Burner effects on melting process of regenerative aluminum melting furnace

According to the features of melting process of regenerative aluminum melting furnaces, a three-dimensional mathematical model with user-developed melting model, burner reversing and burning capacity model was established. The numerical simulation of melting process of a regenerative aluminum melting furnace was presented using hybrid programming method of FLUENT UDF and FLUENT scheme based on the heat balance test. Burner effects on melting process of aluminum melting furnaces were investigated by taking optimization regulations into account. The change rules of melting time on influence factors are achieved. Melting time decreases with swirl number, vertical angle of burner, air preheated temperature or natural gas flow; melting time firstly decreases with horizontal angle between burners or air-fuel ratio, then increases; melting time increases with the height of burner.

Application and study in aluminum melt degassing technologies

The classification, characteristics and current situation of aluminum melt hydrogen-removal methods and technologies have been summarized. The latest studies and research results of aluminum melt degassing technology have been summed up. The tendency and prospect of aluminum degassing technology was discussed.

Heredity of Aluminum Melt Caused by Electric Pulse Modification (Ⅰ)

The heredity of aluminum melt under the action of pulse electric field was investigated by means of the remelt experiment. A new hereditary criterion under this condition was proposed; in the meantime, the differential transferability of genetic carrier in activated melt among filial generations was validated with the aid of DSC.

Molecular mechanics and dynamics simulation of hydrogen diffusion in aluminum melt

The main impurities in aluminum melt are hydrogen and Al_2O_3,which can deteriorate melt quality and materials performance.However,the diffusion process of H atoms in aluminum melt and the interactions among Al atoms,Al_2O_3 and hydrogen have been studied rarely.Molecular mechanics and dynamics simulations are employed to study the diffusion behaviors of different types of hydrogen,such as free H atoms,H atoms in H_2 and H^+ions in H_2O using COMPASS force field.Correspondingly,force field types h,h1h and h1o are used to describe different types of hydrogen which are labeled as H_h,H_(h1h) and H_(h1o).The results show that the adsorption areas are maximum for H_(h1o),followed by H_(h1h) and H_h.The diffusion ability of H_(h1o) is the strongest whereas H_h is hard to diffuse in aluminum melt because of the differences in radius and potential well depth of various types of hydrogen.Al_2O_3 cluster makes the Al atoms array disordered,creating the energy conditions for hydrogen diffusion in aluminum melt.Al_2O_3 improves the diffusion of H_h and H_(h1o),and constrains H_(h1h) which accumulates around it and forms gas porosities in aluminum.H_(h1o) is the most dispersive in aluminum melt,moreover,the distance of Al-H_(h1o) is shorter than that of Al-H_(h1h),both of which are detrimental to the removal of H_(h1o).The simulation results indicate that the gas porosities can be eliminated by the removal of Al_2O_3 inclusions,and the dispersive hydrogen can be removed by adsorption function of gas bubbles or molten fluxes.

Multiple-response optimization for melting process of aluminum melting furnace based on response surface methodology with desirability function

To reduce the fuel consumption and emissions and also enhance the molten aluminum quality, a mathematical model with user-developed melting model and burning capacity model, were established according to the features of melting process of regenerative aluminum melting furnaces. Based on validating results by heat balance test for an aluminum melting furnace, CFD （computational fluid dynamics） technique, in association with statistical experimental design were used to optimize the melting process of the aluminum melting furnace. Four important factors influencing the melting time, such as horizontal angle between burners, height-to-radius ratio, natural gas mass flow and air preheated temperature, were identified by PLACKETT-BURMAN design. A steepest descent method was undertaken to determine the optimal regions of these factors. Response surface methodology with BOX-BEHNKEN design was adopted to further investigate the mutual interactions between these variables on RSD （relative standard deviation） of aluminum temperature, RSD of furnace temperature and melting time. Multiple-response optimization by desirability function approach was used to determine the optimum melting process parameters. The results indicate that the interaction between the height-to-radius ratio and horizontal angle between burners affects the response variables significantly. The predicted results show that the minimum RSD of aluminum temperature （12.13%）, RSD of furnace temperature （18.50%） and melting time （3.9 h） could be obtained under the optimum conditions of horizontal angle between burners as 64°, height-to-radius ratio as 0.3, natural gas mass flow as 599 m3/h, and air preheated temperature as 639 ℃. These predicted values were further verified by validation experiments. The excellent correlation between the predicted and experimental values confirms the validity and practicability of this statistical optimum strategy.

Current Status and Application of Ceramic Foam Filter for Aluminum Melt

The importance of purification for aluminum and aluminum alloy casting was outlined. By comparing ceramic foam filters （CFF） in China and overseas, the existing problems and challenges of China＇ s CFF for aluminum were given. Measures to improve the performance of CFF were put forward based on material, preparation process, utility evaluation, etc.

Hydrogen Diffusion in Aluminum Melts: An ab initio Molecular Dynamics Study

The diffusion process of hydrogen in aluminum melts was investigated by molecular dynamics simulation. The pair correlation function, first peak position, and coordination number was calculated and differences in the structural properties among Al-H, Cl-H, and Al-Cl pair were examined. The mechanism of chlorine on improving hydrogen diffusion was discussed. From an ab initio molecular dynamics calculations, the diffusivity of hydrogen in liquid aluminum as D（T）=（0.118×10-4 m2/s）exp（-0.316 eV/kT） is obtained, which is in good agreement with the experimental data. Correspondingly the diffusivity with presence of chlorine is promoted as D（T）=（0.09×10-4 m2/s）exp（-0.251 eV/kT）. It can be concluded that the diffusion of hydrogen in aluminum melts can be enhanced in the presence of chlorine.

Dynamic investigation of the finite dissolution of silicon particles in aluminum melt with a lower dissolution limit

The finite dissolution model of silicon particles in the aluminum melt is built and calculated by the finite difference method, and the lower dissolution limit of silicon particles in the aluminum melt is proposed and verified by experiments, which could be the origin of microinhomogeneity in aluminum-silicon melts. When the effects of curvature and interface reaction on dissolution are not considered; the dissolution rate first decreases and later increases with time. When the effects of curvature and interface reaction on dissolution are considered, the dissolution rate first decreases and later increases when the interface reaction coefficient （k） is larger than 10 1, and the dissolution rate first decreases and later tends to be constant when k is smaller than 10-3. The dissolution is controlled by both diffusion and interface reaction when k is larger than 10-3, while the dissolution is controlled only by the interface reaction when k is smaller than 10-4.

REMOVE INCLUSIONS FROM ALUMINUM MELT INELECTROMAGNETIC 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.

Continuous electromagnetic separation of inclusion from aluminum melt using alternating current

A novel scheme about the continuous electromagnetic purification of aluminum melt was put forward based on the utilization of a square separation pipe and a 50 Hz alternating current to produce electromagnetic force. It is experimentally found that with electrical current of 400 A/cm2, it takes only 10 s to remove 95% inclusion from aluminum melt. Comprehensive numerical simulations were carried out to investigate the dynamics mechanisms behind the process. The results show that the removal of inclusion is attributed to the cooperative effects of electromagnetic buoyancy and the secondary flow induced by the rotational electromagnetic force, and the removal efficient increases with the size of inclusion and the electrical current imposed. Theoretical predictions on the distribution and removal efficiency of inclusion were supported by the experiments.

Separation of inclusions from aluminum melt using alternating electromagnetic field

Effects of processing variables such as frequency of imposed magnetic field, imposed magnetic flux density, processing time, diameter of inclusions, and value of r 1/δ on the electromagnetic separating(EMS) removal efficiency were analyzed theoretically. The higher the frequency, the wider the range of r 1/δ will be. Removal efficiency reaches the maximum while r 1/δ ranges from 1.5 to 2. And the experimental results on aluminum melt show that higher frequency and magnetic flux density make for higher removal efficiency, matching well with the theoretical results. When f is 15.6 kHz, B e is 0.1 T , and imposed time is 10 s, more than 80% inclusion particles with 6 μm diameter can be removed.

Numerical Simulation of Magnetic Field Distribution in Aluminum Melting Furnace With Electromagnetic Stirring

In metallurgical processing,effective and reliable electromagnetic stirring of the melt is one of the prerequisites for higher productivity and improved process performance.Reasonable structure and electrical parameters of the stirrer are greatly significant on improving and enhancing the stirring quality.In this paper,ANSYS software is used to research the effect of stirrer parameters on magnetic field distribution in aluminum melting furnace.The results show that magnetic flux density distributes as two humps at the direction(X)of metal length.Magnetic flux density distributes as a hump at the direction(Z)of metal width,reaches its maximum at the pool center and decays gradually toward the edge.It is also demonstrated that magnetic flux density increases by 2.65mT,as kilo-ampere-turns increase by 2.The center distance between two coils changes the distribution of magnetic flux density rather than its magnitude,while the distance from coils to the bottom of molten aluminum changes the magnitude of magnetic flux density but no change of distribution.

Electrochemical Deposition and Nucleation of Aluminum on Tungsten in Aluminum Chloride-Sodium Chloride Melts

Electrochemical deposition and nucleation of aluminum on tungsten electrode from AlCl3-NaCl melts were studied by cyclic voltammetry, chronopotentiometry and chronoamperometry. Cyclic voltammetry and chronopotentiometry analyses showed that Al （Ⅲ） was reduced at 200℃ in two consecutive steps in an electrolyte of molten AlCl3-NaCl system with a composition 52：48 molar ratio. The current-time characteristics of nucleation aluminum on tungsten showed a strong dependence on overpotentials. Chronoamperometry showed that the deposition process of aluminum on tungsten was controlled by an instantaneous nucleation with a hemispherical diffusion-controlled growth mechanism. The results could lead to a better understanding of the AlCl3-NaCl melt system that has technological importance in electrodeposition of metals as well as in rechargeable batteries.

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

The difference of conductivity between primary iron-rich phases and aluminum melt has been used to separate them by electromagnetic force (EMF) which is induced by imposing a direct electric current and a steady magnetic field in molten Al-Si alloy. Theoretical analysis and experiments on self-designed electromagnetic separation indicates that primary needle-like β phases are difficult to separate; while primary α iron-rich phases can be separated by electromagnetic separation. Primary iron-rich phases have been removed from the melt successfully when the molten metal flows horizontally through separation channel. The iron content is reduced from 1.13% to 0.41%.

Influence of melt-treatment on material constants of aluminum sheet used for easy-open can during hot deformation

The isothermal compression test at elevated temperature was carried out for aluminum sheets prepared by different melt-treatment methods with aid of dynamic hot/mechanical simulation experimental technology. The material constants of hot deformation have been solved by multivariate regression directly. Influence of metallurgy factors on the constants was analyzed. The results show that at some strain, the relationship of sheets’ flow stress with deformation temperature and strain rate can be expressed more suitably with Arrhenius equation modified by hyperbolic sine function. Structure factor A1, stress-level coefficient α, strain rate sensibility exponent m and deformation activation energy Q all increase with increment of strain, while stress exponent n decreases gradually. The bigger α value or the smaller n value is, the more obvious the dynamic softening is, but the α value will increase for the metallurgy defects existing in the sheets. Influence of melt-treatment on Q depends upon the synthesis effect of all kinds of metallurgy defects. The Q and n values of the sheet prepared by high-efficient melt-treatment are the least, while the m value is the biggest, and the sheet can deform easily and evenly.

Structure of Liquid Aluminum and Hydrogen Absorption

The hydrogen content in aluminum melts at different temperature was detected. The structure in aluminum melts was investigated by molecular dynamics simulation. The first peak position of pair correlation function, atomic coordination number and viscosity of aluminum melts were calculated and they changed abnormally in the same temperature range. The mechanism of hydrogen absorption has been discussed. From molecular dynamics calculations, the interdependence between melt structural properties and hydrogen absorption were obtained.

选区激光熔化SiC颗粒增强AlMgScZr复合材料的微观组织与力学性能

铝基复合材料具有硬度高、切削加工难度大的特点。为了实现高比强度、高比模量铝基复合材料的近净成形,该文利用激光增材制造技术制备了10%(体积分数)微米级SiC颗粒增强AlMgScZr复合材料,建立了激光能量密度、扫描速率与复合材料成形质量的对应关系,通过光学显微镜(OM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)和万能试验机对微观组织和力学性能进行表征和测试,探讨了微米级SiC颗粒对选区激光熔化(SLM)成形铝基复合材料凝固组织和力学性能的作用机理。结果表明:在铺粉层厚为30μm、扫描间距为0.12mm、激光功率为260W、扫描速率为1000mm/s的工艺参数下,可获得成形质量最佳的SiC/AlMgScZr复合材料,其致密度可达99.81%;激光熔覆过程中,SiC颗粒与Al基体之间发生了剧烈的界面反应,SiC颗粒尖角明显钝化,原位生成的微米级针状Al4SiC4条带与残余SiC颗粒形成混合增强结构;时效态SiC/AlMgScZr复合材料的抗拉强度为379MPa、延伸率为12%、弹性模量为84 GPa,其断裂形式为Al基体的韧性断裂和Al4SiC4相的脆性解理断裂,大量交错分布的针状Al4SiC4条带是材料发生过早失效断裂的主控因素。

THEORETICAL ANALYSIS FOR THE MOTION AND TEMPERATURE OF MELT DROPLETS IN SPRAY DEGASSING PROCESS

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process couM be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets wouM solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results,

Preparation, mechanical properties and wear behaviors of novel aluminum bronze for dies

A modified single melt technique involving joint charging was developed for preparation of aluminum bronze, Cu-14%Al-X(mass fraction) alloy, which could be used as die materials. The mechanical properties and wear behavior of the developed alloy under boundary-lubrication conditions was investigated. The results demonstrate that all the phases disperse homogeneously in the bronze matrix with a significant amount of discrete and spherical brittle and hard γ2 phase, moreover, the dispersed κ phase are the dominant factor that improves the anti-deformation properties of the soft matrix, after a solution treatment at 920 ℃ for 2 h and followed by aging at 580 ℃ for 3 h, thus remarkably improves the mechanical properties and wear resistance of the developed alloy. The Cu-14%Al-X alloy can be used as materials for static precise stretching and squeezing dies.