Patent Application
20100202917
The present invention relates to an apparatus for producing an alloy. In particular, the present invention relates to an apparatus for producing a R-T-B-based rare-element containing alloy (R is at least one element of the rare-earth elements containing Y, T is metal which contains essentially Fe, and B is boron).
Priority is claimed on Japanese Patent Application, No. 2007-247851, filed on Sep. 25, 2007, the contents of which are incorporated herein by reference in their entirety.
R-T-B-based magnets, which have the maximum magnetic energy product in permanent magnets, are used for HD (hard disks), MRI (magnetic resonance imaging methods), various motors, etc. because they have high characteristics. In recent years, since saving energy has been increasingly demanded, in addition to an improvement of heat resistance of the R-T-B-based magnets, the use of R-T-B magnets as motors including a motor for vehicles has increased.
Since the main components of the R-T-B-based magnets are Nd, Fe, and B, the R-T-B magnets are also collectively called Nd—Fe—B magnets.
In the R-T-B magnets, R means Nd, a part of which is replaced with at least one rare-earth element, such as Pr, Dy, and Tb, in particular, often Nd, a part of which is replaced with at least one of rare-earth elements including Y. T means an alloy of Fe as an essential component, and Co, Ni, etc. B is boron, and may be partially substituted with C or N.
Other elements such as Cu, Al, Ti, V, Cr, Ga, Mn, Nb, Ta, Mo, W, Ca, Sn, Zr, and Hf may be added to the R-T-B-based alloys, singly or in combination of two or more species.
R-T-B-based alloys, which are R-T-B magnets, contain a ferromagnetic phase, R2T14B crystals, which contribute to magnetization, as the main phase, and a nonmagnetic R-rich phase having a low melting point and containing a non-magnetic rare-earth element at high concentration.
Since the R-T-B-based alloy is an active metallic material, the alloy is generally melted and cast in a vacuum or under an inert gas. When a sintered magnet is obtained from casting a R-T-B-based alloy ingot by a powder metallurgy method, in general, an alloy ingot is crushed to obtain alloy powder having a particle size of about 3 μm (as measured by means of FSSS (Fisher Sub-Sieve Sizer)), the powder is subjected to pressing in a magnetic field, the obtained compact is sintered in a sintering furnace at about 1,000 to 1,100° C., the sintered product is heated, mechanically processed, and plated for corrosion prevention, and a sintered magnet is obtained.
The R-rich phase plays the following important roles in the R-T-B-based sintered magnet.
(1) Since the R-rich phase has a low melting point, the phase liquefies during sintering, thereby contributing to achievement of high remanence, leading to improved magnetization.
(2) The R-rich phase functions to smoothen grain boundaries, thereby reducing the number of nucleation sites of reversed magnetic domains, thereby enhancing the coercive force.
(3) The R-rich phase magnetically insulates the main phase, thereby enhancing the coercive force.
When the distribution of the R-rich phase in a cast magnet is inferior, sintering may be partially defective, and magnetic properties may be decreased. Therefore, it is important to disperse uniformly the R-rich phase into the cast magnet. The distribution of the R-rich phase depends greatly on the microstructure of raw material, an R-T-B-based alloy.
Another problem involved in casting of the R-T-B-based alloy is that α-Fe is formed in the cast alloy. The α-Fe has deformability, and remains in a crusher, without being crushed. Due to this, α-Fe not only deteriorates crushing efficiency during the crushing of the alloy, but also changes the composition before and after crushing, and greatly affects the particle distribution. In addition, if α-Fe remains even after sintering, magnetic characteristics of the sintered product are deteriorated.
In order to solve the above problems caused by formation of α-Fe in the R-T-B-based alloy, a strip casting method (abbreviated as SC method), in which an alloy ingot is cast with a higher cooling rate has been developed, and employed in actual production steps.
In the SC method, an alloy is rapidly solidified by pouring a molten alloy onto a rotating copper roller, the inside of which is cooled by water, to cast a strip having a thickness of about 0.1 to about 1 mm. During casting, the molten alloy is supercooled to the formation temperature of R2T14B or less, which is the main phase. Therefore, it is possible to form directly R2T14B from the molten alloy. Due to this, it is possible to prevent the formation of α-Fe.
In addition, since the crystalline structure of the alloy is minutely dispersed, it is possible to form an alloy having a structure in which an R-rich phase is finely dispersed. The R-rich phase reacts with hydrogen in a hydrogen atmosphere, expands, and forms brittle hydride (hydrogen decrepitation step). It is possible to generate fine cracks using the R-rich phase. When an alloy is finely crushed after the hydrogen decrepitation step, since the alloy is broken due to a lot of fine cracks, which are formed by the hydrogenation, crushability of the alloy is excellent.
As explained above, since the R-rich phase is minutely dispersed in the alloy ingot produced through the SC method, dispersion of R-rich phase in the product obtained by crushing and sintering the alloy also becomes satisfactory. Thereby, it is possible to improve magnetic properties of the obtained magnet (For example, Patent Document No. 1)
In addition, the alloy flakes, which are cast by the SC method, have superior uniformity of microstructure. The uniformity in microstructure can be evaluated based on a crystal grain size and the dispersion state of the R-rich phase. In alloy flakes formed by the SC method, chill crystals sometimes generate on a side which contacts with a cast roller (abbreviated as “cast surface side” below). Therefore, it is possible to obtain a reasonably fine and uniform microstructure by rapid solidification.
As explained above, the R-T-B-based alloy obtained by the SC method has a finely dispersed R-rich phase, and the formation of α-Fe is also prevented. Therefore, when a sintered magnet is obtained, uniformity of the R-rich phase in the final magnet product is improved, and crushing and adverse effects due to α-Fe can be prevented. In this way, the R-T-B-based alloy ingot obtained by the SC method has superior microstructure for producing sintered magnets.
Patent Document No. 1: Japanese Unexamined Patent Application, First Publication No. H5-222488
It has been required that the R-T-B-based alloys obtained by the SC method are further improved.
As explained above, the R-T-B-based alloy contains mainly R, T, and B (boron), where R denotes Nd, a part of which is replaced with at least one of rare-earth elements including Y. T means an alloy containing Fe as an essential component, and Co, Ni, etc.
In general, heat resistance of the R-T-B-based alloy is determined depending on coercive force. As the compositional ratio of Dy and Tb in the R-T-B-based alloys becomes higher, coercive force also increases. However, when Dy or Tb is added in alloys, coercive force increases, but remanence tends to be decreased. Therefore, it is difficult to satisfy demands by customers by only increasing the compositional ratio of Dy and Tb.
In consideration of the above-described problems, it is an object of the present invention to provide an apparatus for producing an alloy containing a rare-earth element, which can produce a rare-earth magnet having high coercive force, and decrease Br (remanence) due to addition of Dy and Tb minimum.
In order to achieve the object, the present invention provides the following inventions.
[1] An apparatus for producing an alloy, wherein the device includes at least a casting device for casting a molten alloy by the SC method, a crushing device for crushing a cast alloy after casting, a heat-retaining device for maintaining the temperature of cast alloy flakes supplied from the crushing device, and a storage container for storing the cast alloy flakes after maintaining the temperature, the heat-retaining device including a heat-retaining container for storing the cast alloy flakes supplied from the crushing device, a heater for maintaining the temperature of the cast alloy flakes in the heat-retaining container, and an inclination device for inclining the heat-retaining container and sending the cast alloy flakes in the heat-retaining container to the storage container.
[2] The apparatus for producing an alloy according to [1], wherein the inclination device sends the cast alloy flakes to the storage container after a specific period of heat-retaining time since the cast alloy flakes are stored in the heat-retaining container.
[3] The apparatus for producing an alloy according to [1] or [2], wherein the heater is arranged on a wall and/or a bottom of the heat-retaining container.
[4] The apparatus for producing an alloy according to any one of [1] to [3], wherein the heater is arranged above the heat-retaining container.
[5] The apparatus for producing an alloy according to any one of [1] to [4], wherein the heater is arrange below the heat-retaining container.
[6] The apparatus for producing an alloy according to any one of [1] to [5], wherein the inclination device includes at least a pair of conveyor rollers, an endless conveyor belt which drives so as to rotate between a pair of the conveyor rollers, and a fixing member for fixing slidably the heat-retaining container on a conveyor surface of the endless conveyor belt, the heat-retaining container being inclined when a moving direction of the endless conveyor belt is reversed by either conveyor roller of a pair of the conveyor rollers.
[7] The apparatus for producing an alloy according to [6], wherein a plurality of the heat-retaining containers is fixed to the endless conveyor belt.
[8] The apparatus for producing an alloy according to any one of [1] to [5], wherein the inclination device includes a rotation shaft provided to the heat-retaining container, and a movable device for inclining the heat-retaining container by inclining the rotation shaft.
[9] The apparatus for producing an alloy according to [8], wherein the heat-retaining container has an inlet hole for the cast alloy flakes at the upper part, and an openable outlet portion for the cast alloy flakes at the side part.
[10] The apparatus for producing an alloy according to any one of [1] to [9], wherein the casting device, the crushing device, and the heat-retaining device are arranged inside of a chamber in an inert gas atmosphere.
[11] The apparatus for producing an alloy according to [10], wherein a cooling chamber is provided in the chamber, and the storage container is stored so as to be able to move to the cooling chamber.
[12] The apparatus for producing an alloy according to any one of [1] to [11], wherein the alloy is a rare-earth element containing alloy.
[13] The apparatus for producing an alloy according to [12], wherein the rare-earth element containing alloy is an R-T-B-based alloy (wherein R is at least one element selected from the group consisting of rare-earth elements including Y, T is an alloy containing Fe as an essential component, and B is boron).
[14] The apparatus for producing an alloy according to any one of [1] to [11], wherein the alloy is a hydrogen storage alloy.
[15] The apparatus for producing an alloy according to any one of [1] to [11], wherein the alloy is a thermoelectric semiconductor alloy.
[16] An alloy produced by the apparatus for producing an alloy according to any one of [1] to [11].
[17] A rare-earth element containing alloy produced by the apparatus for producing an alloy according to any one of [1] to [11].
[18] A hydrogen storage alloy produced by the apparatus for producing an alloy according to any one of [1] to [11].
[19] A thermoelectric semiconductor alloy produced by the apparatus for producing an alloy according to any one of [1] to [11].
[20] A rare-earth magnet made of the rare-earth element containing alloy according to [17].
The apparatus for producing an alloy according to the present invention includes a heat-retaining container for storing the cast alloy flakes supplied from the crushing device, a temperature retaining heater for maintaining the temperature of the cast alloy flakes in the heat-retaining container, and an inclination device for sending the cast alloy flakes in the heat-retaining container to the storage container by inclining the heat-retaining container. Therefore, it is possible to improve various properties of the obtained alloy by retaining the temperature of the cast alloy flakes after crushing.
In particular, when the alloy is the R-T-B-based alloy, the coercive force can be improved by retaining the temperature. Therefore, it is possible to produce a rare-earth element magnet having high coercive force without increasing the compositional ratio of Dy and Tb in the R-T-B-based alloy.
Below, the apparatus for producing an alloy of the present invention is explained in detail referring to figures. Moreover, figures, which are referred to in the following explanations, are for explaining the structure of the apparatus for producing an alloy, and a size, a thickness, etc. of each part illustrated may differ from the real size, thickness, etc. in the apparatus for producing an alloy.
[Total Structure of the Production Apparatus for an Alloy]
The production apparatus 1 for an alloy (abbreviated as “production apparatus” below) shown in
The production apparatus 1 shown in
In the heat-retaining and storing chamber 6b, the container 5 is arranged below the heat-retaining device 3. The container 5 is made of various metals, which can be used under high temperatures, such as stainless, iron, HASTELLOY®, and INCONEL°. The production apparatus 1 is provided with a belt conveyor 51 (movable device), which moves the container 5. The container 5 can move in the horizontal direction in
In addition, the heat-retaining and storing chamber 6b has a gate 6e. The heat-retaining and storing chamber 6b is hermetically closed by the gate 6e except when the container 5 is transferred outside the heat-retaining and storing chamber 6b.
Moreover, a cooling chamber may be provided to the heat-retaining and storing chamber 6b on the opposite side of the gate 6e. Furthermore, it possible to provide another gate in the cooling chamber to transfer the container 5 to the outside of the chamber 6.
[Structure of the Casting Device]
The molten alloy L is produced in a high frequency melting furnace (not shown in Figures) which is outside of the chamber 6. In the high frequency melting furnace, a molten metal is prepared by putting raw materials into a refractory crucible 24 under a vacuum or an inert gas atmosphere, and making molten the raw materials by a high frequency melting process. Although the temperature of the molten metal L varies depending on the composition of the alloy, it is adjusted to a range of from 1300° C. to 1500° C. The prepared molten metal L is transferred to the casting device 2, together with the refractory crucible 24. Then, the molten alloy L is supplied from the refractory crucible 24 into the tundish 23.
The tundish 23 has a rectifier device or a slag removal device, if necessary.
The cooling roller 22 has a water cooling device, which is not shown in figures, inside thereof. The circumference 22a of the cooling roller 22 is cooled by the water cooling device. The material constituting the cooling roller 22 is preferably copper or a copper alloy, because it has high thermal conductivity and is easily obtainable. The supply rate of the molten alloy L and the revolution speed of the cooling roller 22 are controlled according to the thickness of the casting alloy M. The surface speed of the cooling roller 22 is preferably in a range of from 0.5 to 3 m/s of the rotating speed, since an alloy easily adheres to the peripheral surface 22a of the cooling roller 22, depending on the construction material of the cooling roller 22, or the surface state of the peripheral surface 22a. Therefore, when a cleaning device is installed depending on necessity, the quality of the cast R-T-B-based alloy is stabilized. The cast alloy M solidified on the cooling roller 22 falls off the cooling roller 22 on the opposite side of the tundish 23.
As shown in
[Structure of the Heat-Retaining Device]
As shown in
The heat-retaining container 32 stores the cast alloy flakes N which have fallen from the crushing device 21. The heat-retaining container 32 is made of a material having high thermal insulation properties, for example, a ceramic block, such as alumina block and zirconia block, a fibrous plate, or a complex material in which plural metal thin plates are deposited with a gap.
After the temperature is maintained for a fixed period of time since the cast alloy flakes N are stored in the heat-retaining container 32, the belt conveyor 33 makes the heat-retaining container 32 incline to send out the cast alloy flakes N in the heat-retaining container 32 into the container 5.
The belt conveyor 33 has plural conveyor rollers 34 which extend in a substantially horizontal direction, an endless ring-shaped conveyor belt 35 which is installed on the periphery of the plural conveyor rollers 34, and a fixing member 36 for fixing the heat-retaining container 32 on the conveyor surface of the endless conveyor belt 35 so as to swing.
The plural conveyor rollers 34 include a pair of end rollers 34a and 34a which are arranged on both sides, and intermediate rollers 34b which are arranged between the end rollers 34a and 34a.
The belt conveyor 33 makes the heat-retaining container 32 incline while the transfer direction of the endless conveyor belt 35 is reversed by one end roller 34a.
The heat-retaining container 32 is fixed on the exterior surface of the endless conveyor belt 35 such that the opening portion 32 faces outwardly. The heat-retaining container 32 circles on the outside of the endless conveyor belt 35, while the opening portion 32 faces outwardly, by rotating the conveyor rollers 34.
Specifically, the cast alloy flakes N are supplied from the crushing device 21 to the heat-retaining container 32 having the open portion 32 facing outwardly during moving. Then, when the heat-retaining container 32 is made to incline at the end portion 33a of the belt conveyor 33 in the transfer direction, the cast alloy flakes N in the heat-retaining container 32 are sent to the container 5.
In addition, it is possible to control the time after storing the cast alloy flakes N in the heat-retaining container 32 before sending them to the container 5 by adjusting the moving speed of the heat-retaining container 32.
The temperature retaining heater in the heat-retaining device 3 shown in
The lower heater 31b is arranged below the heat-retaining container 32. The lower heater 31b heats the moving heat-retaining container 32 while the opening portion 32a faces downwardly, from the bottom.
In addition, a flake injection hole 31c for supplying the cast alloy flakes N from the crushing device 21 to the heat-retaining container 32 is formed in a part of the upper heater 31a. As shown in
The heating manner of the upper and lower heaters 31a and 31b is not particularly limited. For example, resistance heating, infrared-ray heating, and induction heating are used.
In addition, since a heating element in the upper and lower heaters 31a and 31b may be a metal wire, silicon carbide, black lead, etc. can be used.
[Operation of the Production Apparatus]
Next, operation of the production apparatus 1 is explained.
As shown in
In addition, the heat-retaining container is rotated by operating the belt conveyor 33. The temperature of the heat-retaining container is raised to a fixed temperature by switching on the upper and lower heaters 31a and 31b.
Then, the cast alloy flakes N are produced by operating the crushing device 21. In order to prepare the cast alloy flakes N, a molten alloy L is prepared using a melting device not shown in figures. Then, as shown in
For example, the molten metal L has a composition expressed by a general formula, R-T-B. In the general formula, R denotes at least one of rare-earth elements including Y. T means Fe which is partially replaced with a metal, such as Co, and Ni. B is boron, or boron which is partially replaced with C or N. In addition, other elements such as Cu, Al, Ti, V, Cr, Ga Mn, Nb, Ta, Mo, W, Ca, Sn, Zr, and Hf may be added, to the R-T-B-based alloys, singly or in combination of two or more species.
The composition ratio of R is 28 to 33% by mass, B is 0.9 to 1.3% by mass, and T is the remainder. It is possible that a part of R be replaced with 15% by mass of Dy and/or 15% by mass of Tb.
The composition of the molten metal L used in the production apparatus 1 is not limited to the above ranges. Any composition can be used as long as it is a R-T-B-based alloy.
It is preferable that the average cooling rate of the molten alloy on the cooling roller be adjusted to a range of from 300 to 3000° C. per second. When it is 300° C. per second or more, the cooling rate is sufficient, and the precipitation of α-Fe, and coarsening of the R2T17 phase can be more reliably prevented. In contrast, when it is less than 3,000° C. per second, supercooling is not excessive, and it is possible to supply the cast alloy flakes to the heat-retaining device 3 maintaining more adequate temperatures. In addition, the cast alloy flakes are not cooled more than necessary. Therefore, reheating of the cast alloy flakes is not necessary.
Moreover, an average cooling rate is calculated by dividing the temperature difference of the molten alloy between just before contacting the cooling roller 22 and when removing from the cooling roller 22 by the period of time during contacting with the cooling roller 22.
In addition, the average temperature of the cast alloy M when removing from the cooling roller 22 varies depending on slight variation of contacting conditions between the cast alloy M and the cooling roller 22, or the thickness of the cast alloy M. The average temperature of the cast alloy M when removing from the cooling roller 22 is obtained by averaging the measurement values obtained by measuring the surface of the alloy in the width direction throughout the casting using a radiation thermometer.
It is preferable that the average temperature of the cast alloy M when removing from the cooling roller 22 be a temperature which is 100° C. to 500° C. less than the solidification temperature of the molten alloy when the R2T14B phase is in equilibrium, and a temperature which is 100° C. to 400° C. less than the solidification temperature is more preferable. When the R2T14B phase is made of Nd—Fe—B, the melting point is 1,150° C. This melting point varies by replacing Nd with another rare-earth element, Fe with another transition element, or kind and amount of another additive element added.
When the difference between the average temperature of the cast alloy M when removing from the cooling roller 22 and the solidification temperature of the cast alloy M when the R2T14B phase is in equilibrium is less than 100° C., the cooling rate is insufficient. In contrast, when the difference is 500° C. or more, the cooling rate is too fast. When the molten alloy is supercooled, the conditions of the alloy are not uniform within the alloy, and vary depending on the contact degree between the molten alloy L and the cooling roller 22, or the distance from the contacting portion on the cooling roller 22.
Next, as shown in
In the production apparatus 1 shown in
Next, each heat-retaining container 32 is explained.
The temperature of the empty heat-retaining container 32, of which the opening portion 32a faces upwardly, is maintained at predetermined temperatures by heating with the upper heater 31a while moving from the left-hand side to right-hand side in
After that, the heat-retaining container 32 containing the cast alloy flakes N moves further from the left-hand side to right-hand side in
Moreover, the period of time after the cast alloy flakes N are stored in the heat-retaining container 32 before the cast alloy flakes N are sent to the container 5 is adjusted by controlling the moving speed of the heat-retaining container 32 by the belt conveyor 33 in the heat-retaining device 3 shown in
Then, the temperature of the empty heat-retaining container 32 of which the opening portion 32a faces downwardly is maintained at specific temperatures by heating with the lower heater 31b while moving from the right-hand side to left-hand side in
In this embodiment, it is preferable that the temperature of the heat-retaining container 32, that is, the maintaining temperature of the cast alloy flakes, be less than the temperature of the cast alloy flakes N when moving from the cooling roller 22 (abbreviated as “cooling roller removing temperature” below). Specifically, the temperature is preferably in a range of from (cooling roller removing temperature −100° C.) to the cooling roller removing temperature, and more preferably in a range of from (cooling roller removing temperature −50° C.) to the cooling roller removing temperature. More specifically, it is preferably in a range of from 600° C. to 900° C.
When the temperature of the cast alloy flakes N is maintained in the range, it is possible to improve the coercive force of the R-T-B-based alloy. When the maintaining temperature is 600° C. or more, the coercive force can be further improved. In contrast, when it is less than 900° C., it is possible to prevent more reliably the formation of α-Fe, and coarsening of the R2T17 phase.
Moreover, when the temperature of the cast alloy flakes N is maintained at 1,000° C. or more, the coercive force is also improved. However, when the cast alloy flakes N are maintained at 1,000° C., the microstructure becomes coarse. Therefore, the grain size distribution, fluidity, and sintering temperature after crushation vary. Due to this, it is necessary to consider the effects after maintaining the temperature in a case of maintaining the cast alloy flakes N at 1,000° C.
When the cooling roll removing temperature falls for a any reason, it is possible to raise and maintain the temperature of the cast alloy flakes N by controlling the upper heater 31a and/or the lower heater 31b, and making the maintaining temperature higher than the cooling roller removing temperature. Thereby, the temperature of the cast alloy flakes N can be raised and maintained. In this case, the raising temperature range is preferably 100° C. or less, and more preferably 50° C. or less. When the raising temperature range is larger than 100° C., productivity may be decreased.
The heat-retaining time of the cast alloy flakes N is preferably 30 seconds or more, more preferably in a range of from 30 seconds to several hours, and most preferably in a range of from 30 seconds to 2 minutes. When the heat-retaining time is 30 seconds or more, the coercive force can be further improved. It is possible to maintain for several hours. However, in terms of the productivity, 2 minutes or less is preferable.
There is a heat-retaining time lag between the cast alloy flake N which is supplied at first and the cast alloy flake N which is supplied at the end. In this embodiment, it is preferable that the heat-retaining time of the cast alloy flake N which is supplied at first and the heat-retaining time of the cast alloy flake N which is supplied at the end is also adjusted in that range.
The cast alloy flakes N, which are sent to the container 5 after maintaining the temperature thereof by the heat-retaining device 3, are collected in the container 5 uniformly in the horizontal direction, because the container 5 moves in the horizontal direction in
The cast alloy flakes N collected in the container 5 are cooled by contacting the inner wall of the container 5. The cast alloy flakes N in the container 5 are transferred outside of the chamber 6 by opening the gate 6e of the heat-retaining and storing chamber 6b, and transferring the container 5 to the outside of the chamber 6.
When the cooling chamber is formed in the chamber 6, the cast alloy flakes N in the container 5 are cooled by opening the gate 6e of the heat-retaining and storing chamber 6b, and transferring the container 5 to the cooling chamber. Then, after cooling the cast alloy flakes N, the gate of the cooling chamber is opened, and the container 5 is transferred outside of the chamber 6.
As explained above, the production apparatus shown in
In addition, according to the production apparatus 1 shown in
In addition, the belt conveyor 33 in the production apparatus shown in
In addition, the heat-retaining container 32 rotates by the belt conveyor 33 in the heat-retaining device 3 shown in
In addition, the heat-retaining device 3 has the upper heater 31a for heating the heat-retaining container 32 having the open portion 32 facing upwardly while moving. The flake injection hole 31 is formed at a part of the upper heater 31a. The flake injection hole 31 is below the crushing device 21. Due to this, the cast alloy flakes N can be supplied from the crushing device 21 into the heat-retaining container 32 having the opening portion 32a facing upwardly while moving. At the same time, the heat-retaining container 32 having the opening portion 32a facing upwardly can be heated from the upper portion.
In addition, since the heat-retaining device 3 is arranged below the crushing device 21, the cast alloy flakes N can be supplied from the crushing device to the heat-retaining device 3 by only making the cast alloy flakes N fall. Therefore, it is not necessary to use a transfer mechanism for transferring the cast alloy flakes N from the crushing device 21 to the heat-retaining device 3. The size of the production apparatus 1 can be reduced, and space for the production apparatus 1 can also be reduced.
In addition, the heat-retaining device 3 has the lower heater 32b for heating the heat-retaining container 32 having the opening portion 32a facing downwardly from the lower portion. The heat-retaining container 32 having the opening portion 32a facing downwardly can be heated at specific temperatures. Thereby, the temperature of the heat-retaining container 32 when the cast alloy flakes N are supplied to the heat-retaining container 32 can be easily adjusted to the specific temperature range.
Since it has the belt conveyor 51 which makes the container 5 move, the cast alloy flakes N after maintaining the temperature can be collected uniformly in the container 5 by moving the container 5 with the belt conveyor 51. Thereby, it is possible to obtain the cast alloy flakes N having uniform quality. In addition, it has the belt conveyor 51 which makes the container 5 move freely, the cast alloy flakes N after maintaining the temperature can be easily transferred out of the production apparatus 1.
In addition, since the casting device 2 has the crushing device 21, the cast alloy ingot is promptly crushed to make the cast alloy flakes N. Thereby, the cast alloy can be easily handled in the container 5 and the heat-retaining device 3.
In addition, since the casting device 2 and heat-retaining device 3 are arranged in the chamber 6 in an inert gas atmosphere, deterioration of R-T-B-based alloy can be prevented.
When the cooling chamber is in the chamber 6, since the container 5 can move into the cooling chamber, it is possible to transfer the cast alloy flakes N after maintaining the temperature together with the container 5 out of the heat-retaining and storing chamber 6b to cool them. Thereby, it is possible to improve the productivity.
In addition, when the rare-earth element containing alloy is the R-T-B-based alloy, it is possible to produce magnets having high coercive force and heat resistance using the production apparatus 1. The coercive force of the R-T-B-based alloy containing the rare-earth element containing alloy increases, when the compositional ratio of Dy and increases. However, the remanence tends to decrease.
Since the production apparatus 1 has the heat-retaining device 3, the temperature of the R-T-B-based alloy can be maintained. Thereby, the coercive force of the magnet containing the R-T-B-based alloy can also be improved. Therefore, it is possible to decrease the compositional ratio of Dy and Tb. In addition, the remanence can be also improved by decreasing the compositional ratio of Dy and Tb.
Moreover, the heat-retaining device 3 is not limited to this embodiment. For example, when the heat-retaining device 3 has the upper and lower heaters 31a and 31b shown in
In addition, for example, it is also possible for a heater to be fixed on the side wall and/or the bottom of the heat-retaining container 32, instead of or in addition to the upper and lower heaters 31a and 31b. In this case, it is possible to exactly control the maintaining temperature of the cast alloy flakes N.
The heat-retaining device 3 may have the structure shown in
Similar to the heat-retaining device 3 shown in
The inclination device 13 has a rotation shaft 55 provided with the heat-retaining container 52, and a movable device (not shown in
The heat-retaining container 52 is supported while an opening portion 52a faces outwardly so as to be able to rotate by the rotation shaft 55 which extends in the substantially horizontal direction. The inclination and rotation of the heat-retaining container 52 are controlled by the movable device.
The heat-retaining container 52 has the opening portion 52a at the upper portion. The cast alloy flakes N are supplied into the heat-retaining container 52 through the opening portion 52a. In addition, the heat-retaining container 52 has an outlet portion 53a on one side wall (side portion), and a gate plate 53 which can move in the vertical direction so as to open or close the outlet portion 53a. The movement of the gate plate 53 in the vertical direction can be controlled by a moving device (not shown in
That is, the cast alloy flakes N are supplied from the crushing device 21 into the heat-retaining container 52 through the opening portion 52a. Then, the gate plate 53 provided with the heat-retaining container 52 moves upwardly, and thereby the outlet portion 53 which has been closed by the gate plate 53 is opened. When the heat-retaining container 52 inclines and rotates by the movable device, the cast alloy flakes N are sent to the container 5 through the outlet portion 53a.
When the inclination and rotation of the heat-retaining container 52 is controlled by the movable device, and the movement of the gate plate 53 is controlled by the transfer device, it is possible to control the maintaining time after the cast alloy flakes N are stored in the heat-retaining container 52 before the cast alloy flakes N are sent to the container 5.
Similar to the heat-retaining device 3 shown in
In the heat-retaining device 30 shown in
When the cast alloy flakes N are produced using the production apparatus 10 shown in
The heat-retaining time for the cast alloy flakes N is preferably 30 seconds or more, more preferably in a range of from 2 minutes to several hours, and most preferably in a range of from 2 minutes seconds to 30 minutes. When the heat-retaining time is 2 minutes or more, the coercive force can be further improved. It is possible to maintain for several hours. However, when the productivity is concerned, 30 minutes or less is preferable.
There is a heat-retaining time lug between the cast alloy flake N which is supplied at first and the cast alloy flake N which is supplied at the end. It is preferable that the heat-retaining time of the cast alloy flake N which is supplied at first and the heat-retaining time of the cast alloy flake N which is supplied at the end are both adjusted in that range.
The production apparatus 10 shown in
In addition, the production apparatus 10 shown in
Since the inclination device 13 has the rotation shaft 55 provided with the heat-retaining container 52, and the movable device for rotating the rotational shaft 55 to incline and rotate the heat-retaining container 52. Therefore, the cast alloy flakes N, which are supplied from the crushing device 21, are stored in the heat-retaining container 52, and the cast alloy flakes N in the heat-retaining container 52 can be sent to the container 5 by inclining and rotating the heat-retaining container 52. At this time, it is possible to control the heat-retaining time of the cast alloy flakes N by controlling the inclination and rotation of the heat-retaining container 52. Therefore, it is also possible to maintain constantly the heat-retaining time of the cast alloy flakes N and make the quality of the cast alloy flakes N uniform.
In addition, the cast alloy flakes N in the heat-retaining container 52 can be sent to the container 5 by controlling the movement of the gate plate 53 and the rotation of the heat-retaining container 52. Therefore, it is possible to make the rotation angle of the heat-retaining container 52, when the cast alloy flakes N are sent, smaller, compared with a case in which the heat-retaining container 52 does not have the openable outlet portion 53 on the side wall, and the cast alloy flakes N are sent from the opening portion 52a formed upper portion of the heat-retaining container 52. Thereby, size of the production apparatus 10 can be reduced, and space for the production apparatus 10 can also be reduced.
In addition, the heat-retaining container 52 is rotatably supported such that the opening portion 52a faces outwardly by the rotational shaft 55 which extends in the substantially horizontal. Therefore, it is possible to swing the heat-retaining container 52 having the opening portion 52a facing upwardly within an angle range such that the cast alloy flakes N are not spilled, while maintaining the temperature of the cast alloy flakes N in the heat-retaining container 52. Thereby, the cast alloy flakes N can be stored uniformly in the heat-retaining container 52, and the temperature of the cast alloy flakes N in the heat-retaining container 52 can be uniformly kept. Therefore, the cast alloy flakes N having a uniform quality can be produced.
Moreover, for example, it is also possible to use the upper and lower heaters 31a and 31b in the production apparatus 1 shown in
The production apparatus for an alloy of the present invention is not limited to the above embodiments. The constitution of the production apparatus according to the present invention can be changed as long as the change of the constitution is within the scope of the present invention.
For example, although the belt conveyor 51 is used as the movable device for moving freely the storage container, it is also possible to use a self-propelled storage container having a carriage with tires. Of course, it is also possible to set rails and make the carriage move along the rails.
In addition, a hopper for introducing the cast alloy flakes N above the heat-retaining container may be provided between the crushing device and the heat-retaining and storing device. In this case, it is possible to prevent scattering of the cast alloy flakes N into the heat-retaining and storing device, when the cast alloy flakes N are sent from the crushing device into the heat retaining device.
In addition, the production apparatus according to the present invention can be used not only for the R-T-B-based alloy, but also for a thermoelectric semiconductor alloy, or a hydrogen-storing metal alloy.
Examples of the thermoelectric semiconductor alloy can include alloys, which are shown by the general formula A3-xBxC (in the general formula, A and B denote at least one element selected from the transition metals, such as Fe, Co, Ni, Ti, V, Cr, Zr, Hf, Nb, Mo, Ta, and W, C denotes at least one element selected from the elements in 13rd and 14th groups, such as Al, Ga, In, Si, and Ge).
In addition, alloys can be used, which are shown by the general formula ABC (in the general formula, A and B denote at least one element selected from the transition metals, such as Fe, Co, Ni, Ti, V, Cr, Zr, Hf, Nb, Mo, Ta, and W, C denotes at least one element selected from the elements in 13rd and 14th groups, such as Al, Ga, In, Si, and Ge).
In addition, rare-earth elements containing alloys can also be used, which are shown by the general formula REx(Fe1-yMy)4Sb12 (in the general formula, RE means at least one of La and Ce, M denotes at least one element selected from the group consisting of Ti, Zr, Sn, and Pb, and x and y satisfy the relationship of 0<x≦1, and 0<y<1).
Furthermore, rare-earth elements containing alloys can also be used, which are shown by the general formula REx(Co1-yMy)4Sb12 (in the general formula, RE means at least one of La and Ce, M denotes at least one element selected from the group consisting of Ti, Zr, Sn, Cu, Zn, Mn and Pb, and x and y satisfy the relationship of 0<x≦1, and 0<y<1).
As the hydrogen-storing metal alloy, AB2 type alloy (alloy containing a transition element, such as titanium, manganese, zirconium, and nickel, as a base), or AB5 type alloy (alloys containing a rare-earth element, niobium, and the zirconium, and at least one transition element having catalyst functions, such as nickel, cobalt, aluminum, etc. with a ratio of 1:5) can be used.
In order to produce the rare-earth permanent magnet of the present invention, for example, the cast alloy flakes containing the R-T-B-based alloy are finely pulverized such that the average particle diameter is in a range of from 3 to 5 μm (measured by a laser diffraction meter), the obtained powder is compacted using a molding device in a transverse magnetic field, and then this is sintered under vacuum conditions.
Since the rare-earth element containing magnet in this embodiment contains the R-T-B-based alloy produced by the production apparatus according to the present invention, the coercive force is high and magnetic properties are also excellent.
In order to obtain a raw material, metal neodymium, metal dysprosium, ferroboron, cobalt, aluminum, copper, and iron were added to an aluminum crucible so that the raw material contained 28% of Nd, 4.5% of Dy, 0.96% of B, 1.0% of Co, 0.15% of Al, 0.10% of Cu, and the remainder of Fe as a mass ratio, and these were melted in a high frequency melting furnace in an argon gas atmosphere at 1 atom to prepare a molten alloy.
Subsequently, the molten alloy was supplied to the production apparatus shown in
Moreover, the diameter of the cooling roller was 600 mm, and the material constituting the cooling roller was an alloy containing a small amount of Cr and Zr, and Cu as the remainder. The inside of the cooling roller was cooled.
The rotating speed of the cooling roller during casting was 1.3 m/s. When the average temperature of the cast alloy when it was removed from the cooling roller was measured using a radiation thermometer, the average temperature was 890° C. The difference between the highest temperature and the lowest temperature was 35° C.
The melting point of the R2T14B phase in the obtained alloy was about 1,170° C. Therefore, the difference between the average removing temperature and the melting point was about 280° C.
In addition, the average cooling rate of the cast alloy on the cooling roller was 980° C./s, and the average thickness of the cast alloy was 0.29 mm.
The obtained cast alloy flakes were stored in the heat-retaining container 32 of the heat-retaining device 3 shown in
The cast alloy flakes of Example 2 were produced in a manner identical to that of Example 1, except that the cast alloy flakes were stored in the heat-retaining container 52 of the heat-retaining device 30 shown in
The cast alloy flakes of Comparative Example 1 were produced in a manner identical to that of Example 1, except that the heat-retaining treatment was not carried out.
Then, the cast alloy flakes in Examples 1 and 2, and Comparative Example 1 were finely pulverized such that the average particle diameter was 5 μm (measured by a laser diffraction meter), and compacted using the molding device in a transverse magnetic field in a 100% nitrogen atmosphere. The molding pressure was 0.8 t/cm2, and the magnetic field in the cavity of the mold was set to 15 kOe.
The obtained mold was maintained at 500° C. for 1 hour under a vacuum of 1.33×10−5 hPa, and subsequently this was maintained at 800° C. for 2 hours under a vacuum of 1.33×10−5 hPa. After that, this was further maintained at 1030° C. for 2 hours under a vacuum of 1.33×10−5 hPa. Thereby, the obtained compacts were sintered. The sintered density was 7.67-7.69 g/cm3 or more, which is sufficient density.
In addition, the sintered body was heated at 530° C. for 1 hour in an argon atmosphere, and the R-T-B-based magnets in Examples 1 and 2 and Comparative Example 1 were obtained.
The magnetic properties of the obtained R-T-B-based magnets were measured by the pulse form BH curve tracer. The results are shown in
It is clear from
The production apparatus for an alloy according to the present invention can improve various properties of an alloy. In particular, when the alloy is the R-T-B-based alloy, the coercive force can be improved by retaining the temperature. Therefore, it is possible to produce a rare-earth element magnet having a high coercive force without increasing the compositional ratio of Dy and Tb in the R-T-B-based alloy.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-247851 | Sep 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/066827 | 9/18/2008 | WO | 00 | 3/15/2010 |
