稀土球铁与稀土-镁球铁中元素的分布

用自射线照相、电子探针及离子探针等方法研究了铈球铁、轻稀土-镁球铁、钇基重稀土球铁、钇基重稀土-镁球铁中铈、钇、镁、钙等球化元素以及硫的分布。自射线照相所获得的乳胶干板各处的黑度分布近似地反映了石墨与基体中放射性物质的重量百分浓度。在金相显微镜和扫描电子显微镜观察中均发现,有的球墨有核心。电子探针的探测结果说明:在铈球铁中,有的球墨的核心为硫化铈;在用铈、钙稀土合金处理的球铁中,有的球墨的核心有硫化铈和硫化钙;在轻稀土-镁球铁中,有的球墨的核心有铈、镁、硅的化合物。球化元素铈、镁、钇、钙等和反球化元素硫在球墨中的分布是多样的;这些元素的化合物可能构成某些球墨的结晶核心;有的球墨边缘或周围有铈、钇、镁、钙的富集;有的球墨中铈为均匀分布,钇为不规则分布;在相当多的球墨中,没有铈、钇等球化元素的富集。根据球化元素的多种分布形态,认为球墨的成因,也不限于一种。球化剂的主要作用可能是它能去除硫、氧等杂质,改变了馆体的表面张力和熔体-石墨间的界面张力,从而有利于球墨的形成。对双层球墨的成因进行了初步分析。     

DISTRIBUTION OF NODULARIZING ELEMENTS IN R. E. TREATED SPHEROIDAL GRAPHITE CAST IRONS

用自射线照相、电子探针及离子探针等方法研究了铈球铁、轻稀土-镁球铁、钇基重稀土球铁、钇基重稀土-镁球铁中铈、钇、镁、钙等球化元素以及硫的分布。自射线照相所获得的乳胶干板各处的黑度分布近似地反映了石墨与基体中放射性物质的重量百分浓度。在金相显微镜和扫描电子显微镜观察中均发现,有的球墨有核心。电子探针的探测结果说明:在铈球铁中,有的球墨的核心为硫化铈;在用铈、钙稀土合金处理的球铁中,有的球墨的核心有硫化铈和硫化钙;在轻稀土-镁球铁中,有的球墨的核心有铈、镁、硅的化合物。 球化元素铈、镁、钇、钙等和反球化元素硫在球墨中的分布是多样的;这些元素的化合物可能构成某些球墨的结晶核心;有的球墨边缘或周围有铈、钇、镁、钙的富集;有的球墨中铈为均匀分布,钇为不规则分布;在相当多的球墨中,没有铈、钇等球化元素的富集。根据球化元素的多种分布形态,认为球墨的成因,也不限于一种。球化剂的主要作用可能是它能去除硫、氧等杂质,改变了馆体的表面张力和熔体-石墨间的界面张力,从而有利于球墨的形成。 对双层球墨的成因进行了初步分析。     

大型灰铁及球铁件生产中的主要问题讨论

详细介绍了生产大型灰铁和球铁件的技术流程,提出生产大型灰铁件必须重视浇注方法、冒口和冷铁的设计,强调要将各种工艺参数输入电脑,反复模拟试浇并修正;认为大型球铁件特有的问题是:球墨数量少、球墨直径大、球墨畸变、石墨漂浮、化学成分偏析、晶间碳化物和碎块状石墨,指出解决的途径有:强化冷却加速凝固和改进铁液熔炼与处理工艺等。     

微量元素偏析对厚大断面球铁石墨形态的影响

分析了厚大断面球铁件石墨畸变的形成原因及影响因素,浇注了400mm×400mm×450mm的试块研究微量元素偏析对石墨形态的影响。结果表明：开花状石墨的中心部存在Mg、Al、La、Ca、S等元素的富集,这些元素的富集破坏了石墨生长的稳定性;而晶界上V、Ti的偏析和球化元素Mg或RE等氧化形成的氧化夹杂,破坏了奥氏体壳的稳定性,造成石墨畸变;在铁液中添加微量Sb,凝固过程中Sb偏析于石墨—奥氏体界面上,可有效抑制或减缓C向石墨球扩散,限制石墨球生长,抑制石墨球畸变。     

球状石墨的形核与孕育--球墨铸铁基础理论的最新发展(一)

石墨球的形成分两个阶段：形核与生长。虽然形核不影响最终的形状，但它是石墨球形成的重要过程。石墨的形核物质有石墨、硫化物、氧化物、碳化物、氮化物、金属间化合物及气体。各种物质的形核机制可以不同，但是都必须符合晶格匹配关系（失配度小于6%时，形核能力强），以及满足相互的界面能要求。由于球铁过冷倾向大，所以孕育是球铁生产的必须工序。鉴于硫氧化物是球墨形核的重要组分，特介绍一种新型高效孕育剂，其特点在于孕育剂中含有一定的硫氧非金属物质，可补充球化处理后铁液硫、氧的贫缺。     

大断面球墨铸件球化衰退的分析与处理

在生产球墨铸铁时,铸铁中的石墨形态常常发生变化。尤其是在浇铸大断面球墨铸铁件时,铸件中心的石墨经常出现球化衰退现象。通过分析球化衰退的原因,提出了严格控制铁液成分、合理使用球化剂等改进措施,有效地提高了大断面球墨铸件的质量。     

风电球铁材料球墨形成的原理及工艺

阐述了风电球墨铸铁球墨形核、生长原理与孕育、球化处理的关系。石墨的形核分为均匀形核和异质形核,形核物质与石墨的失配度要小于12%是孕育处理和孕育剂选用的理论基础,孕育处理可以有效增加石墨核心数,孕育以邻近浇注为原则,且采用多次孕育法。球墨的生长必须有强烈的过冷以满足球墨缺陷生长的条件,介绍了提高铁液过冷度的主要方法——球化处理法,介绍了球化剂的选择和使用方法。     

耐热球墨可锻铸铁的研究

与一般球铁类似，硅系耐热球铁也容易形成缩松，故而不宜用在对铸件有气密性要求的工况，为此，在中硅耐热球铁的基础上，仿用球墨可锻铸铁的生产工艺，添加Ｃｒ等合金元素，研制出耐热球墨可锻铸铁，与一般的耐热球铁相比，除了明显减少缩松倾向外，它还可以改善铸铁的材质均一及耐热性，因而应用前景广泛。     

大断面球铁碎块状石墨形成原因浅析及若干防止措施

本文从球墨铸铁石墨－－奥氏体共晶团形成及长大过程中的应力出发,分析了大断面球铁热节处非球形石墨－－碎块状石墨的形成原因及若干影响因素,提出了防止措施。     

Y和Sb对厚大断面球墨铸铁石墨形态的影响

通过采用重稀土钇基稀土镁球化剂处理铁液,浇注厚大断面球铁试块,研究了重稀土Y和微量Sb对厚大断面球铁的石墨形态的影响,分析了石墨结晶的核心,并探讨了石墨畸变的原因。试验结果表明,重稀土Y在铁液中形成高熔点氧化物,残存时间长,作为石墨核心,有利于提高抗衰退性能;Sb具有细化石墨球、增加石墨球数、提高石墨圆整度的作用;在厚大断面球铁中,晶界上Ti的偏析和球化元素Mg或稀土等氧化形成的氧化夹杂,破坏了奥氏体壳的稳定性,造成石墨畸变。     

Distribution of some active elements in primary graphite precipitates

The distributions of cerium and oxygen in the matrix and in graphite precipitates of a pure Fe–C–Ce cast iron sample have been studied using scanning Auger microscopy. It is shown that there is no accumulation of any element at the graphite-matrix interface. Cerium was detected in some cases in spheroidal graphite precipitates, most often associated with oxygen. Various non-spheroidal graphite precipitates proved to contain cerium and oxygen suggesting a correlation between cerium content and graphite degeneracy.     

Estimation of the effective conductivities of complex cast iron microstructures using FIB-tomographic analysis

We present the influence of microstructural characteristics of different graphite morphologies on the effective properties of cast iron. First, the properties are compared with existing analytical bounds and predictive schemes. The estimation of the properties of nodular, flake and all intermediate graphite morphologies becomes possible after the analysis of the graphite crystal structure and growth mechanisms. These properties are implemented in a two-dimensional finite element model. It is shown that the consideration of microstructural parameters – volume fraction, surface density and particle shape – provides good estimates of the properties of cast iron with simply connected nodular graphite particles, but is insufficient for interconnected structures with vermicular and flake graphite. The agreement of the experimental results with three-dimensional simulations on real tomographic data proves that the connectivity of phases is one of the determining factors for material properties.     

磷化冷轧基板表面黑变缺陷研究

目的研究严重影响磷化板表面质量的冷轧基板表面黑变缺陷的成因及机理。方法通过金相分析、扫描电镜电子探针、X射线光电子能谱法、辉光放电光谱法、X射线衍射等分析方法,对黑变缺陷进行系统的分析,并对其形成机理进行探讨。结果黑变缺陷样板表面C元素含量约为正常样板的17倍,C元素主要以石墨形式存在。结论由于带钢表层富集大量以石墨形式存在的C元素,诱发了钢板表面黑变缺陷,其形成原因与钢板化学成分、表面状态以及退火等工艺密切相关。     

Mo element-induced wear behavior evolution of self-lubricant Ti(C,N)-based cermets

In the work, Mo element is used to adjust composition and distribution of the lubricating phase of the self-lubricant Ti(C, N)-based cermets. Ring-block wear test of self-mate pairs is conducted. The microstructure and wear behavior evolution of the cermets are investigated. The results indicate by adjusting the content of Mo, the distribution of graphite on the surface of the self-lubricant cermets changes. With the increase of Mo content, the volume of graphite decrease, and the undissolved Mo increase. During self-mate pair sliding wear, the tribolayer transform from graphite to graphite+MoOx and then to MoOx. The cermets with 4 wt%. Mo show the best tribological properties, which shows a smooth and dense composite tribolayer formed mainly by graphite and MoOx.     

影响薄壁球墨铸铁白口倾向和球墨数量的因素分析

研究了不同的冷却速度、稀土加入量、碳量、硅量、Si／C、Mn／S及孕育处理等工艺时薄壁球墨铸铁球墨数量和白口深度的影响。结果表明，随着冷却速率增加，薄壁球墨铸铁石墨小球越多，但容易产生白口。冷速较大时，加入稀土元素进行孕育和控制碳当量，可以有效的消除薄壁球墨铸铁的白口现象，当Si／C大于0．80、Mn／S大于20时薄壁件白口倾向较小。     

Anti-oxidation behavior of chemical vapor reaction SiC coatings on different carbon materials at high temperatures

To protect carbon materials from oxidation, SiC coatings were prepared on carbon/carbon(C/C) composites and graphite by chemical vapor reaction. SEM and XRD analyses show that the coatings obtained are composed of SiC grains and micro-crystals. The influence of different carbon substrates on oxidation behavior of coated samples was investigated, and then their oxidation mechanisms were studied. Oxidation test shows that the SiC coated graphite has a better oxidation resistance than SiC coated C/C composites at high temperatures (1 623 K and 1 823 K). In the oxidation process, the oxidation curves of SiC coated C/C composites are linear, while those of SiC coated graphite follow a quasi-parabolic manner. The oxidation mechanism of the former is controlled by chemical reaction while the latter is controlled by oxygen diffusion based on the experimental results. The variation of oxidation behavior and mechanism of SiC coatings on two kinds of carbon substrates are primarily contributed to their structure differences.     

新型Ni3Al/石墨高温固体自润滑材料的制备及其性能

采用熔炼法, 制备出新型Ni3Al/石墨抗高温、耐腐蚀固体自润滑材料.结果表明: Al不仅是强化合金基体的元素, 而且是一种使片状石墨转变为球状石墨的球化剂; 铝与氧结合成渣降低了氧在石墨表面的吸附.建立了界面能和过冷度对石墨生长形态影响的动力学模型; 分析表明, 石墨在洁净的液态金属中结晶, 由于(1010)棱面与(0001)基面的温度回升速率的差异, 促使石墨球状生长.石墨经球化处理后, 材料的冲击韧性得到提高; 将该材料与GCr15轴承钢及45﹟退火钢进行干摩擦磨损时, 摩擦因数分别为0.36和0.40.     

Effect of nickel-plated graphite on microstructure and properties of matrix for Fe-based diamond tools

Nickel-plated graphite particles and unmodified graphite particles with different contents were added to the Fe-based diamond composites. The basic properties of those specimens were measured, including relative density, hardness, bending strength, abrasion ratio and holding force coefficient. And also, SEM, XRD and EDS were used to carry out microstructure characterization, phase analysis and element distribution of these specimens. The results show that nickel plating effectively improves the surface wettability of graphite particles. And it is determined that an element diffusion zone is formed on the transition interface between the nickel-plated graphite and the matrix materials, effectively enhancing the interfacial bonding strength. Also, the pores and cracks in the matrix generated by adding the graphite particles are reduced after nickel plating. Thus, the loss of basic properties of the specimens is restrained. But it is found the higher the graphite content is, the weaker the positive effect of nickel plating is. In addition, it is revealed that nickel plating plays a conducive part in the formation of graphite lubricants on the working surface, and nickel-plated graphites can slow down the thermal corrosion of the diamond particles inside the high-temperature sintered specimens.     

超高碳钢石墨化的热力学分析及研究

对喷射态超高碳钢和普通铸造的母合金1．25C-3．0Si-1．5Cr进行了热轧试验，发现在渗碳体和奥氏体双相区热轧时有条状石墨生成。喷射态超高碳钢较母合金中的石墨数量少且石墨较细。从热力学角度分析了元素对石墨化的影响，得出变形可促进石墨的形成。通过控制化学成分，选择合理的热轧工艺减小碳的偏析，可有效抑制石墨的生成。     

锰对灰铸铁凝固特性的影响

灰铸铁的含锰量在0．5％－2．3％范围内变化时，对其一次结晶的热分析曲线特征点，结晶白口倾向、铁液表面张力变化、一次结晶组织特点等，进行了较系统地统计回归分析与研究讨论；试验发现，反石墨化的正确偏析元素可促进1种新型“逆B型”石墨出现，其分布特征完全不同于现有国标已命标的A、B、C、D、E、F型石墨。