The solidification process of Fe-C-P alloy was investigated by thermal analysis and microscopic observation, some applying quenching method. For the specimens more than 1% phosphorus, it was observed that plate-like Fe₃C solidified with less graphite flakes at binary eutectic reaction. The formation of the plate-like Fe₃C was discussed on the structures of mottled iron, i.e. in the alloy, the binary eutectic reaction of γ-Fe₃C proceeded owing to a wide range of reaction temperature, so that ledeburite-austenite would deposit on the precedingly formed austenite ; primary or eutectic with Sasanoha-structure.

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    As a substitute of binders for shell molding, the utilization of powdered natural resins and urea resins has been studied in the previous report (Report 2). There was, however, a difficulty to pulverize them to very fine particles on account of low melting point of these resins. In addition to this, there were some trouble in mixing them homogeneusly with powdered P-F (Phenol-Formaldehyde) resins.
    To eliminate these faults, the pre-coating of sand with rosin or its derivatives has been studied this time. The rough grains of rosin or its derivatives are mixed with sands at first and the mixture is heated up to the melting point of these resins. After cooling, they are graded to a fine particles. As the results of these means, sand grains are easily coated by the film of resin, then they are blended with small amount of powdered P-F resins (2∼4%), and the mixture thus obtained may be applied to shell molding process.
    The experimental results taken are as follows.
  1) The best condition of coating, in the case of rosin, was obtained by heating them to 100°C with sand grains for about 30 min. The higher the temperature, the lower the strength of the mold made of this material. The application of alcoholic solution of rosin to coating materials was by no means yielded better results.
  2) Using rosin coated sands in place of powdered rosin, the strength of the mold made of rosin and P-F resin mixtures (1 : 1) was improved about 10%.
  3) In order to convert the polar characteristics of rosin, the derivatives of rosin, such as ester-gum, rosin maleic acid and rosin-pentaerythritol condensates were used for coating. The strength of the mold cured by the mixture of one of these derivatives and powdered P-F resin (1 : 1) was inferior than the second result.
  4) To the rosin coated sand, either powdered CaO or ZnO was added as a hardening agent. Curing was completed in about 4 min. in the former case and 8 min. in the latter. The strength of the mold was, however, not yet satisfactory for shell molding.

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  For the production of large castings, the reverberatory furnace, cupola or crucible furnace are commonly used, but the direct arc furnace has not yet been employed. The authors have succeeded in the melting of Mn-bronze and Sn-bronze using a direct arc furnace (2 or 10 ton capacity). In this case, the charge included 40% of heads and runners and 10% of turning scrap are used, the melting loss was 8∼9% and this was rather more than the case of crucible or indirect arc furnace. In melting Sn-bronze a complete deoxidation was done by adding 700 g of 15% P-Cu per 100 kg of metals. A great success was obtained by using graphite and chamotte powder mixtures instead of silica sand or magnesia as the furnace lining. Glass was used as a cover of the metal to prevent the oxidation on the melt surface. Fluidity of slag was controlled by the addition of borax and soda ash.

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