The use of oxygen in the manufacture of cast iron has not been particularly put into practice. However, an investigation into utilization of oxygen to improve cast iron has been conducted for several years in the authors' company's laboratory.
  The treatment of lancing oxygen into molten iron decreased contents of carbon, silicon, manganese and other harmful elements for the formation of nodular graphite, such as titanium, and did not have the harmful influence of oxidation on the iron. Therefore, the above treatment could be adopted for the improvement of pig iron for ductile iron and the manufacture of various cast irons. For instance, even pig iron, having some quantities of elements such as titanium which disturbed the formation of nodular graphite brought about by magnesium addition, easily formed spheroidic graphite by magnesium addition after the oxygen lancing treatment. Cast irons treated by injection of oxygen showed superior properties in the uniformity of graphite distribution, the tensile strength and the influence of mass effects.
  For the purpose of oxygen treatment of cast iron the foundry converter has been used, by which various cast irons have been made from cupola irons. The converter is especially suitable for the manufacture of chilled castings which have comparatively low silicon content. The manufacture of cast irons by the converter is easier and more economical, compared with the process of electric arc furnace and reverberator, because the refining time is shorter.

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  The chemical compositions of the ordinary malleable cast iron have a restriction to obtain white iron as cast. It is generally demanded that the sum of carbon and silicon must be within 3.8 to 4.0 per cent and the ratio of manganese to sulfur is more than 1.7. Investigations were done particularly on the ratio of manganese to sulfur, and the results obtained were as follows ;
  1) By decreasing the manganese cantent, formation of white cast iron was promoted without increasing the sulfur content.
  2) In this case, by an unbalanced ratio of manganese to sulfur, the mottled fracture hardly appeared even in the specimens of more silicon content, and the increase of silicon content cancelled the ratardation of graphitization caused by excess sulfur.
  3) In comparison with an ordinary malleable cast iron of the same thickness, the graphitization could be promoted by high silicon content.
  4) Higher strength can be expected by the silico-ferrite of high silicon content in this malleable iron.
  5) It is supposed that, in the range of such silicon contents, white iron could be obtained even in thicker castings, but the graphitization would be more difficult by an unbalanced ratio of manganese to sulfur.
  6) Melting in reducing atmosphere is more preferable for manufacturing this special malleable iron.

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  Many works have been done on the carburizing or decarburizing phenomena in the cupola operation. But still many problems are remained unsolved to get complete quality control of cast iron in the operation. In this report, for a part of the methods of quality control, the carburizing abilities of various carburizing agents are studied and discussed. In order to clarify the quality of the carburizing agents, the problems on ash viscosities in high temperature and kinds of carburizing agents are studied in the first step. As the results of this investigation, following equations were obtained for and viscosities and various kinds of carburizing agents.
              C = αlogS+β
  Where C = Carbon pick up (%)
              S = Na₂O/SiO₂+Al₂O₃
          α, β = Constants given by carburizing agents
              C = alogT+b
  Where C = carbon pick up (%)
              T = reaction time (mn)
          a, b = constants given by carburizing agents

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  The hardening reaction of the exothermic and selfhardening mold by sodiumsilicate and silicon was studied. The reaction is presumed as follows.
            Na₂O, nSiO₂+H₂O⇄2NaOH+nSiO₂
            mSi+2NaOH+(2m－1)H₂O=Na₂O, mSiO₂+2mH₂
  This assumption was ascertained by normal gas unalysis and mass spectro analysis and by the measurements of pH and viscosity of the reaction system. Then, X-ray diffraction photographies of the products of the reaction were examined.

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  The author has previonsly reported on the pin holes of steel casting caused by the moulds and offered the more reliable method for quantitative estimation of pin holes.
  Now, the author studied experimentally on the relations between the drying depth of the mould and the thickness of the steel castings, on which Dr. Chijiiwa had reported theoretically on some assumptions.
  The effects of the sectional size of in-gate, the weight and size of riser on the “Pin hole intensity” have also been investigated.
  The results obtained were as follows ;
  (1) As a conclusion of this investgation, the difference between the theoretical and the experimental results was due to the ignorance of the gas pressure of the melt on solidification in theoretical calculation.
  (2) In the specimens of the same thickness, the more the sectional area of in-gate and riser increased, the less became the pin hole intensity.
  With a constant sectional area of riser, the more the riser weight increased, the more was the pin hole intensity.

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