Effect of Zn Concentration on Microstructural,Optical,and Hyperfine Properties of Nanocrystalline a-Fe_2O_3

Efforts have been made to prepare nanocomposites of a-Fe2O3-ZnO by wet chemical route with varying concentrations of the precursors.The microstructural properties of the samples are investigated by powder X-ray diffractometry(PXRD) and Transmission electron microscopy.Initial concentration of Zn ions(up to 20 at%) leads to the formation of nanocomposites of a-Fe2O3 and ZnO.Evolution of ZnFe2O4 phase is detected by the substitution of higher concentration of Zn2?(30 at%) in the sample.The average size of the nanoparticles remains in the range of 22–27 nm as obtained from XRD data.The results obtained from electron microscopic studies are also close to these values.Photoluminescence measurement shows the excitonic peak of ZnO around 390 nm which gets strengthened with Zn addition.FTIR spectra show the metal–oxygen band below 700 cm-1.Room temperature Mssbauer studies of the samples show the transition of iron oxide form antiferromagnetic state to paramagnetic state with increasing concentration of Zn2?.Sharp quenching of hyperfine field with Zn concentration is observed as the Hintvalue reduced to zero from 51 T.     

基于子模型法的混凝土面板堆石坝应力变形数值分析

采用非线性有限单元法,并基于邓肯-张(E-B)非线性本构模型,考虑面板堆石坝填筑施工与蓄水过程,利用中点增量法对苗家坝面板堆石坝进行了三维有限元数值仿真分析,得到了坝体施工期和蓄水期坝体的应力变形分布规律,从坝体结构意义上判断,堆石坝体工作是可靠的;同时,为了获得面板及其接缝应力变形更为精确可靠的结果,采用发展的三维子模型方法,而面板与垫层区之间的特殊边界用耦合的薄层单元进行模拟.工程算例的计算结果表明:面板应力和变形规律正常,较大拉应力分布范围局限在铺盖保护区以内,面板竖缝和周边缝变形值不大,面板的安全性是比较有保障的.同时,进一步证明了用耦合的薄层单元模型模拟接触面的子模型法在面板应力变形计算中具有一定的可行性和可靠性.     

Numerical and experimental analysis of quenching process for cam manufacturing

In order to obtain satisfactory mechanical properties for the cam used in high-power ship diesel engines, a new quenching technology was proposed by designing a two-stage quenching process with an alkaline bath as the quenching medium. To demonstrate the effectiveness of the proposed new quenching technology, both numerical analysis and experimental study were performed. The new quenching technology was analyzed using finite element method. The combined effects of the temperature, stress and microstructure fields were investigated considering nonlinear material properties. Finally, an experimental study was performed to verify the effectiveness of the proposed new quenching technology. The numerical results show that internal stress is affected by both thermal stress and transformation stress. In addition, the direction of the internal stress is changed several times due to thermal interaction and microstructure evolution during the quenching process. The experimental results show that the proposed new quenching technology significantly improves the mechanical properties and microstructures of the cam. The tensile strength, the impact resistance and the hardness value of the cam by the proposed new quenching technology are improved by 4.3%, 8.9% and 3.5% compared with those by the traditional quenching technology. Moreover, the residual stress and cam shape deformation are reduced by 40.0% and 48.9% respectively for the cam manufactured by the new quenching technology.     

高钛高炉渣碎石用做砼骨料的研究

攀钢高炉渣TiO2含量15%以上，与普通高炉渣的组成结构有较大差异，高钛高炉渣的性质研究及其用于砼的试验说明：高钛高炉渣结构稳定，其碎石用做砼骨料与普通碎石相比，抗压强度及劈拉强度稍高于后者。此外，其运用实例也说明了高钛高炉渣砼的稳定性。开发利用高钛高炉渣对环境保护，延长攀钢渣场使用年限具有重要意义。     

提高热轧板卷终轧温度的研究

根据攀钢热轧生产工艺流程 ,建立了带钢轧制过程的数学模型。该模型计算值与实测值基本吻合 ,温度偏差≤± 15℃。利用该模型定量分析了轧制速度、轧制节奏、轧制道次、加热温度等工艺参数对热轧板卷终轧温度的影响 ,在此基础上 ,提出了提高热轧板卷终轧温度的技术措施。经现场大生产实际应用 ,可以满足冷轧冲压系列钢板尤其是超低碳IF钢对热轧高温终轧的要求     

应变分析方法在金属薄板拉深成形中的应用

用应变分析方法测量和分析接深试验过程中拉深杯件各个区域的应变分布情况和应变变化历史,还分析了典型实物拉深零件JD90型摩托车油箱的应变分布特点,最后提出了确定接深成形零件危险部位的方法。     

含钒熟料间歇式浸出工艺研究

介绍了攀钢转炉钒渣焙烧熟料间歇式浸出生产Ｖ２Ｏ３的工艺,对影响钒浸出率的温度,浸泡时间,浸、洗次数进行了研究。工业生产表明：浸洗后残渣中ＳＶ降到０．１％以下,浸出液含钒浓度达到下步工序的要求。     

稀土在钒微合金化热轧钢板中的作用

通过在钒微合金化热轧钢板中加入稀土与不添加稀土的对比试验,结果表明：稀土处理具有净化钢质、变质夹杂的作用,有利于提高钢板的的成形性能;同时,稀土在钢中还具有一定的微合金化作用及抑制钢板时效的作用。