Flaky graphite cast iron prepared from Swedish pig iron and magnesium-treated spheroidal graphite cast iron prepared from high purity pig iron were both melted in a Kryptol furnace and pouring into sand molds kept at 500°C and room temperature. The chemical composition of the specimens was about 4%C, 1.8%Si, 0.5%Mn (Mn/S ratio 50-70), 0.02%P, 0.006-0.010%S in flaky graphite cast iron and about 3.6%C, 2.5% or 3%Si, 0.02-0.51%Mn (Mn/S ratio 4-101), 0.004-0.006%S, 0.033-0.105%Mg in spheroidal graphite cast iron.
  In flaky graphite cast iron, the addition of 3%CeF₄, LaF₃, ThF₄ increased the amount of ferritic matrix and which became more remarkable by the addition of LaF₃ and ThF₄ combined (1 : 2). In the spheroidal graphite cast iron, the addition of 3%CeF₄ increased the amout of ferrite in specimcns containing 2.5%Si (Mn/S ratio 7.3 and 15.5) and 3%Si (Mn/S ratio 5.6 and 12.7), and the smaller the Mn/S ratio, the larger was the amount of ferrite. The addition of 3% LaF₃ increased the amount of ferrite at the Mn/S ratio of about 11 in specimens containing 2.5% and 3%Si and the morphology of graphite changed from spheroid- to crab-shape. The addition of 3% CaF₂ increased the amount of ferrite considerably in specimens containing 2.5%Si (Mn/S ratio 17), but the addition of 3%NaF increased the amount of ferrite slightly in specimens containing 2.5% Si(Mn/S ratio 14.4). The addition of 3%ThF₄ either promoted or retarded the ferritization of marix depending upon the Mn/S ratio. The additton of these fluorides were effective for ferritization in the order of CeF₄>CaF₂>LaF₃>NaF>ThF₄ under present condititons depending upon the Mn/S ratio and the method of addifton.
  Metallic Ce was a powerful graphitizer and almost all matrixes were ferritized in 0.1% or 0.3%Ce treated specimens, and especially in 0.1%Ce treated specimens undercooled graphite intermixed with a large amount of massive graphite and flaky graphite intermixed with a small amount of star-like graphite were often observed. The influence of Ce, Ca, La, Na and Th were explained by taking into consideration the direct influence of these elements on the stability of the cementite based upon the nature of the chemical bonding in cementite and their indirect influence arising from the strong interaction which they have with the impurities (S, N, O) in the cast irons. It was pointed out that the various influences seemed to appear depending upon the Mn/S ratio and method of addition.

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  The liquid nitriding process (Tufftride process) was used to improve wear, seizure and pitting resistances in white cast iron. Fe₃C and silicon dissolved in α-iron have important effects on nitriding. In this basic study of liquid nitriding of white cast iron, white cast iron containing 3%C and 1∼3%Si was nitrided by the Tufftride process at 570°C for 4 hrs.
  The compound and diffusion zones were obtained by nitriding. The compound zone consisted of ε(Fe_2-3N base) carbonitride and Si₃N₄. Carbon contained in white cast iron in form of Fe₃C has been dissolved in ε phase by the nitriding. The presence of Si₃N₄ in samples was confirmed by increase of acid insoluble nitrogen. The value of maximum hardness in compound zone of each sample greatly increased owing to the great amount of carbon dissolved in the ε phase. As the silicon content increase, the depth of the diffusion zone became shallow by the reduction of diffusion velocity, but that of the compound zone did not change.

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  It has long been recognized that the inner surface of almost globular blow hole in steel castings were generally smooth and yet the details on their shape and condition have been not studied. This study was introduced to clarify the actual condition of blow holes and obtain more information concerning the formation of blow holes by scanning electron microscopic observation and electron X-ray microanalysis.
  The inner surface of blow holes made by gas looks smooth and almost globular, but is not necessarily perfectly smooth. Especially, the characteristics of oxidized blow holes are very different from the blow holes produced by reducing atmosphere or gas. The blow holes produced by H₂, N₂ and CO gases have different inner surfaces, respectively. On the inner surfaces of blow holes, oxides of various shapes and sizes are found, and it was cleared that these oxides are mainly SiO₂ or SiO₂-MnO-Al₂O₃ compound oxides.

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  The structure of unidirectionally solidified aluminum and its alloys was studied in order to clarify the effect of artificial convection flow caused by Lorentz-interaction between a magnetic field and a direct current.
  Artificial convection flow creates a wide equiaxed zone and considerable grain refinement, and it is suggested that the grain refining effect is caused by dendrite arm segmentation and accumulation. Some definite convection flow places the columnar crystals at an angle, regardless of the solute concentration. Inverse segregation is inhibited by the presence of artificial convection flow, and it is thought that because of this the solute in front of the tips of growing dendrites is transported away into the melt. With the artificial convection flow, the secondary dendrite arm spacing is found to be exponentially inversely proportional to average cooling rate, and arm spacing tends to spread compared to stationary solidification. In stationary solidification, the Al-CuAl₂ eutectic develops a lamellar structure, however, in artificial convection flow, it changes to divorced eutectic and degenerated structures.

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  The viscosity change in solidifying Sn-Pb and Al-Si alloys was investigated using a torsional transduccr forced to oscillate at a resonance frequency. Since the amplitude of vibration was only 1μ and the skin depth was less than a few millimeter in this viscometer, it has only a very small stirring effect on the melt. Therefore, the features of solidification of melts were reflected well in the results of viscosity measurements with this apparatus.
  There was a rapid increase in viscosity at the beginning of solidification in the supercooled melt. In the eutectic alloy, the beginning of viscosity increase at the eutectic temperature was delayed, but once the change began the viscosity increased sharply. Viscosity increase was more rapid in alloys with wide freezing range than in those with narrow freezing range. Viscosity increase was more rapid in alloys which primary phases crystallize dendritically than in alloys which those crystallizes planarly. Viscosity increase was more rapid in alloys which crystallize many small primary solids than in alloys which crystallize only a few large solids.

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  This investigation was made in order to obtain the data on strength and moisture content of moisture condensed layer in green sand mold. Tensile tests were performed in the range of room temperature to 100°C to study the influences of bentonite and moisture content, type of bentonite, additives and ramming density of synthetic sand specimens.
  The tensile strength of moisture condensed layer changed as moisture content in the specimen gradually increased according to the rise of temperature at the point of measurement, and it varied with (moisture weight)/(bentonite weight) value. The tensile strength of the layer was great when bentonite with a high value of liquid limit, plastic limit and swelling was used. The moisture content of the layer increased rapidly in the range of 60°C to 70°C, and saturated moisture content at 100°C incresed about 2% more than the initial moisture content. It became clear that bentonite slurry changed its characteristics with temperature and influenced the strength of the moisture condensed layer.

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