鋳物

研究論文

金型鋳造用塗型の気孔率と熱伝導率との関係について

近藤靖彦, 磯谷三男, 島田健三

1970 年 42 巻 12 号 p. 973-982
発行日: 1970/12/25
公開日: 2012/10/01

DOIhttps://doi.org/10.11279/imono.42.12_973

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  In this paper there will be no report concerning the relation between experimental values and theoritical values, though some theoretical considerations have been made in the past about thermal conductivity of coatings for metal mold casting. This is caused by the fact that it is comparatively difficult to quantitatively measure the intricate coating layers. In this report, the thermal conductivity of the system silica flour-diatomaceous earth coatings were obtained from the thermal resistance measurements which have already been discussed in the previous paper and the relation between porosity and thermal conductivity of coatings were considered. It was also discussed that porosity of coatings influences durability. Durability was measured from the decreasing rate of coatings by the repeated metal mold castings. The results obtained were as follows.
  (1) Porosity of coatings was maximum when using only diatomaceous earth as the basic material, and the decrease of porosity becomes smaller with addition of silica flour. About the binders, phosphate proved to have more porosity and smaller pore size than silicate. And dilution of the binder increased the porosity of coatings.
  (2) Relations between porosity and thermal conductivity were clarified. In case of coatings with porosity over 70% (with over 50% diatomaceous earth), thermal conductivity decreased rapidly. This was also proven from the results of casting tests. The relation between porosity and thermal conductivity can be surmised from Russell’s equation, and more over the relation between volume fractions of the binary system basic materials and thermal conductivity can also be surmised from Kingery’s equation.
  (3) Acid treatment on metal mold surface improved the adhesiveness of coating for metal mold. Durability of coating increased by adding 30% diatomaceous earth in silica flour.

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鋳鉄に及ぼす酸素，硫黄，微量元素の影響

本間正雄, 福岡清人

1970 年 42 巻 12 号 p. 983-990
発行日: 1970/12/25
公開日: 2012/10/01

DOIhttps://doi.org/10.11279/imono.42.12_983

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Various properties of cast irons are dependent upon oxygen, sulfur and minute elements contained in them. The influence of oxygen, sulfur and minute elements on graphitizing tendency of cast irons were shown quantitatively on a structural diagram. From the diagram the influence of these elements on various propertiese of cast iron can be presumed.

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CO₂鋳型表面の晶出現象とその対策

中野俊雄, 西村仁, 中田享美

1970 年 42 巻 12 号 p. 990-998
発行日: 1970/12/25
公開日: 2012/10/01

DOIhttps://doi.org/10.11279/imono.42.12_990

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    When the CO₂ sand molds are put out in the air, sometimes the carbonate crystal grows on their surface. This tendency becomes promoted in the low temperature and high humidity air.
    The influence of water content in the sand, CO₂ gassing time and mole ratio of water glass added to the sand in crystallization are studied. Furthermore, the procedure of suppressing this surface crystallization is studied.
    The results obtained are summarized as follows :
  (1) The more the water content in the sand and/or the CO₂ gassing time are increased, the more promoting tendency of surface crystallization becomes.
  (2) Increasing the mole ratio of water glass, the crystallization becomes decreased.
  (3) As crystal grows more, the compression strength and the surface stability of the CO₂ mold go down.
  (4) The addition of alkylene oxide, such as ethylene oxide or propylene oxide up to 1% of the sand, suppresses the crystallization and the compression strength and the surface stability of the mold are improved.

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初析セメンタイトの析出に関する研究

大城桂作, 松田公扶

1970 年 42 巻 12 号 p. 999-1005
発行日: 1970/12/25
公開日: 2012/10/01

DOIhttps://doi.org/10.11279/imono.42.12_999

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  On cooling liquid hypoeutectic cast iron immediately after solidification the supersaturated carbon in austenite starts precipitating both intergranularly and intragranularly to form proeutectoid cementite. The present experiments were planned in order to reveal the influence of carbon and chromium content, and the cooling rate on the morphorogy of the proeutectoid cementite and also to study the distribution of chromium among the eutectic cementite, the proeutectoid cementite and the matrix in white cast iron.
  The experimental results were as follows :
  (1) Proeutectoid cementite precipitated first on the boundaries between the primary and the eutectic crystal, making the eutectic cementite massive, then on the grain boundaries of the primary crystals, forming a network structure, and finally precipitated in the grains of the primary crystals as a plate-like cementite or the so called Widmanstätten cementite.
  (2) The carbon content markedly affected the morphology of the proeutectoid cementite. In a Fe-C systam, the largest Widmanstätten cementite was formed with a carbon content of 1.95%.
  (3) The chromium (of 2-4%) lowered the precipitating temperature of both the grain-boundary-cementite and the intragranular plate-like cementite and weakened their growth.
  (4) In white cast iron containing chromium, at high temperature the plate-like cementite precipitated in the neighbourhood of the eutectic cementite and the grain-boundary-cementite rather than in the grains of the primary crystals.
  (5) The chromium in a white cast iron concentrated into the cementite, but the chromium content in the proeutectoid cementite was lower than in the eutectic cementite.

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