Patent Grant
7958929
The present invention relates to an apparatus for producing an alloy. In particular, the present invention relates to an apparatus for producing a rare earth element-containing alloy that includes an R-T-B type alloy (wherein R is at least one or more elements of rare earth elements including Y, T is a metal which always includes Fe, and B is boron).
R-T-B type magnets, which have the highest magnetic energy product among permanent magnets, have been applied to hard disks (HD), MRIs (magnetic resonance imaging), various types of motors and the like due to their excellent properties. In recent years, their application for motors used in cars has been increased because energy saving is highly expected and the heat-resistance of the R-T-B type magnets has been improved.
The R-T-B type magnets mainly contain Nd, Fe, and B, and therefore, they are generally called an “Nd—Fe—B type” or “R-T-B type” magnet. The R of the R-T-B type magnet represents mainly those in which a part of Nd is substituted with other rare earth elements such as Pr, Dy, and Tb, namely at least one of these rare earth elements including Y T represents those in which a part of Fe is substituted with metals such as Co and Ni. B represents Boron in which a part of Boron can be substituted with C or N. In addition, Cu, Al, Ti, V, Cr, Ga, Mn, Nb, Ta, Mo, W, Ca, Sn, Zr, Hf, etc. may be added singularly or in combination as additional elements in the R-T-B type magnet.
An R-T-B type alloy, which turns into the R-T-B type magnet, is an alloy which has a main phase of R2T14B, namely a ferromagnetic phase that contributes to magnetization, and which simultaneously has non-magnetic R-rich phase having a low melting temperature in which the rare-earth elements are concentrated, and the R-T-B type alloy is an active metal. Therefore, the R-T-B type alloy has been molten or cast generally in a vacuum or an inert gas. Also, in order to produce a sintered magnet from a block of the cast R-T-B type alloy by way of the powdered metal technique, the block of the alloy is crushed into alloy powder of about 3 μm (measured using a Fisher Sub-Sieve Sizer (FSSS)), then pressed in a magnetic field, and sintered at a high temperature of about 1000° C. to 1100° C. in a sintering furnace. Then, the sintered alloy is generally subjected to the heating treatment, mechanical processing, and further plated to improve the erosion resistance, thereby forming a sintered magnet.
The R-rich phase of the R-T-B type sintered magnet has the following important roles:
Consequently, if the state of the dispersion of the R-rich phases in the shaped magnet is inferior, this causes partial sintering-deficiency and low magnetization, and it is therefore important that the R-rich phases are uniformly dispersed in the shaped magnet. The distribution of the R-rich phases is considerably affected by the organization of the material, namely R-T-B type alloy.
Another problem rises in the casting of the R-T-B type alloy, in which α-Fe generates in the cast alloy. α-Fe has deformability, and therefore, is not crushed and remains in the crusher. This not only decreases the crushing efficiency of the alloy but also affects compositional alteration and the particle size distribution before and after crushing. Moreover, if α-Fe remains in the magnet even after sintering, then the magnetic property of the magnet will deteriorate. Therefore, it has been considered that α-Fe should be excluded from the material alloy as much as possible. This is why α-Fe has been eliminated in conventional alloys by subjecting them to homogenizing treatment conducted at a high temperature for an extended time where necessary. A small amount of α-Fe present in the material alloy can be eliminated by way of the homogenizing treatment. However, the elimination requires the solid phase dispersion at an extended period because α-Fe is present as peritectic nuclei. Consequently, the elimination of α-Fe is actually extremely difficult when the ingots have a thickness of several centimeters and the amount of the rare earth elements is 33% or less.
The strip cast method (abbreviated as “SC method”) has been developed and applied to practical processes, in which a block of the alloy is cast at a more rapid cooling rate in order to solve the problem in which α-Fe generates in the R-T-B type alloy.
The SC method is a technique in which a thin lamina of about 0.1 mm to 1 mm is cast by pouring the molten alloy onto a copper roller whose inside is water-cooled, and the alloy is quenched and solidified. In the SC method, because the molten alloy is extensively cooled to the temperature at which an R2T14B phase (main phase) generates, or below this temperature, the R2T14B phase can be generated directly from the molten alloy and the deposition of α-Fe can be controlled. Furthermore, the crystalline organization of the alloy becomes refined by way of the SC method, and therefore, an alloy that has an organization where the R-rich phases are finely dispersed can be produced. The R-rich phase reacts with hydrogen in a hydrogen atmosphere, expands and becomes a fragile hydride. By applying this property, fine cracks are incorporated therein, matching the degree of the dispersion of the R-rich phases. When the alloy is finely crushed after such a hydrogenation process, a large number of the fine cracks generated by way of the hydrogenation causes the alloy to break, and the crushability is very excellent. Thus, as a thin lamina of the alloy cast by way of the SC method has internal R-rich phases finely dispersed therein, the dispersibility of the R-rich phases in the crushed and sintered magnet is also excellent, thereby successfully improving the magnetic property of the magnet (for example, patent document 1).
In addition, the thin lamina of the alloy cast by way of the SC method has excellent homogeneity of the organization. The homogeneity of the organization can be compared with respect to particle diameters of the crystals or the state of the dispersion of the Rich-phases. In the thin lamina of the alloy produced by way of the SC method, although chill crystals sometimes generate on the side of the thin lamina adjacent to the casting roller (hereinafter, referred as the “casting-roller side”), a properly refined and homogeneous organization on the whole, which resulted from the rapid-cooling and solidification, can be obtained.
As explained above, when the R-T-B type alloy cast by way of the SC method is applied to the production of a sintered magnet, the homogeneity of the R-rich phases in the produced magnet is enhanced, and the harmful effects to the crushing process and the magnetization owing to α-Fe can also be prevented. Thus, the block of the R-T-B type alloy cast by way of the SC method has an excellent organization for producing a sintered magnet. However, as the properties of the magnet improve, further improvement of the R-T-B type alloy has been sought.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. H5-222488
As described above, the R-T-B type alloy is an alloy that mainly includes an element “R” in which a part of Nd is substituted with the other rare earth elements such as Pr, Dy and Tb; an element “T” in which a part of Fe is substituted with metals such as Co and Ni; and “B” (boron). In general, the heat-resistance of the R-T-B type magnet is evaluated on the basis of the magnitude of its coercive force. The coercive force increases as the compositional ratios of Dy and Tb in the R-T-B type alloy increase. However, Dy and Tb are very expensive metals. Therefore, there has been a problem in which the addition of Dy and Tb to produce an R-T-B type magnet is too costly.
Furthermore, the addition of Dy and Tb indeed improves the coercive force, but tends to decline the remanent magnetic flux density. This undesirably results in the decline of the hard magnetic characteristics.
The present invention was accomplished to solve the above problems. The object of the present invention is to provide an apparatus for producing a rare earth element-containing alloy, which makes it possible to produce a rare earth magnet that has a high coercive force.
In order to solve the above-described object, the present invention adopts the following:
As described above, according to the apparatus for producing an alloy of the present invention, the thin laminas of the cast alloy after casting and crushing are subjected to the temperature-keeping treatment or the heating treatment, so that the properties of the alloy can be improved.
In particular, when the produced alloy is an R-T-B type alloy, its coercive force can be improved by way of the temperature-keeping treatment, and a rare earth magnet having excellent coercive force can be produced.
Hereinafter, one preferred embodiment of the apparatus for producing an alloy of the present invention is explained by referring to the figures. However, it should be understood that the figures are used only for describing the configuration of the apparatus, and the shown size, width, scales, etc. of each device does not always reflects those of the actual apparatus for producing an alloy.
[Format of the Apparatus for Producing an Alloy]
An apparatus for producing an alloy 1 shown in
Also, the production apparatus 1 shown in
A gate 6e is provided in the temperature-keeping storage chamber 6b, and the temperature-keeping storage chamber 6b is closed with the gate 6e except that the container 5 is conveyed outside the temperature-keeping storage chamber 6b.
The inside of the chamber 6 is in the state of reduced pressure of an inert gas, and examples of the inert gas include argon.
In addition, a cooling chamber may be provided on the side of the temperature-keeping storage chamber 6b across the gate 6e. Also, the cooling chamber may be equipped with another gate, and the container 5 may be designed to move outside the chamber 6 while leaving this gate open.
The casting device 2 is also equipped with the crushing device 21 that crushes blocks of the cast alloy formed by way of casting into thin laminas of the cast alloy. Moreover, a hopper 7 is provided between the casting device 2 and the opening-closing stage group 32. The hopper 7 directs the thin laminas of the cast alloy onto the opening-closing stage group 32.
Hereinafter, each of the devices included in the production apparatus 1 is further described in detail.
[Structure of the Casting Device]
As shown in
The molted alloy L is prepared in a high-frequency melting furnace which is provided outside the chamber 6 (not shown in the figures). In the high-frequency melting furnace, materials are charged into a refractory pot in a vacuum or in an atmosphere of an inert gas, and the charged materials are molten by way of the high-frequency melting method, thereby preparing a molten alloy. The temperature of the molten alloy L varies with types of alloy contents, but it is adjusted within a range of 1300° C. to 1500° C. As described in
The tundish 23 may be equipped with a flow-adjusting system and/or a slag-removing system where necessary. Also, the cooling roll 22 has a water-cooling system inside (not shown in the figures), and the circumferential surface 22a of the cooling roll 22 is cooled by the water-cooling system. With regard to the material for the cooling roll 22, a copper or copper alloy is suitable because they have excellent thermal conductivity, and are easily available. The supplying rate of the molten alloy L and the revolving speed of the cooling roll 22 are controlled according to the thickness of the cast alloy M, but it may be suitable that the revolving speed of the cooling roll 22 be about 0.5 to 3 m/s at a circumferential speed. Depending on the material for the cooling roll 22 or the condition of the circumferential surface 22a, metals often tend to adhere to the circumferential surface 22a of the cooling roll 22. Therefore, where necessary, a cleaning unit may be provided therein, so that the quality of the produced R-T-B type alloy will be stable. The cast alloy M solidified on the cooling roll 22 is separated from the cooling roll 22 at the side opposite to the tundish 23.
As shown in
[Structure of the Heating Device]
As shown in
With regard to its heating system, any one of the resistance heating, infrared heating, and induction heating can be adopted. Also, the main body 31b, for example, may be any heating element such as metal wires, silicon carbide, and graphite.
The heater 31 has an opening part 31c, and an outlet 7a of the hopper 7 is disposed in the opening part 31c. Consequently, the thin laminas N of the cast alloy that falls down from the casting device 2 and that passes through the hopper 7 can be supplied to the opening-closing stage group 32 of the container 5 which is provided below the heater 31.
Moreover, the heater 31, as shown in
The opening-closing stage group 32 included in the heating device 3 is integrated with the storage container 4 to form the container 5. That is, the container 5 shown in
The opening-closing stage group 32 is equipped with a plurality of opening-closing stages 33. Each opening-closing stage 33 is disposed along the moving direction of the container 5. The opening-closing stage group 32 shown in
Each opening-closing stage 33 leaves the thin laminas N of the cast alloy supplied from the casting device 2 mounted thereon to keep the temperature or to heat them with the heater 31 at a predetermined period, and drops the thin laminas N of the cast alloy to the storage container 4 after the temperature-keeping or heating period.
The opening-closing stage 33 is further explained in detail. Each opening-closing stage 33 is equipped with a stage plate 33a, and an opening-closing system 33b which opens or closes the stage plate 33a. Each opening-closing system 33b has a rotating shaft 33b1 attached to one side of the stage plate 33a; and a driving unit (not shown in the figures), which rotates the rotating shaft 33b1. Each driving unit can freely rotate the rotating shaft 33b1, such that the inclining angle of each stage plate 33a can be controlled separately. The inclining angle of each stage plate 33a can be set anywhere in the range of 0° (where the stage plate 33a is horizontal (the position shown in
The opening-closing stage 33 is in a closed state when the stage plate 33a is in a horizontal position (when the inclining angle is about0°) or when the stage plate 33a is inclined to such a degree that the thin laminas N of the cast alloy do not fall down from there. On the other hand, the opening-closing stage 33 is in an opened state from the condition in which the stage plate 33a, for example, is slightly inclining to the condition in which the stage plate 33a is vertical (when the inclining angle is about 90°). When the opening-closing stage 33 is in the closed state, the thin laminas N of the cast alloy can be mounted on the stage plate 33a. When the opening-closing stage 33 is in an opened state, the stage plate 33a is in an inclined state, and the thin laminas N of the cast alloy can fall, thereby enabling them to fall into the storage container 4.
Thus, the opening-closing stage 33 can leave the thin laminas N of the cast alloy mounted on the stage plate 33a during a predetermined temperature-keeping period by actuating the opening-closing system 33b, and then, can drop the thin laminas N of the cast alloy down into the storage container 4 by making the inclining angle of the stage plate 33a larger.
In addition, the opening-closing stage 33 can function as a cover for the storage container 4. That is, the storage container 4 is closed when the opening-closing stages 33 are in a closed state. This prevents the heat of the heater 31 from transmitting to the storage container 4, thereby saving the inside of the storage container 4 from heating up. In this way, the opening-closing stages 33 can block the heat-transmission from the heater 31 whereby the thin laminas N of the cast alloy stored in the storage container 4 that were already subjected to the heat-keeping treatment are not subjected again to the temperature-keeping or heating, and the quality of the thin lamina N of the cast alloy is kept stable.
Next, a plurality of cooling plates 4a is provided inside the storage container 4 as shown in
Various metals such as a stainless steel, iron, HASTELLOY, and INCONEL are applied to the materials for the opening-closing stage 33 and the storage container 4 as long as they can be used at a high temperature.
As shown in
[The Operation of the Apparatus for Producing an Alloy]
Next, the operation of the above-described production apparatus 1 will be explained. All
As shown in
Then, thin laminas N of the cast alloy are prepared by actuating the casting device 2. In reference to
The composition of the molten alloy L is represented, for example, by the general formula R-T-B. “R” represents mainly those in which a part of Nd is substituted with the other rare earth elements such as Pr, Dy and Tb, namely at least one of the rare earth elements including Y. “T” represents those in which a part of Fe is substituted with metals such as Co and Ni. “B” represents boron in which a part of boron can be substituted with C or N. In addition, Cu, Al, Ti, V, Cr, Ga, Mn, Nb, Ta, Mo, W, Ca, Sn, Zr, Hf, etc. may be added singularly or in combination as additional elements. The composition ratios of R and B are 28 to 33% and 0.9 to 1.3% by mass respectively, and the balance is T. A part of R may be substituted with 15% by mass of Dy and/or 15% by mass of Tb. However, the composition of the molten alloy applied to the production apparatus 1 of the present invention is not limited to the above-described range, and any composition for R-T-B type alloys can be applied.
It is preferable that the average cooling speed of the molten alloy on the cooling roll 22 be 300° C. to 3000° C. per second. When the cooling speed is 300° C. per second or more, sufficient cooling speed can prevent the deposition of α-Fe, and can prevent organizations such as an R-rich phase and R2T17-phase from being coarse. When the cooling speed is 3000° C. per second or less, its cooling rate does not grow excessive whereby the thin laminas of the cast alloy can be supplied to the heating device 3 at a proper temperature. Also, there is a merit that the thin laminas of the cast alloy are not excessively cooled, and therefore, it is unnecessary for them to be heated again. In addition, the average cooling speed can be calculated by dividing the difference between the temperatures of the molten alloy directly before touching the cooling roll and when separating from the cooling roll by the time that the molten alloy touches the cooling roll.
Furthermore, the average temperature of the cast alloy M when separating from the cooling roll will slightly vary depending on a slight change in the condition of touching the cooling roll 22, changes of the thickness, among others. For example, the surface of the alloy is scanned in the cross direction with a radiation thermometer from when casting begins to when casting ends whereby the average temperature of the cast alloy M when separating from the cooling roll can be calculated by averaging the measured values.
It is preferable that the average temperature of the cast alloy M when separating from the cooling roll 22 be lower by 100 to 500° C. than the solidifying temperature of the molten alloy in the equilibrium state of the R2T14B-phase, and it is more preferably lower by 100 to 400° C. The melting temperature of the R2T14B-phase is around 1150° C. in the ternary system of Nd—Fe—B. However, the melting temperature varies according to the substitution of Nd to the other rare earth elements, the substitution of Fe to the other transition elements, and types or amounts of the other additional elements. If the difference between the average temperature of the cast alloy M when separating from the cooling roll 22, and the solidifying temperature of the cast alloy M in the equilibrium state of the R2T14B-phase is less than 100° C., the cooling speed is insufficient. On the other hand, if the difference is over 500° C., the cooling speed is too fast, and the cooling of the molten alloy becomes excessive. The degree of such excessive cooling is not uniform inside the alloy, and it varies depending on the condition of touching the cooling roll, and the distance from the site contacting with the cooling roll.
Next, as shown in
The amount of the thin laminas N of the cast alloy piled on the opening-closing stage 33A may be properly adjusted according to the area of the stage plate 33a. However, the thin laminas N of the cast alloy are continuously supplied from the casting device 2, they will overflow from the opening-closing stage 33A in time although it also depends on the supplying speed.
Therefore, in the production apparatus 1 of the present embodiment, the container 5 is moved to the left side hand as shown in
The piling amount of the thin laminas N of the cast alloy with respect to each of the opening-closing stages 33A to 33E may be monitored with their mass by providing each stage plate 33a with a mass-detecting system, or may be controlled by adjusting the piling period with respect to each stage plate 33a based on the production amount of the thin laminas N of the cast alloy per time that is calculated from the casting or crushing speed of the casting device 2.
During this time, the thin laminas N of the cast alloy piled on each of the opening-closing stages 33A to 33E are kept at a predetermined temperature or heated with the heater 31. It is preferable that the keeping temperature be lower than the temperature of the thin lamina N when separating from the cooling roll (separating temperature), and for example, it is preferably within a range of (the separating temperature—100° C.) to the separating temperature, and it is more preferably within a range of (the separating temperature—50° C.) to the separating temperature. More specifically, the keeping temperature is preferably within a range of 600° C. to 900° C. Also, when the separating temperature declines for any reason, the thin laminas N of the cast alloy can be heated and kept at a predetermined temperature by setting the keeping temperature higher than the separating temperature. It is preferable that the heating range be within 100° C., and more preferably within 50° C. If the heating range is too large, the yield will decline.
Furthermore, the period of the temperature-keeping is preferably 30 seconds or more, more preferably 30 seconds to about several hours, and most preferably 30 seconds to 30 minutes. The coercive force of the R-T-B type alloy can be enhanced by way of subjecting the thin laminas N of the cast alloy to the temperature-keeping treatment. When the keeping temperature is 600° C. or more, the coercive force can be sufficiently enhanced. Also, when the coercive force is 900° C. or less, the deposition of α-Fe can be prevented, and the organizations such as the R-rich phase and the R2T17-phase can be prevented from being coarse. If the temperature-keeping time is 30 seconds or more, then the coercive force can be sufficiently enhanced. That is, the thin laminas of the cast alloy may be subjected to the temperature-keeping treatment for several hours, but the temperature-keeping time is preferably 30 minutes or less in terms of the yielding efficiency.
In addition, if they are kept at 1000° C., the coercive force can be improved. However, such a temperature makes organizations coarse. Furthermore, the particle distribution or the fluidity of the fine powder when they are finely crushed, and the sintering temperature may unfavorably change. When they are kept at 1000° C., it is required to consider its influence to subsequent processes.
Next, as shown in
With regard to the thin laminas N of the cast alloy piled on the opening-closing stages 33A to 33E, they are successively dropped into the storage container 4 by making each opening-closing stage in an opened state as shown in
As described above by referring to
The thin laminas N of the cast alloy that dropped into the storage container 4 are in contact with the cooling plate 4a whereby the heat is absorbed into the cooling plate 4a, and the thin laminas N of the cast alloy are consequently cooled down.
If the casting and crushing processes by the casting device 2 are subsequently conducted after that, the container 5 can be moved to the right hand in the figures while all opening-closing stages 33 are made in a closed state, and the thin laminas N of the cast alloy are successively mounted on each opening-closing stage 33 in accordance with the preparation of the thin laminas N of the cast alloy.
To the contrary, if the casting and crushing processes by the casting device 2 are terminated, all opening-closing stages 33 are switched to in a closed state to prevent the heat of the heater 31 from reaching the storage container 4. Then, the gate 6e of the temperature-keeping storage chamber 6b is opened, and the container 5 is conveyed outside the chamber 6.
Also, if a cooling chamber is provided in the chamber, the gate 6e of the temperature-keeping storage chamber 6b is opened, the container 5 is conveyed to the cooling chamber, and the thin laminas N of the cast alloy inside the container 5 are allowed to stand in order to cool. When the cooling is completed, the gate of the cooling chamber is opened, and the container 5 may be carried outside the chamber 6.
As explained above, because the production apparatus 1 is equipped with the heating device 3 that keeps the thin laminas N of the cast alloy at a predetermined temperature or that heats them, the coercive force of the thin laminas N of the cast alloy made of the R-T-B type alloy can be improved whereby an R-T-B type magnet having excellent heat-resistance can be produced.
Also, the production apparatus 1 is equipped with the opening-closing stages 33 on which the thin laminas N of the cast alloy supplied from the casting device are mounted when they are in a closed state, and that drops the thin laminas N of the cast alloy into the storage container 4 when they are in an opened state; and the heater 31 that keeps the thin laminas N of the cast alloy mounted on the opening-closing stages 33 at a predetermined temperature or that heats them. This is why the temperature-keeping time for the thin laminas N of the cast alloy can be controlled by adjusting the opening or closing period of the opening-closing stages 33 without switching the heater 31 on or off, and this also results in miniaturization of the apparatus.
Also, according to the above production apparatus 1, the opening-closing stages 33 release the thin laminas N of the cast alloy to the storage container 4 when a predetermined temperature-keeping time passes after the thin laminas N of the alloy are mounted thereon whereby the coercive force of thin laminas N of the cast alloy can be greatly improved.
Also, according to the production apparatus 1, the heating device 3 is disposed below the casting device 2 whereby the thin laminas N of the cast alloy can be easily moved between two or three of the devices only by way of dropping them. Therefore, it is unnecessary to provide another system for delivering the thin laminas N of the cast alloy, and this can result in the miniaturization or space-saving for the production apparatus 1.
Also, according to the production apparatus 1, the storage container 4 and the opening-closing stages 33 are integrated to form the container 5 whereby the total thin laminas N of the cast alloy after the temperature-keeping treatment can be released to the storage container 4 without loss thereof. Also, because the storage container 4 and the opening-closing stages 33 are integrated to form one body, the miniaturization or space-saving for the production apparatus 1 can be achieved. Furthermore, the belt conveyor 51 which freely moves the container 5 is provided therein whereby the thin laminas N of the cast alloy after the temperature-keeping treatment can be quickly delivered out from the production apparatus 1.
Also, according to the production apparatus 1, the container 5 is equipped with a plurality of the opening-closing stages 33, and each opening-closing stage 33 is disposed along the moving-direction of the container 5 whereby thin laminas N of the cast alloy can be successively mounted on each opening-closing stage 33 by moving the container 5 even if thin laminas N of the cast alloy are continuously supplied from the casting device 2. Consequently, the thin laminas N of the cast alloy will not overflow from each opening-closing stage 33.
Also, according to the production apparatus 1, the thin laminas N of the cast alloy are successively released to the storage container 4 when a predetermined temperature-keeping time passes after the thin laminas N of the cast alloy are mounted on each opening-closing stage 33 whereby the temperature-keeping time can be fixed and the quality of the thin laminas N of the cast alloy can be consequently kept uniform.
Also, according to the production apparatus 1, the heater 31 is disposed between the casting device 2 and the opening-closing stages 33 along the moving direction of the container 5 whereby the distance between the thin laminas N of the cast alloy on each opening-closing stage 33 and the heater 31 can be fixed even while the container 5 moves. Consequently, the thin laminas N of the cast alloy can always be kept at a predetermined temperature in the same conditions.
Also, according to the production apparatus 1, the storage container 4 is equipped with the cooling plate 4a that cools the thin laminas N of the cast alloy whereby the thin laminas N of the cast alloy after the temperature-keeping treatment can be quickly cooled. Consequently, the temperature-keeping time will not be substantially extended, and the quality of the thin laminas N of the cast alloy can be improved.
Also, according to the production apparatus 1, the casting device 2 is equipped with the crushing device 21 whereby blocks of the cast alloy can be easily crushed into thin laminas N of the cast alloy, and this consequently makes it easier to treat the cast alloy in the heating device 3 or the storage container 4.
Also, according to the production apparatus 1, the hopper 7 that directs the thin laminas N of the cast alloy onto the opening-closing stages 33 is provided between the crushing device 21 and the opening-closing stages 33 whereby the thin laminas N of the cast alloy will not scatter inside the temperature-keeping storage chamber 6b, and the entire amount of the thin laminas N of the alloy can be delivered to the opening-closing stages 33 without loss thereof.
Also, according to the production apparatus 1, the heater 31 has the opening part 31c, and the outlet 7a of the hopper 7 is disposed in the opening part 31c whereby the outlet 7a of the hopper 7 faces the opening-closing stage 33 of the container 5, and the entire amount of the thin laminas N of the alloy can be therefore delivered to the opening-closing stages 33 without loss thereof as well as miniaturization and space-saving for the production apparatus 1 can be achieved.
Also, according to the production apparatus 1, the casting device 2 and the heating device 3 are provided inside the chamber 6 of an atmosphere of an inert gas whereby the R-T-B type alloy can be prevented from deteriorating.
Also, according to the production apparatus 1, a cooling chamber is provided inside the chamber 6, and the container 5 can be moved to the cooling chamber whereby the thin laminas N of the cast alloy stored in the container 5 that have already subjected to the temperature-keeping treatment can be delivered from the temperature-keeping storage chamber 6b, and they can be cooled. Consequently, the yield can be improved.
Also, according to the production apparatus 1, the rare earth element-containing alloy is an R-T-B type alloy whereby a magnet having high coercive force and excellent heat resistance can be produced.
The R-T-B type alloy is an alloy that mainly includes an element “R” where a part of Nd is substituted with the other rare earth elements such as Pr, Dy and Tb; an element “T” where a part of Fe is substituted with metals such as Co and Ni; and “B” (boron). The coercive force of the R-T-B type magnet formed of such an alloy generally increases as the composition ratios of Dy and Tb in the R-T-B type alloy increase, but the remanent magnetic flux density tends to decline on the contrary.
According to the production apparatus 1, the R-T-B type alloy can be subjected to the temperature-keeping treatment because the heating device 3 is provided therein whereby the coercive force of the magnet formed of the R-T-B type alloy can be improved. Consequently, the composition ratios of Dy and Tb in the alloy can be reduced. In addition, when the composition ratios of Dy and Tb in the alloy are reduced, the remanent magnetic flux density can also be improved.
The heating device is not limited to the above-described embodiment, and embodiments shown in
That is, the heater 131 shown in
Also, the protective cover 131c is disposed between the main body 131b and the container 5. When the thin laminas N of the cast alloy fall down to the opening-closing stages 33 of the container, the thin laminas N of the cast alloy may strike against the main body 131b because they rebound on the opening-closing stages 33. However, the protective cover 131c can protect the main body 131b from the thin laminas N of the cast alloy. In addition, the heater emitted from the main body 131b is radiated onto the thin laminas N of the cast alloy on the opening-closing stages 33 through the protective cover 131c.
The protective cover 131c may be a plate-shaped or mesh-like structure. If the protective cover 131c is plate-shaped, the use of a material that has excellent thermal conductivity and heat-radiation efficiency is preferable in order to sufficiently radiate the heat to the thin laminas N of the cast alloy. If it is mesh-like, it is preferable to use those which have pore sizes where the thin laminas N of the cast alloy cannot pass through the protective cover.
Next,
That is, the opening-closing stage group 132 illustrated in
Moreover, the partition panels 134 are provided on the boundary of each opening-closing stage 133. Each partition panel 134 is set to stand facing the direction of the heater 31.
When the thin laminas N of the cast alloy fall down to the opening-closing stages 133, the thin laminas N of the cast alloy rebound on the opening-closing stage 133, and may scatter into adjacent opening-closing stages 133. However, the partition panel 134 can prevent the thin laminas N of the cast alloy from scattering.
Furthermore, the partition panel 134 can prevent the thin laminas N of the cast alloy from piling around a boundary part of the opening-closing stage 133, and the all thin laminas N can be dropped into the storage container 4 without leaving them thereon.
In addition, the partition panel 134 may include an auxiliary heater in order to assist temperature-keeping for the thin laminas N of the cast alloy on the opening-closing stage 133. The use of the auxiliary heater can uniformly keep the temperature of the thin laminas N of the cast alloy.
Next,
That is, the heating device 303 shown in
The heater 331 includes a heater cover 331a and a main body 331b provided under the heater cover 331a. The function, the material, etc. of the heater cover 331a and the main body 331b are arranged in the same manner as the above-described heater 31.
Moreover, an outlet 7a of the hopper 7 is provided at the left side of the heater 331 whereby the thin laminas N of the cast alloy which have dropped from the casting device 2 through the hopper 7 can be delivered out to the belt conveyor 306.
Furthermore, the heater 331 is disposed along the longitudinal direction of the belt conveyor 306 at a regular distance from each other as shown in
In addition, in the heating device 303 shown in
Next, the belt conveyor 306 is disposed such that the end part 306a is arranged directly under the outlet 7a of the hopper 7 and the end part 306b is arranged directly over the container 305. The belt conveyor 306 extends from the end part 306a to the end part 306b along the heater 331. Also, the distance between the belt conveyor 306 and the heater 331 is almost fixed.
According to the above-described configuration, the thin laminas N of the cast alloy that has dropped from the casting device 2 through the hopper 7 can be subjected to the temperature-keeping by the heater 331 while being delivered by the belt conveyor 306. Then, the thin laminas N of the cast alloy can be released from the end part 306b of the belt conveyor 306 to the container 305. With regard to the temperature-keeping time, the starting point refers to when the thin laminas N of the cast alloy reach the belt conveyor 306, and the ending point refers to when they are sent from the end part 306b of the belt conveyor 306 to the container 305. Consequently, the temperature-keeping time can be adjusted by way of adjusting the driving speed of the belt conveyor 306.
Thus, according to the heating device 303 shown in
In addition, the container 305 is provided on another belt conveyor 51, and the container 305 can be moved to either the left or the right side hand of the figure. According to this structure, the relative position of the container 305 to the end part 306b of the belt conveyor 306 can be freely adjustable whereby the thin laminas N of the cast alloy can be prevented from piling at the same position of the container 305.
Next,
That is, the heating device 403 includes a heater 331; a container 305; the pushing device 406 disposed between the heater 331 and the container 305. The pushing device 406 delivers the thin laminas N of the cast alloy, which are supplied from the casting device, to the container 305 while they are kept at a predetermined temperature. In addition, the container 305 is equipped with a cooling plate 305a.
A heater 331 includes a heater cover 331a; a main body 331b provided under the heater cover 331a. The function, material, etc. of the heater cover 331a and the main body 331b are arranged in the same manner as the above-described heater 31.
Also, an outlet 7a of a hopper 7 is disposed at the left side of the heater 331 whereby the thin laminas N of the cast alloy that have been dropped the casting device 2 passing through the hopper 7 can be released to the pushing device 406.
Moreover, the heater 331, as shown in
In addition, in a heating device 403 shown in
Next, the pushing device 406 includes the base plate 406a; and a pushing member 406b that slides on the base plate 406a. The base plate 406a is disposed such that the end part 406a1 is arranged directly under the outlet 7a of the hopper 7 and another end part 406a2 is arranged directly over the container 305. The base plate 406a extends from the end part 406a1 to the end part 406a2 along the heater 331. Also, the distance between the base plate 406a and the heater 331 is almost fixed. The pushing member 406b moves from the end part 406a1 of the base plate 406a toward the end part 406a2 while being in contact with the base plate 406a. To the contrary, the pushing member 406b moves back from the end part 406a2 to the end part 406a1 while separating from the base plate 406a.
According to the above-described configuration, the thin laminas N of the cast alloy that have been dropped from the casting device 2 passing from the hopper 7 are piled on the base plate 406a, and the thin laminas N of the cast alloy are kept at a predetermined temperature by the heater 331 while the pushing member 406b delivers them to the end part 406a2 of the base plate by way of pushing. Then, the thin laminas N of the cast alloy are released from the end part 406a2 of the base plate 406a to the container 305. With regard to the temperature-keeping time, the starting point refers to when the thin laminas N of the cast alloy reach the base plate 406a, and the ending point refers to when they are sent from the end part 406a2 of the base plate 406a to the container 305. Consequently, the period for the temperature-keeping can be adjusted by way of controlling the driving speed of the pushing member 406b.
Thus, according to the heating device 403 shown in
In the same manner as
Next,
The vertical furnace 451 shown in
When the thin laminas N of the cast alloy are supplied to the above-described vertical furnace 451, the inside of the thin lamina-path 452 is filled with the thin laminas N of the cast alloy, and the thin laminas N of the cast alloy are successively pushed out from the thin lamina-path 452. The pushed out thin laminas N of the cast alloy are mounted on the table 462 of the table feeder 461, but they are further pushed out to the circumference of the table 462 when the rotating blade 463 rotates, and they are dropped into the container 305. The thin laminas N of the cast alloy are kept at a predetermined temperature or heated with the outside heater 453 while they pass through the thin lamina-path 452. The temperature-keeping time can be adjusted by controlling the balance between the supplying rate of the thin laminas N of the cast alloy to the vertical furnace 451, and the discharging rate of the thin laminas N of the cast alloy at the table feeder 461.
Thus, according to the heating device shown in
Next, another embodiment of the apparatus for producing an alloy is further described, wherein a vibrating feeder equipped with a heater is provided between a casting device and a heating device in order to uniformly keep the temperature of the thin laminas N of the cast alloy directly uniform after crushing. The structure is shown in
In the production apparatus shown in
A hopper 502b which is a path-way for the thin laminas of the cast alloy crushed by a crushing device 21 is disposed at the upstream of the thin lamina-path 502. Also, the inclined plane 502a has an outlet 502c at the downstream of the thin lamina-path 502, and a metal net 502d is attached to the outlet 502c. A retrieving outlet 502e is provided at the downstream from the outlet 502c to retrieve the thin laminas of the cast alloy having large particle sizes that could not pass through the metal net 502d, and a retrieving plate 502f is provided under the retrieving outlet 502e.
In addition, projections may be provided on the inclined plane 502a to entirely spread the sliding thin laminas of the cast alloy in the cross direction of the inclined plane 502a.
When the thin laminas of the cast alloy are supplied to the vibrating feeder 501 equipped with a heater, the thin laminas of the cast alloy slide off on the inclined plane 502a which is vibrated by the vibration-generating device 503. Then, the thin laminas of the cast alloy having small particles sizes pass through the metal net 502d, and drop from the hopper 7 into the heating device 3. On the other hand, the thin laminas of the cast alloy having large particle sizes further slide down onto the metal net 502d, and they are retrieved in the retrieving plate 502f from the retrieving outlet 502e. The thin laminas of the cast alloy are kept at a predetermined temperature or heated by the heater 504 while they slide down on the thin lamina-path 502. Accordingly, the temperature of the thin laminas of the cast alloy directly after crushing can be made uniform.
In addition, the present invention is limited to the above-described embodiment, and additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. For example, the configuration of the opening-closing stages 33 is not limited to the above-described embodiment. For example, the opening-closing stages 33 shown in
Also,
As an example of a driving member for the container 5, a belt conveyor 51 is shown. However, for example, the container 5 may be equipped with a truck having wheels to form a vehicle-type container, and the truck may be designed to run on a railroad which is built in the apparatus.
Furthermore, the following embodiments can be applied instead of installing the cooling plate inside the container.
One example is a storage container wherein a stainless steel net is provided parallel to the bottom of the container so as to form a space between the stainless steel net and the bottom of the container, and an inert cooling gas is injected thereto. In this device, the thin laminas of the cast alloy can be cooled by injecting a cooling gas thereto directly after they are dropped and retrieved therein, and the cooling rate for the thin laminas of the cast alloy can be further modulated by adjusting the volume of the cooling gas injected thereto.
In the above-described example, they are cooled by way of the gas-phase cooling with a gas flowing between the piles. Therefore, if a large amount of the thin laminas of the cast alloy is piled, and the container is large, then the piles also tend to be large, and their cooling rate may be accidentally limited, or they may be ununiformly cooled depending on the position of the container.
Such problems may be solved by applying another example, wherein the inside of the storage container is partitioned with a plurality of hollow partition panels, a cooling medium flows inside the hollow partition panels, and the cooling rate of the thin laminas of the cast alloy can be sped up by way of the contact cooling between the hollow partition panels and the thin laminas of the cast alloy. According to this technique, the cooling medium does not have direct contact with the thin laminas of the cast alloy. Therefore, a gas such as air other than inert gases, or a liquid such as water can be used as a cooling medium.
Yet another embodiment can be mentioned. This embodiment utilizes the technique in which vent holes are made at the bottom parts of the above-described hollow partition panels, and a part of the inert gas that is injected into the panels is released from the vent holes to the inside of the storage container to cool the thin laminas of the cast alloy. In general, it is effective to cool the thin laminas of the cast alloy as rapidly as possible with regard to cooling after the internal structures of the alloy are solidified. In particular, such rapid cooling is preferable when casting is continuously conducted.
Another heater can be provided on the down side of the stage plate 33a of the opening-closing stage 33, and the stage plate 33a may be heated by this heater. This heater may be used in combination with the heater 31. In addition, this embodiment may be applied to the above-described heating device 103 or 203.
Also, a heat-insulated structure may be provided on the down side of the stage plate 33a of the opening-closing stage 33 in order to prevent the heat generated from the heater 31 from transmitting to the inside of the container 5. In this case, as examples of such a heat-insulated structure, blocks or fibrous boards made of ceramics such as alumina and zirconia may be disposed on the down side of the stage plate 33a, or a plurality of thin metal plates are piled on the down side of the stage plate 33a while having a space between them. With regard to the materials for the thin metal plate, those having a melting temperature lower than the temperature of the thin laminas of the cast alloy can be used, and iron or stainless steel, for example, may be used. In addition, this embodiment can be applied to the above-described heating device 103 or 203.
Also, a heater may be provided in hopper 7 to prevent the thin laminas of the cast alloy from being cooled.
Also, the production apparatuses of the present invention can be applied to produce a thermoelectric semiconductor alloy or hydrogen absorbing alloy other than R-T-B type alloy.
The thermoelectric semiconductor alloys, for example, include alloys represented by the general formula A3-xBxC (wherein A and B represent at least one element of transition metals such as Fe, Co, Ni, Ti, V, Cr, Zr, Hf, Nb, Mo, Ta and W; and C represents at least one element of Group 13 or 14 such as Al, Ga, In, Si, Ge, and Sn).
Also, the thermoelectric semiconductor alloys can includes, for example, alloys represented by the general formula ABC (A and B represent at least one element of transition metals such as Fe, Co, Ni, Ti, V, Cr, Zr, Hf, Nb, Mo, Ta and W; and C represents at least one element of Group 13 or 14 such as Al, Ga, In, Si, Ge, and Sn).
Moreover, rare earth alloys represented by the general formula REx(Fe1-yMy)4Sb12 (wherein RE represents at least one element of La and Ce; and M represents at least one element selected from the group consisting of Ti, Zr, Sn, and Pb where 0<x≦1 and 0<y<1) can be also mentioned.
Furthermore, rare earth alloys represented by the general formula REx(Co1-yMy)4Sb12 (wherein RE represents at least one element of La and Ce; and M represents at least one element selected from the group consisting of Ti, Zr, Sn, Cu, Zn, Mn and Pb where 0<x≦1 and 0<y<1) can be also mentioned.
As examples of the hydrogen absorbing alloy, AB2-type alloys (those using a base material of a transition element alloy such as Ti, Mn, Zr and Ni) or AB5-type alloys (those using a base material of an alloy containing 5 parts of a catalytic transition element (Ni, Co, Al or the like) with respect to 1 part of a rare earth element, Nb, and/or Zr) can be mentioned.
The material mixture of neodymium metal, dysprosium metal, ferroboron, cobalt, aluminum, copper, and iron (where the alloy composition ratio becomes 22% of Nd, 9.5% of Dy, 0.96% of B, 1.0% of Co, 10.15% of Al, 0.10% of Cu, and the balance being Fe) was molten in the atmosphere of an argon gas at 1 atm pressure in the high-frequency melting furnace using an alumina crucible in order to prepare a molten alloy.
Then, this molten alloy was supplied to the casting device of the production apparatus shown in
In addition, the diameter of the cooling roll was 600 mm, the material of the cooling roll was an alloy in which a small amount of Cr and Zr is mixed with copper. The inside of the cooling roll was water-cooled, and the circumferential speed of the roll was 1.3 m/s when casting. The average temperature of the cast alloy M when separating from the cooling roll was measured with a radiation thermometer, and it was found 890° C. Furthermore, with regards to the measured values, the difference between the maximum temperature and the minimum temperature was 35° C. The melting temperature of the R2T14B-phase of the produced alloy was about 1170° C. Therefore, the difference between the melting temperature and the average temperature was 280° C. In addition, the average cooling rate of the blocks of the cast alloy on the cooling roll was 980° C./second, and the average thickness was 0.29 mm.
The produced thin laminas of the cast alloy were allowed to pass through the hopper 7 of the production apparatus shown in
On the other hand, thin laminas of the cast alloy of Comparative Example 1 were produced in the same manner as Examples 1 to 3 except that the temperature-keeping treatment was not conducted.
Then, each of thin laminas of the cast alloy was pressed with a molding machine in an atmosphere of 100% nitrogen and in the transverse magnetic field. The molding pressure was set 0.8 t/cm2 and the magnetic field of 15 kOe was generated in the mold cavity. The obtained compact was kept in a vacuum of 1.33×10−5 hPa at 500° C. for one hour, then kept in a vacuum of 1.33×10−5 hPa at 800° C. for two hours, and further kept in a vacuum of 1.33×10−5 hPa at 1030° C. for two hours whereby the compact was sintered. Their sintered densities ranged from 7.67 to 7.69 g/cm3 or more, and they had sufficient densities. These sintered products were further heated in an atmosphere of argon at 530° C. for one hour whereby R-T-B type magnets of Examples 1 to 3 and Comparative Example 1 were produced.
The magnetic properties of the obtained R-T-B type magnets were measured with a pulse-type B-H curve tracer. The result is shown in
As shown in
According to the present invention, the apparatus for producing an alloy can produce an R-T-B type magnet having high coercive force as well as reducing the cost with regard to the material used therein. The produced R-T-B type magnets can be applied to industrial products such as hard disks, MRI apparatuses and motors. Furthermore, the production apparatus of the present invention can be applied to the production of a thermoelectric semiconductor alloy or hydrogen absorbing alloy other than the R-T-B type alloy. Therefore, the apparatus for producing an alloy of the present invention has high industrial applicability.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-106793 | Apr 2006 | JP | national |
This application claims the priority of Japanese Patent Application No. 2006-106793, filed Apr. 7, 2006, and the priority benefit of U.S. Provisional Application No. 60/792,647, filed on Apr. 18, 2006, the contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/058124 | 4/6/2007 | WO | 00 | 5/15/2008 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2007/117037 | 10/18/2007 | WO | A |
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