铝熔体偏置旋转喷吹净化的水模拟研究

采用水模拟方法,在不同的搅拌方式、转子旋转速度和进气量条件下,对铝熔体旋转喷吹净化过程的流场进行了分析。结果表明,与中心搅拌相比,偏置搅拌能有效消除液面漩涡,细化熔体中的气泡,改善气泡分布,防止气泡的偏聚。     

2024铝合金挤压棒材表面气泡形成机理研究

通过对2024铝合金挤压棒材表面气泡低倍组织、显微组织的分析,得出的结论是:表面气泡是由于气体析出形成的气体通透性气泡。解决办法是要对熔铸精炼过程氢含量、热处理过程中环境和工艺、挤压过程中气体带入进行工艺控制。这能为生产中减少和避免表面气泡提供参考。     

气泡对纯铝微弧氧化放电特性的影响

气泡可以被视为一种特殊的微弧氧化电解液添加剂。研究了微弧氧化过程中外来气泡及微弧氧化过程本身产生的气泡对放电特性的影响。结果表明,在微弧氧化过程中通入外气体会对放电过程产生一定影响。在恒压模式下,通入气体量较少时,对微弧氧化放电特性没有明显影响;当通入气体量较大时,会造成电解液导电通路变窄,进而系统阻抗增加,电流下降。通入气体种类对微弧氧化放电特性影响较小。微弧氧化过程本身产生的气泡对微弧氧化放电特性并不会产生影响,原因在于该过程产生的气体量较少,而且微弧氧化放电剧烈,电流主要沿放电通道流过,在该通道气泡几乎没有遮挡作用。     

铝及铝合金熔液处理技术（2）

4.SNIF净化装置 SNIF即Spinning Nozzle Inert Flotation,是旋转喷气浮选净化方法.其机理主要是动态的熔液用惰性气体浮选的原理.该装置的核心是旋转喷嘴,其作用是把惰性气体喷成极微细的气泡,并使之均匀地分布于整个熔液中,强烈地搅拌熔液并形成定向液流.喷嘴是用石墨制成的,浸在铝熔液中,用高压空气冷却.惰性气体是从喷嘴出来,由于旋转叶轮的碰撞和剪切作用,形成极细的气泡,垂直下落的金属流使气泡均匀分散.     

铝熔体旋转喷吹净化过程的模拟分析

采用水模拟和计算机数值模拟方法,对不同铝熔体旋转喷吹精炼方式的流场进行分析。结果表明,相对于中心精炼,偏置精炼能够有效抑制熔池内和液面漩涡的产生,得到的气泡分布更好,气泡在熔体内停留的时间更长,精炼效果更好。     

精炼处理对Al-Si-Mg合金熔体中TiB2粒子的影响

加入Al-5Ti-1B中间合金的Al-Si-Mg合金熔体,经N2气精炼处理后试样的晶粒尺寸较精炼处理前明显粗化,即精炼处理显著削弱了Al-5Ti-1B中间合金对Al-Si-Mg合金的细化效果。分析认为,精炼过程中一部分TiB2粒子及其聚集团极易被N2气泡捕获并游离出熔体,使异质形核衬底数目大幅减少。针对精炼对细化效果的不利影响,提出了两种解决方案,即采用Al-5Ti-0.6B-0.2C中间合金或先精炼后添加细化剂的操作工艺。     

机械搅拌的气孔缺陷形成机制

采用混合多相模型研究在机械搅拌过程中气孔缺陷的形成机制。研究表明,搅拌器附加的外力形成的负压,是卷入气体的主要因素;内负压区域主要在搅拌桨上方区域和桨叶附近区域,形成气孔缺陷。搅拌速度和搅拌时间影响气体在熔液中的分散,随着搅拌速度和搅拌时间逐渐增加,卷入的气体逐渐增加,且从集中区域向四周少量扩散。     

再生铝熔体旋转喷吹净化水模拟的研究

采用水模拟方法,从转子旋转速度、进气量等方面对铝熔体旋转喷吹净化过程的流场进行分析。结果表明:高转速能够获得较小的气泡和较好的气泡分布,但其值过高容易产生漩涡。在低转速下精炼,进气量的增大会产生气泡合并现象。     

旋转喷吹水模拟试验中的气泡形态研究

考察了水模拟试验过程中气液两相流的运动情况。对试验过程中气泡的破碎、扩散及合并情况进行了分析,指出气泡破碎是由液体的涡旋作用造成的,同时分析了气泡破碎的条件;气泡的扩散是搅拌机构和气泡浮力共同作用的结果;而气泡合并多发生在箱体内远离喷头的区域,并对不同尺寸气泡的合并情况进行了分析。     

铁液KR脱硫中后期搅拌桨转速研究

分析了铁液KR脱硫过程中脱硫剂在铁液中运动的主要过程,根据不同的过程推导了为保持与标准搅拌桨等效的铁液动力学条件中后期搅拌桨需要的理论转速,研究了搅拌转速对铁液液面边缘上升高度和中心最低点高度的影响。采用CFD软件分别对包含标准搅拌桨和中后期搅拌桨的KR脱硫模型进行数值模拟,研究了搅拌转速与脱硫剂在铁液中分散之间的关系,验证了中后期搅拌桨理论转速的合理性。     

铝熔体旋转喷吹净化动态水模拟试验研究

通过动态水模拟试验考察了喷头转速、气体流量和喷头浸入液体深度三个因素与气泡尺寸的关系,利用二次回归正交试验方法设计试验过程。试验结果表明,可以观察到气泡床的偏移,在特定的容积内喷头转速对气泡尺寸的影响最大,其次是气体流量,而喷头浸入深度对气泡尺寸影响较小。在现有的模拟试验条件下,当喷头转速215 r/min、气体流量2.94 m3/h、喷头浸入深度551 mm时,可以获得最理想的气泡尺寸。用相应设备处理铝熔体时,对铝熔体的含氢量进行测定。结果表明,在适宜的结构空间内,大叶轮、低转速的合理工艺组合可以获得较理想的除气效果。     

Physical modeling of gas induced bath flow in drained aluminum reduction cell

A room temperature physical model was used to study the bubble behavior and gas induced bath circulation in a drained aluminum reduction cell. By passing compressed argon through the penetrated Plexiglas box bottom plate immersed in water, gas evolution at the anode bottom surface was simulated. Bubble behavior and liquid flow field were studied and analysis was presented. Bath secondary recirculation was observed in the interpolar gap not the net rising flow as expected. Liquid driven by the bubbles forms small vortices along the interpolar gap with small mean and turbulent velocities and accordingly poor mass transfer. Secondary recirculation also exists between the slot and interpolar gap, part of the flow in the interpolar gap go to the slot with the bubbles and fluid at the bottom of the slot enters the interpolar gap directly without going to the center channel. The existence of the fluid secondary recirculation is very unfavorable to the alumina dissolution and dispersion. Increasing the anode tilt or gas flow rate, or decreasing the anode-cathode distance can make the secondary recirculation in the interpolar gap weak, however, will intensify the secondary recirculation between the slot and interpolar gap.     

A Nonlinear Shallow-Water Model Combined with Gas Bubble Effect for Melt Flows and Interface Instability in Aluminum Reduction Cells

A nonlinear shallow-water model combined with the effect of anode gas bubbles was derived for the melt flows and interface instability in aluminum reduction cells. Both the electromagnetic forces and the drag forces between the bath and gas bubbles, as the main driven forces for the melt flows, were taken into account in this model. A comparative numerical study was carried out using both the model considering the bubble and the model without considering the bubble. The results show the effect of the bubble cannot be neglected in a fluid dynamics analysis for the aluminum reduction cell. The bath flow, induced by the motion of bubbles, presents a series of small eddies rather than large eddies as the metal flow pattern shows. The horizontal drag forces between the bath and the bubbles in the bath layer enlarge the deformation of the metal–bath interface, to some extent, but have a positive influence on stabilizing the metal–bath interface perturbations.     

富氧底吹熔炼炉内气液两相流动的数值模拟

以某公司的富氧底吹熔池熔炼炉为原型,运用数值模拟的方法对炉内氧气铜锍两相流动进行三维瞬态模拟,研究炉内气泡主要参数、气含率分布规律、氧枪出口附近压力变化以及液面波动情况。并借助于高速摄像仪设备,对水模型实验中气泡形成、合并、变形及破碎过程进行研究,所得结果与模拟结果进行比较。结果表明:所建立的数学模型是合理的。氧气铜锍两相流动模拟结果表明,炉内气泡形成时间为0.12~0.25 s,生成频率为4~5 Hz,其短轴大小集中在3.5d~6.5d(d为氧枪直径尺寸);气泡停留时间为0.2~0.4 s,其在熔池内的平均上浮速度约为4 m/s;7°和22°氧枪出口气泡后座现象出现的平均频率分别为5 Hz和7 Hz,作用时间为0.06 s;高效反应区存在于熔池上部区域;气相搅动液相所形成的表面重力波在沉淀区传播的过程中,波幅衰减很快,当波传播到出渣口附近时,液面趋于静止。     

Ar气泡在连铸坯固/液界面处运动行为的物理模拟研究

针对连铸过程中水口吹Ar工艺导致的铸坯缺陷,利用Cu质水冷插针进行物理模拟实验,研究了气泡在连铸坯固/液界面处的运动行为.通过观察气泡在固/液界面的运动行为,研究气泡被铸坯捕获机理.同时,对现场铸坯进行了取样分析,发现弯月面处生长的枝晶是气泡被凝固坯壳捕获的一个重要因素,进而提出生产中采用水口电磁制动和结晶器窄面处电磁搅拌的方法来改善铸坯质量,减少气泡凝入铸坯.     

铝液微气泡精炼的模拟试验研究

利用气泡计测量的方法研究了熔池内气泡数量、大小和分布及其影响因素，对气液两相区宏观和微观结构进行了研究。测定了在不同喷枪转速和供气量条件下的气泡直径和气体容量。结果表明，气泡频率和含气率在喷头附近分布很高，在其它部位分布是均匀的。在一定供气量条件下，气泡直径随喷枪转速增加而减小。     

相界面逸出惰性气泡时相间传质

本文针对液-液两相接触时的传质过程,以流体动力学理论及相间传质的渗透理论为基础,根据界面上惰性气泡逸出界面时流体流动及传质过程的特征,导出了气泡促进的相间传质系数的数学关系式。该关系式表明,流体中传质速率不仅与逸出气泡的体积速度的平方根成正比,同时与气泡大小、界面上气泡分布密度等参数有关。该关系式能较好地描述文献中的实验数据。     

Rotary impeller refinement of 7075Al alloy

The effects of four parameters, gas flow, rotational speed, refining time, and stewing time, on the rotary impeller refinement of 7075 Al were studied. The effects of C2Cl6refining, rotary impeller refuting, and composite refining of 7075 AI alloy were compared with each other. The results showed that the greatest impact parameter of rotary impeller refinement was rotational speed, followed by gas flow, refining time, and stewing time. The optimum purification parameters obtained by orthogonal analysis were as follows: rotor speed of 400 r/min, inert gas flow of 0.4 mL/h, refining time of 15 min, and stewing time of 6 min. The best degassing effect can be obtained by the composite refuting of C2Cl6 and rotary impeller. The degassing rate of C2Cl6 rotary impeller, and composite refining was 34.5%, 69.2%, and 78%, respectively. The mechanical properties of the specimen refined by rotary impeller were higher than those by C2C16 refining, but lower than those by composite refining.     

吹头旋转方式影响铝液精炼效果的水模拟试验

采用水模拟的方法对铝液旋转吹气精炼工艺参数进行了试验研究，模拟分析了旋转方式对两种典型吹头气泡分布及液体表面状态的影响，以及阻流板浸入深度对侧叶片式吹头气泡分布及液体表面状态的影响。将模拟结果应用于生产现场试验表明，吹头正反转方式比吹头单向转方式对铝液的精炼效果更理想。     

Cold model on bubble growth and detachment in bottom blowing process

The bubble growth and detachment behavior in the bottom blowing process were investigated. Four multi-hole nozzle configurations with different opening ratios were assessed experimentally using high-speed photography and digital image processing. For these configurations, the experiments reveal that the bubble growth consists of a petal-like stage, an expansion stage and a detachment stage. The petal-like shape is qualitatively described through the captured images, while the non-spherical bubbles are analyzed by the aspect ratio. The bubble size at the detachment is quantified by the maximum caliper distance and the bubble equivalent diameter. Considering the dependence on the opening ratio, different prediction models for the ratio of maximum caliper distance to hydraulic diameter of the nozzle outlet and the dimensionless bubble diameter are established. The comparative analysis results show that the proposed prediction model can accurately predict the bubble detachment size under the condition of multi-hole nozzles.