JP3628282B2 - Process for producing rare earth alloys with very low oxygen content and fine and homogeneous crystal structure by reduction of rare earth oxides - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, a rare earth oxide raw material or oxidized rare earth alloy waste material is reduced with a reducing agent to form a molten alloy, and the molten alloy is directly quenched and solidified to form a rare earth alloy, particularly a secondary battery negative electrode material or A method for producing a rare earth-based hydrogen storage alloy or a rare-earth magnet alloy having an extremely low oxygen content and a fine and homogeneous crystal structure useful as a storage medium for supplying hydrogenTo the lawRelated.
[0002]
[Prior art]
Conventionally, as an alloy containing a rare earth metal as a main component, a negative electrode alloy or magnet alloy for an alkaline secondary battery made of a combination of a rare earth metal R and a transition metal T is known. These alloys are usually prepared by melting a mother alloy produced using a refined rare earth metal raw material and other refined metal raw materials by high frequency induction heating, and then producing an alloy having a target component composition by die casting. Yes.
[0003]
In addition, as a method of using inexpensive raw materials, a mixture of rare earth oxide raw materials and other alloy component raw materials is reduced with Ca metal or rare earth metal, and a melt of the rare earth metal and other alloy components is die-cast. Methods for producing an alloy having a desired composition by cooling and solidifying are known. For example, Japanese Patent Application Laid-Open Nos. 62-188772, 3-287740, 11-319752, and 11- Japanese Patent No. 329811, Japanese Patent Application Laid-Open No. 2000-109908, and Japanese Patent Application Laid-Open No. 2000-30919 disclose Ca diffusion reduction methods such as R—Fe—B based magnet alloys.
[0004]
However, in the rare earth oxide Ca diffusion reduction method, it is extremely difficult to remove undesirable calcium oxide as inclusions in the obtained metal, as a inclusion, or to remove impurities such as oxygen and carbon. Low oxygen alloy powder cannot be obtained.
[0005]
Therefore, in the Ca diffusion reduction method, it is usually necessary to wash and remove the generated calcium oxide and the like in the process until obtaining the alloy powder. However, rare earth metals are easily oxidized, and oxygen remains as impurities in the alloy. In order to impair the alloy properties, practical application is hindered.
[0006]
Japanese Patent Publication No. 4-35548 uses a Fe crucible that does not cause any problem even when a rare earth metal oxide reacts with a molten alloy in the presence of Fe and B. A method for producing an Fe—B—R intermediate alloy with a low content of inclusions, oxygen, and carbon by reducing Ca is described. In this case, the intermediate alloy is remelted and an additional alloy element is added. Thus, a process for obtaining a desired alloy composition is required.
[0007]
Japanese Examined Patent Publication No. 3-64574 describes a method for producing a master alloy ingot of extremely low oxygen by a reaction of a reducing agent at a temperature of 300 ° C. or lower using a reducing agent. A reducing agent having a special composition is prepared. It takes a long time for the reaction.
[0008]
As described above, it is difficult to obtain an alloy with an extremely low oxygen content of the target component composition by reducing and melting and solidifying a rare earth oxide raw material, and polishing that occurs in the manufacturing process of a rare earth alloy magnet as a melting raw material Scrap such as powder cannot be reused as a melting raw material.
[0009]
For this reason, for rare earth alloy magnet scraps such as abrasive powders, there is a known method for solid-phase reduction with Ca of about 2 to 4 times the stoichiometry and removing calcium oxide by water washing or pickling. (For example, JP-A-56-38438, JP-B-61-53413, JP-A-61-153201).
[0010]
Also, in the rare earth alloy mold casting method, segregation due to non-uniformity of alloy concentration and precipitation of different phases occur due to the difference in cooling rate between the central part and the peripheral part of the mold during the solidification process of the melt. Then, a long-time homogenization heat treatment is required for adjusting the crystal structure in the subsequent process. For example, Sm₂ Fe₁₇And Nd₂ Fe₁₄In the case of obtaining the B compound, impurity phases such as α-Fe phase and Nd rich phase due to peritectic reaction are inevitably generated in the cooling process, and therefore the cast alloy is heated to 1000 ° C. or higher in an inert atmosphere. It was necessary to perform homogenization at high temperature.
[0011]
In order to improve this defect, for example, JP-A-5-327992, JP-A-11-323467, JP-A-8-60265, JP-A-10-280010, JP-A-2000-144277, Japanese Unexamined Patent Publication No. 2000-144278 and Japanese Unexamined Patent Publication No. 2000-160265 propose alloy production by a strip casting method in which a molten alloy is rapidly solidified by a high-speed rotating roll surface or the like. According to this method, since the molten alloy is directly rapidly solidified without using a mold, an alloy having a small crystal structure and a small impurity phase can be obtained.
[0012]
[Problems to be solved by the invention]
In the conventional strip casting method, an expensive metal raw material is prepared so as to have a target alloy component composition, and this is melted by high frequency induction heating melting in a non-oxidizing atmosphere. Further, in the conventional Ca reduction method, a target component having a desired characteristic of a fine and homogeneous crystal structure with a small content of impurities such as oxygen even if strip casting is performed using a molten alloy in which a rare earth oxide raw material is dissolved. It is difficult to produce an alloy of composition.
[0013]
The present invention can be economically produced using an inexpensive rare earth oxide raw material,Also,Reuse of rare earth metal resources, which are expensive and rare resources, by using spent rare earth alloy waste materials that have been problematic in terms of profitability due to the long and costly reprocessing process. Therefore, the purpose of the present invention is to develop a method for producing a rare earth alloy having a target component composition having a desired characteristic of a fine and homogeneous crystal structure with a small content of impurities such as oxygen.
[0014]
[Means for Solving the Problems]
The present inventorOr used rare earth alloy wasteCan be melted in a normal crucible, and the alloy with the desired component composition can be produced with the desired properties of a fine and homogeneous crystal structure with low oxygen content while strip-casting without using other purification means. I found a way I could do it.
[0015]
That is, the present invention(1)A crucible equipped with a heating device and a rapid solidification means for molten alloy are provided in a sealed chamber, and the sealed chamber is in a vacuum or inert gas atmosphere.NozomiEarth oxide powderAnd the restA first step of charging a crucible with a mixture of a raw material powder made of other alloy component powder and a reducing agent made of calcium or calcium hydride powder, the mixture having a calcium melting point (843 ° C.) to 1200 ° C. Calcium reduction reaction by heating to a predetermined temperatureTo form a solid alloyThe second step, followed by a third step of rapidly heating to a predetermined temperature exceeding 1200 ° C. to form a molten alloy and slag, and when the predetermined temperature is reached, the molten alloy is separated from the slag and allowed to flow out of the crucible Or discRapid solidification means comprisingRapid solidification by contacting withFormed alloyThe fourth step,ByWith rapid solidificationOxygen content is 600ppm or lessOf fine and homogeneous crystal structureRare earth hydrogen storage alloy or rare earth magnet with desired alloy compositionA method for producing a rare earth alloy by reduction of a rare earth oxide, characterized by producing an alloy.
[0016]
The present invention also provides:(2) A crucible equipped with a heating device and a rapid solidification means for a molten alloy were provided in a sealed chamber, and the chamber was oxidized in a vacuum or inert gas atmosphere. A first step of charging a crucible with a mixture of raw material powder made of rare earth-based hydrogen storage alloy electrode waste material and a reducing agent made of calcium or calcium hydride powder; the mixture is made at a melting point of calcium (843 ° C.) or higher and 1200 ° C. The second step of forming a solid alloy by a calcium reduction reaction by heating to the following predetermined temperature, then the third step of rapidly heating to a predetermined temperature exceeding 1200 ° C. to form a molten alloy and slag, to the predetermined temperature When it reaches, the fourth step of rapidly solidifying by letting the molten alloy flow out of the crucible while separating from the slag and bringing into contact with the rapid solidification means consisting of a cooling roll or a disk, and the oxygen content is 600 ppm or less in the rapid solidification state. A rare earth-based hydrogen storage alloy with a target alloy composition having a fine and homogeneous crystal structure. Rare earth-based hydrogen storage alloy by reduction of class-based hydrogen storage alloy electrode scrapIt is a manufacturing method.
[0017]
The present invention also provides:(3) A raw material comprising a waste material of oxidized rare earth alloy magnets provided with a crucible equipped with a heating device and a rapid solidification means for a molten alloy in a sealed chamber, and the sealed chamber in a vacuum or inert gas atmosphere. A first step of charging a crucible with a mixture of powder and a reducing agent made of calcium or calcium hydride powder, and heating the mixture to a predetermined temperature not lower than the melting point of calcium (843 ° C.) and not higher than 1200 ° C. The second step of forming a solid alloy by reduction reaction, then the third step of rapidly heating to a predetermined temperature exceeding 1200 ° C. to form a molten alloy and slag, and when the predetermined temperature is reached, the molten alloy is separated from the slag. While the fourth step of rapidly solidifying by bringing it out of the crucible and bringing into contact with the rapid solidification means comprising a cooling roll or a disk, Of the rare earth magnet alloy by reduction of waste of the rare earth alloy magnet, characterized in that while in the oxygen content of the cooling solidification producing a rare earth magnet alloy object the alloy composition of less and fine and homogeneous crystal structure 600ppmIt is a manufacturing method.
[0018]
The present invention also provides:(4) The crucible is tilted to cause the molten alloy to flow out, and the slag is separated from the molten alloy without flowing out by the outflow prevention member provided at the upper part of the crucible. AlloyIt is a manufacturing method.
[0019]
The present invention also provides:(5) A tundish is provided in the sealed chamber, and the molten alloy is allowed to flow out from the crucible to the preheated tundish, and a small amount of slag particles contained in the molten alloy staying in the tundish is separated on the upper surface of the molten alloy, Then, a molten alloy is ejected from a plurality of pores opened in the tundish and brought into contact with a rapid solidification means comprising a cooling roll or a cooling disk to produce a thin plate having a thickness of 0.2 to 3 mm. Of any of the alloys (1) to (3) aboveIt is a manufacturing method.
[0020]
The present invention also provides:(6) In the method of (5), the alloy flakes according to any one of (1) to (3) above, wherein the rapidly solidified alloy is crushed by colliding with a pulverizing plate provided in the sealed chamber. MethodIt is.
[0021]
The present invention also provides (7)A powder having an oxygen content of 600 ppm or less is obtained by pulverizing the alloy flakes produced by the method for producing an alloy flake according to any one of (1) to (3) above to a desired particle size using an impact airflow crusher. In the manufacturing method of the rare earth magnet alloy powder characterizedis there.
[0022]
According to the present invention, rare earth oxide reduction and alloy casting are performed in a sealed chamber in a vacuum or an inert gas atmosphere.A series of consecutiveProduction of rare earth-based hydrogen storage alloys or rare-earth magnet alloys with extremely low oxygen content and good crystallinity, which was difficult with the conventional Ca reduction method, because it can be carried out in a short time in the process and there is no washing step Is possible. Furthermore, since spent alloy electrodes and alloy magnet wastes can be used as raw materials, resources can be reused and economical alloy production can be achieved.
[0023]
Conventionally, when producing an Nd-Fe-B alloy from a metal raw material, first, Nd-Fe and Fe-B master alloy are produced, and then mixed without using each metal having a large difference in melting point. The final Nd-Fe-B alloy is manufactured by melting, but according to the method of the present invention, an alloy having a target alloy composition is used as an oxide raw material.Or used rare earth alloy wasteTherefore, it is possible to save such trouble.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an outline of an alloy production apparatus used in the method for producing a rare earth alloy of the present invention. This manufacturing apparatus includes a rapid solidification apparatus for a molten alloy including a tiltable crucible equipped with a heating device, a cooling roll, or a cooling disk in a sealed chamber that can be in a vacuum or an inert gas atmosphere. The sealed chamber may be evacuated and then have an inert gas flow.
[0025]
In addition, it is preferable to provide a tundish between the crucible and the rapid solidification apparatus in which the molten alloy that has flowed out due to the tilting of the crucible is once introduced and then ejected from the pores provided at the bottom. As a heat source for the crucible, a high frequency induction heating device in which a heating coil is wound around the crucible can be used. The cooling roll or cooling disk of the rapid solidification apparatus is rotated at a high speed. A flake shape in a sealed chamber is provided downstream of the rapid solidification device by providing a pulverizing plate that collides with the alloy formed by rapid solidification.PowderIt is possible to produce a rare earth alloy that has been crushed.
[0026]
The material of the crucible is not limited, and a ceramic crucible can be used, but rare earth metals are extremely reactive and have strong reducing power, so that crucibles such as alumina, silica, magnesia, titania can react and impurities can be mixed And thermodynamically most stable calcia (CaO) and zirconia equivalent thereto are preferable. Tantalum and boron nitride can also be used, but are not practical because they are expensive.
[0027]
In order to melt an alloy by high-frequency induction heating melting, a ceramic crucible is charged with a predetermined amount of oxide and metal components, which are target alloy components, and the oxide also heats as the metal self-heats by induction current. As a result, the reduction reaction in the solid phase and the formation of the molten alloy are performed by increasing the output of the high-frequency induced current. It is easy to dissolve when the amount of metal such as iron or nickel is larger than the amount of oxide, but when the amount of oxide is large or when many powdery waste materials are used, lightly press after mixing the raw materials thoroughly Molded into a pellet to facilitate the flow of induced current. Alternatively, it is also effective to employ a method in which a graphite crucible is disposed on the outer periphery of the ceramic crucible and the raw material is indirectly heated by induction heating of graphite.
[0028]
Hereinafter, the rare earth alloy production method of the present invention is referred to as Nd.₂Fe₁₄The case of producing the B alloy will be described in more detail with reference to the schematic production process diagram of FIG. First, in FIG.(1)In the first step shown by rare earth oxide powderAnd the restA mixture of a raw material powder made of other alloy component powder and a reducing agent made of calcium or calcium hydride powder is charged into the crucible.
[0029]
As the raw material powder, a rare earth oxide powder, a defective product generated in the alloy manufacturing process, or a used rare earth alloy waste material can be used in a predetermined amount after a component composition analysis is performed in advance. Since the battery waste material is considered to be contaminated with trace amounts of potassium, fluorine, carbon, etc., the characteristics of the alloy obtained by mixing with a new oxide raw material is desirable rather than using 100% rare earth alloy waste material as a raw material. In addition to the above, a metal, an alloy, or a carbonyl metal compound that is a constituent of the target alloy may be added as a raw material.
[0030]
The above oxides react with metals at low temperatures, ie more stable metals, at high temperatures, as suggested by the standard free energy / temperature diagrams of various oxides (also referred to as Ellingham diagrams). Can be reduced. As the reducing agent, generally known calcium or calcium hydride powder is used. Since calcium is more active at higher temperatures, it is necessary to suppress reaction with the crucible. Therefore, the calcium input is measured so that it does not become excessive for a given reaction. In addition, it is desirable to load calcium metal in the center portion in order to suppress the reaction with the crucible.
[0031]
The raw material and the reducing agent are mixed or formed into a molded pellet for homogenizing the reduction reaction, and then charged into a crucible and subjected to a heating reaction. Once the crucible is set in the sealed chamber, the raw material is induction-heated by a high-frequency induction heating coil by evacuating the sealed chamber and then switching to an argon gas flow.
[0032]
Next, in FIG.(2)In the second step, the raw material mixture is heated to a predetermined temperature not lower than the melting point of calcium (843 ° C.) and not higher than 1200 ° C. to cause a calcium reduction reaction. In this process, solid Nd is formed by the reaction between the calcium melt and the oxide / metal.₂Fe₁₄B and CaO are produced. In particular, in the method of the present invention, the time required for the third step from the completion of the second step, which is a reduction reaction of the rare earth oxide, at a relatively low temperature to the complete dissolution of the alloy is minimized.
[0033]
That is, in the second step, the calcium reduction reaction is carried out by heating to a predetermined temperature not lower than the melting point (843 ° C.) of calcium and not higher than 1200 ° C. The reduction reaction temperature is appropriately selected depending on the type of raw material, but in the case of rare-earth hydrogen storage alloys and magnet alloys, the reduction reaction temperature is carried out at a temperature near the melting point of calcium. However, if the temperature is too high, the evaporation of calcium to be used for the reduction of the oxide increases, so that it is difficult to complete a sufficient reduction reaction. Accordingly, the temperature is preferably 1200 ° C. or lower.
[0034]
Next, in FIG.(3)As shown in Fig. 3, since a solid alloy is formed after the reduction reaction is completed, the temperature can be easily raised by induction heating. Therefore, in the third step, rapid heating and melting to prevent the crucible erosion to a predetermined temperature exceeding 1200 ° C are performed. Form the alloy completely. The higher the temperature, the lower the viscosity of the molten alloy and the easier the rapid solidification. On the other hand, in order to promote the reaction between the molten alloy and the crucible, the predetermined temperature is preferably 1300-1500 ° C. The heating time to the predetermined temperature is preferably within about 5 minutes, and the output level of the high frequency induction current and the amount of molten alloy in the crucible are determined so that the temperature can be raised in a short time. It is also possible to determine the output level of the high-frequency induction current and the amount of molten alloy in the crucible so that the temperature is raised to 300 ° C. within 1 minute.
[0035]
MmNi₅-Based hydrogen storage alloys and Nd₂Fe₁₄When using a B-based magnet alloy as a raw material, the alloy begins to melt at 1200 ° C to 1300 ° C in the third step, and the calcium oxide, which is a reaction product, melts as slag as shown in the figure because of its low specific gravity. Float on top of alloy. Since a high-quality molten alloy with few impurities can be obtained by this slag generation, it is also effective to promote the generation of slag by adding boric acid in advance.
[0036]
For example, MmNi₅-Based hydrogen storage alloys and Nd₂Fe₁₄In the case of the B-based magnet alloy, the temperature raising process is performed by rapidly heating from room temperature to 900 ° C. in 3 minutes, and holding in the temperature range of 900 to 1100 ° C. for 10 minutes in order to complete the Ca reduction reaction, and thereafter the molten alloy In order to prevent crucible erosion, the temperature of the molten alloy is increased to 1400 ° C. in 2 minutes by rapid heating. At this time, the metal Ca slightly surplus in the reduction reaction is evaporated and discharged together with the argon gas to the outside of the apparatus, while the calcium oxide slag generated by the reaction floats on the upper surface of the molten alloy. For this reason, oxygen and calcium are easily separated from the molten alloy as slag.
[0037]
In the final fourth step, the crucible is tilted to rapidly flow out of the molten alloy that has reached a predetermined temperature, and brought into contact with a rapid solidification means comprising a cooling roll or a disk to rapidly solidify. The slag is separated from the molten alloy without flowing out by an appropriate outflow prevention member provided at the upper part of the crucible. As the rapid solidification device, a device conforming to the Nd-Fe-B rapid cooling flake production device, which has been manufactured for many years at MQI, can be used as it is.thicknessThe amount of molten alloy per hour is increased for the purpose of producing a thin plate of about 0.2 to 3 mm. Therefore, the molten alloy is temporarily received in the tundish, and the molten alloy is cooled at a high speed from a plurality of holes opened in the tundish. It is desirable to eject and solidify on a roll.
[0038]
By pouring the molten alloy into the preheated tundish, a small amount of slag particles contained in the molten alloy staying in the tundish is separated on the upper surface of the molten alloy. Thereafter, the molten alloy is continuously ejected from the fine holes provided at the bottom of one end of the tundish 4 onto the cooling roll 5 that rotates at high speed. The molten alloy solidifies on the cooling roll 5, collides with the steel crushing plate 6, is crushed, and rapidly cools and solidifies the alloy flakes 7 in the container 8. In this case, by cooling the inside of the cooling roll with water and setting the rotation speed to about 0.5 to 10 m / second, an alloy having a desired fine and homogeneous crystal structure can be obtained.
[0039]
This crystal structure is obtained by appropriately controlling the temperature and supply speed of the molten alloy and the rotation speed of the cooling roll. By setting the molten alloy temperature 100 to 200 ° C. above the melting point of the alloy, setting the roll rotation speed to several m / second, and setting the solidification speed to 100 to 2000 ° C./second, several to several tens with few impurity phases. A fine crystal structure of several microns can be obtained. It is also effective to homogenize the obtained alloy flakes at a high temperature for crystal structure adjustment.
[0040]
Thus, according to the present invention, the reaction between the molten alloy and the crucible is avoided by high-temperature heating for a short time after the Ca reduction at a relatively low temperature, and the reaction between Ca and oxide at a high temperature is promoted. It is possible to form a molten alloy with high cleanliness, and to obtain a rare earth alloy having a very low oxygen content and a fine and homogeneous crystal structure by immediately solidifying the molten alloy immediately in an inert atmosphere. Become.
[0041]
Although the alloy produced by the method of the present invention uses an oxide raw material, it undergoes a sufficient reduction reaction at a high temperature and eliminates the water washing step that has been conventionally carried out by the reduction method. Therefore, the oxygen content of impurities contained in the alloy as cast is 600 ppm or less, more preferably 400 ppm or less.
[0042]
The rare earth hydrogen storage alloy targeted in the present invention is LaNi._Five And MmNi_Five Type rare earth alloy. These alloys may contain other transition metals, copper, aluminum, etc. for adjusting various properties such as hydrogen storage capacity, initial activity, and charge / discharge cycle characteristics.
[0043]
The rare earth-based magnet alloy that is the subject of the present invention has R as the rare earth element and R as the transition element.₂ T₁₇, RT₁₂, R₂ T₁₄Sm as a representative example.₂ Fe₁₇N_Three And Nd₂Fe₁₄Magnets made of the B compound are in practical use. As alloy materials, rare earth oxide powder and iron powder, iron alloy powder, boron powder, and other necessary additive components are selected according to the desired alloy.
[0044]
Sm₂ Fe₁₇And Nd₂ Fe₁₄In the case of a B-based alloy, the temperature of the molten alloy is set to 100 to 200 ° C. above the melting point of the alloy, the rotation speed of the cooling roll is set to several m / sec, and the solidification rate is set to 100 to 2000 ° C./sec. As a result, a fine crystal structure of 10 to 80 microns having almost no impurity phase such as α-Fe can be obtained.
[0045]
It is also effective to homogenize the obtained alloy flakes at 1000 to 1200 ° C. in an inert gas for crystal structure adjustment. This alloy flake can be pulverized to a desired particle size and molded in a magnetic field, sintered, machined to produce a sintered magnet, or mixed with an organic resin to produce a bonded magnet.
[0046]
【Example】
Example 1
As a result of separating and recovering a rare earth-nickel-based hydrogen storage alloy negative electrode material from a small secondary battery and performing ICP composition analysis after solvent cleaning, the basic component composition is MmNi_4.6Al_0.27Mo_0.11Alloy. Moreover, the amount of each element mixed measured by the oxygen / nitrogen simultaneous analyzer manufactured by LECO was 3.1% by mass of oxygen and 0.03% by mass of nitrogen.
[0047]
This hydrogen storage alloy waste material was pulverized by an impact airflow pulverizer into which nitrogen gas was introduced to obtain a powder of about 40 to 300 microns. Since most of the oxygen contained in the above-mentioned alloy waste is considered to be an oxide of Mm, calcium having a particle size of about 2 mm as a reducing agent is estimated from the amount of mixing, and the above alloy powder A total of 200 g was weighed in a ratio of 88:12. Next, they were mixed using a blender and solidified by applying a pressure of 50 MPa.
[0048]
As shown in FIG. 1, this mixture is loaded into a calcia crucible 1, set in a sealed chamber equipped with a cooling roll, evacuated in the sealed chamber, then switched to an argon gas flow, and induction by a high frequency induction heating coil 2 Heating was performed. In the temperature raising process, rapid heating is performed from room temperature to 900 ° C. in 3 minutes, and is held at 1050 ° C. for 10 minutes in order to complete the Ca reduction reaction. Thereafter, rapid heating is performed and the molten alloy temperature is increased to 1400 ° C. in 2 minutes. Raised.
[0049]
At this time, the metal Ca slightly surplus in the reduction reaction was evaporated and discharged out of the apparatus together with the argon gas, while the calcium oxide slag 3 produced by the reaction floated on the upper surface of the molten alloy. For this reason, oxygen and calcium were easily separated from the molten alloy as slag.
[0050]
Furthermore, the crucible was tilted and the molten alloy was poured into the preheated tundish, thereby separating a small amount of slag particles contained in the molten alloy retained in the tundish on the upper surface of the molten alloy. Thereafter, the molten alloy was continuously ejected from the fine holes provided at the bottom of one end of the tundish 4 onto the cooling roll 5 rotating at high speed. The molten alloy solidified on the cooling roll 5, collided with the steel crushing plate 6 and crushed, and the rapidly solidified alloy flake 7 having a thickness of 0.2 mm was collected in the container 8.
[0051]
At this time, the estimated cooling speed of the alloy was about 1000 ° C./second by setting the rotational speed of the cooling roll 5 to 5 m / second. Further, the alloy flakes 7 were pulverized in nitrogen gas using an impact airflow pulverizer, and after sieving, a powder of 20 to 40 microns was manufactured.
[0052]
Comparative Example 1
The alloy for comparison was mixed using a blender with the calcium addition amount increased by 20% with respect to the same raw material composition as described above. This mixture was placed in a stainless steel crucible and charged in an electric furnace, and kept at 900 ° C. for 4 hours in an argon gas atmosphere to perform a Ca reduction reaction and cool to room temperature. The reaction product is taken out of the crucible, washed with water, replaced with alcohol, and dried._4.4Co_0.3Al_0.3An alloy powder of composition was produced. The particle size of the obtained powder was in the range of 20 to 40 microns as in Example 1.
[0053]
As a result of performing oxygen analysis of the alloy powder of Example 1 and the comparative example using a nitrogen / oxygen analyzer manufactured by LECO, the former is 230 ppm and the latter is 2840 ppm. The alloy powder obtained in Example 1 has oxygen impurities. It became clear that there was very little.
[0054]
FIG. 3 shows the PCT curves at room temperature of both alloy powders measured by the Siebelz method. It can be seen that Example 1 has a wider and flat hydrogen pressure plateau region than Comparative Example 1, and is excellent as a secondary battery material. The main reasons for this are presumed to be that because there was almost no oxygen contamination, segregation in composition could be prevented and the alloy composition was kept appropriate, and that a fine and homogeneous crystal structure was obtained by rapid solidification.
[0055]
Next, both the above powders were compressed and solidified, and nickel-plated to produce an electrode, and the charge / discharge cycle characteristics of the battery were examined. As is clear from the results of FIG. 4, the battery using the alloy of Example 1 has a markedly lower decrease in discharge capacity due to the increase in the number of charge / discharge cycles than that using the alloy of Comparative Example 1, and the absorption of hydrogen. The progress of pulverization of the alloy accompanying the release was also suppressed.
[0056]
Example 2
The waste material of the rare earth-nickel-based hydrogen storage alloy negative electrode material was separated and recovered from the small secondary battery, and the composition analysis was performed._4.6Al_0.27Mo_0.11O_0.3Met. The powder obtained by pulverizing this hydrogen storage alloy waste material is a 99% pure misch metal oxide powder, a 99.9% pure nickel powder, an aluminum piece, a molybdenum powder, and a 99% pure as a reducing agent. Granular calcium, the composition formula of which is MmNi_4.7Al_0.3 Mo_0.1It measured so that it might become an alloy composition represented by these. These powders were mixed using a blender, and then solidified by applying a pressure of 50 MPa.
[0057]
In the same manner as in Example 1, after reducing Ca, the mixture was melted and rapidly solidified to produce an alloy flake having a thickness of 0.15 mm and further pulverized to obtain a powder of 20 to 40 microns.
[0058]
Comparative Example 2
On the other hand, as a comparative example, misch metal with a purity of 99% and nickel powder, aluminum pieces, and molybdenum powder with a purity of 99.9% were weighed so as to have the same component composition as in Example 2. A mixture of each weighed material was loaded into an alumina crucible, melted by high-frequency induction heating, and rapidly solidified to produce an alloy flake having a thickness of 0.15 mm. Subsequently, a powder of 20 to 40 microns was obtained by grinding. The oxygen contents of the alloy powders of Example 2 and Comparative Example 2 were 250 ppm and 230 ppm, respectively, and an alloy having a significantly low oxygen concentration was obtained.
[0059]
Next, the results of examining the PCT characteristics at room temperature as in Example 1 are shown in FIG. The one using the alloy powder of Example 2 shows almost the same hydrogen pressure plateau characteristics as the one using the alloy powder of Comparative Example 2 using only the metal raw material, and using the alloy waste material or the rare earth oxide as the raw material. It can be seen that it has excellent battery material properties.
[0060]
Example 3
Using a blender, 95 g of 99.9% pure samarium oxide powder, 80 g of 99.9% pure samarium powder, 478 g of 99.9% iron powder, and 47 g of 99% pure granular calcium as a reducing agent were mixed. . This mixture was loaded into a zirconia crucible 1 and set in a sealed chamber equipped with a quenching roll. The inside of the apparatus was evacuated and then switched to an argon gas atmosphere to perform induction heating with the high frequency induction heating coil 2.
[0061]
In the temperature raising process, rapid heating was performed from room temperature, and the temperature was maintained at 1100 ° C. for 10 minutes in order to complete the Ca reduction reaction, and thereafter, further rapid heating was performed to raise the molten alloy temperature to 1550 ° C. At this time, the slag 3 produced by the reaction floats on the upper surface of the molten alloy, tilts the crucible, pours the molten alloy into the preheated tundish, It was continuously ejected onto the cooling roll 5.
[0062]
The molten alloy solidified on the cooling roll 5, collided with the iron crushing plate 6 and crushed, and the rapidly solidified alloy flake 7 having a thickness of 0.6 mm was collected in the container 8. At this time, the estimated cooling rate of the alloy was about 1000 ° C./second by setting the rotational speed of the cooling roll to 2 m / second. This alloy was pulverized using a stamp mill and an impact airflow pulverizer to produce an alloy powder of about 100 microns.
[0063]
The powder is the desired Sm₂ Fe₁₇It became clear from X-ray structural analysis that it has a structure. Moreover, from the compositional analysis result by fluorescent X-rays, the alloy composition was 23.8% Sm-remainder Fe in mass ratio. Furthermore, the oxygen content in the alloy by a nitrogen / oxygen analyzer manufactured by LECO was 410 ppm, and a high-quality magnet alloy having a remarkably low impurity oxygen concentration was obtained.
[0064]
Comparative Example 3
A comparative alloy was produced by the following method. 100 g of samarium oxide powder with a purity of 99.9%, 78 g of samarium with a purity of 99.9%, 480 g of 99.9% iron powder, and 54 g of granular calcium with a purity of 99% as a reducing agent are used as raw materials. And mixed.
[0065]
This mixture was placed in a stainless steel crucible and loaded into an electric furnace, and kept at 950 ° C. for 6 hours in an argon gas atmosphere to perform a Ca reduction reaction and cool to room temperature. The obtained reaction product was taken out from the crucible, washed with water, substituted with alcohol, and dried to produce an alloy powder. From the same analysis results as in Example 3, the alloy composition was 23.9% Sm-0.12% Ca-balance Fe. Furthermore, the oxygen content in the alloy was 1350 ppm, and high concentrations of oxygen and calcium impurities remained.
[0066]
Example 4
202 g of neodymium oxide powder with a purity of 99.9%, 23 g of dysprosium oxide with a purity of 99.9%, 41 g of ferroboron powder with a boron content of 19%, 367 g of iron powder with a 99.9% purity, and a reducing agent As a mixture, 103 g of granular calcium having a purity of 99% was mixed using a blender.
[0067]
This mixture was loaded into a zirconia crucible, set in a sealed chamber, and heated by high frequency induction. In the temperature raising process, rapid heating was performed from room temperature, the temperature was maintained at 1000 ° C. for 30 minutes to complete the Ca reduction reaction, and then increased to 1480 ° C. Subsequently, the crucible was tilted, the molten alloy was poured into the tundish, and continuously jetted onto a cooling roll rotating at high speed.
[0068]
The rotating speed of the cooling roll was 1 m / second, and a rapidly solidified alloy flake having a thickness of 0.8 mm was obtained. This alloy has the desired Nd₂Fe₁₄It was revealed from X-ray structural analysis and microscopic observation that it has a B structure and a crystal structure of 20 to 70 microns. Further, from the result of compositional analysis by fluorescent X-ray, the alloy composition was 27.7% Nd-3.2% Dy-1.09% B-balance Fe in mass ratio. Furthermore, the oxygen content in the alloy by a nitrogen / oxygen analyzer manufactured by LECO was 470 ppm, and a high-quality magnet alloy having a remarkably small impurity oxygen concentration was obtained.
[0069]
Comparative Example 4
As raw materials, 204 g of 99.9% pure neodymium oxide powder, 24 g of 99.9% pure dysprosium oxide, 41 g of ferroboron powder with a boron content of 19%, 367 g of 99.9% iron powder, and reducing agent As a mixture, 108 g of granular calcium having a purity of 99% was mixed using a blender.
[0070]
This mixture was placed in a stainless steel crucible and charged in an electric furnace, and held at 1000 ° C. for 6 hours in an argon gas atmosphere to perform a Ca reduction reaction and cool to room temperature. The obtained reaction product was taken out from the crucible, washed with water, substituted with alcohol, and dried to produce an alloy powder. From the same analysis results as in Example 4, the alloy composition was 27.8% Nd-3.2% Dy-1.1% B-0.11% Ca-balance Fe. Furthermore, the oxygen content in the alloy was 1400 ppm and contained a large amount of impurities such as oxygen and calcium.
[0071]
Example 5
As raw materials, 102 g of 99.9% purity neodymium oxide powder, 11.6 g of 99.9% purity dysprosium oxide, 21 g of ferroboron powder with a boron content of 19%, 184 g of 99.9% iron powder, and As a reducing agent, 51 g of granular calcium having a purity of 99% was weighed.
[0072]
On the other hand, a rare-earth alloy magnet having poor sintering and a component composition of 27.6% Nd-3.0% Dy-1.10% B-0.55% O-0.16% C-balance Fe. 275 g of powder obtained by pulverizing the waste material with a stamp mill was weighed and mixed with the above raw materials using a blender.
[0073]
This mixture was loaded into a zirconia crucible and set in a sealed chamber, heated by high frequency induction, and the alloy was melted after the reduction reaction to raise the temperature of the molten alloy to 1480 ° C. Subsequently, the crucible is tilted, the molten alloy is poured into the tundish, and the molten alloy is continuously ejected onto the cooling roll that is rotating at high speed, and the cooling roll is rotated at a speed of 1 m / second and rapidly solidified with a thickness of 0.8 mm. A flake was obtained.
[0074]
This alloy has the desired Nd₂ Fe₁₄It had a B structure, and its composition was 27.6% Nd-3.0% Dy-1.11% B-0.09% C-balance Fe in mass ratio. Furthermore, the oxygen content in the alloy was 520 ppm, and a high-quality magnet alloy containing a small amount of carbon but having a low impurity oxygen concentration was obtained.
[0075]
Comparative Example 6
As raw materials, neodymium, dysprosium, ferroboron, iron are weighed so as to have a desired composition, high frequency induction heating and melting, and after the temperature of the molten alloy reaches 1480 ° C., the crucible is tilted and the molten alloy is poured into the tundish. The alloy flakes were rapidly solidified with a thickness of 1 mm with the rotation speed of the cooling roll being 1 m / sec. This alloy is Nd₂ Fe₁₄It had a B structure, and its composition was 27.5% Nd-3.0% Dy-1.12% B-balance Fe in mass ratio, and the oxygen content was 490 ppm.
[0076]
Therefore, the alloy obtained by the manufacturing method of the present invention is almost the same as the alloy of the comparative example manufactured using only the refined metal raw material, even though the rare earth oxide or rare earth alloy magnet waste material is used as the raw material. It is a good alloy with an equivalent low oxygen content and is economically advantageous.
[0077]
【The invention's effect】
According to the present invention, the reduction of the oxide and the casting of the alloy can be carried out in the same process in a sealed chamber in a vacuum or an inert atmosphere, and since there is no washing process, it is difficult to perform the casting that has been difficult with the conventional Ca reduction method. An alloy with an extremely low oxygen content and good crystallinity can be produced. Further, an alloy having a finer crystal structure than that of the mold casting method and having the same quality as that obtained by the strip casting method can be manufactured using inexpensive rare earth oxide raw materials and rare earth alloy waste materials.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a production apparatus used in a method for producing a rare earth alloy of the present invention.
FIG. 2 shows Nd produced by the rare earth alloy production method of the present invention.₂Fe₁₄It is explanatory drawing which shows the outline manufacturing process in the case of manufacturing B alloy, and a heating temperature pattern.
FIG. 3 is a graph showing PCT curves of alloy powders of Example 1 and Comparative Example 1.
4 is a graph showing charge / discharge cycle characteristics of batteries using the alloy powders of Example 1 and Comparative Example 1. FIG.
5 is a graph showing PCT curves of alloy powders of Example 2 and Comparative Example 2. FIG.
[Explanation of symbols]
1: crucible
2: High frequency induction heating coil
3: Slag
4: Tundish
5: Cooling roll
6: Crush plate
7: Alloy flake
8: Container

Claims (7)

The rapid solidification means the crucible and the molten alloy with a heating device provided in the enclosed chamber, the enclosed chamber Te state smell was vacuum or inert gas atmosphere, a rare earth oxide powder and the balance of other alloy component powders A first step of charging a crucible with a mixture of a raw material powder made of calcium and a reducing agent made of calcium or calcium hydride powder, and heating the mixture to a predetermined temperature not lower than the melting point of calcium (843 ° C.) and not higher than 1200 ° C. a second step that form a solid alloy by calcium reduction reaction by, then a third step of forming a rapid heating to melt the alloy and slag to a predetermined temperature in excess of 1200 ° C., the solution fusible alloy reaches a predetermined temperature to form a rapidly solidified alloy was by contacting the rapid solidification means comprising a cooling roll or disk by flow out of the crucible while separating the slag Fourth step, the rare earth oxide, characterized in that the oxygen content remains rapid solidification to produce a rare earth-based hydrogen storage alloy or a rare earth magnet alloy object the alloy composition of less and fine and homogeneous crystal structure 600ppm Method for producing rare earth alloy flakes by reduction of materials. A crucible equipped with a heating device and a rapid solidification means for a molten alloy are provided in a sealed chamber, and in a state where the sealed chamber is in a vacuum or an inert gas atmosphere, A first step of charging a crucible with a mixture of calcium or calcium hydride powder and a reducing agent, and heating the mixture to a predetermined temperature not lower than the melting point of calcium (843 ° C.) and not higher than 1200 ° C. A second step of forming a solid alloy and then a third step of rapidly heating to a predetermined temperature exceeding 1200 ° C. to form a molten alloy and slag, and when the predetermined temperature is reached, the crucible is separated from the slag By a fourth step of rapidly solidifying by bringing it out of contact with a rapid solidification means consisting of a cooling roll or disk, A rare earth-based hydrogen storage alloy electrode waste material produced by reduction of a rare earth-based hydrogen storage alloy electrode waste material, characterized by producing a rare earth-based hydrogen storage alloy alloy having a target alloy composition with an oxygen content of 600 ppm or less and a fine and homogeneous crystal structure as it is cold-solidified Method for producing hydrogen storage alloy flakes . A crucible equipped with a heating device and a rapid solidification means of a molten alloy are provided in a sealed chamber, and in a state where the sealed chamber is in a vacuum or an inert gas atmosphere, a raw material powder made of oxidized rare earth alloy magnet waste material, A first step of charging a crucible with a mixture of a reducing agent made of calcium or calcium hydride powder, heating the mixture to a predetermined temperature not lower than the melting point of calcium (843 ° C.) and not higher than 1200 ° C. to cause a calcium reduction reaction. A second step of forming a solid alloy, and then a third step of rapidly heating to a predetermined temperature exceeding 1200 ° C. to form a molten alloy and slag. When the predetermined temperature is reached, the molten alloy is separated from the slag from the crucible. A fourth step of rapid solidification by flowing out and bringing into contact with a rapid solidification means consisting of a cooling roll or a disk; Preparation of a rare earth-based magnet alloy flakes by reducing the oxygen content of the waste of the rare earth alloy magnet, characterized by producing less and rare-earth magnet alloy object the alloy composition of fine and homogeneous crystal structure 600ppm remain Method. 4. The alloy flakes according to claim 1, wherein the crucible is tilted to cause the molten alloy to flow out, and the slag is separated from the molten alloy without flowing out by the outflow prevention member provided at the upper part of the crucible . Production method. A tundish is provided in the sealed chamber, and the molten alloy is allowed to flow out from the crucible to the preheated tundish, and a small amount of slag particles contained in the molten alloy staying in the tundish is separated on the upper surface of the molten alloy. A molten alloy is ejected from a plurality of pores opened in a tundish and brought into contact with a rapid solidification means comprising a cooling roll or a cooling disk to rapidly cool and solidify to produce a 0.2 to 3 mm thin plate. method for producing alloy flakes according to any one to claims 1 to 3. 6. The method according to claim 5, wherein the rapidly solidified alloy is crushed by colliding with a pulverizing plate provided in the sealed chamber to form an alloy flake. Production method. It manufactured with the manufacturing method of the alloy flakes in any one of Claim 1 thru | or 3. A method for producing a rare earth magnet alloy powder, characterized in that a powder having an oxygen content of 600 ppm or less is obtained by crushing an alloy flake to a desired particle size with an impact airflow crusher.

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