JP2018164004A - Method for producing RTB-based sintered magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method in which unnecessary irregularities are not formed on the surface of an RTB-based sintered magnet after a heat treatment in which a heavy rare earth element RH is diffused from a magnet surface to the inside. SOLUTION: The method for producing an RTB-based sintered magnet of the present disclosure includes a step of preparing a particle size adjusting powder containing a powder of an alloy or compound of a heavy rare earth element RH, and an M oxide (M is Mg). , Al, Si, Ti, Cr, Mn, Fe, Co, Zr (one or more selected from the group) and a coating step of applying an adhesive to the coating region on the surface of the sintered magnet. The step of adhering the particle size adjusting powder to the coating region on the surface of the sintered magnet, the step of allowing the M oxide powder to exist on the surface of the sintered magnet together with the particle size adjusting powder, and the sintering temperature of the sintered magnet or less. It includes a diffusion step of diffusing the heavy rare earth element RH contained in the particle size adjusting powder from the surface of the sintered magnet to the inside by heat treatment at the above temperature. [Selection diagram] FIG. 1C

Description

  The present disclosure relates to a method for producing an R-T-B based sintered magnet (R is a rare earth element, T is Fe or Fe and Co, and B is boron).

  R-T-B system sintered magnets are known as the most powerful magnets among permanent magnets. Voice coil motors (VCM) for hard disk drives, motors for electric vehicles (EV, HV, PHV, etc.), industrial It is used in various motors such as equipment motors and home appliances.

The RTB-based sintered magnet is composed of a main phase mainly composed of an R ₂ T ₁₄ B compound and a grain boundary phase located at the grain boundary portion of the main phase. The main phase R ₂ T ₁₄ B compound has a high saturation magnetization and an anisotropic magnetic field, and forms the basis of the characteristics of the R—T—B system sintered magnet.

At a high temperature, the coercive force H _cJ (hereinafter sometimes simply referred to as “H _cJ ”) of the _RTB -based sintered magnet decreases, and irreversible thermal demagnetization occurs. Therefore, in particular, an _RTB -based sintered magnet used for an electric vehicle motor is required to have a high _HcJ .

In the RTB-based sintered magnet, a part of the light rare earth element RL (for example, Nd or Pr) contained in R in the R ₂ T ₁₄ B compound is a heavy rare earth element RH (for example, Dy or Tb). Substitution is known to improve _HcJ . As the substitution amount of RH increases, _HcJ improves.

However, when RL in the R ₂ T ₁₄ B compound is replaced with RH, the H _{cJ of the RTB} -based sintered magnet is improved, while the residual magnetic flux density B _r (hereinafter simply referred to as “B _r ”). There is). In particular, RH such as Tb and Dy has problems such as the supply is not stable and the price fluctuates greatly due to the small amount of resources and the limited production area. Yes. Therefore, in recent years, it has been demanded to improve _HcJ without using RH as much as possible.

On the other hand, so as not to reduce the B _r, to improve the H _cJ of the R-T-B based sintered magnets have been studied with less heavy rare-earth element RH. For example, fluoride or oxide of heavy rare earth element RH, or various metals M or M alloys, either individually or mixed, are present on the surface of the sintered magnet, and heat treatment is performed in that state, _thereby improving _HcJ . It has been proposed to diffuse the contributing heavy rare earth element RH into the magnet. For example, Patent Document 1 discloses a method in which powders of R oxide, R fluoride, and R oxyfluoride are brought into contact with the surface of an R-T-B system sintered magnet and subjected to heat treatment to diffuse them into the magnet. Is disclosed.

International Publication No. 2006/043348 International Publication No. 2015/163397

  Patent Document 1 discloses a method in which a mixed powder containing an RH compound powder is present on the entire magnet surface (the entire magnet surface) to perform heat treatment. According to a specific example of this method, a magnet is dipped in a slurry in which the above powder is dispersed in water or an organic solvent and pulled up (immersion pulling method). In the case of the immersion pulling method, hot air drying or natural drying is performed on the magnet pulled up from the slurry. Instead of immersing the magnet in the slurry, spraying the slurry onto the magnet is also disclosed (spray coating method).

In these methods, slurry can be applied to the entire surface of the magnet. For this reason, the heavy rare earth element RH can be introduced into the magnet from the entire surface of the magnet, and the _HcJ after the heat treatment can be greatly improved. However, in the immersion pulling method, the slurry is inevitably biased to the lower part of the magnet due to gravity. Further, in the spray coating method, the coating thickness at the end of the magnet increases due to surface tension. In either method, it is difficult to make the RH compound uniformly exist on the magnet surface.

When the coating layer is thinned using a slurry having a low viscosity, the unevenness of the coating layer thickness can be improved to some extent. However, since the amount of slurry applied is reduced, _HcJ after the heat treatment cannot be greatly improved. If application is performed a plurality of times in order to increase the amount of slurry applied, the production efficiency will be greatly reduced. In particular, when the spray coating method is employed, the slurry is also applied to the inner wall surface of the spray coating apparatus, and the utilization yield of the slurry is lowered. As a result, there is a problem in that the heavy rare earth element RH, which is a rare resource, is wasted.

  In the patent document 2, the present applicant discloses a method of performing a diffusion heat treatment in a state where the RLM alloy powder and the RH fluoride powder are present on the surface of the RTB-based sintered magnet. It is difficult to say that a method for causing these powders to uniformly exist on the surface of the RTB-based sintered magnet is well established.

In the present disclosure, when a layer of powder particles containing a heavy rare earth element RH is formed on the magnet surface in order to diffuse the heavy rare earth element RH into the RTB-based sintered magnet and improve _HcJ , these powders are used. Particles can be uniformly and efficiently applied to the surface of an R-T-B sintered magnet, and the heavy rare earth element RH can be diffused from the magnet surface into the interior to greatly improve _HcJ. The present invention also provides a production method with high production efficiency with less unnecessary irregularities on the surface of the RTB-based sintered magnet after diffusion heat treatment.

  In the exemplary embodiment, the manufacturing method of the RTB-based sintered magnet of the present disclosure prepares an RTB-based sintered magnet (R is a rare earth element, and T is Fe or Fe and Co). A step, a step of preparing a particle size adjusting powder formed from a powder of an alloy or compound of heavy rare earth element RH which is at least one of Dy and Tb, M oxide (M is Mg, Al, Si, Ti, Cr, A step of preparing a powder of one or more selected from the group consisting of Mn, Fe, Co, and Zr), a coating step of applying a pressure-sensitive adhesive to a coating region on the surface of the RTB-based sintered magnet, By adhering the particle size adjusting powder together with the M oxide powder to the application region on the surface of the R-T-B type sintered magnet coated with the pressure-sensitive adhesive, the R-T-B type sintered magnet Heavy rare earth element RH and M oxide are present on the surface And heat treating the RTB-based sintered magnet having the particle size-adjusted powder and the M oxide powder on the surface at a temperature lower than the sintering temperature of the RTB-based sintered magnet. And a diffusion step of diffusing the heavy rare earth element RH contained in the particle size adjusting powder from the surface of the RTB-based sintered magnet to the inside.

  In one embodiment, the step of causing the M oxide powder to be present on the surface of the R-T-B system sintered magnet together with the particle size-adjusting powder comprises: In this step, the M oxide powder is dispersed on the surface of the magnet.

  In one embodiment, the step of causing the M oxide powder to be present on the surface of the R-T-B system sintered magnet together with the particle size-adjusting powder comprises: In this step, the magnet is embedded in the M oxide powder.

  In another exemplary embodiment, the manufacturing method of the RTB-based sintered magnet of the present disclosure includes an RTB-based sintered magnet (R is a rare earth element, and T is Fe or Fe and Co). And a powder of an alloy or compound of heavy rare earth element RH which is at least one of Dy and Tb, and an M oxide (M is Mg, Al, Si, Ti, Cr, Mn, Fe, Co, Zr) A step of preparing a particle size-adjusted mixed powder formed from a powder of one or more selected from the group consisting of: a coating step of applying a pressure-sensitive adhesive to a coating region on the surface of the RTB-based sintered magnet; The particle size-adjusted mixed powder is applied to the surface of the RTB-based sintered magnet by attaching the particle size-adjusted mixed powder to the application region on the surface of the RTB-based sintered magnet coated with an adhesive. And the particle size-adjusted mixed powder is on the surface. The existing RTB-based sintered magnet is heat-treated at a temperature equal to or lower than the sintering temperature of the RTB-based sintered magnet, and the heavy rare earth element RH contained in the particle size adjusting powder is converted into the R- A diffusion step of diffusing inward from the surface of the TB sintered magnet.

  In one embodiment, the particle size adjusting powder or the particle size adjusting mixed powder is a powder of an RHM1M2 alloy (M1 and M2 may be one or more selected from Cu, Fe, Ga, Co, Ni, Al, and M1 = M2). Or an RLRHM1M2 alloy (RL is one or more selected from Nd and Pr).

  In one embodiment, the particle size adjusting powder or the particle size adjusting mixed powder is an RH compound (RH is one or more selected from Dy and Tb, and the RH compound is selected from RH fluoride, RH acid fluoride, and RH oxide). One or more powders).

  In one embodiment, the particle size adjustment powder or the particle size adjustment mixed powder is an RLM1M2 alloy (RL is one or more selected from Nd and Pr, and M1 and M2 are selected from Cu, Fe, Ga, Co, Ni, and Al. 1 type or more, M1 = M2 may be included).

  In one embodiment, the particle size adjusted powder or the particle size adjusted mixed powder is a particle size adjusted powder or a particle size adjusted mixed powder granulated together with a binder.

According to an embodiment of the present disclosure, a layer of powder particles containing heavy rare earth element RH is _added to _RTB in order to diffuse heavy rare earth element RH into the RTB-based sintered magnet and improve _HcJ. It can be uniformly and efficiently applied to the surface of the sintered system magnet. For this reason, it is possible to improve the _HcJ of the _RTB -based sintered magnet while reducing the consumption of the heavy rare earth element RH, which is a rare resource. Furthermore, since unnecessary irregularities on the magnet surface after the diffusion heat treatment are reduced, it is not necessary to flatten these irregularities, and the production efficiency is high.

2 is a cross-sectional view schematically showing a part of a prepared RTB-based sintered magnet 100. FIG. It is sectional drawing which shows typically a part of RTB type sintered magnet 100 in the state in which the adhesion layer 20 was formed in a part of magnet surface. It is sectional drawing which shows typically a part of RTB system sintered magnet 100 in the state to which the powder particle 30 which comprises a particle size adjustment powder was adhered. It is a figure which shows the photograph of the RTB type sintered magnet (left side) in which the knob-like thing did not generate | occur | produce, and the RTB type sintered magnet (right side) in which the knob-like thing generate | occur | produced.

An exemplary embodiment of a method for manufacturing an RTB-based sintered magnet according to the present disclosure is as follows:
(1) a step of preparing an R-T-B sintered magnet (R is a rare earth element, T is Fe or Fe and Co, and B is boron);
(2) Heavy rare earth element RH alloy or compound powder which is at least one of Dy and Tb, or heavy rare earth element RH compound powder and RLM1M2 alloy (RL is one or more selected from Nd and Pr, M1, M2 is a step of preparing a particle size-adjusting powder containing a powder of one or more selected from the group consisting of Cu, Fe, Ga, Co, Ni, and Al, M1 = M2 may be
(3) preparing a powder of M oxide (M is one or more selected from the group consisting of Mg, Al, Si, Ti, Cr, Mn, Fe, Co, Zr);
(4) Application process of applying an adhesive to the application region on the surface of the RTB-based sintered magnet,
(5) The particle size adjustment is applied to the surface of the R-T-B system sintered magnet by attaching the particle size-adjusting powder to the application region on the surface of the R-T-B system sintered magnet coated with an adhesive. Allowing the powder to exist,
(6) A step of causing the M oxide powder to exist on the surface of the RTB-based sintered magnet together with the particle size adjusting powder,
(7) Heat treating the RTB-based sintered magnet having the particle size-adjusted powder and the M oxide powder on the surface at a temperature lower than the sintering temperature of the RTB-based sintered magnet ( Diffusion heat treatment), a diffusion step of diffusing the heavy rare earth element RH contained in the particle size adjusting powder from the surface of the RTB-based sintered magnet to the inside;
including.

  In addition, the said process does not necessarily need to perform each process separately, and several processes may be performed simultaneously. Details will be described later.

  FIG. 1A is a cross-sectional view schematically showing a part of an RTB-based sintered magnet 100 that can be used in the method for manufacturing an RTB-based sintered magnet according to the present disclosure. In the drawing, an upper surface 100a and side surfaces 100b and 100c of the RTB-based sintered magnet 100 are shown. The shape and size of the RTB-based sintered magnet used in the manufacturing method of the present disclosure are not limited to the shape and size of the RTB-based sintered magnet 100 illustrated. The upper surface 100a and the side surfaces 100b and 100c of the RTB-based sintered magnet 100 shown in the figure are flat, but the surface of the RTB-based sintered magnet 100 has irregularities or steps. Or may be curved.

  FIG. 1B shows an R-T-B system sintered magnet 100 in a state where a pressure-sensitive adhesive layer (adhesive layer) 20 is formed on a part of the surface (application region) of the R-T-B system sintered magnet 100. It is sectional drawing which shows a part typically. The adhesive layer 20 may be formed on the entire surface of the RTB-based sintered magnet 100. The pressure-sensitive adhesive layer 20 can be formed by applying the pressure-sensitive adhesive composition by a method such as spraying, dipping, or dispensing with a dispenser.

  FIG. 1C is a cross-sectional view schematically showing a part of the RTB-based sintered magnet 100 in a state where the particle size adjusting powder is adhered. The powder particles 30 constituting the particle size adjusting powder positioned on the surface of the R-T-B system sintered magnet 100 are attached so as to cover the coating region, and form the particle size adjusting powder layer 40 together with the pressure-sensitive adhesive composition. Yes. According to the manufacturing method of the RTB-based sintered magnet of the present disclosure, a plurality of regions (for example, the upper surface 100a and the side surface 100b) having different normal directions on the surface of the RTB-based sintered magnet 100 are used. However, the particle size adjusting powder can be easily attached in one application step without changing the direction of the R-T-B system sintered magnet 100. It is also easy to uniformly apply the particle size adjusted powder to the entire surface of the R-T-B system sintered magnet 100.

  When diffusion heat treatment is performed on the RTB-based sintered magnet 100 with the particle size adjusting powder attached thereto, elements contained in the particle size adjusting powder such as the heavy rare earth element RH are converted into the RTB system. It can diffuse efficiently from the surface of the sintered magnet to the inside without waste. During the diffusion heat treatment, the pressure-sensitive adhesive composition in the particle size-adjusted powder layer 40 does not become a low-viscosity liquid at 150 to 200 ° C. in an inert gas atmosphere, for example, and thermally decomposes in the range of 150 to 700 ° C. It is preferable that the magnet surface has a characteristic that does not leave a residue as much as possible.

  In the method of the present disclosure, the powder particles do not further overlap and adhere to the surface of the RTB-based sintered magnet 100, specifically, the powder particles 30 attached to the adhesive layer 20. Therefore, about one layer of the particle size adjusting powder adheres to the surface of the RTB-based sintered magnet 100 as shown in FIG. 1C. Therefore, the particle size-adjusted powder can be uniformly attached to the portion of the surface of the RTB-based sintered magnet 100 where the adhesive layer 20 is applied. Furthermore, when the particle size of the particle size adjusting powder is adjusted to be approximately the same as the layer thickness of the particle size adjusting powder to be formed, in the example shown in FIG. 1C, the particle size adjustment adhered to the surface of the R-T-B system sintered magnet 100. The layer thickness of the powder is about the particle size of the powder particles constituting the particle size adjusting powder. By utilizing this, the amount of the particle size adjusting powder per unit area on the surface of the R-T-B system sintered magnet 100 can be adjusted, and the amount of the element diffused in the R-T-B system sintered magnet 100 Can be controlled.

  In an embodiment of the present invention, an alloy or compound powder of heavy rare earth element RH, or a powder of heavy rare earth element RH compound and an RLM1M2 alloy (RL is one or more selected from Nd and Pr, M1 and M2 are Cu, R-T-B system sintered magnet with M oxide powder together with a particle size adjusting powder containing at least one selected from the group consisting of Fe, Ga, Co, Ni, and Al, and M1 = M2) Heat treatment is performed on the surface.

  When heat treatment is carried out with the above-mentioned particle size-adjusted powder present on the surface of an R-T-B sintered magnet without using M oxide powder, the nodule containing a large amount of light rare earth elements RL after the heat treatment The present inventors have found that there is a problem of occurrence on the surface. These lumps are mainly hemispherical particles with a size of several hundred μm to a maximum of 4 mm, and cannot be firmly fixed to the magnet surface, which can greatly hinder subsequent processes such as processing. all right. The detailed reason why such a bump is generated is unknown. According to the analysis by the present inventors, the RL contained in the rod-like material has moved from the inside of the magnet to the magnet surface due to the mutual diffusion accompanying the diffusion of the heavy rare earth element RH into the R-T-B system sintered magnet. When RL is contained in RL and the particle size adjusting powder, it is considered to be that RL. Further, when the particle size adjusting powder is adhered to the magnet by the pressure-sensitive adhesive, for example, a difference in RL or RH concentration on the magnet surface may occur due to a slight difference in particle size. Such a difference in the concentration of rare earth elements on the surface of the magnet may affect the formation of the bumps.

  As a result of repeated investigations by the inventors, it has been found that when the M oxide powder is present on the magnet surface together with the particle size adjusting powder and heat treatment is performed, no lumpy fixed matter is generated. When both the particle size-adjusted powder and the M oxide are present on the magnet surface, the RL having a strong reducing power is consumed for the reduction of the M oxide, so that the RL is prevented from agglomerating in the form of lumps and forms an RL oxide. Therefore, it is considered to exist on the magnet surface.

  Further, according to the present disclosure, the M element is appropriately selected so that the reduced M element does not diffuse into the magnet and adversely affect the magnet characteristics.

  Details of this embodiment will be described below.

1. Preparation of R-T-B system sintered magnet base material An R-T-B system sintered magnet base material to be diffused of heavy rare earth element RH is prepared. In this specification, for the sake of easy understanding, an RTB-based sintered magnet that is an object of diffusion of the heavy rare earth element RH may be strictly referred to as an RTB-based sintered magnet base material. The term “RTB-based sintered magnet” includes such an “RTB-based sintered magnet base material”. As this RTB-based sintered magnet base material, a known material can be used, for example, having the following composition.
Rare earth element R: 12-17 atom%
B (a part of B (boron) may be substituted with C (carbon)): 5 to 8 atomic%
Additive element M ′ (selected from the group consisting of Al, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb, and Bi At least one): 0 to 2 atomic%
T (a transition metal element mainly composed of Fe and may contain Co) and inevitable impurities: balance

  Here, the rare earth element R is mainly a light rare earth element RL (at least one element selected from Nd and Pr), but may contain a heavy rare earth element. In addition, when a heavy rare earth element is contained, it is preferable that at least one of Dy and Tb is included.

  The RTB-based sintered magnet base material having the above composition is manufactured by an arbitrary manufacturing method. The RTB-based sintered magnet base material may be sintered, or may be subjected to cutting or polishing.

2. Preparation of Particle Size Adjustable Powder In the embodiment of the present disclosure, the particle size adjusted powder is a powder obtained by granulating a diffusing agent powder or a diffusing agent powder and a diffusion aid powder, which will be described below, as necessary, to adjust the particle size. Say that.

[Diffusion agent]
The particle size adjusting powder includes a powder of an alloy or compound of heavy rare earth element RH which is at least one of Dy and Tb. These alloy and compound powders all function as diffusing agents.

  An alloy of heavy rare earth element RH is, for example, an RHM1M2 alloy (M1, M2 may be one or more selected from the group consisting of Cu, Fe, Ga, Co, Ni, and Al, and M1 = M2 may be used) and / or RHRLLM1M2 alloy (RL) Is one or more selected from Nd and Pr).

  The method for producing the alloy powder of heavy rare earth element RH is not particularly limited. An alloy ribbon may be prepared by a roll quenching method, and the alloy ribbon may be pulverized, or may be prepared by a known atomization method such as a centrifugal atomization method, a rotating electrode method, a gas atomization method, or a plasma atomization method. May be. You may grind | pulverize the ingot produced by the casting method. In the case of producing by a rapid cooling method or a casting method, M1 ≠ M2 is set in order to improve crushability. Typical examples of heavy rare earth element RH alloys are DyFe alloy, DyAl alloy, DyCu alloy, TbFe alloy, TbAl alloy, TbCu alloy, DyFeCu alloy, TbCuAl alloy, NdTbCu alloy, PrTbGa alloy, PrTbCuGa alloy and the like. The particle size of the alloy powder of heavy rare earth element RH is, for example, 500 μm or less, and the small one is about 10 μm.

  The compound of the heavy rare earth element RH is at least one selected from RH fluoride, RH oxyfluoride, and RH oxide, and these are collectively referred to as an RH compound. The RH oxyfluoride may be contained in the RH fluoride as an intermediate substance in the production process of the RH fluoride. These compound powders may be used alone or in combination with an RLM1M2 alloy powder described below. The particle size of many available RH compound powders is about 20 μm or less, typically 10 μm or less, and a small one is about several μm in terms of the size of the aggregated secondary particles.

[Diffusion aid]
The particle size adjusting powder may contain an alloy powder that functions as a diffusion aid. An example of such an alloy is the RLM1M2 alloy. RL is one or more selected from Nd and Pr, M1 and M2 are one or more selected from the group consisting of Cu, Fe, Ga, Co, Ni, and Al, and M1 = M2. Typical examples of the RLM1M2 alloy are NdCu alloy, NdFe alloy, NdCuAl alloy, NdCuCo alloy, NdCoGa alloy, NdPrCu alloy, NdPrFe alloy and the like. These alloy powders are used by mixing with the above-mentioned RH compound powder. A plurality of types of RLM1M2 alloy powder and RH compound powder may be mixed and used. The method for producing the RLM1M2 alloy powder is not particularly limited. When manufactured by a rapid cooling method or a casting method, in order to improve pulverizability, it is preferable to set M1 ≠ M2, and employ, for example, a ternary or higher alloy such as an NdCuAl alloy, an NdCuCo alloy, or an NdCoGa alloy. The particle size of the RLM1M2 alloy powder is, for example, 500 μm or less, and the smaller one is about 10 μm.

[Granularity adjustment]
The particle size of these powders is adjusted in a mixed state or a single state, and a particle size adjusted powder is produced. In one embodiment, the particle size is included in the particle size adjusting powder when the powder particles constituting the particle size adjusting powder are arranged on the entire surface of the RTB-based sintered magnet to form one particle layer. The amount of the heavy rare earth element RH may be set so as to be within a range of 0.7 to 1.5% by mass ratio with respect to the R-T-B based sintered magnet. The particle size may be determined by such calculations and / or experiments. The experiment for determining the particle size can be performed according to an actual production method.

  As the mass ratio of the heavy rare earth element RH diffused into the RTB-based sintered magnet to the RTB-based sintered magnet increases from zero, the increase in the coercive force increases. However, if the conditions other than the amount of RH, such as heat treatment conditions, are the same from experiments conducted separately, the coercive force is saturated when the amount of RH is around 1.0% by mass, and the amount of RH is increased beyond 1.5% by mass. However, the increase in coercive force did not increase. That is, when the amount of RH that is 0.7 to 1.5% by mass of the R-T-B system sintered magnet is adhered to the entire surface of the R-T-B system sintered magnet, it is most efficiently maintained. Magnetic force can be improved.

  When about one layer adheres to the surface of the RTB-based sintered magnet, if the RH amount falls within the above range, there is an advantage that the RH amount or the coercive force improvement degree can be managed by adjusting the particle size. The optimum particle size depends on the amount of RH contained in the particle size adjusted powder, but is, for example, more than 50 μm and 500 μm or less.

  The particle size of the particle size adjusting powder may be adjusted by classification using a standard sieve of JIS Z 8801. In addition, if the particle size-adjusted powder excluded by sieving is within 10% by mass, the influence is small, and it may be used without sieving. That is, the particle size of the particle size adjusting powder is preferably 90% by mass or more within the above range. In addition, the particle size of various powders in the present disclosure is classified according to the standard sieve described in JISZ8801, and depending on the particle size, for example, microscopic observation, a commercially available particle size distribution measuring device (for example, laser diffraction manufactured by Microtrac Bell, Inc.) -It can be measured by a scattering type particle size distribution measuring device.

  These powders are preferably mixed or singly and granulated with a binder. By granulating together with the binder, there is an advantage that the binder is melted in a post-heating step to be described later, and the powder particles are integrated with each other by the melted binder, and it is difficult to fall off and is easy to handle. Further, when a plurality of types of powders are mixed and used, granulation with a binder makes it possible to produce a particle size-adjusted powder having a uniform mixing ratio. Therefore, these powders are mixed at a constant mixing ratio. It becomes easy to be present on the surface of the system sintered magnet.

  When the alloy powder of heavy rare earth element RH is used alone, the particle size can be adjusted without granulation. For example, if the shape of the powder particles is equiaxed or spherical, the amount of RH of the RHM1M2 alloy powder to be adhered is 0.7 to 1.5% by mass ratio with respect to the R-T-B system sintered magnet. By adjusting the particle size in this way, it can be used as it is without being granulated.

  As the binder, it is preferable that the particle size-adjusted powder has a smooth flowability without sticking or agglomerating when the dried or mixed solvent is removed. Examples of the binder include PVA (polyvinyl alcohol). You may mix suitably using aqueous solvents, such as water, and organic solvents, such as NMP (n-methylpyrrolidone). The solvent is evaporated and removed in the granulation process described later.

  When a mixture of RLM1M2 alloy powder and RH compound powder is used, it may be difficult to mix them evenly by mixing these powders alone. This is because the powder of the RH compound generally has a relatively smaller particle size than the powder of the RLM1M2 alloy. For example, the particle size of RLM1M2 alloy powder is typically 500 μm or less, and the particle size of RH compound powder is typically 20 μm or less. For this reason, it is preferable to set it as the particle size adjustment powder which granulated the powder of RLM1M2 alloy, the powder of RH compound, and the binder. By adopting such a particle size adjusting powder, there is an advantage that the blending ratio of the RLM1M2 alloy powder and the RH compound powder can be made uniform throughout the powder. Moreover, it becomes possible to make it exist uniformly on the magnet surface.

  Any method of granulating with the binder may be used. Examples thereof include a rolling granulation method, a fluidized bed granulation method, a vibration granulation method, a high-speed air impact method (hybridization), a method of mixing powder and binder, and crushing after solidification.

When the RLM1M2 alloy powder and the RH compound powder are mixed, the abundance ratio (before heat treatment) of the RLM1M2 alloy and the RH compound in the powdered state on the surface of the RTB-based sintered magnet is RLM1M2 alloy in mass ratio. : RH compound = 96: 4 to 50:50. That is, the powder of the RLM1M2 alloy in the entire mixed powder contained in the paste can be 50% by mass or more and 96% by mass or less. The abundance ratio may be RLM1M2 alloy: RH compound = 95: 5-60: 40, and the effect of the present invention is great when 65: 35-50: 50. That is, the RLM1M2 alloy powder may be 60% by mass or more and 95% by mass, and preferably 50% by mass or more and 65% by mass or less of the whole of the mixed powder. When the RLM1M2 alloy and the RH compound are mixed and used at this mass ratio, the RLM1M2 alloy efficiently reduces the RH compound. As a result, the fully reduced RH diffuses into the _RTB -based sintered magnet, and _HcJ can be greatly improved with a small amount of RH. When the RH compound contains a fluoride or oxyfluoride of RH, the RLM1M2 alloy efficiently reduces the RH compound, so that the fluorine contained in the RH compound does not enter the R-T-B system sintered magnet, and the RLM1M2 It has been confirmed by another experiment by the inventors that the alloy remains outside the R-T-B sintered magnet in association with the RL of the alloy. Of fluorine in the interior of the R-T-B based sintered magnet to prevent entry it is considered to be a factor that does not reduce significantly the B _r of the R-T-B based sintered magnet.

  In the embodiment of the present disclosure, it is not necessarily excluded that a powder (third powder) other than the powder of the RLM1M2 alloy and the RH compound is present on the surface of the R-T-B system sintered magnet. Care must be taken not to inhibit diffusion of RH in the RH compound into the R-T-B system sintered magnet. As for the mass ratio of the powder of "RLM1M2 alloy and RH compound" to the whole powder which exists on the surface of a RTB system sintered magnet, it is desirable that it is 70% or more.

  By using the powder whose particle size is adjusted in this way, the powder particles constituting the particle size-adjusted powder can be uniformly and efficiently adhered to the entire surface of the R-T-B system sintered magnet. According to the method of the present disclosure, the thickness of the coating film does not deviate due to gravity or surface tension unlike the conventional immersion method or spray method.

  In order to make the powder particles constituting the particle size-adjusted powder more uniformly on the surface of the R-T-B system sintered magnet, the powder particles are about one layer, specifically, one to three layers. It is preferable to arrange on the surface of the RTB-based sintered magnet. When a plurality of types of powder are granulated and used, the granulated particle size-adjusted powder particles are present in 1 layer or more and 3 layers or less. Here, “3 layers or less” does not mean that the particles adhere to three layers continuously, but it is allowed that the particles partially adhere to up to three layers depending on the thickness of the adhesive and the size of each particle. It means that. In order to more accurately control the amount of RH attached depending on the particle size, the thickness of the coating layer is set to one or more and less than two layers of the powder particle layer (the layer thickness is equal to or larger than the particle size and twice the particle size). It is preferable that the particle size adjusting powders are bonded to each other by the binder in the particle size adjusting powder and are not laminated in two or more layers.

3. Adhesive application process As an adhesive, PVA (polyvinyl alcohol), PVB (polyvinyl butyral), PVP (polyvinyl pyrrolidone), etc. are mention | raise | lifted. When the pressure-sensitive adhesive is a water-based pressure-sensitive adhesive, the RTB-based sintered magnet may be preliminarily heated before coating. The purpose of the preheating is to remove excess solvent and control the adhesive force, and to adhere the adhesive uniformly. The heating temperature is preferably 60 to 100 ° C. In the case of a highly volatile organic solvent-based pressure-sensitive adhesive, this step may be omitted.

  Any method may be used for applying the adhesive to the surface of the RTB-based sintered magnet. Specific examples of coating include spraying, dipping, and dispensing with a dispenser.

4). Step of Adhering Particle Size Adjusting Powder to Surface of R-T-B System Sintered Magnet In a preferred embodiment, an adhesive is applied to the entire surface (entire surface) of the R-T-B system sintered magnet. You may make it adhere to one part instead of the whole surface of a RTB system sintered magnet. According to the manufacturing method of the present disclosure, one or more particle size adjusting powders are adhered to a plurality of regions having different normal directions on the surface of the R-T-B system sintered magnet in one step. Can do.

  Any method may be used for attaching the particle size adjusting powder to the RTB-based sintered magnet. Examples of the adhesion method include a method of dipping an R-T-B type sintered magnet coated with a pressure-sensitive adhesive in a processing container containing particle size-adjusted powder, and a R-T-B type sintered powder coated with a pressure-sensitive adhesive. For example, a method of sprinkling particle size-adjusted powder on the magnet. At this time, vibration may be applied to the processing container containing the particle size adjusting powder, or the particle size adjusting powder may be flowed so that the particle size adjusting powder easily adheres to the surface of the RTB-based sintered magnet. However, in the present invention, since it is desired to deposit about one layer of the particle size adjusting powder, it is preferable that the adhesion is substantially only due to the adhesive strength of the adhesive. For example, the powder to be adhered in the processing container is put together with the impact media and given an impact to adhere to the surface of the R-T-B system sintered magnet, or the powder is bonded by the impact force of the impact media to form a film. A method of growing is not preferable.

  In a preferred embodiment, a heat treatment (post heat treatment) for fixing the particle size-adjusted powder to the surface of the RTB-based sintered magnet is performed. The heating temperature can be set to 150-200 ° C. If the particle size adjusting powder is granulated with a binder, the particle size adjusting powder is fixed by melting and fixing the binder.

5. Step of making M oxide exist [M oxide]
In the present disclosure, a powder of M oxide is prepared, and the powder of M oxide is present on the surface of the RTB-based sintered magnet together with the above-described particle size adjusting powder. Here, M is at least one selected from the group consisting of Mg, Al, Si, Ti, Cr, Mn, Fe, Co, and Zr.

  The step of allowing M oxide powder to be present on the surface of the RTB-based sintered magnet together with the particle size-adjusting powder is performed by attaching the particle size-adjusting powder to the surface of the RTB-based sintered magnet. Even if the oxide is sprinkled from above the RTB-based sintered magnet, or the RTB-based sintered magnet having the particle size-adjusted powder attached to the surface is buried in the M oxide powder Good.

  In order to disperse the M oxide, the M oxide powder is sprinkled as it is on the surface of the R-T-B system sintered magnet having the particle size adjusting powder attached thereto, or the M oxide powder is sprayed with water or an organic solvent. What is necessary is just to spray-disperse by dispersing in a solvent such as. In addition, M oxide powder is laid on the base plate on which the R-T-B system sintered magnet of the heat treatment apparatus is mounted, and after the R-T-B system sintered magnet is mounted thereon, M oxidation is performed. You may spray things.

  In order to embed the R-T-B type sintered magnet in the M oxide powder, the inside of the processing vessel is filled with the M oxide powder, and the particle size adjusting powder is adhered to the R- An M-oxide powder may be placed so as to embed a TB sintered magnet or to cover the RTB sintered magnet on the base plate of the heat treatment apparatus.

  The individual components (powder particles) of the particle size adjusting powder and M oxide powder particles may be mixed and granulated with a binder, and the granulated powder may be adhered to the magnet surface. In the present disclosure, such a granulated powder is referred to as a particle size adjusted mixed powder. In this case, for example, the powder of the diffusing agent and the powder of M oxide, or the powder of the compound of heavy rare earth element RH, the powder of the diffusion aid and the powder of M oxide are granulated with a binder and used. By granulating the M oxide powder together with a diffusing agent or a diffusion aid, there is no need to separately provide a step for allowing the M oxide powder to exist. Moreover, it becomes possible to make M oxide exist uniformly with a desired compounding ratio. At this time, if the M oxide is excessively mixed with the diffusing agent, there is a possibility that the granulation cannot be performed well. Therefore, the mixing ratio of the M oxide is 1.0% by mass or more and 15.0% by mass with respect to the diffusing agent. It is preferable that it is about the following, more preferably about 2.0 mass% or more and 10.0 weight% or less. The step of attaching the particle size-adjusted mixed powder to the surface of the RTB-based sintered magnet may be in accordance with the step of attaching the particle size-adjusted powder to the surface of the RTB-based sintered magnet.

6). Diffusion process of heat treating R-T-B system sintered magnet with particle size-adjusted powder and M oxide or particle-size-adjusted mixed powder adhered The heat treatment temperature for diffusion is the sintering of R-T-B system sintered magnet It is below the temperature (specifically, for example, 1000 ° C. or below). When the particle size adjusted powder or the particle size adjusted mixed powder contains RLM1M2 alloy powder, the temperature is higher than the melting point thereof, for example, 500 ° C. or higher. The heat treatment time is, for example, 10 minutes to 72 hours. Moreover, you may perform the heat processing for 10 minutes-72 hours at 400-700 degreeC further as needed after the said heat processing.

(Experimental example 1)
First, by a known method, the composition ratio Nd = 13.5, B = 5.7, Al = 1.0, Cu = 0.1, Co = 2.2, Ga = 0.3, balance Fe (atomic%) R-T-B based sintered magnets were prepared. By machining this, an RTB-based sintered magnet base material having a thickness of 4.9 mm, a width of 7.4 mm, and a length of 60 mm was obtained. A sample of 4.9 mm x 7.4 mm x 7.4 mm was cut out from the center part of the obtained R-T-B system sintered magnet base material in the direction of 60 mm length, and each surface was subjected to surface grinding by 0.2 mm. after a 4.5mm × 7.0mm × 7.0mm, a result of measurement of magnetic properties by B-H _{tracer, H cJ} is 1105kA / m, _{B r} was 1.41T (n = 6 average).

Next, TbF ₃ powder or DyF ₃ powder and NdCu powder were granulated with a binder to prepare a particle size adjusted powder. The TbF ₃ powder and the DyF ₃ powder were commercially available non-spherical powders, and the particle size was 10 μm or less. The NdCu powder was a spherical Nd ₇₀ Cu ₃₀ alloy powder produced by a centrifugal atomization method, and the particle size was 106 μm or less. The binder used was PVA (polyvinyl alcohol) and water as a solvent. The particle size adjustment powder A is NdCu powder: TbF ₃ powder: PVA: water = 52: 42: 3: 3 (mass ratio) (mass ratio of NdCu powder: TbF ₃ powder is 55:45), and the particle size adjustment powder B is NdCu powder: TbF ₃ powder: PVA: water = 56: 38: 3: 3 (mass ratio) (mass ratio of NdCu powder: TbF ₃ powder is 60:40), and the particle size adjusting powder C is NdCu powder: DyF ₃ powder : PVA: water = 56: 38: 3: 3 (mass ratio): in (NdCu powder DyF ₃ powder mass ratio of 60:40), a paste obtained by mixing each hot air drying to evaporate the solvent, in an Ar atmosphere Crushed with.

  Next, an adhesive was applied to the RTB-based sintered magnet base material so that the RTB-based sintered magnet base material was about 0.2 mass% after drying. Specifically, PVP (polyvinylpyrrolidone) (adhesive: water = diluted to 30:70) is used as the adhesive, and the RTB-based sintered magnet base material is immersed in the adhesive, and the constant is 5 mm / sec. An adhesive was applied to the entire surface of the RTB-based sintered magnet base material at a pulling rate of. After applying the pressure-sensitive adhesive, excess water contained in the pressure-sensitive adhesive was dried at 120 ° C. for 5 to 10 minutes.

  Next, after the RTB-based sintered magnet base material coated with the pressure-sensitive adhesive was cooled to room temperature, the particle size-adjusted powder was sprinkled on the entire surface of the RTB-based sintered magnet base material.

  When the R-T-B system sintered magnet base material with the particle size-adjusted powder adhered was observed with a stereomicroscope, the R-T-B system sintered magnet base material was uniformly layered on the surface of the R-T-B system sintered magnet base material with almost no gap. Adhesion was observed. At this time, the particle size of the particle size adjusted powder was adjusted so that the adhesion amount of Tb or Dy in the particle size adjusted powder was 0.7 mass% with respect to the RTB-based sintered magnet base material. Specifically, a sieve was appropriately selected and classified from JIS Z 8801 standard sieves of 50 to 250 μm, and the particle size was adjusted so as to achieve the above adhesion amount.

  Meanwhile, M oxide powder was prepared. Table 1 shows the M oxide used in the experiment. These M oxides were commercially available powders, and the particle size thereof was 10 μm or less.

  The M oxide was uniformly coated by the coating method shown in Table 1 on the surface of 7.4 mm × 60 mm (upper surface 1 surface) of the RTB-based sintered magnet base material to which the particle size adjusting powder was adhered. Each of the coating methods is “dry powder sprinkling”, a method in which M oxide powder is sprinkled from above using a sieve, and “spray” is a method in which M oxide powder and pure water are mixed with M oxide: pure water = 1: 1 (mass) Ratio) is a method in which the slurry mixed by spraying is used, and “buried” is a method in which an RTB-based sintered magnet base material in which a particle size-adjusted powder is adhered in an M oxide powder is buried. . (Sample Nos. 1-25.)

Sample No. Apart from 1 to 25, as examples of the particle size-adjusted mixed powder, Samples 26-28 were prepared. The component of the particle size adjustment powder A serving as a base was set to 100%, and M oxide in the amount shown in Table 1 was added thereto to prepare a particle size adjustment mixed powder. That is, sample No. In 26, NdCu powder: TbF ₃ powder: PVA: water: M oxide = 52: 42: 3: 3: 8 ratio, the samples 27, 28 NdCu powder: TbF ₃ powder: PVA: water: M oxide = Pastes mixed at a ratio of 52: 42: 3: 3: 4 were dried with hot air, pulverized and classified in the same manner as described above. Each of them was adhered to the surface of the RTB-based sintered magnet base material coated with an adhesive in the same manner as described above.

  Sample No. 1-28 were accommodated in the heat processing furnace, and heat processing was performed at 900 degreeC for 10 hours in Ar atmosphere of 100Pa. Thereafter, heat treatment was further performed at 500 ° C. for 3 hours in a vacuum of 10 Pa or less.

  The appearance and magnetic properties of the magnet after heat treatment were evaluated. The results are shown in Table 1. The appearance evaluation was visually confirmed, and it was determined that there were those in which the bumps were observed on the surface of the RTB-based sintered magnet after the heat treatment, and those that were not observed.

FIG. 2 is a view showing a photograph of an RTB-based sintered magnet (left side) in which no bumps are generated and an RTB-based sintered magnet (right side) in which the knobs are generated. is there. The RTB-based sintered magnet (left side) in which no bumps were generated is a sample (sample No. 10) in which a powder of Zr oxide (ZrO ₂ ) was applied as M oxide. . The RTB-based sintered magnet (right side) in which the bumps are generated is a sample (sample No. 1) in which the M oxide powder was not applied.

The magnetic properties are 4 by cutting a sample of 4.9 mm × 7.4 mm × 7.4 mm from the center of the R-T-B sintered magnet in the direction of 60 mm length and grinding each surface by 0.2 mm. After setting the thickness to 0.5 mm × 7.0 mm × 7.0 mm, the magnetic properties were measured with a BH tracer. Considering the variation in magnetic properties of the _RTB -based sintered magnet base material, the measured H _cJ is equal to or higher than “H _cJ −20 kA / m of a sample not coated with M oxide using the same particle size-adjusted powder” If it was less than that, it was rated as x.

  From Table 1, in the R-T-B system sintered magnet coated with M oxide used in the present invention, or included in the particle size-adjusted mixed powder, and heat-treated, the nodule is produced without affecting the magnetic properties. It was found that the occurrence of odor was suppressed (overall evaluation: ◯).

The present invention can provide a method for producing an _RTB -based sintered magnet that improves _HcJ with less heavy rare earth element RH and has high production efficiency.

Claims (8)

A step of preparing an R-T-B sintered magnet (R is a rare earth element, T is Fe or Fe and Co);
Preparing a particle size adjusting powder formed from a powder of an alloy or compound of heavy rare earth element RH which is at least one of Dy and Tb;
Preparing a powder of M oxide (M is one or more selected from the group consisting of Mg, Al, Si, Ti, Cr, Mn, Fe, Co, Zr);
An application step of applying an adhesive to the application region on the surface of the RTB-based sintered magnet;
By adhering the particle size adjusting powder together with the M oxide powder to the application region on the surface of the R-T-B type sintered magnet coated with the pressure-sensitive adhesive, the R-T-B type sintered magnet A step of causing a heavy rare earth element RH and the M oxide to be present on the surface;
The RTB-based sintered magnet on which the particle size-adjusted powder and the M oxide powder are present is heat-treated at a temperature lower than the sintering temperature of the RTB-based sintered magnet, A diffusion step of diffusing the heavy rare earth element RH contained in the particle size adjusted powder from the surface of the RTB-based sintered magnet to the inside;
The manufacturing method of the RTB type | system | group sintered magnet containing this.   The step of allowing the M oxide powder to be present on the surface of the RTB-based sintered magnet together with the particle size adjusting powder is performed on the surface of the RTB-based sintered magnet to which the particle size adjusting powder is adhered. The manufacturing method of the RTB type | system | group sintered magnet of Claim 1 which is a process of spraying the said powder of M oxide.   The step of allowing the M oxide powder to exist on the surface of the R-T-B system sintered magnet together with the particle size-adjusted powder comprises the steps of: The manufacturing method of the RTB type | system | group sintered magnet of Claim 1 which is the process of burying in the powder of M oxide. A step of preparing an R-T-B sintered magnet (R is a rare earth element, T is Fe or Fe and Co);
Powder of alloy or compound of heavy rare earth element RH which is at least one of Dy and Tb, and M oxide (M is selected from the group consisting of Mg, Al, Si, Ti, Cr, Mn, Fe, Co, Zr) Preparing a particle size-adjusted mixed powder formed from one or more powders;
An application step of applying an adhesive to the application region on the surface of the RTB-based sintered magnet;
The particle size adjustment mixed powder is adhered to the surface of the R-T-B system sintered magnet by adhering the particle size-adjusted mixed powder to the application region on the surface of the R-T-B system sintered magnet coated with the adhesive. Allowing the powder to exist;
The RTB-based sintered magnet having the particle size-adjusted mixed powder existing on the surface thereof is heat-treated at a temperature lower than the sintering temperature of the RTB-based sintered magnet, and is included in the particle size-adjusted powder. A diffusion step of diffusing the heavy rare earth element RH from the surface of the RTB-based sintered magnet to the inside;
The manufacturing method of the RTB type | system | group sintered magnet containing this.   The particle size adjusted powder or the particle size adjusted mixed powder is a powder of an RHM1M2 alloy (M1, M2 may be one or more selected from Cu, Fe, Ga, Co, Ni, and Al, M1 = M2 may be used), or an RLRHM1M2 alloy The manufacturing method of the RTB system sintered magnet in any one of Claim 1 to 4 containing (RL is 1 or more types chosen from Nd and Pr).   The particle size adjusted powder or the particle size adjusted mixed powder is an RH compound (RH is one or more selected from Dy and Tb, and the RH compound is one or more selected from RH fluoride, RH acid fluoride, and RH oxide). The manufacturing method of the RTB type | system | group sintered magnet in any one of Claim 1 to 4 containing a powder.   The particle size adjusted powder or the particle size adjusted mixed powder is an RLM1M2 alloy (RL is one or more selected from Nd and Pr, M1 and M2 are one or more selected from Cu, Fe, Ga, Co, Ni, and Al, M1 = M2) may be included. The method for producing an RTB-based sintered magnet according to claim 6.   8. The RTB-based sintered magnet according to claim 1, wherein the particle size adjusted powder or the particle size adjusted mixed powder is a particle size adjusted powder or a particle size adjusted mixed powder granulated together with a binder. Production method.