JP2010098080A - Method of manufacturing r-t-b system sintered magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problems: integrally bonding the materials having mutually different compositions by sintering without the use of an adhesive agent deforms the processed goods in the sintering step to require an extra machining for the predetermined dimension, lowering production yield, or causes cracks among the materials having the different compositions. <P>SOLUTION: A method of manufacturing an R-T-B (R: rare metal, B: boron, T: mainly Fe) system sintered magnet includes the steps of: preparing a first raw material alloy powder including relatively low concentration of heavy rare earth element R<SB>H</SB>or including no heavy rare earth element R<SB>H</SB>, and a second raw material alloy powder including relatively high concentration of heavy rare earth element R<SB>H</SB>; respectively filling the first raw material alloy powder and the second raw material alloy powder to the predetermined space of cavities formed by molds; obtaining a composite compact comprising a first compact part of the first raw material alloy powder and a second compact part of the second raw material alloy powder; and forming a sintered magnet with the first compact part and the second compact part combined by sintering the composite compact. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing an RTB-based sintered magnet that is suitably used for motors mounted on automobiles and the like.

An R-T-B-based sintered magnet (R is a rare earth element, B is boron, and T is mainly Fe) having the Nd ₂ Fe ₁₄ B type compound as the main phase has the highest performance among permanent magnets. It is known as a magnet, and is used in various motors such as hard disk drive VCM (voice coil motor) and hybrid vehicle mounted motors, home appliances, and the like. When the RTB-based sintered magnet is used in various devices such as a motor, it is required to have excellent heat resistance and high coercive force in order to cope with a use environment at a high temperature.

In order to improve the coercive force of the R-T-B based sintered magnet, a rare earth element R is blended with a light rare earth element _{RL as} well as a predetermined amount of heavy rare earth element _RH as a raw material, and a melted alloy is used. It has been broken. According to this method, since the light rare earth element _RL of the R ₂ Fe ₁₄ B phase, which is the main phase as the rare earth element R, is substituted with the heavy rare earth element _RH , the magnetocrystalline anisotropy of the R ₂ Fe ₁₄ B phase ( The essential physical quantity that determines the coercivity is improved.

However, the magnetic moment of the light rare earth element _RL in the R ₂ Fe ₁₄ B phase is in the same direction as the magnetic moment of Fe, whereas the magnetic moment of the heavy rare earth element _RH is opposite to the magnetic moment of Fe. Therefore, the residual magnetic flux density _Br decreases as the substitution amount of the heavy rare earth element _{RH with} respect to the light rare earth element _RL increases.

The magnets used in the motor or the like, high residual magnetic flux density B _r, and coercive force H _cJ of the area exposed to high heat and large demagnetizing field is high is required.

The prior art, there is possible to use an adhesive-integrated magnet with residual magnetic flux density B _r is higher magnet and the coercivity H _cJ high magnet to various devices such as a motor. However, when the adhesive-integrated magnet is used in various devices such as a motor, the upper limit temperature for use is limited by the low heat resistance of the adhesive. In addition, when an adhesive-integrated magnet is manufactured, extra work time is required, and productivity is deteriorated. Furthermore, when there are many adhesives used for joining, a magnetically discontinuous layer will be formed with an adhesive.

A method of forming an integral magnet without using an adhesive has also been considered (Patent Document 1, Patent Document 2). In Patent Document 1, each of which have the same basic composition, and one of the materials having a high residual magnetic flux density B _r in comparison to other, the other having a high coercive force H _cJ compared to one of the material the A field composite permanent magnet in which a material and a material are integrally fixed by sintering is disclosed.

  In Patent Document 2, a plurality of field permanent magnets having a circular arc cross section constituting a plurality of permanent magnets of a DC machine, the inner circumferential surface vicinity portion around the inner end face edge portion on the demagnetizing field side of each field permanent magnet. Only a permanent magnet having a coercive force higher than that of the main body permanent magnet is disclosed.

  However, none of these documents is directed to ferrite magnets, and did not satisfy the demand for miniaturization and high performance of motors and the like. In addition, since materials of different compositions are joined together by sintering, they are deformed in the sintering process and cracked from the joint due to the difference in shrinkage of each material as the temperature rises during use. There was a problem.

Japanese Patent Laid-Open No. 57-148656 Japanese Utility Model Publication No.59-117281

  When the adhesive-integrated magnet is used in various devices such as a motor, there is a problem that the upper limit temperature of use is limited by the heat resistance of the adhesive. On the other hand, if an attempt is made to integrally bond materials having different compositions without using an adhesive, the deformation may occur in the sintering process. For this reason, processing to a predetermined dimension is required, and the yield may be reduced or the materials having different compositions may be broken.

The present invention has been made to solve the above problems, it is an object without using an adhesive, the residual magnetic flux density B _r in a predetermined position of the magnet is high area and coercivity H _cJ An object of the present invention is to provide a method for producing an RTB-based sintered magnet in which a high region is firmly bonded and integrated, and deformation during sintering is small.

The method for producing the RTB-based sintered magnet contains both a light rare earth element R _L (at least one of Nd and Pr) and a heavy rare earth element R _H (at least one of Dy and Tb), and Nd ₂ An RTB-based sintered magnet (R is a rare earth element, B is boron, and T is mainly Fe) having a Fe ₁₄ B-type crystal as a main phase, comprising a heavy rare earth element _RH Preparing a first raw material alloy powder having a relatively low or no concentration and a second raw material alloy powder having a relatively high concentration of the heavy rare earth element _RH , and the first raw material alloy powder and the second raw material alloy A filling step of filling powder into predetermined spaces of a cavity formed by a mold, and a composite comprising a first molded body portion of the first raw material alloy powder and a second molded body portion of the second raw material alloy powder Obtaining the molded body; and A step of obtaining a sintered magnet in which the first molded body part and the second molded body part are combined by sintering a composite molded body, is there.

  In a preferred embodiment, a cavity comprising a space in which the first raw material alloy powder and the second raw material alloy powder can be filled in the filling step is formed, and one of the first raw material alloy powder or the second raw material alloy powder is placed in the cavity. And filling the upper surface of the raw material alloy powder to be filled with the other of the first raw material alloy powder or the second raw material alloy powder.

  In a preferred embodiment, in the filling step, one of the first raw material alloy powder or the second raw material alloy powder is filled into a cavity formed by a space that can be filled with the one raw material alloy powder, and the upper surface of the filled powder is horizontally disposed. After that, a space in which the other of the first raw material alloy powder or the second raw material alloy powder can be filled on the upper surface of the raw material alloy powder in the cavity, and the second filling of the other raw material alloy powder is filled in the space. And a process.

  In a preferred embodiment, the filling step includes arranging a partition in the cavity, dividing the cavity, and filling the first raw material alloy powder and the second raw material alloy powder into separate divided cavities.

  In a preferred embodiment, the partition disposed in the cavity in the filling step includes removing the composite molded body after filling before obtaining.

  In a preferred embodiment, at least the first raw material alloy powder of the first raw material alloy powder and the second raw material alloy powder is selected from the group consisting of shrinkage relaxation agents M (C, Al, Co, Ni, Cu, and Sn). The concentration of the shrinkage relaxation agent M in the first raw material alloy powder is higher than the concentration of the shrinkage relaxation agent M in the second raw material alloy powder.

According to the present invention, it is possible to realize a strong bond without using an adhesive for the heavy rare-earth element R _H is at the junction between the high regions and the coercive force H _cJ regions of high residual magnetic flux density B _r is diffused.

Furthermore, by varying the process parameters such as the concentration of the shrinkage relaxation agent M depending on the concentration difference of the heavy rare-earth element R _H of the remanence B _r of high area and a high coercivity H _cJ region, the heavy rare-earth element R It becomes possible to suppress the deformation of the sintered magnet in the sintering process caused by the difference in _H concentration.

  With reference to FIG. 1 and FIG. 2, the structural example of the RTB type | system | group sintered magnet by this invention is demonstrated. FIG. 1 is a cross-sectional view showing a configuration example of an RTB-based sintered magnet 1, and FIG. 2 schematically shows a structure inside the magnet of FIG.

R-T-B based sintered magnet 1 shown, the amount of heavy rare-earth element R _H in comparison with the region second region consists of the composition the amount of heavy rare-earth element R _H is often 2 (high coercivity portion) is small composition And a region 3 (high _Br portion) made of the above-described structure are integrally joined via a joint portion 4.

In the present specification, for the sake of simplicity, the first region where the concentration of the heavy rare earth element _RH is relatively low or zero is referred to as a “high residual magnetic flux density portion” or “high _Br portion”, The second region having a relatively high _RH concentration may be referred to as a “high coercivity portion” or a “high H _cJ portion”. The main feature of the present invention is that the high coercive force portion and the high residual magnetic flux density portion are firmly bonded by molding and sintering, and bonding with an adhesive is not performed as in the prior art.

Magnets tissues as indicated in Figure 2, the main phase 5 consisting of a heavy rare-earth element _{R H} of the high amount the composition _Nd 2 _{Fe 14} B crystal, the heavy rare-earth element _{R H} of the small amount the composition _Nd 2 _{Fe 14} B crystal A main phase 6 comprising:

In the vicinity of the junction 4, the heavy rare earth element _{RH in the} region 2 and the light rare earth element _{RL in the} region 3 are diffused to each other, thereby realizing a strong bond. This heavy rare earth element _RH diffusion region (region Y in the figure) shows a tendency that the amount of heavy rare earth element _RH as a whole gradually decreases from region 2 to region 3, as shown in FIG. Further, the light rare earth element _RL shows a tendency opposite to that of _RH . The grain boundary phase 8 is a rare earth-rich phase.

  The RTB-based sintered magnet of the present invention can be manufactured, for example, by the following method.

In the method for producing an RTB-based sintered magnet of the present invention, a first raw material alloy powder and a second raw material alloy powder having different heavy rare earth element _RH contents are prepared.

[First material alloy]
The first raw material alloy used for the first raw material alloy powder includes a light rare earth element _{RL of} 16.0% by mass or more and 36.0% by mass or less, and a heavy rare earth element R _H (Dy and no less than 0% by mass and less than 15% by mass). Any one or both of Tb), 0.5% by mass to 2.0% by mass of B (boron), and the balance Fe and unavoidable impurities. Here, a part of Fe (50 atomic% or less) may be substituted with another transition metal element (for example, Co or Ni). In addition, this alloy has Al, Si, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb depending on various purposes. In addition, at least one additive element selected from the group consisting of Bi and Bi may be contained in an amount of about 0.01 to 1.0% by mass. The above-mentioned alloy can be suitably produced by rapidly cooling a molten raw material alloy by, for example, a strip casting method. Hereinafter, preparation of a rapidly solidified alloy by a strip casting method will be described.

  First, a raw material alloy having the above composition is melted by high-frequency melting in an argon atmosphere to form a molten raw material alloy. Next, after this molten metal is maintained at, for example, about 1350 ° C., it is rapidly cooled by a single roll method to obtain, for example, a flake-shaped alloy slab having a thickness of about 0.3 mm. The alloy slab thus produced is pulverized into flakes having a size of 1 to 10 mm, for example, before hydrogen pulverization in the next coarse pulverization step. In addition, the manufacturing method of the raw material alloy by a strip cast method is disclosed by US Patent 5,383,978 specification, for example.

[Second material alloy]
The second raw material alloy used for the second raw material alloy powder includes a light rare earth element _{RL of} 16.0% by mass to 35.0% by mass and a heavy rare earth element R of 0.5% by mass to 15.0% by mass. 1st raw material alloy except containing _H (one or both of Dy and Tb), B (boron) of 0.5 mass% or more and 2.0 mass% or less, remainder Fe and inevitable impurities The second raw material alloy is produced in the same manner as described above. Here, a part of Fe (50 atomic% or less) may be substituted with another transition metal element (for example, Co or Ni). In addition, this alloy has Al, Si, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb depending on various purposes. In addition, at least one additive element selected from the group consisting of Bi and Bi may be contained in an amount of about 0.01 to 1.0% by mass. Similarly to the first raw material alloy, the second raw material alloy is also preferably produced by a strip casting method.

  In the present invention, an embodiment using two kinds of raw material alloys, ie, a first raw material alloy and a second raw material alloy, has been described, but three or more kinds of raw material alloys may be used.

The difference between the first raw material alloy and the second raw material alloy is that the concentration of the heavy rare earth element _RH in the first raw material alloy is relatively lower than the concentration of the heavy rare earth element _RH in the second raw material alloy. The first raw material alloy may not contain the heavy rare earth element _RH .

[Coarse grinding process]
The coarse pulverization of the first raw material alloy and the second raw material alloy is performed by a hydrogen embrittlement method. This is a method of producing and cracking fine cracks in the alloy by utilizing the volume expansion accompanying hydrogen storage. In the alloy system of the present invention, the difference in hydrogen storage amount between the main phase and the R-rich phase, that is, Since the difference in volume change causes cracking, the probability of cracking at the grain boundary of the main phase increases, and the raw material alloy can be pulverized into a fine powder in the subsequent pulverization step.

  In the hydrogen embrittlement treatment, usually, after exposure to pressurized hydrogen at room temperature for a certain period of time, the temperature is raised to release excess hydrogen, followed by cooling. The coarse powder after hydrogen embrittlement treatment is very active because it contains a large number of cracks and the specific surface area is greatly increased, and the amount of oxygen increases significantly when handled in the atmosphere. It is desirable to handle in an inert gas such as nitrogen, Ar. Further, since a nitriding reaction may occur at a high temperature, an Ar atmosphere is preferable if the cost permits.

  By the hydrogen pulverization, the alloy slabs of the first raw material alloy and the second raw material alloy are pulverized to a size of about 0.1 mm to several mm, and the average particle diameter becomes 500 μm or less. After the hydrogen pulverization, the embrittled raw material alloy is preferably crushed more finely and cooled. When the raw material alloy is taken out in a relatively high temperature state, the cooling process time may be relatively shortened.

[Fine grinding process]
Next, fine pulverization is performed on the coarsely pulverized powder using, for example, a jet mill pulverizer. A cyclone classifier is connected to the jet mill crusher used in the present embodiment. The jet mill pulverizer is supplied with the coarsely pulverized powder coarsely pulverized in the coarse pulverization step, and pulverizes in the pulverizer. The powder pulverized in the pulverizer is collected in a collection container through a cyclone classifier. In this way, it is possible to obtain the first raw material alloy powder and the second raw material alloy powder, which are fine powders having a D50 of about 1 to 10 μm (typically 3 to 5 μm) as measured by the airflow dispersion type laser diffraction method. The pulverizer used for such fine pulverization is not limited to a jet mill, and may be an attritor or a ball mill. In grinding, a lubricant such as zinc stearate may be used as a grinding aid.

  Here, as the shrinkage relaxation agent M, at least one of C, Al, Co, Ni, Cu, and Sn (C is preferably contained in an amount of 50 ppm to 3000 ppm. In any of Al, Co, Ni, Cu, and Sn, 0. Is preferably mixed with the first raw material alloy powder and / or the second raw material alloy powder as a compound or metal powder. By mixing, it is possible to suppress deformation caused by a difference in shrinkage rate when a compact formed by compressing powders made of raw material alloys having different compositions is sintered. When the shrinkage relaxation agent M is added at the time of dissolving the raw material, the effect as a shrinkage relaxation agent is small.

[Filling and forming process of composite molded body]
Next, the first raw material alloy powder and the second raw material alloy powder are respectively filled in predetermined spaces of cavities formed by a mold made of a punch, a die, etc., and then the first raw material alloy powder A composite compact including one compact part and a second compact part of the second raw material alloy powder is obtained.

  In the present embodiment, for example, 0.3% by mass of a lubricant may be added to and mixed with the produced first raw material alloy powder and second raw material alloy powder in a rocking mixer, for example. Here, as the lubricant, a lubricant containing C such as zinc stearate can be used.

  Here, the powder made of the first raw material alloy produced by the above-described method is filled in the cavity formed by the mold, and further, the powder made of the second raw material alloy is filled in the same cavity. And molded in a static magnetic field of 0.4 MA / m to 1.6 MA / m. At that time, the cavity is formed by lowering the lower punch relatively to a depth sufficient to fill the total amount of the first raw material alloy powder and the second raw material alloy powder before filling, A method may be used in which one of the two raw material alloy powders is filled in the cavity, and then the other of the first raw material alloy powder or the second raw material alloy powder is filled thereon (FIG. 4).

After completion of filling of the first raw material alloy powder and the second raw material alloy powder, a composite formed body having a formed body density of about 3.5 to 4.8 g / cm ^{3 in} an orientation magnetic field using a known press device Good to get. If it is less than 3.5 g / cm ³ , handling after taking out the molded product becomes difficult, and if it exceeds 4.8 g / cm ³ , molding is performed at a high pressure and the orientation of the alloy powder is disturbed, so high characteristics cannot be obtained. There is a problem.

  As another embodiment, first, the lower punch is relatively pulled down to a depth sufficient to fill one of the first raw material alloy powder or the second raw material alloy powder, and the first raw material alloy powder or the second raw material alloy powder After filling one side and leveling the top surface of the filled raw material alloy powder, the first raw material alloy powder or the second raw material alloy is further filled on the top surface of the filled raw material alloy powder by relatively moving the lower punch. A method (FIG. 5) in which a space for filling the other powder is formed and filled may be used. By these methods, the first raw material alloy powder and the second raw material alloy powder can be laminated and integrated in the pressing direction.

After the filling of the first raw material alloy powder and the second raw material alloy powder is completed, the composite material is obtained by molding in an orientation magnetic field using a known press device. Here, it is good to shape | mold with a molded object density of about 3.5-4.8 g / cm < ³ >.

  Further, as another embodiment, the cavity is relatively pulled down to a depth sufficient to fill the total amount of the first raw material alloy powder and the second raw material alloy powder before filling, and the cavity is filled in the cavity before filling. A partition can be arranged in each of the above, and the cavities can be divided to fill the cavities with the first raw material alloy powder and the second raw material alloy powder. By these methods, the first raw material alloy powder and the second raw material alloy powder can be integrated in a direction orthogonal to the pressing direction. The partition disposed in the cavity is removed after the filling is completed and before the composite molded body is formed (FIG. 6).

After the filling of the first raw material alloy powder and the second raw material alloy is completed and the partition is removed, it is molded in an orientation magnetic field using a known press device to obtain a composite molded body. Here, it is good to shape | mold with a molded object density of about 3.5-4.8 g / cm < ³ >.

[Sintering process]
Next, the composite molded body is sintered to produce a sintered magnet in which the first molded body portion and the second molded body portion are combined. A step of holding the powder compact at a temperature in the range of 300 ° C. to 900 ° C. for 30 minutes to 120 minutes, and then firing at a temperature higher than the holding temperature (eg, 1000 ° C. to 1150 ° C.). It is preferable to sequentially perform the step of further proceeding with the linking. After sintering, an aging treatment (700 ° C. to 1000 ° C.) is performed as necessary.

The RTB-based sintered magnet manufactured in the present invention contains both a light rare earth element R _L (at least one of Nd and Pr) and a heavy rare earth element R _H (at least one of Dy and Tb). This is an RTB-based sintered magnet having an Nd ₂ Fe ₁₄ B-type crystal as a main phase. In this sintered magnet, a high residual magnetic flux density portion having a relatively low or no heavy rare earth element _RH concentration (content) and a high coercive force portion having a relatively high heavy rare earth element _RH concentration are formed. ing.

According to the present invention, by changing the filling order of the first raw material alloy and the second raw material alloy, it is possible to arrange a region containing a large amount of the heavy rare earth element _RH at an arbitrary position. FIG. 3 is a cross-sectional view showing a configuration example of an RTB-based sintered magnet of the present invention that can be formed by the above manufacturing method. The arrows in the figure indicate the magnetic field orientation direction.

A plate-shaped sintered magnet 11, the rare earth element R shown in FIG. 3, both end portions 12 consist region rich in heavy rare-earth element R _H, the central portion 13 is relatively small amount of heavy rare-earth element R _H, It consists of the area | region which contains many light rare earth elements _RL .

In the example shown in FIG. 3, the magnetic field orientation directions are common in a plurality of regions having different concentrations of the heavy rare earth element _RH .

According to the present invention, a small amount of the heavy rare earth element _RH is concentrated in a part of the whole magnet formed by molding and sintering, and a region _having a high coercive force _HcJ is selected. Can be formed. For this reason, since it is not necessary to add the heavy rare earth element _RH unnecessarily to the region of the sintered magnet where the demagnetizing field is small, the residual magnetic flux density _Br can be increased in that region. Moreover, since the adhesive is not used, the problem described in the prior art (the upper limit temperature of use is limited by the low heat resistance of the adhesive) can be avoided.

  Hereinafter, examples showing the effect of the method for producing an RTB-based sintered magnet according to the present invention will be described.

Example 1
First, the composition of Nd: 26.0, Pr: 5.0, B: 1.00, Co: 0.90, Cu: 0.1, Al: 0.20, the balance: Fe (unit: mass%). The ingot of the first raw material alloy blended so as to have was melted by the above-mentioned strip casting method and cooled to prepare an alloy flake having a thickness of 0.2 to 0.3 mm.

  Nd: 16.5, Pr: 5.0, Dy: 10.00, B: 1.00, Co: 0.90, Cu: 0.1, Al: 0.20, balance: Fe (unit: An alloy flake having a thickness of 0.2 to 0.3 mm was produced by similarly melting and cooling the ingot of the second raw material alloy so as to have a composition of (mass%) by a strip casting method.

  Next, each of these alloy flakes was filled in a container and inserted into a hydrogen treatment apparatus. Then, by filling the hydrogen treatment apparatus with a hydrogen gas atmosphere at a pressure of 500 kPa, the alloy flakes were occluded with hydrogen at room temperature, then heated to 500 ° C. in a vacuum and held for 2 hours to release part of the hydrogen. I let you. By performing such a hydrogen treatment, the alloy flakes were embrittled and an irregular coarse powder having a size of about 0.15 to 0.2 mm was produced.

  After adding 0.05% by weight of zinc stearate as a grinding aid to each of the coarse powders produced by the above hydrogen treatment and mixing, each powder particle size is adjusted by carrying out a grinding process with a jet mill device. In either case, a fine powder of about 4 μm was produced. Then, 0.15 mass% lubricant (liquid fatty acid ester) was added as a powder lubricant to each finely pulverized powder.

Among the fine powders thus produced, the fine powder (first raw material alloy powder) made of the first raw material alloy is filled in the press device and arranged so that the upper surface of the powder is parallel to the punch surface. A fine powder (second raw material alloy powder) made of the second raw material alloy 2 is filled thereon so as to have a mass ratio of 1: 1, and a composite molding having a density of 4.2 g / cm ³ in an applied magnetic field of 1.5 T. The body was made. Then, the sintering process for 4 hours was performed at 1050 degreeC with the vacuum furnace.

  The press used in this example is a known perpendicular magnetic field forming apparatus (hereinafter also referred to as a transverse magnetic field press apparatus), and the produced sintered magnet is a powder as shown in the example of the sintered magnet in FIG. The stacking direction and the magnetic field application direction are orthogonal to each other. The same effect can be obtained even with a magnetic field press in which the pressing direction and the magnetic field application direction are parallel.

  The sintered body block thus produced was mechanically processed to obtain a sintered magnet having a thickness of 3 mm × length 14 mm (magnetization direction) × width 8 mm (press direction).

Example 2
A composite molded body in which the powder lamination direction and the magnetic field application direction coincide with a known transverse magnetic field press apparatus is manufactured by the method shown in FIG. A magnet was produced.

  On the other hand, a sample of Comparative Example 1 was also produced.

Comparative Example 1
The first raw material alloy powder and the second raw material alloy powder are separately filled in a press device, and each of the compacts having a density of 4.2 g / cm ³ is produced in an applied magnetic field of 1.5 T. After sintering at 1040 ° C. for 4 hours to obtain two magnet sintered bodies, a sintered magnet joined with a two-component epoxy adhesive so that the magnetization orientation directions of the produced two magnet sintered bodies are aligned. A sintered magnet was produced under the same conditions as in Example 1 except that it was produced.

Comparative Example 2
Nd: 26.0, Pr: 5.0, Dy: <0.05, B: 1.0, Co: 0.90, Cu: 0.1, Al: 0.20, balance: Fe (unit is mass) %) Except that the sintered magnet was prepared using only the raw material alloy 3 blended so as to have the composition of the composition of Example 2).

  The samples of Examples 1 and 2 and Comparative Example 1 were heated in a constant temperature bath at 200 ° C. for 2 hours assuming use in a high temperature environment in various devices such as a motor. While there was no change before and after the high temperature holding, the adhesive part of the sample of Comparative Example 1 was peeled off.

  Three-point bending strength (measurement conditions span distance: 9 mm, crosshead speed: 1 mm / min, device name: LSC-1 / 30 manufactured by JT Toshi) was measured for the samples obtained in Examples 1 and 2 and Comparative Example 2. Then, Example 1 and Example 2 were compared based on the bending strength of Comparative Example 2 (300 MPa).

  The sintered magnets of Example 1 and Example 2 had a bending strength equivalent to that of Comparative Example 2.

Further, the Dy diffusion state of Example 1 was confirmed by EPMA mapping (measurement conditions: acceleration voltage: 15 kV, beam: current: 100 nA, beam irradiation time: 1 s / point, device name: Shimadzu EPMA-1610). From a high coercivity portion made of a second material alloy containing a large amount of heavy rare-earth element R _H as a street rare earth element R in FIG. 7, a high B that the amount of heavy rare-earth element R _H as the rare earth element R consisting of a relatively small first material alloy It was found that heavy rare earth element R _H (Dy here) was diffused in the _r portion. In addition, a tungsten metal is sandwiched as a mark so that the molded body joint before sintering can be seen.

In addition, the diffusion state of Dy of Example 1 was confirmed with an EPMA line profile (measurement conditions acceleration voltage: 15 kV, beam: current: 100 nA, beam irradiation time: 1 sec / point, device name: Shimadzu EPMA1610). Line profile, the high B _r unit amount of heavy rare-earth element R _H from a high coercivity portion formed of the second material alloy powder containing a large amount of heavy rare-earth element R _H as the rare earth element R is relatively small first material alloy powder Measured toward. To the high B _r unit earth element R _{H (here,} Dy) comprising a first material alloy powder from a high coercivity portion as formed of the second material alloy powder of FIG. 8 it was found to be diffused. Here, the represented line is a line obtained by subtracting the Dy values of the main phase, the grain boundary phase, and the triple point at intervals of 2 μm. Further, "Range" of the horizontal axis is the junction of the high coercivity portion made of a high B _r unit and the second material alloy consisting of first material alloy as a reference (0 .mu.m).

According to the manufacturing method according to the present invention described above, since a plurality of fine powders having different concentrations of heavy rare earth elements _RH are simultaneously sintered, the powders constituting each of these compacts are sintered together. In addition to bonding, the molded bodies are joined to each other. At this time, due to the difference in the concentration of the heavy rare earth element _RH , a difference occurs in the shrinkage amount of each molded body, so that the final sintered magnet formed by integrating a plurality of molded bodies is slightly deformed. There is a case.

  In order to further suppress the deformation of the sintered magnet, (1) Addition to the raw material alloy powder between the compact part for the high coercive force part and the compact part for the high Br part in the composite compact Amount of lubricant (shrinkage relaxation agent M (C)), amount of shrinkage relaxation agent M (at least one of Al, Co, Ni, Cu, and Sn), (2) powder of magnetic powder forming the compact Preferably, at least one process parameter of the particle size difference is changed.

  Hereinafter, an embodiment in which these process parameters are adjusted will be described.

  First, as shown in Table 1 below, three types of raw material alloy powders A, B, and C having different Dy concentrations were prepared.

  Table 1 and Table 2 below describe the composition of each of the raw material alloy powders A, B, and C, the density of the compact produced by compression molding, the shrinkage ratio during sintering, and the like. The pulverized particle size D50 of each powder was adjusted to 4.70 μm. Except for the matters described in Table 1 and Table 2, it was produced in the same manner as in Example 1. The “molding pressure” shown in Table 2 is a value obtained by dividing the total pressure applied to the molded body by the punch area in contact with the molded body. The compact density is a value obtained by dividing the value obtained by (single weight of the compact (actual value)) / (die hole area (design value)) by the height of the compact (actual value). The shrinkage rate during sintering is a value obtained in the magnetic field orientation direction (M direction) and the direction (K direction) perpendicular to both the M direction and the pressing direction (pressing direction). The shrinkage ratio is determined by measuring the distance between the opposing surfaces at the center of each surface of the molded body and the sintered body, and from the size of the corresponding part, ((dimension of the molded body−dimension of the sintered magnet) / value of the dimension of the molded body Is a value obtained by multiplying 100 by 100.

  The data shown in Table 2 are obtained separately for the compact and sintered body made of the raw material alloy powder A, the compact and sintered body made of the raw material alloy powder B, and the compact and sintered body made of the raw material alloy powder C, respectively. This is the value obtained.

In this example, 0.15% by mass of a lubricant (liquid fatty acid ester) was added to each raw material alloy powder, and compression molding was performed by applying a pressure (forming pressure) of 0.34 ton / cm ² to each. . The molding in this example is based on so-called right-angle magnetic field molding in which the pressing direction (pressing direction) and the magnetic field application direction are orthogonal to each other. The molded body thus obtained was sintered at 1040 ° C. for 4 hours. Table 2 It was found that the shrinkage varies depending on the Dy concentration of the raw material alloy powder.

  As shown in Table 3, sintered magnets were produced by changing various combinations of powders A, B, and C and additional conditions.

  Table 3 below shows Sample No. 1-1 to Sample No. About 4-4, the manufacturing conditions and the shape of the sintered magnet finally obtained are shown. In the same manner as in Example 1, these examples were produced in the order of “first filling → second filling → molding → sintering”.

The column “Combination” in Table 3 describes the type of powder initially filled in the cavity of the press device (left in the same column) and the type of powder subsequently filled in the cavity (right in the same column). . For example, sample No. In 1-1, the raw material alloy powder A is first supplied and the upper surface of the powder is adjusted to be parallel to the punch surface, and then the raw material alloy powder B is supplied to form 0.34 ton / cm ² . The composite was molded by compression with pressure.

  Sample No. “Additional conditions” for 2-1 include not only adding a standard value (0.15% by mass) of lubricant (liquid fatty acid ester) to the raw material alloy powder B but also adding 0.05% by mass of lubricant. (A total of 0.20% by mass of lubricant was added and 1000 ppm of C was contained in the molded body). Similarly, sample no. “Additional condition” regarding 2-2 is that not only the standard value (0.15 mass%) of the lubricant was added to the raw material alloy powder A but also 0.08 mass% of the lubricant was further added ( A total of 0.23% by mass of lubricant was added, and the molded body contained about 1100 ppm of C). Sample No. 2-1, sample no. In 2-2, the reason why the lubricant added to the first-stage alloy powder is relatively increased is that the Dy concentration of the first filled molded body portion in the integrated molded body is relatively low, Because it tends to shrink, the amount of lubricant added is relatively increased, and as a result, the density of the compact is increased even at the same molding pressure, thereby reducing the dimensional difference between the high residual magnetic flux density part and the high coercive force part during sintering. This is to reduce.

  Conversely, sample no. As an “additional condition” regarding 2-3, not only the standard value (0.15% by mass) of lubricant (liquid fatty acid ester) is added to the raw material alloy powder C but also 0.05% by mass of lubricant is added. Or a total of 0.20% by mass of lubricant was added. As an “additional condition” regarding 2-4, not only the standard value (0.15 mass%) of the lubricant is added to the raw material alloy powder C but also 0.08 mass% of the lubricant is further added (in total) 0.23 mass% lubricant was added), and the dimensional difference between the high residual magnetic flux density part and the high coercive force part during sintering further spreads, and cracking due to strain occurred during sintering. End up.

  Sample No. The “additional condition” regarding 3-1 is that 0.10 mass% Sn powder was added to the raw material alloy powder B as the shrinkage relaxation agent M. Similarly, sample no. The “additional condition” regarding 3-2 is that 0.19% by mass of Sn powder was added to the raw material alloy powder A as the shrinkage relaxation agent M. Sample No. 3-1, sample no. In 3-2, the reason why the shrinkage mitigating agent M is added to the first-stage alloy powder is that the Dy concentration in the first filled molded body portion in the integrated molded body is relatively low and shrinks. This is because the shrinkage relaxation agent M reduces the high residual magnetic flux density part and the high coercive force part during sintering.

  Conversely, sample no. As an “additional condition” for 3-3, 0.10% by mass of Sn powder as a shrinkage relaxation agent M is added to the raw material alloy powder C. As an “additional condition” regarding 3-4, when 0.19 mass% Sn powder is added to the raw material alloy powder C as the shrinkage relaxation agent M, a high residual magnetic flux density part and a high coercive force part during sintering As the dimensional difference increases, cracking due to strain occurs during sintering.

  Sample No. The “additional condition” regarding 4-1 is that the pulverized particle size D50 of the raw material alloy powder B is changed from the standard value (4.70 μm) to 4.80 μm. Similarly, sample no. The “additional condition” regarding 4-2 is that the pulverized particle size D50 of the raw material alloy powder A is changed from the standard value (4.70 μm) to 5.10 μm. Sample No. 4-1 and sample no. In 4-2, the reason why the pulverized particle size of the first-stage alloy powder is relatively large is that the Dy concentration in the first-stage portion in the integrated molded body is relatively low and easily contracts. This is because the shrinkage rate is reduced by increasing the particle size of the powder and, as a result, increasing the density of the molded body even at the same molding pressure. Process parameters not described in the “additional conditions” column were set to the same conditions for all samples.

  Conversely, sample no. As an “additional condition” regarding 4-3, the pulverized particle size D50 of the raw material alloy powder C is changed from the standard value (4.70 μm) to 4.80 μm. As an “additional condition” regarding 3-4, when the pulverized particle size D50 of the raw material alloy powder C is changed from the standard value (4.70 μm) to 5.10 μm, the high residual magnetic flux density portion and the high coercive force during sintering are further increased. As the dimensional difference with the part widens, cracking due to strain occurs during sintering.

The column of “shape” determination in Table 3 is based on the following dimensional ratio. Here, the size ratio, the sintered magnet, high B _r portion (portion derived from the first material alloy powder), (a portion from a second material alloy powder) high coercivity portion of each (in the plane center) the magnetic field orientation dimension is measured refers to a percentage of the size of the high coercivity portion size of the high B _r unit. The symbol “◎” indicates a dimension ratio of 99.0% or higher, the symbol “○” indicates a dimension ratio of 98.5% to 99.0%, the symbol “△” indicates a dimension ratio of 98.0% to 98.5%, and the symbol “×” indicates a dimension. It means that the ratio was 98.0% or less or cracking occurred. By adjusting the above process parameters, the dimensional ratio of regions having different Dy concentrations can be reduced, and as a result, deformation of the sintered magnet can be sufficiently suppressed.

From the results of Table 3, in order to suppress deformation of the sintered magnet, between the heavy rare-earth element R _H is no or relatively little first molded body and the heavy rare-earth element R _H is relatively large second molded body Thus, the lubricant to be added to the powder of the molded body is 0.05 mass% or more, and 0.10 mass for at least one of C, Al, Co, Ni, Cu, and Sn as the shrinkage relaxation agent M. It was found that it is preferable to add at least%.

From the results of Table 3, it was found that it is preferable to make the particle size of the first raw material alloy powder coarser than the particle size of the second raw material alloy powder in order to suppress deformation of the sintered magnet. When the shrinkage mitigating agent M is not used, it is preferable that the first raw material alloy powder and the second raw material alloy powder contain heavy rare earth elements _RH in order to suppress deformation of the sintered magnet. I understood.

According to the present invention, it is possible to provide a R-T-B based sintered magnet remanence B _r is high region and a high coercive force _HcJ region is present respectively without using an adhesive.

It is the schematic diagram showing the cross section of the sintered compact firmly integrated by laminating | stacking and sintering the some molded object from which a composition differs. It is a schematic diagram which shows typically the structure | tissue inside the magnet of FIG. It is a figure showing one Example of this invention. It is process drawing which shows the filling process of this invention. It is process drawing which shows the other filling process of this invention. It is process drawing which shows the other filling process of this invention. 2 is an EPMA mapping image of a cross section of the sintered body of Example 1. FIG. 2 is an EPMA line profile image of a cross section of the sintered body of Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 Integrated rare earth magnet sintered body 2,12 Area | region which consists of a composition containing many heavy rare earth elements _RH in an integrated rare earth magnet sintered body 3,13 Heavy rare earth elements in an integrated rare earth magnet sintered body Region composed of a composition not containing much _RH 4 Junction trace 5, 6, 7 Main phase 8 Grain boundary phase Y Region where heavy rare earth element _RH is diffused

Claims (6)

R-T-B containing both a light rare earth element R _L (at least one of Nd and Pr) and a heavy rare earth element R _H (at least one of Dy and Tb) and having an Nd ₂ Fe ₁₄ B type crystal as a main phase A production method of a sintered system magnet (R is a rare earth element, B is boron, T is mainly Fe),
Preparing a heavy rare-earth element R _H first material alloy powder density does not include relatively low or, and the second material alloy powder concentration is relatively high heavy rare-earth element R _H,
A filling step of filling the first raw material alloy powder and the second raw material alloy powder into predetermined spaces of a cavity formed by a mold,
Obtaining a composite compact comprising a first compact part of the first raw material alloy powder and a second compact part of the second raw material alloy powder;
Sintering the composite molded body to obtain a sintered magnet in which the first molded body portion and the second molded body portion are combined;
The manufacturing method of the RTB type | system | group sintered magnet containing this. In the filling step, a cavity including a space in which the first raw material alloy powder and the second raw material alloy powder can be filled is formed, and one of the first raw material alloy powder or the second raw material alloy powder is filled in the cavity. ,
The manufacturing method of the RTB type | system | group sintered magnet of Claim 1 including the process of filling the other of the said 1st raw material alloy powder or the 2nd raw material alloy powder in the said raw material alloy powder upper surface filled after that. In the filling step, after filling one of the first raw material alloy powder or the second raw material alloy powder into a cavity composed of a space where the one raw material alloy powder can be filled, and leveling the filled powder upper surface, Furthermore, a second filling step of forming a space capable of filling the other of the first raw material alloy powder or the second raw material alloy powder on the upper surface of the raw material alloy powder in the cavity, and filling the other raw material alloy powder in the space;
The manufacturing method of the RTB type | system | group sintered magnet of Claim 1 containing this.   2. The filling process according to claim 1, wherein the filling step includes partitioning the cavity, dividing the cavity, and filling the first raw material alloy powder and the second raw material alloy powder into separate divided cavities. Manufacturing method of RTB-based sintered magnet.   The manufacturing method of the RTB type | system | group sintered magnet of Claim 4 including removing the partition arrange | positioned in a cavity in the said filling process before forming a composite molded object after filling. The shrinkage reducing agent M (at least one selected from the group consisting of C, Al, Co, Ni, Cu, and Sn) is included in at least the first raw material alloy powder of the first raw material alloy powder and the second raw material alloy powder. Containing
The method for producing an RTB-based sintered magnet according to claim 1, wherein the concentration of the shrinkage relaxation agent M in the first raw material alloy powder is higher than the concentration of the shrinkage relaxation agent M in the second raw material alloy powder. .

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