鋳物
Online ISSN : 2186-0335
Print ISSN : 0021-4396
ISSN-L : 0021-4396
49 巻, 1 号
選択された号の論文の6件中1~6を表示しています
研究論文
  • 河野 顕臣, 山田 俊宏
    1977 年 49 巻 1 号 p. 3-8
    発行日: 1977/01/25
    公開日: 2012/07/10
    ジャーナル フリー
      Nitriding of spheroidal graphite cast irons containing 2.04−2.98%Si was carried out at various temperatures from 500 to 620°C and at various lengths of heating time from 10 to 40hr in a tubular furnace using 100% gaseous ammonia. Spheroidal graphite cast irons were sufficiently hardened by gas-nitriding, resulting in a surface hardness between Hv (100g) 700 and 800, and the depth of hardened layer between 0.2 and 0.4mm. Expansion of the test pieces were observed in proportion to the increase in temperature and heating time, and reached 0.12mm, at maximum. It was considered that the precipitated silicon nitride (Si3N4) contributes to the hardening of the nitrided spheroidal graphite cast iron.
  • 高柳 猛, 加藤 誠, 蓑輪 晋
    1977 年 49 巻 1 号 p. 9-13
    発行日: 1977/01/25
    公開日: 2012/07/10
    ジャーナル フリー
      Synthetic mother slag (SiO2-CaO-Al2O3 ternary system) of acid range was prepared, and the influence of Na2O, Na2SiF6, MnO and Fe2O3 on the viscosity of molten slag was studied. Also, the viscosity of the acid slag obtained from the operating cupola was measured and was compared with synthetic slags.
      The viscosity of molten slag decreased by rise in the temperature. Increasing the CaO content in the slag, decreased the viscosity of molten slag. By adding Na2O and Na2SiF6, the viscosity decreased in the same way as by the addition of CaO. Especially, by the addition of Na2SiF6, there was a remarkable decrease in the viscosity of the molten slag. This effect is due to the considerable break-down of slag structure by the action of F- ion. By the addition of MnO and Fe2O3, the viscosity of molten slag decreased and the influence of both oxides resembled each other. The viscosity of molten slag obtained from the operating cupola was approximate to that of the molten synthetic slags which contained the same amount of the network modifier (CaO, Na2O, MnO, Fe2O3, etc.) as cupola slag.
  • 玉崎 洋一
    1977 年 49 巻 1 号 p. 14-19
    発行日: 1977/01/25
    公開日: 2012/07/10
    ジャーナル フリー
      In the previous report, effect of various alloying elements in the copper-base binary alloys on the thermal decomposition temperature of gypsum which are made to contact with these alloy melts were investigated by the differential thermogravimetric equipment with 20°C/min heating rate and by the decolorization of KIO3 solution due to SO2 generating from gypsum. In order to confirm these results under the casting condition, 80×80×5mm specimens of pure Cu and Cu-base binary alloys with various concentration of alloying elements were cast varying the pouring temperature into the plaster mold, and compared the appearance and roughness of casting surfaces.
      The promotion of the reaction between pure Cu and Cu-base binary alloy melts and plaster molds including more than 60% of alpha gypsum were clearly recognized and the casting surfaces coarsened, when the pouring temperature exceeded the thermal decomposition temperature of gypsum which was investigated in the previous work. Cu-2%Be, Cu-5%Al and Cu-5%Si alloys little reacted with the plaster mold by the formation of stable oxide films in a short period when the pouring temperature was as high as 1,250°C. In the case of Cu-40%Zn and Cu-10%Sn alloy, as a result of insufficient difference between the temperature of thermal decomposition of gypsum and melting point of alloy, the pouring temperature for obtaining good casting surface with the plaster mold was restricted within a certain temperature range where neither the thermal decomposition of gypsum nor the miss-run of melt occur. In the case of Cu-Pb alloy which included 5-10% of Pb, because the thermal decomposition temperature of gypsum and the melting point of alloy was close together to bring about either thermal decomposition of gypsum or miss-run of melt, it was considered that it was impossible to use this alloy with a plaster mold.
  • 相沢 達志, 名取 達雄, 渡辺 昭英, 長谷川 啓治
    1977 年 49 巻 1 号 p. 20-24
    発行日: 1977/01/25
    公開日: 2012/07/10
    ジャーナル フリー
      This investigation was carried out to clarify (1) why metals cool slower in vacuum sealed molds than in green sand mold or self-hardening sand mold, (2) the effect of various degrees of vacuum sealing and grain size of mold sand on the rate of heat transfer. Binder and water were added to the molding sand and N-process molds were also used to compare with the vacuum sealed molds.
      The rate of heat transfer in the vacuum sealed mold is smaller than that in the N-Process mold. The rate of heat transfer decreases by reducing the grain size of molding sand and increasing the degree of vacuum sealing. When there is a binder in a mold, the rate of heat transfer increases. Moisture in the mold has only a slight effect on the rate of heat transfer. It was assumed that the absence of a binder and the presence of rarefied air caused the metal to cool slowly in the vacuum sealed mold.
  • 上田 俶完, 和出 昇
    1977 年 49 巻 1 号 p. 25-30
    発行日: 1977/01/25
    公開日: 2012/07/10
    ジャーナル フリー
      Recently, the improvement of the toughness of iron and steel by reverse transformation is attracting attention. The mechanism of reverse transformation of spheroidal graphite cast iron, however, is considered to be different from steel because of high carbon and silicon content. In fact, during the reverse transformation of ferritic spheroidal graphite cast iron, a remarkable expansion was observed, which was never found in steel. This paper intends to elucidate the mechanism of expansion during reverse transformation of ferritic spheroidal graphite cast iron. The specimen was annealed to obtain a fully ferritic matrix, heated rapidly and held isothermally at the reverse transformation temperature between 800-900°C, and was measured dilatometrically. Metallurgical experiment and colorimetric analysis of carbon cantent dissolved in austenite were also performed. The experimental results were compared with the calculated results from a simple diffusion model.
      Dilatometric behavior during reverse transformation is complicated, but several points, where dl/dt changes remarkably, correspond to the volume fraction of austenite detected by the metallurgical experiment. In the early stage of reverse transformation, a little contraction is observed. This results from the dissolution of a small amount of residual cementite and the decrement of vacancies formed by Kirkendall effect. The remarkable expansion in a later stage of reverse transformation is observed only in ferritic spheroidal graphite cast iron. This phenomenon results from the fact that the density of the austenite matrix with about 0.52-0.53%C dissolved is smaller than that of the ferritic matrix at a given temperature, and that probably, in addition, the graphite becomes porous during reverse transformation.
  • 竹本 義明
    1977 年 49 巻 1 号 p. 31-37
    発行日: 1977/01/25
    公開日: 2012/07/10
    ジャーナル フリー
      Expansion defects such as scab or fin are mostly studied from the standpoint of binder contents and properties. In this paper, these defects in gray cast iron for automobiles were examined with green sand molds and shell molds, particularly from the point of view of feldspar content in silica sand.
      Hot toughness of molding sands increased by increasing the feldspar content in silica sand. This increase in hot toughness was caused by sintering of feldspar grains. It was effective for scab defects in green sand molds and shell molds. Where metal penetration and finning appears on the surface of shell cores which are surrounded by heavy metal sections, feldspar additions have cured the problem in most casess. For example, adding 11% feldspar to silica sand reduced scabs on surfaces of shell cores which were used for transmission cases (about 25kg in weight). In the case of water jacket cores for cylinder heads and diesel engine blocks, it was necessary to add up to 11-37% where most severe finning and penetration occured. When these castings had extremely few holes for ejecting core sands, it was necessary not to add more than 27% of feldspar, because the jacket cores became less collapsible as a result of graze caused by fusion of the feldspar.
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