鋳造工学
Online ISSN : 2185-5374
Print ISSN : 1342-0429
ISSN-L : 1342-0429
86 巻, 9 号
選択された号の論文の8件中1~8を表示しています
研究論文
  • 森中 真行, 豊田 充潤
    2014 年 86 巻 9 号 p. 703-711
    発行日: 2014/09/25
    公開日: 2017/04/03
    ジャーナル フリー

      The fatigue strength of aluminum alloy casting is influenced by shrinkage porosity. However, the effect of impurity elements on the formation behavior of shrinkage porosity is not necessarily known. In this paper, investigations were conducted on the effects of phosphorus, an impurity element, on the formation behavior of shrinkage porosity in Al-7%Si alloys, using an uncontrolled unidirectional solidification method. The results are as follows.

      Shrinkage porosity is unlikely to form in alloys not containing phosphorus, and likely to form in those that do, due to the following reasons : First, it is thought that the interface of the solid AlP in molten metal and molten metal acts as the site of porosity generation. The second reason is because protuberance was observed at the surface of the primary α-Al dendrite in the porosity of an alloy not containing phosphorus. This protuberance is thought to be a divorced eutectic α-Al phase whose growth precedes the eutectic silicon phase during the cooling process of eutectic solidification. In the case of alloys containing phosphorus, eutectic cells are unlikely to generate because there are no primary α-Al dendrites at the boundary of the crystal grains. Therefore, the liquidus phase of the boundary of the crystal grains is moved to compensate for the solidification shrinkage of eutectic cells. As a result, it naturally follows that, shrinkage porosity is formed at the boundary of the crystal grains.

  • 藤本 亮輔, 平塚 貞人, 堀江 皓, 晴山 巧
    2014 年 86 巻 9 号 p. 712-718
    発行日: 2014/09/25
    公開日: 2017/04/03
    ジャーナル フリー

      In recent years, there has been an increase in the amount of manganese (Mn) contained in cast iron due to changes in raw materials. It is thought that the increase of Mn contents has a bad influence on the mechanical properties of cast iron. This study aims to investigate the effects of Mn content and post inoculation for mechanical properties and structural changes of FCD450-10 with different thicknesses. In this study, spheroidal graphite cast iron was used as specimens with a Mn concentration of 0.3%, 0.6%, 0.9%. The rates of the cooling of specimens to the eutectic temperature were 0.22K/s, 0.12K/s and 0.08K/s, respectively, for different thickness of specimens. It was observed that thick wall specimens with a cooling rate of 0.12K/s or less had large graphite and grain diameters. In addition, when the Mn content was 0.9% or more, coarse cementite occurred in the last region to solidify (intercellular structure) with the segregation of Mn to the cell boundary. On the other hands, for the specimens with post inoculation, graphite nodule count and cell count increased, and the pearlite area decreased. Course cementite also disappeared in the specimens. Mn segregating to cell was concentrated in the pearlite. Mechanical properties decreased with decreasing cooling rate and increasing amount of post inoculant. This is due to chunky graphite formed.

  • 信木 関, 旗手 稔, 烏谷 豪, 宮本 諭卓, 浜坂 直治, 加納 慎也
    2014 年 86 巻 9 号 p. 719-727
    発行日: 2014/09/25
    公開日: 2017/04/03
    ジャーナル フリー

      The aim of the present work is to study the influence of copper content on impact characteristics and mechanical properties of ductile cast irons. Five melts with different chemical compositions from 0 (i.e. FCD) to 2mass% of copper content were produced using a high frequency induction furnace. The melt was poured into a Y-block CO2 sand mould of 32mm in thickness.

      The chemical compositions of the samples are similar to each other in terms of Carbon (3.66mass%) and Silicon (2.52mass%), and the graphite nodularity is about 86% in all samples.

      In as-cast samples, the tensile strength (UTS), elongation, and Brinell hardness, of non-additive element samples (i.e. FCD) were 480MPa, 19.5%, and 157HBW, respectively. The Charpy impact value at room temperature (R.T.) of smooth samples was 95.2J/cm2.

      The strength depends on the Cu contents, and showed the highest value of 958MPa for UTS, and the minimum value of 6.3% for elongation. However, the impact value of the sample containing 2mass% Cu was 25.8J/cm2 at R. T. The impact transition temperature also tends to increase toward R. T. with increasing Copper contents. In order to improve toughness of cast irons for samples containing 1% Cu (named Cu1.0) and 2% Cu (named Cu2.0), normalization heat treatment was carried out in which the treatment temperature is decided based on the thermal expansion measurement results.

      As a result, the area fraction of pearlite in the Cu1.0 and Cu2.0 samples was found to decrease by heat treatment at 1073K. For Cu2.0 samples treated at 1173K, UTS was 951MPa and elongation was 9.5%. The fracture energy at R. T. of these samples was 70J/cm2.

技術論文
  • 村上 雄一朗, 三輪 謙治, 鬼頭 雅幸, 本田 隆, 金武 直幸, 多田 周二
    2014 年 86 巻 9 号 p. 728-733
    発行日: 2014/09/25
    公開日: 2017/04/03
    ジャーナル フリー

      Making slurry with fine and spherical solid particles is one of the most important issues in semi-solid process. In this study, we tried to make slurry by applying mechanical vibration, and investigated the effects of the factors of vibration on the size and shape of solid particles. The slurry was prepared by pouring molten AC4CH aluminum alloy into a vibrating metal container, and the vibration conditions of the container were controlled. As a result, the solid particles in the slurry became fine and spherical with increasing acceleration amplitude at the same frequency, or with decreasing frequency and same acceleration amplitude. On the other hand, at the same velocity amplitude and different frequency and acceleration amplitude, the solid particles became dendritic shape with high or low frequency. The solid particles were most fine and spherical at the frequency of 50Hz. The results of calculating the particle diameter and particle roundness showed that the solid particles became fine and spherical with increasing velocity amplitude. Additionally, the shapes of the solid particles were affected by frequency and displacement amplitude. The solid particles in the slurry became fine and spherical with the application of mechanical vibration higher than a certain frequency and displacement amplitude level. Furthermore slurry with sufficient fine and spherical particles could be obtained by applying mechanical vibration with frequency of 50Hz and acceleration amplitude higher than 49.0m/s2.

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