JP2018056334A - Method for manufacturing r-t-b based sintered magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply a layer of powder particles including a Pr-Ga alloy to a surface of an R-T-B based sintered magnet efficiently and uniformly without waste in order to increase Hby diffusing Pr and Ga into the R-T-B based sintered magnet.SOLUTION: A method for manufacturing an R-T-B based sintered magnet comprises: a step of preparing granulated powder into which powder of a Pr-Ga alloy is granulated together with a binder; a deposition step of heating at least a surface of an R-T-B based sintered magnet to deposit the granulated powder to the surface of the sintered magnet; and a diffusion step of performing a thermal treatment on the sintered magnet with the granulated powder deposited thereto at a temperature equal to or lower than a sintering temperature to diffuse Pr and Ga included in the granulated powder into the sintered magnet from the surface thereof.SELECTED DRAWING: Figure 1

Description

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

  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 high temperatures, 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, an _RTB -based sintered magnet used particularly for an electric vehicle motor is required to have a high H _cJ .

In the RTB-based sintered magnet, a part of the light rare earth element RL (eg, Nd or Pr) contained in R in the R ₂ T ₁₄ B compound is heavy rare earth element RH (eg, Dy or Tb). Substitution is known to improve H _cJ . As the substitution amount of RH increases, H _cJ 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 H _cJ 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. 2016/133071

  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 H _cJ 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.

Furthermore, in Patent Document 2, as a method for improving H _cJ without using RH, those are performed by bringing a powder of Pr—Ga alloy into contact with the surface of the R—T—B system sintered magnet and performing a heat treatment. A method is disclosed for diffusing in a magnet. According to this method, H _cJ of the _RTB -based sintered magnet can be improved without using RH. 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 Pr—Ga alloy is formed on a magnet surface in order to diffuse Pr and Ga into an _RTB -based sintered magnet to improve H _cJ , these powder particles Can be applied uniformly and efficiently on the surface of an _RTB -based sintered magnet, and Pr and Ga can be diffused from the magnet surface into the interior to greatly improve _HcJ. provide.

  In the embodiment, the manufacturing method of the RTB-based sintered magnet of the present disclosure includes a step of preparing an RTB-based sintered magnet (R is a rare earth element, T is Fe or Fe and Co), Pr—Ga alloy (Pr is 65 to 97 mass% of the entire Pr—Ga alloy, 20 mass% or less of Pr can be substituted with Nd, and 30 mass% or less of Pr is substituted with Dy and / or Tb. Ga is 3 mass% to 35 mass% of the entire Pr—Ga alloy, and 50 mass% or less of Ga can be substituted with Cu. Inevitable impurities may be included.) A step of preparing a granulated powder in which the powder is granulated together with a binder; and at least the surface of the RTB-based sintered magnet is heated, and the surface of the heated RTB-based sintered magnet Attaching the granulated powder to the surface, and attaching the granulated powder to The RTB-based sintered magnet was heat-treated at a temperature lower than the sintering temperature of the RTB-based sintered magnet, and Pr and Ga contained in the granulated powder were converted into the RT- A diffusion step of diffusing inward from the surface of the B-based sintered magnet.

  In one embodiment, the attaching step is a step of attaching the granulated powder to the entire surface of the RTB-based sintered magnet.

  In one embodiment, the amount of Ga contained in the granulated powder adhered to the entire surface of the RTB-based sintered magnet is 0.10 to 1 relative to the RTB-based sintered magnet. 0.0% by mass.

  In one embodiment, the attaching step includes immersing the heated RTB-based sintered magnet in the fluidized granulated powder, thereby allowing the RTB-based sintered magnet to be immersed. This is a step of attaching the granulated powder to the entire surface.

  In one embodiment, in the attaching step, the RTB-based sintered magnet has a thickness of 38 μm or more and 300 μm or less so that the granulated powder attached to the RTB-based sintered magnet has a thickness of 38 μm or more and 300 μm or less. The surface temperature and immersion time are adjusted.

In one embodiment, the RTB-based sintered magnet is
R: 27.5-35.0% by mass (R is at least one of rare earth elements, and necessarily contains Nd),
B: 0.80 to 0.99 mass%,
Ga: 0 to 0.8% by mass,
M: 0 to 2% by mass (M is at least one of Cu, Al, Nb and Zr),
Containing
The remainder T (T is Fe or Fe and Co) and inevitable impurities, and [T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%. When
[T] /55.85> 14 [B] /10.8
The composition satisfies the following inequality.

  In one embodiment, the Nd content of the Pr—Ga alloy is less than or equal to the inevitable impurity content.

  In one embodiment, the heat treatment step includes a step of performing a first heat treatment in a vacuum or an inert gas atmosphere at a temperature of greater than 600 ° C. and less than or equal to 950 ° C., and the RT- in which the first heat treatment is performed. The second heat treatment at a temperature lower than the temperature performed in the step of performing the first heat treatment in a vacuum or an inert gas atmosphere at a temperature of 450 ° C. or higher and 750 ° C. or lower with respect to the B-based sintered magnet. Carrying out the steps.

According to an embodiment of the present disclosure, a layer of powder particles containing a Pr—Ga alloy is _added to an _RTB to diffuse Pr and Ga into the _RTB -based sintered magnet to improve H _cJ. It can be uniformly and efficiently applied to the surface of the sintered system magnet. Moreover, it becomes possible to improve _HcJ of a _RTB system sintered magnet, without using the heavy rare earth element RH which is a rare resource.

It is a perspective view which shows an example of the processing container which can be used with a fluid immersion method. It is a perspective view which shows the position which measured the layer thickness of the granulated powder on the RTB type | system | group sintered magnet 100. FIG.

(1) Preparation of R-T-B system sintered magnet base material An R-T-B system sintered magnet base material to be diffused of the Pr-Ga alloy is prepared. In this specification, for the sake of easy understanding, an RTB-based sintered magnet that is a target of diffusion of the Pr-Ga alloy 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 the RTB-based sintered magnet base material, known materials can be used, but those having the following composition are preferable.
Rare earth element R: 27.5-35.0 mass%
B (a part of B (boron) may be substituted with C (carbon)): 0.80 to 0.99% by mass
Ga: 0 to 0.8% by mass,
Additive element M (at least one selected from the group consisting of Al, Cu, Zr, Nb): 0 to 2% by mass
T (which is a transition metal element mainly composed of Fe and may contain Co) and inevitable impurities: the balance However, the following inequality (1) is satisfied.
[T] /55.85> 14 [B] /10.8 (1)
([T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%)

  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.

On the other hand, when the Ga content exceeds 0.8% by mass, the main phase magnetization may decrease due to the inclusion of Ga in the main phase, and high _Br may not be obtained. As for Ga content, 0.5 mass% or less is more preferable.

  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 granulated powder [Diffusion agent]
The granulated powder is formed from Pr—Ga alloy powder. The Pr—Ga alloy powder functions as a diffusing agent.

In the Pr—Ga alloy, Pr is 65 to 97 mass% of the entire Pr—Ga alloy, and 20 mass% or less of Pr can be substituted with Nd, and 30 mass% or less of Pr is replaced with Dy and / or Tb. Can be replaced. Ga is 3 mass% to 35 mass% of the entire Pr—Ga alloy, and 50 mass% or less of Ga can be substituted with Cu. Inevitable impurities may be included. In this disclosure, “20% or less of Pr can be replaced with Nd” means that the Pr content (% by mass) in the Pr—Ga alloy is 100%, and that 20% can be replaced with Nd. Means. For example, if Pr in the Pr—Ga alloy is 65 mass% (Ga is 35 mass%), Nd can be substituted up to 13 mass%. That is, Pr is 52% by mass and Nd is 13% by mass. The same applies to Dy, Tb, and Cu. By performing the first heat treatment described later on the RTB-based sintered magnet material having the composition range of the present disclosure with the Pr—Ga alloy having Pr and Ga within the above range, Ga is allowed to pass through the grain boundary. It can be diffused deep inside the magnet. The present disclosure is characterized by using an alloy containing Ga containing Pr as a main component. Pr is, Nd, may be replaced with Dy and / or Tb, for each of the substitution amount is too small, Pr exceeds the above range, it is impossible to obtain a high B _r and high H _cJ. Preferably, the Nd content of the Pr—Ga alloy is unavoidable impurity content or less (1 mass% or less). Ga can replace 50% or less with Cu, but if the amount of substitution of Cu exceeds 50%, _HcJ may decrease.

  The method for producing the Pr—Ga alloy powder 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. The particle size of the Pr—Ga alloy powder is, for example, 500 μm or less, and the small one is about 10 μm.

According to the studies made by the inventors, it is impossible to obtain a high B _r and high H _cJ compared with the case of using the Pr in the case of using Nd instead of Pr. This is considered to be because in the specific composition of the present disclosure, Pr is more easily diffused into the grain boundary phase than Nd. In other words, it is considered that Pr has a larger penetration force into the grain boundary phase than Nd. Since Nd easily penetrates into the main phase, it is considered that a part of Ga is diffused into the main phase when an Nd—Ga alloy is used. When using the Pr-Ga alloy, as compared with the case of adding Ga in the stage of the alloy phase or alloy powder, the amount of Ga diffused into the main phase is low, the H _cJ with little lowering the B _r Can be improved.

By performing the heat treatment with the Pr—Ga alloy powder adhered to the R—T—B system sintered magnet material, it is possible to diffuse Pr and Ga through the grain boundary while hardly diffusing into the main phase. . As a result of the presence of Pr accelerating grain boundary diffusion, it is possible to diffuse Pr and Ga deep inside the magnet. Thus, while reducing the content of RH, it is possible to obtain a high B _r and high H _cJ.

[Granulation]
These powders are granulated with a binder, either mixed or alone. By granulating together with the binder, the powder particles can be easily attached to the surface of the RTB-based sintered magnet simply by bringing the granulated powder into contact with the surface of the heated RTB-based sintered magnet. it can. When a mixture of a plurality of types of powder is used, granulated powder having a uniform mixing ratio can be produced by granulating with a binder. For this reason, it becomes easy to make these powders uniformly exist on the surface of the RTB-based sintered magnet at a desired mixing ratio. In addition, when a powder having a small particle size such as an RH compound powder is used alone, if the particle size is increased to some extent by granulation, it becomes easy to adhere uniformly and efficiently to the magnet surface.

  The binder preferably has thermoplasticity and allows the granulated powder to flow more smoothly without sticking or agglomerating when the dried or mixed solvent is removed. Examples of the binder include polyester and PVA (polyvinyl alcohol). You may mix suitably using water-based solvents, such as water, and organic solvents, such as NMP (N-methylpyrrolidone). The solvent is evaporated and removed in the granulation process described later.

  Any method for granulating the powder together with the binder may be used. For granulation methods, for example, rolling granulation method, fluidized bed granulation method, vibration granulation method, high-speed air impact method (hybridization), powder and binder are mixed to produce a paste or slurry, The method of solidifying and crushing is mentioned afterwards.

  The particle size of the granulated powder is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less. When the particle size of the granulated powder is too large, it becomes difficult to control the adhesion amount of the powder particles. The size of the smallest particle contained in the granulated powder is about 10 μm.

  In the embodiment of the present disclosure, it is not necessarily excluded that a powder other than the Pr—Ga alloy powder (second powder) is present on the surface of the R—T—B system sintered magnet. Care must be taken not to inhibit the diffusion of Ga into the RTB-based sintered magnet. The mass ratio of the “Pr—Ga alloy” powder in the entire powder existing on the surface of the RTB-based sintered magnet is desirably 70% or more.

(3) Adhering step A preheated magnet is brought into contact with the granulated powder. This contact allows the granulated powder to adhere to the magnet surface by melting the binder of the granulated powder by the heat of the magnet surface. The heated magnet selectively melts the binder in the granulated powder in contact with the surface thereof, so that the powder particles constituting the granulated powder can be evenly distributed over the entire surface of the R-T-B system sintered magnet. It can be attached efficiently. Therefore, according to the method of the present disclosure, the thickness of the coating film is not biased by gravity or surface tension, unlike the dipping method or spraying method of the prior art. Further, since the granulated powder does not adhere to anything other than the preheated magnet, there is no waste. In addition, since a pre-granulated powder is used, a necessary amount of powder particles can be uniformly adhered to the magnet surface in a single coating operation, which is efficient.

  Hereinafter, the adhesion process in the embodiment of the present disclosure will be described in more detail.

  (I) Preheating the RTB-based sintered magnet. The purpose of the preheating is to melt the binder of the granulated powder by the heat of the magnet surface and adhere it to the surface of the RTB-based sintered magnet. The lower limit of the heating temperature is equal to or higher than the melting temperature of the binder used for the granulated powder (the temperature at which melting starts and becomes possible to adhere to the magnet surface), and is specifically about 100 ° C. although it depends on the binder. On the other hand, if the heating temperature is too high, too much granulated powder adheres and it becomes difficult to control the amount of adhesion, so the upper limit of the heating temperature is 230 ° C., preferably 180 ° C., more preferably 150 ° C.

  (Ii) Adhere the granulated powder. The granulated powder is adhered to the preheated RTB-based sintered magnet. Any method may be used, for example, a method in which a preheated RTB-based sintered magnet is immersed in a processing container containing granulated powder, or a preheated RTB system. For example, a method of sprinkling granulated powder on a sintered magnet. At this time, vibration may be applied to the processing container containing the granulated powder, or the granulated powder may be fluidized with air. Among them, a so-called fluidized bed coating process in which a preheated RTB-based sintered magnet is immersed in the fluidized granulated powder is preferable.

  Hereinafter, an example in which the fluid immersion method is applied to the adhesion process in the present disclosure will be described. The fluid dipping method is a method widely used in the field of powder coating, and a heated coating is immersed in a fluidized thermoplastic powder coating, and the paint is heated by the heat of the surface of the coating. This is a method of fusing. In this example, in order to apply the conventional fluidized dipping method to a magnet, instead of the thermoplastic powder coating material, a diffusing agent Pr—Ga alloy is granulated with a thermoplastic binder as described above.

  Any method may be used for flowing the granulated powder. For example, as one specific example, a method of using a container provided with a porous partition wall at the bottom will be described. In this example, the granulated powder is put into a container, a gas such as air or inert gas is injected into the container from the lower part of the partition wall, and the granulated powder above the partition wall is floated by the pressure or air flow. It can be made to flow. In the method of the present disclosure, since the granulated powder is heavier than the powder coating, it is necessary to increase the flow rate of the gas as compared with the powder coating.

  The time for immersing the RTB-based sintered magnet in the granulated powder flowing inside the container is, for example, about 0.5 to 10.0 seconds, although it depends on the temperature of the preheating. In this method, the adhesion amount can be controlled by adjusting the preheating temperature and the immersion time. When it is desired to achieve a desired amount of adhesion, the immersion time can be shortened by increasing the preheating temperature, but if it is too high, it becomes difficult to control the immersion time. On the other hand, if the preheating temperature is too low, the immersion time becomes too long and the efficiency is deteriorated. The adhesion amount tends to increase as the magnet has a larger specific surface area per unit volume even with the same immersion time. Depending on the magnet shape, the preheating temperature and the immersion time when a desired amount of adhesion is desired can be determined by experiment.

  According to the above method, the thickness of the coating film is not biased by gravity or surface tension, unlike the conventional dipping method or spraying method. Furthermore, by adjusting the preheating temperature and the dipping time, it is possible to control the amount of the granulated powder attached, and thus the amount of Ga attached. Adjusting the temperature and immersion time of the surface of the RTB-based sintered magnet so that the thickness of the granulated powder adhering to the RTB-based sintered magnet is not less than 38 μm and not more than 350 μm. preferable.

The adhesion amount of Ga is preferably 0.10 to 1.0% by mass of the R-T-B system sintered magnet when the granulated powder is applied to the entire surface of the R-T-B system sintered magnet. . As the mass ratio of the Pr—Ga alloy diffused into the _RTB -based sintered magnet to the _RTB -based sintered magnet increases from zero, the increase in H _cJ increases. However, from experiments conducted separately, it was found that when the conditions other than the Ga amount such as the heat treatment conditions are the same, the increase in H _cJ does not increase even if the Ga amount is increased _beyond 1.0 mass%. That is, a Pr—Ga alloy having an amount of Ga of 0.10 to 1.0% by mass of the RTB-based sintered magnet was adhered to the entire surface of the RTB-based sintered magnet. Sometimes, H _cJ can be improved most efficiently.

  (Iii) A post-heating step may be performed. The heating temperature is preferably 150 to 200 ° C. At this time, the granulated powder is more firmly fixed by melting and fixing the binder, which is preferable.

(4) Diffusion heat treatment After the above adhesion step, the RTB-based sintered magnet with the granulated powder adhered is heat-treated to a temperature equal to or lower than the sintering temperature of the RTB-based sintered magnet, A diffusion step of diffusing Pr and Ga contained in the granulated powder from the surface of the RTB-based sintered magnet to the inside is performed.

  The heat treatment is preferably performed by the following first heat treatment and second heat treatment.

(Step of performing the first heat treatment)
The RTB-based sintered magnet material to which the Pr—Ga alloy powder layer having the above composition is attached is heat-treated at a temperature of more than 600 ° C. and not more than 950 ° C. in a vacuum or an inert gas atmosphere. In this specification, this heat treatment is referred to as a first heat treatment. As a result, a liquid phase containing Pr and Ga is generated from the Pr—Ga alloy, and the liquid phase is diffused and introduced from the surface of the sintered material through the grain boundary in the RTB-based sintered magnet material. Is done. Thereby, Ga together with Pr can be diffused deep into the RTB-based sintered magnet material through the grain boundary. If the first heat treatment temperature is 600 ° C. or less, the amount of liquid phase containing Pr or Ga may be too small to obtain high H _cJ, and if it exceeds 950 ° C., H _cJ may be reduced. There is sex. Preferably, the RTB-based sintered magnet material subjected to the first heat treatment (over 600 ° C. and 940 ° C. or less) is cooled at a rate of 5 ° C./min or more from the temperature at which the first heat treatment is performed. It is preferable to cool to 300 ° C. Higher H _cJ can be obtained. More preferably, the cooling rate to 300 ° C is 15 ° C / min or more.

(Step of performing the second heat treatment)
With respect to the RTB-based sintered magnet material subjected to the first heat treatment, in a vacuum or an inert gas atmosphere, the temperature is lower than the temperature performed in the step of performing the first heat treatment, and Heat treatment is performed at a temperature of 450 ° C. or higher and 750 ° C. or lower. In this specification, this heat treatment is referred to as a second heat treatment. By performing the second heat treatment, an RT-Ga phase is generated in the grain boundary phase, and high H _cJ can be obtained. When the second heat treatment is at a higher temperature than the first heat treatment, or when the temperature of the second heat treatment is less than 450 ° C. or more than 750 ° C., the amount of R—T—Ga phase produced is too small and high H Can't get _cJ .

(Experimental example 1)
First, by a known method, the composition ratio Nd = 30.0, B = 0.89, Al = 0.1, Cu = 0.1, Co = 1.1, and the balance Fe (mass%) RTB A system sintered magnet was produced. By machining this, an RTB-based sintered magnet base material having a size of 4.5 mm thick × 15 mm wide × 26 mm long was obtained.

  Next, the Pr—Ga alloy powder was granulated with a binder to produce a granulated powder. The raw materials of the respective elements were weighed so that the composition ratios were Pr = 89 and Ga = 11, and the raw materials were dissolved, and a ribbon or flake-like alloy was obtained by a single roll super rapid cooling method (melt spinning method). The obtained alloy was pulverized in an argon atmosphere using a mortar. The pulverized Pr—Ga alloy powder was classified with a sieve to a particle size of 106 μm or less. Using polyester as the binder and NMP (N-methylpyrrolidone) as the solvent, a paste was prepared by mixing with Pr—Ga alloy powder: polyester: NMP = 90: 5: 5 (mass ratio). This paste was dried with hot air to evaporate the solvent, and then pulverized in an Ar atmosphere and classified with a sieve to obtain a granulated powder of 106 μm or less.

  Next, a processing container 20 having a configuration schematically shown in FIG. 1 was prepared for use in the fluid immersion method. This processing container has a generally cylindrical shape with the upper part opened, and has a porous partition wall 30 at the bottom. The treatment container 20 used in the experiment had an inner diameter of 78 mm and a height of 200 mm, and the partition wall 30 had an average pore diameter of 15 μm and a porosity of 40%. The granulated powder was put into the processing vessel 20 to a depth of about 50 mm. The granulated powder was caused to flow by injecting air into the processing vessel 20 from below the porous partition wall 30 at a flow rate of 20 liters / min. The height of the flowing powder was about 70 mm. An RTB-based sintered magnet base material 100 preheated to 110 ° C. in a drying furnace is fixed with a clamping jig (not shown), immersed in a flowing granulated powder for 1 second, and pulled up. The granulated powder was adhered to the B-based sintered magnet base material 100. The jig was fixed by two-point contact on both sides of the 4.5 × 26 mm surface of the magnet, and the surface with the narrowest area of 4.5 mm × 15 mm was immersed as the upper and lower surfaces. The magnet to which the granulated powder was adhered was post-heated at 150 ° C. for 15 minutes to fix the granulated powder.

  The thickness in the 4.9 mm direction of the RTB-based sintered magnet base material 100 to which the granulated powder was fixed was measured. Measurements were made at three measurement positions 1, 2, and 3 in FIG. 2 for each RTB-based sintered magnet base material (N = 5 for each). At the time of immersion, measurement position 1 was on the upper side and measurement position 3 was on the lower side. Table 1 shows half the value (value of increase on one side) of the value increased from the RTB-based sintered magnet base material before the granulated powder adheres. All three locations had almost the same value, and there was almost no variation in thickness depending on the measurement location.

(Experimental example 2)
The same RTB-based sintered magnet base material as in Experimental Example 1 and granulated powder were prepared. Using the same processing vessel as in Experimental Example 1, the granulated powder was applied to the RTB-based sintered magnet base material in the same manner as in Experimental Example 1, except that the preheating temperature and the immersion time were changed to the values shown in Table 2. Attached. No post-heating step was performed. Table 2 shows the adhesion amount of the granulated powder obtained from the increase in the weight of the magnet and the Ga adhesion amount calculated therefrom. The adhesion amount of Ga in Table 2 is the mass ratio of Ga present on the magnet surface to the total mass of the R-T-B system sintered magnet base material. This Ga adhesion amount was calculated | required from the mass of the granulated powder adhering to the whole surface of the RTB system sintered magnet base material, and Ga density | concentration in granulated powder. The higher the preheating temperature of the RTB-based sintered magnet base material and the longer the immersion time, the more the adhesion amount can be increased. By adjusting the preheating temperature and the immersion time, the Ga adhesion amount can be increased. It turns out that it can be controlled. Moreover, in order to make Ga amount into 0.10-1.0 mass% of a R-T-B type | system | group sintered magnet base material, preheating temperature can be adjusted at 80-120 degreeC, and immersion time can be adjusted for 1 to 10 seconds. all right.

(Experimental example 3)
An RTB-based sintered magnet base material having a composition shown in Table 3 and having a size of 7.4 mm × 7.4 mm × 7.4 mm was prepared. A granulated powder was produced in the same manner as in Experimental Example 1 using a Pr—Ga alloy shown in Table 4, polyester as a binder, and NMP as a solvent. The produced granulated powder was adhered to the same RTB-based sintered magnet base material as in Experimental Example 1 in the same manner as in Experimental Example 1 in the combinations shown in Table 5. However, the preheating temperature and the immersion time are adjusted, and the layer thickness of the adhered granulated powder is controlled to be 100 μm or more and 300 μm or less, and as a result, the amount of Ga adhesion becomes 0.2 to 0.7 mass%. I did it.

Furthermore, these were heat-treated for the heat treatment temperature and time shown in Table 5. The entire surface of each sample is cut by 0.2 mm using a surface grinder on the R-T-B sintered magnet after heat treatment, and a 7.0 mm × 7.0 mm × 7.0 mm cube is cut out. After that, the magnetic properties were measured. Table 5 shows the measured magnetic property values. All these RTB-based sintered magnets have high magnetic properties of B _r ≧ 1.30 T and H _CJ ≧ 1490 kA / m, and H _CJ is 160 kA for each without substantially reducing B _r. / M or more was confirmed.

Embodiments of the present disclosure can be used for the production of rare earth sintered magnets that require high H _cJ because _{less HrJ} can improve the H _cJ of _RTB -based sintered magnets with fewer Pr—Ga alloys. .

20 processing vessel 30 porous partition wall 100 RTB-based sintered magnet base material

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);
Pr—Ga alloy (Pr is 65 to 97 mass% of the entire Pr—Ga alloy, 20 mass% or less of Pr can be substituted with Nd, and 30 mass% or less of Pr is substituted with Dy and / or Tb. Ga is 3 mass% to 35 mass% of the entire Pr—Ga alloy, and 50 mass% or less of Ga can be substituted with Cu. Inevitable impurities may be included.) Preparing a granulated powder in which the powder is granulated with a binder;
An adhesion step of heating at least the surface of the RTB-based sintered magnet and attaching the granulated powder to the surface of the heated RTB-based sintered magnet;
The RTB-based sintered magnet to which the granulated powder is adhered is heat-treated at a temperature not higher than the sintering temperature of the RTB-based sintered magnet, and Pr and Ga contained in the granulated powder. A diffusion step of diffusing 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 method for producing an RTB-based sintered magnet according to claim 1, wherein the attaching step is a step of attaching the granulated powder to the entire surface of the RTB-based sintered magnet. .   The amount of Ga contained in the granulated powder adhered to the entire surface of the RTB-based sintered magnet is 0.10 to 1.0 mass% with respect to the RTB-based sintered magnet. The manufacturing method of the RTB type | system | group sintered magnet of Claim 2 which exists.   The adhering step is performed by immersing the heated RTB-based sintered magnet in the fluidized granulated powder, so that the entire surface of the RTB-based sintered magnet is immersed. The manufacturing method of the RTB type | system | group sintered magnet of Claim 2 or 3 which is the process of making the said granulated powder adhere.   In the adhering step, the temperature of the surface of the RTB-based sintered magnet and the thickness of the granulated powder adhering to the RTB-based sintered magnet are 38 μm to 300 μm. The manufacturing method of the RTB type | system | group sintered magnet of Claim 4 which adjusts immersion time. The RTB-based sintered magnet is
R: 27.5-35.0% by mass (R is at least one of rare earth elements, and necessarily contains Nd),
B: 0.80 to 0.99 mass%,
Ga: 0 to 0.8% by mass,
M: 0 to 2% by mass (M is at least one of Cu, Al, Nb and Zr),
Containing
The remainder T (T is Fe or Fe and Co) and inevitable impurities, and [T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%. When
[T] /55.85> 14 [B] /10.8
The manufacturing method of the RTB type | system | group sintered magnet in any one of Claim 1 to 5 which has a composition which satisfies inequality of these.   The manufacturing method of the RTB system sintered magnet according to any one of claims 1 to 6 whose Nd content of said Pr-Ga alloy is below inevitable impurity content.   The heat treatment step includes a step of performing a first heat treatment in a vacuum or an inert gas atmosphere at a temperature of more than 600 ° C. and not more than 950 ° C., and an RTB-based sintered magnet on which the first heat treatment has been performed. In contrast, a step of performing the second heat treatment at a temperature lower than the temperature performed in the step of performing the first heat treatment in a vacuum or an inert gas atmosphere and a temperature of 450 ° C. or higher and 750 ° C. or lower; The manufacturing method of the RTB type | system | group sintered magnet in any one of Claim 1 to 7 containing these.

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