Electromagnetic Casting Research Articles

Development and Application of a New Al-Si-Mg Alloy for Semi-Solid Forming

Based on A356, development and application of a new Al-Si-Mg alloy had been studied, aimed to get an alloy with excellent mechanical property and suitable for semi-solid forming. An adjustment of Mg content is made, from 1% to 2.5%, to ensure the composition range. The temperature range of semi-solid alloys can be obtained through the phase calculation on the alloys with T-cal, a kind of thermodynamic software. The accuracy of phase can be verified with differential scanning calorimeter (DSC). The chosen alloys are melted to be prepared for specimens, followed by mechanical testing. Finally, the optimal composition can be got according to mechanical properties, to be used for electromagnetic continuous casting, followed by the induction reheating and thixotropic semi-solid forming process. The law analyses were discussed during the induction reheating for Al-Si-Mg alloy and A356.

Numerical Simulation of High Frequency Electromagnetic Field in Soft Contact Continuous Casting Mold

Based on electromagnetic theory, a billet model electromagnetic continuous casting of physical and mathematical were established. The three-dimensional mold for billet electromagnetic field was calculated by finite element method of ANSYS three-dimensional numerical simulation. Then the distribution of the electromagnetic field inside the crystal was gotten. At the same time, the influence of the power frequency and current strength on the intensity and distribution of the magnetic field were simulated. The result shows that the maximum of the electromagnetic flux density lies in the center of induction coil (steel surface in the center of the coil), and the magnetic flux density gradually reduces along the casting direction; the magnetic flux density increases while the power frequency is increasing; the magnetic flux density increases with the increasing of the current intensity.

Preparing Large Sized Billet of High Strength Aluminum Alloy with the Application of Low Frequency Electromagnetic Field

Grain refinement is quite important for producing 7050 alloy billet especially in large scale. Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy Φ500 mm billets and study the effect of electromagnetic field on the microstructure. The sound Φ500 mm billets of 7050 alloys without any grain refiner can be successfully prepared by the LFEC process. The results show that low frequency electromagnetic field has a significant grain refining effect on 7050 alloy and can effectively eliminate feather grain structure. The microstructures of LFEC ingot from the border to the center of the cross section are all equiaxed grains and are finer and more uniform than that of conventional direct chill (DC) cast billets. The LFEC process also shows a strong power to eliminate hot tearing during casting large sized billet of high strength aluminium alloy.

Feasibility of directional solidification of silicon ingot by electromagnetic casting

Electromagnetic casting is a novel technology that combines the advantages of electromagnetic cold crucible and continuous casting. By controlling induction heating and strengthening bottom cooling, multicrystalline silicon ingot with 60mm×60mm in cross section was continuously and directionally solidified by this technology. The ingot shows smooth surface and consists of uniform columnar crystals with no precipitate except in the top part. The grain size of the top part is smaller due to higher impurity content and the impurities acting as nucleation sites for grain. The density of dislocations at the bottom and middle parts, about 1×106cm−2, is much less than that at the top part.

Shape optimization for inverse electromagnetic casting problems

In this article we present an algorithm for inverse optimization problems concerning electromagnetic casting of molten metals. We are interested in locating suitable inductors around the molten metal so that the equilibrium shape will be as near as possible to a desired target shape. A simultaneous analysis and design mathematical programming formulation is stated for the inverse problem. The resulting optimization problem is solved with FAIPA, a feasible directions interior-point algorithm.

Combined Effect of Electromagnetic Field and Grain Refiner on Microstructure of Φ310 Mm 7050 Aluminium Alloy Ingot

Grain refinement is quite important for producing 7050 alloy ingot especially in large scale. Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy Φ310 ingots and study the effect of electromagnetic field and grain refiner on the microstructure of 7050 alloy ingots. The results showed that both grain refiner and low frequency electromagnetic field can result in some grain refinement of 7050 alloy. However, the low frequency electromagnetic field shows more remarkable grain refinement. For the grain refined alloy by grain refiner, further significant grain refinement can be achieved with the application of low frequency electromagnetic field. The finest microstructure was achieved by combining the applications of both grain refiner and electromagnetic field.

Grain Refinement of Direct Chill Cast 7050 Aluminium Alloy with Low Frequency Electromagnetic Field

Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy 162mm ingots and study its effect on the as-cast microstructure. Effects of electromagnetic field parameters such as frequency and current intensity on microstructures were systemically investigated. The results showed that LFEC has a significant grain refining effect on 7050 alloy. The microstructures of LFEC ingot from the border to the center of the cross section are all equiaxed or nearly equiaxed grains which are much finer and more uniform than those of DC cast ingot. It was also found that electromagnetic field frequency and current intensity play important roles on the microstructure refinement. The discussion was mainly focused on the mechanism of grain refinement by LFEC process.

Solidification of electronic materials: An overview

Electronic materials are now found throughout the world and are used in virtually every aspect of life. Consider a backcountry canoe trip (one of my favorite activities)—although nature surrounds the canoeist, the presence of perhaps a radio and light-emitting diode fl ashlight, as well as a solar panel for recharging batteries and energy storage is a reminder of modern technology. The radio, fl ashlight, and solar panel all contain electronic materials to enable component usage, heavily processed to meet purity, reliability, and/or dopant requirements. Solidifi cation affects three aspects of electronics and electronic materials production. First, an electronic material must meet strict purity requirements to optimize related physical and functional properties. High-purity materials can only be produced through excellent control of the casting process. Second, solidifi cation is used during component assembly to physically join or solder various electrical devices to the underlying printed circuit board. Third, the quality of the solder will affect the long-term in-service reliability of the electronic component. This issue of JOM explores the topic of electronic materials solidifi cation by examining the fundamentals along with processing-related questions. In the past few years, advances in this fi eld have occurred in the areas of leadfree solders, multicrystalline silicon production for photovoltaic cells, and component assembly processing techniques. The fi rst two papers examine solidifi cation mechanisms in silicon alloys for solar cell applications. The major challenge in this industry is to meet purity requirements enabling high cell effi ciency while reducing costs. In the fi rst paper, L. Arnberg et al. critically assess a number of the most common methods for producing multicrystalline silicon. Although the Czochralski crystal pulling and Bridgman-type directional solidifi cation methods currently dominate the market, new techniques such as electro-magnetic casting and direct ribbon casting are shown to have potential for signifi cantly higher productivity. Next, the use of a crucible cover during directional solidifi cation is examined by B. Gao et al. as a method for improving alloy purity levels. Numerical simulations show that while the use of a crucible can signifi cantly reduce carbon and oxygen levels in the melt, new design strategies are needed to ensure that the crucible cover does not react with the SiO gas. The conversion to lead-free solder alloys and increased warpage due to the use of thinner microelectronic packaging technologies has increased the risk of solder joint defects during component assembly. In the third paper, by R.S. Sidhu et al., the common head-and-pillow solder defect that occurs between fi ne-pitch ball grid array (BGA-type) electronic packages and the motherboard during surface mount assembly is examined and the mechanisms related to various aspects of design and solder quality that affect defect formation are discussed. It is shown that even small variations in solder chemistry can lead to increased risk of defect formation; chemistries that reduce oxide formation or extend solidifi cation undercooling are benefi cial as they increase the time available for wetting between the solder ball and paste. Solidifi cation mechanisms in tinrich lead-free solders is also the focus of the fourth paper, by M. Felberbaum et al. In this work, the mechanisms responsible for the benefi cial effects of Ni in Sn-0.7Cu solder are investigated through the use of Bridgman solidifi cation experiments and microscopy. It is shown that changes in microstructure morphology are due mostly to the segregation of impurity elements, particularly lead, and not the nickel content. Instead, the nickel addition is benefi cial as it improves the fl uidity and reduces the freezing range. In summary, solidifi cation issues within electronic materials are diverse, and can provide many avenues for scientifi c research and development. Novel solidifi cation techniques, especially in multicrystalline silicon for photovoltaics and component reliability, are necessary for improving the economics of renewable-energy sources. The articles in this issue capture only a small subset of current unanswered questions while highlighting key achievements and remaining challenges.

Production of super-high strength aluminum alloy billets by low frequency electromagnetic casting

The effects of low frequency electromagnetic field on the macro-physical fields in the semi-continuous casting process of aluminum alloys and the microstructure and crack in the billets were studied and analyzed by the numerical and experimental methods. Comparison of the results for the macro-physical fields in the low frequency electromagnetic casting (LFEC) process with the conventional DC casting process indicates the following characters due to the application of electromagnetic field: an entirely changed direction and remarkably increased velocity of melt flow; a uniform distribution and a decreased gradient of temperature; elevated isothermal lines; a reduced sump depth; decreased stress and plastic deformation. Further, the microstructure of the billets is refined remarkably and the crack in the billets is eliminated in LFEC process because of modification of the macro-physical fields induced by the application of low frequency electromagnetic field.

The Microstructure and Properties of ZL116 Alloy Obtained by the Nearby-Liquidus Electromagnetic Casting

Studying the microstructures of ZL116 alloy slurry prepared by nearby liquidus electromagnetic casting (NLEMC), electromagnetic casting (EMC), and nearby liquidus casting (NLC) by means of electron microscope and image analysis apparatus. At the same time, determining the their hardness by using hardness instrument. The results show that the NLEMC can obtain the fine and uniform equiaxed grains structure, its average-area-circle grain diameter is 28.5μm, and its rheoforming parts, hardness is 129Hv. All of these also show that the slurry microstructure and rheoforming properties of ZL116 prepared by NLEMC are the best in the three kinds of ways. At the same time, discussing the mechanism of NLEMC structure fine.

Effect of Physical Fields on Solidification Structures of DC Casting AZ80 Magnesium Alloy Billets

AZ80 magnesium alloy was semi-continuously cast under different physical fields which were conventional direct chill (DC) casting, low frequency electromagnetic casting (LFEC), ultrasonic casting (USC) and electromagnetic-ultrasonic combined casting (ECUC), respectively. The effect of different physical fields on solidification structures of AZ80 alloys was investigated. The results show that compared with the conventional DC casting, structures of AZ80 alloys billets cast with LFEC and USC have been greatly refined. The effective refinement takes place in the edge of billets when LFEC is applied. However, the effective refinement takes place in the center of billets when USC is applied. When combination of low frequency electromagnetic and ultrasonic fields is applied during semi-continuous casting AZ80 magnesium alloy billet, structures of AZ80 alloys are refined significantly in the whole billets everywhere and more uniform.

Experimental study on hot melt splashes during electromagnetic continuous casting silicon

Hot melt splashes often take place during electromagnetic casting silicon, which break the stable pulling process and endanger the safety of equipments in the vacuum chamber. Investigations are carried out to analyze the causes of melt splashes and put forward measures to prevent the happening of them. Pores with different sizes are observed in perpendicular sections of the left ingots, their surface compositions are analyzed by EDS. The results indicate that they are rich in O, Al, Ca and Mg elements, which means that the driving pressures of hot melt splashes are mainly the vapor tension of SiO, Al, Ca and Mg. Calculated results show that the volatilization of those elements is inevitable, so the vapor excluding and pressure releasing are key issues for preventing hot melt splashes, both of which are affected by the height and top position of the liquid dome. Therefore, controlling of those parameters properly can efficiently prevent the hot melt splashes. The optimal dome top position is from 6 mm to 16 mm lower than the coil top position.

Quantitative metallographic assessment of the electromagnetic casting influence on the microstructure of 7075 Al alloy

This study presents an attempt to obtain the better quality of an aluminum super-high strength alloy by application of electromagnetic field during the casting process. The conventional continuous casting process of aluminum alloys causes many defects, such as surface imperfections, grain boundary segregation, non-uniform grain size, and porosity. The better ingot surface along with the homogeneous fine-grained microstructure, and hence the better mechanical properties of the ingot, can be achieved by applying the electromagnetic casting process. The microstructure characterization, accompanied by quantitative metallographic assessment, reveals that it is possible to avoid or decrease many defects of as cast ingots during electromagnetic casting process. In this article, the microstructure of the samples of as cast 7075 aluminum alloy, obtained with and without electromagnetic field influence, was analyzed by optical microscope and the variation of key alloying elements content, i.e., Zn and Mg, through the ingot cross section was examined by chemical analysis. Besides, the microstructural parameters such as dendrite arm spacing, interdendritic space width, as well as eutecticum and intermetallic phases volume fraction, were measured using linear method. The electromagnetic field influence on the microstructure of the as cast 7075 Al alloy was evaluated based on measured quantitative metallographic data.

Microsegregation development of heavily electromagnetically stirred melt of super high strength Al–10Zn–2·5Mg–2·3Cu alloy

Low frequency electromagnetic casting applied to high strength aluminium alloys promoted heavy stirring in direct chill melt, which prevented hot cracking of aluminium alloys never manufactured by direct chill. For instance, Al–10Zn–2·7Mg–2·3Cu alloy was able to be produced by low frequency electromagnetic casting because of the fine grain size, which is small enough, such as 50 μm, when cast into 200 mm diameter billet. It is of importance to understand the microscopic solidification behaviour to properly develop alloy design. Therefore, microsegregation in accordance with solidification progress, including the formation of various kinds of intermetallic compounds, was discussed by precise experiment through compositional analysis using microprobe mapping method. Even under a peculiar solidification condition of refined equiaxed crystals, microsegregation development was apparently similar to a columnar dendrite growth in which the initial solute pile-up was attributed to the diffusion in liquid. For heavily electromagnetically stirred billet, microsegregation was governed by back diffusion.

Structure and mechanical properties of AZ31 magnesium alloy billets by different hot-top semi-continuous casting technology

AZ31 alloy billets of 200 mm in diameter were produced by three different processes of conventional direct chill (DC) casting, low-frequency electromagnetic casting (LFEC) and low-frequency electromagnetic vibration casting (LFEVC), respectively. The effect of LFEC and LFEVC on the microstructures, macrosegregation and mechanical properties of AZ31 alloy billets was investigated. In conventional DC casting, the AZ31 alloy billets exhibited coarse grains (about 370 μm) and severe segregation of Al and Zn. In the presence of a solo low-frequency alternating magnetic field or a low-frequency electromagnetic vibration field applied during DC casting of ϕ200 mm AZ31 billets, grains in the AZ31 alloy billets were effectively refined (about 210 μm) and the macrosegregation of Al and Zn in the billets was greatly decreased. Furthermore, the tensile strength, fracture elongation and hardness of the as-cast AZ31 alloy billets were improved by the processes of LFEC and LFEVC relative to that cast by the process of conventional DC casting.

Effect of parameters on the grain growth of silicon ingots prepared by electromagnetic cold crucible continuous casting

In this paper silicon ingots were continuously and directionally solidified by electromagnetic casting (EMC). A group of orthogonal experiments were completed to investigate the effects of input power, withdrawal velocity and initial heat preservation time on the grain growth of silicon ingots. The results showed that all of the deviating angle ( θ), the convex height of the solid/liquid (S/L) interface, the thickness of the surface fine grain zone and grain size in the centre zone decrease with increasing input power and withdrawal velocity. Increasing initial heat preservation time results in larger grain size in the centre zone, but has little effect on the convex height of S/L interface and the thickness of the surface fine grain zone. The results were explained by the heat transfer analysis during the steady casting process and the optimised parameters for casting silicon were given finally.

Effects of the Low Frequency Electromagnetic Field on the Centerline Macrosegregation of 7075 Aluminum Ingots

The effects of the low frequency electromagnetic field on the macrosegregation of the 7075 aluminum ingots were investigated. The 7075 aluminum ingots with the diameter of 200 mm were prepared by the conventional direct chill casting and the low frequency electromagnetic field casting (LFEC) processes, respectively. The temperature during casting at steady state was measured, and the mushy region was observed from the temperature contour. The concentrations of the alloying elements were measured by the spectrograph. It was found that the transition region was broadened, but the mushy zone became narrower with presence of the low frequency electromagnetic field. The centerline macrosegregation of the ingots was alleviated by the low frequency electromagnetic casting process.

Present Situation and Development Perspective of Soft-Contact Electromagnetic Continuous Casting Technology

Soft-contact electromagnetic continuous casting is one of innovative technologies for the development of steel industry. In this paper, the present situation was reviewed from five aspects: the soft-contact mold material and structure parameter design, the electromagnetic field distribution, the meniscus shape and movement behavior, casting slab surface quality improvement mechanism and the method of magnetic fields imposed. The main questions of the technology were analysed, and the remarhable in the process of industrialization were pointed out.

Effects of Electromagnetic Parameters on the Process of Low Frequency Electromagnetic Hot-Top Casting of Aluminium Alloy

During the low frequency electromagnetic casting process, the electromagnetic parameter plays an important role among the casting parameters. In this work, effects of electromagnetic parameters on the electromagnetic field and body force are analyzed by constructing a two-dimensional finite element model and using ANSYS software which is a kind of commercial FEM analysis software. The results show that the current frequency mainly influences the distribution of electromagnetic body force, the current intensity determines the intensity of electromagnetic body force, and the current frequency and intensity should be matched during the low frequency electromagnetic casting process.

Research on Heat Transfer during LFEC Processing by <i>In Situ</i> Temperature Measurement

Low-frequency electromagnetic casting (LFEC) processing could improve not only the metallurgical quality of magnesium billet including refining grain size, reducing regional microstructural difference and lightening segregation, but also its surface quality due to the effect of applied electromagnetic field according to the results by microstructure observation and the numerical simulation. In this research in-situ temperature measurement was carried out in LFEC processing in order to investigate heat transfer behavior of billet during solidification. The effects of the electromagnetic conditions (frequency and the intensity) together with the casting temperature on the sump and the mushy zone were investigated in detail. The results indicate that all the casting conditions affect the temperature field of magnesium billet markedly during solidification. Electromagnetic field could decrease not only the sump depth but also the difference of regional temperature field along the solidification direction leading to much more uniform cooling rate.