JP2008195969A - Method for producing alloy ingot by molten salt electrolysis using ESR heating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing an alloy ingot by molten salt electrolysis using a metal oxide as a raw material.
A method for producing an alloy ingot by molten salt electrolysis, in which a metal constituting an alloy matrix and an oxide of a metal constituting an alloy component are dissolved in the molten salt, and the molten salt is energized. A method for producing an alloy ingot, comprising subjecting the oxide to molten salt electrolysis.
[Selection] Figure 1

Description

  The present invention relates to a method for producing an alloy from a metal oxide by molten salt electrolysis.

  Conventionally, titanium metal has been widely used for aircraft fuselage materials and components, and in recent years, application development has progressed and it has been widely used for building materials, roads, sports equipment, and the like. Conventionally, metallic titanium has been produced by a crawl method in which titanium tetrachloride is reduced with molten magnesium to obtain sponge titanium, and production costs have been reduced by accumulating various improvements. However, since the crawl method is a batch process that repeats a series of operations discontinuously, there is a limit to the efficiency.

  For the above situation, the FFC method (for example, refer to Patent Document 1) in which titanium oxide is directly reduced to metal titanium by reducing titanium oxide in molten salt, or metal calcium in molten salt. A technique is disclosed in which metal titanium is recovered by reduction, and the by-produced calcium oxide is chlorinated to calcium chloride, and this is subjected to molten salt electrolysis to recover metal calcium (see, for example, Patent Document 2). Both of these techniques are attracting attention as methods for producing titanium metal using titanium oxide as a starting material.

  However, in any method, since the titanium produced is a solid titanium having a low purity containing a salt bath, in order to obtain a titanium ingot, the salt bath is separated and removed from the electrolytically produced solid titanium and further dissolved. A process is required.

  In order to solve the above problems, the molten salt in which titanium oxide is dissolved is heated to a temperature higher than the melting point of titanium, the molten salt is electrolyzed to form molten titanium, and this is settled and immersed in the bottom of the electrolytic layer to form a titanium ingot. A technique for directly manufacturing is disclosed (for example, see Patent Document 3).

  However, in this method, although a titanium ingot with high purity can be obtained, the current efficiency of molten salt electrolysis is low, and improvement has been demanded. Thus, a technique for efficiently producing a metal titanium ingot using titanium oxide as a raw material is desired.

  Furthermore, in the manufacture of titanium alloy, it is manufactured by briquetting sponge titanium manufactured by the crawl method and electron beam melting or combining the briquettes to constitute an electrode and vacuum arc melting, but there are a plurality of steps. Cost improvement is required over a wide range. In any of the above-mentioned documents, there is no description relating to alloy production. Thus, there is a need for a technique for efficiently producing a titanium alloy ingot using titanium oxide as a starting material.

WO99 / 064638 JP 2003-129268 A Japanese Patent Application Laid-Open No. 06-146049

  An object of the present invention is to provide a method for efficiently producing an alloy ingot by molten salt electrolysis using a metal oxide as a raw material.

  As a result of intensive studies in view of such circumstances, a method for producing an alloy ingot by molten salt electrolysis, in which the parent phase metal of the alloy (the metal constituting the main phase of the main component) and the component metal (the parent phase) A carbon electrode immersed in the molten salt and an alloy ingot disposed at the bottom of the vessel for performing the molten salt electrolysis while dissolving each oxide of the metal constituting the alloy component to be added in the molten salt It has been found that an alloy ingot can be efficiently produced by energization heating in the meantime, and the present invention has been completed.

  That is, the method for producing an alloy ingot according to the present invention is a method for producing an alloy ingot by molten salt electrolysis, in which a metal constituting the parent phase of the alloy and an oxide of each of the metals constituting the alloy component are fused. And the molten salt is subjected to molten salt electrolysis by applying current to the molten salt.

  Also, the method for producing an alloy ingot according to the present invention is characterized in that electricity is passed between the top of the alloy ingot as a cathode disposed at the bottom of the cathode chamber and the anode disposed in the anode chamber. .

  By using the above-described molten salt electrolytic cell and electrolysis method according to the present invention, an alloy ingot having a high purity can be efficiently produced while maintaining a high current efficiency.

  By using the above-mentioned method according to the present invention, an effect that an alloy ingot having a high melting point and high activity metal such as a titanium alloy as a parent phase metal can be efficiently produced using a metal oxide as a raw material. It plays.

The best embodiment of the present invention will be described below.
FIG. 1 is a schematic view showing a molten salt electrolyzer according to the present invention. Reference numeral 1 denotes an electrolytic container composed of a water-cooled copper wall for cooling. In the electrolytic container 1, a molten salt bath 2 heated to a melting point or higher of a metal to be melted is held. In the present invention, the molten salt bath 2 is preferably composed of calcium oxide and calcium fluoride.

  The molten salt bath 2 is held in a molten state by a heating means (not shown), and the molten salt bath 2 itself becomes a resistance and generates heat by applying a voltage at the time of molten salt electrolysis. It can also be. An anode 3 is immersed in the bath surface of the molten salt bath 2, and an ingot 4 that functions as a cathode is inserted in the bottom of the molten salt bath 2. A molten metal pool 5 is formed at the top of the ingot 4 in contact with the molten salt bath 2.

  Reference numeral 6 denotes a lid that shields the electrolytic vessel 1 from the outside. The lid 6 is provided with a raw material supply nozzle 7 for producing an alloy ingot to be melted. From this raw material supply nozzle 7, a raw material for producing an alloy is supplied into the electrolytic vessel 1. The raw material consists of an oxide of the metal (matrix metal) that constitutes the parent phase, which is the main component of the alloy, and an oxide of the metal (component metal) that constitutes the alloy component to be added. Put into the container 1. The lid 6 is provided with an inert gas supply nozzle 8 for supplying an inert gas and an exhaust nozzle 9 for discharging the gas in the electrolytic vessel 1. A space 10 is provided above the molten salt bath 2.

  In the present invention, the molten salt bath 2 is dissolved in the molten salt bath 2 while dissolving the oxide of the matrix metal and the oxide of the component metal, which are raw materials of the alloy ingot, in the molten salt bath 2 kept at a high temperature. The temperature of the molten salt bath 2 is maintained by energizing between the anode immersed in 2 and the top of the ingot 4 inserted and held at the bottom of the molten salt electrolysis tank holding the molten salt bath 2. On the other hand, both supplied oxides can be reduced to metal and combined with the molten metal pool 5 formed at the top of the ingot 4 disposed at the bottom of the electrolytic vessel 1.

The anode 3 immersed in the molten salt bath 2 is preferably composed of carbon. By using the anode 3 made of carbon, the oxygen in the oxide of the matrix metal and the oxide of the component metal dissolved in the molten salt bath 2 is expressed by the following formulas (1) and (2). And can be separated out of the system as CO and CO ₂ gas.

C + O ²⁻ = CO + 2e ⁻ (1)
C + 2O ²⁻ = CO ₂ + 4e ⁻ (2)

  In the present invention, it is preferable to use the top of the ingot 4 immersed in the molten salt bath 2 or inserted and held at the bottom of the molten salt electrolytic cell as the cathode. With such an arrangement, there is an effect that the parent phase metal and the component metal generated at the top of the ingot 4 can be combined with the ingot 4. Here, the ingot 4 to be inserted and arranged at the bottom of the reaction vessel 1 at the start of the molten salt electrolysis is not limited as long as it is a titanium material, but is an alloy that matches the composition of the alloy ingot generated by the molten salt electrolysis. By configuring in advance, there is an effect that the entire melted ingot can be used as a titanium alloy ingot.

The oxide of the matrix metal and the oxide of the component metal supplied to the molten salt bath 2 are dissolved to generate matrix metal ions M ^{n +} and component metal ions X ^{m +, respectively,} at the top of the ingot 4 As shown, the matrix metal M and the component metal X generated by the reaction expressed by the formulas (3) and (4) are dissolved to reduce the alloy.

M ^{n +} + ne ⁻ = M (3)
^{X m + + me - = X} ··· (4)
(Here, m and n are positive integers.)

  It is preferable to keep the top part of the ingot 4 in a molten state so that the molten alloy produced by reduction is united with the top part of the original ingot 4. The molten metal pool 5 formed on the top of the ingot 4 can be held relatively easily by applying high-frequency power from the outside of the molten salt electrolytic cell.

  By holding the top of the ingot 4 in such a molten state, the matrix metal M and the component metal X generated by the electrode reaction are combined with the molten metal pool 5 formed at the top of the ingot 4. And uniform ingots can be produced.

  The parent metal of the alloy that can be produced in the present invention can be suitably applied to so-called refractory metals such as titanium, niobium, and tantalum. Moreover, the component metal of the alloy can be appropriately selected from aluminum, vanadium, nickel, iron, silicon, molybdenum and the like.

  Therefore, an alloy such as a titanium-aluminum alloy, a titanium-nickel alloy, or a titanium-iron alloy can be suitably manufactured by appropriately combining these metal oxides as raw materials.

  As described above, it is preferable to use an oxide corresponding to a parent phase metal and a component metal as a raw material used for manufacturing the alloy of the present invention. For example, when manufacturing a titanium alloy, it is preferable to use metal titanium oxide, niobium pentoxide for a niobium alloy, and tantalum pentoxide for a tantalum alloy, respectively.

  Component metals of the alloy can be appropriately selected from oxides such as aluminum, vanadium, nickel, iron, silicon, and molybdenum. In addition, the blending amount of the component metal oxide may be appropriately selected depending on the composition of the target alloy.

  The oxide raw material of the parent phase metal constituting the alloy is preferably granular or granular. When producing a titanium alloy, titanium oxide is preferably used, and titanium oxide having a particle size range of 0.1 mm to 1 mm is preferably used. By using titanium oxide having such a particle size range as a raw material, it can be efficiently supplied into the molten salt by, for example, an injection method.

  It is preferable to use a raw material having a particle size range of 0.1 mm to 1 mm for the component metals constituting the alloy. By using a component metal having such a particle size, it can be efficiently dissolved in the molten salt.

For the molten salt used in the present invention, it is preferable to select components and compositions so that the alloy raw materials can be easily dissolved. For example, when a titanium alloy is melted using the present invention, it is preferable to use a composite salt composed of calcium oxide and calcium fluoride. By using the composite molten salt, the matrix metal oxide and the component metal oxide can be efficiently dissolved.
The compounding ratio of calcium fluoride to calcium oxide constituting the composite salt can be selected as appropriate depending on the type and blending amount of the oxide of the parent phase metal and the component metal oxide introduced into the molten salt. In the invention, it is preferable to select from the range of 1/1 to 1/3.

  By using the complex salt, the melting point of the complex salt can be adjusted to 1350 ° C to 1500 ° C. As a result, the energy required for heating to maintain an electrolysis temperature suitable for molten salt electrolysis can be suppressed to a low level.

  Further, the added amount of the component metal oxide constituting the alloy may be supplied to the molten salt in an amount corresponding to the composition of the target alloy.

  An alloy ingot can be continuously produced by previously mixing a predetermined amount of oxides corresponding to the parent phase metal and the component metal constituting the alloy or supplying them separately to the molten salt independently.

  Next, a preferable apparatus configuration of the molten salt electrolyzer used when carrying out the invention of the present application will be described, and a preferable mode in the case of melting an alloy ingot using this will be described below with reference to FIG.

The electrolytic vessel 1 constituting the electrolytic bath molten salt electrolytic bath F is preferably composed of water-cooled copper so as to withstand the hot molten salt bath 2. When the electrolytic vessel 1 is composed of water-cooled copper, the surface of the water-cooled copper wall in contact with the molten salt bath 2 has a solid phase (hereinafter referred to as “molten salt self-coat layer”) of the molten salt bath 2 not shown. Is formed). The said molten salt self-coat layer exhibits the preferable effect that the water-cooled copper wall which comprises the electrolytic vessel 1 from the molten salt bath 2 in high temperature can be protected effectively.

  The thickness of the molten salt self-coat layer is determined from the balance between heat input to and extraction from the water-cooled copper wall constituting the electrolytic vessel 1, but in the present invention, the thickness of the molten salt self-coat layer is 2 to 5 mm. It is preferable to control to the extent.

  As the molten salt self-coat layer is thicker, the protective function is increased, but the temperature of the molten salt bath 2 is lowered, which is not preferable. On the other hand, if the molten salt self-coat layer is thin, the function as a protective layer is deteriorated, for example, the hot molten salt bath 2 damages the water-cooled copper wall, which is not preferable. Therefore, the molten salt self-coat layer is preferably controlled to have a thickness within the above range.

  The electrolysis vessel 1 is configured to be blocked from the atmosphere by a lid 6, and the lid 6 is preferably provided with an inert gas supply nozzle 8 and an exhaust nozzle 9 for adjusting the atmosphere. By taking the above apparatus configuration, the inside of the molten salt electrolytic cell F can be maintained in an inert gas atmosphere. As a result, wear of the anode 3 made of carbon can be effectively suppressed.

In the space 10 on the molten salt bath 2, CO and CO ₂ gas generated by the reduction reaction are present. The CO ₂ gas upon contact with the carbon constituting the anode 3, the tendency may anode 3 undergoes a carbon solution reaction of the CO ₂ gas with temperature is subjected to wear is known to be susceptible to occur at lower temperatures Yes.

Therefore, it is preferable that the lid portion 6 is formed of a heat insulating wall so that the temperature of the space portion 10 is maintained at 500 ° C. or higher where carbon solution reaction is unlikely to occur. More preferably, the anode 3 is covered with a ceramic or quartz tube or the like so as not to come into contact with the CO ₂ gas generated from the molten salt bath 2.

Electrode (Anode / Cathode)
The anode 3 is disposed so as to penetrate downward from the top of the lid 6 and is immersed in a molten salt bath 2 held in the container 1. Further, the anode 3 can be made to function effectively as a reducing agent for oxygen ions dissolved in the molten salt bath 2 by being composed of graphite.

  Since the carbon constituting the anode 3 functions as a reducing agent, it is consumed in proportion to the operation time. For this reason, with the passage of time, there is a tendency to gradually deviate from the molten metal pool 5 constituting the cathode 4, and the voltage necessary for flowing a predetermined current increases. Therefore, it is preferable to configure the anode 3 so that it can move downward as the operating time elapses.

  As described above, the molten salt used in the present invention includes an oxide corresponding to the alloy component metal in addition to calcium fluoride and calcium oxide, so that the resistance value of the molten salt is higher than before. Can be set to

  Therefore, even if the same voltage as before is applied, high Joule heat can be generated, and the molten salt bath 2 can be held in a molten state relatively easily.

Further, the parent phase metal oxide and the component metal oxide supplied into the molten salt bath 2 dissolve in the molten salt bath 2 in a short time, and are separated into metal ions and oxygen ions, respectively. Is reduced by the carbon constituting the anode 3 to become CO and CO ₂ gas and discharged out of the system through the nozzle 9. On the other hand, the metal ions are generated from the molten metal pool 5 and merged with the molten metal pool 5, and then cooled from the water-cooled copper wall constituting the electrolytic vessel 1 and extracted as an alloy ingot.

Oxides corresponding to the parent phase metal and the component metal, which are the raw material of the raw material supply alloy ingot, can be supplied into the molten salt bath 2 from the raw material supply nozzle 7 provided on the side wall of the lid 6. The raw material may be preheated in advance. As a result, it is possible to effectively suppress the temperature drop of the molten salt bath 2 that may occur when the raw material is charged.

  Further, when the oxide corresponding to the matrix metal such as titanium oxide is in the form of powder or granules, it can be efficiently supplied into the molten salt bath 2 by using the injection method together.

An ingot 4 also serving as a cathode is inserted and disposed at the bottom of the electrolytic cell 1 for drawing the generated ingot . Moreover, it is preferable that the molten metal pool 5 is formed at the top of the ingot 4.

  The molten metal pool 5 is formed by heating when the molten salt bath 2 generates resistance by applying a direct current between the anode 3 immersed in the molten salt bath 2 and the ingot 4 also serving as the cathode. In addition, by arranging a high frequency coil outside the electrolytic vessel 1 corresponding to the molten metal pool 5, high frequency power can be applied to the molten metal pool 5. As a result, the molten metal pool 5 can be maintained at a predetermined temperature.

  The parent phase metal ions and alloy component metal ions dissolved in the molten salt are supplied with electrons from the molten metal pool 5 constituting the cathode as described above, and produce titanium metal and alloy component metals. The produced titanium metal and alloy component metal are combined with the molten metal pool 5 to produce an alloy.

  The titanium metal and the alloy component metal produced in the molten salt bath 2 merge with the molten metal pool 5 formed at the top of the ingot 4, and the molten region of the molten metal pool 5 rises.

  Therefore, it is preferable to operate a drawing device (not shown) engaged with the lower end portion of the ingot 4 to continuously draw the ingot 4 downward at a speed commensurate with the production rate of the molten alloy. By performing the above-described operation, an alloy ingot can be continuously produced while keeping the level of the molten metal pool 5 constant.

  The melted alloy ingot can be cut at an appropriate length into a product ingot. Another ingot can be melted by newly engaging a drawing device with the cut surface of the remaining ingot.

  By using the molten salt electrolysis method according to the present embodiment described above or the present invention, there is an effect that an alloy ingot such as a titanium-aluminum alloy can be efficiently manufactured.

[Example 1]
A titanium-aluminum alloy was produced by molten salt electrolysis using the apparatus configuration of FIG. 1 under the following conditions.
1) Apparatus configuration Electrolytic container (side wall): Cylindrical water-cooled copper wall (outer diameter: 180 mm)
Anode 1: Graphite (outer diameter: 60 mm)
Cathode 2: Pure titanium ingot (outer diameter: 110 mm, JIS Class 1 equivalent)
2) Amount of current between anode and cathode: 10-20KA
3) Molten salt bath Composition: CaF ₂ : CaO = 5: 2 (weight ratio)
Bath temperature: 1700-2000 ° C
4) Titanium oxide (matrix metal material)
Purity: 99%
Particle size: 0.1 mm to 1.0 mm
Input amount: 10% of molten salt bath weight
5) Aluminum oxide (component metal material)
Purity: 99%
Particle size: 0.005mm to 1mm
6) Mixing ratio of titanium oxide and aluminum oxide Composition: TiO ₂ : Al ₂ O ₃ = 1: 2 to 1: 4 (weight ratio)
7) Results Molten salt electrolysis was performed twice under the above conditions, and titanium-aluminum alloy ingots were produced in each test. When the produced titanium ingot was analyzed, it was confirmed that a titanium-aluminum alloy having a composition as shown in Table 1 was produced. In addition, the current efficiency was 37% to 50%, and it was confirmed that the current efficiency was higher than that of the conventional technique.

[Comparative Example 1]
1, the mixing ratio of TiO ₂ and Al ₂ O ₃ is not changed, and the mixing ratio of CaF ₂ : CaO: Al ₂ O ₃ is changed from 5: 2: 3 to 6: 2: 2 (weight ratio). The molten salt electrolysis was performed under the same conditions as in Example 1 except that the alloy ingot was manufactured. When the manufactured titanium ingot was analyzed, the oxygen and carbon contents were high, and the quality characteristics of the pure titanium ingot could not be satisfied. Moreover, the current efficiency was less than 30%, which was not a satisfactory result.

  An alloy ingot having a high melting point and high activity metal such as titanium as a parent phase metal can be efficiently produced, and the cost of producing such an alloy can be reduced.

It is a schematic cross section of the alloy manufacturing apparatus by molten salt electrolysis of this invention.

Explanation of symbols

F Molten salt electrolysis apparatus 1 Electrolysis vessel 2 Molten salt bath 3 Anode 4 Cathode (Ingot)
5 Molten metal pool 6 Lid 7 Raw material supply nozzle 8 Inert gas supply nozzle 9 Exhaust nozzle 10 Space

Claims (5)

  A method for producing an alloy ingot by molten salt electrolysis, wherein a metal constituting the parent phase of the alloy (hereinafter sometimes referred to as “parent phase metal”) and a metal constituting the alloy component (hereinafter referred to as “component metal”) A method for producing an alloy ingot, in which each oxide is dissolved in a molten salt, and the molten salt is subjected to molten salt electrolysis by energizing the molten salt.   The method for producing an alloy ingot according to claim 1, wherein the molten salt is composed of calcium oxide and calcium fluoride.   2. The method for producing an alloy ingot according to claim 1, wherein the matrix metal is any one of titanium, niobium, and tantalum.   The method for producing an alloy ingot according to claim 1, wherein the component metal is at least one selected from aluminum, vanadium, nickel, iron, silicon, and molybdenum. 2. An electric current is passed between a carbon electrode constituting an anode immersed in the molten salt and an alloy ingot constituting a cathode arranged at the bottom of a water-cooled copper container holding the molten salt. The manufacturing method of the alloy ingot in any one of -4.

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