材料期刊网

Effect of Niobium on Isothermal Transformation of Austenite to Ferrite in HSLA LowCarbon Steel

CAO Jianchun , LIU Qingyou , YONG Qilong , SUN Xinjun

钢铁研究学报(英文版)

Using thermomechanical simulation experiment, the kinetics of the isothermal transformation of austenite to ferrite in two HSLA lowcarbon steels containing different amounts of niobium was investigated under the conditions of both deformation and undeformation. The results of optical microstructure observation and quantitative metallography analysis showed that the kinetics of the isothermal transformation of austenite to ferrite in lower niobium steel with and without deformation suggests a stage mechanism, wherein there exists a linear relationship between the logarithms of holding time and ferrite volume fraction according to Avrami equation, whereas the isothermal transformation of austenite to ferrite in high niobium steel proceeds via a two stage mechanism according to micrographs, wherein, the nucleation rate of ferrite in the initial stage of transformation is low, and in the second stage, the rate of transformation is high and the transformation of residual austenite to ferrite is rapidly complete. Using carbon extraction replica TEM, niobium carbide precipitation for different holding time was investigated and the results suggested that NbC precipitation and the presence of solute niobium would influence the transformation of austenite to ferrite. The mechanism of the effect of niobium on the isothermal transformation was discussed.

关键词: niobium;transformation;ferrite;austenite

Jian ZHANG/Langhong Lou

材料科学技术（英）

关键词:

液态CaO-SiO_2和CaO-Al_2O_3-SiO_2渣中CaO的活度

邹元爔 , 赵彭年 , 曹兆民

金属学报

利用石灰的加碳还原反应,设计了一个新的研究方法,以直接测定液态高炉型渣中CaO的活度.这一方法的成功,依靠溶剂金属的正确选择以降低熔液中钙的化学位,而使金属钙量提高到可以用化学分析测定的水平.我们估计钙在锡稀溶液中的活度系数很小,可能符合于我们的要求,因此研究了下列反应:CaO+C(石墨)=Ca(锡)+CO(气).以测定液态CaO-SiO_2和CaO-Al_2O_3-SiO_2渣中CaO的活度,在上式中符号下波纹线表示溶于渣中的组分,直线表示溶子金属中的组分,下同.对于CaO-Si0_2系,应用Gibbs-Duhem关系从CaO活度值算出了SiO_2的活度值,并根据一个统计力学模型讨论了活度曲线的形状.从CaO-Al_2O_3-SiO_2系的研究结果,可知在所研究的整个碱度范围內,渣中存在10%Al_2O_3都使CaO的活度增加;当Al_2O_3为20%时,则对CaO活度的影响视碱度不同而异.对Al_2O_3的这种行为,根据炉渣的离子结构理论提出了解释.

关键词:

MgO-CaO耐火材料性能研究进展

王宏联 , 崔庆阳 , 薛群虎 , 闫振华 , 宋鹏涛 , 田晓丽

耐火材料 doi:10.3969/j.issn.1001-1935.2010.01.018

介绍了MgO-CaO耐火材料的特性,总结了提高MgO-CaO耐火材料的抗水化性、烧结性、抗渣性、抗剥落性等的技术措施.提出了MgO-CaO耐火材料的发展方向,即:开发高CaO含量的MgO-CaO耐火材料;进一步开发不烧MgO-CaO耐火材料;开发水泥回转窑用MgO-CaO耐火材料.

关键词: MgO-CaO耐火材料 , 抗水化 , 应对措施

Investigations of the g factors of Fe+ in MgO and CaO

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The g factors of Fe+ in MgO and CaO are theoretically investigated by the perturbation formula of the g factor of a V ion in cubic octahedral symmetry based on the cluster approach. By considering the partial quenching of the spin-orbit coupling interaction and the effective Lande factor due to the dynamic Jahn-Teller effect (DJTE), the experimental g factors of the studied systems are reasonably interpreted. It can be suggested that the small g factors of the Fe+ centers in MgO and CaO can be likely attributed to the DJTE, rather than the covalency effect within the scheme of the static crystal-field model.

关键词: electron paramagnetic resonance;crystal- and ligand-field theory;Fe+;MgO;CaO;atomic screening constants;electron spin resonance;paramagnetic-resonance;orbit interaction;scf functions;crystals;spectra;oxide;co2+

CaO-SiO_2-Al_2O_3熔渣中CaO的活度

张子青 , 周继程 , 邹元燨 , 田彦文

金属学报

本文以Sn为溶剂金属,直接用“渣-金属”化学平衡法,在较大组成范围内测定了CaO-Si0_2-Al_2O_3三元熔渣中CaO的活度。成功地用图示推测法推测了较难直接获得实验结果的低CaO浓度范围内CaO的活度。应用本文实验结果和数据分析得到了该渣系中较全面的等CaO活度曲线图,并对Al_2O_3在该渣系中的酸碱性行为进行了探讨。

关键词:

真空冶炼用MgO-CaO坩埚的研制

刘彦海 , 段百泉 , 胡希东

耐火材料 doi:10.3969/j.issn.1001-1935.2007.04.012

为了降低真空冶炼用MgO坩埚因MgO的高温不稳定性对冶炼合金造成的影响,同时发挥CaO的脱硫作用,以w(MgO+CaO)>97%的MgO-CaO熟料为原料,在对MgO-CaO熟料进行水化试验和烧结试验研究的基础上,研制了MgO-CaO坩埚,并且与CaO坩埚一起对一种纯金属和同材质的高温合金进行了对比冶炼试验.结果表明:MgO-CaO熟料的抗水化性远高于石灰熟料的;在添加适当种类和数量的烧结助剂后,MgO-CaO熟料的可烧结性明显改善;MgO-CaO坩埚的冶炼效果达到甚至超过了CaO坩埚.

关键词: 真空冶炼 , 坩埚 , CaO , MgO-CaO

ZrO2(CaO)纳米粉体的性能与CaO含量的关系

梁丽萍 , 党淑娥 , 高荫本

硅酸盐通报 doi:10.3969/j.issn.1001-1625.2002.06.018

采用凝胶-超临界流体干燥技术合成不同CaO含量的稳定化ZrO2超微粉体,对粉体的织构性能和烧结性能进行研究.实验表明:粉体中CaO的浓度会显著影响其粒度、相组成及烧结性能,而且这种影响作用与传统粉体的不同.

关键词: CaO稳定化ZrO2 , 粒度 , 相组成 , 烧结

PE/CaO复合材料的流变行为

游瑞云 , 肖荔人 , 刘欣萍 , 林葱里 , 黄宝铨 , 许兢 , 陈宇 , 陈庆华

材料工程 doi:10.3969/j.issn.1001-4381.2010.06.002

通过熔融共混法制备CaO含量不同的PE/CaO复合材料,借助熔体流动速率仪和AR2000旋转流变仪,对PE/CaO复合材料熔体的流变行为进行研究.结果表明:PE/CaO复合材料的黏流活化能随CaO含量的增加先上升后逐渐下降;当CaO含量(质量分数,下同)≤20%时,复合材料的线性黏弹性与纯PE相近,零剪切黏度变大的幅度较小;当CaO含量≥25%时,复合材料的时间稳定性下降,零剪切黏度明显增大.

关键词: 聚乙烯 , 氧化钙 , 复合材料 , 流变行为

CaO-NaCl焙烧分解独居石的研究

吴文远 , 陈旭东 , 陈杰 , 孙树臣 , 涂赣峰

稀土 doi:10.3969/j.issn.1004-0277.2004.02.006

研究了630℃～870℃焙烧温度范围内,CaO、NaCl对独居石分解率影响的变化规律,得出了相应的回归方程,并且用该方程讨论了CaO、NaCl、焙烧温度对独居石分解率的影响.研究结果表明:独居石分解率随CaO、NaCl增加、焙烧温度的升高而增加.当CaO和NaCl加入量分别都为45%,焙烧温度为870℃时,独居石的分解率达到78.39%.

关键词: CaO-NaCl , 独居石 , 分解率