ELECTROMAGNETIC FIELD REMOVE INCLUSIONS FROM ALUMINUM MELT IN ELECTROMAGNETIC FIELD

Electromagnetic separation of non-metallic inclusions from Al-Si melt is studied by theoretical analysis and experiments on self-designed electromagnetic separation apparatus. Metallographs and LECO Image Analysis System were used to analyze the content of alumina in aluminum alloy before and after electromagnetic separation. It is seen that removal effciency increases with the increase of electromagnetic force (EMF) and diameter of inclusion particles while decreases with the increase of melt velocity and height of separator. All alumina particles with diamete of 14μm have been removed successfully from the melt.     

铝熔体中夹杂物形状与取向对其电磁分离的影响

采用有限元方法,对电磁场作用下铝熔体中任意形状与取向夹杂的受力进行数值计算。结果表明：不同形状与取向的夹杂均仅受到一个与熔体所受电磁力方向相反的斥力作用;电磁斥力的大小不仅与夹杂的形状有关,还受其取向的影响;当夹杂的形状奇异程度愈大时,取向对电磁斥力的影响也愈大;当夹杂在磁场方向的主轴长度较大,并且在电磁力方向的主轴长度较小时,夹杂所受电磁斥力不显著。     

电磁过滤钢液中非金属夹杂物的运动速度和去除效率的理论分析

电磁过滤原理是根据非金属夹杂物与熔体导电性的差异,在电磁场作用下非金属夹杂物与熔体的运动规律不同,使非金属夹杂物与熔体分离,经流体力学分析、采用柱塞流及轨线模型研究电磁过滤水平流动钢液中非金属夹杂物的运动速度和去除效率,结果表明,非金属夹杂物的去除效率随着熔体流速（u)和过滤器的高度（2h)的降低而增加;随着电磁力（f)、电磁力作用区长度（x)和非金属夹杂物的粒径（dp)的增加而增加,经分析表明,采用电磁过滤法可有效去除粒径小于10um的非金属夹杂物,该模型可用来设计过滤器的结构和确定电磁过滤工艺参数,为电磁去除钢液中的非金属夹杂物技术的工业应用提供理论基础。     

Effect of electromagnetic force on melt induced by traveling magnetic field

A new apparatus was designed to measure the electromagnetic force and a computational study of the traveling magnetic field(TMF)and its application to the Ga-In-Sn melt(with low melting point),then the forces on Al,Mg,and Li melt,were simulated. The result show that the electromagnetic force on the melt increases linearly with the increasing length of the melt in the TMF.The TMF-induced Lorentz force increases with increasing frequency,and then decreases.The maximum value is obtained when the current frequency is 160 Hz,over that frequency the force decreases rapidly.When the iron-core is activated,the force increases when the melt closes to the iron-core.The Lorentz forces have inversely-proportional relationships with the electrical resistivity,the dfx/dρdecreases and the dfy/dρincreases with the increasing electrical resistivity(df/dρis the slope of the Lorentz force profile).     

行波磁场连续净化铝合金液实验

采用行波磁场进行了电磁连续净化铝合金液实验,并采用电磁净化金属熔体的轨线模型,对实验中的夹杂物去除率进行了理论预测,结果表明,含夹杂的铝合金液连续液经电磁力作用段时,夹杂物被阻隔,形成电磁过滤效应,而夹杂物聚集区域夹杂物面积分数趋于某一常数,轨线模型预测与实验结果吻合良好。     

A study on elimination of alumina particles in molten aluminum using direct electromagnetic force

From the viewpoint of energy reduction, the recovery of metal scrap and its recycling have been rising as an important global subject. However, it is difficult to remove deleterious impurities, which have detrimental effects on the mechanical properties. In particular, it is difficult to eliminate nonmetallic inclusions such as alumina(Al₂O₃) in aluminum alloys when they are subject to recycling. In this study, an experiment on the elimination of the impurities in the melt by imposing electromagnetic force to molten aluminum was conducted. The principle behind these electromagnetic methods is that as the electromagnetic force induced in metal scarcely acts on non-metallic inclusions due to low electric conductivity, the non-metallic inclusions are moved to the direction opposite the electromagnetic force and can be separated from the melt. The prediction based on the theoretical analyses was confirmed through the visualization of the polystyrene particle motion in an NaCl aqueous solution. We also proposed optimum electromagnetic conditions such as current density, magnetic field intensity and particle size for eliminating the inclusion particles continuously found through numerical analysis and experiments.     

脉冲磁致振荡下纯铝凝固磁场与流场分布的数值模拟

脉冲磁致振荡可以细化金属晶粒,为了研究其作用机理,采用ANSYS有限元模拟软件对脉冲磁致振荡下纯铝凝固磁场与流场分布进行了数值模拟.模拟结果显示,由于电磁趋肤效应,线圈中脉冲电流只在熔体表面感应产生电磁力,且随时间出现指向内部的压力与指向外部的拉力交替变化,沿径向有指向熔体顶部与底部交替变化.交变电磁力可以振荡熔体表面率先析出的晶核而使之游离,增大熔体形核率.同时感应电磁力迫使熔体产生流动,会利于晶核的均匀分布与温度场、浓度场的均匀化.     

Effect of mould material on aluminum alloy ingot quality under low frequency electromagnetic casting

F or a semi-continuous aluminum casting process, it is essential to supply high quality aluminum alloy ingot without internal and outside defects. The use of electromagnetic fields to control the size and shape of grains has become one of the most promising methods [1-5] in many engineering applications and tends to be widespread in industries. The application of electromagnetic casting (EMC) technique for improving products quality has attracted a great deal of attention in recent years, and…     

静流式铝电解槽磁场仿真及设计

通过对槽内磁场、电流场的分析和研究,提出一种静流式铝电解槽的概念,采用阴极垂直出电的方式代替目前的水平出电方式,从而大幅度降低铝液层中的水平电流,大幅度削弱电磁力对槽内熔体的影响,进而减小铝液的流动和波动,将电磁影响削弱到最低程度以实现熔体界面高稳定性,并依此原理设计开发新型高效节能型铝电解试验槽。同时对母线配置进行设计,在最优化母线配置下,磁场数值仿真计算结果表明,该电解槽垂直磁场最大值为0.896 3 mT,平均值为0.360 2 mT,远低于同规格普通电解槽的垂直磁场,从而可获得电解槽超稳定运行条件,为大幅度降低极距,实现大幅度节能创造条件。     

Electromagnetic separation of primary iron-rich phases from aluminum-silicon melt

1　ＩＮＴＲＯＤＵＣＴＩＯＮＩｒｏｎｉｓｕｓｕａｌｌｙｃｏｎｓｉｄｅｒｅｄｔｏｂｅｈａｒｍｆｕｌｉｍｐｕｒｉｔｙｉｎａｌｕｍｉｎｕｍ .Ｔｈｅｎｅｅｄｌｅ ｌｉｋｅｏｒｍａｓｓｉｖｅｉｒｏｎ ｓｉｌｉｃｏｎｉｎｔｅｒ ｍｅｔａｌｌｉｃｃｏｍｐｏｕｎｄｓ ,ａｒｅｎｏｔｏｎｌｙｃｒａｃｋｏｒｉｇｉｎｓｂｕｔａｌｓｏｃｒａｃｋｇｒｏｗｔｈｐａｔｈｓｗｈｉｃｈｄｒａｍａｔｉｃａｌｌｙｉｎｆｌｕｅｎｃｅｔｈｅｓｔｒｅｎｇｔｈａｎｄｅｌｏｎｇａｔｉｏｎｏｆａｌｕｍｉｎｕｍａｌｌｏｙ .Ｔｈｅｓｅｈａｒｄａｎｄｂｒｉ…     

New model of body force in electromagnetic stirring gas tungsten-arc welding

1　ＩＮＴＲＯＤＵＣＴＩＯＮＥｌｅｃｔｒｏｍａｇｎｅｔｉｃｓｔｉｒｒｉｎｇ (ＥＭＳ)ｗｅｌｄｉｎｇｔｅｃｈ ｎｉｑｕｅｉｓｄｉｆｆｅｒｅｎｔｆｒｏｍｔｈｅｃｏｍｍｏｎａｒｃｗｅｌｄｉｎｇｔｅｃｈ ｎｉｑｕｅａｎｄｈａｓｔｈｅｆｏｌｌｏｗｉｎｇａｄｖａｎｔａｇｅｓ[1～ 3] :1)ｌｏｗｃｏｓｔｓｆｏｒｉｎｖｅｓｔｍｅｎｔｏｗｉｎｇｔｏｓｉｍｐｌｅａｄｄｉｔｉｏｎａｌｅｑｕｉｐ ｍｅｎｔ;2 )ｏｐｅｒａｔｉｏｎａｌｒｅｌｉａｂｉｌｉｔｙｗｈｉｃｈｔｈａｎｋｓｔｏｔｈｅｕｓｅｏｆｈｉｇｈ ｐｅｒｆｏｒｍａｎｃｅｃ…     

THEORETICAL INVESTIGATION ON BY-ONLY-CURRENT ELECTROMAGNETIC SEPARATION OF INCLUSION FROM MOLTEN METALS

The electromagnetic field under applied AC and DC current in round and rectangular pipe was systematically investigated, then a concept of "equivalent current density" was proposed for evaluating the inhomogeneous electromagnetic pinch force, and the mono-component removal efficiency and the overall removal efficiency of inclusion were formulated. It is founded that flat pipe is superior to round pipe for the electromagnetic removal of inclusion, and DC current can get a higher removal efficiency than A C current due to absence of skin phenomenon. Under usual condition, a removal efficiency of 52% for 10μm inclusion or more than 92% for 20μm inclusion can be achieved by imposing a current density of 3×106A/m2 in a flat pipe.     

Effect of electromagnetic parameters on melt flow and heat transfer of AZ80 Mg alloy during differential phase electromagnetic DC casting based on numerical simulation

Based on multi-physical field coupling numerical simulation method, magnetic field distribution, melt flow, and heat transfer behavior of a Φ300 mm AZ80 alloy billet during differential phase electromagnetic DC casting (DP-EMC) with different electromagnetic parameters were studied. The results demonstrate that the increase in current intensity only changes the magnitude but does not change the Lorentz force’s distribution characteristics. The maximum value of the Lorentz force increases linearly followed by an increase in current intensity. As the frequency increases, the Lorentz force’s r component remains constant, and the z component decreases slightly. The change in current intensity correlates with the melt oscillation and convection intensity positively, as well as the liquid sump temperature uniformity. It does not mean that the higher the electric current, the better the metallurgical quality of the billet. A lower frequency is beneficial to generate a more significant melt flow and velocity fluctuation, which is helpful to create a more uniform temperature field. Appropriate DP-EMC parameters for a Φ300 mm AZ80 Mg alloy are 10–20 Hz frequency and 80–100 A current intensity.

     

铝合金半固态浆料制备过程的电磁-流体数值模拟

利用ANSYS软件时旋转型电磁搅拌作用下铝舍金半固态浆料内的电磁场、不同温度下浆料内流场进行了数值模拟。分析了励磁电流强度和频率的变化对半固态浆料内的磁感应强度、电磁力及流动状态的影响。结果表明：在相同频率下，半固态浆料内的磁感应强度、电磁力的大小随电流强度的增加呈线性增加的关系；在相同电流强度下，磁感应强度是随着频率的增大而减小的，而电磁力是增大的，但数值变化不大。随浆料中固相体积分数的增加，使半固态浆料的温度降低．粘度增大，流动速度降低。     

影响铝熔体电磁净化效果因素的分析

从液态金属电磁净化技术的原理出发,在理论上分析了当夹杂物与金属熔体密度接近的情况下,可以利用两者之间的电性能与磁性能的差异来实现夹杂物的分离,达到金属熔体净化的效果。综述了影响电磁分离效率和效果的因素。表明在电磁净化过程中,通电时间越长、磁感应强度越大、管半径与集肤程度比值在1.5~2.0之间、分离管为异型管、夹杂颗粒越大且近于球形,分离效果越理想,分离效率越高。     

外加磁场下GMAW熔池电磁力的有限元计算

针对外加各种磁场作用下的GMAW堆焊过程,开发了基于电弧简化模型的熔池电磁力工程化有限元计算方法. 利用此方法,系统研究了无外加磁场、外加纵向磁场和横向磁场三种工况下熔池内电磁力的分布情况,并预测了电磁力对熔池对流的影响. 结果表明,焊接自有磁场驱动了熔池中心收缩下沉流;外加纵向磁场导致周向搅拌流,形成电磁搅拌细化晶粒;外加横向磁场可以驱动熔池流动演变为"单涡"对流状态,有利于熔池接纳熔滴减少飞溅. 基于模拟结果的预测与试验结果吻合,因此验证了所用计算方法的正确性.     

异相位电磁连铸的电磁场分析

采用ANSYS有限元软件对空心管异相位电磁连铸中电磁场、力场的分布进行了模拟．结果表明：异相位磁场作用下,铸管中磁感应强度高且分布均匀;壁厚中部的金属熔体受到沿径向的电磁推力,向外结晶器方向流动;石墨环附近的金属熔体和初凝壳受到电磁斥力的作用,可以避免“抱芯”,减少摩擦,抑制了偏析瘤的形成,进而提高了铸管表面质量．     

脉冲波形对金属熔体内部电磁场分布的影响

建立了金属熔体内部电磁场分布的3-D模型,运用Maxwell软件模拟了正弦波、方形波和三角波脉冲电流作用下熔体内部磁感应强度的分布情况。结果表明,脉冲波形对金属熔体内部电磁场的分布及金属凝固组织的细化效果有很重要的影响。相同脉冲电流峰值和脉宽时,方形波的脉冲电流在金属熔体内部产生的感应电磁场强度大于三角波和正弦波。     

电磁搅拌法制备半固态浆料过程中电磁场的数值模拟

建立了电磁搅拌法制备半固态金属浆料电磁场的计算模型,采用商用ANSYS软件对电磁场分布进行了数值模拟,分析了线圈和坩埚间的缝隙、坩埚材质、电流和频率对磁感应强度的影响规律,并进行了相应的试验验证.研究结果表明,电磁场模拟结果与试验结果具有较好的一致性,验证了计算模型与软件算法的可行性.在电磁力的作用下,铝合金熔体在水平方向上产生旋转运动,由于感应电流的集肤效应,合金熔体中的电磁力由外向内依次减小;磁感应强度随频率的增大而依次减小,随电流的增大而依次增大;在选用不锈钢坩埚,坩埚和线圈间缝隙为5 mm时可以使铝合金熔体获得的磁感应强度最大;在电流为50 A,频率为10 Hz时电磁搅拌法可以获得更加细小均匀的半固态组织.     

Numerical calculation and industrial measurements of metal pad velocities in Hall-Heroult cells

1　ＩＮＴＲＯＤＵＣＴＩＯＮＭａｇｎｅｔｏｈｙｄｒｏｄｙｎａｍｉｃｓ(ＭＨＤ )ｐｌａｙｓａｎｉｍｐｏｒｔａｎｔｒｏｌｅｉｎｃｅｌｌｐｅｒｆｏｒｍａｎｃｅ[1] .Ｉｎｒｅｃｅｎｔｙｅａｒｓ ,ｎｏｔｏｎｌｙｉｎｔｈｅｎｅｗｃｅｌｌｄｅｓｉｇｎｉｎｇｂｕｔａｌｓｏｉｎｉｎｃｒｅａｓｉｎｇａｍｐｅｒａｇｅｉｎｅｘｉｓｔｉｎｇｌｉｎｅｓ ,ｍｏｒｅａｔｔｅｎｔｉｏｎｓｈａｖｅｂｅｅｎｐａｉｄｏｎｔｈｅｓｔｕｄｙｏｆＭＨＤ[2 ] .Ｔｗｏａｐｐｒｏａｃｈｅｓｈａｖｅｂｅｅｎｕｓｅｄｆｏｒｄｅ ｔｅｒｍｉｎｉｎｇｔｈｅＭ…