JPS6187888A - Method and device for producing neodymium-iron base alloy - Google Patents

Abstract

PURPOSE:To reduce continuously an Nd-Fe alloy in a large scale by taking out the Nd-Fe alloy in the liquid state produced in one stage of an electrolytic reduction operation collected into an alloy vessel disposed in an electrolytic cell to the outside of the electrolytic cell in the liquid state. CONSTITUTION:The Nd compd. consisting, by weight %, of 35-76 NdF3, 20-60 LiF, <40 BaF2 and <20 CaF2 is electrolytically reduced in a molten electrolytic bath by using an iron cathode and carbon anode. The formed Nd is deposited on the iron cathode and is alloyed with the Fe constituting the cathode to form the Nd-Fe alloy on the cathode. The Nd-Fe alloy in the liquid state is dropped in the form of droplets into a receiver having an aperture in the electrolytic bath below the cathode and is stored as a liquid layer. The Nd-Fe alloy is taken out in the liquid state from the liquid layer in said receiver.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for producing a neodymium-iron master alloy and an apparatus for producing the same, and in particular to a neodymium-iron alloy, particularly a neodymium-iron alloy suitable for a master alloy for high-performance permanent magnets. High neodymium content (,
The present invention relates to a method and apparatus for continuously producing a neodymium-iron alloy with a low content of harmful impurities and inclusions.

(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). Both neodymium-iron and neodymium-iron-boron permanent magnets require raw materials with few impurities that degrade magnetic properties, and especially for neodymium raw materials with high reactivity, those with low impurities such as oxygen are manufactured. It is necessary to establish an industrial method to do so.

By the way, metallic neodymium has so far had almost no use, and the only known manufacturing methods are a reduction method using -C with an active metal, especially calcium, and a molten salt electrolysis method, and industrial manufacturing methods are insufficient. Not established. Therefore, even if there is an industrial manufacturing method for neodymium-iron master alloy suitable as a raw material for high-performance permanent magnets as described above, it has not been sufficiently established.

Under these circumstances, the following methods of manufacturing neo-Nmu iron master alloys can be considered based on the conventional technological level, but each method has various problems inherent in it. None of these methods can be fully satisfied as an industrial or practical method for continuously producing a neodymium-iron master alloy.

a) A method in which metallic neodymium is first produced in advance by a reduction method using an active metal such as calcium or by a molten salt electrolysis wave, and then iron is added, remelted, and alloyed: In this method, , there is a problem with the initial neodymium manufacturing process. That is, the reduction method using active metals such as calcium is a batch method and is not suitable for continuous large-scale production.

In addition, in the molten salt electrolysis method, electrolysis of a chloride electrolytic bath (for example, Jiro Shio et al., "Electrochemistry", Vol. 35, 1967,
(see p. 496, etc.) and electrolysis of an oxide (NdzOz) dissolved in a fluoride electrolytic bath (E, Morris et al., rU, s, B
ur, Min,.

Rep, Invest, J, II & 16957.
(see 1967), but there are problems with electrolytic performance and operating methods, and a method suitable for continuous large-scale production has not been established.

b) A method in which a neodymium compound and iron or iron compound are mixed and alloyed while being reduced with a suitable reducing agent such as calcium: As mentioned above, the reduction method is generally carried out in a batch manner. It is no exception that this method is very unsuitable for continuous large-scale production.

C) A method in which a compound of neodymium and a compound of iron are dissolved in an electrolytic bath consisting of a suitable molten salt and deposited as an alloy of neodymium and iron on a non-consumable cathode by simultaneous electrolysis of these compounds: In this method, It is difficult to stabilize the alloy composition obtained, and iron can be produced in large quantities and inexpensively by other methods without using molten salt electrolysis, so it is inferior to the following method d) in terms of economy. There is.

d) in an electrolytic bath of a suitable molten salt, with the iron itself as the cathode,
Neodymium oxide (NdzO3) as a compound of neodymium
Regarding the so-called consumable cathodic dual method, in which neodymium metal is electrolytically reduced and deposited on the cathode and simultaneously alloyed with the iron of the cathode, neodymium oxide is supplied into a fluoride electrolytic bath and electrolysis is carried out. Research example of obtaining neodymium-iron alloy (
E, Maurice et al., rU,s, Bur, Min,.
Rep, Invest, J + N117146,
1968), which is considered to be an excellent method that does not have the drawbacks of methods a) to C) mentioned above, but it does have various technical difficulties.

In other words, in this electrolysis method using neodymium oxide as a raw material, the solubility of neodymium oxide in the selected electrolytic bath is 2.
When trying to obtain a metal with a small amount of impurities, such as about %, and as the purpose of the present invention, the temperature of the electrolytic bath is selected to be low, and as a result, its solubility further decreases.
It is extremely difficult to dissolve neodymium oxide in the electrolytic bath, and the raw material cannot be continuously and stably supplied. For this reason, (1) an abnormal phenomenon unique to molten salt electrolysis called the anode effect occurs frequently due to insufficient supply of raw materials to the electrolytic bath, and (2) undissolved raw materials coalesce into formed alloy droplets. (3) Undissolved raw materials accumulate at the bottom of the electrolytic bath and form so-called sludge, resulting in deterioration of the quality of the produced alloy due to the inclusion of inclusions, and a decrease in the raw material utilization rate (
(4) Deterioration of electrolytic performance due to the occurrence of anode effect; (5) Continuation of electrolysis itself may sometimes become difficult. This makes it difficult.

(Summary of the Invention) The present invention has been made against the background of the above circumstances, and its purpose is to make a neodymium-iron master alloy particularly suitable for manufacturing high-performance permanent magnets. An object of the present invention is to provide a method and apparatus for producing a neodymium-iron master alloy on a large scale and continuously,
Another purpose is the high neodymium content,
The object of the present invention is to provide a reliable and economical industrial manufacturing method and apparatus for a neodymium-iron master alloy with a low content of harmful impurities and inclusions.

That is, in order to achieve the above object, the present invention electrolytically reduces a neodymium compound in a molten salt electrolytic bath using an iron cathode and a carbon anode, deposits the generated neodymium on the iron cathode, and When alloying with iron constituting the cathode to form a neodymium-iron alloy, neodymium fluoride is used as the neodymium compound, and the molten salt electrolytic bath containing the neodymium compound contains substantially 35 to 76% by weight. neodymium fluoride, 20~
The neodymium-iron alloy is deposited in a liquid state on the iron cathode while being prepared to consist of 60% by weight of lithium fluoride, up to 40% by weight of barium fluoride and up to 20% by weight of calcium fluoride. The neodymium-iron alloy in the liquid state is dropped as droplets into a receiver having an opening in the electrolytic bath below the iron cathode to collect as a liquid layer, and further from the liquid layer in the receiver. , the neodymium-iron alloy was extracted in a liquid state.

As described above, according to the present invention, a neodymium-iron master alloy can be produced in one step of the electrolytic reduction operation, and the content of impurities such as oxygen and inclusions that adversely affect the magnetic properties of permanent magnets is low. , and a neodymium-iron master alloy with a high neodymium content can be effectively produced in one step.

Moreover, 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 at the time of electrolysis, so there is virtually no interruption of 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.

Furthermore, 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 the difficulties in continuous operation in the electrolytic production method, and also to maintain high current efficiency for a long period of time, which cannot be achieved with the electrolytic production method of chloride mixed molten salt made from neodymium chloride. This can be achieved over a period of time.

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 this case, the conditions of anode current density: 0.05 to 0.60 A/cd and cathode current density: 0.50 to 55 A/cj are preferably adopted.

Furthermore, when the molten salt electrolytic bath containing the neodymium compound in which the electrolytic reduction operation is performed is substantially composed of a binary system of neodymium fluoride and lithium fluoride, the molten salt electrolytic bath containing the neodymium compound is It is desirable that the proportion of neodymium fluoride present in the electrolytic bath be at least 40% by weight and the lithium fluoride present in the electrolytic bath in a proportion of at least 24% by weight.

As described above, by adopting the method according to the present invention, it is possible to economically, continuously produce a neodymium-iron master alloy with high neodymium content and low impurity content on a large scale, which is suitable as a raw material for high-performance permanent magnets. It was. Such a neodymium-iron master alloy can also be advantageously used as an intermediate raw material for producing neodymium metal.

In carrying out the present invention, (a) a molten salt electrolytic bath consisting essentially of neodymium fluoride and lithium fluoride, and barium fluoride and calcium fluoride added as necessary; , an electrolytic cell made of a refractory material, (b) a lining applied to the inner surface of the electrolytic cell in contact with the bath, and (C) inserted and immersed in the molten salt electrolytic bath of the electrolytic cell. (d) a long carbon anode with substantially no change in shape in the longitudinal direction; an elongated iron cathode; (e) positioned in the molten salt electrolytic bath of the electrolytic cell, with an aperture located below the iron cathode, and an electric current applied between the carbon anode and the iron cathode; (f) an alloy receiver for collecting neodymium-iron alloy droplets formed on the iron cathode by electrolytic reduction of neodymium fluoride with a direct current; Neodymium in liquid state in receiver
(g) a liquid alloy extraction means for extracting the iron alloy out of the electrolytic cell; An apparatus including a cathode insertion means for inserting the cathode so as to obtain a current density of .

However, such a neodymium-iron master alloy production apparatus further includes an anode insertion means for inserting the carbon anode into the molten salt electrolytic bath of the electrolytic tank so as to obtain a predetermined current density, and a material as a raw material. It is desirable that the electrolytic cell is provided with a raw material supply means for supplying neodymium fluoride into the electrolytic cell,
In addition, the lining applied to the inner surface of the electrolytic cell includes:
Instead of refractory metal materials such as molybdenum and tungsten,
An inexpensive iron material will be suitably used. 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.

Further, in the present invention, in order to effectively take out the neodymium-iron alloy in a liquid state collected in an alloy receiver disposed in an electrolytic cell out of the electrolytic cell while keeping it in a liquid state, The liquid alloy extraction means is configured to have a pipe-like nozzle inserted into the liquid neodymium-iron alloy in the alloy receiver, through which the neodymium-iron alloy is sucked up by vacuum suction and electrolyzed. From the viewpoint of industrial implementation, it is advantageous to take it out of the tank.

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

As this solvent 4, neodymium fluoride (NdF
3) and lithium fluoride (LiF) are used, but in addition to these, it is also possible to use barium fluoride (BaFz) and calcium fluoride (caFz) alone or by adding both at the same time. be. 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, but in the present invention, the raw material is not neodymium oxide as in the conventional case, but is a component of the electrolytic bath. Neodymium fluoride, which is also one of the

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 neodymium fluoride raw material inside is electrolytically reduced. Through this electrolytic reduction, the cathode 1
The metal neodymium deposited on the surface of the electrolytic bath 2 immediately forms a liquid alloy with the iron forming the cathode 10, drips from the surface of the cathode 10, and accumulates in a receiver placed in the electrolytic bath in the electrolytic cell 2. Note that at the temperature at which the above-mentioned predetermined solvent composition melts, the alloy formed on the iron cathode 10 is in a liquid state, and the specific gravity of the electrolytic bath made of such a molten salt is: As such liquid alloy is formed on the iron cathode 10, it falls below the surface of the cathode 10 since it is smaller than that of the formed alloy.

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, as described above, neodymium fluoride is used as the electrolytic raw material, unlike the conventional neodymium oxide. When neodymium fluoride is used as a raw material, since neodymium fluoride itself is the main component of the electrolytic bath, it is easy to supplement the amount consumed by electrolysis by supplying it. Electrolysis can be continued over a much wider range of raw material concentrations than in the case of As for the supply method of this raw material neodymium fluoride, it is common to add it to the surface of the electrolytic bath in the form of a powder, which is preferable because it dissolves quickly in the electrolytic bath. It is also possible to carry out the method by immersing a powder compact in an electrolytic bath.

Furthermore, compared to the electrolysis of neodymium oxide, in the electrolysis operation of neodymium fluoride, the permissible range of the concentration of the electrolytic raw material in the electrolytic region between the electrodes is much wider than that of the electrolysis of neodymium oxide. Even if there is a delay, it will not interfere with the continuation of electrolysis, and therefore there are no small restrictions on the supply position of the raw material neodymium fluoride and the amount of electricity supplied for electrolysis, such as when neodymium oxide is used as the raw material. This has the advantage that selection can be made more arbitrarily without being affected by

In addition, in the present invention, in order to produce a neodymium-iron alloy with few impurities and inclusions, it is necessary to lower the electrolysis temperature, and for this purpose, the electrolysis temperature is reduced by 35 to 76% (
Weight standards. (same below) neodymium fluoride, 20-60%
consisting essentially of fluoride (neodymium fluoride, lithium fluoride, barium fluoride, and・Even if a mixed molten salt (with a total amount of calcium nitride of 100%) is selected as the electrolytic bath, and the above raw material neodymium fluoride is added to such an electrolytic bath, during electrolysis The electrolyte bath will always be adjusted to have such a composition range.

Note that if the neodymium fluoride concentration in the electrolytic bath composition according to the present invention is less than the lower limit, that is, less than 35%, the electrolytic performance will deteriorate, and if it exceeds the upper limit concentration (76%), the electrolytic bath This causes problems such as the melting point of the material becoming too high. Additionally, 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 be 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. The total amount of these four components, namely neodymium fluoride, lithium fluoride, barium fluoride, and calcium fluoride, is substantially 100%.
In this way, an electrolytic bath is formed.

However, regarding such an electrolytic bath composition, if the electrolytic bath is a binary system consisting of only two components, neodymium fluoride and lithium fluoride, neodymium fluoride should account for at least 40% of the electrolytic bath. As mentioned above, it is desirable that lithium fluoride be prepared so that it is present in an amount of at least 24% or more. 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 that of the neodymium-iron alloy to be produced, so that during electrolysis, the neodymium-iron alloy produced is 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 within the 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, whereas if the electrolytic bath temperature is too low, This is because 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.

Therefore, in this temperature range, a neodymium-iron alloy with a high neodymium concentration containing 73% by weight or more of neodymium can be advantageously produced, and the produced alloy does not form a liquid layer in the receiver in this temperature range. This makes 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. Furthermore, 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 neodymium-iron alloy and is consumed, but the iron that is consumed by such electrolysis is supplemented, By sequentially immersing the cathode in the electrolytic bath, the desired neodymium-iron alloy can be produced continuously without interrupting the electrolytic operation. In this case, it is of course 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 supplement the worn cathode bone. 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 has a great advantage in that it is easy to increase the size of the electrolytic furnace.

Furthermore, in the electrolysis of neodymium fluoride using the carbon anode according to the present invention, the current density over the entire surface of the anode is always maintained within the range of 0.05 to 0.60 A/ffl during the electrolysis operation. It is desirable that 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 an abnormal phenomenon similar to this when neodymium oxide is used as a raw material tends to occur.

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, it is more preferable to maintain the current density over the entire surface of the anode between 0.10 and 0.40 A/-.

On the other hand, the current density of the cathode is allowed over a wide range of 0.50 to 55 A/cnt 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 is too small.
Productivity deteriorates and it becomes unindustrial. Furthermore, if this cathode current density becomes too high, the electrolytic voltage will increase significantly and the electrolytic results will deteriorate. In addition, for [E] of actual electrolytic operation, an additional 1.5 to 25 A/cr
It can be said that it is more preferable to maintain the cathode current density within the narrower range of A in order to maintain a narrow variation range of electrolysis voltage and facilitate electrolysis operation.

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, neodymium-iron alloy can be produced continuously without interrupting the 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 having an external shape that does not substantially change in the length direction, no inconvenience will occur in their continuous use.

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 steel.

Furthermore, the lower tank 22 and the lid body 24 each have fireproof insulation material layers 30, 32 made of brick, cask pull, alumina, etc. on the outside, and bath-resistant material layers 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 neodymium-iron alloy that is produced. However, in the present invention, such lining material 38
Therefore, it is recommended to use inexpensive iron materials.

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. Further, the bath-resistant material layer 34 is not necessarily required, and there is no problem in applying the lining material 38 directly on the fire-resistant heat insulating material 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. Here, two carbon anodes 42, 42 are shown among the anodes disposed facing the iron cathode 40, and graphite is suitably used as the material thereof.

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. Further, the anode 42 is connected to an anode lifting mechanism 46 as an anode insertion means.
The surface area of the immersion part can be moved up and down by the immersion depth intermittently or continuously to ensure a suitable anodic current density for electrolysis@1 series. It can be adjusted with. In addition,
The anode lifting mechanism 46° 46 can also have the function of electrical connection to the anode.

On the other hand, the cathode 40 is made of iron to be alloyed with metallic neodymium deposited by electrolytic reduction, one of which is shown here. Further, in FIG. 2, the cathode immersion portion is shown in a conical shape, showing traces of cathode consumption due to the formation of droplets of the neodymium-iron alloy. In addition,
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, or the like. The iron cathode 40 is also continuously or intermittently fed into the electrolytic bath 44 by a cathode elevating mechanism 48 serving as a cathode insertion means to compensate for wasted bone due to alloy formation. And this cathode world! The s mechanism 48 can also serve as an electrical connection to the cathode. Furthermore, 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 Liquid neodymium produced on 40-
The iron alloy 52 drips from the surface of the cathode and is collected in the formed alloy receiver 50 which opens directly below the cathode surface. The produced alloy receiver 50 is formed using a refractory metal that has low reactivity with the produced alloy 52, such as tungsten, kuntal, molybdenum, niobium, or an alloy thereof, or is made of a boron such as boron nitride. It can also be formed using materials such as ceramics such as compounds and oxides, or cermets. .

The electrolytic bath 44 is made of a fluoride mixed molten salt containing neodymium fluoride, which has been adjusted to have a composition according to the present invention described above, and its composition has a specific gravity that corresponds to the neodymium-iron alloy to be produced. Selected so that the specific gravity is below.

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 an electrolytic bath 44 having a predetermined composition is formed.

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 placed in the electrolytic furnace. 20 will be 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 formed alloy 52 is flowed out of the furnace and downward through the take-out pipe by penetrating the pipe and opening into the receiver 50.

Although not shown, a protective gas is supplied into the electrolytic furnace 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 to be equally restrictive by the description of such examples. It goes without saying that.

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 can be implemented in various embodiments 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 various embodiments that can be implemented are within the scope of the present invention.
should be understood.

Example 1 Neodymium-iron (Nd-Fe) alloy 11 having an average composition of 80% neodymium (by weight; the same applies hereinafter) and 18% iron
．． 3 kg were obtained as follows.

That is, in an apparatus having the same configuration as the electrolytic cell shown in FIG. Above, an electrolytic bath consisting of a binary fluoride mixed molten salt of neodymium fluoride and lithium fluoride was electrolyzed in an inert gas atmosphere. As the cathode, we used 6 wood 6 crane diameter iron wires arranged concentrically and immersed in the electrolytic bath in the center of the graphite crucible (in planar form), and as the anode we used iron wires arranged concentrically around the cathode. Six graphite rods of 80 φ were used, which were immersed (in planar form) in an electrolytic bath.

Using neodymium fluoride as a raw material, electrolysis was carried out for 24 hours while intermittently supplying the powder to the electrolytic bath while maintaining the electrolytic conditions within the range shown in Table 1 below. During this time, the electrolytic operation was able to continue very well, and the liquid neodymium-iron alloy was successively dripped and collected in a molybdenum receiver placed in the electrolytic bath. This accumulated alloy was taken out of the electrolytic furnace 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, neodymium oxide powder was used as a raw material in a similar manufacturing equipment, and this was continuously supplied to the electrolytic bath in the anode gas generation area (electrolysis area) between the cathode and the anode. Electrolysis was carried out under these conditions, but in that case, the formation of neodymium oxide sludge at the bottom of the electrolytic furnace became noticeable as the electrolysis continued, and anode effects frequently occurred. Therefore, an attempt was made to prevent the frequent occurrence of the anodic effect by further lowering the anode current density, but this attempt did not give satisfactory results. Furthermore, when the bath temperature was further raised, some improvement was observed in terms of operation, but the amount of harmful impurities in the produced alloy increased rapidly.

Example 2 20.9 kg of neodymium-iron alloy having an average composition of 88% neodymium and 10% iron was obtained at a lower temperature than in Example 1 by the following electrolytic operation.

First, a graphite crucible with iron lining on the inner surface as a bath-resistant material was used as a container for the electrolytic bath, and a tungsten container installed at the center of the bottom was used as a receiver for the produced alloy, and in effect the neodymium fluoride and An electrolytic bath consisting of a fluoride heptad molten salt of lithium fluoride and barium fluoride was electrolyzed in an inert gas atmosphere. As the cathode, Example 1
Three 12 mm diameter iron rods arranged in the same manner as above were used, and the same 80 mm diameter graphite rod as in Example 1 was used as an anode.

When neodymium fluoride was used as a raw material and the electrolytic conditions were maintained within the range shown in Table 1 below while being intermittently supplied to the electrolytic bath, good electrolytic operation continued for 48 hours. In addition, liquid neodymium-iron alloy was sequentially dripped and collected in the tungsten receiver.

Furthermore, the generated alloy in this collected receiver was Example 1
It was also possible to extract it in liquid form.

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.

For comparison, we attempted electrolysis using neodymium oxide as a raw material in the same manner as in Example 1 using the same manufacturing equipment, but the formation of neodymium oxide sludge and the occurrence of the anode effect became even more severe, and the electrolysis failed. It was not possible to continue the operation.

Example 3 6.6 kg of neodymium-iron alloy with an average composition of 84% neodymium and 14% iron was obtained at a lower temperature than in Example 1 by adopting the following electrolytic operation.

That is, an iron crucible is used as a bath-resistant container of an electrolytic cell, and a produced alloy receiver similar to that in Example 1 is installed in the center of the bottom of the crucible, and essentially a binary fluoride mixture of neodymium fluoride and lithium fluoride is mixed. An electrolytic bath consisting of a molten salt was subjected to electrolysis under an inert gas atmosphere.

As the negative electrode (F), a 12 uφ iron rod similar to that in Example 2 was used, and as the anode, five 60 μφ graphite rods arranged concentrically around the cathode (in plan view) were used.

While continuously supplying neodymium fluoride as a raw material to the electrolytic bath, it was possible to maintain good electrolytic operation for 24 hours while maintaining the electrolytic conditions within the range shown in Table 1 below. In addition, liquid neodymium-iron alloy was sequentially dropped and collected in the molybdenum container. Further, the accumulated alloy was taken out of the electrolytic cell in a liquid state in the same manner as in Example I.

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.

In this example, by suppressing the upper limit of the cathode current density and keeping the cathode current density within a narrow range, an increase in voltage during electrolysis was prevented and the voltage fluctuation width was improved.

Example 4 4.6 kg of neodymium-iron alloy having an average composition of 90% neodymium and 8% iron was obtained at a lower temperature than in Examples 2 and 3 by the following electrolytic operation.

That is, as in Example 3, an iron crucible is used as a bath-resistant container of an electrolytic cell, and a produced alloy receiver similar to that in Example 2 is installed in the center of the bottom of the crucible, and essentially neodymium fluoride and lithium fluoride are An electrolytic bath consisting of a binary fluoride mixed molten salt was electrolyzed in an inert gas atmosphere. A single iron rod of 34 nφ was used as the cathode, and a graphite rod of 60 vaφ similar to that in Example 3 was used as the anode.

Then, using neodymium fluoride as a raw material, electrolysis is carried out for 18 hours by continuously supplying it to the electrolytic bath and maintaining the electrolytic conditions within the range shown in Table 1 below. I was able to continue doing this. Note that the liquid neodymium-iron alloy was sequentially dropped and stored in the tungsten container. This accumulated alloy was taken out from the electrolytic cell every 8 hours using a vacuum suction type alloy recovery device having a nozzle as shown in FIG. Note that the nozzle portion of this vacuum suction type alloy recovery device was preheated before being inserted into the electrolytic cell.

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 neodymium fluoride according to the present invention, a neodymium-iron alloy with a high neodymium content can be produced all at once. The resulting alloy is found to be a neodymium-iron alloy with a low content of impurities such as oxygen that deteriorate 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. Further, in this example, impurities other than those shown in Table 2 are substantially composed of rare earth metals other than neodymium.

Furthermore, Table 2 shows the analysis results of commercially available neodymium metals for comparison, but these commercially available neodymium metals have a high content of impurities such as oxygen that are harmful to magnet materials. There is.

Furthermore, among the above examples, in Examples 1 to 3, it is easy to continue electrolysis for a longer period of time, and even in such cases, the same results as in each example can be obtained. Confirm that you can get it.

has been done.

[Brief explanation of the drawing]

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 Fig. 1

Claims (11)

[Claims] (1) Using an iron cathode and a carbon anode, a neodymium compound is electrolytically reduced in a molten salt electrolytic bath, and the generated neodymium is deposited on the iron cathode and alloyed with the iron constituting the cathode. - When forming the iron alloy, neodymium fluoride is used as the neodymium compound, and the molten salt electrolytic bath containing the neodymium compound is
substantially 35-76% by weight neodymium fluoride, 20-6
The neodymium-iron alloy is deposited on the iron cathode in a liquid state while being adjusted to consist of 0% by weight of lithium fluoride, up to 40% by weight of barium fluoride and up to 20% by weight of calcium fluoride. The neodymium-iron alloy in the liquid state is dropped as droplets into a receiver having an opening in the electrolytic bath below the iron cathode to collect as a liquid layer, and further from the liquid layer in the receiver. A method for producing a neodymium-iron master alloy, characterized in that the neodymium-iron alloy is extracted in a liquid state. (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
0.60A/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 neodymium compound is substantially composed of neodymium fluoride and lithium fluoride, and the neodymium fluoride is at least 40% by weight or more and the lithium fluoride is at least 24% by weight. The manufacturing method according to any one of claims 1 to 4, wherein the manufacturing method is adjusted so that each of the above exists. (6) substantially neodymium fluoride and lithium fluoride;
Also, an electrolytic cell made of a fire-resistant material that houses a molten salt electrolytic bath made of barium fluoride and calcium fluoride added as necessary, and a lining applied to the inner surface of the electrolytic cell in contact with the bath. and a long carbon anode whose shape does not substantially change in the longitudinal direction, which is inserted and immersed in the molten salt electrolytic bath of the electrolytic tank; an elongated iron cathode whose shape does not substantially change in the longitudinal direction; and an elongated iron cathode arranged in the molten salt electrolytic bath of the electrolytic cell so that the opening is located below the iron cathode; Droplets of neodymium-iron alloy formed on the iron cathode by electrolytic reduction of neodymium fluoride by a direct current applied between a carbon anode and an iron cathode, for collecting such droplets of neodymium-iron alloy; a liquid alloy receiver for taking out the liquid neodymium-iron alloy in the alloy receiver to the outside of the electrolytic cell; An apparatus for producing a neodymium-iron master alloy, comprising: a cathode inserting means for inserting a cathode into the molten salt electrolytic bath of the electrolytic cell so as to obtain a predetermined current density according to consumption. (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 neodymium fluoride as a raw material into the electrolytic cell. (9) The liquid alloy extraction means has a pipe-shaped nozzle inserted into the liquid neodymium-iron alloy in the alloy receiver, and sucks up the neodymium-iron alloy by vacuum suction through the nozzle, and The manufacturing apparatus according to any one of claims 6 to 8, which is adapted to be taken out. (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.