This study was performed to investigate the effects of coke size on operating conditions of cupola and on properties of castings. The cupola used has an internal diameter of 520mm, effective height of 2310mm, tuyére ratio of 5, and no forehearth. Coke size for the experiment were selected as follows :
  a) large size, 100∼120mm, 1/5∼1/4 of internal diameter,
  b) medium size, 60∼80mm, 1/9∼1/6 of. internal diameter,
  c) small size, 30∼50mm, 1/17∼1/10 of internal diameter,
  d) mixed size, mixture of a) and c) with equal amount.
    Other operating factors were kept constant as follows :
  Blast volume : 21m³/min (100m³/m²-min)
  Height of coke bed : 1100mm
  Quality of coke : 7% ash
  Coke ratio : 15%
  Charged metal : 40% of pig iron, 30% of return iron scrap, 30% of steel scrap, and some amount of ferro-silicon and ferro-manganese. Size of each raw metal was arranged uniformly.
    The results obtained are as follows :
  (1) On the operating conditions : As coke size got smaller, the amount of carbon dioxide in effluent gas from cupola decreased, tapping temperature dropped, and coke bed lowered remarkably. The mean value of tapping temperature of each operation was as follows :
  Large size coke : 1500°C. Medium size coke : 1490°C. Small size coke : 1350°C.
  Mixed size coke : 1470°C.
    In the operation using medium size coke, the fluctuation of operating conditions was the least.
  (2) On the properties of castings : When medium size coke was used, the best result was obtained ; sound castings with the highest strength were taken from the iron in this operation. Moreover, the fluctuation of measured values throughout operation was the least. The result of the second class was obtained by using small size coke. In this case, shrinkage cavities were not occured, but defects such as pin holes and short cut rarely appeared due to the lower tapping temperature. In the case of using large size coke, both shrinkage cavities and blow holes were formed in spite of the highest tapping temperature. On the properties of these castings, consequently, the result obtained was the worst. The mixed size coke had also bad influences upon the properties of castings.
    As contrasted these results with the amount of carbon dioxide in effluent gas, it was recognized that the soundness of castings was related closely with the oxidizability of furnace atmosphere.

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    The thermal behaviour of mould coating in iron casting were investigated by means of differential thermal analysis. Graphite and silica coatings, the most common materials, were examined firstly, then alumina, metallic silicon, aluminium, mica and others were tried.
    The following results were obtained by our experiments.
  (1) Graphite coating has the remarkable insulating effect by itself with the promotion of insulating gas film.
  (2) Silica powder has also the reliable effect and fused layer at casting surface is easily stripp for finer grains.
  (3) Silicon coating has the same insulating effect and make casting surface smooth by changing to silica or some other suitable slags.
  (4) Aluminium powder is less reliable coating but it might give good surface when proper amount is applied.
  (5) Mica powder is also less reliable coating. When it is applied to penetrative sand mould, however, it gives good casting surface and makes easy to remove surface slag.

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  With the purpose to find out the suitable sodium silicate binders for CO₂ Process, the authors mixed water-soluble starch, dextrine, corn binder and silica sol to water glasses respectively, and studied the physical properties of the mold bonded with such specially prepared water glasses. From the view points of reactivity of binders with CO₂ gas, the strength, the easiness of mulling and stripping, about 1 per cent addition of organic binders such as water-soluble starch, dextrine and corn binder is preferable. For the addition of silica sol, about 5 per cent is recommended.

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  In report 1, 2, 3 and 4, the authors have already described the results obtained on the segregation in cast iron and copper alloy castings.
    Succeeding to previous reports, an experiment on the segregation in aluminium alloy castings was made by the similar methods to the experiments in cases of copper alloy castings.
    The experiment was made on three different systems of aluminium alloys such as Al-Cu, Al-Mg and Al-Si.
    Four kinds of samples were prepared on each aluminium alloy, viz., the samples cast into watercooled metal molds, the samples cast into alumina molds, the samples solidified in the slowly cooled furnace and the grain refined samples treated with KBF₄.
    The determination of segregation on the traverse section of cylindrical samples was made by the similar method to the previous experiment, i.e., the local spectrographic analysis with the C.R.L. universal source unit.
    The gists of the results are as follows :
  (1) In the rapid cooled castings, inverse segregation appeared at the outer and inner layers, besides normal segregation in the intermediate layer, i. e., two stages of inverse segregation were indicated. In the slowly cooled castings, however, the inverse segregation at the outer layer did not appear and the normal to inverse segregation appeared at the outer to inner layer.
    These features of ingot segregation were similar to that appeared in copper alloy castings.
  (2) In the cases of samples which was solidified in the furnace and cooled more slowly than samples cast into alumina molds, both the degree of inverse segregation at the inner layer and the degree of normal segregation at the outer layer has decreased.
    It is noticiable that such slower cooling did not cause the normal segregation at the outer layer to a higher degree.
  (3) Grain refining treatment resulted generally in a lower degree on the local and ingot segregation.
  (4) It is clarified, furthermore, that the local spectrographic analysis method established by the authors was suited well for the determination of segregation in aluminium alloy castings.
    This paper presents details mentioned above.

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