共查询到20条相似文献,搜索用时 78 毫秒
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本文以脱油沥青的高附加值利用为研究目的,采用化学气相沉积和真空热处理相结合的方法,宏量制备得到粒度均一、高的石墨化程度和高的热稳定性石墨微球(GraphiticSpheres,GS5)。通过SEM、HRTEM、XRD和TGA等测试手段对比碳微球和石墨碳球,高温热处理得到的碳球石墨化程度高,热稳定性好。在热动力作用下,无序结构的碳微球结构逐步向有序的石墨碳结构过渡,形成了石墨球。 相似文献
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球墨铸铁的石墨球数及其影响因素 总被引:2,自引:1,他引:2
球铁生产中希望获得球形圆整、分布均匀、球径较小和数量较多的石墨球。国标GB9441-88“’对球化级别(球化率)和石墨大小作了分级,但没有石墨球数的评定级别。美国铸造师学会(AFS)编写的《球墨铸铁金相图谱)t”(以下简称AFS图谱)中把石墨球数由25个/mm’到300个/mm’,分为7个级别。在球化良好和石墨分布均匀的球墨铸铁中,石墨球数与石墨大小(球径)有一近似的对应关系,如表1。由表1可见,用石墨球数来评价球铁组织中石墨的均匀程度要比用石墨大小(或球径)作评价参数,更为详实和精确。目前,国内对石墨球数的研究较少… 相似文献
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利用原料的遗传性制成化学成分基本相同但组织不同的球墨铸铁,研究了低温热处理对球铁中不同原始石墨组织的影响.结果表明,经低温热处理后,铸态石墨化程度低且球化效果较差的石墨组织,球化率和球化级别显著提高,石墨的平均球径增加;铸态石墨化程度高且球化效果比较理想的石墨组织中出现了部分点状石墨,石墨球的平均球径减小,且点状石墨群和球状石墨群有规律地交替分布,而石墨的球化等级和球化率没有明显变化. 相似文献
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在为长春汽车研究所S6110发动机研制了简体铸造珠光体球墨铸铁活塞环后,为探索球铁活塞环批量生产的可能性,又进行了单体铸造工艺的试验。在试验过程中,遇到了石墨球计数问题。按照新的概念,石墨球数——单位平方毫米中的石壁球数量为衡量孕育效果的主要指标之一,也是衡量产品质量的重要指标之一,国外制造厂商往往以此作为商品宣传的重要项目。国内一般球铁铸件的石墨球数,采用炉前孕育时为150个/mm~2左右,采用瞬时孕育时为240~250个/mm~2,国外菲亚特公司的曲轴采用型内球化工艺,石墨球数达400~500个/mm~2。美国的小模数汽车另件的石墨球数为1550个/mm~2。国内某厂试制的单体铸造球 相似文献
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《International Journal of Cast Metals Research》2013,26(1-4):81-85
AbstractAlthough it is known that the addition of bismuth refines the graphite nodule in spheroidal graphite cast iron, the refinement mechanism has not yet been clarified. In this research, the effect of bismuth on the refinement has been investigated by examining the microstructure of the spheroidal graphite cast iron containing a small amount of bismuth. Bismuth was added at 0˙01 mass% to the spheroidal graphite cast iron melt containing 3˙5–3˙7 mass% carbon and 2˙0– 2˙8 mass% silicon, then the melt was poured into the mould to obtain the stepped test bar with 2, 3, 5 and 10 mm thicknesses. The graphite nodule increased as the bismuth content increased. The diameter of the graphite nodule decreased as the thickness decreased, namely, as the cooling rate increased. The graphite nodule was further refined by the addition of bismuth. The increase in silicon content increased the graphite nodule count and the ferrite in the matrix. It postulated that bismuth exists as simple substance or a compound in the vicinity of the nucleus of the graphite. 相似文献
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Liu Jin-hai Yan Jian-shuai Zhao Xue-bo Fu Bin-guo Xue Hai-tao Zhang Gui-xian Yang Peng-hui 《中国铸造》2020,17(4):260-271
The quantity and morphology of spheroidal graphite have an important effect on the properties of ductile iron,and the characteristics of spheroidal graphite are determined by the solidification process.The aim of this work is to explore the precipitation and evolution of graphite nodules in hypoeutectic,eutectic,and hypereutectic ductile irons by thermal analysis,liquid quenching and metallographic technique.Results show that hypoeutectic ductile iron has the longest solidification time and the lowest eutectic temperature;eutectic ductile iron has the shortest solidification time;hypereutectic ductile iron has the highest eutectic temperature.After solidification is completed,hypoeutectic ductile iron has the lowest nodule count,nodularity and graphite fraction;eutectic ductile iron has the highest nodule count,nodularity and the smallest nodule diameter;hypereutectic has the highest nodule diameter and graphite fraction.The nucleation and growth of graphite nodules in hypereutectic ductile iron starts before bulk eutectic crystallization stage,however,the precipitation and evolution of graphite nodules of hypoeutectic and eutectic ductile irons mainly occur in the eutectic crystallization stage.The graphite precipitated in eutectic crystallization of hypoeutectic,eutectic,and hypereutectic ductile irons,are 61%,68% and 43% of total graphite volume fraction,respectively.Simultaneously,there are plenty of austenite dendrites in hypoeutectic and hypereutectic ductile irons,which are prone to shrinkage defects.Therefore,the eutectic ductile iron has the smallest shrinkage tendency. 相似文献
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采用扫描电镜分析了QT900-5(1#试样)和QT900-2(2#试样)的微观组织及断口形貌.结果表明,1#试样石墨球细小,且形状较为圆整;2#试样石墨球数量较少,比较粗大.对断口的扫描结果发现,1#试样的微观断裂特征为石墨球与基体形成圆整的韧窝;而2#试样石墨球表面粗糙,且极不规整,断口处出现部分团絮状的硅酸盐.对两组试样的湿化学分析结果表明,1#和2#试样残留Mg含量分别为0.056%和0.035%;而P含量分别为0.036%和0.051%.2#试样较低的Mg残留量和较高的P含量是其韧性较低的原因之一. 相似文献
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R. Salazar F. M. Herrera-Trejo M. Castro J. Méndez N. J. Torres T. M. Méndez N. 《Journal of Materials Engineering and Performance》1999,8(3):325-329
The transformation of austenite to ferrite and graphite or to pearlite in spheroidal graphite cast iron depends on a number
of factors, among which are the nodule count and the cooling rate. In this study, the pearlite fraction decreased as the nodule
count increased for a given cooling rate. Furthermore, as the cooling rate increased, the fraction of pearlite increased.
Both effects were more sensitive at low nodule count. The effects of altering these parameters on the relative amount of pearlite
and ferrite in the matrix of a copper-molybdenum (Cu-Mo) spheroidal graphite cast iron were addressed using heats carried
out in an induction furnace, and the melts were treated with magnesium ferrosilicon in a ladle. To vary the nodule count,
the melts were inoculated with two different amounts of ferrosilicon. Pouring was performed into sand molds of cylindrical
cavities with different section size in order to achieve various cooling rates. Both the nodule count and the cooling rate
affected the relative amount of ferrite and pearlite in the matrix. 相似文献
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A multiphase cellular automaton model was developed to simulate microstructure evolution of near eutectic spheroidal graphite cast iron (SGI) during its solidification process, and both dendritic austenite and spheroidal graphite growth models were adopted. To deduce the mesh anisotropy of cellular automaton method, the composition averaging and geometrical parameter were introduced to simulate the spheroidal graphite growth. Solute balance method and decentered square algorithms were employed to simulate austenite dendrites growth with different crystallographic orientations. The simulated results indicate that the graphite nodule grows in a spherical morphology when the surrounding environment of a single graphite nodule is same. However, for two adjacent graphite nodules, the environment is different. The higher the carbon concentration, the faster the growth of graphite. By comparison with experimental results, it is found that the microstructure evolution of near eutectic spheroidal graphite cast iron during solidification process can be reproduced quantitatively by numerical simulation with this model. 相似文献
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《International Journal of Cast Metals Research》2013,26(1-4):90-95
AbstractThe present study examined the influence of refinement of graphite nodules on microstructure and tensile properties of austempered ductile cast iron (ADI). A casting technique using deoxidation treatment enabled manufacture of thin walled castings made of ductile cast iron without ledebulite. The thin walled casting (t=2 mm) was subjected to extreme refinement of graphite nodules, where the number of graphite nodules was 1750 mm?2. Decrease in graphite nodule diameter resulted in refinement of ausferrite and γ-pool structures in ADI and rapid reaction of austempering. The significant increase in the number of graphite nodules resulted in a remarkable drop in the tensile strength and elongation of ADI. These results can be explained by the graphite nodule distance. 相似文献
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对采用普通孕育剂和采用添加S-O-Ce的孕育剂生产厚壁球墨铸铁件进行了对比,结果显示:采用加S-O-Ce的孕育剂能增加球墨数量、提高球墨圆整度,提高力学性能以及降低缩松倾向.分析了加S-O-Ce孕育剂的孕育机理,认为加S-O-Ce的孕育剂对力学性能的影响是组织改善与抑制有害元素作用的综合结果. 相似文献