JP2003045710A - Permanent magnet and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an R2 Fe14 B-based permanent magnet, that has very high coercive force and a sufficiently high remanent magnetic flux density, and that is superior in corrosion resistance. SOLUTION: This permanent magnet contains R (at least one kind of rare- earth element), T (Fe or Fe and Co), and B at the main components. In the magnet, adjacent main phases are substantially isolated from each other by surrounding each main phase, containing RH (at least one kind of heavy rare- earth element) and RL (at least one kind of light rear-earth element) and composed substantially of an RL2 T14 B intermetallic compound having isolated phase, composed substantially of an RH2 T14 B intermetallic compound. In addition, this permanent magnet contains a low-melting point element ML, which lowers the melting point of the RH2 T14 B.

Description

Detailed Description of the Invention

[0001]

The present invention relates to R ₂ T ₁₄ containing R (R is at least one of rare earth elements), T (T is Fe, or Fe and Co) and B.
The present invention relates to a B-based rare earth sintered magnet and a method for manufacturing the same.

[0002]

2. Description of the Related Art As rare earth metal magnets having high performance, Sm-Co magnets having an energy product of 32 MGOe produced by powder metallurgy are mass-produced. However, this material has a drawback that the raw material prices of Sm and Co are high. Among rare earth elements, elements with small atomic weight, for example,
Ce, Pr and Nd are more abundant and cheaper than Sm. Further, Fe is cheaper than Co.

Therefore, in recent years, R ₂ F such as Nd ₂ Fe ₁₄ B magnet has been used.
An e ₁₄ B magnet has been developed, and a sintered magnet is disclosed in JP-A-59-46008. For the magnet by the sintering method, the conventional Sm-Co-based powder metallurgy process (melting → casting → coarse grinding of ingot → fine grinding → press → sintering → magnet)
Can be applied and high magnetic characteristics can be easily obtained. When producing the R-Fe-B magnet by a sintering method, typically by molding a raw material powder of the R ₂ Fe ₁₄ B alloy having the same composition as the magnet to be manufactured, sintering.

In order to obtain a high coercive force in a R ₂ Fe ₁₄ B sintered magnet, for example, as described in Japanese Patent Publication No. 7-78269, the main phases composed of tetragonal intermetallic compounds are not It is necessary that the structure be isolated from each other by the magnetic R-rich phase. Here, the nonmagnetic R-rich phase is a nonmagnetic phase having an R content of 80% or more.

R₂Fe₁₄B magnet characteristics, especially residual magnetic flux density
Degree and coercive force also change with density and crystal grain size
Is most affected by the type and content of R. For example,
When the main component of R is a light rare earth element such as Nd or Pr,
High saturation magnetization (Nd, Pr) ₂Fe₁₄Phase B is the main
Therefore, a high residual magnetic flux density can be obtained. However, (Nd,
Pr)₂Fe₁₄A high coercive force cannot be obtained only with the B phase. one
On the other hand, some of Nd and Pr are heavy rare earth elements such as Dy and Tb.
If replaced, the anisotropic magnetic field H_AIs large (Dy, Tb)₂F
e₁₄Phase B appears. Anisotropic magnetic field H_AIs large, the magnetization is anti
Since it is difficult to roll, coercive force is improved by adding heavy rare earth elements.
Go up.

For example, in Japanese Examined Patent Publication No. 5-31807, R (R is at least one kind of light rare earth element), B and L (L is a heavy rare earth element including Y and Al, titanium, V, Nb, Mo). An anisotropic sintered magnet containing M (at least one of the above) and the balance M (M is Fe or a mixture of Fe and Co), and the element L is contained in the R ₂ M ₁₄ B matrix phase grains. We have proposed rare earth permanent magnets that are unevenly distributed near the grain boundaries.

Further, in JP-A-7-122413, R ₂ T ₁₄ B crystal grains (R is at least 1 of rare earth elements).
And T is a rare earth permanent magnet having a main phase mainly composed of at least one kind of transition metal) and an R rich phase as main constituent phases, wherein at least heavy rare earth elements are contained in the R ₂ T ₁₄ B crystal grains. We are proposing rare earth permanent magnets distributed in three places with high concentration.

Further, Japanese Patent Laid-Open No. 4-155902 discloses an R ₂ T ₁₄ B magnet in which the concentration of Tb + Dy is higher in the vicinity of the crystal grain boundaries of the crystal grains than in the central portion of the crystal grains. Note that T is Fe or Fe and Co. In this publication, a basic composition alloy powder containing at least Rf (Rf is Nd and / or Pr), T and B as main components, and Ra (Ra being Dy and / or Tb) and / or Ra compounds as main components. It is manufactured by molding and sintering a mixture with an additive powder.

However, Dy ₂ Fe ₁₄ B and Tb ₂ Fe ₁₄
Since B has a low saturation magnetic flux density, the residual magnetic flux density decreases as the amount of the heavy rare earth element added increases. Therefore, in order to secure a sufficient residual magnetic flux density for use as a magnet, the content of heavy rare earth elements cannot be increased remarkably, and as a result, there is a limit in improving the coercive force.

Further, in the conventional R ₂ T ₁₄ B magnet, the existence of the non-magnetic R-rich phase surrounding the crystal grains is essential, but this phase is easily corroded and becomes brittle when corroded.
Volume expansion occurs. Therefore, when this phase corrodes,
Even if the crystal grains are not corroded, the crystal grains (main phase) will fall off. Therefore, it has been essential for the conventional R ₂ T ₁₄ B magnet to provide a nickel plating film, a resin film, or the like as a protective film.

[0011]

[0008] The present invention has been made from such circumstances, have a significantly higher and the coercive force and a sufficiently high residual magnetic flux density, yet having excellent corrosion resistance R ₂
It is an object of the present invention to provide a Fe ₁₄ B-based permanent magnet and a method for manufacturing the same.

[0012]

[Means for Solving the Problems] The above-mentioned object is as follows (1)
It is achieved by the present invention of (6). (1) R (R is at least one rare earth element
, T (T is Fe or Fe and Co)
And a permanent magnet containing B as a main component, wherein R_H(R_HIs
At least one heavy rare earth element) and R_L(R_L
Is at least one of light rare earth elements)
Qualitatively R_L2T₁₄The main phase consisting of the B intermetallic compound is substantially
To R_H2T₁₄Surrounded by an isolated phase composed of B intermetallic compound
By doing so, the adjacent main phases are substantially
Is isolated from _H2T₁₄Lowering the melting point of B
Low melting point element M_LA permanent magnet containing. (2) R₂T₁₄Non-magnetic R rich with more R content than B
Phase is absent or said non-magnetic R-rich phase
The permanent magnet according to (1) above, in which the main phase is not surrounded. (3) The volume ratio of the isolated phase to the main phase is 0.0
The permanent magnet according to (1) or (2) above, which is 1 to 0.1. (4) The element content expressed as a mass percentage is 23 ≦ R ≦ 40, 0.8 ≦ B ≦ 1.5, 0.5 ≦ M_L≦ 10, Balance T The permanent magnet according to any one of (1) to (3) above. (5) Molar ratio R_H/ R_LIs 0.01 to 0.15
The permanent magnet according to any one of (1) to (4). (6) Manufacture the permanent magnet according to any one of (1) to (5) above.
A method of making, R_L2T₁₄Mainly including B intermetallic compounds
Compatible powder and R_H, T and B-containing powder for isolated phase
And the low melting point element M_LForming raw material powder containing and
And has a process of sintering at a temperature of 1000 ° C or less
Magnet manufacturing method.

[0013]

OPERATION AND EFFECT The permanent magnet of the present invention has the conventional R ₂ T
_{Like the 14} B sintered magnet, it has the R ₂ T ₁₄ B phase as the main phase. However, in the magnet of the present invention, in place of the non-magnetic R-rich phase, which was essential for the expression of coercive force in the conventional R ₂ T ₁₄ B sintered magnet, the isolated phase substantially consisting of the R _H2 Fe ₁₄ B phase. Have.

As shown in FIGS. 1 and 2 of Japanese Patent Publication No. 5-31807, for example, even in the conventional R ₂ T ₁₄ B sintered magnet, the nonmagnetic R-rich phase is one of the grain boundaries. It may appear to exist only in the department. However, even with such a magnet, it is possible to confirm that the main phase is surrounded by the thin R-rich phase when observed with a transmission electron microscope, for example. As described above, in the conventional R ₂ T ₁₄ B sintered magnet, unless it is surrounded by the R-rich phase, a coercive force practical as a magnet cannot be obtained.

Conventionally, an R ₂ T ₁₄ B sintered magnet to which a heavy rare earth element such as Dy or Tb is added has been known. When a magnet containing a heavy rare earth element is manufactured by an ordinary method, it is general that the heavy rare earth element is almost uniformly dispersed in the crystal grains. Further, as described in JP-A-4-155902, when Nd ₂ T ₁₄ B powder and a powder containing a heavy rare earth element as a main component are mixed and sintered, the heavy rare earth element is included in the crystal grains. An element concentration distribution is formed.

On the other hand, in the magnet of the present invention, the main phase is the R _L2 Fe ₁₄ B phase whose residual magnetic flux density is extremely high because it contains a light rare earth element, and this main phase is surrounded by the isolated phase. It has a structured structure. R _H2 that constitutes the isolated phase
Fe ₁₄ B has an anisotropic magnetic field H _A that is about three times that of Nd ₂ Fe ₁₄ B and has a small magnetization. Therefore, the critical magnetic field required to generate nuclei for generating reverse magnetic domains is large. A large reverse magnetic field is required to generate a reverse magnetic domain in the isolated phase having a large anisotropic magnetic field. Further, since the main phase has a small anisotropic magnetic field, reverse magnetic domains are easily generated in the main phase, but the main phase is surrounded by the isolated phase having a large anisotropic magnetic field.
Therefore, the reverse magnetic domain generated in the main phase cannot cross the isolated phase unless a remarkably large reverse magnetic field is applied. Therefore, the magnet of the present invention is extremely unlikely to cause magnetization reversal. As a result, in the magnet of the present invention, compared with the conventional magnet in which the heavy rare earth element is uniformly distributed in the crystal grains, as compared with the conventional magnet having only the concentration distribution of the heavy rare earth element in the crystal grains. However, the coercive force HcJ becomes extremely high.

Further, in the conventional R ₂ T ₁₄ B sintered magnet, it is indispensable to provide a protective film such as a nickel plating film or a resin film in order to prevent crystal grains from falling off due to corrosion of the non-magnetic R rich phase. It was On the other hand, the isolated phase included in the magnet of the present invention has much better corrosion resistance than the nonmagnetic R-rich phase. Therefore, in the magnet of the present invention, a protective film having lower performance than the conventional one may be used, and when the required corrosion resistance is not so high, it can be used without providing the protective film. Therefore, the manufacturing cost can be reduced.

The magnet of the present invention is manufactured by molding raw material powder and sintering it. In the present invention, in order to form the isolated phase, the raw material powder contains the low melting point element M _L which lowers the melting point of the R _H2 Fe ₁₄ B intermetallic compound forming the isolated phase. As a result, R _H2 Fe ₁₄ having a relatively high melting point is obtained.
B tends to be in a liquid phase even if the sintering temperature is relatively low. By sintering this raw material powder at a lower temperature than before, element diffusion at the time of sintering is suppressed, so that a structure structure in which the main phases are isolated from each other by the isolation phase can be realized.

Since the low melting point element M _L is a non-magnetic component, it reduces the residual magnetic flux density. However magnet of the present invention, unlike the conventional magnet, because it does not contain a non-magnetic R-rich phase to reduce the residual magnetic flux density, despite containing low melting point element M _L, equivalent to the residual and the conventional magnet The magnetic flux density is obtained. Therefore, the magnet of the present invention realizes an extremely high coercive force and a sufficient residual magnetic flux density. Specifically, the intrinsic coercive force HcJ can be set to 1600 kA / m or more, and the residual magnetic flux density can be set to 1.2 T or more.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

Permanent Magnet The permanent magnet of the present invention contains R, T and B as main components.
The element R is at least one kind of rare earth element. In the present invention, the rare earth elements are Y and lanthanoid. The element T is Fe, or Fe and Co.
Is.

The magnet of the present invention contains _RH ( _RH is at least one heavy rare earth element) and _RL ( _RL is at least one light rare earth element). Light rare earth elements include La, Ce, Pr, Nd, Pm, Sm, and Eu, and heavy rare earth elements include Gd, Tb, Dy, Ho, E.
Included are r, Tm, Yb, Lu and Y.

In the magnet of the present invention, the main phase consisting essentially of the R _L2 T ₁₄ B intermetallic compound is surrounded by the isolated phase consisting essentially of the R _H2 T ₁₄ B intermetallic compound, and this main phase is the main phase. It has a structure in which the phases are substantially isolated from each other.
Thereby, high coercive force and high residual magnetic flux density are realized.
To increase the coercive force and the residual magnetic flux density, R
It is preferable to select Nd and / or Pr as _L , and it is preferable to select at least one of Tb, Dy and Ho as R _H.

In the present specification, "substantially R _L2 T
_The “main phase composed of ₁₄ B intermetallic compound” means that the atomic ratio R _H / R _L in the main phase is preferably 0.05 or less, more preferably 0.01 or less. The element distribution in the magnet can be measured by, for example, EPMA (electron probe microanalysis). Also,
The "isolated phase substantially consisting of R _H2 T ₁₄ B intermetallic compound" means that the atomic ratio R _L / _RH in the isolated phase is preferably 0.05 or less, more preferably 0.01 or less. Means

Further, in the present invention, when observing the vicinity of the crystal grain boundary with a transmission electron microscope, it is most preferable that the continuous isolated phase surrounds the main phase in a continuous manner in any arbitrary visual field. However, the number of fields of view to be observed is 10
When the number of fields of view in which the separation phase is interrupted between two adjacent crystal grains is 5 or less when 0 is set, it can be said that “the main phases are substantially separated from each other by the separation phase”, The effects of the present invention are fully realized. In this case, the size of the field of view to be observed is in a range narrower than the crystal grain size.

In order to realize the above structure, the magnet of the present invention has a function of lowering the melting point of the R _H2 T ₁₄ B intermetallic compound, and the element M for lowering the melting point which itself has a relatively low melting point. _{Contains L.} The element M _L lowers the melting point of R _H2 T ₁₄ B means that a part of the elements constituting R _H2 T ₁₄ B, particularly a part of the element T, is replaced by the element M _L , and the R after replacement is R.
Means that the melting point of _H2 T ₁₄ B decreases. The melting point lowering element M _L is preferably Al, Ga, Ag, In, B.
At least one of i, Sn, Pb, Zn, Li, Sb and Si, more preferably Al, Ga, Ag, I.
It is at least one kind of n, Bi and Sn, and more preferably at least one kind of Al, Ga, Bi and Sn.

In the magnet, the element M _L may be uniformly distributed, or may be distributed in the isolated phase or the main phase in a biased manner. However, it may be distributed uniformly or in the isolated phase. It is preferable that they are distributed unevenly in the isolated phase.

In order to realize a high coercive force in the conventional R ₂ T ₁₄ B magnet, it was essential that the main phases be substantially separated from each other by the non-magnetic R rich phase. On the other hand, in the magnet of the present invention, a high coercive force and a high residual magnetic flux density are realized by replacing the non-magnetic R-rich phase with a structure in which the main phases are separated from each other by the isolated phase that functions as a magnet. In the magnet of the present invention, it is most preferable that the non-magnetic R-rich phase does not exist, but some of the grain boundaries (triple point, etc.)
If it does not surround the main phase, such as
A non-magnetic R-rich phase may be present. The non-magnetic R-rich phase that may be contained in the magnet of the present invention means R ₂
It is a nonmagnetic phase having a higher R content than T ₁₄ B, and usually means a phase having an R content of 80% by mass or more.

The volume ratio of the isolated phase to the main phase is preferably 0.01 to 0.15, more preferably 0.025 to.
It is 0.08. Further, the minimum thickness of the isolated phase is preferably 0.01 to 2 μm, more preferably 0.05 to 1 μm. If the volume ratio is too small or the isolated phase is too thin, the isolation of the main phase by the isolated phase tends to be insufficient,
It is difficult to obtain high coercive force. On the other hand, if the volume ratio is too large or the isolation phase is too thick, the proportion of the main phase having a higher magnetization than the isolation phase becomes low, and it becomes difficult to obtain a high residual magnetic flux density. The minimum thickness of the isolated phase can be measured by a transmission electron microscope.

The main phase is a tetragonal system like the crystal grains of the conventional R ₂ T ₁₄ B system sintered magnet, and its average diameter (average crystal grain size) is usually 1 to 80 μm, preferably 1 ~ 50 μm,
More preferably, it is 1 to 20 μm.

Element content in magnet (mass percentage)
Preferably 23 ≦ R ≦ 40, 0.8 ≦ B ≦ 1.5, 0.3 ≦ M L ≦ 10, and the balance T, more preferably 28 ≦ R ≦ 32, 0.8 ≦ B ≦ 1 .2, 0.5 ≦ M _L ≦ 5, and the balance T 2. The molar ratio R _H / R _L in the element R is preferably 0.0 depending on the volume ratio of the isolated phase to the main phase described above.
1 to 0.15, more preferably 0.025 to 0.08.

If the R content is too low, a free α-Fe phase is produced, and the coercive force is lowered. On the other hand, if the R content is too large, the nonmagnetic R-rich phase increases, and the residual magnetic flux density decreases. If the T content is too low, the residual magnetic flux density will be low, and if it is too high, the coercive force will be low. If the B content is too low, a low anisotropy phase having a rhombohedral structure, such as the R ₂ T ₁₇ compound, is generated, and the coercive force becomes low.
If the amount is too large, the B-rich nonmagnetic phase increases, and the residual magnetic flux density decreases. If the M _L content is too small, it becomes difficult to form a liquid phase of R _H2 T ₁₄ B due to the lowering of the melting point, which makes it difficult to form a structure in which the main phases are separated from each other by the separated phase.

By substituting a part of Fe by Co,
The temperature characteristics can be improved without impairing the magnetic characteristics. In this case, if the molar ratio of Co in T exceeds 50%, the magnetic properties deteriorate, so the molar ratio of Co in T is preferably 50% or less, particularly preferably 20% or less.

For the purpose of improving coercive force, productivity, and cost reduction, C, P, S, Ti, V, Cr, M
n, Bi, Nb, Ta, Mo, W, Ge, Zr, Ni,
One or more elements selected from Si, Hf, Cu and the like may be added. The total content of these elements in the magnet is preferably 3% by mass or less. If the total content of these elements is too large, the residual magnetic flux density becomes low.

Manufacturing Method The magnet of the present invention is preferably manufactured by the method described below.

In this method, a permanent magnet is obtained by molding and sintering a raw material powder containing a powder for main phase and a powder for isolated phase. The raw material powder further contains the low melting point element M _L. The main-phase powder includes R _L2 Fe ₁₄ B intermetallic compound. On the other hand, the powder for the isolated phase contains R _H , T and B, but may or may not contain the R _H2 Fe ₁₄ B intermetallic compound. Element M _L in the raw powder
The existing form of is not particularly limited, and may be any of the forms described below.

The element M _L may be contained in the main phase powder and / or the isolation phase powder. Since the element M _L is used to lower the melting point of the isolation phase powder, the element M _L is preferably contained in the isolation phase powder.

Further, the powder containing the element M _L may be independently present in the raw material powder. The powder containing element M _L, may be a powder consisting of elements M _L, it may be a powder composed of an alloy containing an element M _L, a mixture of two or more powder selected from these May be As the alloy containing the element M _L , it is preferable to use at least one of R-M _L alloy and T-M _L alloy.

On the surface of the alloy particles constituting the powder for the main phase and / or on the surface of the alloy particles constituting the powder for the isolation phase, a metal containing M _L (a metal consisting of element M _L or element M _{L) is formed.
L-} containing alloy) may be applied. To deposit the _ML- containing metal on the surface of the alloy particles, a vapor phase forming method such as a vapor deposition method or a method of applying a mechanical strain force can be used.

In the method of applying mechanical straining force, mechanical straining force is applied to a mixture of particles made of _ML- containing metal and the alloy particles by a grinding medium such as metal balls or ceramic balls. When the spreadability of the _ML- containing metal used is low, the particles made of the _ML- containing metal are fixed on the surface of the alloy particles while maintaining the particle shape. Further, when the M _L- containing metal has a high spreadability, the M _L- containing metal is spread and covers at least a part of the surface of the alloy particles.

Since the element M _L is used for lowering the melting point of the isolation phase powder, the M _L- containing metal is preferably deposited on the surface of the alloy particles constituting the isolation phase powder.

Among the above-mentioned respective methods, a method of incorporating the element M _L into the powder for the isolation phase, and a method of using an M _L- containing metal having high spreadability on the surface of the particles constituting the isolation powder by mechanical strain. The method of deposition is preferred. When the element M _L is contained in the powder for the isolation phase, the powder for the isolation phase is easily liquefied at a relatively low temperature during sintering, and the sintering reaction proceeds. on the other hand,
When the M _L- containing metal is deposited on the surface of the alloy particles that make up the isolation phase powder, the M _L- containing metal melts during sintering and reacts with the isolation phase powder to lower the melting point of the isolation phase powder. To do. As a result, the powder for the isolated phase easily becomes a liquid phase at a relatively low temperature,
The sintering reaction proceeds.

As the powder for the isolated phase, only a powder having a composition centered on R ₂ T ₁₄ B (atomic ratio) (hereinafter sometimes referred to as R ₂ T ₁₄ B powder) may be used, but different powders are used. You may use the powder of 2 or more types of composition. For example, in the case of using a powder containing the element M _L in addition to the main phase powder and the isolated phase powder, (1) R ₂ T ₁₄ is used as the isolated phase powder.
A combination of B powder and RB alloy powder, (2) R ₂ T
₁₄ It is preferable to use a combination of B powder, RB alloy powder and TB alloy powder, and (3) a combination of RB alloy powder and TB alloy powder.

The powder for the main phase and the powder for the isolated phase may be manufactured in the same manner as the raw material powder to be sintered used in manufacturing the conventional R ₂ T ₁₄ B magnet. That is, these powders can be obtained by crushing an alloy produced by a strip casting method or a mold casting method. The pulverization method is not particularly limited, but generally, it may be roughly pulverized by a disc mill or the like to a particle size of about 10 to 100 μm, and then finely pulverized by a jet mill or the like to a particle size of about 0.5 to 10 μm. In addition, hydrogen occlusion pulverization can also be performed. In hydrogen storage and crushing, alloy strips and alloy ingots roughly crushed to about 30 mm square are embrittled by performing hydrogen storage and hydrogen release at least once, and then mechanically crushed and finely crushed as described above. To do. The raw material powder may be obtained by producing finely pulverized powder for each of the main phase alloy and the isolated phase alloy and mixing them, or by mixing coarsely pulverized powder of each alloy and finely pulverizing the mixture. You may obtain by doing.

The composition of the powder for the main phase and the composition of the powder for the isolated phase are such that the overall composition after sintering falls within the preferable range described above, and in the powder for the main phase, the R ₂ T ₁₄ B intermetallic compound is used. However, it is preferable that both powders have 23 ≦ R ≦ 40, 0.8 ≦ B ≦ 1.5, and the balance T. However, in the alloy for the main phase, it is more preferable that the R content is relatively small in order to suppress the generation of the R-rich phase. Specifically, 28 ≦ R ≦ 32, 0.8 ≦ B ≦ 1. _{2, 1 ≦ M L ≦ 5} , it is desirable that the balance T. On the other hand, in the grain boundary phase alloy, it is more preferable that the R content is relatively large in order to lower the melting point. Specifically, 28 ≦ R ≦ 35, 0.8 ≦ B ≦ 1.2, 1 ≦ It is desirable that M _L ≦ 5 and the balance T. In the case of incorporating the M _L powder for the main-phase powder and / or quarantine phase, it may be added to M _L in a manner to replace the element T. Further, it is preferable that the total amount of the element R is the element R _L in the main phase powder and the total amount of the element R is the element R _H in the isolated phase powder.

Next, the raw material powder is molded. Molding is performed in a magnetic field. Magnetic field strength is 800 kA / m or more, molding pressure is 50
It is preferably about 500 MPa.

After molding, it is sintered. Sintering temperature (stable temperature)
Is 1000 ° C. or lower, preferably 900 to 980 ° C. The stable temperature is a temperature in a stable temperature region sandwiched between a temperature raising process and a temperature lowering process. The time for maintaining the stable temperature is preferably 0.1 to 100 hours, more preferably 2 hours.
0 to 80 hours. As described above, the present invention is characterized in that in the sintering step, heating is performed at a lower temperature and for a longer time than in the conventional case. If the sintering temperature is too low or the sintering time is too short, the powder for the isolation phase will be difficult to liquefy,
Sintering does not proceed sufficiently, and both the residual magnetic flux density and the coercive force tend to be low. On the other hand, if the sintering temperature is too high or the sintering time is too long, the diffusion of elements proceeds, and as a result, the function as the isolation phase and the function as the main phase become low.

After sintering, it is preferable to perform an aging treatment.
The aging treatment is preferably performed at a temperature of 450 ° C. or higher and a sintering temperature or lower, more preferably 550 to 950 ° C. for 0.1 to 10 ° C.
It is performed by heating for 0 hours. The coercive force is further improved by the aging treatment. The aging treatment may be composed of multi-step heat treatment. For example, in the aging treatment consisting of two-step heat treatment, the first-step heat treatment is performed at a temperature of 700 ° C. or higher and lower than the sintering temperature for 0.1 to 50 hours, and the second-step heat treatment is performed for 50 hours.
It is preferable to carry out the treatment at 0 to 700 ° C. for 0.1 to 100 hours.

The steps of crushing, mixing, molding, sintering and aging treatment are preferably carried out in a non-oxidizing gas atmosphere such as Ar gas or N ₂ gas or in vacuum.

The use of the magnet of the present invention is not particularly limited, and the magnet of the present invention can be applied to various devices such as a motor and a speaker.

[0051]

Example Sample No. 1 A powder for main phase was manufactured by the following procedure. First, an alloy strip composed of Nd: 29% by mass, B: 1.05% by mass, Fe: the balance and a trace amount of unavoidable impurities was manufactured by a strip casting method. This alloy strip has a thickness of 0.3-0.6 mm and a columnar R
_It contained ₂ T ₁₄ B intermetallic compound crystals. Analysis by X-ray diffraction revealed no diffraction lines derived from other phases, and observation by EPMA revealed a small amount of non-magnetic R-rich phase.

Hydrogen was absorbed in this alloy strip at around room temperature, and the temperature was increased to dehydrogenate to embrittle the alloy strip, and then coarsely pulverized by a disc mill to a size that passed through an opening sieve of 350 μm. Then
Average particle size is 5μ by jet mill using nitrogen gas
Finely pulverized to m to obtain a main phase powder.

A powder for the isolated phase was manufactured by the following procedure. First, an alloy strip composed of Dy: 32.5% by mass, B: 1.13% by mass, Co: 3% by mass, Fe: the balance and trace amounts of unavoidable impurities was manufactured by a strip casting method. This alloy strip has a thickness of 0.3-0.6 mm and a columnar R
_It contained ₂ T ₁₄ B intermetallic compound crystals. Analysis by X-ray diffraction showed no diffraction lines derived from other phases. By using this alloy strip and pulverizing it in the same manner as in the production of the powder for the main phase, an average particle size of 3.5
A μm powder for the isolated phase was obtained.

This powder for the isolated phase was placed in a rotary kiln capable of controlling the atmosphere, and Al was placed in the rotary kiln.
By introducing the steam, an Al film was formed on the surface of the alloy particles constituting the powder for the isolation phase. The amount of Al deposited on the surface of the alloy particles was 10 mass% with respect to the powder for the isolation phase. It should be noted that this Al is an element M for lowering the melting point in the present invention.
Functions as _L.

Next, both powders were mixed by a V mixer so that the powder for the main phase / the powder for the isolated phase adhered with Al = 9/1 (mass ratio), to obtain a raw material powder. The raw material powder was molded in a magnetic field of 1.2 T by applying a pressure of 196 MPa in a direction orthogonal to the direction of the magnetic field. The obtained compact was sintered by holding it at 980 ° C. for 29 hours in an Ar gas atmosphere of less than 1 atm. The obtained sintered body was aged at 450 ° C. for 12 hours to obtain a sintered magnet sample.
I got No.1.

The composition of sample No. 1 was: Nd: 26.1% by mass, Dy: 3.0% by mass, B: 1.05% by mass, Co: 0.27% by mass, Al: 0.91% by mass. , Fe: The balance, which further contains a trace amount of unavoidable impurities. The cross section of sample No. 1 shows the EPMA and X
It was examined by line diffraction and transmission electron microscopy. As a result, a crystal grain (main phase) and a grain boundary phase (isolation phase) exist, and the main phase is substantially composed of Nd ₂ T ₁₄ B intermetallic compound,
The isolated phase is substantially composed of Dy ₂ T ₁₄ B intermetallic compound, a small amount of non-magnetic R-rich phase is present at the triple points of the grain boundaries, and Al is present in the isolated phase at a higher concentration than the main phase. It was found to have a distributed tissue structure. The average crystal grain size was 11 μm, the minimum thickness of the isolated phase was 0.12 μm, and the volume ratio of the isolated phase to the main phase was 0.07.
In addition, in 100 fields of view of the transmission electron microscope, the field of view in which the isolation phase was interrupted between two adjacent crystal grains was 3.

Sample No. 2 The powder for the isolation phase used in the production of Sample No. 1 and the Al powder having an average particle size of 1 μm were put into a barrel processing machine together with a stainless steel ball having a diameter of 5 mm, and were placed in an Ar atmosphere. Vibration was applied at. As a result, Al particles were deposited on the surfaces of the alloy particles constituting the powder for the isolated phase. The amount of Al deposited on the surface of the alloy particles was 10.5 mass% with respect to the powder for the isolation phase.

Sintered magnet sample No. 2 was obtained in the same manner as sample No. 1 except that the powder for the isolated phase coated with Al was used. When the cross section of Sample No. 2 was examined in the same manner as Sample No. 1, it was found to have the same structure structure as Sample No. 1. Also, the average crystal grain size is 8 μm
The minimum thickness of the isolated phase was 0.08 μm, and the volume ratio of the isolated phase to the main phase was 0.07. Further, in 100 fields of view of the transmission electron microscope, the field of view in which the isolation phase was discontinued between two adjacent crystal grains was 4.

Sample No. 3 Dy: 30% by mass, B: 1.13% by mass, Co: 3% by mass, Al: 10% by mass, Fe: An alloy strip consisting of the balance and trace amounts of unavoidable impurities was strip cast. It was manufactured by the method. This alloy strip has a thickness of 0.3-0.6 mm and a columnar R
_It contained ₂ T ₁₄ B intermetallic compound crystals. Analysis by X-ray diffraction showed no diffraction lines derived from other phases. It is considered that Al replaces the Fe site of the R ₂ T ₁₄ B intermetallic compound crystal. The alloy strip was pulverized in the same manner as in the production of the powder for the main phase of Sample No. 1 to obtain the powder for the isolated phase having an average particle diameter of 3.6 μm.

The powder for the isolated phase and the powder for the main phase used in the production of Sample No. 1 were prepared as follows: powder for the main phase / powder for the isolated phase =
The raw material powder was obtained by mixing with a V mixer so as to be 9/1 (mass ratio). Sintered magnet sample No. 3 was obtained in the same manner as sample No. 1 except that this raw material powder was used.

The composition of sample No. 3 was as follows: Nd: 26.1% by mass, Dy: 3.0% by mass, B: 1.06% by mass, Co: 0.3% by mass, Al: 1.0% by mass. , Fe: The balance, which further contains a trace amount of unavoidable impurities. When the cross section of Sample No. 3 was examined in the same manner as Sample No. 1, it was found to have the same structure structure as Sample No. 1. The average crystal grain size was 11 μm, the minimum thickness of the isolated phase was 0.14 μm, and the volume ratio of the isolated phase to the main phase was 0.09. In addition, 1 of transmission electron microscope
The number of visual fields in which the isolated phase was discontinued between two adjacent crystal grains was 00 in the 00 visual field.

Sample No. 4 (comparative) Nd: 29.8% by mass, Dy: 2.8% by mass, B: 1.06% by mass, Fe: An alloy strip consisting of the balance was manufactured by the strip casting method. This alloy strip has a thickness of 0.3-
It was 0.6 mm and contained columnar R ₂ T ₁₄ B intermetallic compound crystals. Analysis by X-ray diffraction showed no diffraction lines derived from other phases, and observation by EPMA showed a non-magnetic R-rich phase. The alloy strip was pulverized in the same manner as in the production of the powder for main phase of Sample No. 1 to obtain a raw material powder having an average particle size of 5.5 μm.

Next, this raw material powder was sample No. 1
Molding was performed in a magnetic field under the same conditions as in manufacturing. The obtained molded body was heated to 1050 in an Ar gas atmosphere of less than 1 atm.
Sintering was carried out by holding at 4 ° C for 4 hours. The obtained sintered body was aged at 450 ° C. for 12 hours to obtain a sintered magnet sample No. 4.

When the cross section of Sample No. 4 was examined in the same manner as in Sample No. 1, the main phase composed of R ₂ T ₁₄ B was surrounded by the nonmagnetic R rich phase, and the main phases were nonmagnetic R rich phase. It was a structure isolated by.

Evaluation The coercive force HcJ and the residual magnetic flux density Br of each of the above samples were measured at room temperature. Also, 80 ° C-90%
It was stored under constant temperature and humidity conditions of RH, and the time until rusting was examined. The results are shown in Table 1.

[0066]

[Table 1]

From Table 1, the effect of the present invention is clear.
In other words, Sample Nos. 1 to 3 have significantly higher coercive force HcJ and extremely good corrosion resistance as compared to Sample No. 4 even though the contents of heavy rare earth elements are the same. ing. Moreover, the residual magnetic flux density Br
Is almost inferior.

Claims (6)

[Claims] 1. R (R is at least one rare earth element)
, T (T is Fe, or Fe and Co)
And a permanent magnet containing B as a main component, R_H(R_HIs at least one of the heavy rare earth elements) and
And R_L(R_LIs at least one kind of light rare earth element)
Contains and substantially R_L2T₁₄Main phase consisting of B intermetallic compound
But substantially R_H2T₁₄In the isolation phase consisting of B intermetallic compound
Therefore, by being surrounded, adjacent main phases are mutually
Is substantially isolated, and R _H2T₁₄Melting point of B
Element for lowering melting point M_LA permanent magnet containing. 2. A non-magnetic R having a higher R content than R ₂ T ₁₄ B.
The permanent magnet according to claim 1, wherein a rich phase does not exist, or the main phase is not surrounded by the non-magnetic R rich phase. 3. The permanent magnet according to claim 1, wherein the volume ratio of the isolated phase to the main phase is 0.01 to 0.1. 4. A element content expressed in percent by mass is, 23 ≦ R ≦ 40, 0.8 ≦ B ≦ 1.5, 0.5 ≦ M L ≦ 10, of claims 1 to 3 the balance T One of the permanent magnets. 5. The permanent magnet according to claim 1, wherein the molar ratio R _H / R _L is 0.01 to 0.15. 6. The method for producing a permanent magnet according to claim 1, wherein the main phase powder contains R _L2 T ₁₄ B intermetallic compound, and R _H and T
A method for producing a permanent magnet, comprising a step of molding a raw material powder containing a powder for an isolated phase containing B and B and the low melting point element M _L and sintering the powder at a temperature of 1000 ° C. or less.