Large castings of green sand mould involve many problems. such as Scabbing, Backling, Veining and Rat tail. To find out the cause of these defects, we investigated properties of green sand systematically from green state to the high temperature.
  In this report, we describe the relations among the properties of green sand, especially deformability, for it is most important to the high temperature properties.
 (1) As the deformation increases, the permeability increases.
 (2) As the deformation increases, the strength decreases.
 (3) Among the deformation, permeability and porosity, there is recognized a certain relation, but by adding silica flour, such relation will be eliminated.
 (4) Between the porosity and strength, there is no relation but by adding silica flour there is recognized a certain relation.
 (5) The influence on the tensile strength is produced by bentonite, the influence on the compression strength is produced by bentonite but scarcely by grain size. The grain size affects the permeability.

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  Determination of clay contents in molding sand, in general, is done by the A. F. S. method. But by this method, there is a possibility for errors that a part of clay remains in silica sands without separating from them and then micro-grains of sand mix into clay.
  Another method to determine clay contents in sand is the method by means of dye-adsorption. This is measured by the duboscq type colorimetry. Since the relation of density and measured value is expressed as a logarithmic curve, the precision of this measurement becomes worse in a wide range of density.
  This report shall be announced as to the result of determination of clay contents by means of polarographic method. The relation between density and measured value can be expressed as a linear function by this method.

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  The experiment this time is done to ascertain the relation between the strength of molds and dye-adsorption.
  a) The determination of the adsorpted dye quantity is made by means of polarographic method. This method can be applied to a considerably wide range of density since the relation of adsorpted dye quantity and measured value can be expressed as a linear curve and hence the comparison of the adsorption quantities can be made easily.
  b) Deterioration of clay is also investigated by making comparisons on the strength of molds, and the quantities of dye-adsorption; molds used for a sample were made of various kinds of tempered clay and the same sort of silica sand mixtured.
  c) The applicability of this method on the deterioration test of the foundry sands is confirmed by making the comparison stated in (b) on natural-bonded sands.

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  We have done some study on basic cupola operation with a small cupola of 300 mm inside diameter and reported about it. Following the study, we enlarged the scale of the experiment, using a cupola with 490 mm inside diameter.
    Four sorts of lining materials were applied, 1) Magnesia brick, 2) Crushed Magnesia brick, 3) Dolomite (treated by Iwaki Cement Co.) and 4) Magnesia clinker.
    Results obtained are as follows :
  1. The fluidity of slag was good enough to do moderate operation.
  2. It seems that the depth of slag in the cupola has large influence upon the degree of desulpherization.
  3. Si-loss is very large and methods of controlling Si give some difficulties.
  4. Chilling effect is less than acid iron, when carbon equivalent is low.
  5. Basic iron seems cleaner than acid iron.
  6. The problem on lining materials is most important.

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  With a view of investigating the relation between the graphitization of white iron and pouring temperature, graphitizing time of free cementite, electric resistance, total carbon content and primarily precipitated graphite, impurities, oxide inclusion and micrographic as-cast structure were studied on the series of white iron specimens which have been cast in green sand mold from the same melt with varying the pouring temperature respectively.
  Results obtained with consideration are summarized in followings :
    1) The lower the pouring temperature, the shorter the graphitizing time of white iron.
    2) Micrographic as-cast structure largely depends upon the pouring temperature. Namely, primary austenite dendritic structure being formed and grown regularily at the higher pouring temperature collapses and disappears gradually with lowering the temperature. It seems that the increasing of the surface area of the primary cementite lamina with lowering the pouring temperature is the cause of shortenning of the graphitizing time of white iron at lower pouring temperatures.
    3) No conspicuous variation of electric resistance with lowering the pouring temperature were measured.
    4) Total carbon content decreases slightly with lowering the pouring temperature. Primary precipitation of graphite, however, showed no noteworthy change.
    5) Oxide inclusion analysis in white iron has not explained the increase of the graphitizing speed with lowering the pouring temperature.

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