperature, °C
          θ₀; initial mold temperature, °C
          k; heat transfer rate, cm²/sec
The formula is effective where the temperature is higher than 100°C. Because this is an analytical solution, good approximate values were not always obtained, but it is sufficient for seeing the tendency in temperature distribution.

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  The degree of supercooling and the freezing rate during solidification govern the solidfied structures. These factors depend on heat transfer through the mold, pouring temperature and liquidus-solidus range of the alloys. In the present work, the degree of supercooling and the cooling rate were determined by thermal analysis during freezing, and the structures were observed microscopically. Aluminum alloys such as Al-1∼3%Mg, Al-1∼33%Cu, Al-0.5∼20%Si and some ternary alloys were melted at 850°C and cast into molds made from various materials. To ensure rapid response to changes in temperature, special electric circuit was used in the temperature measurement.
  At a coolig rate higher than about 50°C/sec, the degree of supercooling ΔT depended upon the cooling rate v, in a relationship ΔT²=K₁·v
  The correlation between three factors, namely the degree of supercooling, cooling rate and solute concentration was obtained graphically. When the solute concentration is below the eutectic composition, the solidified structures varied in the following order with the increase of cooling rate : structure having primary crystallized solid-solution in which the solutes dissolved non-uniformly : structucture having primary solid-solution of uniform concentration : and finally at very high cooling rate, structure having primarily crystallized metastable supersaturated solid-solution or a two-phase structure in which one phase is this metastable solid-solution. The critical conditions for the transition from structures of non-uniform one to uniform are in a linear function ΔT²=K₂v+K₃. The constant K₂ and K₃ depended upon the solute concentration. The minimum cooling rate necessary for the structure to have a uniform solid-solution increased in order of Al-Mg, Al-Si and Al-Cu alloys successively.
  In the hyper-eutectic Al-Si alloy, it was shown that the eutectic composition of Si moved to a higher value over a certain cooling rate.

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  It is important from the standpoint of casting or metallurgical industry to study the physical property of partially solidified alloys. An empirical study on the apparent viscosity of partially solidified Zn-Sn and Al-Cu alloys was carried out, and the theoretical and technical problemes on viscosity measurement were fundamentally discussed. The values of viscous torque were measured using an inner cylinder rotation type viscometer and by comparing with the standard viscosity of glycerin, they were calibrated for the apparent viscosity of the alloys.
  The apparent viscosity for the mixture of glycerin and some amount of powders of oxides or graphite moderately increases with the concentration of powders up to 20vol%, but fhe viscosity at higher concentrations increases rather rapidly, the increment of which is greately influenced by density, shape and grain diameter of the suspended powders.
  A similar behavior to the mixture of glycerin was observed for the apparent viscosity of partially solidified alloys, the values of which decreased with the increase of shearing velocity. The relation between the apparent viscosity and the fraction of solid markedly varied with the chemical composition of alloys. In order to determine the apparent viscosity accurately, it is neccesary to maintain the laminar flowing condition over a wide range of viscosity and to keep a constant rate of solidification.
  It was shown from microphotographic observations that the primary dendritic solids were broken down and transformed to a rather rounded shape during the viscosity measurement, i.e. while stirring the partially solidified alloys.

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  There is a general agreement that the graphite nodule number in black-heart malleable cast iron is an important ferritization rate-determining factor. The authors reported in a previous paper that the rate of ferritization in spheroidal graphite cast iron can be explained from the distribution or graphite nodules and the diffusion of carbon through the ferrite shell around the nodules, but they did not directly indicate the effect of graphite nodule number on the ferritization. In this paper, the effect of graphite nodule number on the rate of ferritization during isothermal annealing in black-heart malleable and spheroidal graphite cast irons were evaluated mathermatically and experimentally.
  In the direct transformation of black-heart malleable and spheroidal graphite cast irons, the isothermal annealing time t, to get the same level of ferritization is inversely proportional to Nv^2/3 or to N_A, where N_V and N_A denote the graphite nodule number per unit volume and the graphite nodule number per unit area, respectively. In the indirect transformation, the effect of graphite nodule number on the rate of ferritization during 720°C isothermal annealing in black-heart malleable cast iron is almost the same as that in direct transformation. But in spheroidal graphite cast iron the effect of nodule number becomes less as the annealing temperature is lowered. An increase in silicon content of the cast iron causes a marked increase in the growth rate constant of the ferrite layer.

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  Only a few study on the aging phenomenon in cast iron, such as the studies on age-hardening in nickel-aluminum-containing ferritic spheroidal graphite and ferritic malleable cast iron, are reported. To clarify the aging phenomenon in aluminum-containing ferritic spheroidal graphite cast iron, the cast iron was prepared by adding 0∼3% of aluminum and 2% of calcium cyanamide before graphite spheroidizing treatment with magnesium. The specimens were annealed at 950°C for 2hrs., slowly cooled to 720°C, held at this temperature for 2hrs. and water-quenched before aging treatment at 550°C, 600°C and 650°C.
  The hardness of ferritic matrix increased by aluminum addition and became harder by the aging treatment. The precipitates were suggested to be AlN and Si₃N₄ by microscopic examination and nitride analysis. The size of precipitates in the over-aged specimen was about 0.5μ. The tensile strength increased about 4kg/mm² after the aging at 550°C for 500min in iron containing 3.23%Al.

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  In general it is considered that the unsoundness of pure copper castings is mainly caused by the steam generated by the reaction between hydrogen and oxygen absorbed in molten copper. In the present work, the behavior of oxygen and hydrogen in the melting and pouring processes of pure copper was quantitatively analysed and the effects of gases on the soundness of castings were determined.
  When molten copper (1,230°C) was oxidized in the atmosphere, the oxidation rate was in good agreement with the previously reported values for the 25min from the start of oxidation. The flux cover on the surface of molten copper was necessary to keep the oxygen content at a minimum and the graphite cover was best. Oxygen content in molten copper was 0.34% in weight when the flux was not used, 0.072% when a strongly oxidizing flux powder was used and 0.004% when graphite powder was used.
  In general, when phosphorus was added, hydrogen content was high while oxygen content was low. However, the melt with oxidizing flux cover showed low hydrogen content even with low oxygen content.
  The density of sand mold castings increased with pouring distance, due to the evolution of hydrogen during the pouring process. When phosphorus was not added, the densities of sand and permanent mold castings depended on the hydrogen content. Both castings gave low figures when the hydrogen content increased up to 0.00007%. When phosphorus was added, the density of sand mold castings depended upon the hydrogen content and low figures were obtained when the hydrogen increased up to 0.00015%. However, the density of permanent mold castings was not affected by hydrogen content.

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