Journal of Japan Foundry Engineering Society
Online ISSN : 2185-5374
Print ISSN : 1342-0429
ISSN-L : 1342-0429
Volume 69, Issue 7
Displaying 1-8 of 8 articles from this issue
Research Article
  • Ryoichi Shibata, Tomomi Souda, Hideya Yamane, Takateru Umeda
    1997 Volume 69 Issue 7 Pages 549-555
    Published: July 25, 1997
    Released on J-STAGE: February 01, 2011
    JOURNAL FREE ACCESS
      The effects of pouring temperature on grain size of AC4CH aluminum alloy were studied by using sand mold with a chiller at one side of the casting. When poured from near liquidus temperature, the grain size fell under 100μm except in the area within a few mm from chill surface. The grain size is proportional to the −0.16th power of the cooling rate. On the other hand, when poured from higher temperatures, a dendrite structure appeared, and secondary dendrite arm spacing was proportional to the −0.41th power of the cooling rate. Refinement of grain size by low temperature pouring is due to the homogeneous nucleation of crystals at all over the test castings.
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  • Hiroshi Kawahara, Yoji Awano
    1997 Volume 69 Issue 7 Pages 556-561
    Published: July 25, 1997
    Released on J-STAGE: February 01, 2011
    JOURNAL FREE ACCESS
      It is necessary for reduction of inferior castings due to porosity to clarify the shrinkage morphology of poured melt and the factors affecting its change. The change in the amount of porosity in the test castings was investigated from the viewpoint of hydrogen absorption with oxidation for JIS AC2B secondary alloy ingots. The amount of porosity changes with holding time and temperature of the molten metal as well as the humidity in the holding atmosphere, and the degree of the change differs according to the raw ingot because of the difference in the degree of the hydrogen absorption of the molten metal. Hydrogen absorption is closely related with the oxidation of the molten metal. In the case of the ingot containing both Mg and Ca, considerable hydrogen absorption occurred even during a short holding time, and the oxide formed on the melt surface sank. It is considered that the oxide sinks because Ca improves the wettability between the oxide and molten metal. This suggests that the oxidation of the melt is promoted, causing considerable hydrogen absorption.
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  • Hideo Nakae, Hochul Shin, Naoki Hashihara
    1997 Volume 69 Issue 7 Pages 562-569
    Published: July 25, 1997
    Released on J-STAGE: February 01, 2011
    JOURNAL FREE ACCESS
      The microstructure of flake graphite cast iron is the most important factor in determining the mechanical properties. The microstructure consists of two principal parts : the graphite and the matrix. Therefore, the present paper discusses the influence of the matrix and graphite morphology on mechanical properties. Graphite morphology was varied based on inoculation and holding of the melt and the addition of Ti. The influence of matrix on the tensile properties of cast iron were investigated using kinds of heat treatments. The experimental results were as follows : (1) The influence of graphite morphology on tensile strength of cast iron can be explained by the Rule of Mixture. (2) In the case of the difference of elongation between A-type graphite samples and D-type graphite samples is more than 0.4%, we can use the Rule of Mixtures. But when the difference is less than 0.2%, can not be used the Rule.
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  • Seiji Saikawa, Kiyoshi Nakai, Yasuo Sugiura, Akihiko Kamio
    1997 Volume 69 Issue 7 Pages 570-577
    Published: July 25, 1997
    Released on J-STAGE: February 01, 2011
    JOURNAL FREE ACCESS
      The corrosion behavior of step castings of Al-2.5%Li-2%Mg and Al-2.5%Li-1.2%Cu-0.7%Mg alloys with and without 0.15%Zr and 0.12%Ti were investigated by means of the water-salt spraying test. In the as cast state, weight loss by corrosion in the center part and near the surface part of the step castings of Al-Li system alloys is more or less the same as that of the conventional Al-7%Si-0.4%Mg alloy A356. This is due to the formation of corrosion products such as Na (CICN), Cu3 (CO3)2 (OH)2 and Al (OH)3 over corrosive δ (AlLi) crystallized phases. In the Al-Li alloys aged at 453K for 36ks after solutionization, the corrosion resistance in the center parts of the castings becomes lower than in those of as cast ones. But in T6 treated Al-Li alloys, the corrosion resistance in the parts near the casting surface is high compared with that in the center parts, because of the difference in the amount of metastable state δ’ (Al3Li), S’ (Al2CuMg) and T1(Al2CuLi) precipitates.
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  • Yoshikazu Genma, Yoshiki Tsunekawa, Masahiro Okumiya, Yuko Tanada, Nao ...
    1997 Volume 69 Issue 7 Pages 578-584
    Published: July 25, 1997
    Released on J-STAGE: February 01, 2011
    JOURNAL FREE ACCESS
      This study is aimed at examining the influence of ultrasound-assisted exothermic reaction and improved wettability on the incorporation of Al2O3 particles into molten aluminum alloy in melt stirring. The Al2O3 particles with premixed nickel powder were added to molten Al-5mass%Mg alloy and stirred at a rotation speed of 16.7rps at 1023K in a nitrogen atmosphere. The ultrasound was then transmitted to the molten aluminum alloy with a ceramic plate. The application of ultrasonic vibration to melt stirring not only improves the apparent wettability, but also helps to dissolve the nickel powder thoroughly into molten aluminum alloy. The exothermic reaction of the nickel aluminide formation is promoted by ultrasonic vibration applied. This exothermic reaction leads to a local temperature rise of the molten aluminum alloy, which also improves the wettability. The ultrasound-assisted exothermic reaction of the nickel aluminide formation contributes to an increase in the engulfed Al2O3 particles and also the preparation of pore-free composite slurry.
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