JP5501833B2 - R-T-B permanent magnet - Google Patents

Description

  The present invention relates to an R-T-B (wherein R is one or more rare earth elements, T is one or more transition metal elements in which Fe, Fe and Co are essential) based sintered magnets. In particular, the present invention relates to an R-T-B permanent magnet having high magnetization characteristics.

  Among rare earth magnets, RTB-based sintered magnets are used in various electric devices because they have excellent magnetic properties and Nd, which is the main component, is abundant and relatively inexpensive. . Until now, research and development have been mainly conducted for improving the magnetic properties of the RTB-based sintered magnet, specifically, the residual magnetic flux density, coercive force or maximum energy product. However, recently, research and development focusing on magnetizing characteristics have been conducted. The RTB-based sintered magnet requires a higher magnetizing magnetic field than the ferrite magnet. For example, when a ring-shaped RTB-based sintered magnet is used as a rotor of a motor, the ring-shaped RTB-based sintered magnet is incorporated after the RTB-based sintered magnet is incorporated into the motor. Magnetization may be performed using a motor coil wound around a magnet. When the motor is small, the coil wire diameter becomes thin to obtain a predetermined number of turns, and a large current cannot be passed. Therefore, sufficient attachment to the R-T-B system sintered magnet is possible. A magnetic field cannot be applied. Therefore, the RTB-based sintered magnet used for the above-described applications is required to have as high a magnetization characteristic as possible with a low magnetization magnetic field.

For example, in Japanese Patent Laid-Open No. 2002-356701 (Patent Document 1), the average composition of the main phase is (LR _1-x HR _x ) ₂ T as an RTB-based sintered magnet having excellent magnetization characteristics. ₁₄ A (T is Fe or a mixture of Fe and at least one transition metal element other than Fe, A is boron or a mixture of boron and carbon, LR is at least one light rare earth element, and HR is heavy rare earth A rare earth alloy sintered body represented by at least one element, 0 <x <1, and having a composition represented by (LR _1-p HR _p ) ₂ T14A (0 ≦ p <x) And a rare earth alloy containing a plurality of crystal grains each having at least one of a main phase having a composition represented by (LR _1-q HR _q ) ₂ T ₁₄ A (x <q ≦ 1) A sintered body is disclosed.

  Japanese Patent Laid-Open No. 2003-217918 (Patent Document 2) describes, for the purpose of improving the magnetizing characteristics, in weight%, R (R is at least one kind of rare earth element including Y, and Nd occupies R). Is 25-35%, B: 0.8-1.5%, M (Ti, Cr, Ga, Mn, Co, Ni, Cu, Zn, Nb, Al if necessary) At least one kind): 8% or less, and the balance T (Fe or Fe and Co), and inevitable impurities, and Fe phase with FeACo1-A of 80 at% or more in a size of 0.01 to 300 μm In the rare earth sintered magnet having a crystal structure remaining in the sintered body, the magnetization rate Br (0.2 MA / m) / Br (2.0 MA / m) evaluated by the residual magnetic flux density is 59% or more, Magnetization rate Φ (0.3 A / m) / Φ (discloses that 4.0 MA / m) is 4% or more.

JP 2002-356701 A JP 2003-217918 A

  According to the technique disclosed in Patent Document 1, the magnetization characteristics can be improved without deteriorating the magnetic characteristics. However, a magnetizing magnetic field of about 0.8 MA / m (10 kOe) is necessary to obtain a magnetizing ratio of about 50%, and it is desirable to obtain a magnetizing ratio of about 50% with a lower magnetizing field. In addition, the magnetization rate Br (0.2 MA / m) / Br (2.0 MA / m) evaluated by the residual magnetic flux density in Patent Document 2 is 59% or more, and the magnetization rate Φ (0.3 MA / m) evaluated by the flux. When the value of m) / Φ (4.0 MA / m) is 4% or more, it cannot be said that the magnetization characteristics are good.

  On the other hand, according to the study by the present inventors, the R-T-B type sintered magnet that can obtain a higher magnetization rate with a low magnetic field has a gentle magnetization characteristic curve that represents the fluctuation of the magnetization rate due to the magnetization magnetic field. It tends to show an inclination. That is, since the magnetization characteristic curve is gentle, a larger magnetizing magnetic field is required to reach a magnetization rate near 100%.

  The present invention has been made on the basis of such a technical problem, and obtains a higher magnetization rate with a low magnetization magnetic field, and further increases the magnetization rate until reaching a magnetization rate of around 100%, for example, about 85%. It is an object of the present invention to provide an R-T-B permanent magnet having a quick rise.

In order to achieve the above object, an R-T-B system permanent magnet according to claim 1 of the present application includes R ₂ T ₁₄ B crystal grains (where R is one or more rare earth elements, and T is Fe or Fe). And one or more transition metal elements essential for Co. The same shall apply hereinafter.), R: 25 wt% to 35 wt%, B: 0.5 wt% to 4 wt%, Al and Cu 0.02 wt% to 0.6 wt% of 1 type or 2 types, 0.02 wt% to 1.5 wt% of 1 type or 2 types of Zr, Nb and Hf, Co: 0.5 wt% to 5 wt% or less, A step of pulverizing a magnet raw material into magnet powder, wherein the R ₂ T ₁₄ B crystal grains have an average particle size of 10 μm or less, and the pulverized magnet. following structural formula powder M- _{(OR) x} (wherein, M is Al, Cu, and at least one of r, Nb, Hf, and Co. R is an alkyl group having 2 to 6 carbon atoms, which may be linear or branched, and x is an arbitrary integer. Forming a molded body by molding the magnet powder having the organometallic compound attached to the particle surface, and a step of attaching the organometallic compound to the particle surface of the magnet powder A step of calcining the magnet powder with the organometallic compound attached to the particle surface before or after molding and before sintering in a hydrogen atmosphere ; and sintering the molded body; It is manufactured by.

  An R-T-B system permanent magnet according to claim 2 is an R-T-B system permanent magnet according to claim 1, wherein an effective magnetic field of 400 kA / m (where Pc (permeance coefficient) is 2) , Effective magnetic field = applied magnetic field−demagnetizing field) applied to the total flux f1, 600 kA / m applied effective flux f2, 2000 kA / m applied effective magnetic flux Assuming that f3, the magnetization rate a (= f1 / f3 × 100) is 35% or more, and the magnetization rate b (= f2 / f3 × 100) is 85% or more.

  Furthermore, the RTB-based permanent magnet according to claim 3 is the RTB-based permanent magnet according to any one of claims 1 to 3, wherein the sintered body is made of Bi and Ga. 1 type or 2 types are contained 0.01wt%-0.2wt%, It is characterized by the above-mentioned.

According to the RTB-based permanent magnet according to claim 1 having the above-described configuration, a higher magnetization rate is obtained with a low magnetization magnetic field, and until a magnetization rate in the vicinity of 100%, for example, about 85% is reached. , The rise of the magnetization rate becomes faster.
Further, by adding an organometallic compound containing at least one of Al, Cu, Zr, Nb, Hb, and Co to the magnet powder, Al, Cu, Zr, Nb, Hf, or Co contained in the organometallic compound is added. Efficiently uneven distribution at the grain boundaries of the magnet. As a result, the amount of Al, Cu, Zr, Nb, Hf, or Co used can be reduced, the residual magnetic flux density can be prevented from lowering, and effects such as coercivity improvement and grain boundary phase homogenization by each element can be fully achieved. It becomes possible to do. Further, decarbonization can be easily performed as compared with the case where other organometallic compounds are added, and there is no possibility that the magnet characteristics are deteriorated by the carbon contained in the sintered magnet. The whole can be sintered precisely.

  According to the R-T-B system permanent magnet according to claim 2, the magnetization rate in a low magnetic field of about 400 kA / m (5.1 kOe) is improved and 600 kA / m (7. An RTB-based sintered magnet having an improved magnetization rate in a magnetization magnetic field of 6 kOe) or more is provided. Such an RTB-based sintered magnet having excellent magnetization characteristics can reduce the width of the neutral zone when used in a multipolar magnetized magnet. A motor using such a ring magnet can maintain high rotational performance. In addition, a magnet with a high magnetization rate has a high cost and high magnetic properties as a material, but there are cases where a total flux actually generated is larger than a magnet with a low magnetization rate. Therefore, the present invention can realize a predetermined total flux with a low-cost magnet. Alternatively, the size of the magnet can be reduced.

  Furthermore, according to the R-T-B permanent magnet according to claim 3, the sintered body contains 0.01 wt% to 0.2 wt% of one or two of Bi and Ga. It becomes possible to improve.

1 is an overall view showing a permanent magnet according to the present invention. It is the schematic diagram which expanded and showed the vicinity of the grain boundary of the permanent magnet which concerns on this invention. It is explanatory drawing which showed the manufacturing process in the 1st manufacturing method of the permanent magnet which concerns on this invention. It is explanatory drawing which showed the manufacturing process in the 2nd manufacturing method of the permanent magnet which concerns on this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of a permanent magnet and a method for producing a permanent magnet according to the present invention will be described in detail with reference to the drawings.

[Configuration of permanent magnet]
First, the configuration of the permanent magnet 1 according to the present invention will be described. FIG. 1 is an overall view showing a permanent magnet 1 according to the present invention. 1 has a cylindrical shape, the shape of the permanent magnet 1 varies depending on the shape of the cavity used for molding.
An R-T-B magnet is used as the permanent magnet 1 according to the present invention. Further, as shown in FIG. 2, the RTB-based sintered magnet according to the present invention has R ₂ T ₁₄ B crystal grains (where R is one or more rare earth elements, and T is Fe or Fe and Co). 1 or more of transition metal elements mainly composed of). In addition to the main phase 11, a grain boundary phase 12 is included. The grain boundary phase 12 has an R content greater than that of the main phase 11.

Further, the RTB-based sintered magnet of the present invention has 1 to ₂ R ₂ T ₁₄ B crystal grains (hereinafter sometimes simply referred to as crystal grains) having a grain size D of 15 μm or more in the sintered body. It is desirable to exist 8%. As will be described later, if the crystal grains having a grain size D of 15 μm or more in the sintered body are less than 1%, the magnetization rate cannot be improved. In addition, when the crystal grains having a grain size D of 15 μm or more exist in the sintered body in excess of 8%, a high magnetization can be obtained, but the coercive force is significantly lowered. Therefore, in the present invention, it is desirable that 1 to 8%, preferably 2 to 7%, more preferably 3 to 6% of crystal grains having a grain size D of 15 μm or more exist.

In the present invention, the reason why excellent magnetization characteristics can be obtained by the presence of relatively coarse crystal grains having a grain size D of 15 μm or more is not clear. However, it can be understood that such a coarse crystal grain is easier to rotate the magnetic domain, and the rotation of the magnetic domain of the coarse grain induces the rotation of the magnetic domain of the surrounding fine grains, so that the magnetization characteristics are improved.
This invention does not ask | require the method of obtaining the sintered compact in which the crystal grain which has the particle size D of 15 micrometers or more exists 1-8%. It is possible to obtain a sintered body in which 1 to 8% of crystal grains having a particle diameter D of 15 μm or more are present by manipulating the particle size distribution and sintering conditions of the finely pulverized powder subjected to molding in a magnetic field. It is.

In the RTB-based sintered magnet of the present invention, the average particle size of the R ₂ T ₁₄ B crystal grains is 10 μm or less. This is because when the average particle size exceeds 10 μm, the coercive force is significantly reduced. However, in the present invention, since the crystal grains having a grain size D of 15 μm or more are intentionally present, it is advantageous to set the average grain size of the grains within a range of 10 μm or less. Therefore, in this invention, it is preferable to make the average particle diameter of a crystal grain into the range of 6-9 micrometers. However, even if the average grain size of the crystal grains is outside the range of 6 to 9 μm, it has a high effect as described later.

Next, a preferable chemical composition of the RTB-based sintered magnet of the present invention will be described. This chemical composition is that of the main phase 11 and the grain boundary phase 12 as a whole.
The RTB-based sintered magnet of the present invention contains 25 to 35 wt% of R. If the amount of R is less than 25 wt%, the generation of R ₂ T ₁₄ B crystal grains that will be the main phase 11 of the R—T—B system sintered magnet is not sufficient. For this reason, α-Fe or the like having soft magnetism is precipitated, and the coercive force is remarkably lowered. On the other hand, when the amount of R exceeds 35 wt%, the volume ratio of the R ₂ T ₁₄ B crystal grains constituting the main phase 11 decreases, and the residual magnetic flux density decreases. On the other hand, when the amount of R exceeds 35 wt%, R reacts with oxygen, and the amount of oxygen contained increases, and as a result, the R-rich phase effective for the generation of coercive force decreases and the coercive force decreases. Therefore, the amount of R is set to 25 to 35 wt%. A desirable amount of R is 26 to 33 wt%, and a more desirable amount of R is 27 to 32 wt%.

  When Dy and / or Tb is included as R, the sum of Dy and / or Tb and other R is set to 25 to 35 wt%. And in this range, it is preferable that the quantity of Dy and / or Tb shall be 0.1-8 wt%. The amount of Dy and / or Tb is desirably determined within the above range depending on which of the residual magnetic flux density and the coercive force is important. That is, when it is desired to obtain a high residual magnetic flux density, the amount of Dy and / or Tb is set to 0.1 to 3.5 wt%. When a high coercive force is desired to be obtained, the amount of Dy and / or Tb is set to 3.5. It is desirable to set it to -8 wt%.

  The RTB-based sintered magnet of the present invention contains 0.5 to 4 wt% of boron (B). When B is less than 0.5 wt%, a high coercive force cannot be obtained. However, when B exceeds 4 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit is 4 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 RTB-based sintered magnet of the present invention uses Co as an essential element, but its amount is 0.5 to 5 wt%. Co is effective in improving the Curie temperature and the corrosion resistance. In order to obtain this effect, it is preferably 0.5 wt% or more. Moreover, it has the effect that the aging treatment temperature range from which a high coercive force is obtained is expanded by adding together with Cu. However, excessive addition causes a decrease in coercive force and increases the cost, so the upper limit is made 5 wt%. The desirable Co content is 0.5-3 wt%, and the more desirable Co content is 0.8-2.5 wt%.

  The RTB-based sintered magnet of the present invention contains one or two of Al and Cu in a range of 0.02 to 0.6 wt%. By including one or two of Al and Cu in this range, it is possible to increase the coercive force, increase the corrosion resistance, and improve the temperature characteristics of the obtained RTB-based sintered magnet. In the case of adding Al, a desirable amount of Al is 0.03 to 0.3 wt%, and a more desirable amount of Al is 0.05 to 0.25 wt%. When Cu is added, the amount of Cu is 0.3 wt% or less (excluding 0), desirably 0.2 wt% or less (excluding 0), and the more desirable amount of Cu is 0 0.03 to 0.15 wt%. One or two kinds of Al and Cu do not adversely affect the effect of the present invention even if they are contained in either the main phase or the grain boundary phase.

  The RTB-based sintered magnet of the present invention contains 0.2 to 1.5 wt% of one or more of Zr, Nb, and Hf. When reducing the oxygen content in order to improve the magnetic properties of the RTB-based sintered magnet, Zr, Nb and Hf exhibit the effect of suppressing abnormal growth of crystal grains during the sintering process, Make the structure of the sintered body uniform and fine. Therefore, Zr, Nb, and Hf have a remarkable effect when the amount of oxygen is low. A desirable amount of one or more of Zr, Nb and Hf is 0.05 to 1.3 wt%, and a more desirable amount is 0.08 to 1.0 wt%.

  The RTB-based sintered magnet of the present invention allows the inclusion of other elements. For example, it is effective to contain one or two of Bi and Ga in order to improve the coercive force. One or two of Bi and Ga are preferably contained in the range of 0.01 to 0.2 wt%. A more preferable range of one or two of Bi and Ga is 0.03 to 0.15 wt%, and a more preferable range is 0.05 to 0.12 wt%. Even if Bi and Ga are contained in either the main phase or the grain boundary phase, they do not adversely affect the effects of the present invention.

  The RTB-based sintered magnet of the present invention preferably has an oxygen content of 4500 to 6000 ppm. When the amount of oxygen is large, the oxide phase, which is a nonmagnetic component, increases and the magnetic properties are deteriorated. On the other hand, when the amount of oxygen is lowered, the amount of the oxide phase having the function of suppressing the growth of crystal grains during the sintering process is reduced. As described above, the present invention expects the effect of improving the magnetization characteristics by generating relatively coarse crystal grains, and the amount of oxygen contained in the sintered body in consideration of the increase in the oxide phase. Is 4500 to 6000 ppm.

  In the present invention, addition of one or a plurality of elements among Al, Cu, Zr, Nb, Hf or Co (hereinafter referred to as Al, etc.) is performed before forming a pulverized magnet powder as described later. It is carried out by adding an organometallic compound containing etc. Specifically, by adding an organometallic compound containing Al or the like, Al or the like in the organometallic compound is uniformly attached to the particle surfaces of the magnet particles by wet dispersion. By sintering the magnet powder in this state, Al or the like in the organometallic compound uniformly adhered to the particle surface of the magnet particles is efficiently unevenly distributed at the grain boundary of the main phase 11, that is, the grain boundary phase 12. The

Further, in the present invention, M- (OR) _x (wherein, M includes at least one of Al, Cu, Zr, Nb, Hf, and Co. R is a C 2-6 carbon atom, as described later). Any of alkyl groups, which may be linear or branched, and x is an arbitrary integer.) An organometallic compound containing Al or the like (for example, copper ethoxide, copper isopropoxide, aluminum isopropoxy) (D) is added to an organic solvent and mixed with the magnet powder in a wet state. Thereby, an organometallic compound containing Al or the like can be dispersed in an organic solvent, and the organometallic compound containing Al or the like can be efficiently attached to the particle surfaces of the magnet particles.

Here, M- (OR) _x (wherein M includes at least one of Al, Cu, Zr, Nb, Hf, and Co. R is any one of alkyl groups having 2 to 6 carbon atoms). A metal alkoxide is an organometallic compound that satisfies the structural formula: x may be linear or branched, and x is an arbitrary integer. The metal alkoxide is represented by a general formula M- (OR) _n (M: metal element, R: organic group, n: valence of metal or metalloid). Examples of the metal or metalloid forming the metal alkoxide include W, Mo, V, Nb, Hf, Ta, Ti, Zr, Ir, Fe, Co, Ni, Cu, Zn, Cd, Al, Ga, In, Ge, Sb, Y, lanthanide, etc. are mentioned. However, in the present invention, in particular, Al, Cu, Zr, Nb, Hf, and Co are used.

  The type of alkoxide is not particularly limited, and examples thereof include methoxide, ethoxide, propoxide, isopropoxide, butoxide, alkoxide having 4 or more carbon atoms, and the like. However, in the present invention, those having a low molecular weight are used for the purpose of suppressing residual coal by low-temperature decomposition as described later. Further, since methoxide having 1 carbon is easily decomposed and difficult to handle, it is particularly preferable to use ethoxide, methoxide, isopropoxide, propoxide, butoxide, etc., which are alkoxides having 2 to 6 carbon atoms.

[Magnetic properties of permanent magnets]
In the present invention, when Pc (permeance coefficient) is 2, an effective magnetic field of 400 kA / m (however, effective magnetic field = applied magnetic field−demagnetizing field) is applied, the total flux is f1, and an effective magnetic field of 600 kA / m is applied. When the total flux when f2 and an effective magnetic field of 2000 kA / m are applied is f3, the magnetization rate a (= f1 / f3 × 100) is 35% or more and the magnetization rate b (= f2 / f) f3 × 100) is 85% or more. Furthermore, the RTB-based sintered magnet of the present invention has a magnetization rate c (= f4 / f3 × 100) of 95% or more when the total flux when an effective magnetic field of 790 kA / m is applied is f4. The magnetization rate is extremely high. Note that Pc in the present invention is determined based on FIG. 5-4 on page 146 of “sintered magnet” by Yoshio Tsuji and Kenji Ohashi (Morikita Publishing). The magnetization rate was measured as follows. A magnet to be evaluated was sandwiched between pole pieces to form a closed magnetic circuit, and then an electric current was passed through the electromagnet for magnetization. In this case, the applied magnetic field = effective magnetic field. After magnetization, the total flux was measured with a flux meter.

  Here, regarding the magnetization characteristics, as described above, it is ideal that the magnetic field has a larger magnetization rate in a low magnetic field and that the magnetization rate rises steeply. However, conventionally, a low coercive force type R-T-B type sintered magnet having a coercive force (HcJ) of 1600 kA / m or less has not been easy to satisfy both. However, according to the present invention, the magnetization a (= f1 / f3 × 100) is 35% or more, the magnetization b (= f2 / f3 × 100) is 85% or more, and the magnetization c (= f4 / f3). The present invention provides an RTB-based sintered magnet having a high magnetization rate in an unprecedented low magnetic field of × 100) of 95% or more and a rapid rise in magnetization rate.

Further, the present invention is preferably applied to a magnet subjected to multipolar magnetization.
The magnets magnetized with multiple poles include radial or polar anisotropic ring magnets used for motors, rectangular parallelepiped magnets used for driving pickups of devices such as CDs and DVDs, and VCM (Voice Coil Motors). ) Fan-shaped magnet. These multipolar magnets have a plurality of N · S polarities.

  When the RTB-based sintered magnet of the present invention is applied to the above multipolar magnetized magnet, the width of the neutral zone can be reduced. Therefore, the total flux amount is increased. For example, if used for a motor, the characteristics of the motor can be improved. Here, the neutral zone refers to a region that is not magnetized by either N or S at the boundary where the polarity (N · S) is reversed when the magnet is magnetized. In particular, in a small-sized magnet or a magnet having a large number of poles, the ratio of the neutral zone increases. Therefore, the width of the neutral zone can be reduced by using the R-T-B sintered magnet having excellent magnetization characteristics according to the present invention for multipolar magnetization, and thus the characteristics of the motor in which the magnet is used can be reduced. Can be improved.

[Permanent magnet manufacturing method 1]
Next, the 1st manufacturing method of the permanent magnet 1 which concerns on this invention is demonstrated using FIG. FIG. 3 is an explanatory view showing a manufacturing process in the first manufacturing method of the permanent magnet 1 according to the present invention.

  First, it is composed of R-T-B (for example, Nd: 20.26 wt%, Pr: 9.06 wt%, B: 0.97 wt%, Fe: 69.71 wt%) satisfying the above-described composition ratio. Manufacture ingots. Further, a small amount of Dy or Tb may be included to improve the coercive force. Thereafter, the ingot is roughly pulverized to a size of about 200 μm by a stamp mill or a crusher. Alternatively, the ingot is melted, flakes are produced by strip casting, and coarsely pulverized by hydrogen crushing.

  Subsequently, the coarsely pulverized magnet powder is either (a) in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas having substantially 0% oxygen content, or (b) having an oxygen content of 0.0001. Finely pulverized by a jet mill 41 in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, and He gas of ˜0.5%, and a predetermined size (for example, the average grain size of sintered crystals is 6 to 9 μm) A fine powder having an average particle size of The oxygen concentration of substantially 0% is not limited to the case where the oxygen concentration is completely 0%, but may contain oxygen in such an amount that a very small amount of oxide film is formed on the surface of the fine powder. Means good.

Meanwhile, an organometallic compound solution to be added to the fine powder finely pulverized by the jet mill 41 is prepared. Here, an organometallic compound containing at least one of Al, Cu, Zr, Nb, Hf, and Co is previously added to the organometallic compound solution and dissolved. The organometallic compound to be dissolved is M- (OR) _x (wherein M includes at least one of Al, Cu, Zr, Nb, Hf, and Co. R is an alkyl having 2 to 6 carbon atoms. An organometallic compound (for example, copper ethoxide, copper isopropoxide, aluminum isopropoxide, etc.) corresponding to any of the groups, which may be linear or branched, and x is an arbitrary integer. . The amount of the organometallic compound to be dissolved is not particularly limited, but the content of Al, Cu, Zr, Nb, Hf or Co in the sintered magnet is within the above-described range (for example, Co is 0.5 to 3 wt. %, Preferably 0.8 to 2.5 wt%, Al is 0.03 to 0.3 wt%, preferably 0.05 to 0.25 wt%, Cu is 0.3 wt% or less (however, 0 2), preferably 0.2 wt% or less (excluding 0), more preferably 0.03 to 0.15 wt%, Zr, Nb and Hf are 0.05 to 1.3 wt%. , Preferably 0.08 to 1.0 wt%).

  Subsequently, the organometallic compound solution is added to the fine powder classified by the jet mill 41. Thereby, the slurry 42 in which the fine powder of the magnet raw material and the organometallic compound solution are mixed is generated. The addition of the organometallic compound solution is performed in an atmosphere made of an inert gas such as nitrogen gas, Ar gas, or He gas.

  Thereafter, the produced slurry 42 is dried in advance by vacuum drying or the like before molding, and the dried magnet powder 43 is taken out. Thereafter, the dried magnet powder is compacted into a predetermined shape by the molding device 50. There are two types of compacting: a dry method in which the dried fine powder is filled into the cavity, and a wet method in which the powder is filled into the cavity after slurrying with a solvent or the like. In the present invention, the dry method is used. Illustrate. Further, the organometallic compound solution can be volatilized in the firing stage after molding.

As shown in FIG. 3, the molding apparatus 50 includes a cylindrical mold 51, a lower punch 52 that slides up and down with respect to the mold 51, and an upper punch 53 that also slides up and down with respect to the mold 51. And a space surrounded by them constitutes the cavity 54.
The molding apparatus 50 has a pair of magnetic field generating coils 55 and 56 disposed above and below the cavity 54, and applies magnetic field lines to the magnet powder 43 filled in the cavity 54. The forming in the magnetic field may be performed at a pressure of about 0.3 to 3.0 ton / cm ² (30 to 300 MPa) in a magnetic field of about 12 to 20 kOe (960 to 1600 kA / m). The applied magnetic field may be a pulsed magnetic field in addition to the static magnetic field.

And when compacting, first, the dried magnet powder 43 is filled into the cavity 54. Thereafter, the lower punch 52 and the upper punch 53 are driven, and pressure is applied in the direction of the arrow 61 to the magnetic powder 43 filled in the cavity 54 to perform molding. Simultaneously with the pressurization, a pulse magnetic field is applied to the magnetic powder 43 filled in the cavity 54 by the magnetic field generating coils 55 and 56 in the direction of the arrow 62 parallel to the pressurization direction. Thereby orienting the magnetic field in the desired direction. Note that the direction in which the magnetic field is oriented needs to be determined in consideration of the magnetic field direction required for the permanent magnet 1 formed from the magnet powder 43.
Further, when using the wet method, the slurry may be injected while applying a magnetic field to the cavity 54, and wet molding may be performed by applying a magnetic field stronger than the initial magnetic field during or after the injection. Further, the magnetic field generating coils 55 and 56 may be arranged so that the application direction is perpendicular to the pressing direction.

  Next, the compact 71 formed by compacting is held in hydrogen by holding it in a hydrogen atmosphere at 200 ° C. to 900 ° C., more preferably 400 ° C. to 900 ° C. (eg 600 ° C.) for several hours (eg 5 hours). Perform calcination. The amount of hydrogen supplied during calcination is 5 L / min. In the calcination treatment in hydrogen, so-called decarbonization is performed in which the organometallic compound is thermally decomposed to reduce the amount of carbon in the calcined body. Further, the calcination treatment in hydrogen is performed under the condition that the carbon content in the calcined body is 1000 ppm or less, more preferably 500 ppm or less. Accordingly, the entire permanent magnet 1 can be densely sintered by the subsequent sintering process, and the residual magnetic flux density and coercive force are not reduced.

Here, the molded body 71 calcined by the above-described calcining treatment in hydrogen has a problem that NdH ₃ exists and is easily combined with oxygen. However, in the first manufacturing method, the molded body 71 is preliminarily hydrogenated. Since it moves to the below-mentioned vacuum baking without making it contact with external air after baking, a dehydrogenation process becomes unnecessary. During the firing, hydrogen in the molded body is released.

Then, the sintering process which sinters the molded object 71 calcined by the calcination process in hydrogen is performed. In the sintering process, the temperature is raised to about 800 ° C. to 1180 ° C. at a predetermined rate of temperature rise and held for about 2 hours. During this time, vacuum firing is performed, but the degree of vacuum is preferably 10 ⁻⁴ Torr or less. Thereafter, it is cooled and heat-treated again at 600 ° C. for 2 hours. And the permanent magnet 1 is manufactured as a result of sintering.

[Permanent magnet manufacturing method 2]
Next, the 2nd manufacturing method which is another manufacturing method of the permanent magnet 1 which concerns on this invention is demonstrated using FIG. FIG. 4 is an explanatory view showing a manufacturing process in the second manufacturing method of the permanent magnet 1 according to the present invention.

  The process until the slurry 42 is generated is the same as the manufacturing process in the first manufacturing method already described with reference to FIG.

  First, the produced slurry 42 is dried in advance by vacuum drying or the like before molding, and the dried magnet powder 43 is taken out. Thereafter, the dried magnet powder 43 is calcined in hydrogen by holding it in a hydrogen atmosphere at 200 ° C. to 900 ° C., more preferably 400 ° C. to 900 ° C. (eg 600 ° C.) for several hours (eg 5 hours). The amount of hydrogen supplied during calcination is 5 L / min. In the calcination treatment in hydrogen, so-called decarbonization is performed in which the organometallic compound is thermally decomposed to reduce the amount of carbon in the calcined body. Further, the calcination treatment in hydrogen is performed under the condition that the carbon content in the calcined body is 1000 ppm or less, more preferably 500 ppm or less. Accordingly, the entire permanent magnet 1 can be densely sintered by the subsequent sintering process, and the residual magnetic flux density and coercive force are not reduced.

  Next, dehydrogenation treatment is performed by holding the powder-like calcined body 82 calcined by calcination in hydrogen at 200 to 600 ° C., more preferably at 400 to 600 ° C. for 1 to 3 hours in a vacuum atmosphere. I do. The degree of vacuum is preferably 0.1 Torr or less.

Here, the calcined body 82 calcined by the above-described calcining process in hydrogen has a problem that NdH ₃ exists and is easily combined with oxygen.
Stage Therefore, the dehydrogenation process, NdH ₃ calcined body of 82 produced by calcination process in hydrogen (activity Univ), NdH ₃ (activity Univ) → NdH ₂ to (activity small) Thus, the activity of the calcined body 82 activated by the treatment during the hydrogen calcination is lowered. Thereby, even when the calcined body 82 calcined by the calcining process in hydrogen is moved to the atmosphere after that, Nd is prevented from being combined with oxygen, and the residual magnetic flux density and coercive force are reduced. There is no reduction.

  Thereafter, the powder-like calcined body 82 subjected to the dehydrogenation treatment is compacted into a predetermined shape by the molding apparatus 50. The details of the molding apparatus 50 are the same as the manufacturing steps in the first manufacturing method already described with reference to FIG.

Thereafter, a sintering process for sintering the formed calcined body 82 is performed. In the sintering process, the temperature is raised to about 800 ° C. to 1180 ° C. at a predetermined rate of temperature rise and held for about 2 hours. During this time, vacuum firing is performed, but the degree of vacuum is preferably 10 ⁻⁴ Torr or less. Thereafter, it is cooled and heat-treated again at 600 ° C. for 2 hours. And the permanent magnet 1 is manufactured as a result of sintering.

In the second manufacturing method described above, since the powdered magnet particles are calcined in hydrogen, the first manufacturing method in which the magnet particles after molding are calcined in hydrogen are used. In comparison, there is an advantage that the pyrolysis of the organometallic compound can be more easily performed on the entire magnet particle. That is, it becomes possible to more reliably reduce the amount of carbon in the calcined body as compared with the first manufacturing method.
On the other hand, in the first manufacturing method, the compact 71 does not come into contact with the outside air after hydrogen calcination, and moves to vacuum firing described later, so that a dehydrogenation step is unnecessary. Therefore, the manufacturing process can be simplified as compared with the second manufacturing method. However, also in the second manufacturing method, the dehydrogenation step is not necessary when the firing is performed without contact with the outside air after the hydrogen calcination.

As described above, in the permanent magnet 1 according to the present embodiment, a higher magnetization rate is obtained with a lower magnetization magnetic field as compared with the conventional one, and moreover, until reaching a magnetization rate in the vicinity of 100%, for example, about 85%. The rise of the magnetization rate becomes faster.
In addition, when Pc (permeance coefficient) is 2, when an effective magnetic field of 400 kA / m (however, effective magnetic field = applied magnetic field−demagnetizing field) is applied, the total flux is f1, when an effective magnetic field of 600 kA / m is applied. If the total flux is f2 and the total flux when an effective magnetic field of 2000 kA / m is applied is f3, the magnetization rate a (= f1 / f3 × 100) is 35% or more and the magnetization rate b (= f2 / f3 ×). 100) is 85% or more, the magnetization rate at a magnetization field as low as about 400 kA / m (5.1 kOe) is improved and the magnetization rate at a magnetization field of 600 kA / m (7.6 kOe) or more. Further, an R-T-B system sintered magnet with improved performance is provided. Such an RTB-based sintered magnet having excellent magnetization characteristics can reduce the width of the neutral zone when used in a multipolar magnetized magnet. A motor using such a ring magnet can maintain high rotational performance. In addition, a magnet with a high magnetization rate has a high cost and high magnetic properties as a material, but there are cases where a total flux actually generated is larger than a magnet with a low magnetization rate. Therefore, the present invention can realize a predetermined total flux with a low-cost magnet. Alternatively, the size of the magnet can be reduced.
Furthermore, since the sintered body contains 0.01 wt% to 0.2 wt% of one or two of Bi and Ga, the coercive force can be improved.
In the manufacturing method of the permanent magnet 1, M- (OR) _x (wherein M is Al, Cu, Zr, Nb, Hf, Co, etc.) with respect to the fine powder of the pulverized RTB-based magnet. At least one of them, R is an alkyl group having 2 to 6 carbon atoms, which may be linear or branched, and x is an arbitrary integer.) Then, the organometallic compound solution is added to uniformly adhere the organometallic compound to the particle surface of the magnet. Thereafter, the green compact is subjected to calcination treatment in hydrogen by holding it in a hydrogen atmosphere at 200 ° C. to 900 ° C. for several hours. Then, the permanent magnet 1 is manufactured by baking at 800 to 1180 degreeC. Thereby, Al, Cu, Zr, Nb, Hf, or Co contained in the organometallic compound can be efficiently unevenly distributed at the grain boundaries of the magnet. As a result, the amount of Al, Cu, Zr, Nb, Hf, or Co used can be reduced, the residual magnetic flux density can be prevented from lowering, and effects such as coercivity improvement and grain boundary phase homogenization by each element can be fully achieved. It becomes possible to do. Further, decarbonization can be easily performed as compared with the case where other organometallic compounds are added, and there is no possibility that the magnet characteristics are deteriorated by the carbon contained in the sintered magnet. The whole can be sintered precisely.
In addition, a magnet to which an organometallic compound is added is calcined in a hydrogen atmosphere before sintering, so that the organometallic compound is thermally decomposed and carbon contained in the magnet particles is preliminarily burned out (the amount of carbon is reduced). The carbide is hardly formed in the sintering process. As a result, it is possible to sinter the entire magnet densely without generating voids between the main phase and the grain boundary phase of the sintered magnet, and to prevent the coercive force from being lowered. . Further, αFe is not precipitated in the main phase of the magnet after sintering, and the magnet characteristics are not greatly deteriorated.
In particular, in the second manufacturing method, since the powdered magnet particles are calcined, the pyrolysis of the organometallic compound is performed in comparison with the case of calcining the molded magnet particles. This can be done more easily for the whole particle. That is, the amount of carbon in the calcined body can be reduced more reliably. Further, by performing the dehydrogenation treatment after the calcination treatment, the activity of the calcined body activated by the calcination treatment can be reduced. As a result, the magnet particles are prevented from being combined with oxygen thereafter, and the residual magnetic flux density and coercive force are not reduced.

In addition, this invention is not limited to the said Example, Of course, various improvement and deformation | transformation are possible within the range which does not deviate from the summary of this invention.
Moreover, the pulverization conditions, kneading conditions, calcination conditions, sintering conditions, etc. of the magnet powder are not limited to the conditions described in the above examples.
Moreover, you may abbreviate | omit about a calcination process in hydrogen and a dehydrogenation process.

In the present invention, the average grain size of the crystal grains is in the range of 6 to 9 μm, but the average grain size may be in a smaller range. For example, the average particle size may be in the range of 0.1 to 5.0 μm. Further, even when _{the R} 2 _{T 14} B crystal grains having 15μm or more particle size D in the sintered body does not exist 1-8%, the present invention has a high effect.

In the above-described manufacturing method, for Al, Cu, Zr, Nb, Hf, and Co, M- (OR) _x (wherein M is one of Al, Cu, Zr, Nb, Hf, and Co) And R is any one of an alkyl group having 2 to 6 carbon atoms, which may be linear or branched, and x is an arbitrary integer.) However, some of the components may be included in the ingot in advance.

1 Permanent magnet 11 Main phase 12 Grain boundary phase

Claims (3)

R ₂ T ₁₄ B crystal grains (provided that R is one or more rare earth elements, T is one or more transition metal elements essential for Fe, Fe, and Co; the same shall apply hereinafter). It has a main phase, R: 25 wt% to 35 wt%, B: 0.5 wt% to 4 wt%, one or two of Al and Cu, 0.02 wt% to 0.6 wt%, Zr, Nb and Hf 1 It consists of a sintered body having a composition of 0.02 wt% to 1.5 wt%, Co: 0.5 wt% to 5 wt% or less of the seed or two or more species, and the balance substantially consisting of Fe,
The R ₂ T ₁₄ B crystal grains have an average grain size of 10 μm or less;
Crushing magnet raw material into magnet powder;
The pulverized magnet powder has the following structural formula M- (OR) _x
(In the formula, M includes at least one of Al, Cu, Zr, Nb, Hf, and Co. R is an alkyl group having 2 to 6 carbon atoms, and may be linear or branched. X Is an arbitrary integer.)
A step of attaching the organometallic compound to the particle surface of the magnet powder by adding an organometallic compound represented by:
Forming the molded body by molding the magnet powder having the organometallic compound attached to the particle surface;
A step of calcining the magnet powder having the organometallic compound attached to the particle surface before or after molding and before sintering in a hydrogen atmosphere; and
An RTB permanent magnet manufactured by the step of sintering the molded body.   When the effective magnetic field of 400 kA / m (where effective magnetic field = applied magnetic field−demagnetizing field) is applied at a Pc (permeance coefficient) of 2, the total flux when the effective magnetic field of f1 and 600 kA / m is applied. F2 and a total flux when an effective magnetic field of 2000 kA / m is applied is f3, the magnetization a (= f1 / f3 × 100) is 35% or more and the magnetization b (= f2 / f3 × 100) The R-T-B type permanent magnet according to claim 1, wherein the ratio is 85% or more. The RTB-based permanent magnet according to claim 1 or 2, wherein the sintered body contains 0.01 wt% to 0.2 wt% of one or two of Bi and Ga.

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