In tin bronze castings, gross shrinkage defects are hard to occur, so far as melting is carried out carefully, hence it has often been misunderstood that there is little trouble in producing sound tin bronze castings. This seems to be due to the fact that the shrinkage cavities of bronze castings are often so microscopically fine and dispersed that the porosities may not be detectable. The purpose of this research is to clear up the mode of shrinkage defects and to investigate the effect of risers and end portion on the soundness of tin bronze castings. The specimens of tin bronze castings were made under various casting conditions, and X-ray inspection of porosities were carried out on comparatively thin slices which were cut off from each specimen. Porosities revealed in castings subjected to radiographic inspection and effects of riser and cooling action of the end portion of castings on the soundness of tin bronze castings were also investigated. Some physical properties of castings were also measured in relation to the defects. Furthermore, a similar experiment was carried out on brass and aluminum bronze castings for a comparison with tin bronze castings.
  Results obtained are as follows. In tin bronze, feeding of metal during solidification is essentially difficult because of its wide freezing temperature range, and the occurrence of fine shrinkage porosities is inevitable. Shrinkage defects are varied by the mode of crystalline growth, and the growth of equiaxials is accompanied with dispersed microporosities, while columnar crystals cause centerline shrinkage cavities. In either case, riser has little effect upon the soundness of castings except the initial stage of solidification so far as shrinkage cavities are concerned. In columnar crystal structure castings, shrinkage cavities are concentrated to the centerline portion, and the sound end zone produced is longer than the case of equiaxial one. The sound end zone is about 4D mm long in plate castings and 10√D mm in bar castings, so far as crystals grow in columns. And the length of zone is affected by the pouring procedures. Horizontal pouring is more effective than vertical. If pouring is made vertically, top gating is more desirable than bottom gating, and pouring should be done slowly. And also, gases dissolved in tin bronze have detrimental effects upon the soundness of castings. As to casting defects, brass and aluminium bronze show different behavior from tin bronze, and feeding of metal can be made so effectively that riser effect is obvious and the occurrence of shrinkage defects in these alloys resembles to that of steel castings.

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  This is the second progress report on the study of melt quality of 85-5-5-5 red brass, and includes the investigation of the conditions for gas absorption by the steam reaction, and the behaviour of dissolved gas by means of fracture observation, radiography, fluorescent penetrant inspection of the chill-blocks, and porosity measurement.
  In an usual furnace atmosphere, contact of water vapour with the metal results in little gas absorption. But, if the melt is contaminated with an excess amount of de oxidant such as phosphor-copper, heavy gas absorption is caused from bubbling or exposing water vapour into the super-suturated state. Attention is also directed to the behaviour of dissolved gas in the melt.
  Amounts of dissolved gas in the melts or porosities have a certain relation to the fracture characteristics of chill-blocks. The typical features of the fractures which are dependent on the dissolved gas include depth of blue-grey region, depth of columnar patern, fracture texture, and bulk of oxide inclusion formed on the fractures. These features may be reproducible with certain reliability.

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  he effects of O₂, N₂ and A on vacuum-melted cast inon and on hyper eutectoid carbon steel were investigated. 6 kinds of specimens of cast iron and steel with different % of C were vacuum-melted. The sample was cast after it had been held in O₂, N₂ or A gas with the pressure of 760mm Hg for 20 minutes. Then % of C, % of Si, microstructure and tensile strength were compared with those of vacuum-melted specimens having the same % of C respectively. The results obtained are summarized as follows.
  The effects of O₂ :
  1) Decrease of % C is remarkable; the higher the melting temperature, the greater the decrease. Changes in % of Si were scarcely observed. 2) Structure of eutectic graphite in vacuum-melted cast iron, was the same as that of the cast iron melted under O₂ atmosphere. But in the latter case, free cementite and pearlite appeared. In hyper eutectoid steel range, free cementite was added to the initial massive graphite+pearlite structure by melting in O₂ atmosphere. 3) The values of tensile strength scattered greatly corresponding to the structural change in cast iron range, reaching to 50kg/mm² in some case, while, in hyper eutectoid steels range, tensile strength always decreased greatly.
  The effects. of N₂:
  Experiments were performed for 4 kinds of specimens whose % of C and % of Si are in the range of cast iron. 1) % of C, % of Si did not change. 2) Microstrucre change was not observed. 3) Tensile strength did not change.
  The effects of A:
  1) % of C, % of Si did not change. 2) Microstructure change was not observed. 3) Tensile strength did not change.

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  Little work has been done on the effects of titanium on the properties of calcium S-G iron. In the previous informations on magnesium S-G iron, it was suggested that titanium in calcium S-G iron may have an anti-spherodizing effect of graphite. The present work has been carried out to determine the effects of titanium on the properties of calcium S-G iron and also the effects produced when misch-metal is used with calcium to counteract the anti-spherodizing effect of titanium.
  Followings are the summary of the results obtained;
  (1) Titanium restricts spherodization of graphite in calcium S-G iron, but is not so powerful as in the case of magnesium S-G iron.
  (2) The combined use of a small quantity of misch-metal with calcium effectively counteracts the antispherodizing effect of calcium.

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  In our previous reports, we have investigated the appearances, causes and differences of the scabs in natural and synthetic sand mold.
  In the present report, our aim is to show the results of our investigation and research on the types of scabs which appeared in semi-synthetic sand mold. The method we employed in each test is the same as that in the previous investigation.
  The conclusions from our tests are as fallows:
  1) The properties of high temperatur and the scabs of several kinds of semi-synthetic sand molds which have foundamental combination are shown in the following table.
  [Written in non-displayable characters.]
  N. Sand : Natural Foundry Sand
  S. Sand : Silica Sand
  Syn. Sand : Synthetic Foundry Sand
  Bent: Bentonite
  F. Clay : Fire Clay
  “Medium” show that its property is situated between those of N. Sand and Syn. Sand.
  2) The oppearances of the scabbing deffects produced in the semi-synthetic sand mold closely resemble that produced by the compressive strength, as high temperature and generally the higher the compressive strength, the greater the scabbing defects.

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  In most cases, when the green or dry sand specimen is exposed to the high temperature (700°, 900° and 1150°C), the natural molding sand begins to decrease in strength at the beginning of the exposure, but afterwards recovers from this decrease.
  However, the sythetic molding sand specimen consisting of silica sand and bentonite does not decrease the strength even at the beginning of the exposure.
  In some cases, the natural molding sand is prevented from the decrease of strength by adding the bentonite or mulling the sand.

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