Magnesium becomes supersaturated and separates as vapour on solidification of cast iron out, which vapour is adsorbed by separating graphite particles. These graphite particles become very deformable on adsorbing Mg vapour and spherulitize. This is the theory proposed by the author. In the previous paper, the formations of various types of graphite，namely, flake graphite, lump graphite etc., were discussed, and sufficient pages were not given for the discussion on the formation of globular graphite. Besides, the theory was not proved by author's own experiment.
  The present paper contains an experimental evidence on Mg adsorption by graphite particles. If Mg-treated molten iron is inoculated by charcoal or graphite powder, the inoculant will adsorb the separating Mg vapour, so that the separating graphite particles will be unable to adsorb sufficient Mg vapour to spherulitize and they will remain flaky. This inference was experimentally proved in the present paper.
  The surface tension of solids was next discussed. If the surface tension of a liquid is smaller than that of a solid, the liquid will wet the solid and a liquid will not wet a solid when its surfacee tension is larger than that of the solid, The experiment of Wulff, Taylor & Buttner was explained by this idea. When nodular iron is melted in a graphite crucible, the wall of the crucible will adsorb the separated Mg vapour and decrease its own surface tension, accordingly, the surface tension of the molten iron will become relatively larger than that of the crucible, therefore, the molten nodular iron will not wet the crucible.
  The author's theory on globular graphite formation is as following :
  The facts that the suspending particles do not dissolve in the liquid and that the particles are easily deformable are the two fundamental causes of spherulitization phenomenon. Magnesium becomes supersaturated and evolves as vapour on solidification of aus eni e. The separating graphite particles adsorb the vapour and becomes very deformable. The easily deformable (plastical) graphite particles are pressed on all sides and spherulitize by he similar mechanism as a “butter ball” formation. Butter does not spherulitize by its own surface tension, but it spherulitizes when pressed on all sides by knives or fingers.

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  In this study, the reactivity was discussed when a pure magnesium block and magnesium alloys were added to molten cast iron. Moreover the new adding method was studied in use of the special phosphorizer and the tablet in which the mixing powder of magnesium and silicon was binded by meta-acrylic-resin. By this method the elevation of the magnesium recovery per cent and the decrease of violent reaction were obtained.
  Another adding tablets that consisted of magnesium powder and magnesia, calcium carbid or calsium silicide powder respectively in place of silicon powder were studied.

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  The authors measured the O₂, N₂ and H₂ contents in cast iron by means of the vacuum fusion gas analysis equipment to determine how much these gas contents were influenced by melting conditions.
    Several tests were also performed on molten metals from a cupola or an electric furnace with the following conclusions:—
  1. Up to 1450°C under the condition of crucible - melting in the laboratory, rise of the melting temperature is attended with an increase of O₂, N₂ contents : further rise over 1500°C, on the contrary, will result in a decrease of both elements.
  2. In the cupola or electric furnace, high temperature operation over 1500°C will also reduce the amounts of O₂, and N₂.
    In comparison with crucible melting in the laboratory, the H₂ content is very large.
  3. Relationship among the microstructure, graphitization degree, hardness of castings and analysis value of O₂ is to be still further studied for clarification.
  4. Characteristics of low-temperature and high-temperature melting were investigated with regard to deoxidation of molten cast iron.
    As a result it is pointed out that in low-temperature operation, effects of rusted charging materials and oxidized layers growing before the melt-down are hard to eliminate, but in high temperature working, the O₂ content approaches the deoxidation equilibrium value and at the same time molten metals tend to be very liable to absorb H₂.

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  Molten cast iron of about 1330°C was poured into the green sand mold having the cavity of the finite dimension δcm 0.4∼1.42. From the thermal analysis of the center of the casting, various experimental equations on various transformations, δcm, the time and temperature were obtained. Thereby the conventional accumulating diagrams in foundry were made.
    {δcm = Volume/Surface Area (cm)}

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  Defects such as Scabbing, Buckling, Veining and Rat Tail are all chiefly caused by cracking of sand moulds on the pouring.
    The cracking of sand moulds are effected by the following properties of sand moulds on the pouring.
    1. Thermal expansion and contraction       2. Toughness.
    3. Back Pressure       4. Heat Transition
  So, in this report, we tried to clear the factors that effected the thermal expansion and contraction, and compared it with high temperature crack test's results.
  And results obtained are as follows :—
    1. When high temperature expansion increases, high temperature contraction decreases and increases high temperature crack of sand moulds.
    2. High temperature expansion and crack increase in the following cases :—
      i. Decreasing grain size of sands.       ii. Hard ramming.
      iii. Silica flour addition.       iv. Increasing binder used.
      v. Increasing deformation of the compression test.

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  The research on the mold or core gas pressure has been systematically performed as seen in many literatures. This paper is prepared to report the measurement of gradual variations of the core gas pressures in the case of cylindrical mold cavity of 3"φ × 2"φ × 4" into which molten cast iron was poured.
  (1) The core gas pressure shows an instantaneous high peak having a value of 200 to 300mm Aq as molten metal is poured. After 30∼40 seconds, the second peak appears again and then its pressure gradually decreases.
  (2) The time these two peaks appear is not affected by the core mixtures and the treatment of cores. The value of the gas pressure is, however, decided by the later.
  (3) Venting holes arranged in cores tend to decrease the core gas pressures and to make these two peaks vanish or to make these variations gradual. (T. Okakura)

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