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MICRODISTRIBUTION OF NODULIZER IN VARIOUS PHASES OF CAST IRON 总被引:1,自引:0,他引:1
应用有机电解液低温电解及放射性测量方法,测定了普通铸铁及高纯Fe-C-Si合金中的合金化Ce量及石墨中的Ce量,石墨中的Ce量大都略高于或相近于基体中的Ce量,在Ce含量相同的情况下,铸铁中的合金化Ce量比钢中多。 涂层法自射线照相结果表明:Ce在片状石墨中呈均匀分布,而在球状石墨中的分布却是多样的。开花状石墨中的Ce多于片状石墨及球状石墨中的Ce.球状石墨周围的铁素体及珠光体是贫Ce.远离球状石墨的珠光体及莱氏体是富Ce.初生奥氏体枝晶转变形成的珠光体和蜂窝状莱氏体都含有较少的Ce,而板状渗碳体型莱氏体含Ce较多.Ce明显富集于共晶时最后凝固的区域。球状石墨的形成主要取决于原铁水中的反球化剂(硫)含量,它的影响比球化剂的残留量或合金化量的作用更大。 相似文献
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过共晶球铁凝固过程中奥氏体的生长方式与形貌特征 总被引:1,自引:0,他引:1
采用着色腐蚀技术显示出过共晶球铁中的高温凝固组织,观察分析过共晶球铁凝固过程中奥氏体的生长方式与形持征。结果表明:在非平衡凝固条件下,过共晶球铁凝固时通常会析出初生枝晶和晕圈枝晶,其形成条件主要与冷却速率和熔体的过冷有关。随铸件模数Mc增大,枝晶数量减少,二次臂间距显著增大,形态趋于不发达,由初生枝晶向晕圈枝晶过渡。当Mc≤0.3cm时,二次臂间距的实测值与理论预测值基本吻合。初生石墨球周围往往形成环状封闭奥氏体壳;共晶前期石墨球周围形成封闭或不封闭的框架奥氏体壳;共晶后期石墨球往往被周边生长着的共晶奥氏体所包覆,最终成为共晶奥氏体的一部分。 相似文献
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The shrinkage and chilling tendency of spheroidal graphite (abbreviated SG) cast iron is much greater than that of the flake graphite cast iron in spite of its higher amount of C and Si contents. Why? The main reason should be the difference in their graphitization during the eutectic solidification. In this paper, we discuss the difference in the solidification mechanism of both cast irons for solving these problems using unidirectional solidification and the cooling curves of the spheroidal graphite cast iron. The eutectic solidification rate of the SG cast iron is controlled by the diffusion of carbon through the austenite shell, and the final thickness is 1.4 times the radius of the SG, therefore, the reduction of the SG size, namely, the increase in the number, is the main solution of these problems. 相似文献
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《International Journal of Cast Metals Research》2013,26(1-4):27-30
AbstractGraphite formation should be strictly suppressed for the most abrasion resistant white cast irons, since austenite (γ)+graphite eutectic structure shows lower hardness and selectively wears thus deteriorates the abrasion resistance even though the austenite transform to hard phase such as martensite. On the other hand, a small amount of fine graphite is desired to distribute in rolls for hot steel mills to suppress the scoring. However, strong carbide formers such as Cr, V, Nb have been increasingly added to rolls, in order to crystallise more harder carbides. As γ+carbide eutectic grows, the residual liquid among eutectic cells becomes poor in carbide formers and rich in elements which promote graphite formation. Therefore an appropriate alloy design is essential for the hot steel milling rolls. In this study, the graphite formation mechanisms are discussed for chromium cast iron, high speed steel type cast iron and Ni hard type cast iron. 相似文献
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金属型球铁磨球非平衡凝固特性的研究 总被引:3,自引:1,他引:3
探索了金属型球铁磨球非平衡结晶过程,并就磨球的非平衡凝固特性进行了较深入的分析研究。过共晶球铁凝固时出现非平衡奥氏体;亚共晶球铁出现晕圈铁素体和非平衡渗碳体相;在柱状晶与等轴晶过渡区中存在着偏聚物。为改善球铁磨球的显微组织及性能,球铁成分应控制在共晶或稍过共晶处。 相似文献
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铸态合金耐磨铸铁适用于大型或复杂结构耐磨件。通过金相组织观察、X射线衍射相结构分析、图像分析仪定量金相测试和力学性能检测,研究了含钨量对铸态290Cr26MoW耐磨铸铁组织、结构和硬度的影响规律。结果表明,在含0~2.79%W的范围内,随着含W量的增加,铸态290Cr26MoW耐磨白口铸铁的初生基体数量减少,共晶团数量增加,共晶碳化物数量增加;铸态290Cr26MoW耐磨白口铸铁的碳化物结构类型没有改变,M7C3型碳化物为共晶碳化物;铸态290Cr26MoW耐磨白口铸铁基体的奥氏体比例增加,马氏体减少。马氏体多位于共晶团,即共晶碳化物周围。铸态290Cr26MoW耐磨白口铸铁的硬度由共晶碳化物数量和硬度以及基体中奥氏体和马氏体数量比共同决定。 相似文献
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Conclusions Interdendritic graphite in cast iron forms upon non-equilibrium solidification of the graphite-austenite eutectic under conditions of limited diffusional mobility of carbon brought about either by supercooling of the melt, or additions of elements which retard the diffusion of carbon. Solidification of the liquid of eutectic composition begins with the formation of austenite, which grows in the form of branched dendrites.The solidification of finely differentiated eutectic begins when the carbon content of the melt reaches a value high enough for the growth of strongly branched graphite crystals.Moscow Institute of Steel and Alloys. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 2–5, May, 1992. 相似文献
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Recent studies revealed that in eutectic to slightly hypereutectic grey irons (CE = 4.3%-4.5%) the presence of austenite dendrites provides an opportunity to improve the cast iron properties, as a high number of eutectic cells are "reinforced" by austenite dendrites. An iron powder addition proved to be important by promoting dendritic austenite in hypereutectic irons, but was accompanied by adverse effect on the characteristics of potential nuclei for graphite. The purpose of the present paper is to investigate the solidification pattern of these irons. Chill wedges with different cooling moduli (CM = 0.11 - 0.43 cm) were poured in resin bonded sand and metal moulds.Relative clear / mottled / total chill measurement criteria were applied. Iron powder additions led to a higher chill tendency, while single inoculation showed the strongest graphitizing effect. The various double treatments show an intermediate position, but the inoculant added after iron powder appears to be the most effective in reducing base iron chill tendency, for all cooling moduli and chill evaluation parameters. This performance reflects the improved properties of (Mn,X)S polygonal compounds as nucleation sites for graphite, especially in resin bonded sand mould castings. Both austenite and graphite nucleation benefit from a double addition of iron powder + inoculant,with positive effect on the final structure and chill tendency. 相似文献
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球墨铸铁激光熔融处理后的组织SCIEI 总被引:4,自引:0,他引:4
应用光学显微镜、扫描电镜和扫描Auger探针对球墨铸铁经激光熔融处理后的组织进行了研究。结果指出,在熔池/基体交界区的石墨球周围存在双壳层组织,它们分别为马氏体+残余奥氏体层和伪共晶莱氏体层。提出了这种组织的形成机制。 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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离心铸造复合辊套用高铬铸铁的组织及性能研究 总被引:1,自引:0,他引:1
根据复合辊套的生产和使用要求,研究了3种成分的高铬铸铁通过金属型铸造后的组织和性能。结果表明,金属型铸造的Cr20高铬铸铁其铸态组织由枝晶奥氏体、共晶奥氏体和共晶碳化物组成;具有较好的韧性,并且有一定的耐蚀性和良好的耐磨性;铸态硬度达到HRC55左右。Cr20高铬铸铁能满足轧辊的生产和湿摩擦条件下的使用要求。 相似文献