JPS61291988A - Method and apparatus for producing neodymium-iron alloy - Google Patents

Abstract

PURPOSE:To continuously produce a base alloy suitable for a permanent magnet having high performance in case of using an Fe cathode in an electrolytic bath to form Nd-Fe alloy by adjusting the immersed depth of the Fe cathode on the basis of an electrolytic voltage value and controlling the bath temp. CONSTITUTION:An electrolytic bath 30 of the following molten salt is incorporated in an electrolytic cell 10 which has NdF3 and LiF as an essential component and is added with BaF2 and CaF2 if necessary. An Fe cathode 32 and the carbon anodes 34 are inserted in the electrolytic cell and these under ends are immersed in the electrolytic bath 30. Nd-Fe alloy is formed by reducing electrolytically an Nd compd. in the electrolytic bath and depositing the produced Nd on the Fe cathode 32. When the voltage value is detected with a voltmeter 44 during the electrolytic operation and the detected value reaches the preset value and above, the cathode 32 is transferred to the lower part by actuating a cathode elevator 38 with the command of a controller 46 and the immersed depth is increased. Also the temp. of the electrolyte is controlled in the range of 770-950 deg.C. The produced alloy 52 is received in a receiver 50.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method and apparatus for producing a neodymium-iron alloy, and particularly to a neodymium-iron alloy, particularly a neodymium-containing material suitable as a master alloy for high-performance permanent magnets. The present invention relates to an effective method and apparatus suitable for the continuous production of neodymium-iron alloys in high quantities and 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 the highest energy product: (BH) max
is 36 MGOe or more, and is recognized to be extremely excellent in terms of specific gravity and mechanical strength (see, for example, Japanese Patent Laid-Open No. 59-46008). 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 had almost no use in the past, and the only known manufacturing methods are reduction with active metals, especially calcium, and molten salt electrolysis, and industrial manufacturing methods have not been fully established. Not yet. 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 such circumstances, the method for producing neodymium-iron alloys that can be considered from 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 Shiyo et al., "Electrochemistry," Vol. 35). Vol., 1967, p. 496, etc.) and electrolysis of an oxide (NdzOt) dissolved in a fluoride electrolytic bath (
E. Maurice et al., “Nie Nis Bureau of Mines, Report of Investigations.”
, No. 6957, 1967), and a research example in which a neodymium-iron alloy was obtained by supplying neodymium oxide into a fluoride electrolytic bath and performing electrolysis, which belongs to the so-called consumable cathode method (E., Morris Others, “Nie Nis Bureau of
Mines, Report of Investigations”, 7146. (see 1968), but each method has various problems;
This method has not been fully satisfactory as an industrial or practical method for continuously producing neodymium-iron alloy.

For this reason, the present inventors first applied for patent application No. 59-2077.
In No. 3, neodymium-iron alloys, especially neodymium-iron master alloys particularly suitable for manufacturing high-performance permanent magnets, were produced by electrolytic reduction using neodymium fluoride as a raw material using the conventional consumable cathode method. on a large scale and continuously
A technique that can be advantageously manufactured has been clarified.

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. When alloying with the neodymium iron alloy 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. Moreover, a neodymium-iron alloy with a high neodymium content can be effectively produced in one step.

By the way, in the electrolytic production of neodymium-iron alloy by the consumable cathode method using neodymium fluoride as a raw material,
Maintaining the electrolysis temperature in the range of 770 to 950°C is
This is important in obtaining a neodymium-iron master alloy with a low content of impurities and inclusions such as oxygen that adversely affect the magnetic properties of permanent magnets, and further obtaining a neodymium-iron alloy having more stable quality. It is necessary to keep the electrolytic temperature within a narrow range as much as possible. In particular, when increasing the size of the device by using high current, the electrolytic layer is internally heated,
Therefore, it is essential to develop a method for controlling electrolysis temperature.

On the other hand, in the aluminum electrolytic layer in aluminum smelting, the cathode is composed of an aluminum metal pool and is located at the bottom of the tank, while the anode is composed of carbon and is located above the cathode, and the distance between them is By changing the electrodes, the Joule heat generation in the electrolytic bath between the electrodes is adjusted and the electrolysis temperature is controlled. However, the cathode in the electrolytic reduction of neodymium fluoride as described above is a consumable type, and is similar to the anode. It is a type that is immersed from the top of the electrolytic bath, and since there are multiple electrodes in each large tank, it is not easy to control the distance between the electrodes as in aluminum electrolytic baths, and it is not practical. , it is not something that can be adopted at all.

Therefore, when electrolytically producing neodymium-iron alloys using the consumable cathode method using neodymium fluoride as a raw material, it is necessary to establish electrolytic temperature control technology that is effective for operating the electrolytic cell, especially when implementing it on an industrial scale. becomes.

(Summary of the Invention) The present invention has been made against the background of the above, and its purpose is to develop neodymium-iron alloys, particularly suitable for producing high-performance permanent magnets. Another 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, and another 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. The object of the present invention is to provide an effective control method for maintaining the electrolytic temperature in an internal heating electrolytic cell during the electrolytic production of alloys.

That is, in order to achieve the above object, the present invention utilizes an iron cathode and a carbon anode to substantially combine neodymium fluoride and lithium fluoride, as well as barium fluoride and calcium fluoride added as necessary. In electrolytically reducing a neodymium compound in a molten salt electrolytic bath consisting of: depositing the generated neodymium on the iron cathode and alloying it with the iron constituting the cathode to form a neodymium-iron alloy, The immersion depth of the iron cathode in the molten salt electrolytic bath is adjusted to bring the temperature of the molten salt electrolytic bath to 770°C.
The electrolytic reduction operation was allowed to proceed while controlling the temperature within a range of 950°C to 950°C.

However, in such a continuous manufacturing method of neodymium-iron alloy, the immersion depth of the iron cathode is generally adjusted based on the value of the electrolytic sliding voltage, and in order to carry out the present invention, (a) constructed of a refractory material containing a molten salt electrolytic bath consisting essentially of neodymium fluoride and lithium fluoride, with optional additions of barium fluoride and calcium fluoride; an electrolytic cell; (b) a long carbon anode that is inserted into and immersed in the molten salt electrolytic bath of the electrolytic cell and whose shape does not substantially change in the longitudinal direction; and (C) a molten salt electrolytic bath of the electrolytic cell. (d) an elongated iron cathode having substantially no change in shape along its length, inserted and immersed therein; The carbon anode and the iron cathode are placed in a bath, and droplets of neodymium-iron alloy 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 dripped. an alloy receiver for collecting the neodymium-iron alloy droplets; (CI) 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; cathode insertion means for inserting a cathode into the molten salt electrolytic bath of the electrolytic cell; (g) voltage detection means for detecting the voltage between the carbon anode and the iron cathode; and (h) the voltage detection. control means for controlling the temperature of the molten salt electrolytic bath by adjusting the immersion depth of the iron cathode into the molten salt electrolytic bath by the cathode insertion means based on the voltage value detected by the means; of,
An electrolytic device configured to include this will be suitably used.

By following the method of the present invention, the electrolytic sliding voltage is maintained within a desired range, and fluctuations in the electrolytic temperature are reduced, thereby stabilizing the composition of the produced metal and further reducing the impurity content. In addition to the fact that
It has become possible to automate the immersion of the cathode, saving labor and further stabilizing the cathode current density.
It exhibits characteristics such as stable current efficiency and the possibility of reducing and stabilizing the power consumption rate, which makes it possible to use neodymium-iron alloy economically, on a large scale, and continuously. This made it possible to manufacture the product in

In addition, since the system of the present invention is an improvement over the technology of the inventors' earlier application, it goes without saying that it has the same effects.

In other words, the neodymium-iron alloy is produced in one step of electrolytic reduction operation, and contains a low amount of impurities and inclusions such as oxygen that adversely affect the magnetic properties of permanent magnets, and has a high neodymium content. - The advantage is that iron alloys can be effectively produced in one step. Moreover, 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.

Further, according to the present invention, it is possible to easily increase the size of the equipment and make the operation continuous, and furthermore, it is difficult to achieve continuous operation in the electrolytic production method of a fluoride-oxide mixed molten salt using neodymium oxide as a raw material. It is possible to avoid all of these problems, and furthermore, it is possible to achieve high current efficiency over a long period of time, which cannot be achieved by electrolytic production of a chloride mixed molten salt using neodymium chloride as a raw material.

As described above, according to the present invention, a neodymium-iron alloy containing high neodymium and low impurities is suitable as a raw material for high-performance permanent magnets.
This made it possible to produce it economically, on a large scale, and continuously. Such a neodymium-iron alloy is also advantageously used as an intermediate raw material for producing neodymium metal.

(Specific explanation of the configuration) By the way, as mentioned earlier, in large-scale continuous production of neodymium-iron alloy, it is more economical to increase the current capacity of the electrolytic cell, and above a certain scale, The electrolytic cell will be an internal heating type. That is, the electrolysis temperature of the electrolytic bath is maintained by the direct current for electrolysis itself, and in order to maintain a constant electrolysis temperature, the heat retention structure and electrode arrangement of the electrolytic bath must be appropriately designed.

For this reason, the present inventors performed numerical calculations using the finite difference method and determined the potential distribution and temperature distribution within the electrolytic cell, thereby designing the electrode arrangement and the IA structure. From the calculation results, it was found that when electrolytically producing a neodymium-iron alloy by the consumable cathode method using neodymium heptaide as a raw material, due to the structure of the electrolytic cell or the characteristics of the electrolytic operation, ie, the anode.

If the cathode is immersed from above in the electrolytic bath and there is a relatively large difference between the anode current density and cathode current density, and the cathode current density is larger, the electrolytic sliding voltage will vary depending on the cathode immersion depth. It turned out that there was a big change.

The results are shown in FIG. 1 as the relationship between the cathode immersion depth and the sliding voltage, and the actual measured values are also shown there. When the calculated values and the measured data in FIG. 1 are compared, it is understood that they agree well.

On the other hand, in an electrolytic reduction operation using a cathode consumption method using neodymium fluoride as a raw material as in the present invention, the electrolytic sliding voltage changes due to changing the distance between the electrodes as in an aluminum electrolytic tank. It is relatively small compared to the change in the electrolytic cell, and therefore it is an extremely important factor at the electrolytic cell design stage. This is preferable because it has a greater effect.

Then, the method of changing the cathode immersion depth was
Specifically, the simplest method for controlling the bath temperature of the molten salt electrolytic bath in the electrolytic cell is to detect the electrolytic sliding voltage and to interlock this with the cathode lifting device. The basic idea of the control is as follows. That is, as shown in Figure 2, when the cathode is set at a certain immersion depth and electrolysis is started (point A), the voltage between the anode and cathode leads (generally, approximately equal to the electrolytic sliding voltage) ) is vc, this VC increases as shown in the figure as the cathode wears out over time. Therefore, when a certain high voltage: VH (point B) is reached, the cathode is lowered by a certain amount, or the cathode is immersed until a certain set voltage: ■L is reached, or a combination of these methods is used. Voltage: ■o can be effectively reduced. In addition to the above-mentioned method, this VH determination can also be performed using, for example, voltage change over time: ΔV/Δ
It is also possible to adopt a method in which the determination is made based on t. Note that in that case, ΔV/Δt may increase under certain conditions.

In addition, the cathode current density is within a predetermined range, that is, 0.5 to
The number and shape arrangement of cathodes are designed in advance so as to fall within the range of 55 A/cot, and V, and ■.

Good voltage control is possible if the cathode immersion depth is chosen to achieve a voltage between .

It goes without saying that the heat retention structure is designed so that when operating with this controlled voltage (input energy), the heat balance of the entire electrolytic cell can be maintained. Temperature control is achieved such that the electrolytic bath temperature is in the range of 950°C.

Specifically, the above-mentioned VC detection, its control device, etc. are known at the current technical level or industrial level, and are extremely easy to implement. Although not limited to any of them,
An example is shown in FIG. 3. That is, in FIG. 3, the electrolytic cell 10 is composed of a lower tank 12 and a lid 14 that covers the opening of the lower tank 12. Moreover, the outside of these lower tank 12 and lid body 14 is usually
It consists 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 a fireproof insulation material tank 20.22 made of brick, castable alumina, etc. on the outside, and a bath-resistant material layer 24.26 made of graphite, carbonaceous stamp, etc. on the inside. Arranged and configured.

A lining material 28 is provided on the inner bath-contact surface of the inner bath-resistant material layer 24 of the lower tank 12 to cover the bath-contact surface. This lining material 28 is the bath-resistant material layer 24
In addition to preventing the contamination of impurities from the metal, 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 28
It is recommended to use an inexpensive iron material as a material.

This is because, through studies conducted by the present inventors, it was discovered that inexpensive iron exhibits excellent corrosion resistance and is a good lining material for fluoride electrolytic baths. Moreover, the bath-resistant material layer 24 is not necessarily necessary, and the fire-resistant heat insulating material layer 20
There is no problem in applying the lining material 28 directly on top.

Furthermore, the lining material 28 of such an electrolytic cell 10
A solvent constituting the molten salt electrolytic bath 30 is charged into the tank surrounded by . In addition, this solvent is
Neodymium fluoride (NdF3) and lithium fluoride (Li
F) is used, but in addition to these, barium fluoride (BaFz) and calcium fluoride (CaFz) can be used alone or in combination. Among these, when producing neodymium-iron alloys with few impurities and inclusions, the electrolysis temperature is set at 770°C to 950°C.
℃ range, for which purpose such molten salt electrolytic bath 30 is preferably maintained at substantially 35°C.
~76% (by weight, same hereinafter) neodymium fluoride, 2
selected to consist of a mixed molten salt consisting essentially of fluoride, consisting of 0 to 60% lithium fluoride, up to 40% barium fluoride, and up to 20% calcium fluoride, and Even if the raw material neodymium fluoride is added to such an electrolytic bath 30, during electrolysis,
The electrolyte bath will always be adjusted to have such a composition range.

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. are provided, and both electrodes 32, 34
is immersed in an electrolytic bath 30 made of the predetermined molten salt housed in the lower tank 12 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 for them.

Furthermore, these carbon anodes 34. 34 are used in the form of rods, plates, tubes, etc., and they are used in the known manner in order to increase the anode surface area of the part immersed in the electrolytic bath 30 and reduce the anode current density. It is also possible to have grooves.

In addition, in the drawing, the carbon anodes 34, 34 have a slight slope 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, which allows the anode current density to be set to an appropriate anode current density of 0.05 to 0.60 A/cnl for continuous electrolysis. The surface area of the immersion part can be adjusted intermittently or continuously by adjusting the immersion depth so that , preferably 0.10 to 40 A/cni is secured. In addition, the anode lifting mechanism 3
6.36 can also serve as an electrical connection to the anode.

On the other hand, the cathode 32 is made of an iron material to be alloyed with metallic neodymium deposited by electrolytic reduction, one of which is shown here. The immersed portion of the cathode is also 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 770° C. to 950° C., which is below the melting point of the iron of the cathode 40, the iron cathode 32 is solid and linear.

It is used in the form of rods, plates, tubes, etc. This iron cathode 3
2 is also continuously or intermittently fed into the electrolytic bath 30 by a cathode lifting mechanism 38 serving as cathode insertion means, supplementing the bone consumed by alloy formation. In addition, this cathode lifting mechanism 38 here also has the function of electrically connecting to the cathode 32, and also has the function of electrically connecting the iron cathode 32.
Second, there is no problem even if the surface other than the immersed part is protected with a suitable protective sleeve or the like for corrosion prevention.

Note that the cathode lifting mechanism 38 operates under a predetermined electrolytic sliding voltage,
Furthermore, in order to maintain the temperature of the electrolytic bath, it is possible to simply automate a mechanism to feed the iron cathode 32, and for more stable operation, it can be linked with a sliding voltmeter, etc., to intermittently feed the iron cathode 32. It is also possible to automatically insert the iron cathode 32. Here, such a cathode lifting mechanism 38
is composed of a drive motor 40 and a rack and pinion mechanism 42 operated by the drive motor 40, and the rack and pinion mechanism 42 is operated by the drive motor 40.
The cathode 32 is fed into the electrolytic bath 30 by a pinion mechanism. And a cathode 32 and an anode 34
The voltage (electrolytic sliding voltage) between the By inputting the feed amount of the iron cathode 32 from the rotary encoder 48 to the control device 46, these input values and the control device 4
The voltage value (VH.6) is preset to 6.

The drive motor 4o is controlled based on the VL), so that the cathode 32 is lowered intermittently as shown in FIG.

On the other hand, the current density of the cathode is allowed over a wide range of 0.50 to 55 A/cffl over the entire surface of the cathode. However, if the cathode current density is too low, the current per surface area of the cathode 32 will be too small, resulting in poor productivity and not being industrially practical. Furthermore, if this cathode current density becomes too high, the electrolytic voltage will increase significantly and the electrolytic results will deteriorate. In addition, for 8a continuation of actual electrolysis operation, 1.5 to 25A/c++
! It can be said that it is more preferable to maintain the cathode current density within a narrower range of , in order to maintain a narrow variation range of electrolysis voltage and facilitate electrolysis operation.

On the other hand, in the electrolytic bath 30, a produced alloy receiver 50 is arranged on the bottom of the lower tank 12 so that the receiver opening is located below the iron cathode 32, and the cathode 32 and anode 34 are connected to each other. By applying a predetermined DC current during this period, the liquid neodymium-iron alloy 52 produced on the iron cathode 32 by the electrolytic reduction action of the neodymium fluoride raw material in the electrolytic bath 30 is heated to the surface of the cathode 32. The resulting alloy drips and is collected in the produced alloy receiver 50 which opens directly below. The produced alloy receiver 50 is formed using a soft metal having low reactivity with the produced alloy 52, such as tungsten, tantalum, molybdenum, niobium, or an alloy thereof, and may also be formed using a boron such as boron nitride. It can also be formed using ceramics such as compounds or oxides, or materials such as cermet or iron.

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 neodymium fluoride raw material is electrolytically reduced. The metal neodymium deposited on the cathode 32 immediately forms a liquid alloy with the iron constituting the cathode 32, drips from the surface of the cathode 32, and enters the electrolytic cell l.
It will be collected in the receiver 5o installed in the electrolytic bath 30 in o. Note that at the temperature employed during this electrolytic reduction, that is, 770° C. to 950° C., the alloy formed on the iron cathode 32 is in a liquid state, and the alloy formed on the iron cathode 32 is in a liquid state. 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 becomes.

In this way, as the liquid neodymium-iron alloy 52 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 , the immersion length is gradually shortened, the electrolytic sliding voltage is increased, and the electrolytic bath temperature is further increased. Therefore, as described above, under the control of the control device 46, according to the pattern shown in FIG. The cathode 32 is intermittently inserted into the electrolytic bath 30 to allow the electrolytic reduction operation to proceed while maintaining the electrolytic bath temperature within a target temperature range.

Note that the electrolytic raw material consumed by the electrolytic operation in such an electrolytic apparatus is supplied from the raw material supply device 54 to the lid body 14.
The electrolytic bath 30 having a predetermined composition is formed by being supplied through a raw material supply hole 56 provided in the
Further, the produced alloy 52 dripped from the iron cathode 32 and stored in the receiver 50 is collected in a predetermined amount by a predetermined alloy recovery mechanism (retrieving means) while remaining in a liquid state.
For example, a pipe-shaped vacuum suction nozzle 58 is inserted into the electrolytic bath 30 through the produced alloy suction hole 60, and the tip of the nozzle 58 is immersed in the produced alloy 52 in the produced alloy receiver 50. It is sucked up by suction using the vacuum suction effect of the vacuum device, and is taken out of the electrolytic cell 10. Further, inside the electrolytic bath 10, an electrolytic bath 30, a produced alloy 52, an electrode 3
2.34. In order to prevent deterioration of the constituent materials of the electrolytic cell 10 and to avoid mixing harmful impurities and inclusions into the produced alloy 52, a protective gas is preferably introduced. The gas generated by the electrolytic reduction operation is discharged to the outside through the exhaust gas outlet 62 together with the introduced protective gas.

Incidentally, here, the electrolytic cell 10 has a structure in which raw material supply means (54, 56), produced alloy extraction means (58, 60), and protective gas supply means (not shown) are separately provided. However, by making the iron cathode 32 pipe-shaped, the hollow part can be used to supply protective gas or neodymium fluoride, which is the raw material for electrolysis, and to take out the produced alloy. It can be used for holes.

That is, if the protective gas is introduced into the tube interior space under positive pressure from the protective gas supply device 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. , the electrolytic bath 30 enters the tube,
It is possible to effectively prevent a current having a low current density below the target current density from flowing into this portion.

Further, a pipe-shaped iron cathode 3 is supplied from such a protective gas supply device.
2 by increasing the amount of protective gas supplied into the cathode 3.
By blowing a protective gas into the electrolytic bath 30 from the lower end opening of 2, the electrolytic bath 30 can be effectively stirred, and the dissolution of the raw material neodymium fluoride into the electrolytic bath 30 can be promoted. In addition, it can also be used as a protective gas that fills the space above the electrolytic bath 30 in the electrolytic bath IO.

On the other hand, at the same time as the protective gas supplied from the protective gas supply device as described above is blown, neodymium fluoride powder as a raw material is blown into the electrolytic bath 30 through the hollow part of the pipe-shaped iron cathode 32. , it is possible to simultaneously supply the raw material and promote dissolution in the electrolytic bath 30, and there is also an advantage that the need to provide the raw material supply hole 56 in the electrolytic bath 10 (lid 14) is eliminated. Of course, the raw material neodymium fluoride is not only introduced into the electrolytic bath 30 as a powder, but also supplied 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 addition, when taking out a predetermined amount of produced alloy 52 stored in the produced alloy receiver 50 to the outside of the electrolytic cell 10 using the vacuum suction nozzle 58, the inner space of the iron cathode 32 is used as an insertion hole for the nozzle 58 to produce the produced alloy. Used instead of the alloy suction hole 60, the tip of the nozzle 58 is inserted into the produced alloy 52 of the produced alloy receiver 50 in the electrolytic bath 30 through the tubular interior of the iron cathode 32, and the produced alloy 52 is vacuum-suctioned. It is also possible to collect it outside the tank by operation.

However, the extraction of the produced alloy 52 from the produced alloy receiver 50 is as follows:
Although the method of suctioning and taking out the generated alloy 52 by vacuum suction as described above is a preferable means, it is not limited to this, and instead of this, the electrolytic cell 10
(Lower tank 12) is provided with a take-out pipe that penetrates the lower part of the tank,
It is also possible to adopt an alloy recovery mechanism in which the tip of this take-out pipe is further passed through the produced alloy receiver 50 and opened into the receiver 50, thereby flowing out the produced alloy 52 downwardly outside the tank through the take-out pipe. , is possible.

As is clear from the above description, the present invention basically involves controlling the electrolytic bath temperature by adjusting the immersion depth of the iron cathode in the electrolytic bath in internal heating type electrolytic reduction operation. Therefore, there is no need to provide any special heating device to maintain the electrolysis temperature at a predetermined electrolytic temperature, but if necessary, an appropriate heating device may be installed inside or outside the electrolytic cell 10. Even if you set it up, it won't make any difference. However, even in such a case, the heating device serves to supplementally heat the electrolytic bath, and the electrolytic bath temperature is controlled solely by the immersion depth of the iron cathode.

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

Furthermore, 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 as long as they do not depart from the spirit of the present invention,
It should be understood that any of the various embodiments that can be implemented based on the knowledge of those skilled in the art belong to the scope of the present invention.

Example 1 An apparatus having a similar configuration to the electrolytic apparatus shown in FIG. 3 was used. A graphite crucible was used as the bath-resistant material of the electrolytic cell lOO, and a molybdenum container installed at the center of the bottom of the graphite crucible as the produced alloy receiver 50. An electrolytic bath consisting essentially of a ternary fluoride mixed molten salt of neodymium fluoride, lithium fluoride, and barium fluoride (=35 to 59%: 25 to 43%: 14 to 26%) Electrolysis was carried out continuously in an active gas atmosphere. As the cathode 32, three cathodes were placed and immersed in the electrolytic bath at the center of the graphite crucible so as to be located on the same circumference.
An iron wire of 2+nφ was used, and as the anode 34, five graphite rods of 6011φ were arranged concentrically around the cathode and immersed in the electrolytic bath.

The immersion depth of the cathode 32 was controlled as follows. That is, when the voltage value detected by the voltmeter 44 becomes equal to or higher than the set voltage (Vi) preset in the control device 46, the command from the control device 46 causes
The drive motor 40 of the cathode lifting device 38 was activated to move the cathode 32 downward a predetermined amount to increase the depth of cathode immersion into the electrolytic bath 30. The amount of movement of the cathode 32 is determined by detecting the rotation of the drive motor 40 with a rotary encoder 48, and the operation of the motor 40 is stopped when the cathode 32 has moved a certain distance.

Then, using this automatic cathode immersion depth change-sliding voltage control method, under an electrolytic current of 200 A, for 24 hours,
Electrolytic reduction operation of neodymium fluoride was carried out.

As a result of such electrolytic reduction operation, the voltage fluctuation is 7.5
~8.4 V, and the sliding voltage was extremely stable compared to the voltage fluctuation range of 6.8 to 9.2 V in the case where the sliding voltage control method as described above was not adopted.

In addition, the electrolytic bath temperature is also stabilized, and the bath temperature is 2825 to 86 when such a control method is not adopted.
The electrolytic bath temperature could be controlled within a significantly narrow range of 834 to 850°C compared to 3°C.

In this electrolytic reduction operation, the neodymium content in the produced neodymium-iron alloy taken out of the tank every 8 hours was suppressed to 87.0±1.5% by weight and stable. It contained few impurities and was of good quality.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between cathode immersion depth and sliding voltage, and Figure 2 is a graph for explaining changes in the voltage between the anode and cathode (sliding voltage) with the passage of electrolytic reduction time. FIG. 3 is a sectional view showing an example of the structure of an electrolytic cell according to the present invention. 10: Electrolytic tank Engineering 2: Lower tank 14: M body 20.22: Fireproof insulation layer 24.26
: Bath-resistant material layer 28 Lining material 30: Electrolytic bath 32: Iron cathode 34: Carbon anode 36 Two-anode elevating mechanism 38: Cathode elevating mechanism 40: Drive motor 42: Rank and pinion mechanism 44: Voltmeter 46: Control device 4 JP: Rotary encoder 50: Generated alloy receiver 52: Neodymium-iron alloy 54: Raw material supply device 58: Vacuum suction nozzle Applicant
Sumitomo Light Metal Industries Co., Ltd. Yu Gui Immersion Depth 2:00 Darkness (1)

Claims (7)

[Claims] (1) Using an iron cathode and a carbon anode, neodymium compounds are electrolyzed in a molten salt electrolytic bath consisting essentially of neodymium fluoride, lithium fluoride, and barium fluoride and calcium fluoride added as necessary. The immersion depth of the iron cathode in the molten salt electrolytic bath is determined when the neodymium produced by reduction is deposited on the iron cathode and alloyed with the iron constituting the cathode to form a neodymium-iron alloy. to adjust the temperature of the molten salt electrolytic bath to 7.
A method for producing a neodymium-iron alloy, characterized in that the electrolytic reduction operation is allowed to proceed while controlling the temperature to be within a range of 70°C to 950°C. (2) The method for producing a neodymium-iron alloy according to claim 1, wherein the immersion depth of the iron cathode is adjusted based on the value of the electrolytic sliding voltage of the molten salt electrolysis. (3) substantially neodymium fluoride and lithium fluoride;
Additionally, an electrolytic cell made of a fire-resistant material houses a molten salt electrolytic bath consisting of barium fluoride and calcium fluoride added as necessary; a long carbon anode whose shape does not substantially change in the length direction, and a long carbon anode whose shape does not substantially change in the length direction, which is inserted and immersed in the molten salt electrolytic bath of the electrolytic cell; an iron cathode, placed in the molten salt electrolytic bath of the electrolytic cell so that the opening is located below the iron cathode, and a fluorocarbon film formed by direct current applied between the carbon anode and the iron cathode; an alloy receiver for collecting droplets of neodymium-iron alloy formed on the iron cathode by electrolytic reduction of neodymium chloride; and a liquid state of neodymium in the alloy receiver. - liquid alloy removal means for taking out the iron alloy out of the electrolytic cell; cathode insertion means for inserting the iron cathode into the molten salt electrolytic bath of the electrolytic cell; and a voltage between the carbon anode and the iron cathode. a voltage detection means for detecting the voltage value detected by the voltage detection means; and adjusting the immersion depth of the iron cathode into the molten salt electrolysis by the cathode insertion means based on the voltage value detected by the voltage detection means, 1. A neodymium-iron alloy manufacturing apparatus, comprising: control means for controlling the temperature of an electrolytic bath. (4) The manufacturing apparatus according to claim 3, 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. (5) The manufacturing apparatus according to claim 3 or 4, further comprising a raw material supply means for supplying neodymium fluoride as a raw material into the electrolytic cell. (6) The liquid alloy extraction means is configured to suck up the neodymium-iron alloy through a pipe inserted into the liquid neodymium-iron alloy in the alloy receiver and take it out of the electrolytic cell. The manufacturing apparatus according to any one of Items 3 to 5. (7) The manufacturing apparatus according to any one of claims 3 to 6, wherein the carbon anode is a graphite electrode.