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60 巻, 9 号
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研究論文
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田中 武雄, 大内 宏, 津田 昌利1988 年 60 巻 9 号 p. 567-572
発行日: 1988/09/25
公開日: 2011/09/08
ジャーナル フリーThe cast surface and cast structure of Zn-22 % Al alloy castings solidified at various cooling rates were investigated by mainly stylus measurement and scanning electron microscopy. The cast surfaces of castings solidified at mean cooling rates over 300°C/min were luster surface which was caused by inverse segregation of α phase having low melting point, which crystallized in the cast surface layer. The asperities occurred on the surfaces of the castings which solidified at slow cooling rates. The distribution of the asperities corresponds to the distribution of the β dendrites in the inside cast structure, and these asperities become one of the factors determining the cast surface roughness. There are correlations between the roughness of the cast surface and β-secondary dendrite arm spacing or size of asperities, and the coefficient is variable according to the roughness of the mold wall. The cooling rate during solidification, cast structure of the casting and the roughness of the mold wall strongly participate in the roughness of the cast surface.抄録全体を表示PDF形式でダウンロード (873K) -
中澤 哲夫, 森本 庄吾, 酒井 淳次1988 年 60 巻 9 号 p. 573-577
発行日: 1988/09/25
公開日: 2011/09/08
ジャーナル フリーThermal properties such as thermal conductivity(λ), specific heat(c) and thermal diffusivity(k) of the mold were obtained by calculation and casting experiments. The values of λ, c and k of the mold hardened rapidly by CO2 gas were 0.001cal/cm⋅°C⋅s, 0.425cal/g⋅°C, 0.027cal/cm2⋅°C⋅s1/2 respectively. Using these values, thermal distribution in the mold was estimated by computer simulation. Evaluation of collapsibility of the mold was done to compare with the results of computer simulation, examination of retained strength of the mold and casting experiment. It was found that experimental results agreed well with the results of computer simulation. From these results, this molding process appears to be applicable to aluminum alloy, cast iron and cast steel, when the ratio of the diameter of the core (A, mm), to the thickness of casting (B, mm) and the ratio of A/B are under 15, over 1 and over 2 respectively.抄録全体を表示PDF形式でダウンロード (662K) -
前園 敏郎, 高橋 良治, 末永 允1988 年 60 巻 9 号 p. 578-583
発行日: 1988/09/25
公開日: 2011/09/08
ジャーナル フリーIn order to study the effects of graphite nodule size and testing temperature on the fracture toughness of ferritic spheroidal graphite cast iron, two series of specimens with different silicon content whose mean graphite nodule size was adjusted to four levels were examined. The fracture toughness test was carried out by three point bending of notched bar specimen at the temperature of 20°C, −60°C and −130°C. Tensile strength and 0.2% proof stress increases with lowering the testing temperature. On the contrary elongation tends to decrease. When the testing temperature are 20°C and −60°C, the fracture toughness KIC increases with increasing the graphite nodule diameter. However, at −138°C, KIC decreases with increasing the graphite nodule diameter. When the testing temperatures lower the fracture mode changes from ductile to brittle. βc (1/B⋅KCI2/σys2) is used as a standard for such a transition of fracture mode. And the stress condition at the apex of the crack draws to a plain strain when the βc decreased. When the testing temperature were 20°C and −60°C, this βc decreases with decreasing the mean graphite nodule diameter. However, at −130°C, βc decreases with increasing the mean graphite nodule diameter.抄録全体を表示PDF形式でダウンロード (668K) -
田中 雄一, 沢崎 義久, 石坂 安彦, 平岡 武1988 年 60 巻 9 号 p. 584-589
発行日: 1988/09/25
公開日: 2011/09/08
ジャーナル フリーWet slip-rolling wear tests of flaky graphite cast irons having surface hardened layer were performed using Nishihara-type wear tester to examine the effect of the hardened chilled-layer on surface spalling. The thin surface chilled- layer was formed by TIG remelting and following rapid solidification. When the hardness of as-cast or quenched and tempered specimens exceeds approximately Hv500, no further increment of the endurance limit is achieved. However, the rolling contact fatigue endurance limit of the surface hardened irons increases linearly with increasing hardness of chilled-layer. In spite of the maximum shear stress under Hertzian contact of two cylinders is small, cracks initiate at the boundary of chill/heat affecting zone and propagate by linking the flaky graphite in the direction palallel to the contact surface. The crack initiation in the chilled-layer is difficult, because of the absence of the graphite acted as a stress raiser.抄録全体を表示PDF形式でダウンロード (791K) -
岩堀 弘昭, 高宮 博之, 米倉 浩司, 山本 善章, 中村 元志1988 年 60 巻 9 号 p. 590-595
発行日: 1988/09/25
公開日: 2011/09/08
ジャーナル フリーIn castings of Al-Cu-Si AC2B alloys containing more than 0.5%Fe, the shrinkage porosity is encouraged with an increase in iron content. Such shrinkage porosity results from the fact that the alloys are uncompensatory for shrinkage in the early stage of solidification because the crystallization temperature of the needle-like iron compound rises with an increase in iron content and it results in the rise of the feeding limit temperature. When Mn or Be is added to these alloys, the morphology of the iron compound changes to chinese script. Consequently, the occurrence of the shrinkage porosity is inhibited by the improved feedability of the alloys, which are able to compensate for solidification shrinkage until lower temperatures.抄録全体を表示PDF形式でダウンロード (737K) -
恒川 好樹, 奥宮 正洋, 新美 格, 山田 忠彦1988 年 60 巻 9 号 p. 596-601
発行日: 1988/09/25
公開日: 2011/09/08
ジャーナル フリーFibrous preforms of precipitation-hardenable stainless steel (SUS631) with one-dimensional alignment were prepared in a magnetic field applying ferromagnetism of strain induced martensite due to cold work. The alignment angles to the longitudinal axis have a nearly normal distribution in the fibrous preform. The SUS631 fibrous preforms were then infiltrated by molten magnesium alloy (MC2). Heating up to 973K for infiltration causes the tensile strength of SUS631 fibers to decrease to the same as that of SUS304 because of decomposition of the martensite and disappearance of the workhardening effect. However, the tensile strength of the SUS631 fibers is improved to 1,500MPa after aging at 773K for 3.6ks, but is not improved in SUS304. The tensile strength of the SUS631/MC2 composites linearly increases in the volume fraction range of 0.30-0.45. For example, 612MPa at the volume fraction of 0.45 was obtained. But it was somewhat lower than that predicted by Fukuda and Chou's modified rule of mixture.抄録全体を表示PDF形式でダウンロード (718K)
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