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首页> 外文学位 >FACTORS AFFECTING GRAPHITE MORPHOLOGY, MATRIX STRUCTURE AND TENSILE PROPERTIES OF COMPACTED GRAPHITE CAST IRONS.
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FACTORS AFFECTING GRAPHITE MORPHOLOGY, MATRIX STRUCTURE AND TENSILE PROPERTIES OF COMPACTED GRAPHITE CAST IRONS.

机译：压实石墨铸模离子的影响石墨形态，基体结构和拉伸性能的因素。

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摘要

The scanning electron microscopic observations indicate that graphite morphologies can be changed from one form to another over a wide range of graphite formations by altering the solidification cooling rate and/or the amount of nodulizing elements present such as magnesium or rare earths.; It was also observed that those changes occur by a gradual change in the graphite morphology and do not occur in an interrupted manner which would be characteristic of unique nucleation events required for each graphite form.; Increasing cooling rate and/or increasing the effective presence of nodulizing elements resulted in the following change in graphite formations: type A flake, type B flake, type D undercooled flake, coral, compacted, deteriorated forms of spheroidal, and spheroidal graphite.; Observations also indicate compacted graphite, like flake graphite is interconnected within a eutectic cell, but predominant growth of these individual stubby lamellae, as seen under the microscope on a flat surface, take place along the C axis like spheroidal graphite. However, it is noted that clear eutectic cell boundaries on macroscopically etched samples were revealed in samples only exhibiting fully compacted graphite morphology and no clear eutectic cell boundaries were observed when the graphite form was predominantly either degenerated spheroidal or spheroidal. This suggests that eutectic cell growth characteristics of compacted graphite are similar to that of flake graphite.; It was observed that increasing silicon content upto 2.70% increased the percent compacted graphite and decreased the amount of pearlite content present, but further increase of silicon upto 2.93% resulted in decrease of percent compacted graphite and the amount of pearlite content present further.; A linear equation, Y = -0.38X + 4.46 (+OR-) 0.17, where Y = %C and X = %Si, was found for the determination of C-Si ratio and CE to produce "acceptable" compacted graphite cast iron. It was observed that the graphite floatation was inevitable in high CE (over 4.60) heats.; Optimum Mg-S, and Ti-Mg ratios to produce "acceptable" compacted graphite cast iron were determined from 2/3 to 7/1 and from 10/1 to 4/1, respectively, in the range of Mg content at 0.013-0.023%.; The successive increase of titanium additions increased the chill depth, and percent compacted graphite slightly revealing no less than 90% compacted graphite structure in both rare earth treated and lanthanum ferrosilicon treated heats. It was also observed that compacted graphite structures became thinner with increasing Ti additions and that a nearly negligible change in matrix structure resulted.; The successive increase of aluminum additions decreased chill depth and resulted in negligible change in both percent compacted graphite and matrix structure. However, it was observed that compacted graphite structures became thicker with increasing aluminum content.; The tensile properties of compacted graphite cast irons made with either MgFeSiTi alloy or rare earth alloy can be controlled by not only matrix structure, but also by graphite morphology. The tensile properties of compacted graphite cast irons may be reported as intermediate between those of ductile iron and those of gray iron at the equivalent BHN and matrix structure.; It was found that a good correlation between tensile strength and hardness exists satisfying the equation; TS = 0.30 x BHN + 5.08 with a correlation coefficient of 0.96.
机译：扫描电子显微镜观察表明，通过改变凝固冷却速率和/或存在的结瘤元素（例如镁或稀土）的数量，可以在很宽的石墨形成范围内将石墨形态从一种形式改变为另一种形式。还观察到，那些变化是通过石墨形态的逐渐变化而发生的，而不是以中断的方式发生的，这是每种石墨形式所需的独特成核事件的特征。冷却速度的增加和/或结瘤元素的有效存在的增加，导致了石墨形态的以下变化：A型鳞片，B型鳞片，D型过冷鳞片，珊瑚，密实的，变质的球状和球状石墨。观察结果还表明，致密石墨就像片状石墨在共晶胞内相互连接，但如在显微镜下在平坦表面上观察到的那样，这些单个的粗短薄片的主要生长沿球状石墨沿着C轴发生。但是，应注意的是，在仅表现出完全压实的石墨形态的样品中，在宏观蚀刻的样品上显示出清晰的共晶细胞边界，并且当石墨形式主要是简并的球形或球形时，没有观察到清晰的共晶细胞边界。这表明压实石墨的共晶细胞生长特性与片状石墨相似。观察到，将硅含量提高到2.70％，增加了压实石墨的百分比，减少了珠光体含量的存在，但是，硅含量进一步提高到2.93％，导致了压实石墨的百分比和珠光体含量的进一步降低。找到一个线性方程，Y = -0.38X + 4.46（+ OR-）0.17，其中Y =％C和X =％Si，用于确定C-Si比和CE以生产“合格的”压铸石墨铸铁。观察到，在高CE（4.60以上）加热​​下，石墨的浮选是不可避免的。在0.013的Mg含量范围内，分别确定2/3至7/1和10/1至4/1的最佳Mg-S和Ti-Mg比，以生产“合格的”压实石墨铸铁。 0.023％。钛添加量的连续增加增加了激冷深度，并且在稀土处理和硅铁镧处理的热中，压缩石墨的百分比略显出不少于90％的压缩石墨结构。还观察到，随着钛添加量的增加，致密的石墨结构变得更薄，并且基体结构的变化几乎可以忽略不计。铝添加量的连续增加降低了激冷深度，导致压缩石墨百分比和基体结构的变化可忽略不计。但是，观察到随着铝含量的增加，压实的石墨结构变得更厚。用MgFeSiTi合金或稀土合金制成的压实石墨铸铁的拉伸性能不仅可以通过基体结构来控制，而且可以通过石墨的形态来控制。压实石墨铸铁的抗拉性能据报道是在球墨铸铁和灰铸铁在等效BHN和基体结构之间的拉伸性能。发现满足该方程式时，拉伸强度与硬度之间存在良好的相关性。 TS = 0.30 x BHN + 5.08，相关系数为0.96。

著录项

  • 作者

    PARK, HYUN KEUN.;

  • 作者单位

    The University of Wisconsin - Madison.;

  • 授予单位 The University of Wisconsin - Madison.;
  • 学科 Engineering Metallurgy.
  • 学位 Ph.D.
  • 年度 1981
  • 页码 238 p.
  • 总页数 238
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 冶金工业;
  • 关键词

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