Journal of Japan Foundry Engineering Society
Online ISSN : 2185-5374
Print ISSN : 1342-0429
ISSN-L : 1342-0429
Volume 80, Issue 9
Displaying 1-2 of 2 articles from this issue
Research Articles
  • Shuji Tada, Yuya Makino, Toshiyuki Nishio, Keizo Kobayashi, Ken Aoyama
    2008 Volume 80 Issue 9 Pages 531-535
    Published: September 25, 2008
    Released on J-STAGE: February 21, 2014
    JOURNAL FREE ACCESS
      There are hopes that production costs and environmental load in foundry works can be reduced by employing the frozen mold which is made by refrigerating a mixture of only sand and water. In this study, the transition of the mechanical properties of the frozen mold as it was being thawed and were examined with the aim of applying the frozen mold to product parts with small heat capacity, such as cores. The compressive strength of a standard frozen mold consisting of only sand and 5mass% water dramatically decreased when it was thawed and the strength could not be recovered by drying. In contrast, another frozen mold produced by substituting colloidal silica solution for water showed some compressive strength even in the thawed state, and the strength increased with subsequent drying, while keeping excellent strength during the frozen state. The reusability of sand when colloidal silica was used for producing the frozen mold was also investigated. The compressive strengths did not deteriorate under any states; frozen, thawed, or dried even though the sand was used repeatedly. The above results prove that frozen molds prepared by mixing sand and colloidal silica solution has the potential to be applied to product parts with small heat capacity, such as cores, and possesses excellent reusability without the need for any screening process, thus contributing to the improvement of environmental load.
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  • Shigeo Tsukahara, Mieko Ide
    2008 Volume 80 Issue 9 Pages 536-540
    Published: September 25, 2008
    Released on J-STAGE: February 21, 2014
    JOURNAL FREE ACCESS
      The austempered ductile iron (ADI) has been used as an industrial material, since it is a high strength material with good ductility and toughness. ADI, however, becomes very brittle when it is used in aquatic environments. In cast iron, a local cell is formed between the graphite and the matrix in acid solution and hydrogen is generated by the galvanic reaction. The experimental results suggest that the reduction of strength and ductility of the ADI may be caused by this hydrogen. Excellent properties of strength and ductility are observed even under aquatic environment in ADI with decomposed retained austenite which is produced by annealing at 673~723K after austempering (named ADI-AN). And the similar excellent tensile properties are observed also in the ADI without retained austenite which is produced by austempering at 653K after autenitizing at 1173K and cooling gradually to 1033K (named α-ADI). The strength and the toughness of ADI-AN in air are almost the same as those of the quenched and tempered ductile iron having sorbite structure. However, the toughness of α-ADI is higher than that of the quenched and tempered ductile iron with the same strength.
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