鋳物
Online ISSN : 2186-0335
Print ISSN : 0021-4396
ISSN-L : 0021-4396
44 巻, 3 号
選択された号の論文の5件中1~5を表示しています
研究論文
  • 津田 昌利, 江川 勝一
    1972 年 44 巻 3 号 p. 157-165
    発行日: 1972/03/25
    公開日: 2012/09/24
    ジャーナル フリー
      Coarse primary silicon in the cast structure has a bad effect on the mechanical properties such as tensile strength, elongation, impact resistance, etc. of hypereutectic aluminum-silicon alloys. There are many reports concerning the refining method of primary silicon in hypereutectic aluminum-silicon alloy. The flux for refinement of primary silicon developed by the authors, recently, consists of sodium hexametaphosphate (NaPO3)6 and aluminum oxide (Al2O3). Al-20%Si alloy bath melted with 99.99% aluminum and 99.98% silicon was covered with the flux at 800°C and kept for 10 to 15 minutes in this state, after which it was cast into iron or shell mold at 750°C.
      The refinement of primary silicon by the flux treatment was investigated by measuring silicon grain size all over the specimen cast into an iron mold taking longitudinal and cross sections. On the other hand, the specimens cast into a shell mold were used for the test of tensile strength, elongation and hardness of Al-20%Si alloy refined with the flux.
      The results obtained are as follows :
      1) The refinement of primary silicon with the flux which consisted of sodium hexametaphosphate and aluminum oxide at the ratio of 8 to 1, was remarkable with the refined primary silicon size about 20 microns. A uniform structure was observed throught the specimen because of decreasing mass effect by the flux treatment.
      2) The alloys treated with the flux have high values of tensile strength and elongation, but low values of hardness.
      3) When metallic sodium effective for refining eutectic structure was added to the flux, it was found that the flux must be treated just after the addition of metallic sodium so as to prevent the coarsening of primary silicon by sodium.
      4) Hygroscopic property of the fused flux is equivalent to about one hundredth to one three hundredth of the mixture of sodium hexametaphosphate and aluminum oxide.
      5) The flux is advantageous, because only a small amount, that is 1 to 2% of the molten alloy spread over the surface of the molten bath, is sufficient to refine alloys.
  • 大橋 貞文, 北野 隼男, 中山 勝
    1972 年 44 巻 3 号 p. 166-173
    発行日: 1972/03/25
    公開日: 2012/09/24
    ジャーナル フリー
      Erosion scab is likely to occur at pourening when self-hardening mold with organic binder is used for large steel castings because of its low hot-strength. In order to study this phenomena, the initial load-fracture time curves were obtained by measuring the load change with respect to the time kept at 500°C and 1,000°C for the four organic no-baking binder systems such as phenolic-isocyanate, alkyd-isocyanate, phenol and frun-phenol. Furthermore, these results were compared with the actual pouring, while the theoretical pressure of the poured molten metal was calculated.
      The results obtained are as follows :
      1. Urethane hardening mold easily causes erosion scab, because its fracture time is shorter than that of condensation polymerisation hardening mold. In order to prevent the growth of these defects molding sand should be selected with care. It was found that zircon sand was effective.
      2. The possibility of the erosion scab formation can be predicted from the initial load-fracture time curve and theoretical pressure of the molten metal. However, there is an exception in that the mold with a large degree of softening such as phenol-isocyanate no-bake mold causes erosion scab before burn out.
      3. Especially, for the combustion fracture mold such as organic binder mold, the fracture process and time are important. Initial load-fracture time curves may be used as an effective means of estimation of mold properties at high temperatures.
  • 小林 一典, 山屋 洋樹
    1972 年 44 巻 3 号 p. 174-181
    発行日: 1972/03/25
    公開日: 2012/09/24
    ジャーナル フリー
      Generally, core wash is composed of various coating refractories and carriers. It is common practice to select adequate coating refractories according to the kind of molten metal. As for carriers, usually, water or methanol are used. The selection of carriers, however, has been being made on the nature of dressing and the theoretical basis was not clearly understood.
      The authors studied the function of carriers and coating refractories noting a phenomenon of “penetration of coating refractories and carriers into the moulds.” The study of penetration into the moulds will save unnecessary penetration of carriers, minimize decrease in mould strength and defects in casting caused by carriers which remain inside of moulds. This study also will help to protect mould surface from the penetration of molten metals by adjusting the amount of penetration of coating refraotories into the moulds in accordance with the size of castings and materials concerned.
      The penetration of carriers and coating refractories into the moulds refers to characteristics by which carriers or coating refractories penetrate between moulding sands. When only carriers are used the factor which takes part in the phenomenon is considered to be the capillary effect which is a function of viscosity and surface tension of carriers.
      Furthermore, as for the penetration of coating refractories, it is considered that particle size, heat of wetting which is caused by the wetting of the surfaces and especially the degree of polarity of coating refractories and dipole moment of carriers influences the penetration of coating refractories.
  • 西 成基, 上田 俶完, 近藤 靖彦
    1972 年 44 巻 3 号 p. 182-190
    発行日: 1972/03/25
    公開日: 2012/09/24
    ジャーナル フリー
      In order to examine the influence of titanium on the spheroidization of graphite in cast iron, the detrimental critical content of titanium was determined by the addition of 0∼1.5% of titanium to molten metal with 3.51% carbon and 2.70% silicon. 2% of CaCN2 was added to decrease any unfavorable effect of titanium on the graphite spheroidization before Mg treatment. The effects of cooling rate on the graphite spheroidization and on the matrix were also discussed.
     The results obtained were as follows:
      1) The detrimental critical content of titanium on the graphite spheroidization was about 0.20%, but it increased to about 0.43% by addition of 2% of CaCN2.
      2) The increase of insoluble nitrogen in HCl was negligible even when CaCN2 was added. This was due to the formation of TiN which floated on the surface of molten metal.
      3) The number of graphite nodules in cast iron increased with the addition of CaCN2.
      4) The existence of TiN was not detrimental for graphite spheroidization and the formation of TiC was also not detrimental up to 0.24% titanium.
      5) TiN and TiC were randomly distributed in the matrix, but the gravity segregation was partially found.
      6) The increase of cooling rate of molten metal decreases the unfavourable effect of titanium and the size of titanium compounds.
  • 金 水泳, 小岩井 克忠, 星野 和憲, 草川 隆次
    1972 年 44 巻 3 号 p. 191-198
    発行日: 1972/03/25
    公開日: 2012/09/24
    ジャーナル フリー
      The study of solidification mechanism is very important in the elucidation of various properties such as toughness and strength as well as defects such as shrinkage cavities, pinholes, etc. of the spheroidal graphite cast iron. This is why solid density, liquid density, relation between volume of molten liquid and temperature, type of eutectic solidification and expansion-shrinkage at solidification have already been studied on the spheroidal graphite cast iron. The formation of surface solidification layer on hyper-eutectic composition spheroidal graphite cast iron and flake graphite cast iron was studied in this experiment, because this is closely related to the solidification mechanism as with the above mentioned studies. The most important result obtaind through this investigation is that there is a remarkably different type of formation and growth of surface solidification layer between the two kinds of cast iron which clarifies the fact that the two solidification mechanims are very different.
      The results are summarlized as follows.
      1) On the spheroidal graphite cast iron, a very thin film is formed along the wall of the mold when the molten metal reached melting point in the mold. The growth of the thin film at the first stage is very slow with the growth rate at about 0.004 mm/sec. The second stage start at the end of the first stage, the growth rate being 30 times larger than the first stage. The formation and growth of the first stage is the result of the change in graphite shape induced by external gas, but since the film is very thin at this stage, it is probable that the real solidification of this cast iron begins at the second stage.
      2) The formation and growth of surface solidification layer in flake graphite cast iron is similar to the spheroidal graphite cast iron but the formation rate at the first stage is about 6 or 7 times larger than that of the spheroidal graphite cast iron.
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