Various theories, hypotheses or ideas have hitherto been proposed on globular graphite formation in cast iron. The author classified them into the following 5 groups, and discussed concluding that all of them are untenable from points of views of crystallography, physics and science of metals.
  1) Surface Tension Theory
  2) Theory Assuming the Disappearance of Directional Differences of Growth Rates due to Supercooling
  3) Super-saturation Theory
  4) Theory Assuming Spherical Nucrei
  5) Theory Assuming that Globular Graphite is Formed in Solid Phase
    The author added also briefly his own theory proposed in the “Report of the Castings Research Laboratory,” Waseda University, Tokyo in 1950 and 1953. This theory is based on the following ideas and has fairly been proved by experiment.
    Graphite particles separating from melt adsorb magnesium vapour, which is also separating due to the decrease of solubility on austenite solidifying, and become extremely flexible and inelastic. These extremely flexible and inelastic particles of graphite, suspending and incessantly moving in the melt, are pressed equally by the force on all sides and necessarily globularize in a plastic way.

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  There are so many varieties and designs of castings. It must be recognized that the standard gating systems are not applicable to any design of casting, therefore we must make a preferable design to avoid many defects caused by gating system.
  Some attempts have been made to standardize the gating system, however there are many factors to be taken into account to decrease many defects, so that it is very difficult to fix the gating system of castings.
  Foundrymen have the proper design of their foundries even to simple castings.
  This report deals with the flow of molten metal at gates and runners so as to know the conditions of striking and splashing of metal which cause gas holes, sand inclusion and oxide film.
  Photographs inserted in this monograph have been taken instantaneously at ¹/₁₀₀₀₀ sec.

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  The quality of bonding materials mixed with the molding sand has a great influence upon the properties of the sand.
  Great many conditions are required to clays used for molding sand, but among them, the bonding power should be the greatest necessity.
  The authors have made a study on this subject in order to judge the quality of clays for molding sand, and have made an investigation on the simple judgment of clay for molding sand.
  The results obtained are as follows :
  i) The bonding power of clay-combined-sand usually increases in proportion to the increasing bonding power of clay.
  ii) The bonding power of clay minerals and clay-combined-sands increases in accordance with the increasing amount of clay substance in clay and colloidal materials contained in clay minerals. Therefore, the quality of clay for molding sand will be determined by the contents of clay and colloidal substances in clay minerals.
  iii) The contents of clay and colloidal substances in clay minerals may be measured quickly and simply by utilizing centrifugal force.

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  The effects of cooling rate and inoculation on the solidification process of Fe-C-Si alloy were studied by thermal analysis and microscopic examination, and the following results were obtained. (1) The fine graphite is formed at the first stage of the eutectic reaction when the amount of Si is rather low or the cooling rate is increased. (2) The fine graphite is displaced by laky graphite as Si percent increases or the cooling rate decreases. (3) This displacement is promoted by the inoculation of Si or Ca-Si, but the latter is more effective. (4) The eutectic temperature of flaky graphite formation is higher than that of fine one. (5) The effects of inoculation are more effective when C is low or the melt is oxidized. (6) The distribution of primary dendritic austenite becomes fine and uniform by inoculation treatment.

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  When iron and steel scrap are melted in cupola, these are carburized and changed into high carbon cast iron.
  The authors studied on these scrap-melting in cupola and the following results are obtained : (1) The materials charged in the wall sides are melted at upper level as compared with those in the furnace center, and also the melting rate at wall side is faster. (2) In the case of 50% pitch coke is used as bed coke. the melting zone is higher than that in the case of gas coke alone. (3) The melting zone at the operation becomes remarkably lower than the initial height of bed coke. In this experiment, at the wall side the height of bed coke is 200∼300 mm higher than the tuyere level and 160∼230 mm higher at the furnace center. (4) We found that the low carbon materials are carburized before melting and moreover, carbon content increases further when the melt drops down in contacting with the incandescent coke and with the molten pig iron.

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