鋳物
Online ISSN : 2186-0335
Print ISSN : 0021-4396
ISSN-L : 0021-4396
63 巻, 10 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
  • 大政 光史, 大中 逸雄
    1991 年 63 巻 10 号 p. 817-822
    発行日: 1991/10/25
    公開日: 2011/07/08
    ジャーナル フリー
      An algorithm based on the direct finite difference method with staggered mesh is proposed to simulate mold filling with melt front. The flow model in the method has been made clear, showing necessity to use up-wind velocity for convection term. Shape of melt front is estimated from filled volume in each element, and surface tension is considerd in the equation of motion. Good agreement is demonstrated between simulated and measured mold filling for a water model of gravity casting and aluminum die casting.
  • 麻生 節夫, 大城 桂作
    1991 年 63 巻 10 号 p. 823-829
    発行日: 1991/10/25
    公開日: 2011/07/08
    ジャーナル フリー
      To clarify the fomation processes of eutectic structure unidirectional solidification of 25 % Cr white cast irons containing 1-2 % B, the distribution of solute elements in liquidus region at solid / liquid interface zone and the composition of eutectic compounds formed were examined mainly by means of EPMA technique. Eutectic solidification of the 25 % Cr alloys occurred through two step processes with the primary and secondary eutectics as well as that of the 15 % Cr alloy which was reported in the previous paper. In the low B alloys, both of the eutectics were γ+M23(C, B)6, though they had different composition. They solidified in a rod-like three-dimensional dendritic structure. In the high B alloys, the primary eutectic was γ+M2B which grew in network structure, while the secondary eutectic was γ+M23(C, B)6, which grew in rod-like structure as well as that in low B alloys. Front position of the secondary eutectic was revealed by a discontinuous point on the fraction of solid-distance curve in solid / liquid zone. A one-to-one correspondence was confirmed between solute concentration profile in the liquid region of solid / liquid zone and change in composition of the eutectic compounds formed.
  • 陳 立輝, 呂 傳盛
    1991 年 63 巻 10 号 p. 830-835
    発行日: 1991/10/25
    公開日: 2011/07/08
    ジャーナル フリー
      High-Cr white cast irons of six eutectic carbide area fractions varied from 9.7 % to 24.5 % were abraded by 100-grit SiC polishing papers, with the test conditions of 3 mm × 3 mm apparent contact area, 21 N normal load and 65 mm/s sliding speed. The results reveal a plastic grooving dominated process. By increasing the carbide area fraction, coarsening the eutectic morphology and strengthening the matrix phase, the abrasion resistance is improved. The improvement can be rationalized with the linear equation that Rt=Rm + (kRc - Rm) Ac, where Rt is the abrasion resistance of a given material with Ac as its carbide area fraction. Rm and Rc are the abrasion resistance of pure matrix material and pure carbide material, respectively, k is a modification factor which emphasizes interphase interaction.
  • 沖 善成, 吉田 善博, 上坂 美治
    1991 年 63 巻 10 号 p. 836-841
    発行日: 1991/10/25
    公開日: 2011/07/08
    ジャーナル フリー
      This report discusses the cast hemispherical core dies for the hot extrusion of the hollow shaped aluminum alloys. The hemispherical core die is casted in SKD 61. The end face of the core of this die is hemispherical on the entry side of the billet. The maximum tensile stress appearing around the root of a mandrel of the core is remarkably reduced in comparison with a port-hole die, which results in suppresion of crack initiation. The solidification simulation was used for the purpose of predicting the solidification defects and increasing the temperature gradient at the point of tensile stress. The hemispherical cast dies with the temperature gradient of more than 303 K/cm had the same high-temperature stress characteristics (according to the tensile test piece, which is cut from the cast die) and demonstrated the same extrusion features as that of forged hemispherical core dies. By using this type of cast hemispherical core die, the raw material weight is 38.3 % of a forged hemispherical core die. Moreover, the die forming time is shortened by 50 %.
  • 堤 信久, 高林 久充, 古田 貴久, 草刈 浩介
    1991 年 63 巻 10 号 p. 842-847
    発行日: 1991/10/25
    公開日: 2011/07/08
    ジャーナル フリー
      Dispersion of residual thermal stress by making interlayers of ceramics / metal bonding having controlled compositional gradients has been expected. Various types of the Mo-Si3N4 multilayers construction material with controlled compositional gradients by using particle arrangement method were made in our laboratory. Local cracks, however, were observed at the special part in reaction sintered body having controlled compositional gradients. Because, the part having around 20 vol % Mo expanded larger than other part of the body. It has been clarified by the X-ray analysis that the formation of MoSi2 in the part of specimen containing 20 vol % Mo after sintered at 1673 K has the main effect on its expansion. To prevent this formation, the examination of sintering temperature and composition of specimen was carried out, but occurrence of cracks were not prevented. In this system of the combination, it is comparatively difficult to produce by reaction-sintering of Mo-Si3N4 construction material with controlled compositional gradients under author's experimental condition. By applying hotpress-sintering of the specimen added with 6 vol % of Y2O3 as sintering aids for Si3N4 in every layers, however, obtained a sintered body without any cracks.
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