This report is one of the series of fundamental studies on ferritic cast iron. The purpose of this investigation is to produce ferritic cast iron in the as cast state without heat treatment. In this study, the cooling rate after freezing in shell mold was measured, and the relation between the cooling rate, the carbon content and the quantity of ferrite in the matrix structure was examined.
  The ferrite area ratio in the matrix structure (F) decreased with the increase of cooling rate (V) after freezing, and a following relation was established ; F=−a√V+b, where a and b are constants. The influence of cooling rate on the ferrite area ratio in matrix structure decreased with the increase of S_cvalues. Between Laplanche’s coefficient of graphitization (K) and the maximum cooling rate (V_m) to obtain a perfect ferritic matrix, a relation of log K=p(−logV_m)+q was established, where p and q are constants.
  The ferrite area ratio in the matrix structure increased with the increase of eutectic reaction time and eutectoid transformation time. It was known that the influence of cooling rate on the ferrite area ratio in the matrix structure is highest in the neighborhood of eutectoid transformation temperature.

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  Unidirectional solidification of iron-cementite ally (Fe-4.28%C-3.86%Cr) was experimented under the following controlled conditions : the temperature gradient in the liquid ahead of the solid-liquid interface was about 5°C/mm and the solidification rates were 12, 6, 4, 2 and 1mm/hr. The specimens of 14mm diameter ×100mm long were melted and moved at the above mentioned constant speed through a vertical electric furnace.
  The solidification interface of ledeburite eutectic was perturbed when the solidification rate was fast, but it became planar without primary cementite crystallization when the rate was slow. The primary cementite section was characteristically “ L-shaped ”. This cementite which was located at the center and/or boundary of eutectic structure controlled the growth direction of eutectic lamellae. At slow solidification rates, ledeburite lamellae were aligned by the decrease of lamellar faults.
  Inter-lameller spacing λ changed with the relation of λ=A⋅Rⁿ, where R is the solidification rate, and A and n are constants. In the present investigation, n was estimated to be apout −1/3 for Fe-C-C₁ alloy.

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  The generation and behavior of H₂ and H₂O microscopic gas porosities are wto important variables controlling solute redistribution and inverse segregation in copper-tin alloys. These variables were determined in unidirectionally solidified castings.
  H₂ microscopic gas porosities are formed continuously in the cell boundary, and H₂O porosities, discontinuously and spherically, in the cell boundary. H₂ microscopic gas porosities markedly force out solute tin on the growth front of porosities accelerating the concentration of tin while H₂O microscopic gas porosities slightly condense tin around the porosities. Solidification under H₂ atmosphere accelerates inverse segregation, because it is accelerated by the increase in microsegregation.

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  By statistical research on the effect of melting procedure on the ductility of cast steel, it was verified that sulphur has an unfavourable influence on the toughness of cast steel, especially elongation, reduction of area and impact value. In order to clarify the influence of sulphur on the mechanical properties of cast steel, several SC42 specimens with varied sulphur content from 0.01% to 0.06% using pure iron as base materials were melted and cast.
  Mechanical properties of cast steel deteriorated with increase of sulphur content. Elongated inclusions with forging in cast steel increased by sulphur addition. Meshy inclusions which appeared in austenite grain boundaries of high sulphur specimen were principally (Fe, Mn)S inclusions. It is considered that these turned into elongated inclusion by forging. There were many spherical inclusions in the dimples of the fractured surface of high sulphur content specimen and they were (Fe, Mn)S inclusions. Because of the above, the increase in the (Fe, Mn)S inclusions in the austenite grain boundaries resulted in the decline of mechanical properties of cast steel.

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  In the present work, the transient method was applied for the measurement of thermal conductivity of copper castings in the temperature ranges of 20°C∼600°C. In order to examine the accuracy of this method, the determined values were compared with previously reported values and effects of the amount of phosphorus, tin and porosity on the thermal conductivity were determined and the correlation between thermal and electrical conductivity was determined experimentally at 20°C.
  The thermal conductivity of oxygen-free copper was 0.95 cal/cm⋅sec⋅°C and the value was in good agreement with previonusly reported ones. Variation coefficients at 20°C and 300°C were 0.96% and 1.3%, respectively. Thermal conductivity of copper castings increased with the increase in temperature when the phosphorus content was more than 0.024% and the tin content was more than 0.09%, and that at 20°C decreased by addition of phosphorus and tin.
  There was a proportional relationship between thermal and electrical conductivities at 20°C. Thermal conductivity of copper castings was not affected by the growth direction of crystal grain and decreased linearlly with increasing porosity.

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  Specimens were prepared from high purity pig iron by melting in Kryptol furnace and pouring into sand molds (3mmφ×70mm) kept at room temperature, 500°C and 900°C and also into step-bar sand molds (5-50mm thickness) for the examination of mass effect. The chemical composition of specimens was 3.6%C, either 2.5%Si or 3%Si, 0.02-0.21%Mn, 0.008%P, 0.005%S and 0.05-0.09%Mg.
  (1) The slower the cooling rate and the larger the Si content, the larger was the amount of ferrite. (2) There was an optimum range of Mn/S content ratio for ferritization and this optimun range moved to a smaller numerical value by Ca-Si inoculation. (3) The influence of Ca-Si inoculation on the ferritization was more remarkable than that of Fe-Si inoculation and the reaction occured more completely when Ca-Si and Mg was simultaneously added than when they were separately added. (4) When Ca-Si was added onto the surface of melt, an almosf complete ferrite matrix was obtained at Mn/S content ratio 4 (0.03%Mn) in 2.5%Si specimens poured into sand molds kept at 900°C after inoculation of 0.4%Ca (1.2%Ca-Si) and in 3%Si specimens either poured into molds kept at room temperature and 500°C after inoculation of 0.2%-0.3%Ca (0.59%-0.89%Ca-Si) or poured into molds kept at 900°C without inoculation. (5) When Ca-Si and Mg simultaneously added into melt, an almost complete ferrite matrix was obtained at Mn-S content ratio 4 (0.03%Mn) in 2.5%Si specimens poured into sand molds kept at 500°C after inoculation of 0.4%Ca (1.2%Ca-Si). (6) The change in Brinell hardness due to the change in thickness is relatively smaller in 0.29%Ca (0.86%Ca-Si) inoculated specimens than in Fe-Si inoculated specimens. An almost complete ferrite matrix (aoout 90%) was obtained in Ca-Si inoculated specimens of 50mm thickness containing 3%Si. (7) Influences of Ca-Si inoculation were explained taking into consideration the direct influence of Ca atoms on the stability of the cementite and their indirect influences arising from their strong interaction with the impurities (S, N, O) in the cast iron.

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  It is well known that the reliability concerning ductility of low alloy steel castings is poor compared to homogeneous steel because of segregation of alloying elements, microshrinkage and nonmetallic inclusions contained in steel castings. Many studies have been carried out to elucidate the cause and solve the problem of decrease in toughness of low alloy steel castings. As a result, it became clear that the toughness of low alloy steel castings was not equal to that of homogeneous steels, however much the microporosities and nonmetalic inclusions were reduced. Therefore, this study was made to find a method of improving the toughness of low alloy steel casting by eliminating carbon segregation in the segregation region, because carbon is the most improtant element that has an influence on the metallurgical properties of steels. Although carbon is segregated simultaneously in chromium, manganese and molybdenum segregation regions, it seemed that carbon segregation in steel castings could be eliminated by the addition of silicon that increase the activity of carbon in the segregation region.
  The toughness of low alloy steel castings decreased with an increase in carbon segregation under quenched and tempered conditions. The addition of silicon was effective for vanishing carbon segregation and increased the toughness of low alloy steel castings. The impact values of steel castings approached those of rolled steel, when the carbide segregation completely vanished.
  Suitable chemical composition of steel casting without carbide segregation were determined from the interaction coefficients which indicate the influence of alloying elements on carbon activity in austenite structure and the segregation ratios of alloying elements.

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