JPS6312949B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to an apparatus for producing neodymium-iron alloys, particularly neodymium-iron alloys, which have a high neodymium content and are suitable as master alloys for high-performance permanent magnets, and which contain harmful impurities and inclusions. The present invention relates to an apparatus suitable for continuously producing a neodymium-iron alloy with a low content of. (Background of the Invention) Recently, rare earth-iron and rare earth-iron-boron permanent magnets have been attracting attention as high-performance magnets that do not contain expensive samarium or cobalt and have better magnetic properties than hard ferrite. . Among them, neodymium-iron-boron magnets have a maximum energy product (BH)max of 36MGOe or more,
It is recognized that it is extremely superior in terms of specific gravity and mechanical strength (for example, JP-A-59-46008
(Refer to the publication number, etc.) 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 has become necessary to establish an industrial method to do so. By the way, neodymium metal has had almost no use in the past, and its production methods generally involve using active metals,
In particular, only the reduction method using calcium and the molten salt electrolysis method are known, and no industrial production method has been fully established. Therefore, even if there is an industrial method for producing 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 method for producing neodymium-iron alloys that can be considered based on the conventional state of the art is electrolysis in a chloride electrolytic bath, which falls under the category of molten salt electrolysis (for example, Jiro Shiokawa et al., "Electrochemistry" Vol. 35, 1967, No.
496, etc.) and electrolysis of oxides (Nd ₂ O ₃ ) dissolved in a fluoride electrolytic bath (E. Morris et al., ``U.S.
Bur.Min., Rep.Invest.”, No.6957, 1967)
Also, electrolysis is carried out by supplying neodymium oxide into a fluoride electrolytic bath, which belongs to the so-called consumable cathode method.
Examples of research on obtaining neodymium-iron alloys (E. Morris et al., "USBur.Min., Rep.Invest.", No.7146,
(see 1968), but each method has various problems, and each method uses neodymium-
This method is not fully satisfactory as an industrial or practical method for continuously producing iron alloys. For this reason, the inventors of the present invention have previously filed a patent application filed in
As No. 20773, using the conventional consumable cathode method,
By electrolytic reduction using neodymium fluoride as a raw material, neodymium-iron alloys, especially neodymium-iron master alloys particularly suitable for the production of high-performance permanent magnets, can be produced advantageously on a large scale and continuously. We have clarified the technology that can produce it. That is, the technique proposed earlier 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 reduces the amount of iron constituting the cathode. to form a neodymium-iron alloy, neodymium fluoride is used as the neodymium compound as the neodymium raw material, and the neodymium fluoride is used as one of the main components of the molten salt electrolytic bath. This allows the neodymium-iron alloy to be produced in one step of the electrolytic reduction operation, and has a low content of impurities such as oxygen and inclusions that adversely affect the magnetic properties of the permanent magnet. , and a neodymium-iron alloy with a high neodymium content can now be effectively produced in one step. By the way, round rods, wires, wire bundles, grooved round rods, nets, etc. have been used or proposed as common cathodes for this type of molten salt electrolysis, but iron-consumable cathodes such as those described above In the electrolytic reduction method that produces a neodymium-iron alloy, the key point is that neodymium precipitates on the surface of the cathode and reacts with the iron of the cathode on the surface to produce a liquid neodymium-iron alloy. , and since this neodymium precipitation reaction is a surface reaction, if a rod-shaped cathode with a too large diameter is used as the iron cathode, it will take time for the iron to be consumed to the center of the cathode. In order to ensure current density, the length of the cathode that is inserted and immersed in the electrolytic bath becomes long, causing problems such as colliding with the bottom of the electrolytic bath, which hinders the electrolytic operation. Therefore, in practice, iron cathodes can only be used up to a certain diameter when they are rod-shaped. In addition, when electrolytically producing neodymium-iron alloy by ^the consumable cathode method using neodymium fluoride as a raw material as described above, the anode current density is but
It is much smaller at around 0.05 to 0.06A/ ^cm2 , and therefore,
Under constant current, the anode surface area must be much larger than the cathode surface area, and
When maintaining the temperature of the electrolytic bath, which is preferably set in the range of 950°C, by the Joule heat generated by the electrolytic current, the electrolytic bath must be kept within a narrow range during constant current electrolysis. This causes large fluctuations in temperature, making it difficult to carry out effective electrolytic reduction operations. By the way, in order to obtain the above-mentioned large current density difference, a configuration in which multiple anodes are arranged opposite to a cathode is generally adopted. When using a large number of poles, it becomes necessary to increase the distance between the poles due to geometrical constraints.
For this reason, the bath voltage drop based on the resistance of the electrolytic bath in that part increases, and the electrolytic bath voltage becomes too large, causing a problem of deteriorating the electricity consumption rate of electrolysis, and the amount of heat generated by the electrolytic current ( This causes problems such as excessive heating of the bath, which disturbs the heat balance and raises the bath temperature too much. (Summary of the Invention) The present invention has been made against the background of the above, and its purpose is to obtain a neodymium-iron alloy, particularly suitable for producing high-performance permanent magnets. The purpose is to provide an apparatus that can continuously manufacture neodymium-iron master alloys on a large scale, and another purpose is to produce neodymium-iron alloys by the consumable cathode method using neodymium fluoride as a raw material. In electrolytic production equipment, the iron cathode can be effectively consumed, and continuous electrolytic reduction operations can be performed advantageously, and the distance between the electrodes does not become large even when multiple large-diameter anodes are used. In this way, it is an object of the present invention to provide a structure that can effectively increase the degree of freedom in device design. That is, in order to achieve the above objects, the present invention provides (a) a molten salt 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 that accommodates an electrolytic bath; (b) a lining applied to an inner surface of the electrolytic cell in contact with the bath; and (c) inserted into a molten salt electrolytic bath of the electrolytic cell. ,
(d) a longitudinal carbon anode that is immersed and has no substantially longitudinal shape change; (e) with a longitudinally hollow tubular iron cathode, without
The neodymium fluoride is electrolyzed by a direct current applied between the carbon anode and the iron cathode, which is placed in the molten salt electrolytic bath of the electrolytic cell so that the opening is located below the iron cathode. (f) an alloy receiver for collecting neodymium-iron alloy droplets, onto which the neodymium-iron alloy droplets formed on the iron cathode by reduction are dropped; (g) liquid alloy extraction means for taking out the neodymium-iron alloy out of the electrolytic cell; a cathode insertion means for inserting the cathode into the bath so as to obtain a predetermined current density;
It uses a device containing However, such a neodymium-iron 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 It is desirable to have a raw material supply means for supplying neodymium fluoride into the electrolytic cell, and the lining applied to the inner surface of the electrolytic cell may be made of a refractory metal material such as molybdenum or tungsten. , an inexpensive iron material can be suitably used. Through studies conducted by the present inventors, it has been discovered that such iron materials exhibit excellent bath resistance and corrosion resistance, and can serve as a good lining material for fluoride electrolytic baths. In addition, in the present invention, neodymium in a liquid state collected in an alloy receiver placed in an electrolytic cell is used.
In order to effectively take out the iron alloy out of the electrolytic cell in a liquid state, the liquid alloy removal means has a pipe-shaped nozzle inserted into the liquid neodymium-iron alloy in the alloy receiver. configured,
From the viewpoint of industrial implementation, it is advantageous to suck up the neodymium-iron alloy through the nozzle by vacuum suction and take it out of the electrolytic cell. Furthermore, the tubular iron cathode of the present invention can also serve as the raw material supply means by utilizing the hollow part in its longitudinal direction. A protective gas supply means is connected such that a positive pressure of protective gas is introduced into the hollow space of the iron cathode by the protective gas supply means, thereby preventing the introduction of such protective gas into the electrolytic bath. By blowing, it is possible to stir the electrolytic bath and prevent corrosion of the internal space of the cathode tube. By using such an apparatus according to the present invention, a neodymium-iron alloy can be produced in one step of the electrolytic reduction operation, and moreover, it is free from impurities such as oxygen and inclusions that adversely affect the magnetic properties of the permanent magnet. It has now become possible to effectively produce a neodymium-iron alloy in one step, which has a low content of carbon dioxide and a high neodymium content. Furthermore, since a solid cathode is used, the cathode is not only easy to handle, but also allows for continuous operation without interrupting electrolysis since the produced alloy can be taken out as a liquid alloy during electrolysis. As a result of continuous low-temperature operation, which is an advantage of the cathode exhaustion method, the electrolytic performance and the quality of the produced alloy are effectively improved. In addition, according to the present invention, the size of the device can be increased,
Continuous operation can be easily achieved, and furthermore, it is possible to avoid all difficulties in continuous operation in electrolytic production of fluoride-oxide mixed molten salt using neodymium oxide as a raw material. It is possible to achieve high current efficiency over a long period of time, which cannot be achieved by electrolytic production methods of chloride mixed molten salts using chloride as a raw material. As described above, according to the present invention, it has become possible to economically and continuously produce a neodymium-iron alloy with high neodymium content and low impurity content, which is suitable as a raw material for high-performance permanent magnets, on a large scale. Such a neodymium-iron alloy is also advantageously used as an intermediate raw material for producing neodymium metal. (Specific description of the structure) A specific example of the apparatus according to the present invention is schematically shown in FIG. It is composed of a lid body 14 that covers the section. Moreover, the outside of these lower tank 12 and lid body 14,
Usually, it is composed of tank outer frames 16 and 18 made of metal such as steel. Furthermore, the lower tank 12 and the lid body 14 each have fireproof insulation layers 20, 22 made of bricks, castable alumina, etc. on the outside, and bath-resistant material layers 24, 26 made of graphite, carbonaceous stamp material, etc. on the inside. Arranged and configured. A lining material 28 is provided on the inner bath-contacting surface of the inner bath-resistant material layer 24 of the lower tank 12.
The bath contact surface is coated. This lining material 28 prevents impurities from entering the bath-resistant material layer 24, and if it is made of a refractory metal such as tungsten or molybdenum, it serves as a receiver for the liquid neodymium-iron alloy that is generated. It can also serve as However, in the present invention, such lining material 28
It is recommended to use an inexpensive iron material as a material.
This is because, through studies conducted by the present inventors, it has been found that inexpensive iron exhibits excellent corrosion resistance and is a good lining material for fluoride electrolytic baths. Further, the bath-resistant material layer 24 is not necessarily necessary, and there is no problem in applying the lining material 28 directly on the fire-resistant heat insulating material layer 20. Further, inside the electrolytic cell 10 surrounded by the lining material 28, there is a molten salt electrolytic bath 3.
A solvent constituting 0 is charged. The solvent used is neodymium fluoride (NdF ₃ ).
In addition to these, barium fluoride (BaF ₂ ) and calcium fluoride (CaF ₂ ) can be used alone or in combination. Among them,
In producing a neodymium-iron alloy with few impurities and inclusions, it is preferable to lower the electrolysis temperature, and for this purpose, such a molten salt electrolytic bath 30
is essentially 35-76% (by weight, same hereinafter) neodymium fluoride, 20-60% lithium fluoride, 40
% of barium fluoride and up to 20% of calcium fluoride; Even when neodymium chloride is added, the electrolytic bath is always adjusted to have a composition within this range during electrolysis. Further, an iron cathode 32 is inserted through the lid 14 of the electrolytic cell 10, and a plurality of carbon anodes 34 are arranged concentrically around the iron cathode 32 so as to face the iron cathode 32. It is provided,
Further, both of the electrodes 32 and 34 are connected to an electrolytic bath 30 containing the predetermined molten salt contained in the lower tank 12.
It is adapted to be immersed therein over a length that provides a predetermined current density. Here, two carbon anodes 34, 34 are shown among the anodes disposed facing the iron cathode 32, and graphite is suitably used as the material thereof. Furthermore, these carbon anodes 34, 34 are rod-shaped,
It is used in the form of a plate, a tube, etc., and it can also be grooved in a known manner to increase the anode surface area of the part immersed in the electrolytic bath 30 and reduce the anode current density. In addition, in the drawing, the carbon anodes 34, 34 are slightly inclined at the anode immersion part, showing traces of anode wear due to electrolysis. An electric lead made of a suitable conductor such as metal may be attached to the anode 34 for power supply. Further, the anode 34 is moved up and down by an anode lifting mechanism 36 serving as an anode insertion means, so that an appropriate anode current density of 0.05 to 0.05 for continuous electrolysis is achieved.
The surface area of the immersion part can be adjusted intermittently or continuously by adjusting the immersion depth so that 0.60 A/cm ² , preferably 0.10 to 0.40 A/cm ² is secured. Note that the anode lifting and lowering mechanisms 36, 36 can also have the function of electrically connecting to the anode. On the other hand, the cathode 32 is composed of a pipe-like or tubular member made of an iron material to be alloyed with metallic neodymium deposited by electrolytic reduction, and is connected to a cathode lifting mechanism 38 as a cathode insertion means. Therefore, the amount consumed by alloy formation is compensated for and the material is continuously or intermittently fed into the electrolytic bath 30. In addition, this cathode lifting mechanism 38 here also has the function of electrically connecting to the cathode 32, and the surface of the iron cathode 32 other than the immersed part is protected with a suitable protective sleeve or the like to prevent corrosion. Even if you are used to it, it doesn't make any difference. A protective gas supply device 40 is provided at the opening of the pipe-shaped iron cathode 32 on the outside of the electrolytic cell 10.
is provided, and such a protective gas supply device 40
The atmosphere inside the hollow portion of the iron cathode 32 is made up of a positive-pressure protective gas by the protective gas supplied from the iron cathode 32, for example, an inert gas such as a rare gas. In addition, a produced alloy receiver 42 is arranged on the bottom of the lower tank 12 in the electrolytic bath 30 so that the receiver opening is located below the pipe-shaped iron cathode 32, and the cathode 32 and anode The liquid neodymium-iron alloy 44 produced on the iron cathode 32 by electrolytic reduction of the neodymium fluoride raw material in the electrolytic bath by applying a predetermined direct current between the iron cathode 34 and the It drips from the surface of the cathode and is collected in the produced alloy receiver 42 which opens directly below it. The produced alloy receiver 42 is formed using a refractory metal that has low reactivity with the produced alloy 44, such as tungsten, tantalum, molybdenum, niobium, or an alloy thereof, or a boron such as boron nitride. It can also be formed using materials such as ceramics such as compounds or oxides, or cermets. In an apparatus having such a structure, the neodymium fluoride raw material in the electrolytic bath 30 is electrolytically reduced by direct current applied between the iron cathode 32 and the carbon anode 34, and as described above, The metal neodymium deposited on the iron cathode 32 immediately forms a liquid alloy with the iron constituting the cathode 32, and drips from the surface of the cathode 32 to the receiver 42 installed in the electrolytic bath 30 in the electrolytic cell 10. It will be gathered inside. Note that at the temperature employed during this electrolytic reduction, which is generally a temperature of 770°C to 950°C, the alloy formed on the iron cathode 32 is in a liquid state, and is made of a molten salt as described above. Since the specific gravity of the electrolytic bath 30 is smaller than that of the produced alloy, as the liquid alloy is produced on the iron cathode 32, it falls below the surface of the cathode 32. It is. In this way, as the liquid neodymium-iron alloy 44 is formed on the surface of the iron cathode 32, the iron cathode 32 itself is consumed, and therefore, as the electrolytic reduction operation progresses, the iron cathode 32 is
Although the diameter of the iron cathode 32 is gradually reduced, since the iron cathode 32 has a pipe shape, a predetermined length of the cathode is completely consumed due to wear of the thick wall (tube wall). Therefore, problems such as the cathode remaining undissolved in an elongated state and reaching the bottom of the electrolytic bath (electrolytic bath), which occur when a thick rod-shaped cathode is used, do not occur. In particular, when a plurality of large-diameter carbon anodes 34 are arranged to face the cathode 32, as described above,
By forming the iron cathode 32 into a pipe shape, its consumption can be effectively achieved, so a pipe-shaped iron cathode 32 with a large diameter can be used, which prevents the distance between the electrodes from becoming too large. The underlying problems such as a voltage drop in the bath section, an increase in the voltage of the electrolytic cell, a deterioration in the power unit consumption of electrolysis, and a large fluctuation (excessive rise) in the temperature of the electrolytic bath can be effectively solved. The outer diameter of the iron cathode 32 can be appropriately selected from a wide range depending on the diameter of the carbon anode 34 used, so that a desired cathode current density of 0.50 to 55 A/cm ² can be obtained. However, if the outside diameter of the tube is made large, by making the wall thickness of the tube effective enough to consume the tube, the above-mentioned problems can be avoided and continuous electrolytic operation can be carried out effectively. It is possible to do so. Of course, the cross-sectional shape of the tube of the iron cathode 32 is generally circular, but is not limited to this. Longitudinally hollow tubes of various cross-sectional shapes, such as , rectangular, star-shaped, etc., can be used. Regarding the arrangement of the electrodes, as long as the current density is within a predetermined range and the anode 34 faces the cathode 32, the electrodes may be arranged concentrically around the iron cathode 32 as shown in the example. It goes without saying that other arrangements than the arrangement of the carbon anodes 34 may be adopted as appropriate. Further, the electrolytic raw material consumed by the electrolytic operation in such an electrolyzer is supplied to the raw material supply device 46.
The raw material is supplied through a raw material supply hole 48 provided in the lid 14 to form an electrolytic bath 30 of a predetermined composition, and is also dripped from the iron cathode 32 and stored in the receiver 42. Generated alloy 44
When a predetermined amount of the alloy has accumulated, it is collected in a liquid state by a predetermined alloy recovery mechanism (removal means).
For example, a pipe-shaped vacuum suction nozzle 50 is inserted into the electrolytic bath 30 through the produced alloy suction hole 52, and the tip of the nozzle 50 is immersed in the produced alloy 44 in the produced alloy receiver 42. It is sucked up by suction using the vacuum suction effect of the vacuum device and taken out of the electrolytic cell 10. Furthermore, such an electrolytic cell 1
0 contains an electrolytic bath 30, a generated alloy 44, and an electrode 3.
2, 34. In order to prevent the deterioration of the constituent materials of the electrolytic cell 10 and to avoid the mixing of harmful impurities and inclusions into the produced alloy 44, the above-mentioned protective gas has been introduced. The gas generated by the electrolytic reduction operation is discharged to the outside through the exhaust gas outlet 54 together with the introduced protective gas. By the way, here, the raw material supply means 46, 48
The electrolytic cell 10 has a structure in which the produced alloy extraction means 50, 52, a protective gas supply means (not shown), etc. are separately provided in the electrolytic cell 10, but as described above,
By forming the iron cathode 32 into a pipe shape, the hollow part can be used to supply protective gas or neodymium fluoride, which is an electrolytic raw material, and can also be used as a hole for taking out the produced alloy. Is possible. That is, as shown in the example, if the protective gas is introduced into the tube interior space under positive pressure from the protective gas supply device 40 provided at the external opening of the iron cathode 32, corrosion caused by outside air inside the hollow part of the cathode 32 can be prevented. Furthermore, it is possible to effectively prevent the electrolytic bath 30 from entering the tube and a current having a low current density below the target current density flowing into this portion. Furthermore, the amount of protective gas supplied from the protective gas supply device 40 into the pipe-shaped iron cathode 32 is increased, and the electrolytic bath 3 is
By blowing a protective gas into the electrolytic bath 10, the electrolytic bath 30 can be effectively stirred, and the dissolution of the raw material neodymium fluoride in the electrolytic bath 30 can be promoted. It can also be used as a protective gas to fill the space above the bath 30. On the other hand, at the same time as the protective gas supplied from the protective gas supply device 40 as described above is blown, the raw material neodymium fluoride powder is blown into the electrolytic bath 30 through the hollow part of the pipe-shaped iron cathode 32. This makes it possible to simultaneously supply raw materials and promote dissolution into the electrolytic bath 30, and also to
This provides an advantage in that the need to provide the raw material supply hole 48 in the lid 14 is eliminated. Of course, the raw material, neodymium fluoride, is not only supplied as a powder into the electrolytic bath 30, but also as a solid product molded into a certain shape. The inside of the tubular hollow part of the iron cathode 32 can also be used as the supply hole. In such a configuration in which the iron cathode 32 is used inside the tubular hollow part, the cathode tube itself can be used as the protective gas introduction tube, or another tube of an appropriate diameter can be used. , it is also possible to adopt a form in which it is inserted into the hollow interior of a tubular cathode. In addition, when taking out a predetermined amount of produced alloy 44 stored in the produced alloy receiver 42 to the outside of the electrolytic cell 10 using the vacuum suction nozzle 50, the internal space of the iron cathode 32 is used as an insertion hole for the nozzle 50 to produce the produced alloy. Alloy suction hole 5
2, the tip of the nozzle 50 is inserted into the produced alloy 44 of the produced alloy receiver 42 in the electrolytic bath 30 through the tubular interior of the iron cathode 32, and the produced alloy 44 is sucked by vacuum suction. It is also possible to collect it outside the tank. However, the produced alloy 44 in the produced alloy receiver 42 can be taken out by vacuum suction as described above.
Although the suction extraction method described in No. 4 is a preferred method, it is by no means limited to this.
Instead of this, a take-out pipe is provided that penetrates the lower part of the electrolytic cell 10 (lower tank 12), and the tip of this take-out pipe is further passed through the produced alloy receiver 42,
It is also possible to employ an alloy recovery mechanism that opens in the receiver 42 and drains the produced alloy 44 downwardly outside the tank through the take-out pipe. (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 above-mentioned specific explanation of the present invention and the following examples, and as long as it does not depart from the spirit of the present invention, various embodiments can be implemented based on the knowledge of those skilled in the art. It should be understood that any of the various embodiments that can be implemented in various ways fall within the scope of the present invention. Example 1 Neodymium-iron (Nd-
10.0Kg of Fe) alloy was obtained as follows. That is, in an apparatus having the same configuration as the electrolytic cell shown in FIG. An electrolytic bath consisting of a ternary fluoride mixed molten salt of neodymium fluoride, lithium fluoride, and barium fluoride was electrolyzed in an inert gas atmosphere. The cathode is a 34mmφ (outer diameter), 3mmt (wall thickness) whose lower part is immersed in the electrolytic bath so that it is located in the center of the iron crucible.
An iron tube with its upper end sealed was used, and six 80 mm diameter graphite rods were used as anodes, arranged concentrically around the cathode and immersed in the electrolytic bath. Using neodymium fluoride 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.
Conducted electrolysis. 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 into an 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. Example 2 6.7 kg of neodymium-iron alloy having an average composition of 85% neodymium and 13% iron was obtained as follows. In other words, a graphite crucible with iron lining on the inner surface as a bath-resistant material is used as a container for the electrolytic bath, and a tungsten container installed at the center of the bottom is used as a receiver for the produced alloy, in effect, the neodymium fluoride and An electrolytic bath consisting of a binary fluoride mixed molten salt of lithium fluoride was electrolyzed in an inert gas atmosphere. As the cathode, the same 34 mm as in Example 1 was used.
An iron tube with a diameter of 3 mm was used, and as an anode, five graphite rods with a diameter of 60 mm arranged in the same manner as in Example 1 were used. A protective gas inlet cap was attached to the upper end of the cathode iron tube so that protective gas could be gently blown into the electrolytic bath during electrolysis. Using neodymium fluoride as a raw material, electrolysis was carried out for 24 hours while continuously 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 tungsten 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. Example 3 Using the same apparatus as in Example 1, an electrolytic bath consisting essentially of a binary fluoride mixed molten salt of neodymium fluoride and lithium fluoride was used in an inert gas atmosphere. I did electrolysis. As a cathode, a 110mmφ, 14mm electrode whose lower part was immersed in the electrolytic bath was placed in the center of the iron crucible.
mmt iron tube was used, and eight 80 mmφ graphite rods were used as anodes, which were arranged concentrically around the cathode and immersed in the electrolytic bath. Then, the neodymium fluoride powder used as the raw material was press-molded into a dice shape and placed in an iron basket, passed through the tube from the upper end of the cathode iron tube.
It was immersed in an electrolytic bath and electrolyzed for 8 hours while maintaining the electrolytic conditions within the range shown in Table 1 below. At this time, the upper end of the cathode was electrically insulated and gas-sealed. The electrolytic operation can continue successfully, and the alloy accumulated in the receiver is
After the electrolysis was completed, the alloy was taken out of the electrolytic cell using a vacuum suction type alloy recovery device having a vacuum suction nozzle.
Furthermore, the entire amount of neodymium fluoride in the iron basket had been dissolved. The electrolytic results obtained by such electrolytic operation and the analysis results of the produced alloy are shown in Tables 1 and 2 below.

【table】

【table】

[Table] As is clear from the results in Tables 1 and 2, by electrolyzing neodymium fluoride according to the present invention, neodymium with a high neodymium content and a low content of impurities such as oxygen can be produced. - Iron alloys were produced all at once in one step. In addition, the numerical values of the components in Table 2 are the average values of the analysis values of the extracted alloys,
Further, in this example, impurities other than those shown in Table 2 are substantially composed of rare earth metals other than neodymium. Table 2 also 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. It is recognized that In addition, it was confirmed that in Examples 1 and 2 among the above examples, it was easy to perform electrolysis continuously over a longer period of time, and results similar to those in each example could be obtained. has been done.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the structure of an electrolytic cell according to the present invention. 10: Electrolytic tank, 12: Lower tank, 14: Lid, 2
0, 22: Fireproof insulation material layer, 24, 26: Bath-resistant material layer, 28: Lining material, 30: Electrolytic bath, 32:
Iron cathode, 34: carbon anode, 36: anode lifting mechanism,
38: Cathode lifting mechanism, 40: Protective gas supply device,
42: Generated alloy receiver, 44: Neodymium-iron alloy,
46: Raw material supply device, 50: Vacuum suction nozzle.

Claims (1)

[Scope of Claims] 1. Consisting of a refractory material containing a molten salt electrolytic bath consisting essentially of neodymium fluoride and lithium fluoride, and optionally added barium fluoride and calcium fluoride. a lining provided on the inner surface of the electrolytic cell in contact with the bath; and a longitudinal section whose shape does not substantially change in the longitudinal direction, which is inserted into and immersed in the molten salt electrolytic bath of the electrolytic cell. a carbon anode, which is inserted into and immersed in the molten salt electrolytic bath of the electrolyzer, and has a longitudinally hollow tubular iron cathode with substantially no change in shape in the longitudinal direction; disposed in the molten salt electrolytic bath of the electrolytic cell so as to be located below the cathode,
Neodymium-iron alloy droplets produced on the iron cathode by electrolytic reduction of neodymium fluoride by a direct current applied between the carbon anode and the iron cathode are dropped. an alloy receiver for collecting the neodymium-iron alloy in the liquid state in the alloy receiver, a liquid alloy take-out means for taking out the liquid neodymium-iron alloy in the alloy receiver to the outside of the electrolytic cell; and a cathode insertion means for inserting the cathode into the molten salt electrolytic bath of the electrolytic cell so as to obtain a predetermined current density as the cathode is consumed. . 2. The manufacturing apparatus according to claim 1, 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. 3. The manufacturing apparatus according to claim 1 or 2, comprising a raw material supply means for supplying neodymium fluoride as a raw material into the electrolytic cell. 4. The manufacturing apparatus according to claim 3, wherein the iron cathode also serves as the raw material supply means, and a predetermined neodymium fluoride raw material is supplied into the electrolytic cell through a hollow part of the iron cathode. 5. The liquid alloy extraction means has a pipe-shaped nozzle that is inserted into the liquid neodymium-iron alloy in the alloy receiver, and sucks up the neodymium-iron alloy by vacuum suction through the nozzle to the outside of the electrolytic cell. Claims 1 to 3 taken out
2. Manufacturing equipment according to any of paragraphs. 6. A patent claim in which a predetermined protective gas supply means is connected to the opening of the iron cathode on the outside of the electrolytic cell, and the protective gas supply means introduces a positive pressure protective gas into the hollow part of the iron cathode. The manufacturing apparatus according to any one of items 1 to 5. 7. The manufacturing apparatus according to any one of claims 1 to 6, wherein the lining is made of iron material. 8. The manufacturing apparatus according to any one of claims 1 to 7, wherein the carbon anode is a graphite electrode.