REDUCTION METHOD AND SYSTEM FOR HIGH-MELTING-POINT METAL OXIDE, USING FLUORIDE-BASED ELECTROLYTES

Abstract

The present disclosure relates to a metal oxide reduction method and, specifically, to a metal oxide reduction method which, in producing a high-grade alloy metal using a metal oxide as a raw material, enables operation in the atmosphere by moving away from an existing production process in an inert gas atmosphere, and is easy to commercialize and can maximize efficiency, as an eco-friendly method is used.

Claims

1. A method of reducing metal M.sup.1 from a metal oxide, comprising: forming a molten salt of a fluoride-based flux in an cell; putting, into the cell, a metal M.sup.2 forming an eutectic phase with the metal M.sup.1, and a reducing agent including a metal M.sup.3 to produce an eutectic composition of the metal M.sup.2 and the metal M.sup.3; and reducing the metal M.sup.1 by reacting the metal oxide with the eutectic composition and forming a liquid metal alloy with the reduced metal M.sup.1 and M.sup.2, wherein density of the molten salt is less than density of the eutectic composition and the metal oxide.

2. The method of claim 1, wherein the molten salt has a volatilization rate of 10% by weight or less at 1,600 C. for 10 hours.

3. The method of claim 1, wherein the fluoride-based flux is one or more selected from the group consisting of MgF.sub.2, CaF.sub.2, SrF.sub.2, and BaF.sub.2.

4. The method of claim 3, wherein the fluoride-based flux is CaF.sub.2.

5. The method of claim 1, wherein the metal M.sup.1 is one or more selected from the group consisting of Ti, Zr, Hf, W, Fe, Ni, Zn, Co, Mn, Cr, Ta, Ga, Nb, Sn, Ag, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, and No.

6. The method of claim 1, wherein the metal M.sup.2 is one or more selected from the group consisting of Cu, Ni, Sn, Zn, Pb, Bi, Cd, and alloys thereof.

7. The method of claim 6, wherein the metal M.sup.2 is Cu.

8. The method of claim 1, wherein the metal M.sup.3 is one or more selected from the group consisting of Ca, Mg, Al, and alloys thereof.

9. The method of claim 1, wherein the metal oxide includes one or more selected from the group consisting of M.sup.1.sub.xO.sub.z, and M.sup.1.sub.xM.sup.3.sub.yO.sub.z: wherein x and y are a real number from 1 to 3, respectively, and z is a real number from 1 to 4.

10. The method of claim 1, wherein a process of reducing the metal M.sup.1 by reacting the metal oxide with the eutectic composition is performed in air or in fluoride.

11. The method of claim 1, wherein a process of reducing the metal M.sup.1 by reacting the metal oxide with the eutectic composition is performed in a range of 900 to 1,600 C.

12. The method of claim 1, further comprising forming slags of the molten salt and a by-product generated in a process of reducing the metal M.sup.1 by reacting the metal oxide with the eutectic composition by adding a slag-forming additive.

13. The method of claim 12, wherein the slag-forming additive comprises one or more selected from the group consisting of MgO, CaO, FeO, BaO, SiO.sub.2, and Al.sub.2O.sub.3.

14. The method of claim 12, further comprising: forming a layer in which the liquid metal alloy is positioned at a bottom of the cell and separated from the eutectic composition, and continuously obtaining the liquid metal alloy through a lower portion of the cell; and forming a distinct layer on top of the eutectic composition using the slags, and continuously removing the slags through a top of the cell.

15. The method of claim 1, further comprising electrorefining the liquid metal alloy to produce the metal M.sup.1.

16. A metal obtained by the method of claim 15.

17. A metal alloy obtained by the method of claim 1.

18. The method of claim 17, wherein a residual content of the metal M.sup.3 is 0.1% by weight or less based on the total weight of the metal alloy, and a oxygen content is 1,800 ppm or less.

19. A system for reducing metal M.sup.1 from a metal oxide, comprising: an cell; a molten salt of a fluoride-based flux positioned in the cell; an eutectic composition of metal M.sup.2 and metal M.sup.3 positioned at a lower portion of the molten salt; and a liquid metal alloy of the metal M.sup.1 and the metal M.sup.2 positioned below the eutectic composition; wherein a density of the molten salt is smaller than a density of the metal oxide, the metal oxide and the metal M.sup.3 react to reduce the metal M.sup.1, and the metal M.sup.2 forms an eutectic phase with the metal M.sup.1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0049] FIG. 1 shows a process chart showing a process for reducing metal M.sup.1 from a metal oxide according to an embodiment of the present disclosure.

[0050] FIG. 2 shows a diagram illustrating a process procedure of a method of reducing metal M.sup.1 from the metal oxide according to an embodiment of the present disclosure.

[0051] FIG. 3 shows a diagram and a result table showing a difference in a volatilization rate between a fluoride-based flux and a chloride-based flux.

[0052] FIG. 4 shows a diagram showing the vapor pressure of a fluoride-based flux and a chloride-based flux according to temperature.

[0053] FIG. 5 shows a photograph of a metal alloy produced according to an embodiment of the present disclosure.

[0054] FIG. 6 shows a diagram and a result table of elements analyzed using an energy dispersive spectrometer (EDS) after cutting the metal alloy produced according to an embodiment of the present disclosure.

[0055] FIG. 7 shows a result table of measuring a oxygen content present in the metal alloy produced according to Example 2 of the present disclosure using ELTRA ONH2000.

MODES OF THE INVENTION

[0056] Hereinafter, the intention, operation, and effect of the present disclosure will be described in detail through the embodiments of the present disclosure and specific descriptions, and examples to aid understanding and practice thereof, However, the following description and embodiments are presented as examples to aid understanding of the present disclosure as described above, and the scope of the invention disclosure is not limited or limited thereto.

[0057] Prior to the detailed description of the present disclosure, the terms or words used in the specification and claims should not be interpreted as limiting in a sense in the related art or a preliminary sense, and the inventor should be interpreted in a sense and a concept that are consistent with the technical concept of the present disclosure given the principle that the concepts of the terms may be appropriately defined in order to explain its own invention in its best mode.

[0058] Accordingly, it should be understood that the configuration of the embodiments described herein are only preferred embodiments of the present disclosure and are not intended to vary all of the spirit of the invention, and that there may be various equivalents and modifications that may be substituted for them at the time of this application.

[0059] In this specification, the singular expression includes the plural expression unless the context clearly dictates otherwise. In this specification, the terms comprises, includes, or has and the like are intended to designate the presence of the features, numbers, steps, components, or combinations thereof that are implemented, and are not to be understood as precluding the possibility of the presence or addition of one or more other features or numbers, steps, components or combinations thereof.

[0060] As used herein, the term loading may be used interchangeably with put, introduction, inflow, and injection in this specification, and may be understood to mean bringing or putting any material, such as a raw material, into a place where it is needed.

[0061] Hereinafter, the present disclosure will be described in detail in the order of reduction method of metal M.sup.1, a reduction system, and examples.

1. REDUCTION METHOD OF METAL M.SUP.1

[0062] A method of reducing metal M.sup.1 from a metal oxide according to the present disclosure may include: [0063] forming a molten salt of a fluoride-based flux in an cell; [0064] putting, into the cell, a metal M.sup.2 forming an eutectic phase with the metal M.sup.1, and a reducing agent including a metal M.sup.3 to produce an eutectic composition of the metal M.sup.2 and the metal M.sup.3; and [0065] reducing the metal M.sup.1 by reacting the metal oxide with the eutectic composition and forming a liquid metal alloy with the reduced metal M.sup.1 and M.sup.2.

[0066] In the method of the present disclosure, the molten salt of the fluoride-based flux may be smaller than a density of the eutectic composition of the metal M.sup.2 and the metal M.sup.3 and the metal oxide.

[0067] In the method of the present disclosure, a molten salt of the fluoride-based flux has a volatilization rate of 10% by weight or less, specifically 5% by weight or less, and more specifically 2% by weight or less for 10 hours at 1,600 C.

[0068] By using the molten salt of the fluoride-based flux, there is an environmental advantage in that toxic chlorine gas is not generated, and since its volatilization rate is low, loss of the flux during the process is small, and it is advantageous in terns of maintenance cost. In particular, when compared with a chloride-based flux, such as CaCl.sub.2, which has a volatilization rate of about 74% by weight (FIG. 3) at 1,600 C. for 10 hours, the advantage of this fluoride-based flux may be more clearly understood. Here, the volatilization rate may be measured by leaving for a certain time at a specific temperature and comparing the weight before and after leaving, but Other methods well known to those skilled in the art may be used, and numerical values in the case of using other methods may be appropriately converted from the numerical values in the present disclosure. However, since the flux of the present disclosure is used in a process of reducing a metal by reacting a metal oxide with a eutectic composition, the volatilization rate should be measured within a process temperature (900 to 1600 C.) according to the present disclosure. In particular, since the volatilization rate is higher at higher temperatures, it may be desirable to measure the volatilization rate at 1600 C., which is the highest among allowable process temperatures, to ensure process stability.

[0069] In the method of the present disclosure, the fluoride-based flux may be a fluoride-based flux of one or more metals selected from the group of alkali metals and alkaline earth metals, and determined by considering the relative density difference, a volatilization rate, convenience and safety of operation, and the like according to the target metal M.sup.1 and the reducing agent used. The fluoride-based flux may, for example, be one or more selected from the group consisting of MgF.sub.2, CaF.sub.2, SrF.sub.2, and BaF.sub.2, and specifically may be CaF.sub.2.

[0070] In the method of the present disclosure, by using an eutectic composition of metal M.sup.2 and metal M.sup.3 and a fluoride-based flux molten salt having a density lower than that of the metal oxide, In the step in which the metal oxide reacts with the eutectic composition to reduce the metal M.sup.1 and form a liquid metal alloy between the reduced metal M.sup.1 and the metal M.sup.2, and since the molten salt of the fluoride-based flux is positioned at the top of the cell, the eutectic composition and the metal oxide may not be exposed to an external environment, and inflow of oxygen from the outside may be prevented. Accordingly, a reduction process of the metal M.sup.1 is possible even in a normal air atmosphere other than an inert gas atmosphere.

[0071] In addition, by using a fluoride-based flux with a low volatilization rate, it is advantageous for large-scale industrialization because it allows harmful gases to be disloaded in an acceptable amount even in a normal air atmosphere, thereby increasing the convenience and safety of operation, and significantly lowering a degree of corrosion of equipment than used fluxes in the related art.

[0072] The metal M.sup.1 is not particularly limited, but specifically may be one selected from the group consisting of Ti, Zr, Hf, W, Fe, Ni, Zn, Co, Mn, Cr, Ta, Ga, Nb, Sn, Ag, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, and No, more specifically, one selected from the group consisting of Ti, Zr, W, Fe, Ni, Zn, Co, Mn, Cr, Ta, Er, and No, and even more specifically, one selected from the group consisting of Ti, Zr, W, Fe, Ni, Zn, Co, Mn, and Cr, and in particular, Ti, Zr, or W.

[0073] In the method of the present disclosure, the metal M.sup.2 is not limited as long as it may form an eutectic phase with the metal M.sup.1, for example, the metal M.sup.2 may be one or more selected from the group consisting of Cu, Ni, Sn, Zn, Pb, Bi, Cd, and alloys thereof, and specifically, Cu.

[0074] In the method of the present disclosure, a reducing agent including the metal M.sup.3 is not limited as long as it may reduce the metal oxide including the metal M.sup.1, for example, the metal M.sup.3 may be one or more selected from the group consisting of Ca, Mg, Al, and alloys thereof. Specifically, the metal M.sup.3 may be Mg.

[0075] In the method of the present disclosure, the metal oxide may include one or more selected from the group consisting of M.sup.1.sub.xO.sub.z and M.sup.1.sub.xM.sup.3.sub.yO.sub.z, where x and y are real numbers of 1 to 3, respectively, and z is a real number of 1 to 4.

[0076] Non-limiting examples of the above metal oxides for ease of understanding may include one selected from the group consisting of ZrO.sub.2, TiO.sub.2, MgTiO.sub.3, HfO.sub.2, Nb.sub.2O.sub.5, Dy.sub.2O.sub.3, Tb.sub.4O.sub.7, WO.sub.3, Co.sub.3O.sub.4, MnO, Cr.sub.2O.sub.3, MgO, CaO, Al.sub.2O.sub.3, Ta.sub.2O.sub.5, Ga.sub.2O.sub.3, Pb.sub.3O.sub.4, SnO, NbO, and Ag.sub.2O, or a combination of two or more of these.

[0077] When a composite oxide (M.sup.1.sub.xM.sup.3.sub.yO.sub.z) of the metal M.sup.1 and the metal M.sup.3 is used as the metal oxide, a process of reducing the metal M.sup.1 by reacting with the eutectic composition of the metal M.sup.2 and the metal M.sup.3 may be faster. According to the findings of the present disclosure, in the case of using the complex oxide (M.sup.1.sub.xM.sup.3.sub.yO.sub.z), the time required for reduction may be reduced by at least to 1/10 compared to the case of using M.sup.1.sub.xO.sub.z . That is, when the composite oxide of the metal M.sup.1 and the metal M.sup.3 is used as the metal oxide, a reaction rate between the metal oxide and the eutectic composition may be faster than when only the oxide of the metal M.sup.1 is used. In addition, in the case of using M.sup.1.sub.xM.sup.3.sub.yO.sub.z, there is an advantage in that a ratio of M.sup.1 and M.sup.2 in the liquid metal alloy produced according to the present disclosure may be more widely adjusted. Moreover, when M.sup.1.sub.xM.sup.3.sub.yO.sub.z is used, a required amount of M.sup.3 used as a reducing agent is significantly reduced compared to the case of using M.sup.1.sub.xO.sub.z . For example, when Ti is used as the metal M.sup.1 and Ca is used as the metal M.sub.3. oxide of the metal M.sup.1 may be TiO.sub.2, and the composite oxide of the metal M.sup.1 and the metal M.sup.3 may be CaTiO.sub.3.

[0078] Unlike the Kroll process in the related art, the method according to the present disclosure is different in that it uses a metal oxide instead of a metal chloride as a raw material. A raw material usually found in nature includes an oxide of the metal M.sup.1, and a pre-treatment process of substituting the metal oxide with a chloride is involved in order to use the oxide in the Kroll process. When such a pre-treatment process is performed, it itself causes an increase in process cost. Moreover, hydrochloric acid is used in the pre-treatment process of replacing metal oxide with chloride, and this process promotes corrosion of manufacturing equipment due to strong acidity, and toxic chlorine gas may be generated during the process, which may cause environmental matters. Since the method according to the present disclosure does not require a pre-treatment process for substituting the metal oxide with chloride, process cost is lower than that of the Kroll process and there are advantages in not causing environmental matters.

[0079] In the method of the present disclosure, a process of reducing the metal M.sup.1 by reacting the metal oxide with the eutectic composition may be performed in air or in fluoride. Since a density of the molten salt of the fluoride-based flux is lower than that of the eutectic composition and the metal oxide, the molten salt of the fluoride-based flux is positioned at the top of the cell, and the eutectic composition and the input metal oxide are positioned below the molten salt of the fluoride-based flux. Due to this, since the eutectic composition and the introduced metal oxide can present in a state that is not exposed to an external environment due to the molten salt of the fluoride-based flux and the cell, a process of reducing the metal M.sup.1 by reacting the metal oxide with the eutectic composition may be performed even in a normal atmosphere other than an inert gas atmosphere. Moreover, since a volatilization rate of the molten salt of the fluoride-based flux is relatively low, even when the process is performed in an atmospheric atmosphere, the generation of toxic gases is reduced, and the corrosion of equipment used in the process is significantly reduced, a harmful environment is not created for operators, and large-scale industrialization can be achieved.

[0080] In the method of the present disclosure, a method of reducing the metal M.sup.1 may be performed at least a temperature at which the fluoride-based flux can be melted, the eutectic composition can be produced, and a process of reducing metal M.sup.1 by reacting the metal oxide with the eutectic composition can be performed. For example, a process of reducing the metal M.sup.1 by reacting the metal oxide with the eutectic composition may be performed at 900 C. or more. In addition, he method can be performed at a temperature below which the molten salt of the fluoride-based flux does not evaporate excessively, and considering the energy efficiency according to the heating of the furnace, the method may be performed at 1800 C. or less, 1700 C. or less, 1600 C. or less, or 1600 C. or less. Accordingly, a process of reducing the metal M.sup.1 by reacting the metal oxide with the eutectic composition may be performed in the range of 900 to 1600 C.

[0081] As an example, when the metal M.sup.1 is Ti, the metal oxide (M.sup.1.sub.xO.sub.z ) is TiO.sub.2, the metal M.sup.2 is Cu, and the metal M.sup.3 is Ca, the metal Ti is reduced according to the following Scheme 1-1 and Scheme 1-2, and a metal M.sup.3 oxide (M.sup.3.sub.aO.sub.b) can then be separated while the liquid metal alloy CuTi is obtained. Here, a and b are a real number from 1 to 3, respectively.

2Ca+TiO.sub.2->Ti+2CaO[Scheme 1-1]

Ti+Cu+2CaO->CuTi (Alloy)+2CaO (separation)[Scheme 1-2]

[0082] As another example, when the metal M.sup.1 is Ti, the metal oxide (M.sup.1.sub.xM.sup.3.sub.yO.sub.z) is CaTiO.sub.3, the metal M.sup.2 is Cu, and the metal M.sup.3 is Ca, the metal Ti is reduced according to the following Scheme 1-1 and Scheme 1-2, and a metal M.sup.3 oxide (M.sup.3.sub.aO.sub.b) can then be separated while the liquid metal alloy CuTi is obtained.

2Ca+CaTiO.sub.3->Ti+3CaO[Scheme 2-1]

Ti+Cu+3CaO->CuTi (alloy)+3CaO (separation)[Scheme 2-2]

[0083] The metal M.sup.3 oxide (M.sup.3.sub.aO.sub.b) produced according to the above reaction is a kind of by-product, and it is necessary to continuously remove the by-products in order to enable a continuous process. The by-products may not be completely soluble in the molten salt and it may not be easy to remove the by-products or run the process continuously. The method of the present disclosure may further include forming slags of by-products generated in the process of reducing the metal M.sup.1 by reacting the metal oxide with the eutectic composition and the molten salt of the fluoride-based flux by putting a slag-forming additive. When slags are formed, viscosity is relatively reduced compared to the case where by-products and the molten salt of the fluoride-based flux are present, fluidity is increased, continuous removal of slags including by-products is possible, and furthermore, a continuous process can be made possible.

[0084] Examples of the slag-forming additive to achieve the above effect may include one or more selected from the group consisting of MgO, CaO, FeO, BaO, SiO.sub.2, and Al.sub.2O.sub.3, but are not limited thereto.

[0085] A method of reducing metal M.sup.1 from a metal oxide according to the present disclosure may further include forming a layer in which the liquid metal alloy is positioned at a bottom of the cell and separated from the eutectic composition, and continuously obtaining the liquid metal alloy through a lower portion of the cell; and forming a distinct layer on top of the eutectic composition using the slags, and continuously removing the slags through a top of the cell. By forming a layer in which the liquid metal alloy is positioned at a bottom of the cell and separated from the eutectic composition, a liquid metal alloy may be continuously tapped from a lower portion of the cell. In addition, input of the slag-forming additive causes the slag to form as a distinct layer on an upper portion of the eutectic composition, and the slag is continuously removed through the upper portion of the cell, so that by-products generated in the reduction process of metal oxides can be continuously removed. Accordingly, by continuously removing the reaction product formed when the metal oxide is input to the eutectic composition from the cell, after inputting an amount of the metal oxide, the liquid metal alloy of the metal M.sup.1 and the metal M.sup.2 may be obtained without interruption of the process by continuously inputting the metal oxide rather than all reactions being terminated. At this time, a method known to those skilled in the art may be used for continuously obtaining a liquid metal alloy through the lower portion of the cell or continuously removing slags through the upper portion of the cell.

[0086] After the slags are removed through removing the slags and the fluoride-based flux through the upper portion of the cell, the fluoride-based flux is supplemented during a process operation to maintain the balance of a reaction system and enable a continuous process. At this time, the fluoride-based flux may be continuously separated from the removed slags, and the separated fluoride-based flux may be input into the cell again.

[0087] Cooling for solidification of the obtained liquid metal alloy may be performed. Since the liquid metal alloy is in a state in which the metal M.sup.1 and the metal M.sup.2 are homogeneously mixed, the structure of the alloy obtained after solidification is greatly affected by a cooling rate of the liquid metal alloy. The cooling rate can stably form an intermetallic compound phase, in the temperature range in which the process according to the present disclosure is performed, it may be slowly cooled to room temperature at a rate of 20 C./min, so that a tissue structure in which the intermetallic compound phases of M.sup.1 and M.sup.2 are continuously connected to each other can be produced. When the cooling rate is excessively fast outside a suggested range, a structure in which a large amount of fine intermetallic compound particles are dispersed and incorporated into the metal M.sup.1 matrix is obtained, and thus there is a risk that a continuous and rapid mass transfer path of metal M.sup.1 may not be formed. When the cooling is excessively slow, the microstructural benefit is negligible, but as the time required for the process becomes excessively long, the cooling rate may be substantially 1 C./min or more, and more substantially 5 C./min or more.

[0088] The method according to the present disclosure may further include obtaining an alloy including the metal M.sup.1 and the metal M.sup.2, and then electrolytically refining the obtained alloy including the metal M.sup.1 and the metal M.sup.2 to obtain the metal M.sup.1.

[0089] Obtaining the metal M.sup.1 by performing the electrorefining may be solidifying the obtained liquid metal alloy to obtain a solid alloy, electrolytically refining the solid alloy, and recovering the metal M.sup.1 from the alloy.

[0090] In some cases, prior to electrorefining the solidified alloy, the flux that may remain in the liquid metal alloy may be removed, this can be achieved, for example, by heat treating the liquid metal alloy in a vacuum or inert gas atmosphere to cause the flux to distill off A distillation temperature (heat treatment temperature) is not particularly limited as long as the temperature is higher than a boiling point of the flux used in the system of the present disclosure, for example, the temperature may be 2,500 C. or more, and reduced pressure may be performed to lower the distillation temperature and increase efficiency. In order to effectively prevent the liquid metal alloy from being oxidized again, it may be advantageous to perform the distillation in a vacuum atmosphere and under an inert gas.

[0091] The present disclosure provides a metal alloy of the metal M.sup.1 and the metal M.sup.2 obtained by any method or combination thereof described in the specification of the present disclosure. For example, the metal alloy of the metal M.sup.1 and the metal M.sup.2 can be obtained by a method of reducing metal M.sup.1 from a metal oxide, including: forming a molten salt of a fluoride-based flux in an cell; putting, into the cell, a reducing agent including a metal M.sup.2 forming an eutectic phase with the metal M.sup.1, and a metal M.sup.3 to produce an eutectic composition of the metal M.sup.2 and the metal M.sup.3; and reducing the metal M.sup.1 by reacting the metal oxide with the eutectic composition and forming a liquid metal alloy with the reduced metal M.sup.1 and M.sup.2. For example, the metal alloy of the metal M.sup.1 and the metal M.sup.2 may be made in an atmosphere or obtained from a process performed in a range of 900 to 1600 C. For example, the metal alloy of the metal M.sup.1 and the metal M.sup.2 may be obtained by a method including forming slags of the molten salt and a by-product generated in a process of reducing the metal M.sup.1 by adding a slag-forming additive to react the metal oxide with the eutectic composition. In addition, the metal alloy of the metal M.sup.1 and the metal M.sup.2 of the present disclosure may be obtained by any method or a combination thereof described in the specification of the present disclosure.

[0092] In one embodiment, the metal alloy of the metal M.sup.1 and the metal M.sup.2 is a high-grade metal alloy with a residual content of 0.1% by weight or less, specifically 0.01% by weight or less, and more specifically 0.001% by weight or less, based on a total weight of the metal alloy. In addition, the metal alloy of the metal M.sup.1 and the metal M.sup.2 is a high-grade metal alloy with an oxygen content of 1,800 ppm or less, specifically 1,500 ppm or less, and more specifically 1,200 ppm or less.

[0093] In addition, in a liquid alloy (M.sup.1 and M.sup.2 are liquid metal alloys) obtained according to the method of the present disclosure, the metal alloy itself may be used as a final product. M.sup.1 is often used industrially in the form of an alloy, and when M.sup.1 can be produced with only a single metal, as in the Kroll process in the related art, a post-processing process for forming an alloy with another metal may be required. However, the present disclosure has high process efficiency in that a final product may be obtained in the form of a metal alloy of M.sup.1 and M.sup.2 simultaneously with reduction without such a post-treatment process. Moreover, the reduced metal produced through the Kroll process in the related art has a low production of high grade (grade 1) metal having a low oxygen content and a relatively high residual oxygen content. Therefore, even when a metal alloy is produced using the reduced metal produced by the Kroll process, there is a limit in that the residual oxygen content is high. On the other hand, most of the metal alloys produced according to the present disclosure have a very low oxygen content and are of high quality grade. For example, when M.sup.1 is Ti, the method according to the present disclosure yields a high-grade metal as high as 98% or more, but it is known that the crawl process in the related art yields less than 50% of high-grade metal, and through this, superiority of the present disclosure can be more clearly understood.

2. SYSTEM FOR REDUCING M.SUP.1

[0094] A system for reducing metal M.sup.1 from a metal oxide according to the present disclosure may include: [0095] an cell; [0096] a molten salt of a fluoride-based flux positioned in the cell; [0097] an eutectic composition of metal M.sup.2 and metal M.sup.3 positioned at a lower portion of the molten salt; and [0098] a liquid metal alloy of the metal M.sup.1 and the metal M.sup.2 positioned below the eutectic composition; [0099] wherein a density of the molten salt may be smaller than a density of the metal oxide, [0100] the metal oxide and the metal M.sup.3 may react to reduce the metal M.sup.1, and [0101] the metal M.sup.2 may form an eutectic phase with the metal M.sup.1.

[0102] In one embodiment, the cell may be an electrolytic reduction cell or the like, a high-frequency melting furnace may be used to achieve a desired temperature range, or an electric furnace may be used depending on a target metal alloy, but is not limited thereto. Considering a reaction temperature range, reactivity, and the like, all cells and furnaces that are easy for a person skilled in the art may be used.

[0103] In one embodiment, a mass ratio of the molten salt of the fluoride-based flux to the reaction by-product may be 5:1 to 2:1, preferably 3:1, but is not limited thereto, for smooth separation of the liquid metal alloy and the reaction by-product.

[0104] In one embodiment, the flux may further include an oxide of one or two or more metals selected from an alkali metal and an alkaline earth metal group as a reactive additive. A content of the reactive additive may be 0.1 to 25% by weight based on a total weight of the flux. The reactive additive may include, but are not limited to, LiO, NaO, SrO, CsO, KO, CaO, BaO, or mixtures thereof. The reactive additive contained in the flux may enable easier reduction of a metal oxide contained in a raw material module.

[0105] In one embodiment, a cell similar to that of FIG. 1 may be used to perform a production method an alloy metal of the present disclosure. For example, The fluoride-based flux is loaded into an cell 1 and melted to form a molten salt 5 and a reducing agent including metal M.sup.2 forming an eutectic phase with metal M.sup.1, and metal M.sup.3 is input into an cell to produce an eutectic composition 6 of the metal M.sup.2 and the metal M.sup.3. Since the density of the molten salt of the fluoride-based flux is less than that of the eutectic composition, the molten salt 5 of the fluoride-based flux is positioned on the eutectic composition 6. Thereafter, a metal oxide 10 is loaded into the cell using the raw material input device 1, and the oxide is reacted with the eutectic composition 6 to prepare a liquid metal alloy 7 of the metal M.sup.1 and the metal M.sup.2, and after the reaction is completed, a slag-forming additive 9 is input into the reaction by-product positioned between the liquid metal alloy and the flux to slag the by-product. After that, the liquid metal alloy 7 is obtained through a tapping portion 7 connected to a lower portion of the cell through the lower portion of the cell. Since the slags are positioned at a upper portion of the cell, about 50-90% of the slags are removed by tilting the cell, and a new fluoride-based flux is input into about 10 to 50% of residual slags through an flux input device 2 to form a new flux layer. Thereafter, again, the metal oxide 10 is loaded into the cell using the raw material input device 1 and reacted with the eutectic composition 6, and a process of producing the liquid metal alloy 7 may be repeated. In all stages of the process, such as before removing slags or tilting the cell to remove slags, the liquid metal alloy 7 produced in the lower portion of the cell is continuously obtained through the tapping portion 8 in the lower portion of the cell. The cell may use, for example, a high-frequency melting furnace 3 to facilitate stirring, but is not limited thereto.

3. EXAMPLES

[0106] Hereinafter, examples will be described in detail, through which the action and effect of the present disclosure will be demonstrated. However, the following examples are only presented as examples of the invention disclosure, and the scope of the invention disclosure is not determined thereby.

Example 1

[0107] A system as shown in FIG. 1 was used and proceeded according to a process sequence of FIG. 2. Flux CaF.sub.2 (40.8 g) was weighed in a resistance heating furnace, input into an cell, and then heated to about 1415 C to produce a molten salt of a fluoride-based flux (FIG. 2A).

[0108] 52.8 g and 72.3 g of Cu(s) and Ca(s) were weighed, input into an cell, and melted to produce an eutectic composition (FIG. 2B).

[0109] 72.1 g of TiO.sub.2 (average particle size of 100 m) as a metal oxide was weighed and reacted for 10 hours (FIGS. 2c and 2d).

[0110] In order to remove by-products, 200 g of Al.sub.2O.sub.3 powder and 100 g of CaO as slag-forming additives were input to slags (FIG. 2E), and then slowly cooled in the furnace. The process was performed in an air atmosphere.

Example 2

[0111] A system as shown in FIG. 1 was used and proceeded according to a process sequence of FIG. 2. Flux CaF.sub.2 (40.8 g) was weighed in a resistance heating furnace, input into an cell, and then heated to about 1415 C. to produce a molten salt of a fluoride-based flux (FIG. 2A).

[0112] 60 g and 65.5 g of Cu(s) and Ca(s) were weighed, input into a cell, and melted to produce an eutectic composition (FIG. 2B).

[0113] 111 g of CaTiO.sub.3 as a metal oxide was weighed and reacted for 2 hours (FIGS. 2c and 2d).

[0114] In order to remove by-products, 200 g of Al.sub.2O.sub.3 powder and 100 g of CaO as slag-forming additives were input to slags (FIG. 2E), and then slowly cooled in the furnace. The process was performed in an air atmosphere.

Experimental Example 1

[0115] A volatilization rate of a fluoride-based flux and a chloride-based flux were measured. 500 g of each flux (weight before loading) was weighed and input into a crucible, and weight (weight after loading) of the flux after loading the crucible to a melting furnace and leaving the flux at 1,600 C. for 10 hours was measured. The volatilization rate was evaluated using the following method.

Volatilization rate: (weight before loadingweight after loading)/(weight before loading)100%

[0116] As a result, it was confirmed that CaF.sub.2 used as the fluoride-based flux showed a low volatilization rate of 1.8% by weight, but CaCl.sub.2, a chloride-based flux, showed a high volatilization rate of about 74% by weight (FIG. 3).

[0117] Regarding a volatilization rate of CaF.sub.2, a fluoride-based flux, and a volatilization rate of CaCl.sub.2, a chloride-based flux, measured in each temperature range, it may be seen that a vapor pressure of the fluoride-based flux is remarkably low based on a process temperature at which this process is performed (FIG. 4), indicating that the volatilization rate in the process of the fluoride-based flux is remarkably low.

[0118] From this, it is preferable to use a fluoride-based flux having a low volatilization rate for an efficient process as described above.

Experimental Example 2

[0119] The properties of the alloys obtained in Examples 1 and 2 were evaluated using the following method.

Recovery rate: 100{(1st weight2nd weight)/2nd weight100%} [0120] Residual impurity content: The produced alloy was cut and the inside of the alloy was confirmed using an energy dispersion spectrum. [0121] Oxygen content: The oxygen content present in the alloy was measured using an ELTRA ONH2000.

TABLE-US-00001 TABLE 1 Results of energy dispersion spectrum Ti Cu Oxygen 1st 2nd Recovery (% by (% by content weight weight rate (%) weight) weight) (ppm) Example 1 96 83.9 87.4 27.3 72.7 1162.69 Example 2 99.16 95.86 96.7 40.81 59.19 1126.08 *1st weight: Total amount of Cu put into the initial electrolytic bath + Chemical theoretical reduction amount of Ti included in metal oxide. **1st weight: Total amount of CuTi obtained

[0122] From the results of Table 1, it may be seen that the alloys of Examples produced according to the present disclosure showed a high recovery rate, and that a high-purity alloy was obtained that was substantially free of metal or oxygen used as a reducing agent. That is, it was confirmed that, unlike a presenting process, which was possible only in an inert gas atmosphere as above, even though the process proceeded in an air atmosphere, the recovery rate of the target metal was better and the oxygen content was significantly lower.

[0123] Although the present disclosure has been described with reference to embodiments, those skilled in the art will be able to make various applications and modifications within the scope of the present disclosure based on the above information.