冷连轧机张力-厚度控制交互作用多变量模式

冷连轧机轧制过程为多输入———多输出过程 ,可采用多变量控制技术。本文以 4机架六辊HC冷连轧机为例 ,分析了冷连轧机张力和厚度控制间的交互作用以及该过程的分散控制模式。     

Characterization of copper layers produced by cold gas-dynamic spraying

The cold gas-dynamic spray method produces coatings or deposits by introducing solid feedstock particles into a supersonic gas stream developed through the use of a converging-diverging (de Laval) nozzle. The particles thus accelerated impact on a substrate surface and develop into a dense deposit through a process believed to be similar to cold compaction. The work reported here explores the internal nature and physical characteristics of copper deposits produced by the cold gas-dynamic spray method using two vastly different starting powders: in one case, a “spongy” copper obtained by a direct-reduction process, and in the second, a denser, more spheroidal particulate produced by gas atomization. Optical and electron microscopies (scanning electron microscopy [SEM] and transmission electron microscopy [TEM]) were used to observe details of microstructure in the feedstock particles and deposits. Young’s modulus and residual stress measurements for the deposits were obtained through mechanical means, and measurements of hardness and electrical conductivity are reported. The internal structure of the cold-spray deposit was influenced by the surface purity of the feedstock material.     

循环压载下缺口旁疲劳裂纹扩展

对承受循环压载的缺口试件的疲劳问题进行了试验和理论研究。结果表明，疲劳裂纹是在残余拉应力和循环压应力作用下萌生和扩展的，压塑性变形是裂纹萌生和扩展和扩展的必要条件。循环压载下仍存在着裂纹张开和裂纹闭合，其机理与拉伸循环下不同。以试验中采用的ＬＹ１２ＣＡ材料边缺口试件为例，提出了考虑裂纹闭合效应的扩展率计算模型，结果与试验吻合得较好。     

Si3 N4浸渍处理提高硬度的研究

用硅粉冷等静压成型和反应烧结氮化工艺制造的氮化硅样品不规则气孔且多大，硬度偏低。浸渍处理可以填充气孔，显著提高硬度和抗弯强度。     

冷轧辊回火工艺及残余应力的研究

研究了冷轧辊在低温回火中内部残余应力的变化规律,提出了更为合理的回火工艺制度.利用X射线分析和大截面试样的剥层法测定了冷轧辊在淬、回火后残余应力沿截面的分布.结果表明,采用机械剥层和电解剥层相结合的方法可以获得理想的表面状态,减小了测量误差.改进的冷轧辊低温回火时间将缩短80%90%.     

冷轧带钢残余应力及其对板形影响的研究

轧制过程中金属的不均匀变形导致了板带中残余应力的存在,残余应力的不均匀分布又是影响板形的根本原因。文章采用小孔应力释放法,对在不同张力条件下冷轧后带钢的残余应力进行测量;建立了四辊轧制过程弹塑性有限元分析模型,并利用该模型对残余应力的分布进行数值模拟,研究了张力对残余应力分布的影响以及残余应力与板形的关系。该研究对制定与完善板带轧制规程、控制板形质量具有重要意义。     

冷喷涂技术

冷喷涂技术是近年来发展迅速的工业表面喷涂新技术。本文介绍了冷喷涂技术的原理、系统构成与冷喷涂的特点,以及影响冷喷涂主要工艺参数、粒子沉积行为与涂层性能等研究现状。并结合国内外的发展现状对冷喷涂技术的应用前景进行了展望。     

高强铝合金焊接接头无析出物区的形成机理

采用电弧焊对20 mm厚的2519-T87高强铝合金进行表面堆焊,观察了部分熔化区出现的无析出物区(PFZ)的组织特征,并对该区域的形成机理进行了研究.结果表明:无析出物区的形成主要是晶界液化层迁移所导致的,迁移的驱动力为相干应变能,焊缝收缩引起前,后晶粒的应变能差以及晶界曲率引起的界面能差.焊接热输入对无析出物区的形成有一定影响,随着焊接热输入的增加,无析出物区的宽度亦增加.该区的存在使部分熔化区在拉伸和冲击过程中易于断裂,且断裂方式为沿晶断裂.     

Study on shape factor of the fusion-solidification zone of electron beam weld

The concept of shape factors of the fusion-solidification zone is proposed to describe the weld cross section geometry. According to these shape factors, the electron beam weld fusion-solidification zone is divided into four typical shapes and the classification criterion for these typical shapes is suggested. An integrated parameter n, combining the line power density of electron beam and material thermal properties is proposed to describe the relative power input, and another integrated parameter n2 combing the accelerating voltage and focusing current is proposed to reflect the power distribution in the keyhole. A series of new expressions, which can reflect the influence of focusing current, accelerating voltage, beam current, and material thermal properties, are developed to predict the fusion-solidification zone shape based on experimental results nonlinear fitting of n1 and n2.     

钛合金冷坩埚连续熔铸过程定向凝固

水冷铜坩埚存在很强的侧向散热,而定向凝固则必须保证单向热流,分别从电磁力、温度场及传热3方面来分析冷坩埚定向凝固的可行性.结果表明:在三相点焦耳热最大,感应焦耳热弥补了侧向散热,保证在下驼峰与坩埚接触点Z0附近区域等温线近乎平直,能够利用冷坩埚实现钛合金的定向生长.增大电磁压力,提高熔体过热度,可以减小坩埚壁的侧向散热,有利于冷坩埚实现定向凝固.