浅析热风阀发展与失效问题

文章列举了高炉系统中热风阀的研究发展现状,同时运用数值分析方式,结合实际情况,对热风阀常见失效问题进行了归纳与分析,总结产生失效现象的主要原因。最终,提出了改进建议与未来研究方向。     

Relationship between rectification moment and angle of shield based on numerical simulation

The finite element method is used to simulate the rectification process of shield machine, to study the relationship between rectification moment and angle and to explore the influence laws of different soil parameters and buried depth on rectification moment. It is hoped that the reference value of rectification moment can be offered to operator, and theoretical foundation can be laid for future automatic rectification technology. The results show that the rectification moment and angle generally exhibit good linear behavior in clay layers with different soil parameters or buried depths, and then the concept of rectification coefficient, that is, the ratio of rectification angle to rectification moment, is proposed; different soil parameters and buried depths have different influences on rectification coefficient, in which elastic modulus has great influence but others have little influences; the simulations of rectification process are preformed in clay layers with different elastic modulus, and fitting results show that elastic modulus and rectification coefficient present the quadratic function relation.     

纯稀土纳米晶Gd块体材料的结构与磁性

采用放电等离子烧结技术（简称SPS技术）及热处理制备了全致密纯稀土纳米晶Gd块体材料，研究了材料的微结构和磁性。X衍射结果表明材料在烧结过程中形成了一定程度的c轴织构。TEM观察显示，烧结态纳米晶Gd的平均晶粒尺度在10nm左右；热处理后，平均晶粒尺寸达到100nm。PPMS测试发现与粗晶Gd相比，纳米晶Gd的居里温度以及饱和磁化强度均有所下降。说明Gd的纳米化对其磁性具有重要影响。     

热处理工艺对块体纳米晶Fe3B/Nd2Fe14B复合磁体性能的影响

采用放电等离子烧结技术(Spark Plasma Sintering,简称SPS技术)将快淬Nd4.5Fe77B18.5薄带制备成块状纳米晶复合磁体.着重研究了热处理工艺对磁体密度、微观结构和磁性能的影响.结果表明,通过直接烧结得到的磁体具有超细纳米晶结构,合适的热处理可以消除残余非晶,得到较好的晶体结构和磁性能.但过高的热处理温度和较长的保温时间的增大会造成晶粒长大,结果导致磁性能的恶化.在最佳热处理条件下得到的磁体的磁性能为Br=1.014T,JHc=237.21 kA/m,(BH)max=61.85 kJ/m3.     

NdH纳米助剂回收制备烧结钕铁硼永磁体的研究

采用NdH纳米掺杂的方法对废旧烧结钕铁硼磁体进行了回收制备。研究了不同NdH纳米粉掺杂量对再制造烧结钕铁硼磁性能的影响。随着NdH纳米粉末掺杂量的增多,烧结磁体矫顽力从926.54 kA/m增加到1 299.87 kA/m;剩磁首先相对稳定在1.296 T,在掺杂量2.0%(质量分数)后,剩磁逐渐下降。与原始磁体相比,2.0%(质量分数)NdH纳米粉掺杂磁体性能最佳,矫顽力回复97.5%,剩磁回复95.9%,磁能积回复89.7%。通过计算,掺杂3.0%(质量分数)NdH纳米粉后,再制造烧结磁体中富钕相体积分数从3.03%增加到5.70%,然而其晶粒尺寸从8.18μm增长至11.68μm。结合微观分析与磁性能,2.0%(质量分数)NdH纳米粉掺杂磁体性能最好。     

烧结钕铁硼永磁二次资源再利用技术进展

稀土是重要的战略性资源,在国防和民用高技术领域不可替代。我国长期作为全球稀土原料的主要提供者,面临着稀土储量下降、能源消耗过度和环境破坏严重等问题。而以烧结钕铁硼永磁的工业固废和城市矿产为代表的稀土二次资源量逐年增多,且富含稀土元素,成为我国乃至世界稀土的重要来源之一。因此,烧结钕铁硼永磁二次资源再利用技术备受关注。本文介绍了烧结钕铁硼永磁二次资源的形成过程及其特性,并介绍了现有的产业化回收技术和新技术的研究与发展。     

考虑空间位形力作用的微米软颗粒溶液微圆管流动规律

针对微米级软颗粒溶液在微小孔道流动不符合泊肃叶流动规律问题,考虑受固体管壁影响软颗粒形变产生的空间位形力作用,基于Navier-Stokes理论,推导软颗粒溶液在圆管中的流速分布及流量表达式,引入颗粒形变因子以表征空间位形力作用的影响;建立考虑空间位形力作用的圆管流动数学模型.由微尺度流动特征实验,得到软颗粒溶液微圆管流动规律,与泊肃叶流动对比,结果显示当管径小于颗粒直径时,相同压力梯度下考虑空间位形力作用的流速比泊肃叶流动拟合结果更接近于实验数据.通过数值计算分析发现,与泊肃叶流动下的速度分布和平均流量相比,当微圆管尺寸减小时,空间位形力作用随之增大,其更大程度上影响流体在微圆管内的流动规律;当颗粒呈非球形且最小投影面积相同时,偏离球形颗粒程度越大,空间位形力作用越大,因此空间位形力作用在微小孔道流动中不可忽略.      

水热法沉淀三价铁工艺条件对产物形态影响的研究

本文研究了水热法沉淀三价铁过程中体系初始三价铁浓度、初始pH对沉淀产物物相的影响。一定条件下,在三价铁浓度逐渐降低过程中,铁沉淀产物逐渐由碱式硫酸铁向三氧化二铁转变;同时,一定条件下pH逐渐提高过程也有类似的效果。研究结果表明,实际中可以通过控制适当的条件,利用三价铁溶解直接生产铁红产品。     

Crystallographic alignment and magnetic anisotropy in melt-spun Nd-Fe-B/α-Fe composite ribbons with different neodymium contents

Crystallographic alignment and magnetic anisotropy were studied for NdxFe94-xB6 (x=8,9,10,11) ribbons prepared via melt-spinning. Effect of Nd content and wheel speed on the crystal structure and magnetic properties of the ribbons was investigated. Both the free and wheel side of the ribbons could obtain strong c-axis crystal texture of Nd2Fe14B phase perpendicular to the ribbons surface at low wheel speed,but the texture weakened gradually with the increase of the wheel speed. Increase of Nd content led to better formation of crystal texture in the ribbons,indicating that the α-Fe phase might undermine the formation of crystal texture. Magnetic measurement results showed that the magnetic anisotropy of the ribbons exhibited corresponding behavior with the invariance of the c-axis crystal texture of Nd2Fe14B phase in the ribbons,and the coercivity of the ribbons rose with the increase of both Nd content and wheel speed during melt-spun process.