金属喷射成型过程单颗粒液滴的运动和传热研究

建立了金属喷射成型过程中单颗粒金属液滴的运动和传热数学模型，应用该模型对喷射成型过程中不同尺寸液滴的运动和传热过程进行了分析，确定了不同尺寸液滴的运动轨迹、温度变化及凝固情况．     

喷射成形液滴运动及传热的数值模拟

通过对喷射成形过程的分析,建立了喷射成形过程中金属液滴运动和传热的数学模型.利用该模型计算了喷射成形过程中雾化气体的速度、液滴速度、液滴温度、液滴的固相率等过程参量的变化过程.     

喷射成形静电作用下雾化过程的理论分析

静电雾化技术可以提高喷射成形雾化质量,但由于雾化过程涉及气液固三相流、流场和电场等多场联合作用等,给试验研究带来了诸多不便.为了深入了解静电作用对喷射成形中金属液射流破碎的雾化过程影响,从理论上分析了静电作用对喷射成形雾化中射流破碎长度、雾滴表面张力和雾化液滴粒径的影响.结果表明：随着静电电压的增加,射流破碎长度将缩小,雾化液滴直径减小;当电压升高到一定值时,破碎长度和雾滴直径趋于稳定.静电力降低了液滴的表面张力,使得雾化动力相对增加,从而有助于提高雾化质量.     

锡粉多级雾化研究

在Ｉ型多级雾化－快速凝固装置上首先研究了喷嘴液流直径对粉末平均粒度的影响，再用正交实验方法研究了其他主要工艺因数对纯锡粉多级雾效果的影响。结果表明，喷嘴液流直径的影响不很敏感和显著，而在喷嘴液流直径为一定值的条件下，旋转盘转速和过热温度对粉末平均粒度影响最大，喷射高度和过热温度对粉末形状参数和标准偏差有显著影响。     

激波与液滴作用的空气动力学现象的实验研究

在水平激波管中对激波与液滴的相互作用进行了实验研究.使用氮气作为高压驱动气体,进行了激波马赫数为1.1及1.25的实验,更换生成液滴的不锈钢针头获得了不同尺寸的液滴,用高速摄影仪详细记录了液滴从压缩变形到破碎雾化的过程.通过分析实验数据,探讨液滴位移及横向直径随时间的变化关系,液滴在激波作用之后会进行加速运动,随着液滴的不断变形,其横向直径先增大后减小,直至完全雾化.     

金属喷射成型过程沉积坯的生成及其传热过程研究

通过概率模拟的方法,建立了金属喷射成型过程中大量金属液滴的统计模型.应用该模型对喷射成型过程中钢液的喷射过程进行了研究,给出了在喷射过程中不同尺寸液滴的分布,以及不同液滴产生的位置、初速度分布.通过大量液滴的统计,确定出整个喷射过程液滴的产生、运动和传热情况,为进一步研究液滴在沉积面上的沉积情况提供前提和依据.     

金属喷射成型过程大量液滴的统计模型研究

通过概率模拟的方法,建立了金属喷射成型过程中大量金属液滴的统计模型.应用该模型对喷射成型过程中钢液的喷射过程进行了研究,给出了在喷射过程中不同尺寸液滴的分布,以及不同液滴产生的位置、初速度分布.通过大量液滴的统计,确定出整个喷射过程液滴的产生、运动情况,为进一步研究液滴在沉积面上的沉积情况提供前提和依据.     

球形TC4合金粉制造方法

在氩气保护环境下,利用等离子弧将TC4合金焊丝直接雾化,收集雾化冷却后的小颗粒。对其形貌、成分及物相组成、流动性等进行研究。结果表明,颗粒呈现规则且表面光滑的圆球状。粉体物相结构表现为α相,没有氧化相结构,体现了快速凝固特征。粉体平均粒度57.96μm,粒度分布曲线呈正态分布。等离子弧可以直接制造金属粉体,而不用预先将合金液化或粉碎。     

雾化喷涂过程中的液滴特性研究

研究高压静电雾化过程液滴特性,运用信息熵方法建立油液粒径分布模型,通过静电涂油雾化实验研究液滴粒径分布规律。结果发现,液滴粒径随电压变化而变化,静电电压升高,液滴粒径减小;电压不同,液滴粒径的分布状态不同,电压为65 kV时,液滴粒径较小且分布均匀。所得实验结果与理论模型吻合。     

液滴在高温气流中蒸发混合特性计算分析

针对选择性非催化还原(SNCR)过程中还原剂溶液在炉内的蒸发扩散问题,运用Fluent计算软件模拟液滴在高温气流中蒸发扩散过程.研究涉及到主要参数包括气流流速、气流温度、液滴喷射速度、液滴喷射量以及液滴雾化粒径因素,分析它们对液滴蒸发和扩散规律的影响.以液滴蒸发时间、距离﹑有效区域体积、投影面积为衡量指标,得到液滴蒸发规律.研究表明,气流温度、气流流速和液滴喷射速度的增大都可以加速液滴蒸发,其中气流温度的影响最大,液滴喷射速度次之,气流流速最小.液滴喷射量和液滴雾化粒径的增大都可以使蒸发时间延长.除气流流速外,其他4种变量增大都会使研究区域内混合状况变好.     

Nature of large （Ti, Nb）（C, N） particles precipitated during the solidification of Ti, Nb HSLA steel

To investigate the microsegregation phenomena and complex （Ti, Nb）（C, N） precipitation behavior during continuous casting, a unidirectional solidification unit was employed to simulate the solidification process. The samples of Ti, Nb-addition steels after unidirectional solidification were examined using field emission scanning electron microscope （FE-SEM） and electron probe X-ray microanalyzer （EPMA）. In such specimens, dendrite structure and mushy zone can be detected along the solidification direction. It shows that the addition of titanium, niobium to high-strength low-alloyed （HSLA） steel results in undesirable （Ti, Nb）（C, N） precipitation because of microsegregation. The effect of cooling rate on （Ti, Nb）（C, N） precipitation was investigated. The composition of large precipitates was determined using FE-SEM with EDS. Large （Ti, Nb）（C, N） precipitates could be divided into three kinds according to the composition and morphology. With the cooling rate increasing, Ti-rich （Ti, Nb）（C, N） precipitates are transformed to Nb-rich （Ti, Nb）（C, N） precipitates.     

Design of process parameters for direct squeeze casting

On the basis of the analysis of solidification interval and temperature distribution of components manufactured by the squeeze casting method,formulas for calculating the solidification interval and compaction pressure were deduced according to the principal request that the compaction pressure should be equal to or greater than the plastic deformation resistance of the forming component when solidification ended.The solidification interval was proven to be associated with many factors,such as weight of the component,specific heat of the alloy,latent heat,pouring temperature,component temperature at the end of solidification and heat-transfer coefficients.The compaction pressure was related to the strain rate,deformation temperature,and dimension of the de- forming component.The solidification interval and compaction pressure calculated by the formulas deduced in this article were adopted in the production of 45 steel bidirectional chapiter valves,and components with excellent performance were manufactured.     

基于CAE技术铝合金支架压铸工艺优化

基于CAE技术研究了铝合金汽车支架压铸件的凝固过程,对可能出现的铸造缺陷进行预测,获得了零件成型过程的温度场分布和凝固时间与温度的关系。在有无水冷的两套方案中选择不同部位节点,研究不同节点凝固过程中的温度变化规律。结果表明：没有增设水冷的方案中,铸件凝固顺序混乱,温度梯度分布不合理,铸件成形过程容易产生铸造缺陷;增设水冷设置的方案中,铸件各节点冷却速度得到提高,同时保持良好的凝固顺序,铸造缺陷显著下降。     

Ni_（78.6）Si_（21.4）合金的深过冷与凝固组织演化

深过冷技术研究是凝固科学中重要的研究领域之一.文中采用玻璃熔融净化与循环过热法使Ni78.6Si21.4合金获得了318K的过冷度,研究了其凝固组织随初始过冷度（ΔT）的演化规律,并对凝固组织中的亚稳相进行了分析.研究发现：当ΔT〈193K时,凝固组织为Ni3Si＋（Ni3Si＋α-Ni）非规则共晶;193K〈ΔT〈250K,凝固组织为α？Ni＋（Ni3Si＋α-Ni）非规则共晶;ΔT〉250K时,凝固组织为完全的非规则共晶;随过冷度的增加,过冷合金熔体中依次出现了亚稳相Ni31Si12相和Ni3Si2相.     

Effects of Suspension Casting on Solidification Process of GCr15 Steel Ingot

The mechanism of inoculation in the case of suspension casting process has been studied through solidification kinetics. The effect of suspension casting process on temperature field, solidification rate, temperature gap of crystallization, effective distribution coefficient of solute and nucleation frequency during solidification process in steel ingot were discussed on the base of experiments. It has been found that the suspension casting process can increase both cooling at and solidification rate of steel ingot, improve the temperature field and solute distribution, narrow the temperature gap of crystallication, and increase the nucleation frequency. Thus, the solidification time can be shorten, the solute can be well distributied, the shrinkage porosity can be reduced and the grain of crystallization can be fined.     

快凝制粉技术研究现状

金属粉末的生产是粉末冶金工业的基础,快凝制粉是现代金属粉末生产最重要的技术,分别从工艺原理,工艺,工艺适用范围,工艺特点和所得粉末特性等方面对国内外快速凝固制取金属粉末技术进行了综述,指出了主要的,有大规模工业生产前景的快凝制粉技术,对国内快凝制粉状况进行了全面介绍。     

拉坯速度对连铸大方坯凝固的影响

结合现场研究,利用显式有限差分法计算出不同工艺条件下的铸坯凝固情况;进行了拉坯速度对出结晶器坯壳厚度、铸坯表面温度、铸坯凝固终点位置和铸坯质量影响的模拟分析研究.模拟结果表明,拉速对铸坯表面温度和凝固终点的影响较大,随拉速的增大,表面温度升高,出结晶器坯壳厚度减薄,铸坯液相穴拉长.     

Fabrication of directional solidification components of nickel-base superalloys by laser metal forming

Straight plates, hollow columns, ear-like blade tips, twist plates with directional solidification microstructure made of Rene 95 superalloys were successfully fabricated on Nickel-base superalloy and DD3 substrates, respectively. The processing conditions for production of the parts with corresponding shapes were obtained. The fabrication precision was high and the components were compact. The solidification microstructure of the parts was analyzed by optical microscopy. The results show that the solidification microstructure is composed of columnar dendrites, by epitaxial growth onto the directional solidification substrates. The crystallography orientation of the parts was parallel to that of the substrates. The primary arm spacing was about 10μm, which is in the range of superfine dendrites, and the secondary arm was small or even degenerated. It is concluded that the laser metal forming technique provides a method to manufacture directional solidification components.     

Improving the solidification structure of commercially pure aluminium with electropulse acting on liquid metal

The effect of electropulse on the solidification structure of commercially pure aluminium was studied. The orthogonal array L9 was used to determine the effect of three process parameters of electropulse modification (EPM), which were pulse current intensity, pulse frequency, and treating time. For each factor, three levels were chosen to cover the experimental region. According to the ex-perimental results, the solidification structure of commercially pure aluminium was modified from large grains with columnar crystals to finer grains with equiaxed crystals, by allowing the electropulse to act on liquid aluminium. However, the solidification structures could be refined differently at different EPM parameters. Certain EPM parameters should be selected to get the optimum solidification structure. Among the three parameters, pulse frequency was the most important factor influencing the solidification structure, the secondary factor was current intensity, and treating time was the third one. The optimum parameters were the pulse frequency of 5 Hz, the current intensity of 68 A, and the treating time of 10 s.     

快速凝固条件下Cu-Cr合金的液相分解

采用快速凝固方法研究了Cu100-xCrx(x=2，25和35％)合金凝固行为．利用带有能谱(EDS)的扫描电子显微镜(SEM)分析了Cu—Cr合金的显微组织形貌和成分．实验结果证实，Cu—Cr合金在快速凝固过程中发生了液相分解，在较大的富Cr液相分解球中可观察到来自于二次相分解的、更细小的富Cu粒子．与Cu—Co和Cu-Fe液相分解组织不同，快速凝固Cu-Cr合金的大尺寸液相分解球不是由相互表面界限明确的、尺寸更小的液相分解球所组成，而是一个整体结构．