The experiment has been performed on the influence of the finess number (F•N) of cement bonded mold and the increase of strength in winter is discussed.
  Even if the F•N may be different, the highest strength does not change, but the permeability is greatly influenced.
  The Ramming effect does not observed in coarse sand specimen, but it appears in the specimen of finer granule sand of F•N 80.
  The larger the ramming number is, the worse is the permeability regardless of F•N.
The weight change of cement mold is the best in the sand mold used cement only and the moisture is greatly absorbed when calcium chloride is added.
  The strength of cement mold supplemented with 3∼4% blackstrap molasses is the best to be used after one hour of water mixing.
  The addition of calcium chloride gives the strongest double peaks at 0.5 and at 1.5%.
  The increase of strength by means of high temperature curing is good up to about 100°C by the addition of blackstrap molasses and calcium chloride, and the higher the curing temperature is, the more increase the strength.

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  A study using hypo-eutectic iron-carbon-silicon alloys was performed to make clear the effect of sulphur in hypo-eutectic cast irons on the formation of graphite during solidification, on the malleablization and on the eutectoid transformation. The results obtained were as follows:
  (1) With increasing content of sulphur from 0.004% up to about 0.04%, graphite in the alloys with a gray appearance is modified from D type to A type, eutectic cells are refined and the maximum temperature of graphite-austenite eutectic arrest is raised. Some of these phenomena may be resulted from increasing in the nucleation frequency and decreasing in the rate of growth of the eutectic solidification with higher sulphur content.
  (2) Sulphur in the alloys remarkably suppresses the graphite-ferrite eutectoid transformation and accelerates the pearlite transformation. Accordingly, the alloys of low sulphur content prefer the graphite-ferrite eutectoid to the pearlite transformation. An increase of sulphur content leads the occurrence of the pearlite transformation rather than the graphite-ferrite eutectoid.
  (3) Pearlite and graphite-territe eutectoid develops, respectively, at the boundary and at the centre of eutectic cells.
  (4) An increase from 0.003% up to 0.013% in sulphur content of the alloys with a white appearance lowers the rate of graphitization at both the first-stage and the second-stage graphitization and decreases the number of graphite nodules.
  (5) The change of the structure of the alloys molten under various types of slag seems to be related only to the change of sulphur content by the desulphurization with slag.

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  The affinity of the niobium to nitrogen is between the silicon and the titanium. The effects of silicon and titanium to 1st graphitization of white iron under co-existence of nitrogen were studied. Then, the influence of niobium and nitrogen to the 1st graphitization of white iron was investigated.
  The results obtained were as follows:
  (1) Niobium, which is contained to a certain extent in whihe iron, decreases acid-soluble nitrogen and 1st graphitizing period. But, it does neither over this limit.
  (2) The niobium-containing iron has lower correlation between acidsoluble nitrogen and 1st graphitizing period than niobium-less iron. And its acid-soluble nitrogen disturbs 1 st graphitizaion less than the other.
  (3) Number of graphite nodules increases with niobium and decreases with nitrogen content.
  (4) The niobium compound formed in iron is δ-Nb (C, N), and it is observed as reddish quadrangular small precipitate in microstructure.
  (5) From above results, the influence of niobium to 1st graphitizing period may result partially from the decrease of soluble nitrogen, but niobium is not so effective as titanium.

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  Effects of the varous kinds of coating materials, the coating thickness and the preheating temperature of mold on cooling rate, microstructure and hardness of permanent mold cast iron have been studied, using two kinds of cast iron mold which respectively had the thikness of 20mm and 40mm. The molds were coated with soot, diatomaceous earth, silica sand or fire clay, and a gray iron containing C 3.30%, Si 2.20%, Mn 0.50%, P 0.15% and S 0.08% was poured at about 1400°C. The preheatig temperature of mold before pouring was given at 150°C, 250°C and 350°C, and the coating was given the thickness of 0.1mm, 0.2 and 0.3mm.
  The results obtained are as follows:
  (1) The heat insulating power of coating materials is taken in order as follows: 1) soot, 2) diatomaceous earth, 3) silica sand, 4) fire clay.
  (2) The thickness of coating affects remarkably cooling rate, microstructure and hardness at the surface zone of castings. The thicker the mold is, the more remarkable the effects of coating thickness are. However, in thin mold, and especially at higher temperature, the effects of coating thickness are not so large as in thick mold.
  (3) When the thickness of coating is equal, in thick mold, the appreciable effects of the variation in preheating temperature on cooling rate and microstructure at the surface zone of castings can not be observed. But in thin mold, especially with thinner coating, cooling rate of castings decreases with the increase in preheating temperature, and correspondingly changes in microstructure at the surface zone are observed.
  (4) The wall thickness of mold also considerably affects cooling rate and microstrucure of castings.
  (5) For the iron with above-mentioned analysis, the microstructure at surface zone of castings is composed of ferrite and eutetic graphite at the mean cooling rate of about 230 to 300°C/mn, pearlite, ferrite and very fine graphite at about 180 to 220°C/mn, and pearlite and randomly dispersed fine flake graphite below about 180°C/mn.
  (6) From the above-mentioned fact, it may be said that it is not necessarily required to anneal the casting to soften.
  (7) In the “as cast” condition, the hardest and yet free machinable structure may be obtained by an iron that has a pearlitic matrix containing a randomly disperced fine flake graphite, and in the annealed condition, the hardest structure is a mixed one of ferrite and eutectic graphite.

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  The studies reported here are divided into the following two parts: First, the effect of carbon, silicon, and manganese on hydrogen absorption by molten cast iron at contact with steam; second, the effect of carbon and silicon on hydrogen evolution from cast iron when it solidifies.
  Cast iron was melted in a Tammann furnace; then steam was blown over the surface of the melt. The samples for hydrogen determination were taken from the melt by a quenching technique before or during the steam blowing. For the study on hydrogen evolution during solidification "vacuum sampler" was used. The evolved hydrogen was determined by gas chromatography or the palladium tube technique, and the hydrogen in solid iron samples was determined by vacuum fusion palladium tube method. The results obtained are as followings.
  1) The rate of hydrogen absorption and the maximum hydrogen contents of the melts are reduced by increasing carbon and silicon contents. Manganese of abouf 4% increases the rate of hydorogen absorption.
  2) Fe-C alloy melts (C 4%) absorb hydrogen rather rapidly and the maximum hydrogen contents are about 90% of the calculated values.
  3) Fe-Si alloy melts (Si 14%) absorb little hydrogen. The oxide films on the melts seem to obstruct the contact of steam with melts.
  4) During the solidification of hypoeutectic melts more hydrogen is evolved than retained. During that of hypereutectics, on the contrary, more hydrogen is retained than evolved. Methane is found in the evolved gas from hypereutectic iron.

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