**1. Introduction**

The creation of new inorganic materials, in particular metallic, requires the improvement of existing and the development of new methods for their preparation. The latest melting methods (vacuum arc, induction and electron beam, electroslag, zone, plasma, laser, etc.) of metal melts contribute to further development of modern materials science, while possessing well-known limitations. There is no universal method of melting that would completely satisfy the most diverse requirements of scientists and engineers engaged in this problem. Therefore, it is necessary to use combinations of known melting methods. In this regard, it is of considerable interest to use new methods of melting, for example, electromagnetic levitation (EML) or induction melting furnaces with a cold crucible. It should be noted that, despite a number of obvious advantages, induction melting with a cold crucible cannot yet be widely applied due to imperfect energy conditions for heating the charge and significant heat losses, although quite a certain progress is observed in the designs of furnaces using the principle of cold crucible.

Otto Muck proposed electromagnetic levitation of a metal melt, which is also called melting in an electromagnetic crucible or noncontact, in 1923. He gave the first and simple theoretical explanation of this phenomenon-the implementation of suspension or metal levitation by an electromagnetic field. However, only 30 years later, the first works on the theory and use of this type of melting appeared. Later, studies appeared aimed at expanding the applied and scientific functions of the levitation of metals and alloys both on a laboratory and semi-industrial scale. It is also interesting that the theoretical justification of the method has always been accompanied by the development of EML [1–11].


Perhaps the disadvantages of the method include a small mass of metal, not exceeding several tens of grams, which to some extent limits the wide industrial application of the method. However, there are known applications of EML in the application of thin coatings in electronics, or the production of fine powders for additive technologies. By the way, for most physical and physicochemical studies, a small mass is not an obstacle.

EML techniques enable the noncontact study of thermophysical properties over a wide temperature range. In this regard, an overview on measuring enthalpy through the method of levitation dropping calorimetry for 30 years is of interest [11]. The results of these measurements of melting enthalpies and melting entropies really amaze with the breadth of coverage (three subgroups of refractory metals) and the complete novelty (obtained for the first time due to EML). For these three subgroups of the periodical table: IVb (Ti, Zr, Hf), Vb (V, Nb, Ta), and VIb (Cr, Mo, W), a group similarity was discovered. Accordingly, the melting entropy of metals of the fourth group is 6.8–8 J mol<sup>−</sup><sup>1</sup> K<sup>−</sup><sup>1</sup> , the fifth group is 10–11 J mol<sup>−</sup><sup>1</sup> K<sup>−</sup><sup>1</sup> , and the sixth group is 13–14 J mol<sup>−</sup><sup>1</sup> K<sup>−</sup><sup>1</sup> , although earlier these data simply did not exist. As for possible industrial applications, the promising process of deposition of thin films of light metals on metal and plastic surfaces, based on the levitation of conductive materials in a high-frequency electromagnetic field, has been studied [12]. The authors focused on the design of the inductor, which ensures the achievement of high specific powers, and the system of rational distribution of vapor, which contributes to the production of a uniform thin coating. According to the authors of [12], this method is most optimal when applying thin coatings of metals with low vapor pressure, such as Al, Ni, Cu and their alloys. It seems quite natural and reasonable to use EML as a part of new technology for high rate physical vapor deposition of coatings onto metallic strip. Many publications are known in which, at a good theoretical level, specific technical problems were solved, for example, increasing the mass of levitated metal or spraying liquid metal [13–22].

During EML, the sample quickly melts, the melt undergoes strong mixing, and as a result, the melt becomes completely homogeneous [23–33]. EML has become widely used to study the refining processes in obtaining metals of high purity, active and with high melting points. EML of metals means the electromagnetic interaction of a sample and a magnetic field. For this, metal samples are placed in an inductor

**163**

with a wide range of alloys.

trations were studied.

applications.

*Electromagnetic Levitation of Metal Melts DOI: http://dx.doi.org/10.5772/intechopen.92230*

which leads to heating and melting of the sample.

with a high-frequency alternating current, forming an electromagnetic field in which the sample rises and then melts. Induction current, as a rule, arises on the surface of metal samples, and the interaction between the induction current and the high-frequency magnetic field forms the Lorentz force, which is in equilibrium with the gravity of a solid metal sample in a magnetic field of a certain configuration. As a result, the metal sample hangs in the inductor and levitation is realized. The simultaneous action of the induced current or eddy currents generates Joule heat,

The lifting power of levitation, temperature and stability are important factors in the state of EML. At different times, the researchers modeled the influence of the design and arrangement of inductors on the dynamic deformation and stability of metal melts, as well as the vibrations of metal droplets at different points in time, for which arbitrary Lagrange-Euler equations and the finite element method were used. The effect of the second (transverse) magnetic field on the stability of rotation of the experimental samples was also investigated. In the process of EML, the samples are simultaneously subjected to heating and levitation, and EML creates a high temperature distributed on and around the levitated melt. The factors affecting the temperature characteristics of EML, the melting of samples with low conductivity and high density at relatively low temperatures are investigated. It seems interesting to study the influence of the structural dimensions of multi-turn inductors and the sizes of a metal sample on the temperature characteristics of EML, analyzed with the aim of correctly choosing a suitable inductor for various

EML of melts is a progressive and universal method for conducting hightemperature physical and physicochemical studies necessary to improve metallurgical processes, as well as a means for producing miniature parts and samples from high-purity metals. Due to its unique characteristics, noncontact levitation provides obvious advantages in the field of research of new materials. Compared to traditional studies using crucibles made of refractory materials, noncontact technology is a unique research technique, and only it opens up the possibility of completely avoiding contaminants entering the metal melt from the refractory material of the crucible. Noncontact levitation is also used to crystallize samples of objects, measure physical and chemical properties, and produce ingots of highly pure crystalline and amorphous materials. Noncontact measurement of the physical and physicochemical properties of liquid metals made it possible to observe thermal and surface vibrations during the levitation of metal melts not only in terrestrial conditions, but also in zero or microgravity [34–38]. Significant underheating of the sample can be one of the advantages of the noncontact method of levitation. Undercooling means the nonequilibrium state of a liquid sample at temperatures below its equilibrium melting point. The noncontact of a liquid sample is the essence of EML, especially when combined with an ultrapure process medium. In addition, EML is one of the oldest noncontact methods of levitation used for material science experiments for decades. New levitation methods include aerodynamic and acoustic levitation, as well as electrostatic levitation. In these methods, levitation forces arise from electrodes located above and below a sample containing a surface charge, while heating is performed, for example, using a laser. EML is the most mature of all noncontact melting methods and has been used for decades in ground-based experiments, as well as in experiments with microgravity

Thus, surface tension, density and solubility of various gases in liquid metals were measured, as well as decarburization parameters were established, and features of the Fe desulfurization ability of slags in a wide range of carbon concen-

#### *Electromagnetic Levitation of Metal Melts DOI: http://dx.doi.org/10.5772/intechopen.92230*

*Magnetic Materials and Magnetic Levitation*

accompanied by the development of EML [1–11].

• Controlled gas atmosphere and slag phase.

passage of heterogeneous reactions.

small mass is not an obstacle.

metals of the fourth group is 6.8–8 J mol<sup>−</sup><sup>1</sup>

and the sixth group is 13–14 J mol<sup>−</sup><sup>1</sup>

• Vigorous stirring of metal by electromagnetic field.

• Achieving extremely high crystallization rates up to 105

is also interesting that the theoretical justification of the method has always been

• Controlled metal temperature (from melting temperatures to boiling).

• Ability to use an additional heat source (electronic, laser beam or plasma).

• A favorable ratio between the surface of the droplet and its volume for the

Perhaps the disadvantages of the method include a small mass of metal, not exceeding several tens of grams, which to some extent limits the wide industrial application of the method. However, there are known applications of EML in the application of thin coatings in electronics, or the production of fine powders for additive technologies. By the way, for most physical and physicochemical studies, a

EML techniques enable the noncontact study of thermophysical properties over a wide temperature range. In this regard, an overview on measuring enthalpy through the method of levitation dropping calorimetry for 30 years is of interest [11]. The results of these measurements of melting enthalpies and melting entropies really amaze with the breadth of coverage (three subgroups of refractory metals) and the complete novelty (obtained for the first time due to EML). For these three subgroups of the periodical table: IVb (Ti, Zr, Hf), Vb (V, Nb, Ta), and VIb (Cr, Mo, W), a group similarity was discovered. Accordingly, the melting entropy of

K<sup>−</sup><sup>1</sup>

K<sup>−</sup><sup>1</sup>

increasing the mass of levitated metal or spraying liquid metal [13–22].

During EML, the sample quickly melts, the melt undergoes strong mixing, and as a result, the melt becomes completely homogeneous [23–33]. EML has become widely used to study the refining processes in obtaining metals of high purity, active and with high melting points. EML of metals means the electromagnetic interaction of a sample and a magnetic field. For this, metal samples are placed in an inductor

exist. As for possible industrial applications, the promising process of deposition of thin films of light metals on metal and plastic surfaces, based on the levitation of conductive materials in a high-frequency electromagnetic field, has been studied [12]. The authors focused on the design of the inductor, which ensures the achievement of high specific powers, and the system of rational distribution of vapor, which contributes to the production of a uniform thin coating. According to the authors of [12], this method is most optimal when applying thin coatings of metals with low vapor pressure, such as Al, Ni, Cu and their alloys. It seems quite natural and reasonable to use EML as a part of new technology for high rate physical vapor deposition of coatings onto metallic strip. Many publications are known in which, at a good theoretical level, specific technical problems were solved, for example,

–106 °C/s.

, the fifth group is 10–11 J mol<sup>−</sup><sup>1</sup>

, although earlier these data simply did not

 K<sup>−</sup><sup>1</sup> ,

• Adjustable residence time of a drop of metal in a liquid state.

• Possibility of introducing alloying additives into a liquid drop.

**162**

with a high-frequency alternating current, forming an electromagnetic field in which the sample rises and then melts. Induction current, as a rule, arises on the surface of metal samples, and the interaction between the induction current and the high-frequency magnetic field forms the Lorentz force, which is in equilibrium with the gravity of a solid metal sample in a magnetic field of a certain configuration. As a result, the metal sample hangs in the inductor and levitation is realized. The simultaneous action of the induced current or eddy currents generates Joule heat, which leads to heating and melting of the sample.

The lifting power of levitation, temperature and stability are important factors in the state of EML. At different times, the researchers modeled the influence of the design and arrangement of inductors on the dynamic deformation and stability of metal melts, as well as the vibrations of metal droplets at different points in time, for which arbitrary Lagrange-Euler equations and the finite element method were used. The effect of the second (transverse) magnetic field on the stability of rotation of the experimental samples was also investigated. In the process of EML, the samples are simultaneously subjected to heating and levitation, and EML creates a high temperature distributed on and around the levitated melt. The factors affecting the temperature characteristics of EML, the melting of samples with low conductivity and high density at relatively low temperatures are investigated. It seems interesting to study the influence of the structural dimensions of multi-turn inductors and the sizes of a metal sample on the temperature characteristics of EML, analyzed with the aim of correctly choosing a suitable inductor for various applications.

EML of melts is a progressive and universal method for conducting hightemperature physical and physicochemical studies necessary to improve metallurgical processes, as well as a means for producing miniature parts and samples from high-purity metals. Due to its unique characteristics, noncontact levitation provides obvious advantages in the field of research of new materials. Compared to traditional studies using crucibles made of refractory materials, noncontact technology is a unique research technique, and only it opens up the possibility of completely avoiding contaminants entering the metal melt from the refractory material of the crucible. Noncontact levitation is also used to crystallize samples of objects, measure physical and chemical properties, and produce ingots of highly pure crystalline and amorphous materials. Noncontact measurement of the physical and physicochemical properties of liquid metals made it possible to observe thermal and surface vibrations during the levitation of metal melts not only in terrestrial conditions, but also in zero or microgravity [34–38]. Significant underheating of the sample can be one of the advantages of the noncontact method of levitation. Undercooling means the nonequilibrium state of a liquid sample at temperatures below its equilibrium melting point. The noncontact of a liquid sample is the essence of EML, especially when combined with an ultrapure process medium. In addition, EML is one of the oldest noncontact methods of levitation used for material science experiments for decades. New levitation methods include aerodynamic and acoustic levitation, as well as electrostatic levitation. In these methods, levitation forces arise from electrodes located above and below a sample containing a surface charge, while heating is performed, for example, using a laser. EML is the most mature of all noncontact melting methods and has been used for decades in ground-based experiments, as well as in experiments with microgravity with a wide range of alloys.

Thus, surface tension, density and solubility of various gases in liquid metals were measured, as well as decarburization parameters were established, and features of the Fe desulfurization ability of slags in a wide range of carbon concentrations were studied.
