JP4600690B2 - Manufacturing method of rare earth sintered magnet - Google Patents

Description

  The present invention relates to a method for producing a rare earth sintered magnet, and more particularly to a method for suppressing deformation of a molded body in a step of firing the molded body.

  R-Fe-B sintered magnets, known as a kind of rare earth sintered magnets, exhibit the highest magnetic properties among various permanent magnets and are relatively inexpensive. Has been adopted. Here, R is one or more rare earth elements, and B is boron. Rare earth sintered magnets are produced by pressure-molding alloy powder obtained by pulverizing rare earth alloys in a magnetic field and holding the compact at a predetermined temperature for a predetermined time in a sintering furnace. Has been. When the sintering process is performed in a state where the compact is exposed in the sintering furnace, an impurity gas such as oxygen, carbon, and water vapor in the furnace comes into contact with the compact. For example, when a rare earth element such as Nd contained in an R—Fe—B based sintered magnet is oxidized or carbonized, the characteristics of the magnet are greatly deteriorated. Therefore, the sintering process is performed in a state where the molded body is stored in the sintering container.

Various proposals have been made regarding this sintered container (for example, Patent Documents 1 to 4). These proposals are aimed at preventing deformation of the obtained sintered body when sintering is completed. The deformation of this sintered body will be described.
4 and 5 are views showing a state in which the molded body G is placed in the sintering container 20, FIG. 4 is a plan view thereof, and FIG. 5 is a cross-sectional view taken along line AA in FIG. The sintering container 20 includes a tray 21 having a bottom floor 21a and a side wall 21b erected from the bottom floor 21a, and a lid 22. FIG. 4 shows a state where the lid 22 is removed. Depending on the cross-sectional shape of the compact G, the sintering may be performed in a state where the compact G is placed vertically as shown in FIG. Note that whether or not it is placed vertically can be determined from the position of the center of gravity. When the same object is placed in a state where the center of gravity is relatively high, it can be called vertical placement, and conversely, the case where it is placed in a state where the center of gravity is relatively low can be called horizontal placement. When the sintering process is performed in a state where the compact G is placed vertically, the upper end portion of the compact (sintered body) G may hang down after sintering as shown in FIG. This deformation occurs in the molded body G placed at a specific part of the sintering container 20. That is, as shown in FIG. 4, the green compacts G are arranged in the sintered container 20, but the green compact G placed on the outermost periphery surrounded by the dotted line is exclusively deformed. The deformed molded body (sintered body) G cannot be handled as a product if the degree of deformation is large, and decreases the yield. In addition, an increase in the load of the machining process causes a reduction in productivity due to a reduction in processing capacity and an increase in processing man-hours, thereby increasing product costs.

JP 2005-171348 A JP 2006-249547 A JP 2006-66827 A JP 2006-265601 A

In Patent Document 1, the deformation occurs in the sintering process because the temperature in the sintering container 20 is not uniform. That is, Patent Document 1 states that the heating temperature is highest near the outermost periphery of the sintering vessel 20. Therefore, Patent Document 1 proposes to dispose a heat shield between the molded body G placed on the outermost periphery in the sintering container and the side wall 21b of the sintering container 20. However, even in the proposal of Patent Document 1, the deformation still occurs.
Moreover, in patent document 4, it arrange | positioned in the outer peripheral part of a sintering container by comprising a sintering container with the carbon fiber reinforced carbon composite material which is lower than a metal and shows the heat conductivity close | similar to a rare earth sintered magnet molded object. The temperature difference between the molded body and the molded body arranged at the center is reduced. However, if the sintered container is composed of a carbon fiber reinforced carbon composite material, the rate of temperature increase in the sintered container is slowed during the sintering process, and productivity is reduced.
Therefore, the present invention provides a technology that can effectively suppress deformation of the sintered body by making the heating temperature in the sintering container uniform while suppressing the decrease in the rate of temperature rise in the sintering container. The purpose is to provide.

In order to achieve the above object, the present inventors decided that the sintering container is a double container comprising an outer container and an inner container disposed inside the outer container, and the outer container is heated. It was conceived that the inner container was made of a material having a low thermal conductivity and the inner container was made of a material having a high thermal conductivity. The idea is to reduce the thermal conductivity of the outer container, thereby suppressing a rapid temperature rise in the vicinity of the side wall in the outer container. The purpose is to minimize the decrease in the temperature rise rate inside the container by arranging a high rate inner container. Based on this idea, when the sintering process was performed with a double container, the deformation of the sintered body could be extremely reduced. In addition, the decrease in the temperature increase rate could be minimized.
The present invention is based on the above study, and a rare earth sintered magnet that is sintered by heating from the outside of the sintering vessel in a state where a plurality of compacts made of alloy powder of a predetermined composition are arranged in the sintering vessel. The sintering container is composed of an outer container and an inner container disposed inside the outer container and containing a molded body, and the thermal conductivity of the outer container is that of the inner container. It is a method for producing a rare earth sintered magnet characterized by being smaller than the thermal conductivity.

In the method for producing a rare earth sintered magnet of the present invention, it is preferable that the outer container is made of a carbon fiber reinforced carbon composite and the inner container is made of a refractory metal.
Further, in the method for producing a rare earth sintered magnet of the present invention, it is preferable to arrange a getter between the outer container and the inner container, and this getter is substantially the same as the rare earth sintered magnet obtained by the present invention. It is preferable to be comprised from a sintered compact.

  According to the present invention, the deformation of the sintered body can be effectively suppressed by making the heating temperature in the sintering container uniform while suppressing the decrease in the temperature rise rate in the sintering container.

The method for producing a rare earth sintered magnet according to the present invention is characterized by a sintered container used during a sintering process. First, the sintered container will be described.
FIG. 1 is a diagram illustrating a state in which a sintering process is performed using a sintering container 10. As shown in FIG. 1, for example, a heater 3 is disposed in the sintering furnace 1, and the molded body placed in the sintering container 10 is heated to the sintering temperature by the heater 3. The sintering container 10 is subjected to a sintering process in a state where it is placed on the gantry 4 disposed in the sintering furnace 1.

FIG. 2 is a plan view showing the inside of the sintered container 10 in which the compact (sintered body) G is placed, and FIG. 3 is a partially enlarged sectional view of the sintered container 10.
As shown in FIGS. 2 and 3, the sintering container 10 includes an outer container 11 and an inner container 12 disposed inside the outer container 11.
The outer container 11 includes a box-shaped tray 11a having a bottom floor 111 and a side wall 112 standing from the bottom floor 111, and a lid 11b. The lid 11b covers the upper opening of the tray 11a. However, the lid 11b does not seal the outer container 11, and the inside and the outside of the outer container 11 can be ventilated.
The inner container 12 includes a box-shaped tray 12a having a bottom floor 121 and a side wall 122 standing from the bottom floor 121, and a lid 12b. The lid 12b also covers the upper opening of the tray 12a, but the inside and outside of the inner container 12 can be vented.
A plurality of molded bodies G are arranged inside the inner container 12. The molded body G is placed vertically and arranged inside the inner container 12 as described above.

  The outer container 11 and the inner container 12 are made of different materials, and the outer container 11 has a lower thermal conductivity than the inner container 12. Therefore, when the sintering container 10 is placed in the sintering furnace 1 and heated by the heater 3, the heat conductivity of the outer container 11 is low, thereby reducing the radiant heat from the outer container 11, The temperature difference inside the outer container 11 is reduced. The same applies to the inside of the inner container 12 disposed inside the outer container 11. Therefore, the heating temperature of each molded body G arranged inside the inner container 12 becomes more uniform. On the other hand, since the inner container 12 disposed inside the outer container 11 has high thermal conductivity, the temperature inside the inner container 12 is relatively easily heated, and the temperature rising rate inside the inner container 12 is Faster than the outside.

The outer container 11 may be a ceramic sintered body, for example, a zirconia (ZrO ₂ ) ceramic sintered body or a silicon nitride (Si ₃ N ₄ ) ceramic sintered body, preferably a carbon fiber reinforced carbon composite material. Composed. The carbon fiber reinforced carbon composite material is manufactured using a carbon fiber nonwoven fabric as a starting material. The outer container 11 is obtained, for example, by impregnating a carbon fiber nonwoven fabric with a resin to form a prepreg, then molding the prepreg into a predetermined shape to obtain a molded body, and then carbonizing and graphitizing the molded body. is there.
The thermal conductivity of the carbon fiber reinforced carbon composite material is 30 W / (m · ° C.) or less, for example, about 20 W / (m · ° C.). Therefore, it is suitable for the function as the outer container 11 described above, that is, for uniform temperature inside. However, if the thermal conductivity of the carbon fiber reinforced carbon composite constituting the outer container 11 is too low, the sintering process may take a long time even if the inner container 12 is made of a refractory metal. Accordingly, the thermal conductivity of the carbon fiber reinforced carbon composite material constituting the outer container 11 is preferably 5 W / (m · ° C.) or more.

Carbon fiber reinforced carbon composite materials are lighter than metal materials such as molybdenum. Therefore, even if the sintered container 10 has a double structure of the outer container 11 and the inner container 12, an increase in the weight of the entire sintered container 10 can be minimized.
Further, the carbon fiber reinforced carbon composite material has an advantage that the deformation amount is small even when heated to a high temperature of about 1000 to 1300 ° C., compared to molybdenum, which is a general material of a conventional sintered container. .

  The plate thickness of the carbon fiber reinforced carbon composite material constituting the outer container 11 is not particularly limited and should be appropriately set depending on conditions such as the size and the number of molded bodies G to be accommodated. It is preferable that it is a grade. If the plate thickness is less than 2 mm, the strength is insufficient, and there is a concern about breakage such as cracking or chipping during use. If the plate thickness exceeds 15 mm, the capacity of the molded body G per unit volume decreases.

  The inner container 12 is preferably made of a refractory metal. As the high melting point metal in the present invention, tungsten (W, melting point: 3410 ° C., thermal conductivity: 174 W / (m · ° C.)), molybdenum (Mo, melting point: 2620 ° C., thermal conductivity: 138 W / (m · ° C.) )), Rhenium (Re, melting point: 3180 ° C., thermal conductivity: 47.9 W / (m · ° C.)). The refractory metal in the present invention includes alloys of these metals with other metals. Among these, it is preferable to use molybdenum in view of price.

  Next, the thickness of the refractory metal constituting the inner container 12 is not particularly limited, and should be set as appropriate depending on conditions such as the size and the number of molded bodies G to be accommodated. It is preferable that it is a grade. If the plate thickness is less than 1 mm, the strength is insufficient and deformation increases during use, shortening the life of repeated use, and if the plate thickness exceeds 5 mm, the weight of the inner container 12 and thus the sintered container 10 becomes too heavy.

The compacts G can be arranged in direct contact with the bottom floor 121 of the inner container 12. However, in order to prevent the compact G from being welded to the bottom floor 121 in the sintering process, a laying made of, for example, a zirconia (ZrO ₂ ) ceramic sintered body or a silicon nitride (Si ₃ N ₄ ) ceramic sintered body is used. A compact (sintered body) G can be placed in the inner container 12 via the plate 13.

The sintering container 10 of the present embodiment has a double structure of an outer container 11 and an inner container 12. As described above, the main effect of the dual structure is to equalize the temperature inside the sintering container 10 during sintering, but the following effects can also be achieved.
In a Nd—Fe—B based sintered magnet, which is a typical example of a rare earth sintered magnet, a part of Nd is vaporized during the sintering process. In the Nd—Fe—B based sintered magnet, the sintering process is performed in a vacuum or in an inert gas atmosphere, but the vaporized Nd is preferably drifted inside the sintering vessel 10. Sintering does not proceed smoothly when the content of Nd vaporizes from the molded body G, but the Nd vaporized inside the sintering container 10 can prevent vaporization of Nd from the molded body G more than necessary. Moreover, it is because the influence from the inert gas in a furnace can be reduced. The sintering container 10 according to the present embodiment has a double structure. Therefore, the vaporized Nd is not easily discharged out of the sintering container 10 and does not hinder sintering. The Nd—Fe—B based sintered magnet will be described in detail later.

  Next, as also shown in Patent Document 4, the Nd—Fe—B based sintered magnet does not like that carbon (C) comes into contact with and reacts with the green body G during the sintering process. This is to avoid the consumption of Nd necessary for sintering due to the reaction between C and Nd. Therefore, Patent Document 4 proposes to prevent direct contact between the carbon component of the carbon fiber reinforced carbon composite material and the molded body G. On the other hand, in the present embodiment, the outer container 11 is composed of a carbon fiber reinforced carbon composite material, but the molded body G is accommodated in the inner container 12, and the molded body G is a carbon fiber reinforced carbon composite material. There is no direct contact with. Moreover, even if C is released from the carbon fiber reinforced carbon composite material during the sintering process, the inner container 12 is present around the molded body G, so that the released C and the molded body G are in contact with each other. Less likely.

In the present embodiment, a getter 14 may be disposed between the outer container 11 and the inner container 12. Here, the getter 14 refers to a member that captures impurities when the compact G is sintered. For example, if C which is disliked by sintering of the molded body G can be reacted with the getter 14, it is possible to prevent C from entering the inside of the inner container 12. The getter 14 captures mainly C, but is not limited to C, and can capture, for example, gas components that are impurities such as O, N, and the like existing in the sintering furnace 1.
As the getter 14, for example, a ceramic sintered body such as a zirconia (ZrO ₂ ) ceramic sintered body or a silicon nitride (Si ₃ N ₄ ) ceramic sintered body can be used. It is preferable to use a sintered body that is substantially the same as the rare earth sintered magnet. This is because the same gas component as the gas component that reacts in the sintering process of the green compact G, which is a sintered body, can be reliably captured by the getter 14. Here, “substantially the same” includes the case where the chemical compositions do not coincide with each other but the composition systems coincide. For example, in the case of an R (Nd) -Fe-B based sintered magnet, it is substantially included in the same manner as long as it is included in the composition range described later.

  In the sintered container 10 according to the present embodiment, preferably, the heat shield 15 is disposed between the molded body G and the side wall 122 of the inner container 12. The heat shield 15 is disposed so as to surround the molded body G. The heat shield 15 is heated by receiving radiant heat from the side wall 122 of the inner container 12. That is, the heat shield 15 is disposed in place of the molded body G placed on the outermost periphery where the heating temperature is highest in the conventional sintering method shown in FIGS. 4 and 5. Therefore, the deformation of the molded body G surrounded by the heat shield 15 is further suppressed.

  As long as the heat shield 15 fulfills the functions described above, there is no limitation on the material, size, and the like. Of course, since it is exposed to the sintering atmosphere, it is necessary that the material has heat resistance that can withstand it. For example, even when a metal material such as stainless steel or Mo is used as the heat shield 15, the effect of suppressing deformation can be obtained. A ceramic sintered body can also be used as the heat shield 15. However, the use of a gas that emits a gas that adversely affects the sintering during the sintering process should be avoided. Most preferably, the heat shield 15 surrounds the periphery of the molded body G as shown in FIGS. At this time, the heat shield 15 can be constructed as a frame-like integral, but it can also be divided into a plurality of pieces as shown in FIG.

The present invention can be applied to rare earth sintered magnets, specifically, sintered magnets represented by R-Fe-B (R is one or more rare earth elements).
The R—Fe—B based sintered magnet contains 25 to 37 wt% of rare earth element (R). Here, R has a concept including Y. Therefore, one or two of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Selected from more than species. R is typically Nd typically. If the amount of R is less than 25 wt%, the R ₂ Fe ₁₄ B phase, which is the main phase of the R—Fe—B based sintered magnet, is not sufficiently generated, and α-Fe having soft magnetism is precipitated and retained. The magnetic force is significantly reduced. On the other hand, when R exceeds 37 wt%, the volume ratio of the R ₂ Fe ₁₄ B phase, which is the main phase, decreases, and the residual magnetic flux density decreases. Further, R reacts with oxygen, the amount of oxygen contained increases, and accordingly, the R-rich phase effective for the generation of coercive force decreases, leading to a decrease in coercive force. Therefore, the amount of R is set to 25 to 37 wt%. A desirable amount of R is 28 to 35 wt%.

Moreover, the R—Fe—B based sintered magnet to which the present invention is applied contains 0.5 to 4.5 wt% of boron (B). When B is less than 0.5 wt%, a high coercive force cannot be obtained. On the other hand, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit of B is set to 4.5 wt%. A desirable amount of B is 0.5 to 1.5 wt%, and a more desirable amount of B is 0.8 to 1.2 wt%.
The R—Fe—B based sintered magnet to which the present invention is applied can contain Co of 5.0 wt% or less (excluding 0), desirably 0.1 to 3.0 wt%. Co forms the same phase as Fe, but is effective in improving the Curie temperature and the corrosion resistance of the grain boundary phase.

  The R—Fe—B based sintered magnet to which the present invention is applied allows the inclusion of other elements. For example, elements such as Al, Cu, Zr, Ti, Bi, Sn, Ga, Nb, Ta, Si, V, Ag, and Ge can be appropriately contained. On the other hand, it is desirable to reduce impurity elements such as oxygen, nitrogen, and carbon as much as possible. Needless to say, the present invention can be applied not only to the above R—Fe—B based sintered magnets but also to other rare earth sintered magnets such as Sm—Co based magnets.

The R—Fe—B based sintered magnet is usually produced through basic steps of production of a raw material alloy, pulverization of the raw material alloy, forming of the pulverized powder in a magnetic field, and sintering of the formed body.
The raw material alloy can be produced by a strip casting method or other known melting methods in a vacuum or an inert gas, preferably in an Ar atmosphere. In the strip casting method, a molten metal obtained by melting a raw metal in a non-oxidizing atmosphere such as an Ar gas atmosphere is ejected onto the surface of a rotating roll. The melt rapidly cooled by the roll is rapidly solidified in the form of a thin plate or flakes (scales). This rapidly solidified alloy has a homogeneous structure with a crystal grain size of 1 to 50 μm. The raw material alloy can be obtained not only by the strip casting method but also by a melting method such as high frequency induction melting.

  The raw material alloy is subjected to a grinding process. The pulverization process includes a coarse pulverization process and a fine pulverization process. First, the raw material alloy is coarsely pulverized until the particle size becomes about several hundred μm. The coarse pulverization is desirably performed in an inert gas atmosphere using a stamp mill, a jaw crusher, a brown mill or the like. Prior to coarse pulverization, it is effective to perform pulverization by allowing hydrogen to be stored in the raw material alloy and then releasing it. This hydrogen pulverization can be regarded as coarse pulverization, and mechanical coarse pulverization can be omitted.

After the coarse pulverization process, the process proceeds to the fine pulverization process. A jet mill is mainly used for fine pulverization, and a coarsely pulverized powder having a particle size of about several hundreds of μm has an average particle size of 2 to 10, preferably 3 to 6 μm. The jet mill releases a high-pressure inert gas from a narrow nozzle to generate a high-speed gas flow, accelerates the coarsely pulverized powder with this high-speed gas flow, collides with the coarsely pulverized powder, and collides with the target or the container wall. It is a method of generating a collision and crushing.
By adding about 0.01 to 0.5 wt% of a lubricant containing an organic substance before and after pulverization or both, fine powder with high orientation can be obtained at the time of molding in the next magnetic field. In addition, when a lubricant is added before fine pulverization, fine powder having a desired particle diameter can be efficiently produced in the fine pulverization step. As this lubricant, fatty acid or a derivative of fatty acid, for example, stearic acid-based or oleic acid-based zinc stearate, calcium stearate, stearamide, oleamide, or the like can be used.

The fine powder obtained as described above is subjected to molding in a magnetic field. The forming in the magnetic field may be performed at a pressure of about 50 to 200 MPa (about 0.5 to ² ton / cm ² ) in a magnetic field of 800 to 1600 kA / m (about 10 to 20 kOe).

The molded body obtained above is then subjected to a sintering step. The sintering container 10 mentioned above is used for this sintering process.
In the sintering process, a heat treatment for removing the lubricant is performed in the temperature rising process. That is, the lubricant can be removed by maintaining the temperature at a predetermined temperature for a predetermined time in the temperature raising process up to the sintering temperature. The predetermined temperature is preferably 200 to 600 ° C. This is because if the temperature is lower than 200 ° C., the effect of removing the lubricant cannot be sufficiently obtained, while if the temperature exceeds 600 ° C., the effect is saturated. Here, holding in the temperature range of 200 to 600 ° C. is not limited to holding the molded body at a constant temperature in the temperature range, and the molded body is heated to any temperature in the temperature range for a predetermined time. It only has to be.

  If the holding time for removing the lubricant is short, the effect of removing the lubricant is insufficient, while if the holding time is too long, the effect of removing the lubricant is saturated. Therefore, the heat treatment holding time is preferably 0.5 to 10 hours, and more preferably 1 to 3 hours. This lubricant is one of the C generation sources in the sintering furnace 1.

The heat treatment for removing the lubricant can be performed in a vacuum or an inert gas atmosphere. Ar gas, H ₂ gas, or He gas can be used as the inert gas. The molded body that has been subjected to the lubricant removal treatment is heated to the sintering temperature. The sintering process is performed in a vacuum or an inert gas atmosphere, preferably in a vacuum. Sintering conditions need to be adjusted according to various conditions such as composition, pulverization method, difference in average particle size and particle size distribution, etc., but a dense sintered body can be maintained at a temperature of 1000 to 1100 ° C. for about 1 to 10 hours. Can be obtained.

Hereinafter, the present invention will be described based on specific examples.
An alloy having a thickness of 500 μm composed of 30.0 wt% Nd-2.0 wt% Dy-0.5 wt% Co-0.2 wt% Al-0.08 wt% Cu-1.0 wt% B-balance Fe is formed by strip casting. Produced. The obtained strip cast alloy was occluded with hydrogen at room temperature, and then subjected to hydrogen occlusion / dehydrogenation treatment for dehydrogenation at 700 ° C. The alloy that had been subjected to hydrogen storage / dehydrogenation treatment was finely pulverized by a jet mill until the average particle size became 5 μm. Prior to fine pulverization, 0.1 wt% of zinc stearate (C-containing composition) was added. The fine powder obtained by pulverization was molded into a predetermined shape in a magnetic field. The applied magnetic field is 1300 kA / m, the molding pressure is 98 MPa, and the size of the obtained molded body G is 40 mm wide, 100 mm long, and 10 mm thick.

Next, as shown in FIG.2 and FIG.3, the obtained molded object G was arranged in the sintering container 10 which consists of the outer container 11 and the inner container 12, and the sintering process was performed (Example).
The outer container 11 was made of a carbon fiber reinforced carbon composite material (hereinafter referred to as a C / C composite material) having a thickness of 4 mm for both the tray 11a and the lid 11b. The dimension of the bottom floor 111 of the outer container 11 is 300 × 400 mm.
The inner container 12 was made of a molybdenum plate material having a thickness of 1 mm for both the tray 12a and the lid 12b. The dimension of the bottom floor 121 of the inner container 12 is 280 × 380 mm.

A total of 60 compacts G were arranged in the sintered container 10 (inner container 12) having the above specifications. The compact G was placed vertically.
As an example, an example in which the sintering process is performed without arranging the getter 14 and the heat shield 15 (Example 1), the getter 14 is disposed between the outer container 11 and the inner container 12, and the sintering process is performed. In the example (Example 2), the getter 14 is disposed between the outer container 11 and the inner container 12, and the heat shield 15 having substantially the same height as the molded body G is disposed on the outer periphery of the molded body G. Three types of examples (Example 3) for carrying out the sintering treatment were used. The getter 14 is a sintered body piece having a composition of 30.0 wt% Nd-2.0 wt% Dy-0.5 wt% Co-0.2 wt% Al-0.08 wt% Cu-1.0 wt% B-balance Fe. Was used. As the heat shield 15, a steel plate made of JIS SUS430 was processed into a frame shape having a thickness of 5 mm and a height of 100 mm.

  As a comparative example, the outer container 11 and the inner container 12 are both made of a C / C composite material (Comparative Example 1), and the outer container 11 and the inner container 12 are both made of a molybdenum plate (Comparative Example 2). Sintering was performed in the container. The specifications of the outer container 11 and the inner container 12 were in accordance with the example, and the getter 14 and the heat shield 15 were not provided.

  After the sintered container 10 in which the compacts G were arranged was placed in the sintering furnace 1 as shown in FIG. 1, the inside of the furnace was heated to perform vacuum sintering. Note that the heating conditions of the sintering furnace 1 were the same in both the examples and the comparative examples. In each example and each comparative example, the two sintering containers 10 were subjected to a sintering process. The sintering condition is to hold at a temperature of 1050 ° C. for 4 hours. In addition, the temperature of the molded object G placed in the center part and outermost periphery of the sintering container 10 was measured at 400 degreeC (the temperature of the said outermost periphery) of the temperature rising process. As a result, in Examples 1 to 3 and Comparative Example 1, the temperature difference between the central portion and the outermost periphery was 15 ° C. or less, and in Comparative Example 2, the temperature difference between the center and the outermost periphery was 80 ° C. In Comparative Example 1, the temperature increase time to 400 ° C. took 0.5 hours more than Examples 1-3. After the sintering treatment, an aging treatment (900 ° C. × 1 hour, 550 ° C. × 1 hour) was performed to obtain a sintered magnet.

  After completion of the sintering treatment, the amount of deformation of the sintered body (sintered magnet) S is measured by the method shown in FIG. 6, and when the amount of deformation is 0.2 mm or more, it is considered that the deformation has occurred, The number of ligations S was counted. The results are shown in Table 1. As shown in Table 1, it can be seen that in Examples 1 to 3, the number of deformed sintered bodies S is reduced, which contributes to improvement in yield.

  Next, the coercive force (HcJ) of the sintered magnet was measured. The measurement was performed on the five sintered magnets placed at the center and the outermost periphery of each sintering vessel 10 in both Examples and Comparative Examples, and the average value was obtained. The results are shown in Table 2. In any of the examples and comparative examples, the coercive force (HcJ) is lower in the sintered magnet placed on the outermost periphery than in the sintered magnet placed in the center.

It is a figure which shows a mode that the sintering container was arrange | positioned in the sintering furnace. It is a top view which shows a mode that the molded object was placed in the sintering container in this Embodiment. It is a partial expanded sectional view which shows a mode that the molded object was placed in the sintering container in this Embodiment. It is a top view which shows a mode that the molded object was placed in the conventional sintering container. It is AA arrow sectional drawing of FIG. 4 which shows a mode that the molded object was put in the conventional sintering container. In an Example, it is a figure which shows the measuring method of the deformation | transformation amount for specifying the presence or absence of a deformation | transformation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Sintering furnace, 10 ... Sintering container, 11 ... Outer container, 12 ... Inner container, 13 ... Laying board, 14 ... Getter, 15 ... Heat shield, G ... Molded object

Claims (4)

The molded article in a sintering vessel consisting of an alloy powder having a predetermined composition while multiple sequences, a method for producing a rare earth sintered magnet is sintered by heating from the outside of the sintered vessel,
The sintering vessel is
An outer container;
An inner container disposed inside the outer container and containing the molded body,
The method of manufacturing a rare earth sintered magnet, wherein the outer container has a thermal conductivity smaller than that of the inner container. The outer container is composed of a carbon fiber reinforced carbon composite;
The method for manufacturing a rare earth sintered magnet according to claim 1, wherein the inner container is made of a refractory metal.   The method for producing a rare earth sintered magnet according to claim 1, wherein a getter is disposed between the outer container and the inner container.   The method for producing a rare earth sintered magnet according to claim 3, wherein the getter is composed of a sintered body substantially the same as the rare earth sintered magnet.

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