JPS61253391A - Method and apparatus for manufacturing praseodymiumi-iron or praseodymium-neodymium-iron alloy - Google Patents

Abstract

PURPOSE:To manufacture a Pr-Fe or Pr-Nd-Fe alloy by electrolytically reducing a praseodymium compound or praseodymium and neodymium compounds in an electrolytic molten salt bath with an iron cathode and a carbon anode. CONSTITUTION:A praseodymium compound or praseodymium and neodymium compounds are electrolytically reduced in an electrolytic molten salt both with an iron cathode and a cardon anode. Produced praseodymium or praseodymium and neodymium are deposited on the cathode and alloyed with the iron forming the cathode to manufacture a praseodymium-iron or praseodymium-neodymium- iron alloy.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for producing praseodymium-iron or praseodymium-neodymium-iron alloy and an apparatus for producing the same.
A praseodymium-iron alloy or praseodymium-neodymium-iron alloy with a high content of praseodymium or praseodymium and neodymium and a low content of harmful impurities and inclusions, especially suitable as a master alloy for magnetic materials such as high-performance permanent magnets. The present invention relates to a method and apparatus for continuously producing an alloy.

(Background of the invention) Recently, it has become possible to use
Moreover, rare earth-iron based and rare earth-iron-boron based permanent magnets are attracting attention as high-performance magnets with superior magnetic properties than hard ferrite. Among them, neodymium-iron-boron magnets have a maximum energy product (BH)max of 36
It is recognized that it is even higher than MGOe and is extremely superior in terms of specific gravity and mechanical strength (for example, JP-A-5
9-46008). Instead of neodymium, it is possible to use praseodymium or praseodymium-neodymium, which is expected to have the same level of magnetic properties. especially,
Praseodymium-neodymium exists as an unseparated mixture before its raw material is final separated into rare earth elemental compounds;
It is cheaper than neodymium alone and has high performance as a permanent magnet [95th Annual Meeting of the Japan Institute of Metals]
1984) Summary Collection, p. 250], and the demand is expected to increase in the future.

By the way, the following four methods are generally known as methods for producing alloys of rare earth metals and high melting point metals.

First, rare earth metals are produced by molten salt electrolysis or reduction with active metals (removed as rare earth metals or alloys thereof), mixed with other metals, and dissolved.
This is a method of alloying. However, among these methods, when chloride is used as the raw material for electrolysis, handling of the raw material is difficult, and the operation is batch-type. There is a problem with that. Furthermore, when oxides of rare earth metals are electrolyzed using a fluoride electrolytic bath, the solubility of such oxide raw materials in the electrolytic bath is low, which makes continuous operation difficult, and sludge is formed at the bottom of the electrolytic layer. There is an inherent problem. In particular, in order to achieve mass production and continuous operation, it is preferable that the metal produced be in a liquid state, but in the case of high melting point rare earth metals, it is necessary to raise the electrolysis temperature to achieve this, and impurities such as furnace materials is likely to be mixed into the produced metal, making it impractical.

On the other hand, the above method, which includes the step of reducing rare earth metal raw materials using active metals, has problems in that the operation is batch-type and is not suitable for continuous large-scale production. use, requires expensive materials for reduction equipment,
Further, there are inherent problems such as the need for a step to remove residual reducing agent components.

The second method is to mix a rare earth metal compound and a metal compound to be alloyed and reduce the mixture with an appropriate compound (for example, calcium hydride in the case of producing an Sm-Co alloy).
However, this method has problems, such as the use of an expensive reducing agent and the fact that the operation is batch-type, making it unsuitable for continuous large-scale production.

Furthermore, thirdly, a method in which a rare earth metal compound and a metal compound to be alloyed are dissolved in an electrolytic bath by molten salt electrolysis, and both compounds are electrolytically reduced and deposited as an alloy on a cathode (for example, Japanese Patent No. 3298935), but this method also has the following problems. In other words, it is difficult to stabilize the composition of the alloy deposited on the cathode over a long period of time during the electrolytic process, and when oxides are used as raw materials, the solubility of the raw materials in the electrolytic bath is low, making continuous operation difficult. There are inherent problems such as difficulty in

The fourth method is the so-called consumable electrode method, in which the metal to be alloyed is used as a solid cathode, while the rare earth metal compound is dissolved in an electrolytic bath of a suitable molten salt. A method in which the target rare earth metal is deposited on the cathode and alloyed with the cathode metal (rU,
, Bureau of Mines, Report of Investigations, Case 7146 (1968),
Patent No. 837401, Patent No. 967389).

However, even this method has the following drawbacks. In other words, when an oxide raw material is used as a rare earth metal compound to be electrolytically reduced, as mentioned above, there are problems such as low solubility of the oxide in the electrolytic bath and the formation of sludge. There is a problem, and high temperature operation is required to avoid this problem.

However, when this high-temperature operation is carried out, impurities from the furnace materials and the like increase, causing a new problem that deteriorates the quality of the produced alloy.

Moreover, in this consumable electrode method, the produced alloy is collected in a batch manner, and is not continuous, which has the inherent problem of being unsuitable for mass production.

Under these circumstances, metal praseodymium and alloy praseodymium
Neodymium has so far had almost no use, and although the first method described above is considered as a method for producing it, no industrial production method has been fully established. Therefore, an industrial method for producing praseodymium-iron or praseodymium-neodymium-iron alloy, which is suitable as a raw material for magnetic materials such as high-performance permanent magnets as described above, has not been sufficiently established.

Laboratory-scale electrowinning of these metal praseodymium and alloy praseodymium-neodymium (didymium containing lanthanum) is described in E. Morris et al. (rU, S., Bureau of Mines, Report of Investigations). ” Patient 6957 (1967L) attempted to use oxide raw materials, but the commercially available oxide of praseodymium
It is a non-stoichiometric compound containing a slight excess of oxygen called r60+t, and this causes abnormal consumption of anode carbon during electrolysis, similar to when CeO is electrolyzed. Therefore, E. Morris et al. By carbon reduction, p
r60++ is converted into Prt03 and used as a raw material, but this method becomes complicated in terms of process and is not considered to be an industrially advantageous method.

Furthermore, JP-A-60-46346 discloses a method for reducing a raw material mixture of neodymium chloride or fluoride and praseodymium fluoride using a reducing agent metal in the presence of iron. However, due to the use of reducing metals, there are problems with the rise in manufacturing costs, the formation of slag, and a decrease in the quality of the produced alloy due to the contamination of slag or residual reducing agent components. ,
There is a problem in that it is difficult to continuously produce the desired praseodymium-neodymium-iron alloy in large quantities.

(Summary of the Invention) The present invention has been made against the background of the above, and its object is to produce a high-performance permanent magnet using praseodymium-iron or praseodymium-neodymium-iron alloy. Praseodymium-iron or praseodymium-neodymium, which is particularly suitable for the production of magnetic materials such as
The purpose is to provide a method and equipment for producing iron alloys on a large scale and continuously.Another object of the invention is to provide a method and equipment for producing iron alloys on a large scale, and another purpose is to eliminate harmful impurities and It is an object of the present invention to provide a reliable and economical industrial manufacturing method and apparatus for a praseodymium-iron alloy or a praseodymium-neodymium-iron alloy with a low content of inclusions.

That is, in order to achieve the above object, the present invention electrolytically reduces a praseodymium compound or a raw material compound consisting of the praseodymium compound and a neodymium compound in a molten salt electrolytic bath using an iron cathode and a carbon anode, and produces praseodymium or praseodymium. and neodymium are precipitated on the iron cathode and alloyed with the iron constituting the cathode to form praseodymium-iron or praseodymium-neodymium-iron alloy, the method comprising praseodymium fluoride or fluoride as the raw material compound. A fluorinated raw material consisting of a mixture of praseodymium chloride and neodymium fluoride is used, and the molten salt electrolytic bath containing the fluoride raw material is substantially
At 5-76% by weight of praseodymium fluoride or a mixture of praseodymium fluoride and neodymium fluoride, 20-60% by weight of lithium fluoride, up to 40% by weight of barium fluoride and up to 20% by weight of calcium fluoride. wherein the praseodymium-iron alloy or praseodymium-neodymium-iron alloy is formed on the iron cathode in a liquid state, and the praseodymium-iron alloy or praseodymium-neodymium-iron alloy in the liquid state is The alloy is dropped as a droplet into a receiver having an opening in the electrolytic bath below the iron cathode and stored as a liquid layer, and the produced alloy is taken out in a liquid state from the liquid layer in the receiver. be.

Thus, according to the present invention, a praseodymium-iron alloy or a praseodymium-neodymium-iron alloy can be produced in one step of the electrolytic reduction operation, and impurities such as oxygen and inclusions that adversely affect the magnetic properties of the permanent magnet can be produced. Praseodymium - iron alloy or praseodymium - with low content of praseodymium or praseodymium and high neodymium content
Neodymium-iron alloys could now be manufactured economically, continuously, and on a large scale in one step.

More specifically, since a solid cathode is used, the cathode is not only easy to handle, but also the produced alloy can be taken out as a liquid alloy during electrolysis, so electrolysis can be carried out without interrupting the electrolysis. Continuous operation is possible, and as a result of continuous low-temperature operation, which is an advantage of the consumable cathode method, the electrolytic performance and the quality of the produced alloy are effectively improved.

Further, according to the present invention, it is possible to achieve large-scale and continuous operation, which is difficult to achieve with the above-mentioned reduction method using active metals such as calcium. This has made it possible to avoid all difficulties in continuous operation in the electrolytic production method of compound-oxide mixed molten salt, and in addition, as in the case of the electrolytic method using praseodymium oxide as a raw material, PraO++) p
There is no longer a need for the previous step of reducing it to the r, o3 form to use it as a raw material.

Furthermore, according to the present invention, it is possible to operate at a lower temperature than electrolysis using praseodymium oxide or praseodymium oxide-neodymium oxide as raw materials, which prevents contamination of impurities and inclusions from furnace materials etc. into the produced alloy. can be effectively suppressed, and the anode current density can be increased at the same temperature. There is an advantage that the current can be increased and productivity can be improved.

In addition, in the method of the present invention as described above, it is desirable that the molten salt electrolytic bath is maintained at a temperature of 770 to 950°C, and that the electrolytic reduction operation is performed at this temperature. In, anode current density: 0.05 to 1.0OA/cm2, cathode current density:
The conditions of 0.50 to 55 A/cJ will be suitably adopted.

Furthermore, the molten salt electrolytic bath containing the fluoride raw material in which the electrolytic reduction operation is performed is such that it is substantially a 6-binary system of praseodymium fluoride or a mixture of praseodymium fluoride and neodymium fluoride and lithium fluoride. in which the praseodymium fluoride or the mixture of praseodymium fluoride and neodymium fluoride contains at least 40%
It is desirable that the fluorinated salt is present in the electrolytic bath in an amount of at least 24% by weight.

As described above, by adopting the method according to the present invention, a low impurity, high praseodymium-containing praseodymium-iron alloy, or a low impurity,
It became possible to produce a praseodymium-neodymium-iron alloy with a high [praseodymium-neodymium] content economically and continuously on a large scale. Such a praseodymium-iron or praseodymium-neodymium-iron alloy can also be advantageously used as an intermediate raw material for producing praseodymium metal or praseodymium-neodymium alloy.

In carrying out the present invention, (a) substantially praseodymium fluoride or a mixture of praseodymium fluoride and neodymium fluoride, lithium fluoride, and barium fluoride added as necessary; an electrolytic cell made of a refractory material and containing a molten salt electrolytic bath made of calcium fluoride; (b) a lining applied to the inner surface of the electrolytic cell in contact with the bath; and (c) a lining of the electrolytic cell. (d) a long carbon anode that is inserted and immersed in the molten salt electrolytic bath and whose shape does not substantially change in the longitudinal direction; (e) an elongated iron cathode whose shape does not change in the longitudinal direction; Droplets of praseodymium-iron alloy or praseodymium-neodymium-iron alloy produced on the iron cathode by electrolytic reduction of praseodymium fluoride or praseodymium fluoride and neodymium fluoride by a direct current applied between a carbon anode and an iron cathode. (f) an alloy receiver for collecting such produced alloy droplets, into which the alloy receiver is dropped; (g) subjecting the iron cathode to a predetermined current density in the molten salt electrolytic bath of the electrolytic cell in accordance with its depletion as the praseodymium-iron alloy or praseodymium-neodymium-iron alloy is produced; A device including a cathode insertion means for inserting the cathode so as to obtain the cathode is preferably used.

However, such a praseodymium-iron alloy or praseodymium-neodymium-iron alloy production apparatus further includes an anode for inserting the carbon anode into the molten salt electrolytic bath of the electrolytic cell so as to obtain a predetermined current density. It is preferable to include an insertion means and a raw material supply means for supplying praseodymium fluoride or a mixture of praseodymium fluoride and neodymium fluoride as a raw material into the electrolytic cell. As the lining, an inexpensive iron material is preferably used instead of a refractory metal material such as molybdenum or tungsten.

Through studies conducted by the present inventors, it has been discovered that such an iron material exhibits excellent bath resistance and corrosion resistance, and is a good lining material for fluoride electrolytic baths.

In addition, in the present invention, the praseodymium-iron alloy or the praseodymium-neodymium-iron alloy in the liquid state collected in the alloy receiver placed in the electrolytic cell is left in the liquid state to be effectively discharged outside the electrolytic cell. The liquid alloy extraction means is configured to have a pipe-like nozzle inserted into the liquid produced alloy in the alloy receiver, through which the produced alloy is sucked up by vacuum suction. Therefore, from the viewpoint of industrial implementation, it is advantageous to take out the electrolytic cell outside the electrolytic cell.

(Specific explanation of the configuration) First, FIG. 1 shows a schematic diagram of an electrolytic system for carrying out the present invention. is adapted to be charged with a solvent 4 constituting a molten salt electrolytic bath.

As this solvent 4, praseodymium fluoride (P
rF3) or a mixture of praseodymium fluoride (PrF, J) and neodymium fluoride (NdF, ) (hereinafter abbreviated as rare earth fluoride mixed salt) and lithium fluoride (L i F
) is used, but in addition to these, barium fluoride (
It is also possible to use BaF, ) and calcium fluoride (CaFz) alone or in combination.

On the other hand, the electrolytic raw material is supplied from the raw material supply device 6 into the electrolytic bath in the electrolytic cell 2, and in the present invention, as this raw material, conventional praseodymium oxide (Pr60.
) or a mixture of neodymium oxide and neodymium oxide (NdzOz) (hereinafter referred to as rare earth oxide mixed salt), but praseodymium fluoride or rare earth fluoride mixed salt, which is one of the constituents of the electrolytic bath. It is used.

Further, a carbon anode 8 and an iron cathode 10 are each immersed in the electrolytic bath in the electrolytic bath 2, and direct current power 12 is applied between the anode 8 and the cathode 10, so that the electrolytic bath is heated. The praseodymium fluoride or rare earth fluoride mixed salt raw material contained therein is electrolytically reduced. The metal praseodymium or praseodymium-neodymium deposited on the cathode 10 by this electrolytic reduction immediately forms a liquid alloy with iron constituting the cathode 10, drips from the surface of the cathode 10, and electrolyzes the electrolytic cell 2. It will accumulate in a receiver that should not be placed in a bath. Note that at the temperature at which the above-mentioned predetermined solvent composition melts, the alloy formed on the iron cathode 10 will be in a liquid state, and the specific gravity of the electrolytic bath made of such a molten salt will depend on the temperature of the formed alloy. As the liquid alloy is formed on the iron cathode 10, it falls below the surface of the cathode 10.

Therefore, the liquid alloy collected in the receiver having the opening located below the iron cathode 10, which receives the liquid alloy falling from the iron cathode 10, is further transferred to the outside of the electrolytic cell 2 by the appropriate alloy extraction means 14. It will be taken out and collected.

In addition, the electrolytic bath, the produced alloy, and the electrode (anode 8
A protective gas 16 is introduced in order to prevent deterioration of the cathode 10), the constituent materials of the electrolytic cell, etc., and to avoid the mixing of harmful impurities and inclusions into the produced alloy. Further, the gas generated in the electrolytic cell 2 during the electrolytic reduction operation is led to the waste gas treatment device 18 together with the introduced protective gas, and is subjected to a predetermined treatment.

By the way, in the electrolytic system according to the present invention, praseodymium fluoride or a mixture of praseodymium fluoride and neodymium fluoride is used as the electrolytic raw material, unlike the conventional praseodymium oxide or a mixture of praseodymium oxide and neodymium oxide. be done. When this fluoride is used as a raw material, even in the electrolysis of the praseodymium fluoride/neodymium fluoride mixture, the composition ratio of praseodymium to neodymium fluoride is approximately the same as the composition ratio of praseodymium fluoride to neodymium fluoride in the electrolytic bath. It has been found that an alloy containing 10% of the total amount of carbon dioxide is deposited on the cathode. That is, when trying to obtain an alloy having the desired praseodymium-neodymium composition ratio, by using an electrolytic bath with the same composition ratio and supplying a fluoride raw material with the same composition ratio to replace the amount consumed by electrolysis, Electrolysis can be performed continuously. It has been found that this relationship is maintained over the entire concentration range of the binary fluoride consisting of praseodymium fluoride and neodymium fluoride. Furthermore, these fluoride raw materials are also the main constituents of the electrolytic bath, are easily supplied, and can continue electrolysis warmly and over a wide raw material concentration range compared to oxide electrolysis.

The method for supplying electrolytic fluoride is generally to add it to the surface of the electrolytic bath in the form of a powder, which is preferable because it dissolves quickly into the electrolytic bath, but it is preferable to introduce it into the electrolytic bath together with a gas. It can also be carried out by immersing a powder molded body in an electrolytic bath. Furthermore, compared to the case of electrolysis of oxide raw materials, in the electrolysis operation of fluoride raw materials, the permissible range of the electrolytic raw material concentration in the electrolytic region between the electrodes is warmer and larger, and therefore the movement of the supplied raw material to this region is Even if there is a delay in the process, it is unlikely to interfere with the continuation of electrolysis, and therefore, the supply position of the raw material fluoride and the supply amount per amount of electricity for electrolysis are not subject to detailed restrictions as when using oxides as raw materials. However, it has the advantage that selection can be made more arbitrarily.

In addition, in the present invention, in order to produce a praseodymium-iron alloy or a praseodymium-neodymium-iron alloy with few impurities or inclusions, it is necessary to lower the electrolysis temperature, and for this purpose, the 76% (based on weight).

praseodymium fluoride or a mixed fluoride salt (same hereinafter), 20-60% lithium fluoride, up to 40% barium fluoride, and up to 20% calcium fluoride; Even if a mixed molten salt consisting only of fluorides is selected as the electrolytic bath and the above-mentioned raw material fluoride is added to such an electrolytic bath, the electrolytic bath should always have a composition within this range during electrolysis. It will be adjusted to

Note that the concentration of praseodymium fluoride or rare earth fluoride mixed salt in the electrolytic bath composition according to the present invention is less than the lower limit,
That is, if it is less than 35%, the electrolytic performance will deteriorate, and if it exceeds the upper limit concentration (76%), problems such as the melting point of the electrolytic bath will rise too much. In addition, if the concentration of lithium fluoride is too low, the melting point of the electrolytic bath will rise too much, while if the concentration is too high, the reaction with the formed alloy will become intense, resulting in poor electrolytic performance. Since this problem arises, its concentration needs to be adjusted to 20-60%.

Furthermore, barium fluoride and calcium fluoride are added for the purpose of reducing the amount of expensive lithium fluoride used and adjusting the melting temperature of the mixed molten salt that is formed. If there is too much fluoride, the melting point of the electrolytic bath will rise too much, so the former barium fluoride should be used at a proportion of up to 40%, and the latter calcium fluoride at a proportion of up to 20%, each alone or together. It will be used. These four components, namely praseodymium fluoride or recovered fluoride mixed salt,
The electrolytic bath is formed such that the total amount of lithium fluoride, barium fluoride, and calcium fluoride is substantially 100%.

However, regarding such an electrolytic bath composition, if the electrolytic bath is a binary system consisting of only two components: praseodymium fluoride or a mixed salt of recovered fluoride, and lithium fluoride, praseodymium fluoride Alternatively, it is preferable that the fluoride mixed salt and lithium fluoride be prepared in an amount of at least 40% and 24%, respectively, in the electrolytic bath. Each fluoride used as a component of this electrolytic bath must be of high purity as long as it does not contain impurities that have a negative effect on the properties of the end-use product of the electrolyzed and produced alloy, such as the magnetic properties of permanent magnets. Impurities that are normally included unavoidably in industrial raw materials may be included in the electrolytic bath as long as they are tolerable. The composition of the electrolytic bath is selected so that the electrolytic bath has a specific gravity smaller than the specific gravity of the praseodymium-iron or praseodymium-neodymium-iron alloy that is produced. alloy or praseodymium-neodymium-iron alloy,
Due to the difference in specific gravity, it falls through the electrolytic bath from the cathode and can easily reach a receiver for the produced alloy, which has an opening located below the cathode.

In the present invention, the temperature during electrolysis of the electrolytic bath having such a composition is preferably adjusted to a range of 770°C to 950°C. As mentioned above, if the electrolytic bath temperature becomes too high, the amount of impurities and inclusions mixed into the produced alloy will exceed the permissible limit.
On the other hand, if the electrolytic bath temperature is too low, it becomes difficult to form a homogeneous molten salt electrolytic bath, the properties of the electrolytic bath deteriorate, and it becomes difficult to continue electrolysis.

In such a temperature range, a high praseodymium or high [praseodymium-neodymium] concentration praseodymium-iron alloy or praseodymium-neodymium-iron alloy containing 73% by weight or more of praseodymium or praseodymium-neodymium can be advantageously produced. Moreover, the produced alloy forms a liquid layer in the receiver within this concentration range, making it suitable for extraction in a liquid state. The liquid alloy in this receiver can be effectively taken out from the upper part of the electrolytic cell by a vacuum suction method, and can also be taken out from below by a pouring method. Moreover,
When taking out the alloy, there is no need to specially heat the alloy in the receiver, and the alloy can be taken out of the electrolytic cell very easily as a liquid alloy.

Further, in the present invention, as the electrodes for electrolysis, iron is preferably used for the cathode, and carbon, particularly graphite, is preferably used for the anode. If the iron of the cathode contains impurities, the impurities will be introduced into the produced alloy. Therefore, when such a produced alloy is used as a material for a permanent magnet, it is necessary to avoid impurities such as oxygen that deteriorate the magnetic properties of the produced alloy. It is preferable to use less. Further, according to the present invention, as the electrolytic operation progresses, the iron constituting the cathode produces a praseodymium-iron alloy or a praseodymium-neodymium-iron alloy and is consumed. By supplementing iron in the parts and sequentially immersing the cathode in the electrolytic bath, the desired praseodymium-iron alloy or praseodymium-neodymium-iron alloy can be produced continuously without interrupting the electrolytic operation. It is possible. that time,
Of course, it is possible to perform thread cutting or the like on the end of the iron member of the cathode, and then connect the iron members constituting the cathode one after another by screw connection or the like to compensate for the consumed cathode portion. In this way, the fact that solid iron can be used as a cathode is easier to handle than when molten metal is used as a cathode, and the electrolytic furnace can be simplified in terms of equipment, so it is useful for industrialization. This is a great advantage in that it is easy to increase the size of the electrolytic furnace.

In addition, in fluoride electrolysis using the carbon anode according to the present invention, the current density over the entire surface of the anode is
It is desirable to maintain the current within the range of 0.05 to 1.00 A/cd at all times during the electrolytic operation. However, if this current density is too low, the anode surface area will be too large or the current per unit surface area of the anode will be too small, resulting in poor productivity and no industrial advantage. Furthermore, if the current density becomes too high, an anode effect or similar abnormal phenomena are likely to occur when an oxide is used as a raw material. Therefore, in the present invention, it is recommended that the anode current density, which is one of the electrolytic conditions, be maintained within the above range to effectively avoid the occurrence of such abnormal phenomena. Note that, taking into account local fluctuations on the anode surface, the current density over the entire surface of the anode is 0.10 to 0.
It is more preferable to maintain it between 40 A/cal.

Furthermore, when praseodymium fluoride or a mixed fluoride salt is used as a raw material, the anode current density can be higher at the same temperature than when praseodymium oxide or a mixed salt of clay oxide is used as a raw material. This is preferable from the viewpoint of productivity.

On the other hand, the current density of the cathode is allowed over a wide range of 0.50 to 55 A/a as the current density over the entire surface of the cathode. However, if the cathode current density is too low, the current per unit surface area of the cathode will be too small, resulting in poor productivity and not being industrially viable. Furthermore, if this cathode current density becomes too high, the electrolytic voltage will increase significantly and the electrolytic results will deteriorate. In addition, when continuing the actual electrolytic operation, it is recommended to keep the cathode current density within a narrower range of 1.5 to 25 A/cJa in order to maintain a narrow variation range of the electrolytic voltage and facilitate the electrolytic operation. , can be said to be more preferable.

Furthermore, according to the present invention, carbon, which is different from the bath-resistant material of the electrolytic bath, is used as the anode, unlike the case where the bath-resistant container (bath-resistant material) of the electrolytic bath also serves as the anode. ,
There is no need to terminate the electrolysis due to consumption of the anode; it is only necessary to compensate for the consumption and further immerse the anode in the electrolytic bath, or, since a plurality of anodes are used, to replace them with new anodes one by one. Similarly, the cathode only needs to be immersed in an electrolytic bath to compensate for its consumption, or replaced with a new cathode. In the present invention, due to the large difference in the surface current density ratio between the anode and cathode, it is preferable to use an electrode arrangement in which a plurality of anodes are arranged around the cathode so that the anode faces the cathode. In such cases, if the anodes are replaced sequentially, praseodymium-iron alloys and praseodymium-neodymium-iron alloys can be continuously produced without interrupting electrolytic operation. The advantages of the electrolytic method can be fully utilized. Moreover, since both the anode shape and the cathode shape can be used with an external shape that does not substantially change in the length direction, there will be no inconvenience caused in their continuous use. be.

Incidentally, a preferred example of the structure of an electrolytic cell implementing the present invention is schematically shown in FIG. 2.

In FIG. 2, the electrolytic cell 20 is composed of a lower tank 22 and a lid 24 that covers the opening thereof. The outer sides of the lower tank 22 and the lid body 24 are usually constructed of tank outer frames 26 and 28 made of metal such as rope.

Furthermore, the lower tank 22 and the lid body 24 each have a fireproof insulation material layer 30.32 made of brick, castable alumina, etc. on the outside, and a bath-resistant material layer 34.36 made of graphite, carbonaceous stamp material, etc. on the inside. Arranged and configured.

A lining material 38 is provided on the inner bath-contact surface of the inner bath-resistant material layer 34 of the lower tank 22 to cover the bath-contact surface. This lining material 38 is a bath-resistant material layer 34.
In addition to preventing the contamination of impurities from tungsten or molybdenum, if it is made of a refractory metal such as tungsten or molybdenum, it can also serve as a receiver for the liquid praseodymium-iron or praseodymium-neodymium-iron alloy that is produced. . However, in the present invention, it is recommended to use an inexpensive iron material as the lining material 38. This is because, through studies conducted by the present inventors, it has been discovered that inexpensive iron exhibits excellent bath resistance and corrosion resistance, and is a good lining material for fluoride electrolytic baths. Moreover, the bath-resistant material layer 34 is
It is not necessary, and there is no problem in applying the lining material 38 directly on the refractory insulation layer 30.

Further, one or more iron cathodes 40 and a plurality of carbon anodes 42 arranged opposite to the iron cathodes 40 are provided so as to penetrate through the lid body 24, and both of these electrodes 40 .42 is immersed in an electrolytic bath 44 made of the predetermined molten salt housed in the lower tank 22 over a length that provides a predetermined current density. Note that here, two of the carbon anodes 42, 42 are shown among the anodes disposed facing the iron cathode 40, and graphite is preferably used as their material.

Further, these carbon anodes 42, 42 are used in the form of rods, plates, tubes, etc., and in order to increase the anode surface area of the part immersed in the electrolytic bath 44 and lower the anode current density, grooves are formed as known in the art. It can also be attached. In addition, in FIG. 2, the carbon anode 42 has a slight slope at the anode immersion part, showing traces of anode wear due to electrolysis. There is no problem even if an electric lead made of a suitable conductor such as metal is attached to the anode 42 for power supply. Also,
The anode 42 can be moved up and down by an anode lifting mechanism 46 serving as an anode insertion means, and can be moved intermittently or continuously to ensure an appropriate anode current density for continuing electrolysis. Moreover, the surface area of the immersion part can be adjusted by adjusting the immersion depth. Note that the anode lifting/lowering mechanism 46° 46 can also have the function of electrically connecting to the anode.

On the other hand, the cathode 40 is made of iron to be alloyed with metal praseodymium or praseodymium-neodymium deposited by electrolytic reduction, and here, one of them is
The book is shown. In addition, in Figure 2, praseodymium-
The cathode immersion area is shown in a conical shape, showing traces of cathode consumption due to droplet formation of iron or praseodymium-neodymium-iron alloy. Since the electrolysis temperature is selected to be below the melting point of the iron of the cathode 40, the iron cathode 40 is solid and is used in the form of a wire, rod, plate, tube, or the like. This iron cathode 40 is also fed continuously or intermittently into the electrolytic bath 44 by a cathode elevating mechanism 48 serving as a cathode insertion means to compensate for consumption due to alloy formation. The cathode lifting mechanism 48 can also have the function of electrically connecting to the cathode. Further, the surface of the iron cathode 40 other than the immersed portion may be protected with a suitable protective sleeve or the like for corrosion prevention.

Further, in the electrolytic bath 44, a produced alloy receiver 50 is arranged on the bottom of the lower tank 22 so that the receiver opening is located below the iron cathode 40, and the iron cathode is The liquid praseodymium-iron or praseodymium-neodymium-iron alloy 52 produced on 40 is
It drips from the surface of the cathode and is collected in the produced alloy receiver 50 which opens directly below it. The produced alloy receiver 50 is formed using a refractory metal that has low reactivity with the produced alloy 52, such as tungsten, tantalum, molybdenum, niobium, or an alloy thereof, or a boron such as boron nitride. It can also be formed using ceramics such as compounds or oxides, materials such as cermet, or even iron.

The electrolytic bath 44 is made of praseodymium fluoride, or a fluoride mixed molten salt containing praseodymium fluoride and neodymium fluoride, which has been adjusted to have a composition according to the present invention, and its composition is determined by its specific gravity. is selected so that the specific gravity is less than or equal to the praseodymium-iron or praseodymium-neodymium-iron alloy produced. The electrolytic raw material consumed by electrolysis is supplied from a raw material supply device 54 through a raw material supply hole 56 provided in the lid 24, so that the electrolytic bath 44 of a predetermined composition is maintained.

In addition, when a predetermined amount of generated alloy 52 drips from the iron cathode 40 and accumulates in the receiver 50, it is removed from the electrolytic cell 20 in a liquid state by a predetermined alloy recovery mechanism (retrieval means). However, in the present invention, as shown in FIG. The tip of the nozzle 58 is immersed in the produced alloy 52 in the produced alloy receiver 50, and the produced alloy 52 is sucked up by suction using the vacuum suction action of a vacuum device (not shown), and is removed from the electrolytic cell 20. A means for taking out the material is advantageously employed.

However, instead of using such a vacuum suction method to take out the produced alloy 52, an extraction pipe is provided that penetrates the lower part of the electrolytic cell 20 (lower tank 22), and the tip of this extraction pipe is further connected to the produced alloy receiver 50. It is also possible to adopt an alloy recovery mechanism in which the produced alloy 52 is flowed out of the tank and downward through the take-out pipe by penetrating the pipe and opening into the receiver 50.

Although not shown in the figure, a protective gas is supplied into the electrolytic cell 20, and the gas generated by the electrolytic operation is discharged to the outside through the waste gas outlet 62 together with the protective gas. It is designed to be ejected. Further, although such an electrolytic cell 20 is not provided with a special heating device for maintaining the electrolysis temperature described above, in order to maintain the electrolysis temperature at a predetermined temperature, the inside of this electrolytic cell 20 may be heated as necessary. It goes without saying that a suitable heating device may be provided inside or outside the heating device.

(Examples) In order to clarify the present invention more specifically, some examples according to the present invention will be shown below, but the present invention should not be construed in any way limited by the description of such examples. It goes without saying that this is not the case.

The present invention can be implemented in various embodiments in addition to the detailed description of the present invention described above and the following examples, and various modifications can be made based on the knowledge of those skilled in the art without departing from the spirit of the present invention. It is understood that any of the embodiments that can be implemented in the above embodiments are within the scope of the present invention.
should be understood.

Example 1 7.0k of praseodymium-neodymium-iron (Pr-Nd-Fe) alloy having an average composition of 85% praseodymium (by weight, same hereinafter), 1% neodymium and 13% iron
g was obtained as follows.

That is, in an apparatus having the same configuration as the electrolytic cell shown in Part 2, a graphite crucible is used as the bath-resistant material of the electrolytic cell, and a molybdenum container installed at the center of the bottom of the graphite crucible as a receptacle for the produced alloy is used. An electrolytic bath consisting of a binary fluoride mixed molten salt of praseodymium fluoride and lithium fluoride containing a small amount of neodymium chloride as an impurity was electrolyzed in an inert gas atmosphere at an average electrolysis temperature of 837°C. As the cathode, we used three 12-diameter iron wires arranged on the same circumference and immersed in the electrolyte bath in the center of the graphite crucible (in planar form), and as the anode, we used a concentric circle around the cathode. arrayed (in planar form) and immersed in an electrolytic bath,
Five 6On+φ graphite rods were used.

Then, using praseodymium fluoride containing a small amount of neodymium fluoride as an impurity as a raw material, the powder was continuously supplied to the electrolytic bath while maintaining the electrolytic conditions within the range shown in Table 1 below for 24 hours. Electrolysis was performed. During this period, the electrolytic operation was able to continue very well, and the liquid praseodymium-iron alloy was dripped in succession and collected in a molybdenum receiver placed in the electrolytic bath. This accumulated alloy was taken out of the electrolytic cell every 8 hours using a vacuum suction type alloy recovery device having a vacuum suction nozzle.

The electrolytic results obtained by such electrolytic operation and the analysis results of the produced alloy are shown in Tables 1 and 2 below.

For comparison, in a similar manufacturing device, praseodymium oxide powder was used as a raw material, and this was continuously supplied to the electrolytic bath in the anode gas generation area (electrolysis area) between the cathode and the anode, resulting in approximately the same electrolysis. Electrolysis was carried out under these conditions, but in that case, unless the anode current density was reduced to 1/2 or less of that during the above-mentioned fluoride raw material electrolysis, the anodic effect would occur frequently and oxide electrolysis could not continue for m. there were. Therefore, praseodymium oxide had to be supplied in excess, and as a result, sludge was formed at the bottom of the electrolytic cell.

Example 2 2 of a praseodymium-neodymium-iron alloy having an average composition of 44% praseodymium, 43% neodymium and 12% iron.
0 kg was obtained by electrolytic operation as follows.

First, a graphite crucible with an iron lining on the inner surface as a bath-resistant material was used as a container for the electrolytic bath, and a molybdenum container placed in the center of the bottom was used as a receiver for the produced alloy. An electrolytic bath consisting of a ternary fluoride mixed molten salt of neodymium fluoride and lithium fluoride was electrolyzed in an inert gas atmosphere at an average electrolysis temperature of 839°C. As the cathode, three iron rods of 12 m.phi. arranged in the same manner as in Example 1 were used, and as the anode, five graphite rods of 60 m.phi. as in Example 1 were used.

And praseodymium fluoride 50% - neodymium fluoride 5
When a 0% mixture was used as a raw material and the electrolytic conditions were kept within the range shown in Table 1 below while continuously supplying it to the electrolytic bath, good electrolytic operation was achieved for 8 hours.
It was vt. In addition, liquid praseodymium - neodymium -
The iron alloy was dropped sequentially and collected in a molybdenum receiver. Furthermore, the collected alloy produced in the receiver could be taken out in a liquid state as in Example 1.

The electrolytic results obtained by such electrolytic operation and the analysis results of the produced alloy are shown in Tables 1 and 2 below, respectively.

Example 3 5.6 kg of praseodymium-neodymium-iron alloy with an average composition of 21% praseodymium, 66% neodymium and 12% iron.
was obtained by employing the following electrolytic operation.

That is, using a graphite crucible as a bath-resistant container for an electrolytic cell,
An iron forming alloy receiver was installed at the center of the bottom, and an electrolytic bath consisting of a ternary fluoride mixed molten salt of praseodymium fluoride, neodymium fluoride, and lithium fluoride was heated at an average of 8.
Electrolysis was carried out under an inert gas atmosphere at an electrolysis temperature of 4°C. As the cathode, three iron rods of 12 crane diameter similar to those in Example 2 were used, and as the anode, five graphite rods of 60 w diameter arranged concentrically around the cathode (in planar form) were used.

and praseodymium fluoride 25% - neodymium fluoride 7
While continuously supplying a 5% mixture as a raw material to the electrolytic bath, maintaining the electrolytic conditions within the range shown in Table 1 below,
Good electrolytic operation could be continued for 24 hours. In addition, a liquid praseodymium-neodymium-iron alloy was sequentially dropped and collected in the iron container. Furthermore, this accumulated alloy was taken out from the electrolytic cell in a liquid state in the same manner as in Example 1.

The electrolytic results obtained by such electrolytic operation and the analysis results of the produced alloy are shown in Tables 1 and 2 below, respectively.

Example 4 A praseodymium-neodymium-iron alloy with an average composition of 1% praseodymium, 84% neodymium and 14% iron was obtained following an electrolytic operation similar to Example 1.

As the electrolytic bath, a fluoride mixed molten salt of neodymium fluoride and lithium fluoride containing a small amount of praseodymium fluoride was used.

Further, the electrolytic results obtained by such electrolytic operation and the analysis results of the produced alloy are shown in Tables 1 and 2 below, respectively.

As is clear from the results in Tables 1 and 2, by electrolyzing praseodymium fluoride and neodymium fluoride according to the present invention, praseodymium-neodymium-iron alloys with high praseodymium and neodymium contents can be produced all at once. It has been observed that the resulting alloy is a neodymium-iron alloy with a low content of impurities such as oxygen which deteriorate the magnetic properties. Note that the numerical values of the alloy-containing components in Table 2 are the average values of the analysis values of the alloy taken out every 8 hours.

Furthermore, among the above examples, in Examples 1.3 and 4,
Furthermore, it has been confirmed that it is easy to perform electrolysis continuously for a long time, and even in such a case, results similar to those of the respective Examples can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a specific electrolytic system for implementing the present invention, and FIG. 2 is a sectional view showing an example of the structure of an electrolytic cell for implementing the present invention. 2: Electrolytic cell 4: Solvent 6: Raw material supply device 8: Carbon anode 10: Iron cathode 12: Electric power 14: Alloy extraction means 16: Protective gas 18: Waste gas treatment device 20: Electrolytic cell 22: Lower tank 24: Lid body 30.32: Fireproof insulation material layer 34.36: Bath-resistant material layer 38 lining material 40: Iron cathode 42: Carbon anode 44: Electrolytic bath 46: Anode lifting mechanism 48: Cathode lifting mechanism 50: Generated alloy receiver 52: Produced alloy 54: Raw material supply device 58: Vacuum suction nozzle 60: Produced alloy suction hole Applicant: Sumitomo Light Metal Industries, Ltd. Figure 1

Claims (11)

[Claims] (1) Using an iron cathode and a carbon anode, a praseodymium compound or a raw material compound consisting of this and a neodymium compound is electrolytically reduced in a molten salt electrolytic bath, and the praseodymium or praseodymium and neodymium produced are deposited on the iron cathode. , a method of alloying with iron constituting the cathode to form a praseodymium-iron alloy or a praseodymium-neodymium-iron alloy, wherein the raw material compound is praseodymium fluoride or a mixture of praseodymium fluoride and neodymium fluoride. A fluoride raw material is used, and the molten salt electrolytic bath containing the fluoride raw material contains substantially 35-76% by weight of praseodymium fluoride or a mixture of praseodymium fluoride and neodymium fluoride, 20-60% by weight of praseodymium fluoride, Lithium fluoride, 4
The praseodymium-iron alloy or the praseodymium-neodymium-iron alloy is formed in a liquid state on the iron cathode while being adjusted to consist of up to 0% by weight of barium fluoride and up to 20% by weight of calcium fluoride. Then, the liquid praseodymium-iron alloy or praseodymium-neodymium-iron alloy is dropped as droplets into a receiver having an opening in the electrolytic bath below the iron cathode, and is collected as a liquid layer. A method for producing praseodymium-iron or praseodymium-neodymium-iron alloy, characterized in that the produced alloy is taken out in a liquid state from a liquid layer in a vessel. (2) The manufacturing method according to claim 1, wherein the molten salt electrolytic bath is maintained at a temperature of 770 to 950°C, and the electrolytic reduction operation is performed at this temperature. (3) The electrolytic reduction operation has an anode current density of 0.05 to
1.00A/cm^2, cathode current density: 0.50-55
Claim 1 carried out under the condition of A/cm^2
The manufacturing method described in item 1 or 2. (4) The manufacturing method according to any one of claims 1 to 3, wherein the carbon electrode is a graphite electrode. (5) The molten salt electrolytic bath containing the fluoride raw material is substantially composed of praseodymium fluoride or a mixture of praseodymium fluoride and neodymium fluoride and lithium fluoride, and the praseodymium fluoride or praseodymium fluoride and neodymium fluoride in an amount of at least 40% by weight, and lithium fluoride in an amount of at least 24% by weight, respectively. Method. (6) substantially praseodymium fluoride or a mixture of praseodymium fluoride and neodymium fluoride, and lithium fluoride and optionally added barium fluoride;
An electrolytic cell made of a refractory material that accommodates a molten salt electrolytic bath made of calcium fluoride; a lining provided on the inner surface of the electrolytic cell in contact with the bath; and a lining in the molten salt electrolytic bath of the electrolytic cell. an elongated carbon anode that is inserted and immersed into the molten salt electrolytic bath of the electrolytic cell; an elongated iron cathode without a carbon anode, and an electric current is applied between the carbon anode and the iron cathode, the aperture being positioned in the molten salt electrolytic bath of the electrolytic cell so that the opening is located below the iron cathode. droplets of praseodymium-iron alloy or praseodymium-neodymium-iron alloy formed on the iron cathode by electrolytic reduction of praseodymium fluoride or praseodymium fluoride and neodymium fluoride by means of a direct current; collect such resulting alloy droplets; an alloy receiver for extracting the liquid praseodymium-iron alloy or praseodymium-neodymium-iron alloy in the alloy receiver to the outside of the electrolytic cell; cathode insertion means for insertion into the molten salt electrolytic bath of the electrolytic cell so as to obtain a predetermined current density according to its consumption as the alloy or praseodymium-neodymium-iron alloy is produced; An apparatus for producing praseodymium-iron or praseodymium-neodymium-iron alloy. (7) The manufacturing apparatus according to claim 6, further comprising anode insertion means for inserting the carbon anode into the molten salt electrolytic bath of the electrolytic cell so as to obtain a predetermined current density. (8) The manufacturing apparatus according to claim 6 or 7, further comprising a raw material supply means for supplying praseodymium fluoride or a mixture of praseodymium fluoride and neodymium fluoride as a raw material into the electrolytic cell. (9) The liquid alloy retrieval means is a liquid praseodymium-iron alloy or a praseodymium-neodymium-
Claim 6, comprising a pipe-shaped nozzle inserted into the iron alloy, through which the praseodymium-iron alloy or the praseodymium-neodymium-iron alloy is sucked up and taken out of the electrolytic cell by a vacuum suction action. 9. The manufacturing apparatus according to any one of items 8 to 9. (10) The manufacturing apparatus according to any one of claims 6 to 9, wherein the lining is made of iron material. (11) The manufacturing apparatus according to any one of claims 6 to 10, wherein the carbon electrode is a graphite electrode.