JP2003328092A - Rare earth alloy powder for bonded magnet, compound for bonded magnet, and bonded magnet using the compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rare earth alloy powder excellent in filling properties and/or moldability and used for a bonded magnet excellent in magnetic properties; a compound for the bonded magnet; and the bonded magnet prepared by using the compound. <P>SOLUTION: The alloy powder has a composition represented by the composition formula: (Fe<SB>1-m</SB>T<SB>m</SB>)<SB>100-x-y-z</SB>Q<SB>x</SB>R<SB>y</SB>M<SB>z</SB>(wherein T is at least either Co or Ni; Q is at least either B or C; R is at least one rare earth element substantially not containing La and Ce; M is a metallic element selected from among Ti, Zr, and Hf; 10<x≤20 atom.%; 6<y<10 atom.%, 0.1≤z≤12 atom.%; and 0≤m≤0.5) and contains at least two kinds of ferromagnetic crystal phases. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rare earth alloy powder for bonded magnets, a compound for bonded magnets, and a bonded magnet using the same.

[0002]

2. Description of the Related Art At present, bond magnets are used in various electric devices such as motors, actuators, speakers, meters, focus convergence rings and the like. The bonded magnet is a magnet manufactured by mixing alloy powder for magnet (magnet powder) and a binder (resin or low melting point metal), and molding and solidifying the mixture.

Conventionally, Ma has been used as a magnetic powder for bonded magnets.
Fe-RB magnet powder sold by gnequench International (hereinafter abbreviated as "MQI"),
So-called MQ powder is widely used. MQ powder is generally Fe _100-ab B _a R _b (Fe is iron, B is boron, R is
Pr, Nd, Dy, and at least one kind of rare earth element selected from the group consisting of Tb), and a and b in the composition formula are 1 atomic% ≤ a ≤ 6 atomic%,
And the content of 10 atomic% ≤ b ≤ 25 atomic% are satisfied, and the R content b is high.

Conventional alloy powders for bonded magnets represented by MQ powders are produced by rapidly solidifying molten raw material alloys (that is, "molten alloy melt"). This liquid quenching method (melt-quenching)
As a method), a melt-spining method (typically a single roll method) is often used. The single roll method is a method in which the molten alloy is cooled and solidified by bringing the molten alloy into contact with a rotating cooling roll. In the case of this method, the shape of the quenched alloy extends in a ribbon shape along the surface circumferential velocity direction of the cooling roll. The quenched alloy ribbon thus produced has a mean grain size of 300 μm or less (typically about 150 μm) after heat treatment.
m) to obtain a rare earth alloy powder for a permanent magnet. Below, the above-mentioned rare earth alloy powder produced by the liquid quenching method will be simply referred to as "conventional quenching magnet powder" and will not include the nanocomposite magnet powder described below.

[0005] Conventional quenching magnet powder and resin (here, containing rubber or elastomer) are mixed,
A compound for bonded magnets (hereinafter, simply referred to as "compound") is prepared. In this compound,
Additives such as lubricants and coupling agents may be mixed.

This compound is molded into a desired shape by, for example, compression molding, extrusion molding or injection molding to obtain a bonded magnet as a molded body of permanent magnet (also referred to as "permanent magnet body"). Further, since the bonded magnet produced by compression molding or extrusion molding has a low binder content, it may be further surface-treated in order to protect the magnet powder from corrosion.

On the other hand, in recent years, nano-composite magnets of iron-based rare earth alloys (especially Fe—R—B type) (referred to as “exchange spring magnets”) have been used as magnet powders used for bonded magnets because of their relatively low cost. It is sometimes used.) Powder is being used. The Fe-RB-based nanocomposite magnet is, for example, Fe ₃ B or Fe ₂₃ B ₆ or the like, which is a soft magnetic phase of microcrystals of iron-based boride and R ₂ which is a hard magnetic phase.
This is an iron-based alloy permanent magnet in which Fe ₁₄ B phase microcrystals are uniformly distributed in the same metallic structure, and both are magnetically coupled by exchange interaction (for example, Japanese Patent Application No. 11-362103 by the applicant of the present application). No. and Japanese Patent Application 2000-371
788).

The nanocomposite magnet exhibits excellent magnetic characteristics by including magnetic coupling (exchange interaction) between the soft magnetic phase and the hard magnetic phase even though it contains the soft magnetic phase. Further, as a result of the presence of the soft magnetic phase containing no rare earth element R such as Nd, the content of the rare earth element R can be suppressed low as a whole (typically, the content ratio of R is 4.5 atom%). This is advantageous in reducing the manufacturing cost of the magnet and stably supplying the magnet. Further, since the content ratio of R active to oxygen is low, it is also excellent in corrosion resistance. In addition,
This nanocomposite magnet is also produced by the liquid quenching method. This nanocomposite magnet is pulverized by a predetermined method to obtain nanocomposite magnet powder.

The magnetic characteristics of the bonded magnet depend on the magnetic characteristics of the magnet powder contained in the bonded magnet and the filling rate thereof. Therefore, in order to improve the magnetic characteristics of the bonded magnet, it has been studied to improve the filling rate of the magnet powder.

Further, in recent years, with the miniaturization and higher performance of electric equipment, the demand for small and high-performance magnets has been increasing more and more. For example, a ring magnet for a spindle motor has an outer diameter of 15 mm to 20 mm and an inner diameter of 13 mm.
.About.18 mm, thickness of about 1 mm to 2 mm, or as a ring magnet for a stepping motor, a product having an outer diameter of 4 mm to 10 mm, an inner diameter of 2 mm to 8 mm, and a thickness of about 0.5 mm to 1.5 mm. Demand is increasing.

[0011]

However, as a result of the study by the present inventors, it was found that the above-mentioned conventional quenched magnet powder and conventional nanocomposite magnet powder have the following problems.

Conventional quenched magnet powders represented by MQ powders typically have a roll surface peripheral velocity of 15 m / sec or more and a thickness of 50 μm or less (typically about 20 μm to about 4).
It is manufactured by producing a quenched alloy ribbon of 0 μm), heat-treating the quenched alloy ribbon, and then pulverizing the quenched alloy ribbon to an average particle diameter of 300 μm or less (typically about 150 μm). The magnet powder thus produced has a flat particle shape, and the powder particle has an aspect ratio of less than 0.3. The aspect ratio represents the size in the minor axis direction / the size in the major axis direction.

Although this magnet powder has excellent magnetic properties, the packing ratio of the magnet powder (density of bonded magnet / density of powder particles) is the highest among the various molding methods. Even with the compression molding method used, the maximum is usually about 80%.

For example, when a conventional quenched magnet powder is used and a bonded magnet having a packing ratio of the magnet powder of more than 80% is molded by a compression molding method, the amount of resin entering the gap between the magnet powders is reduced, so that the porosity is reduced. , And the magnetic particles may shed. As a result, the magnetic characteristics are significantly deteriorated by the oxidation under the use environment. In order to prevent this deterioration of magnetic properties, voids are filled (sometimes called "sealing treatment") or a protective film of sufficient thickness is formed on the surface (surface treatment) in a later step. Need to do. Also, forming a thick protective film such as resin by surface treatment means increasing the thickness of the non-magnetic layer on the surface of the magnet, which widens the magnetic gap in the magnetic circuit and lowers the utilization efficiency of magnetic energy. I will let you. Further, in the process of producing and molding the compound, particles of the magnet powder may be destroyed and a new surface may be exposed, resulting in a decrease in corrosion resistance and a decrease in magnetic property due to surface oxidation.

In order to improve the filling rate by using the conventional quenched magnet powder, an attempt has been made to control the particle size distribution of the quenched magnet powder, as disclosed in, for example, Japanese Patent Application Laid-Open No. 63-155601. However, the filling rate has not been realized yet.

Further, as a result of the study by the present inventors, the conventional rapidly quenched magnet powder is easily oxidized due to the high content of rare earth elements, and the smaller the particle size, the greater the degree of deterioration of the magnetic properties due to the oxidation ( For example, in the case of MQP-B (maximum particle size of 300 μm or less), the residual magnetic flux density B _r (0.79T) of powder particles of 53 μm or less is more than 106 μm 12
Residual magnetic flux density B _r of powder particles of 5 μm or less (0.90
It is less than 90% of T). ), The magnetic properties of the magnet powder itself deteriorate as the fraction of small particles increases. In order to suppress the deterioration of magnetic properties due to this oxidation, it is necessary to suppress the fraction of small particles contained in the magnet powder for bonded magnets, and as a result, the particle size distribution adjustment to improve the packing rate is required. There was also a limit.

Further, since the conventional quenched magnet powder contains many particles having a relatively large particle size, it is difficult to form a small magnet, which has been in high demand in recent years, and the large particles are likely to be shed. is there.

In order to improve the moldability (particularly the fluidity) of the conventional quenched magnet powder, Japanese Patent Laid-Open No. 315174/1993 proposes a method using magnet powder produced by the gas atomizing method. According to the above-mentioned publication, the particles of the magnet powder produced by the gas atomization method are close to granular (spherical), so that the fluidity can be improved by adding this magnet powder to the conventional quenched magnet powder. However, since the gas atomization method has a slower cooling rate than the liquid quenching method described above, it is difficult to produce magnet powder exhibiting sufficient magnetic properties with a conventional composition, and it is said that the method is industrially applicable. hard.

On the other hand, the conventional Fe-R-B based nanocomposite magnet powder has a relatively low content of rare earth elements,
The volume ratio of the hard magnetic phase is typically 30% or less. Therefore, the magnetic properties (for example, coercive force H _cJ ) are lower than those of conventional quenching magnet powders (MQ powders, etc.), so that there is a problem that a bond magnet having sufficient magnetic properties cannot be obtained. For example, a hard disk drive device (HDD) ) Motor could not be applied.

The present invention has been made in view of the above points, and its main purpose is to provide a rare earth alloy powder and a bond magnet which are used in a bond magnet having excellent filling properties and / or moldability and magnetic properties. It is to provide a compound and a bonded magnet using the compound.

[0021]

The rare earth alloy powder for a bonded magnet according to the present invention has a composition formula (Fe _1-m T _m ) _{100-xy- z.}
Q _x R _y M _z (T is at least one element selected from the group consisting of Co and Ni, Q is B or at least one element selected from the group consisting of B and C, and R is La and Ce.
One or more rare earth elements substantially free of, M is Ti,
A metal element selected from the group consisting of Zr and Hf, wherein at least one metal element that always contains Ti and the composition ratios x, y, z, and m are 10 <x ≦ 2, respectively.
0 atomic%, 6 <y <10 atomic%, 0.1 ≦ z ≦ 12 atomic%, and 0 ≦ m ≦ 0.5),
In addition, the average crystal grain size of the hard magnetic phase is 10 nm or more and 200 n
m or less, the average crystal grain size of the soft magnetic phase is 1 nm or more and 100 n
In the range of m or less, powder particles containing two or more kinds of ferromagnetic crystal phases are included, and the particle size distribution has a particle size of 10
Has a first peak in the range of more than 6 μm and 150 μm or less,
The aspect ratio of the powder particles having a particle size of more than 106 μm is in the range of 0.3 or more and 1.0 or less.

In the particle size distribution, it is preferable that the particle size has a second peak in the range of 53 μm or less.

The average particle diameter of the powder particles is more than 53 μm 12
It is preferably within the range of 5 μm or less.

The average thickness of the powder particles having a particle size of more than 106 μm is preferably in the range of 50 μm or more and 120 μm or less.

More preferably, the aspect ratio of the powder particles is 0.4 or more.

It is preferable that the powder particles are produced by a strip casting method.

More preferably, the powder particles are produced by crushing an alloy ribbon having an average thickness of 50 μm or more and 120 μm or less obtained by a strip casting method.

The compound for bonded magnets of the present invention is characterized by containing any one of the above-mentioned rare earth alloy powder for bonded magnets and a binder.

The bonded magnet of the present invention is characterized by being formed using the above compound for a bonded magnet.
The bonded magnet is preferably formed using a compression molding method.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION The rare earth alloy powder for bonded magnets (hereinafter, abbreviated as “magnetic powder”) according to the present invention has a first peak in a particle size distribution within a range of more than 106 μm and 150 μm or less, The Ti-containing nanocomposite magnetic powder has an aspect ratio of powder particles having a particle size of more than 106 μm in the range of 0.3 or more and 1.0 or less. For details of the Ti-containing nanocomposite magnetic powder, the applicant of the present invention,
Japanese Patent No. 3264664 and Japanese Patent Application No. 2001-3280
No. 85.

The Ti-containing nanocomposite magnetic powder has a composition formula (Fe _1-m T _m ) _100-xyz Q _x R _y M _z (T is Co and N
at least one element selected from the group consisting of i, Q is at least one element selected from the group consisting of B or B and C, and R is at least one rare earth element substantially free of La and Ce The element M is a metal element selected from the group consisting of Ti, Zr, and Hf, and at least one metal element that always contains Ti, the composition ratios x, y, z, and m are
10 <x ≦ 20 atomic%, 6 <y <10 atomic%, 0.1 ≦ z ≦ 12 atomic%, and 0 ≦ m ≦ 0.5, respectively.
And having two or more types of ferromagnetic crystal phases, the hard magnetic phase has an average crystal grain size of 10 nm to 200 nm, and the soft magnetic phase has an average crystal grain size of 1 nm to 100 nm. Have an organization within the range of. Ti
In the contained nanocomposite magnetic powder, the composition ratios x, y, z, and m in the above composition formula are 10 <x <17, respectively.
Atomic%, 7 ≦ y ≦ 9.3 atomic%, 0.5 ≦ z ≦ 6 atomic%
Is preferably satisfied, and more preferably 8 ≦ y ≦ 9.0.

Since the Ti-containing nanocomposite magnetic powder according to the present invention has the composition and structure as described above,
The hard magnetic phase and the soft magnetic phase are magnetically coupled by exchange interaction, and despite the relatively low content of rare earth elements, they have excellent magnetic properties equivalent to or better than those of conventional quenched magnet powders. In addition, it has excellent magnetic properties (especially high coercive force H _cJ ) as compared with the conventional nanocomposite magnet powder having Fe ₃ B phase as a main phase. Specifically, the Ti-containing nanocomposite magnetic powder according to the present invention has a maximum energy product (BH) max of 70 kJ / m ³ or more, a coercive force H _{cJ of} 700 kA / m or more, and a residual magnetic flux density B _{r of} 0.7.
T and above can be realized, and the maximum energy product (B
H) max: 90 kJ / m ³ or more, coercive force H _cJ : 800
A kA / m or more and a residual magnetic flux density B _r : 0.8T or more can be realized.

As described above, since the Ti-containing nanocomposite magnetic powder has magnetic characteristics equal to or higher than those of the conventional quenched magnet powder, it is used as the magnetic powder for the bonded magnet instead of the conventional quenched magnet powder (for example, MQ powder). be able to. Of course, as the magnetic powder for the bonded magnet, it is preferable to use only the Ti-containing nanocomposite magnetic powder, but conventional quenching magnet powder or the like may be mixed to the extent that the characteristics of the Ti-containing nanocomposite magnetic powder are not impaired.

Furthermore, since the Ti-containing nanocomposite magnetic powder has its composition and structure, it has a characteristic that its magnetic characteristics have little dependence on particle size. For example,
The residual magnetic flux density B _r of particles of 53 μm or less is substantially the same (95% or more) as the residual magnetic flux density B _r of particles of more than 106 μm and 250 μm or less. The Ti-containing nanocomposite magnetic powder has a relatively low content of the rare earth element R, and has a small boride phase dispersed so as to surround the R ₂ Fe ₁₄ B phase, and Ti has a high affinity with boron. Therefore, the boride phase contains more Ti than the other phases. As a result, the Ti-containing nanocomposite magnetic powder is superior in oxidation resistance to the conventional quenched magnet powder. As described above, since the conventional quenched magnet powder contains a relatively large amount of rare earth element R, it is easily oxidized, and the smaller the particle size, the more marked the deterioration of the magnetic properties due to the oxidation of the powder particle surface. The composite magnetic powder has little deterioration in the magnetic properties due to oxidation, and has little dependence on the particle size of the magnetic properties. Therefore, the adjustment of the particle size distribution is not limited by the magnetic properties,
It is possible to obtain an optimum particle size distribution for improving moldability.

As will be described later with reference to Examples, Ti-containing nanocomposite magnetic powders having various particle size distributions were prepared and their formability and magnetic properties were examined. As a result, in the particle size distribution, the particle size was more than 106 μm and 150 μm. It was found that the Ti-containing nanocomposite magnetic powder having the first peak in the following range and having the aspect ratio of the powder particles having a particle size of more than 106 μm in the range of 0.3 or more and 1.0 or less is excellent. It was

The Ti-containing nanocomposite magnetic powder having the above-mentioned particle size distribution has a first peak in the range of 150 μm to 500 μm, as disclosed in JP-A-63-155601, and has a particle size of 2 μm to 40 μm. Moldability is superior to that having the second peak in the range. Further, the mass fraction of particles having a particle size of more than 150 μm (the specific gravity of the magnetic powder used here (about 7.45 g / cm ³ ) is almost equal, so the mass fraction is equal to the volume fraction) can be made relatively small. Therefore (for example, 40% by mass or less, preferably 30% by mass or less), it is preferably used for manufacturing a small magnet. In addition, it is possible to suppress a defect that occurs when the magnetic powder is shed from the bonded magnet.

Particularly, in order to suppress shedding and the like in a small magnet, the maximum particle size of the Ti-containing nanocomposite magnetic powder is preferably 250 μm or less, more preferably 215 μm or less. Furthermore, it is preferable to adjust the average particle size of the powder particles to be in the range of more than 53 μm and 125 μm or less. The Ti-containing nanocomposite magnetic powder having such a particle size distribution is suitably used for manufacturing the above-mentioned particularly small ring magnet.

The particle size in the present specification is JIS
It shall be determined by sorting with a standard sieve of 8801. Further, the minimum particle size of the particles contained in the Ti-containing nanocomposite magnetic powder is not particularly limited, but in the manufacturing process of the Ti-containing nanocomposite magnetic powder, ultrafine powder particles having a particle size of 1 μm or less are easily removed, and , Preferably removed.

By adjusting the particle size distribution of the Ti-containing nanocomposite magnetic powder according to the present invention so that the particle size has a second peak in the range of 53 μm or less, the formability can be further improved. This is because a relatively small particle forming the second peak is formed in a gap formed by relatively large particles forming the first peak (particles having a particle size of more than 106 μm are also referred to as “first particles”). It is considered that particles (particles having a particle size of 53 μm or less are sometimes referred to as “second particles”) are efficiently filled.

The effect of improving the formability by this particle size distribution is that the aspect ratio (minor axis / major axis) of the first particles is 0.3.
It is remarkably obtained when it is 1.0 or more. That is, even if the sizes of the first particles and the second particles are controlled, if the aspect ratio of the first particles (particles having a particle size of more than 106 μm) is less than 0.3, the gap formed by the first particles Is considered to be a flat shape and it becomes difficult for the second particles to be filled in the gaps. Of course, the aspect ratio of the second particles is also preferably 0.3 or more and 1.0 or less. Since the second particles have a smaller particle size than the first particles,
It is easy to make the aspect ratio of the particles equal to or higher than the aspect ratio of the first particles.

As will be described below, the Ti-containing nanocomposite magnetic powder of the present invention uses the strip casting method to produce particles having an aspect ratio of 0.3 or more, or 0.4 or more with high productivity. be able to. For details of the method for producing the Ti-containing nanocomposite magnetic powder using the strip casting method, see, for example, Japanese Patent Application No.
No. 001-342692.

The Ti-containing nanocomposite magnetic powder used in the magnetic powder for a bonded magnet according to the present invention has a slower cooling rate (10 ² to 10 ⁶ ° C / ° C) than that of the conventional quenched magnet powder due to the function of Ti, as will be described later. It can also be produced by cooling the molten alloy in seconds), so that the above metallographic structure can be obtained even if an alloy having a plate thickness thicker than the conventional one is produced using the strip casting method. The quenched alloy of the Ti-containing nanocomposite used in the present invention is composed of fine crystal grains, so that it easily breaks along a random orientation, and is equiaxial (aspect ratio of 0.3 or more). Powder particles (close to 1) are likely to be generated.

For example, using the strip casting method,
Alloy with a thickness of 50 μm or more and 120 μm or less (alloy ribbon)
And a magnetic powder having an aspect ratio of 0.4 or more and 1.0 or less is easily pulverized by crushing using a pin disk mill so that the average particle diameter of the magnetic powder is more than 53 μm and 125 μm or less. Obtainable. As a matter of course, since the length of the minor axis of particles having a particle size larger than the thickness of the alloy ribbon obtained by crushing the alloy ribbon is determined by the thickness of the alloy ribbon, Particles with a larger aspect ratio can be obtained by crushing. Therefore, the average thickness of particles having a particle size of more than 106 μm corresponds to the length of the minor axis, falls within the range of 50 μm or more and 120 μm or less, and particles having an aspect ratio of 0.4 or more and 1.0 or less can be obtained.

Furthermore, since the quenched alloy of Ti-containing nanocomposite is easily broken at random as described above,
The smaller the particle size, the larger the aspect ratio tends to be, and the particles whose particle size is equal to or less than the thickness of the alloy ribbon,
It has a larger aspect ratio. The Ti-containing nanocomposite magnetic powder produced by the above method is adjusted to have the above particle size distribution by classification.

The Ti-containing nanocomposite magnetic powder produced by the above method has an aspect ratio of 0.4 or more and 1.
Since it is 0 or less, the filling property is excellent as compared with the conventional quenched magnet powder having an aspect ratio of less than 0.3. Therefore, by preparing a compound using a Ti-containing nanocomposite magnetic powder having an aspect ratio of 0.4 or more and 1.0 or less, magnetic properties are not deteriorated as compared with the case of using a conventional quenched magnet powder. It is possible to obtain a compound having excellent filling properties and moldability.

Particles having an aspect ratio of 0.3 or more, especially,
Particles having an aspect ratio of 0.4 or more can remarkably obtain the effect of improving the formability by adjusting the particle size distribution as described above, and also have the effect of suppressing springback during forming. As a result, a bonded magnet having a high filling rate (low porosity) can be obtained. When a thermosetting resin is used as the resin and is molded by, for example, a compression molding method, a bonded magnet having a magnetic powder filling rate of 80% or more can be obtained.

A compound for a bonded magnet can be obtained by mixing (and / or kneading) the magnetic powder containing the Ti-containing nanocomposite magnetic powder according to the present invention with various resins by a known method. As the resin, a known thermosetting resin or thermoplastic resin can be used. Furthermore, since the Ti-containing nanocomposite magnetic powder according to the present invention improves the moldability of the compound, it is possible to use a high-viscosity resin that has been difficult to use in the past. Furthermore, when the Ti-containing nanocomposite magnetic powder according to the present invention is used, the deterioration of the magnetic properties due to oxidation is small, so that the resin having a high melting point or softening point or curing temperature, which is conventionally difficult to use (for example, polyimide or heat-resistant grade product). Can be used, the characteristics (heat resistance, etc.) of the bonded magnet can be improved.

By using the Ti-containing nanocomposite magnetic powder according to the present invention, as described above, it is possible to provide a bonded magnet having a low porosity (void ratio) while ensuring a filling rate equal to or higher than the conventional one. . Therefore, it is possible to suppress / prevent various problems such as a decrease in reliability that accompanies the surface treatment of the as-molded bonded magnet having many voids. In addition,
The surface treatment in the present specification is a sealing treatment for filling voids,
Known surface treatment methods can be widely used, including formation of a protective film on the surface or modification of the surface.

As described above, according to the present invention, in addition to the bonded magnet having a low porosity being obtained, the corrosion resistance of the magnetic powder itself is higher than that of the conventional quenched magnet powder (for example, MQ powder). This is because the rare earth element content in the magnetic powder is lower than that of the conventional quenched magnet powder, and it has the above-mentioned structure. Therefore, as compared with the conventional bonded magnet using the rapidly cooled magnet powder, a bonded magnet having extremely high corrosion resistance can be obtained.

Further, according to the present invention, a bonded magnet having a high corrosion resistance of the magnetic powder itself and a low porosity can be obtained.
Sufficient corrosion resistance can be obtained by simpler surface treatment than before. That is, by simplifying the surface treatment process without sacrificing the corrosion resistance,
It is possible to improve production efficiency and reduce costs. Of course, the bonded magnet having a low porosity also has an advantage that it has excellent mechanical strength as compared with the conventional bonded magnet having a relatively high porosity.

Further, even if the thickness of the protective film formed on the surface of the bonded magnet is thinner than the conventional one, mechanical strength and / or corrosion resistance equal to or higher than the conventional one can be obtained.
Therefore, it is possible to reduce the thickness of the non-magnetic layer such as the resin coating formed on the surface of the magnet as compared with the conventional one, and to suppress the decrease in the utilization efficiency of the magnetic energy due to the magnetic gap formed in the magnetic circuit. .

The magnetic powder for a bonded magnet according to the present invention, the compound using the same and the bonded magnet will be described in more detail below.

[Ti-Containing Nanocomposite Magnetic Powder] The Ti-containing nanocomposite magnetic powder of the present invention is F containing Ti.
The molten alloy of the e-R-B type alloy is cooled to form a rapidly solidified alloy. This rapidly solidified alloy is
Although it contains a crystalline phase, it is heated if necessary to further promote crystallization.

By adding Ti to an iron-based rare earth alloy having a composition in a specific range, the present inventor is likely to generate during the cooling process of the molten alloy and has excellent magnetic properties (especially excellent coercive force and demagnetization curve). R, which suppresses the precipitation and growth of the α-Fe phase that causes the obstruction of the expression of (squareness) and bears the hard magnetic property.
It was found that the crystal growth of the ₂ Fe ₁₄ B type compound phase can be preferentially and uniformly advanced.

When Ti was not added, Nd ₂ Fe ₁₄
The α-Fe phase precipitates prior to the precipitation / growth of the B phase, which facilitates the growth. Therefore, at the stage where the crystal heat treatment of the quenched alloy is completed, the soft magnetic α-Fe phase is coarsened and the squareness of the demagnetization curve is deteriorated.
ax is greatly reduced.

On the other hand, when Ti is added, α-
Since the kinetics of precipitation / growth of the Fe phase becomes slow and the precipitation / growth requires time, if the precipitation / growth of the Nd ₂ Fe ₁₄ B phase starts before the precipitation / growth of the α-Fe phase is completed. Conceivable. Therefore, the Nd ₂ Fe ₁₄ B phase grows large in a state in which it is uniformly dispersed before the α-Fe phase becomes coarse. Also, Ti has a strong affinity for B,
It seems to be easily concentrated in iron-based borides. It is believed that the addition of Ti stabilizes the iron-based boride due to the strong bonding of Ti and B within the iron-based boride.

According to the present invention, the soft magnetic phases such as the iron-based boride and the α-Fe phase are made fine by the action of Ti, the Nd ₂ Fe ₁₄ B phase is uniformly dispersed, and the Nd ₂ Fe phase is further dispersed.
It is possible to obtain a nanocomposite structure having a high volume ratio of ₁₄ B phase. As a result, the coercive force and the magnetization (residual magnetic flux density) are increased and the squareness of the demagnetization curve is improved as compared with the case where Ti is not added.

Hereinafter, the Ti-containing nanocomposite magnetic powder according to the present invention will be described in more detail.

The Ti-containing nanocomposite magnetic powder according to the present invention preferably has a composition formula of (Fe _{1 -m} T _m ).
It is expressed by _100-xyz Q _x R _y M _z . Here, T is one or more elements selected from the group consisting of Co and Ni, and Q
Is one or more elements selected from the group consisting of B (boron) or B and C (carbon), R is one or more rare earth elements substantially free of La and Ce, M is Ti, Zr,
And Hf, which is at least one metal element selected from the group consisting of Hf and Hf, and always contains Ti.

X, y, z, and m that define the composition ratio
Are 10 <x ≦ 20 atomic%, 6 <y <10 atomic%, 0.1 ≦ z ≦ 12 atomic%, and 0 ≦ m ≦ 0.5, respectively.
It is preferable to satisfy the relationship.

The Ti-containing nanocomposite magnetic powder has a magnetization (residual magnetic flux density) of T due to the addition of Ti even though the composition ratio of rare earth elements is less than 10 atomic% of the whole.
An unexpected effect of maintaining or increasing the level equivalent to the case where i is not added and improving the squareness of the demagnetization curve is exhibited.

In the Ti-containing nanocomposite magnetic powder, since the size of the soft magnetic phase is fine, the constituent phases are combined by exchange interaction, and in addition to the hard magnetic R ₂ Fe ₁₄ B type compound phase, iron-based borides and Even if a soft magnetic phase such as α-Fe is present, the alloy as a whole can exhibit excellent squareness of the demagnetization curve.

The Ti-containing nanocomposite magnetic powder is preferably an iron-based boride or α-having a saturation magnetization equal to or higher than the saturation magnetization of the R ₂ Fe ₁₄ B type compound phase.
It contains Fe. This iron-based boride is, for example, Fe
₃ B (saturation magnetization 1.5T) and Fe ₂₃ B ₆ (saturation magnetization 1.6
T). Here, the saturation magnetization of R ₂ Fe ₁₄ B is R is N
It is about 1.6 T when d, and the saturation magnetization of α-Fe is 2.
It is 1T.

Usually, the composition ratio x of B exceeds 10 atomic%, and the composition ratio y of the rare earth element R is 5 atomic% or more 8
When it is in the range of atomic% or less, R ₂ Fe ₂₃ B ₃ is produced, but even when a raw material alloy having such a composition range is used, by adding Ti as in the present invention, Instead of the R ₂ Fe ₂₃ B ₃ phase, an R ₂ Fe ₁₄ B phase and an iron-based boride phase such as the Fe ₂₃ B ₆ phase or the Fe ₃ B phase can be generated. That is, by adding Ti, the ratio of the R ₂ Fe ₁₄ B phase can be increased, and the generated iron-based boride phase contributes to the improvement of the magnetization.

According to the experiments by the present inventor, only when Ti is added, unlike the case where other kinds of metals such as V, Cr, Mn, Nb, and Mo are added, the magnetization does not decrease,
Rather, it was discovered for the first time that the magnetization improved. Also, T
When i was added, the squareness of the demagnetization curve was particularly good as compared with the other additive elements described above.

The effect of adding Ti is that B is 1
It is remarkably exhibited when it exceeds 0 atom%. Below, Figure 1
This point will be explained with reference to.

FIG. 1 shows Nd-F to which Ti is not added.
It is a graph which shows the maximum magnetic energy product (BH) _{max of an} e-B magnet alloy, and the relationship of B amount. In the graph, a white bar shows data of a sample containing 10 atomic% or more and 14 atomic% or less Nd, and a black bar shows data of a sample containing 8 atomic% or more and less than 10 atomic% Nd. On the other hand, FIG. 2 is a graph showing the relationship between the maximum magnetic energy product (BH) _max and B of the Nd-Fe-B magnet alloy containing Ti. In the graph, a white bar shows data of a sample containing 10 atomic% or more and 14 atomic% or less Nd, and a black bar shows data of a sample containing 8 atomic% or more and less than 10 atomic% Nd.

As can be seen from FIG. 1, when Ti is added,
In the sample without B, B was 10 regardless of the Nd content.
Maximum magnetic energy product as the number exceeds atomic%
(BH)_maxIs falling. Furthermore, the extent of this decline
Is larger when the Nd content is 8 to 10 atomic%.
Become. This tendency has been known from the past, and Nd ₂
Fe₁₄In a magnet alloy whose main phase is B phase, the amount of B is
It is thought that it is preferable to set it to 10 atomic% or less
Came. For example, in US Pat. No. 4,836,868, B is
Disclosed is an example of 5 to 9.5 atomic%, and further, B is preferred.
4 atom% or more and less than 12 atom% as a preferable range, more preferable
The range of 4 atom% or more and 10 atom% or less
is doing.

On the other hand, in the sample to which Ti is added, as can be seen from FIG. 2, the maximum magnetic energy product (BH) _max is improved in a certain range where B exceeds 10 atomic%. This improvement is particularly remarkable when the Nd content is 8 to 10 atomic%.

As described above, according to the present invention, it is possible to obtain an effect, which cannot be predicted from the conventional common general knowledge that the magnetic properties deteriorate when B exceeds 10 atomic%, by adding Ti.

Next, a method for producing a Ti-containing nanocomposite magnetic powder contained in at least the magnetic powder for a bonded magnet of the present invention will be described.

The above composition formula (Fe _1-m T _m ) _100-xyz Q _x
R _y M _z (x, y, z, and m are each 10 <x
≦ 20 atomic%, 6 <y <10 atomic%, 0.1 ≦ z ≦ 12
%, And the iron-based alloy melt represented by 0 ≦ m ≦ 0.5) is cooled in an inert atmosphere, whereby R ₂ Fe
₁₄ A quenched alloy containing, for example, 60% by volume or more of the B-type compound phase is prepared. The average crystal grain size of the R ₂ Fe ₁₄ B type compound phase in the quenched alloy can be, for example, 80 nm or less. If necessary, the quenched alloy is heat-treated to crystallize the amorphous material remaining in the quenched alloy.

In an embodiment using a cooling roll such as a melt spinning method or a strip casting method, the alloy melt is cooled in an atmosphere having a pressure of 1.3 kPa or more. As a result, not only is the molten alloy melt rapidly cooled by contact with the cooling roll, but also after being separated from the cooling roll, the molten alloy is appropriately cooled by the secondary cooling effect of the atmospheric gas.

According to the experiments conducted by the present inventor, the pressure of the atmospheric gas at the time of quenching is 1.3 kPa or more and the atmospheric pressure (10
1.3 kPa) or less, preferably 10 k
It is more preferable to set it in the range of Pa to 90 kPa. A more preferable range is 20 kPa or more and 60 kPa or less.

Under the above atmospheric gas pressure, the roll surface peripheral velocity is preferably in the range of 4 m / sec to 50 m / sec. If the roll surface peripheral velocity is slower than 4 m / sec, the crystal grains of the R ₂ Fe ₁₄ B type compound phase contained in the quenched alloy will become coarse. As a result, the heat treatment further increases the size of the R ₂ Fe ₁₄ B type compound phase, which may deteriorate the magnetic properties.

According to experiments, the more preferable range of the roll surface peripheral velocity is 5 m / sec or more and 30 m / sec or less, and the more preferable range is 5 m / sec or more and 20 m / sec or less. In particular, it is most preferable that the roll surface peripheral velocity is in the range of 13 m / sec or more and 17 m / sec or less.

In the present invention, coarse α is contained in the quenched alloy.
Hardly precipitating -fe, tissue having fine R ₂ Fe ₁₄ B compound phase, or tissue and an amorphous phase having fine R ₂ Fe ₁₄ B type compound phase are mixed tissue is produced. As a result, it is possible to obtain a high-performance nanocomposite permanent magnet in which a soft magnetic phase such as an iron-based boride phase is present in a finely dispersed state or a thinly spread state between the hard magnetic phases (grain boundaries) after heat treatment. it can. Note that the "amorphous phase" in the present specification is not limited to a phase constituted only by a portion in which the atomic arrangement is completely disordered, but also a crystallization precursor or microcrystal (size: several nm or less),
Alternatively, it also includes a phase partially containing an atomic cluster. Specifically, a phase whose crystal structure cannot be clearly identified by X-ray diffraction or transmission electron microscope observation is broadly referred to as an "amorphous phase".

Conventionally, a molten alloy having a composition similar to that targeted by the present invention (but not containing Ti) is cooled and rapidly cooled to contain R ₂ Fe ₁₄ B type compound phase in an amount of 60% by volume or more. When an alloy is produced, an alloy structure in which a large amount of α-Fe is precipitated is obtained, so that there is a problem that α-Fe becomes coarse in the subsequent crystallization heat treatment.
When the soft magnetic phase such as α-Fe is coarsened, the magnetic properties are significantly deteriorated, and a bonded magnet that can withstand practical use cannot be obtained at all.

In particular, when the content of B is relatively large as in the raw material alloy composition used in the present invention, a crystal phase is produced even if the cooling rate of the molten alloy is slowed due to the high amorphous forming ability of B. It was difficult. Therefore, according to the prior art, the cooling rate of the molten alloy is sufficiently reduced to obtain R ₂ Fe ₁₄
If an attempt is made to produce a rapidly solidified alloy in which the volume ratio of the B-type compound phase exceeds 60%, in the prior art, R ₂ Fe ₁₄
In addition to the B-type compound phase, a large amount of α-Fe or its precursor is deposited, and the subsequent crystallization heat treatment causes α-Fe.
The coarsening of the phase progressed, and the magnetic characteristics deteriorated significantly.

From the above, conventionally, in order to increase the coercive force of the raw material alloy for the nanocomposite magnet magnetic powder, the cooling rate of the molten alloy should be increased so that most of the rapidly solidified alloy is occupied by the amorphous phase. After that, it was common knowledge that it is preferable to form a uniformly refined structure from the amorphous phase by crystallization heat treatment. This is because in order to obtain a nanocomposite having an alloy structure in which fine crystal phases are dispersed, it was thought that crystallization should be performed from the amorphous phase in a heat treatment process that is easily controlled.

Therefore, L which is excellent in amorphous forming ability
After a is added to the raw material alloy and the melt of the raw material alloy is rapidly cooled to produce a rapidly solidified alloy having an amorphous phase as a main phase, both the Nd ₂ Fe ₁₄ B phase and the α-Fe phase are subjected to crystallization heat treatment. It has been reported that the technique of precipitating and growing the slag and making each phase as fine as several tens of nm (W.
C. Chan, et.al. "THE EFFECTS OF REFRACTORY METALS O
N THE MAGNETIC PROPERTIES OF α-Fe / R ₂ Fe ₁₄ B-TYPE NA
NOCOMPOSITES ", IEEE, Trans. Magn. No. 5, INTERMAG.
99, Kyongiu, Korea pp.3265-3267, 1999). In addition, this paper shows that the addition of a trace amount of refractory metal elements such as Ti (2 atomic%) improves the magnetic properties, and that the composition ratio of rare earth element Nd is 11.0 atomic% rather than 9.5 atomic%. %
It has been taught that the increase in the Nd ₂ Fe ₁₄ B phase and the α-Fe phase is preferable for increasing the grain size.
The above refractory metal is added by adding boride (R ₂ Fe ₂₃ B ₃ or Fe
The production of ₃ B) inhibited, Nd ₂ Fe ₁₄ B phase and alpha-Fe
It is carried out in order to produce a raw material alloy for magnet powder consisting of only two phases.

On the other hand, in the present invention, the function of the added Ti suppresses the precipitation of the α-Fe phase in the rapid solidification step, and further, the iron-based boride and the soft magnetic phase are generated in the crystallization heat treatment step. By suppressing the coarsening, magnetic powder having excellent magnetic properties can be obtained.

According to the present invention, the magnetization (residual magnetic flux density) and the coercive force are high, and the squareness of the demagnetization curve is excellent, while using a raw material alloy having a relatively small amount of rare earth element (for example, 9 atomic% or less). Magnet powder can be manufactured.

[0084] As described above, an increase in the coercivity of the Ti-containing nanocomposite magnet powder for raw material alloy according to the present invention, Nd ₂
This is achieved by preferentially precipitating and growing the Fe ₁₄ B phase in the cooling process, thereby increasing the volume ratio of the Nd ₂ Fe ₁₄ B phase and suppressing the coarsening of the soft magnetic phase. In addition, the increase in magnetization is caused by the action of Ti, which produces a boride phase such as a ferromagnetic iron-based boride from the B-rich non-magnetic amorphous phase existing in the rapidly solidified alloy, resulting in a strong strength after the crystallization heat treatment. It is considered that it was obtained because the volume ratio of the magnetic phase was increased.

The raw material alloy obtained as described above is subjected to crystallization heat treatment, if necessary, to obtain R ₂ Fe.
_{14 including} B-type compound phase, boride phase, and α-Fe phase 3
It is preferable to form a structure containing more than one kind of crystalline phase. In this structure, the average crystal grain size of the R ₂ Fe _{1 4} B type compound phase is 10 nm or more and 200 nm or less, the boride phase and α
The heat treatment temperature and time are adjusted so that the average crystal grain size of the —Fe phase is 1 nm or more and 100 nm or less. R ₂ Fe
The average crystal grain size of the ₁₄ B type compound phase is usually 30 nm or more, but it is 50 nm or more depending on the conditions. The average crystal grain size of a soft magnetic phase such as a boride phase or α-Fe phase is often 30 nm or less, and typically only a few nm.

R ₂ in the final raw material alloy for magnet powder
The average crystal grain size of the Fe ₁₄ B type compound phase is larger than the average crystal grain size of the α-Fe phase. FIG. 3 schematically shows the metal structure of this raw material alloy. As can be seen from FIG. 3, fine soft magnetic phases are dispersed and exist between the relatively large R ₂ Fe ₁₄ B type compound phases. Thus, even if the average crystal grain size of the R ₂ Fe ₁₄ B type compound phase becomes relatively large, the crystal growth of the soft magnetic phase is suppressed and the average crystal grain size is sufficiently small. Since they are magnetically coupled by the interaction, and as a result, the magnetization direction of the soft magnetic phase is constrained by the hard magnetic phase, the alloy as a whole can exhibit excellent demagnetization curve squareness.

The reason why boride is likely to be produced in the above-mentioned production method is that when a solidified alloy in which the R ₂ Fe ₁₄ B type compound phase occupies the majority is produced, the amorphous phase present in the quenched alloy inevitably contains excessive B. It is considered that this is because this B is likely to combine with other elements in the crystallization heat treatment to precipitate and grow. However, if a compound with low magnetization is generated by the combination of B and other elements, the magnetization of the alloy as a whole will be reduced.

According to the experiments by the present inventors, only when Ti is added, unlike the case where other kinds of metals such as V, Cr, Mn, Nb, and Mo are added, the decrease in magnetization does not occur.
Rather, it was found that the magnetization was improved. Further, when M (particularly Ti) was added, the squareness of the demagnetization curve became particularly good as compared with the other additive elements described above. From these facts, it is considered that Ti plays a particularly important role in suppressing the formation of boride having low magnetization. In particular,
In the composition range of the raw material alloy used in the present invention, B and T
When i is relatively small, an iron-based boride phase having ferromagnetism is likely to precipitate by heat treatment. In this case, B contained in the non-magnetic amorphous phase is taken into the iron-based boride, and as a result, the volume ratio of the non-magnetic amorphous phase remaining after the crystallization heat treatment decreases and the ferromagnetic crystal phase increases. It is considered that the residual magnetic flux density B _r is improved.

Hereinafter, this point will be described in more detail with reference to FIG.

FIG. 4 shows the case of adding Ti and T
It is a figure which shows typically the change of the microstructure in the crystallization process of the rapid solidification alloy when Nb etc. are added instead of i. When Ti is added, grain growth of each constituent phase is suppressed in a temperature range higher than the temperature at which α-Fe precipitates, and excellent hard magnetic properties are maintained. On the other hand, when a metal element such as Nb, V, or Cr is added, the grain growth of each constituent phase remarkably progresses in a relatively high temperature region where α-Fe precipitates, and it acts between each constituent phase. As a result of weakening the exchange interaction, the squareness of the demagnetization curve is greatly reduced.

First, the case where Nb, Mo and W are added will be described. In this case, if the heat treatment is performed in a relatively low temperature region where α-Fe does not precipitate, it is possible to obtain good hard magnetic characteristics with excellent squareness of the demagnetization curve. However, in the alloy heat-treated at such a temperature, R ₂ Fe ₁₄
It is presumed that the B-type fine crystal phase is dispersed and present in the non-magnetic amorphous phase, and since the nanocomposite structure is not formed, high magnetization cannot be expected. Also,
When the heat treatment is performed at a higher temperature, the α-Fe phase is precipitated out of the amorphous phase. Unlike the case where Ti is added, this α-Fe phase rapidly grows and coarsens after precipitation. For this reason, the exchange coupling between the constituent phases becomes weak, and the squareness of the demagnetization curve is greatly deteriorated.

On the other hand, when Ti is added, a heat treatment is performed to form an R ₂ Fe ₁₄ B type crystal phase, an iron-based boride phase, and α-Fe.
A nanocomposite structure containing a phase and an amorphous phase is obtained, and each constituent phase is uniformly miniaturized. Further, when Ti is added, the growth of the α-Fe phase is suppressed.

When V or Cr is added, these added metals form a solid solution with Fe and antiferromagnetically couple with Fe, so that the magnetization is greatly reduced. Further, when V or Cr is added, grain growth due to heat treatment is not sufficiently suppressed,
The squareness of the demagnetization curve deteriorates.

Only when Ti is added as described above, α-
It is possible to appropriately suppress the coarsening of the Fe phase and form a ferromagnetic iron-based boride. Further, Ti is an element that delays the precipitation of Fe primary crystals (γ-Fe that is transformed into α-Fe later) during liquid quenching and facilitates the formation of a supercooled liquid.
Since it plays an important role together with C and C, even if the cooling rate at the time of rapidly cooling the molten alloy is set to a relatively low value of about 10 ² ° C / sec to 10 ⁵ ° C / sec, α-Fe does not precipitate significantly. , R ₂ Fe ₁₄ B type crystal phase and an amorphous phase can be mixed to produce a quenched alloy. This is
Among various liquid quenching methods, the strip casting method, which is particularly suitable for mass production, can be adopted, which is extremely important for cost reduction.

As a method for rapidly cooling the molten alloy to obtain the raw material alloy, the strip casting method in which the molten metal is poured directly from the tundish onto the cooling roll without controlling the flow rate of the molten metal by a nozzle or an orifice has high productivity, It is a low cost method. In order to make the molten metal of the R—Fe—B rare earth alloy amorphous in the cooling rate range that can be achieved by the strip casting method, it is usually necessary to add 10 atomic% or more of B. When a large amount of B is added in the conventional technique, after the crystallization heat treatment is performed on the quenched alloy, in addition to the non-magnetic amorphous phase, coarse α-Fe and soft magnetic phase Nd ₂ Fe ₂₃ B _A homogeneous fine crystal structure cannot be obtained because _three phases are precipitated. As a result, the volume ratio of the ferromagnetic phase is reduced, and the coercive force is significantly reduced due to the reduction of the magnetization and the abundance ratio of the Nd ₂ Fe ₁₄ B phase. However, when Ti is added as in the present invention,
As described above, phenomena such as suppression of coarsening of the α-Fe phase occur, and the magnetization unexpectedly improves.

It should be noted that it is easier to obtain high final magnetic properties when the quenched alloy contains more Nd ₂ Fe ₁₄ B phase than when the quenched alloy contains much amorphous phase. The volume ratio of the Nd ₂ Fe ₁₄ B phase in the quenched alloy is preferably not less than half of the whole, specifically 60% by volume or more. The value of 60% by volume is measured by Moessbauer spectrum spectroscopy.

Next, an embodiment using a melt spinning method which is a kind of roll method will be described more specifically.

[Liquid Quenching Device] In the present embodiment, for example, the raw material alloy is manufactured using the quenching device shown in FIG.
In order to prevent the oxidation of the raw material alloy containing the rare earth element R or Fe, which is easily oxidized, the alloy manufacturing process is performed in an inert gas atmosphere. A rare gas such as helium or argon or nitrogen can be used as the inert gas. Since nitrogen is relatively easy to react with the rare earth element R, it is preferable to use a rare gas such as helium or argon.

The apparatus shown in FIG. 5 is provided with a melting chamber 1 and a quenching chamber 2 for the raw material alloy, which can maintain a vacuum or an inert gas atmosphere and adjust the pressure thereof. 5A is an overall configuration diagram, and FIG. 5B is a partially enlarged view.

As shown in FIG. 5A, the melting chamber 1
Is a raw material 2 formulated to have a desired magnet alloy composition.
Melting furnace 3 for melting 0 at high temperature, and tapping nozzle 5 at the bottom
A hot water storage container 4 having the above and a blended raw material supply device 8 for feeding the blended raw material into the melting furnace 3 while suppressing the entry of the atmosphere. The hot water storage container 4 has a heating device (not shown) capable of storing the molten metal 21 of the raw material alloy and maintaining the temperature of the molten metal at a predetermined level.

The quenching chamber 2 has the molten metal 2 discharged from the molten metal discharge nozzle 5.
A rotary cooling roll 7 for rapidly solidifying 1 is provided.

In this apparatus, the atmosphere and pressure in the melting chamber 1 and the quenching chamber 2 are controlled within a predetermined range. Therefore, the atmospheric gas supply ports 1b, 2b, and 8b and the gas exhaust ports 1a, 2a, and 8a are provided at appropriate places of the apparatus. In particular, the gas exhaust port 2a is connected to a pump in order to control the absolute pressure in the quenching chamber 2 within the range of 30 kPa to normal pressure (atmospheric pressure).

The melting furnace 3 is tiltable, and the molten metal 21 is appropriately poured into the hot water storage container 4 via the funnel 6. Molten metal 21
Is heated in the hot water storage container 4 by a heating device (not shown).

The hot water discharge nozzle 5 of the hot water storage container 4 is arranged on the partition wall between the melting chamber 1 and the quenching chamber 2, and the molten metal 21 in the hot water storage container 4 is
To the surface of the cooling roll 7 located below. The orifice diameter of the tap nozzle 5 is, for example, 0.5 to 2.0 m.
m. When the melt 21 has a large viscosity, it becomes difficult for the melt 21 to flow in the hot water discharge nozzle 5. However, in the present embodiment, since the quenching chamber 2 is kept at a lower pressure state than the melting chamber 1, the melting chamber 1 and the quenching chamber 2 are separated from each other. A pressure difference is formed between the molten metal 21
The tap water is smoothly executed.

The cooling roll 7 can be formed of Al alloy, copper alloy, carbon steel, brass, W, Mo, bronze from the viewpoint of thermal conductivity. However, from the viewpoint of mechanical strength and economical efficiency,
It is preferably formed from Cu, Fe, or an alloy containing Cu or Fe. If the cooling roll is made of a material other than Cu or Fe, the exfoliation property of the quenched alloy from the cooling roll deteriorates, and therefore the quenched alloy may be wound around the roll, which is not preferable. The diameter of the cooling roll 7 is, for example, 300 to 5
It is 00 mm. The water cooling capacity of the water cooling device provided in the cooling roll 7 is calculated and adjusted according to the solidification latent heat and the amount of tapping water per unit time.

According to the apparatus shown in FIG. 5, for example, a total of 10
It is possible to rapidly solidify kg of the raw material alloy in 10 to 20 minutes. The quenched alloy thus formed becomes, for example, an alloy ribbon (alloy ribbon) 22 having a thickness of 10 to 300 μm and a width of 2 mm to 3 mm.

At this time, the thickness of the alloy ribbon is adjusted to be 50 μm or more and 300 μm or less, and then, if necessary, the rapidly solidified alloy is crystallized by heat treatment and then the alloy is crushed. Thus, it is possible to obtain a powder having an aspect ratio (size in the minor axis direction / size in the major axis direction) of the entire powder particles of 0.4 or more and 1.0 or less. By adjusting the thickness of the alloy ribbon in this way and crushing it,
For example, most of particles having a particle size of 215 μm or less (90% by mass or more of the whole magnetic powder) have an aspect ratio of 0.
It can be 4 or more and 1.0 or less. The crushing method will be described later.

[Liquid quenching method] First, a melt 21 of the raw material alloy represented by the above composition formula is prepared and stored in the hot water storage container 4 of the melting chamber 1 in FIG. Next, this molten metal 21 is discharged from the discharge nozzle 5 onto the water-cooled roll 7 in the reduced pressure Ar atmosphere,
Upon contact with the cooling roll 7, it is rapidly cooled and solidified. As the rapid solidification method, it is necessary to use a method capable of controlling the cooling rate with high accuracy.

In the case of the present embodiment, when cooling and solidifying the molten metal 21, it is preferable to set the cooling rate to 1 × 10 ² to 1 × 10 ⁸ ° C./sec, and 1 × 10 ⁴ to 1 × 10 ⁶ ° C./sec. More preferably.

The time during which the molten metal 21 of the alloy is cooled by the cooling roll 7 corresponds to the time from when the alloy comes into contact with the outer peripheral surface of the rotating cooling roll 7 until it separates, and the temperature of the alloy decreases during that time. , Becomes a supercooled liquid state. Then, the supercooled alloy separates from the cooling roll 7 and flies in an inert atmosphere. The alloy is deprived of heat by the atmospheric gases while flying in ribbon form, resulting in a further decrease in temperature. In this embodiment, the pressure of the atmospheric gas is 30 kPa to
Since the pressure is set within the range of normal pressure, the heat removal effect by the atmospheric gas is enhanced, and the Nd ₂ Fe ₁₄ B type compound can be uniformly and finely precipitated and grown in the alloy. If an appropriate amount of element M such as Ti is not added to the raw material alloy, α-Fe preferentially precipitates and grows in the quenched alloy that has undergone the cooling process as described above. However, the final magnetic characteristics will deteriorate.

In this embodiment, the roll surface speed is 10 m.
/ Sec or more and 30 m / sec or less, and by adjusting the atmospheric gas pressure to 30 kPa or more in order to enhance the secondary cooling effect by the atmospheric gas, fine R ₂ Fe having an average crystal grain size of 80 nm or less is obtained. ₁₄ A quenching alloy containing 60% by volume or more of B-type compound phase is produced.

The liquid quenching method for producing the Ti-containing nanocomposite magnetic powder according to the present invention is not limited to the melt spinning method in which the flow rate of the molten alloy supplied to the surface of the cooling roll is controlled by the nozzles and orifices illustrated. A strip cast method that does not use nozzles or orifices can be used. In addition to the single roll method, a twin roll method using two cooling rolls may be used.

Among the above quenching methods, the strip casting method has a relatively low cooling rate of 10 ² to 10 ⁵ ° C / sec. In the present embodiment, by adding an appropriate amount of Ti to the alloy, even if the strip casting method is used, Fe is added.
It is possible to form a quenched alloy which is mostly composed of a structure not containing primary crystals. Since the strip casting method has a process cost of about half or less than that of other liquid quenching methods, it is effective in producing a large amount of quenched alloys as compared with the melt spinning method, and is a technique suitable for mass production. When the element M is not added to the raw material alloy, or instead of the element Ti, Cr,
When V, Mn, Mo, Ta, and / or W is added, even if a quenched alloy is formed by using the strip casting method, a metal structure containing a large amount of Fe primary crystals is generated,
The desired metallographic structure cannot be formed.

Further, the thickness of the alloy can be controlled by adjusting the peripheral speed of the roll surface in the melt spinning method or the strip casting method. When an alloy having a thickness of 50 μm or more and 300 μm or less is formed by adjusting the roll surface peripheral speed, the alloy is composed of the above-described fine structure and is therefore easily fractured in various directions by the crushing process. As a result, powder particles having an equiaxed shape (aspect ratio close to 1) are easily obtained. That is, the powder particles extending flatly along a certain direction are not obtained, but the powder particles having an equiaxial shape, that is, a shape close to a sphere are formed.

On the other hand, when the roll surface peripheral velocity is increased to make the thickness of the alloy thinner than 50 μm, the metallographic structure of the alloy tends to be aligned in the direction perpendicular to the roll contact surface as in the case of the conventional quench magnet. is there. Therefore, it is easy to break along that direction, the powder particles obtained by pulverization are likely to have a shape that extends flat along the direction parallel to the surface of the alloy, and powder particles with an aspect ratio of less than 0.3 are generated. Easy to be affected.

FIG. 6A schematically shows the alloy 10 before the pulverizing step and the powder particles 11 after the pulverizing step in the method for manufacturing magnet powder according to the present embodiment. On the other hand, FIG.
(B) schematically shows the alloy ribbon 12 before the pulverizing step and the powder particles 13 after the pulverizing step in the conventional method for producing a quenched magnet powder.

As shown in FIG. 6A, in the case of this embodiment, since the alloy 10 before pulverization is composed of equiaxed crystals having a small crystal grain size, fracture occurs along random orientations. It is easy to produce equiaxed powder particles 11. On the other hand, in the case of the conventional quenched alloy, as shown in FIG.
As shown in (3), since the alloy ribbon 12 easily breaks in a direction substantially perpendicular to the surface thereof, the particle 13 has a flat shape.

As described above, since the quenched alloy of the Ti-containing nanocomposite easily breaks along the random orientation,
By controlling the peripheral velocity of the roll surface and adjusting the thickness of the alloy ribbon, it is possible to easily obtain a powder having an aspect ratio of 0.3 or more, preferably 0.4 or more and 1.0 or less.

[Heat Treatment] In this embodiment, the heat treatment is performed.
Perform in a gon atmosphere. Preferably, the heating rate is set to 0.
08 ° C / sec to 20 ° C / sec, 550 ° C or more and 850 ° C
After holding at the following temperature for 30 seconds or more and 20 minutes or less,
Cool to room temperature. Amorphous by this heat treatment
Fine crystals of metastable phase precipitate and grow in the phase,
A jitt structure is formed. According to this embodiment, heat
Already fine Nd at the start of processing ₂Fe₁₄B type crystal phase
Since 60% by volume or more of the whole is present, the α-Fe phase and
Coarsening of other crystal phases is suppressed, and Nd₂Fe₁₄B-type crystal
Each constituent phase (soft magnetic phase) other than the phases is uniformly miniaturized.

When the heat treatment temperature is lower than 550 ° C.,
A large amount of amorphous phase remains after the heat treatment, and the coercive force may not reach a sufficient level depending on the rapid cooling conditions.
Further, when the heat treatment temperature exceeds 850 ° C., grain growth of each constituent phase is remarkable, the residual magnetic flux density B _r is lowered, and the squareness of the demagnetization curve is deteriorated. Therefore, the heat treatment temperature is preferably 550 ° C. or higher and 850 ° C. or lower, but a more preferable heat treatment temperature range is 570 ° C. or higher and 820 ° C. or lower.

In the present embodiment, a sufficient amount of Nd ₂ Fe ₁₄ B is contained in the quenched alloy due to the secondary cooling effect of the atmospheric gas.
The type compound phase is uniformly and finely precipitated. For this reason,
Even if the quenched alloy is not intentionally subjected to crystallization heat treatment, the rapidly solidified alloy itself can exhibit sufficient magnetic properties. Therefore, crystallization heat treatment is not an essential step,
It is preferable to do this to improve the magnetic properties.
The magnetic properties can be sufficiently improved even by heat treatment at a lower temperature than in the conventional case.

The heat treatment atmosphere is preferably an inert gas atmosphere in order to prevent oxidation of the alloy. The heat treatment may be performed in a vacuum of 0.1 kPa or less.

In the quenched alloy before heat treatment, R ₂ Fe ₁₄ B
Type compound phase and amorphous phase, Fe ₃ B phase,
A metastable phase such as Fe ₂₃ B ₆ and R ₂ Fe ₂₃ B ₃ phase may be contained. In that case, by the effect of Ti addition in the present invention, in the heat treatment, R ₂ Fe ₂₃ B ₃ phase disappears, R ₂
An iron-based boride (for example, Fe ₂₃ B ₆ ) or α-which exhibits a saturation magnetization equal to or higher than that of the Fe ₁₄ B phase.
Fe can be crystal-grown.

In the case of the present invention, even if a soft magnetic phase such as α-Fe is finally present, grain growth is suppressed by the effect of Ti and the structure is made fine. As a result, the soft magnetic phase and the hard magnetic phase are magnetically coupled by the exchange interaction, so that excellent magnetic characteristics are exhibited.

The average crystal grain size of the R ₂ Fe ₁₄ B type compound phase after the heat treatment needs to be 300 nm or less which is a single domain crystal grain size, and 10 nm or more and 200 nm or less, and further 20 nm or more and 150 nm or less. Is preferable, and more preferably 20 nm or more and 100 nm or less. On the other hand, when the average crystal grain size of the boride phase or the α-Fe phase exceeds 100 nm, the exchange interaction acting between the constituent phases is weakened and the squareness of the demagnetization curve is deteriorated.
H) _max decreases. The average grain size of these is 1
If it is less than nm, a high coercive force cannot be obtained. From the above, the average crystal grain size of the soft magnetic phase such as boride phase or α-Fe phase is 1 nm or more and 100 nm or less, preferably 50 nm or less.
The thickness is preferably nm or less, and more preferably 30 nm or less.

The thin ribbon of the quenched alloy may be roughly cut or crushed before the heat treatment. After the heat treatment, the obtained alloy coarse powder (or thin strip) is pulverized to produce magnetic powder, whereby magnetic powder for a bonded magnet can be manufactured.

[Description of Grinding Process] As the Ti-containing nanocomposite magnetic powder for bonded magnets, those having a maximum particle size of 300 μm or less are used. In particular, in order to suppress shedding and the like in small magnets, the maximum particle size of the Ti-containing nanocomposite magnetic powder is preferably 250 μm or less, and 215 μm
It is more preferably m or less. When used for compression molding, the average particle size is preferably in the range of 50 μm to 200 μm, more preferably in the range of more than 53 μm and 125 μm or less.

Further, as described above, at least the particle size of the Ti-containing nanocomposite magnetic powder of the present invention is 106 μm.
The aspect ratio of the particles exceeding m is 0.3 or more and 1.0 or less, and preferably 0.4 or more.

By appropriately setting the thickness of the alloy ribbon and the pulverization conditions (average particle diameter) as described above, the aspect ratio and average particle diameter of the Ti-containing nanocomposite magnetic powder can be kept within the above desired ranges. You can The Ti-containing nanocomposite magnetic powder having an aspect ratio of 0.3 or more and 1.0 or less and an average particle size of 50 μm or more and 200 μm or less is obtained by crushing an alloy ribbon having a thickness of 50 μm or more and 300 μm or less.

Particularly, a Ti-containing nanocomposite magnetic powder having an aspect ratio of 0.4 or more and 1.0 or less and an average particle size of 53 μm or more and 125 μm or less, which is preferably used for molding a small magnet, is as shown in FIG. 7, for example. It can be produced by crushing an alloy ribbon having a thickness of 50 μm or more and 120 μm or less using a pin disk mill device or the like.

FIG. 7 is a sectional view showing an example of the pin mill device used in this embodiment. The pin mill device 40 is a pin disc mill, and two discs (disks) 42a and 42b having a plurality of pins 11 arranged on one surface are opposed to each other and arranged so that the pins 41 do not collide with each other. At least one disk 42a and / or 42b
Rotates at high speed. In the example of FIG. 7, the disk 42a is the shaft 43.
Rotate around. FIG. 8 shows a front view of the rotating disk 42a. On the disk 42a of FIG. 8, the pins 41 are arranged so as to draw a plurality of concentric circles. Even on the fixed disk 42b, the pins 41 are arranged so as to draw concentric circles.

The object to be crushed by the pin disk mill is fed from the charging port 44 into the space of the gap where the two disks face each other, and the pin 41 on the rotating disk 42a and the stopped state. It collides with the pin 41 on the disk 42b and is crushed by the impact. The powder generated by the pulverization is blown in the direction of arrow A and finally collected in one place.

In the pin mill device 40 of this embodiment,
The disks 42a and 42b that support the pin 41 are made of stainless steel or the like, but the pin 41 is made of carbon steel, ceramics, or a cemented carbide material such as a tungsten carbide (WC) sintered body. As the cemented carbide material, besides WC sintered body, TiC, MoC, Nb
C, TaC, Cr ₃ C _{2 and the} like can be preferably used.
These cemented carbides contain Fe, Co, Ni, Mo, C of carbide powders of metals belonging to the IVa, Va, and VIa groups.
It is a sintered body bonded using u, Pb, or Sn or an alloy thereof.

The pin mill device preferably used in this embodiment is not limited to the pin disc mill in which the pins are arranged on the disc, and may be, for example, a device in which the pins are arranged on the cylinder. The use of the pin mill device has the advantages that a powder having a particle size distribution close to the normal distribution can be obtained, the average particle size can be easily adjusted, and the mass productivity is excellent.

The Ti-containing nanocomposite magnetic powder having the above-mentioned particle size distribution can be obtained by classifying and mixing the Ti-containing nanocomposite magnetic powder thus produced, if necessary.

[Reasons for Limiting Composition] The Ti-containing nanocomposite magnetic powder according to the present invention has a composition formula (Fe _1-m T _m ) _100-x-
yz Q _x R _y M _z (T is at least one element selected from the group consisting of Co and Ni, Q is B or at least one element selected from the group consisting of B and C, R is L
at least one rare earth element substantially free of a and Ce, M is a metal element selected from the group consisting of Ti, Zr, and Hf, and at least one metal element that always contains Ti, composition ratio x, y, z and m are 10 <x ≦ 20 atom%, 6 <y <10 atom%, 0.
1 ≦ z ≦ 12 atomic%, and 0 ≦ m ≦ 0.5).

Q is entirely composed of B (boron) or a combination of B and C (carbon). The atomic ratio of C to the total amount of Q is 0.2
It is preferably 5 or less.

When the composition ratio x of Q is 10 atomic% or less, when the cooling rate during quenching is relatively low at about 10 ² ° C / sec to 10 ⁵ ° C / sec, the R ₂ Fe ₁₄ B type crystal phase and the amorphous phase are It becomes difficult to produce a quenched alloy in which phases are mixed, and even if heat treatment is performed thereafter, H of less than 600 kA / m
_{Only cJ} can be obtained. Therefore, it becomes difficult to produce a magnetic powder having an aspect ratio of 0.4 to 1.0 and excellent magnetic characteristics by relatively slowing the roll peripheral velocity by the melt spinning method or the strip casting method. Further, among the liquid quenching methods, the strip casting method and the atomizing method, which have relatively low process costs, cannot be used, and the price of the magnetic powder increases. On the other hand, the composition ratio x of Q is 20
When it exceeds atomic%, the volume ratio of the amorphous phase remaining after the crystallization heat treatment increases, and at the same time, the abundance ratio of α-Fe having the highest saturation magnetization in the constituent phases decreases,
The residual magnetic flux density B _r is reduced. From the above,
The composition ratio x of Q is preferably set to exceed 10 atom% and 20 atom% or less. The more preferable composition ratio x is 10 atom% or more and 17 atom% or less.
Further, since it is possible to efficiently precipitate the iron-based boride phase and improve B _r , it is more preferable to set the range of x to 10 atom% or more and 14 atom% or less.

R is at least one element selected from the group of rare earth elements (including Y). The presence of La or Ce deteriorates the coercive force and the squareness. Therefore, it is preferable that La and Ce are not substantially contained. However, when a trace amount of La or Ce (0.5 atom% or less) is present as an impurity that is inevitably mixed, there is no problem in terms of magnetic characteristics. Therefore, when La or Ce is contained at 0.5 atom% or less, it can be said that La or Ce is not substantially contained.

More specifically, R preferably contains Pr or Nd as an essential element, and a part of the essential element may be replaced with Dy and / or Tb. When the composition ratio y of R is less than 6 atomic% of the whole, the compound phase having the R ₂ Fe ₁₄ B type crystal structure necessary for expressing the coercive force is not sufficiently precipitated, and the coercive force H _{cJ of 600} kA / m or more is _obtained. Will not be able to get. Further, when the composition ratio y of R is 10 atomic% or more, iron-based borides and α-Fe having ferromagnetism
Abundance decreases. At the same time, the corrosion resistance and oxidation resistance of the magnetic powder are reduced, making it difficult to obtain the effects of the bonded magnet of the present invention. Therefore, the composition ratio y of the rare earth element R is preferably adjusted in the range of 6 atomic% or more and less than 10 atomic%, for example, 6 atomic% or more and 9.5 atomic% or less. A more preferable range of R is 7 atom% or more and 9.3 atom% or less, and a more preferable range of R is 8 atom% or more and 9.0 atom% or less.

The additive metal element M essentially contains Ti and may further contain Zr and / or Hf.
Ti is an essential element for obtaining the above-mentioned effect, contributes to the improvement of the coercive force H _cJ and the residual magnetic flux density B _r and the squareness of the demagnetization curve, and the maximum energy product (B
H) Improve max.

When the composition ratio z of the metal element M is less than 0.5 atom% of the whole, the effect of adding Ti is not sufficiently exhibited. On the other hand, the composition ratio z of the metal element M is 12 atom% of the whole.
If it exceeds, the volume ratio of the amorphous phase remaining after the crystallization heat treatment increases, and thus the residual magnetic flux density B _r is likely to decrease. From the above, the composition ratio z of the metal element M is preferably in the range of 0.5 atom% or more and 12 atom% or less. The lower limit of the more preferable range of z is 1.0 atom%, and the upper limit of the range of more preferable z is 8.0 atom%. A more preferable upper limit of the range of z is 6.0 atom%.

Further, as the composition ratio x of Q is higher, the amorphous phase containing Q (for example, B) is more likely to be formed.
It is preferable to increase the composition ratio z of the metal element M. This allows the deposition of soft magnetic iron-based borides with high magnetization,
The grain growth of the generated iron-based boride can be suppressed. Specifically, it is preferable to adjust the composition ratio so as to satisfy z / x ≧ 0.1, and it is more preferable to satisfy z / x ≧ 0.15.

Since Ti has a particularly preferable function, the metal element M always contains Ti. In this case, the ratio (atomic ratio) of Ti to the entire metal element M is preferably 70% or more, more preferably 90% or more.

Although Fe occupies the remaining content of the above-mentioned elements, desired hard magnetic characteristics can be obtained even if a part of Fe is replaced with one or two transition metal elements (T) of Co and Ni. it can. If the substitution amount of T with respect to Fe exceeds 50% (that is, m is 0.5), a high residual magnetic flux density B _{r of} 0.7 T or more cannot be obtained. Therefore, the substitution amount is preferably limited to the range of 0% or more and 50% or less (that is, 0 ≦ m ≦ 0.5). By substituting a part of Fe with Co, the squareness of the demagnetization curve is improved and the Curie temperature of the R ₂ Fe ₁₄ B phase is increased, so that the heat resistance is improved. The preferable range of the Fe substitution amount by Co is 0.5% or more and 40% or less. In addition, Al, Si,
Cu, Ga, Ag, Pt, Au, Pb, V, Cr, M
Although a small amount of n, Nb, Mo, or W does not deteriorate the magnetic properties, the content is preferably 2 atomic% or less.

[Explanation of Method for Manufacturing Compound and Magnet] The Ti-containing nanocomposite magnetic powder obtained as described above is mixed with a binder such as a resin to manufacture a compound for a bonded magnet.

The compound for compression molding is produced, for example, by mixing a thermosetting resin diluted with a solvent and magnetic powder and removing the solvent. The obtained mixture of magnetic powder and resin is crushed to have a predetermined particle size, if necessary. Granules may be obtained by adjusting the crushing conditions and the like. Moreover, you may granulate the powder material obtained by pulverization.

In order to improve the corrosion resistance of the Ti-containing nanocomposite magnetic powder, the surface of the magnetic powder may be subjected to a known surface treatment such as chemical conversion treatment in advance. Furthermore, in order to further improve the corrosion resistance of magnetic powder, the wettability with resin, and the moldability of compounds, various coupling agents such as silane-based, titanate-based, aluminate-based, and zirconate-based, ultrafine ceramic particles such as colloidal silica, and stearin Lubricants such as zincate and calcium stearate may be used, and heat stabilizers, flame retardants, plasticizers and the like may be used.

In the magnet compound, the type of resin and the compounding ratio of magnetic powder are appropriately determined according to the application. Examples of the resin include thermosetting resins such as epoxy resin, phenol resin and melamine resin, and polyamide (nylon 6
6, nylon 6, nylon 12 etc.), polyethylene,
Thermoplastic resins such as polypropylene, polyvinyl chloride, polyester, and polyphenylene sulfide, rubbers and elastomers, and modified products, copolymers, and mixtures thereof can be used.

By using the Ti-containing nanocomposite magnetic powder according to the present invention, it is possible to realize a magnetic powder filling rate higher than the conventional one (for example, more than 80%), and it is possible to fill up to about 90% at the maximum. However, if the filling rate is raised too much, the resin for sufficiently binding the magnetic particles to each other will be insufficient, and the mechanical strength of the bonded magnet will be reduced, and the magnetic particles may fall off during use. ,
It is preferably 85% or less. Further, by using the Ti-containing nanocomposite magnetic powder according to the present invention in compression molding, it is possible to reduce the amount of voids (voids) formed on the surface of the molded body and suppress adverse effects on the resin coating formed on the surface. Benefits are obtained. These molding methods include
A thermosetting resin, a thermoplastic resin, rubber or the like is appropriately used.

[Surface Treatment of Bonded Magnet] By subjecting the bond magnet after molding to a surface treatment, the corrosion resistance and heat resistance of the bonded magnet can be improved. Since the compound according to the present invention is superior in moldability to the conventional compound, it is possible to obtain a bond magnet having a low porosity (void ratio) while ensuring a filling rate equal to or higher than that of the conventional compound. Therefore, it is possible to suppress / prevent the occurrence of the problem of corrosion that accompanies the surface treatment of the as-molded bonded magnet having many voids. Moreover, since the bonded magnet has high corrosion resistance, the cost can be reduced by simplifying the surface treatment.

Further, even when the molded bond magnet has sufficient corrosion resistance, mechanical damage to the bond magnet during the assembly process, such as a compression-molded ring magnet used in a motor, etc., can be prevented. To prevent
In some cases, it is necessary to prevent the adverse effect on the operation of the motor due to the scattering of the magnetic powder that has fallen off the surface of the bonded magnet. In such a case, it is preferable to perform various surface treatments in order to improve the mechanical strength of the bonded magnet and prevent the magnetic powder from falling off.

Even in such a case, since the protective film can be made thin, the dimensional accuracy of the entire bonded magnet including the protective film can be improved, and the effective volume of the magnet can be increased to downsize the component. There is also an advantage. Further, when incorporated in a motor, the magnetic characteristics between the rotor and the stator can be reduced, so that the motor characteristics can be improved.

As the surface treatment method, widely known methods can be used. The protective film formed by surface treatment is an inorganic material (metal, ceramic, inorganic polymer, etc.)
However, organic materials (low molecular weight, high molecular weight, etc.) and inorganic / organic composite materials can also be used. These protective films can be formed by various methods depending on the material used.

For example, the metal film is formed by plating (electrolytic plating, electroless plating, etc.), various thin film deposition techniques (vacuum vapor deposition, ion plating, sputtering, ion beam, etc.), Sn and Zn. It is possible to employ a method of immersing in a molten metal having a low melting point such as and cooling.

The film of the ceramic material may be formed by using a thin film deposition technique as in the case of the metal film. Alternatively, a treatment liquid in the case of using the sol-gel method or an aqueous solution of alkali silicate may be used, and a dipping method or a spray method may be used. It may be formed using a method or the like. Alternatively, an electrophoretic electrodeposition method or the like may be adopted.

The resin film can be formed using an organic polymer material by various methods such as electrodeposition coating, spray coating, electrostatic coating, dip coating and roll coating. Also,
A film of an inorganic polymer material (for example, silicone resin) can be formed by the same method.

The protective film can also be formed using a low molecular weight organic material such as a coupling agent (silane type, titanate type, aluminate type, zirconate type) or benzotriazole. These low molecular weight organic materials are
It can be applied as a solution to the bonded magnet by various methods.

Fine particles are deposited (deposited) by various methods.
By doing so, a protective film can be formed. The fine particles include Al, Zn, Ni, Cu, Fe, Co, S
n, Pb, Au, Ag, etc., metal fine particles, SiO ₂ , A
Metal oxides and composite metal oxides (including glass) such as 1 ₂ O ₃ , ZrO ₂ , MgO, TiO ₂ , mullite, titanate, and silicate, TiN, AlN, BN, TiC, T.
Examples thereof include ceramic fine particles such as iCN and TiB ₂ , resin fine particles such as polytetrafluoroethylene and acrylic resin, carbon black and MoS ₂ .

A binder may be used if necessary in order to fix these fine particles to the surface of the bonded magnet. As the material of the binder, inorganic materials such as chromic acid, molybdic acid, phosphoric acid and salts thereof, low molecular weight organic compounds such as coupling agents, polymer compounds such as organic resins and the like can be used.

As a method of fixing the fine particles on the surface of the bond magnet, a mixture of fine particles and a binder may be applied by a coating method such as a spraying method or a dipping method, or a binder previously formed on the surface of the bond magnet. Fine particles may be attached to the layer by using mechanical force. If necessary, heat treatment may be performed to further firmly fix the fine particles to the surface of the bond magnet.

The protective film may be formed not only as a new film on the as-molded bond magnet but also by modifying the surface of the bond magnet. The reaction with the magnetic powder on the surface of the bonded magnet may be used. For example, various chemical conversion treatments such as phosphoric acid treatment, zinc phosphate treatment, manganese phosphate treatment, calcium phosphate treatment, phosphoric acid chromate treatment, chromic acid treatment, zirconic acid treatment, tungstic acid treatment and molybdic acid treatment can be mentioned. .

Since the content of the rare earth element (typically Nd) in the Ti-containing nanocomposite magnetic powder according to the present invention is low, sufficient corrosion resistance can be obtained even by using the chemical conversion treatment generally used in the field of steel. Can be obtained.

Further, the surface of the bonded magnet may be oxidized by various methods to form an oxide film having an appropriate thickness.

Further, as described above, the bonded magnet of the present invention is essentially excellent in corrosion resistance because it can reduce voids.
Moreover, although suitable for various surface treatments, various sealing treatments may be performed in order to further improve the reliability of the magnet when used in a harsh environment.

Further, the above-mentioned surface treatments may be appropriately combined, and for example, a laminated film may be formed by using different materials.

The thickness of the protective film is appropriately set according to the surface treatment method used and the application of the bond magnet, but the effect of improving the energy efficiency by reducing the magnetic gap in the above-mentioned motor is obtained. In order to obtain it, the thickness of the protective film is preferably 25 μm or less, more preferably 20 μm or less, still more preferably 10 μm or less.
μm or less.

Hereinafter, Examples 1 and 2 of the present invention and Comparative Examples 1 to 4 will be described.

Examples 1 and 2 and Comparative Example 1
3 to 3 use Ti-containing nanocomposite magnetic powder, and Comparative Example 4 is MQP-B manufactured by MQI, which is a conventional quenched alloy powder.
Is crushed to a maximum particle size of 250 μm or less before use.

The Ti-containing nanocomposite magnetic powders used in Examples 1 and 2 and Comparative Examples 1 to 3 were prepared as follows.

First, Nd: 9 atom%, B: 11 atom%,
After charging 5 kg of a raw material compounded so as to have an alloy composition of Ti: 3 atomic%, Co: 2 atomic% and the balance Fe into the crucible,
A molten alloy was obtained by high frequency induction heating in an Ar atmosphere maintained at 50 kPa.

By tilting the crucible, the molten alloy was directly supplied through a chute to a cooling roll made of pure copper (diameter 250 mm) rotating at a roll surface peripheral speed of 15 m / sec to quench the molten alloy. To do. In addition, the molten metal supply rate at that time is 3 k by adjusting the tilt angle of the crucible.
Adjusted to g / min.

With respect to the obtained quenched alloy, the thickness of 100 scales (alloy ribbon) was measured with a micrometer.
The average thickness of the quenched alloy is 70 μm, and its standard deviation σ is 1
It was 3 μm. After the obtained quenched alloy is pulverized to 850 μm or less, a hoop belt furnace having a soaking zone with a length of about 500 mm is used and the belt feed rate is 100 m under Ar flow.
Heat treatment was performed by introducing the powder into the furnace maintained at 680 ° C. at m / min at a supply rate of 20 g / min to obtain magnetic powder.

It was confirmed by a powder X-ray diffraction method that the obtained magnetic powder was a Ti-containing nanocomposite magnetic powder.
The obtained X-ray diffraction pattern is shown in FIG. As can be seen from FIG. 9, Nd ₂ Fe ₁₄ B phase and Fe ₂₃ B ₆ and α-Fe
Was confirmed.

Then, as described above with reference to FIGS. 7 and 8, the obtained magnetic powder was used to prepare a Ti-containing nanocomposite magnetic powder having an aspect ratio of 0.4 or more and 1.0 or less using a pin disk mill. did. The aspect ratio was determined by SEM observation. The aspect ratio of the magnetic powder of Comparative Example 4 (particles having a particle size of at least 106 μm) was less than 0.3.

The obtained Ti-containing nanocomposite magnetic powder was classified by a standard sieve and adjusted to the particle size distribution shown in Table 1, respectively. Histograms showing the particle size distributions of the magnetic powders used in this example and comparative example are shown in FIGS. The average particle diameter of each magnetic powder is as shown in Example 1: more than 106 μm 12
5 μm or less, Example 2: more than 106 μm and 125 μm or less,
Comparative Example 1: More than 75 μm and 106 μm or less, Comparative Example 2:53
Over 75 μm and below, Comparative Example 3: Over 75 μm and 106 μm
Hereinafter, Comparative Example 4: more than 125 μm and 150 μm or less.

[0177]

[Table 1]

2% by mass of an epoxy resin was added to the magnetic powders of Examples 1 and 2 and Comparative Examples 1 to 4 and mixed and kneaded.
0.1 mass% of calcium stearate was added as a lubricant to obtain a compound for bonded magnet. 980 MPa
Compression molding at a pressure of (10 ton / cm ² ) for 10 m
A molded body having a shape of mφ × 7 mm was obtained. This molded body was cured in air at 150 ° C. for 1 hour to obtain a bonded magnet. Density of each of the obtained bonded magnets of Examples and Comparative Examples (molded body density: mass of molded body / volume of molded body)
Table 2 shows the magnetic properties together with the bulk specific gravity of each magnetic powder.

[0179]

[Table 2]

With reference to Table 2, first, Examples 1 and 2 are compared with Comparative Example 4 (conventional quenched alloy powder).
The magnetic powder of Comparative Example 4 has a lower bulk specific gravity than the magnetic powder of Examples 1 and 2. Further, as is clear from the comparison of the densities of the bonded magnets, the density of the bonded magnet of Comparative Example 4 is lower than the densities of the bonded magnets of Examples 1 and 2. Since the densities of the magnetic particles are the same, this indicates that the bonded magnet of Comparative Example 4 contains more voids. This is
Among the magnetic powders of Comparative Example 4, particles having a particle size of more than 106 μm have an aspect ratio of less than 0.3, that is, a particle size of 1
Particle thickness of more than 06μm (corresponding to the length of the minor axis) is 30μ
It is considered that the reason is less than m.

Optical microscope photographs of the cross sections of the bonded magnet of Example 1 and the bonded magnet of Comparative Example 4 are shown in FIGS. 11 and 12, respectively.

As can be seen from FIG. 11, Ti of Example 1
The contained nanocomposite magnetic powder is produced by crushing an alloy ribbon having an average thickness of 50 μm or more and 120 μm or less (here, 70 μm), and has a particle size of 106 μm.
The aspect ratio of the powder particles exceeding μm is 0.4 or more, that is, the length of the minor axis of the powder particles having a particle size exceeding 106 μm is 50 μm or more. Therefore, as described above, relatively small particles (second particles) are efficiently filled in the gaps between relatively large particles (first particles). In contrast,
As can be seen from FIG. 12, since the magnetic powder of Comparative Example 1 is composed of particles having an aspect ratio of less than 0.3, the gap formed by the first particles is flat or the first particles are densely arranged, The second particles are not uniformly dispersed between the first particles. As described above, the formability can be improved by using the Ti-containing nanocomposite magnetic powder having an aspect ratio of 0.3 or more, preferably 0.4 or more, for the powder particles having a particle size of more than 106 μm.

In addition, the bonded magnets of Examples 1 and 2,
Comparing the magnetic characteristics of the bonded magnets of Comparative Example 4, the coercive force H _cJ is superior in Comparative Example 4, but the residual magnetic flux density B
_{Both the r} and the maximum energy product (BH) _max are excellent in the bonded magnet of the example. Furthermore, in the bonded magnet of Comparative Example 4, large particles were shed. Further, the reliability of the bonded magnet of the comparative example is poor as described above.

Next, Examples 1 and 2 and Comparative Examples 1 to 3
Compare with.

As can be seen from Table 2, Examples 1 and 2
The bulk specific gravity of the magnetic powder and the density (molded body density) of the bonded magnet are higher than those of Comparative Examples 1 to 3. this is,
The magnetic particles of Examples 1 and 2 have a particle size of more than 106 μm and 150.
This is because it has a peak in the range of μm or less (FIG. 10).
reference). In addition, the magnetic powder of Comparative Example 4 was 10
It has a peak in the range of more than 6 μm and 150 μm or less,
Since the aspect ratio of the powder particles having a particle size exceeding 106 μm is less than 0.3 (thickness is less than 30 μm), sufficient moldability (fillability) cannot be obtained even if the particle size distribution is adjusted.

Since the magnetic powders of Comparative Examples 1 and 2 have a peak particle size of 106 μm or less, they are slightly inferior in moldability to the magnetic powders of Examples 1 and 2. On the other hand, Comparative Example 3
Since the magnetic powder of No. 1 has a particle size showing the first peak of more than 150 μm, there is a problem that the magnetic powder is likely to be shed.

Comparing Example 1 and Example 2, Example 2 is superior in moldability. It is considered that this is because the first peak is in the range of more than 106 μm and 150 μm or less and the second peak is in the range of 53 μm or less as described above. That is, it is considered that the gaps formed by the first particles forming the first peak are efficiently filled with the second particles forming the second peak.

Further, in order for the first particles to form the gap in which the second particles are efficiently filled, the particle size is more than 53 μm and 10 or more.
It is considered preferable that the number of particles of 6 μm or less is small. That is, since there is a correlation between the sizes of the first particles forming the gap and the second particles filled in the gap, the abundance ratios of the first particles and the second particles are not continuous, that is, the first particles are not continuous. It is considered preferable that there are few particles having a particle size intermediate between those of the particles and the second particles. Further, the magnetic powder preferably contains more first particles than the second particles on a volume basis, and it is preferable that the number of particles of more than 106 μm and 150 μm or less is three times or more that of particles of 53 μm or less. However, 10
If the number of particles having a size of more than 6 μm and 150 μm or more exceeds 5 times that of particles having a size of 53 μm or less, the second particles filled in the gaps between the first particles are insufficient, and as a result, the filling efficiency decreases, which is not preferable.

[0189]

According to the present invention, there are provided a rare earth alloy powder and a compound for a bonded magnet, which are used for a bonded magnet having excellent formability and magnetic properties, and a bonded magnet using the compound.

The rare earth alloy powder for a bonded magnet according to the present invention uses a Ti-containing nanocomposite magnetic powder having excellent magnetic properties despite having a relatively low rare earth element content, and has a particle size excellent in formability. Because it has a distribution
A high-performance bonded magnet can be provided at low cost. Especially, for example, the outer diameter is 4 mm to 20 mm and the inner diameter is 2 mm to 1.
It is suitable for use as a small ring magnet having a size of 8 mm and a thickness of about 0.5 mm to 2 mm, and can provide a small bond magnet with high performance and high reliability.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the maximum magnetic energy product (BH) _{max of an} Nd-Fe-B nanocomposite magnet to which Ti is not added and the boron concentration. In the graph, white bars represent data for samples containing 10-14 atomic% Nd, and black bars represent data for samples containing 8-10 atomic% Nd.

FIG. 2 is a graph showing the relationship between the maximum magnetic energy product (BH) _max and the boron concentration of a Nd-Fe-B nanocomposite magnet containing Ti. In the graph, white bars represent data for samples containing 10-14 atomic% Nd, and black bars represent data for samples containing 8-10 atomic% Nd.

FIG. 3 is a schematic diagram showing an R ₂ Fe ₁₄ B type compound phase and a (Fe, Ti) -B phase in a magnet according to the present invention.

FIG. 4 shows the case of adding Ti and N instead of Ti.
It is a figure which shows typically the change of the microstructure in the crystallization process of a rapidly solidified alloy when b etc. are added.

FIG. 5 (a) is a cross-sectional view showing an example of the overall configuration of an apparatus used in a method for producing a quenched alloy for iron-based rare earth alloy magnets according to the present invention, and FIG. 5 (b) is a portion where rapid solidification is performed. FIG.

FIG. 6 (a) is a perspective view schematically showing an alloy before crushing and powder particles after crushing according to the present invention, and FIG.
FIG. 3 is a perspective view schematically showing an alloy before crushing and powder particles after crushing in the related art.

FIG. 7 is a diagram showing a configuration of a pin mill device used in the embodiment of the present invention.

8 is a diagram showing a pin arrangement of the pin mill device shown in FIG. 7. FIG.

FIG. 9 is a view showing an X-ray diffraction pattern of Ti-containing nanocomposite magnetic powders used in Examples and Comparative Examples.

FIG. 10 is a histogram showing a particle size distribution of magnetic powder used in Examples and Comparative Examples.

11 is an optical microscope photograph of a cross section of the bonded magnet of Example 1. FIG.

12 is an optical microscope photograph of a cross section of a bonded magnet of Comparative Example 4. FIG.

[Explanation of symbols]

1b, 2b, 8b, and 9b Atmospheric gas supply port 1a, 2a, 8a, and 9a gas outlets 1 Melting chamber 2 quenching room 3 melting furnace 4 Hot water storage container 5 Hot water nozzle 6 funnel 7 rotating cooling rolls 21 molten metal 22 alloy

Continued front page    F term (reference) 4K017 AA04 BA06 BB06 BB09 BB12                       BB13 CA03 CA07 DA04 EA03                       EC02                 4K018 BA18 BB01 BB04 BB06 BC08                       BD01 KA46                 5E040 AA04 AA19 BB04 BB05 CA01                       HB17 NN01 NN06

Claims (9)

[Claims] 1. A composition formula (Fe _1-m T _m ) _100-xyz Q _x R _y
M _z (T is 1 selected from the group consisting of Co and Ni
One or more elements, Q is one or more elements selected from the group consisting of B or B and C, R is one or more rare earth elements substantially free of La and Ce, M is Ti, Zr,
And Hf, which is a metal element selected from the group consisting of Hf and at least one metal element necessarily containing Ti, and composition ratios x, y, z, and m are 10 <x ≦ 20 atomic% and 6 <y, respectively. <10 atomic%, 0.1 ≦ z ≦ 12 atomic%,
And 0 ≦ m ≦ 0.5), and the average crystal grain size of the hard magnetic phase is 10 nm or more and 200 nm.
Below, the average crystal grain size of the soft magnetic phase is 1 nm or more and 100 nm.
Includes powder particles having a structure containing two or more types of ferromagnetic crystal phases within the following range, and having a particle size distribution having a first peak in the range of more than 106 μm and 150 μm or less, Is less than 106 μm, the aspect ratio of the powder particles is in the range of 0.3 or more and 1.0 or less. 2. The particle size distribution has a particle size of 53 μm.
The rare earth alloy powder for a bonded magnet according to claim 1, which has a second peak in the following range. 3. The average particle diameter of the powder particles is more than 53 μm 1
The rare earth alloy powder for a bonded magnet according to claim 1, which is in a range of 25 μm or less. 4. The average thickness of the powder particles having a particle size of more than 106 μm is in the range of 50 μm or more and 120 μm or less,
The rare earth alloy powder for bonded magnets according to any one of claims 1 to 3. 5. The rare earth alloy powder for a bonded magnet according to claim 1, wherein the powder particles have an aspect ratio of 0.4 or more. 6. The rare earth alloy powder for a bonded magnet according to claim 1, wherein the powder particles are produced by a strip casting method. 7. The powder particles according to claim 6, wherein the powder particles are produced by crushing an alloy ribbon having an average thickness of 50 μm or more and 120 μm or less obtained by a strip casting method. Rare earth alloy powder for bonded magnets. 8. A compound for a bonded magnet, which comprises the rare earth alloy powder for a bonded magnet according to claim 1 and a binder. 9. A bond magnet formed using the compound for a bond magnet according to claim 8.