JPH1053844A - (rare earth)-iron-boron magnetic alloy and its production and bond magnet using the (rare earth)-iron-boron magnetic alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high residual magnetic flux density and high coercive force by specifying the composition of elements and the constitution of alloy structure, respectively. SOLUTION: This alloy has a composition represented by the formula, Rx Fe100-x-y-z-w COy Mz Bw [where R is one or more kinds among five rare earth elements such as Nd, M is one or more kinds among 14 elements such as Ti, and 5<=x<=10, 0<=y<=9.0, 0.1<=z<=5, 2<=w<=7, 9<=(x+w), and 5<(y+z) are satisfied]. Moreover, this alloy has an alloy structure in which soft magnetic crystalline phases, containing solid solution of αFe, bccFe, and the above M, and hard magnetic crystalline phases, composed of Nb2 Fe14 B1 type tetragonal system crystal, are precipitated in soft magnetic amorphous phases, respectively. Further, by regulating the area ratios of these amorphous phases and crystalline phases to respectively prescribed values, residual magnetic flux density as high as >=10kG and coercive force as high as >=3.5kOe can be obtained, and, as a result the alloy, having high maximum energy product and excellent in rust- preventing property, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention has a high residual magnetic flux density Br, especially 10 kG or more, and a large coercive force iHc, especially 3.5 kOe or more, so that the maximum energy product (BH) is obtained. The present invention relates to a rare-earth-iron-boron-based magnet alloy having a large max and excellent in rust prevention, a method for producing the same, and a bonded magnet using the rare-earth-iron-boron-based magnet alloy.

[0002]

2. Description of the Related Art Bond magnets have been widely used in various applications such as electric products and automobile parts because of their advantages such as flexibility in shape and high dimensional accuracy. 2. Description of the Related Art In recent years, with the reduction in size and weight of electric products and automobile parts, there has been a strong demand for miniaturization of the bonded magnet itself used for the same.

[0003] For that purpose, it is strongly required that the magnets have high performance, that is, have high residual magnetic flux density Br and large coercive force iHc, and as a result, have a large maximum energy product (BH) max. .

[0004] Bond magnets using magnetoplumbite-type ferrite that have been widely used as bond magnets (hereinafter referred to as ferrite bond magnets) have excellent corrosion resistance because ferrite powder is an oxide. Since it is manufactured using inexpensive raw materials such as oxides such as barium and strontium and iron oxides, it is economical,
Widely used.

However, the magnetic properties of this ferrite bonded magnet are usually such that the residual magnetic flux density Br is about 2-3 kG, the coercive force iHc is about 2-3 kOe, and the maximum magnetic energy product (BH) max is 1.6. Ｍ2.3 MGOe.

Recently, there has been no limit to the demand for higher performance and lower cost of magnets. Therefore, the development of a rare earth-iron-boron exchange spring magnet alloy using Nd as a rare earth element has been actively pursued. It has already been put to practical use.

The above exchange spring magnet exhibits a magnetic spring phenomenon due to exchange interaction between iron or an iron compound and a Nd ₂ Fe ₁₄ B ₁ type tetragonal compound.
The feature is that it has a low rare earth content and a high residual magnetic flux density Br, and it is highly likely that the magnet will be excellent in cost performance.

That is, a rare earth-iron-boron exchange spring magnet alloy having a rare earth content of less than 10 atomic% such as Nd is, for example, a commercially available “MQP” developed by General Motors.
Compared to a rare earth-iron-boron magnet alloy having a rare earth content such as Nd of 10 to 15 atomic%, which is close to the stoichiometric composition, such as (trade name), the potential of the magnetic properties is higher and the expensive rare earth is more expensive. It is economical because it can be reduced.

The rare-earth-iron-boron exchange spring magnet alloy having a rare-earth content of less than 10 atomic%, such as Nd, includes a soft magnetic phase containing αFe or bccFe as a soft magnetic phase.
There is a system containing ₃ B or Fe ₂ B. In the former, the residual magnetic flux density Br is generally as high as 10 to 13 kG, but the coercive force iHc is as low as at most less than 3.5 kOe. In the latter, the coercive force iHc is generally as high as 3.5 to 7.7 kOe. Since the residual magnetic flux density Br is about 10 kG or less,
The residual magnetic flux density Br is higher than that of “MQP”, but αFe
It is lower than the main system.

In the field of small motors and the like, which are the main applications of bonded magnets using rare earth-iron-boron magnet alloys, residual magnetic flux is required from the viewpoint of downsizing the motor and magnetic stability of the magnet used. The magnetic properties are such that the density Br and the coercive force iHc are balanced, that is, the residual magnetic flux density Br is 10 kG or more, and the coercive force iHc is 3.5 kOe.
It is strongly required that this be done.

Further, an alloy containing an Nd-based rare earth element has a drawback that it is easily oxidized in air to gradually produce a stable oxide, and is inferior in rust prevention. Therefore, bonded magnets manufactured using alloys containing Nd-based rare earths have poor corrosion resistance, and are generally provided with a rustproof coating such as resin-based dipping, spray coating, electrodeposition coating or metal plating. Is common.

Therefore, if the rust prevention of an alloy containing a Nd-based rare earth element is improved, it is expected that the rust prevention coating on the bonded magnet surface can be simplified or omitted even in the above-mentioned applications. Further, for example, there is a possibility that the rust prevention coating can be omitted depending on the use of a general-purpose motor or the like.

Therefore, a rare earth-iron-boron magnet having a high residual magnetic flux density Br and a relatively large coercive force iHc, resulting in a large maximum energy product (BH) max and excellent rust prevention properties There is a strong demand that the alloy be obtained economically.

Conventionally, in a quenched permanent magnet material containing Fe as a main component (but less than 91 at%) and containing one or more rare earth elements (R) and boron (B), 10 area% There is known a permanent magnet material containing the following soft magnetic residual amorphous phase, and the balance substantially consisting of a crystalline phase formed by heat treatment and containing an R—Fe—B-based hard magnetic compound (Japanese Patent Application Laid-Open No. H8-208). 162,212).

[0015]

SUMMARY OF THE INVENTION High residual magnetic flux density Br
And a relatively large coercive force iHc. As a result, a rare-earth-iron-boron-based magnet alloy having a large maximum energy product (BH) max and excellent rust prevention properties is currently most demanded. However, a magnet having such characteristics has not yet been obtained.

That is, the rare-earth-iron-boron-based magnet alloy described in the above-mentioned Japanese Patent Application Laid-Open No. 8-162312 has a residual magnetic flux density Br of 0.62 to 0.97 T (6.
It corresponds to 2 to 9.7 kG. ), The coercive force iHc is 0.16 to 0.21 MA / m (1.25 to 2.6 kOe).
Is equivalent to ) Degree, maximum magnetic energy product (BH) m
ax is 19.7 to 72.0 kJ / m ³ (2.5 to 9.0
MGOe. ), The coercive force iHc was as low as about 3 kOe and the residual magnetic flux density Br was as low as about 10 kG at most.

The rare earth-iron-boron magnet alloys described in Examples 2 to 4 of JP-A-8-162212 are obtained by pulverizing a quenched ribbon and extruding it in a vacuum. Rare earth-iron-according to the present invention.
It is different in form from a boron-based magnet alloy.

Therefore, the present invention provides a high residual magnetic flux density Br.
And a large coercive force iHc. As a result, it is possible to economically obtain a rare earth-iron-boron magnet alloy having a large maximum magnetic energy product (BH) max and excellent rust prevention. Make it an issue.

[0019]

The above technical objects can be achieved by the present invention as described below.

That is, the present invention relates to a compound of the formula R _x Fe _100-xyzw
Co _y M _z B _w (where, R represents, Nd, Pr, Dy, Tb
And one or more rare earth elements selected from Ce,
M is Ti, V, Cr, Zr, Nb, Mo, Hf, T
a, W, Mn, one or more elements selected from Cu, Ga, Ag, and Si, x, y, z, and w are respectively 5 ≦ x ≦ 10, 1.0 ≦ y ≦ in atomic ratio. 9.0, 0.1
≦ z ≦ 5, 2 ≦ w ≦ 7, and 9 ≦ (x + w), 5 <
(Y + z)), and αFe,
Each of a soft magnetic crystal phase containing bccFe and a solid solution of these and M and a hard magnetic crystal phase composed of a Nd ₂ Fe ₁₄ B ₁ type tetragonal crystal is precipitated in the soft magnetic amorphous phase. An alloy structure, wherein the soft magnetic amorphous phase accounts for 10% by area or less of the total alloy structure, and the balance is the soft magnetic crystal phase and the hard magnetic crystal phase; A rare earth-iron-boron magnet alloy having a crystal phase of at least 50% by area with respect to the whole crystal structure and the remainder being the hard magnetic crystal phase, and a coercive force iHc of 3.5.
The rare-earth-iron-boron-based magnet alloy has a kOe or more, a residual magnetic flux density Br of 10 kG or more, and a maximum magnetic energy product (BH) max of 13 MGOe or more.

The present invention also relates to a compound of the formula R _x Fe _100-xyzw
Co _y M _z B _w (where, R represents, Nd, Pr, Dy, Tb
And one or more rare earth elements selected from Ce,
M is Ti, V, Cr, Zr, Nb, Mo, Hf, T
a, W, Mn, one or more elements selected from Cu, Ga, Ag, and Si, x, y, z, and w are respectively 5 ≦ x ≦ 10, 1.0 ≦ y ≦ in atomic ratio. 9.0, 0.1
≦ z ≦ 5, 2 ≦ w ≦ 7, and 9 ≦ (x + w), 5 <
(Y + z)) An alloy produced so as to have a composition ratio represented by (y + z) is heated and melted to form a molten metal, rapidly solidified, and then heat-treated in a temperature range of 600 to 850 ° C. The method for producing the rare earth-iron-boron magnet alloy comprises:

Further, the present invention provides a bonded magnet obtained by molding a magnet alloy powder obtained by pulverizing the rare earth-iron-boron magnet alloy using a resin as a binder, wherein the magnet alloy powder is It is a bonded magnet that is mixed and blended at a ratio of 85 to 99% by weight.

The structure of the present invention will be described in more detail as follows.

First, the rare earth-iron-boron magnet alloy according to the present invention will be described.

The alloy composition of the rare earth-iron-boron magnet alloy according to the present invention will be described.

The rare earth according to the present invention - iron - composition of boron-based permanent magnet, wherein _{R x Fe 100-xyzw Co y} M z
Represented by B _w. Wherein R is Nd, Pr, Dy, Tb
And one or more rare earth elements selected from Ce and Ce, and the amount thereof is 5 ≦ x ≦ 10 in atomic ratio. Considering the residual magnetic flux density Br and the coercive force iHc, Nd, Pr,
Nd-Pr alloys and mixtures of these with other rare earth elements are preferred, with Nd and Pr being most preferred. However,
Rare earth elements other than the above are 10 atomic% based on the total rare earth amount.
The following may be included.

The amount of R satisfies 5 ≦ x ≦ 10, preferably 5.5 ≦ x ≦ 9, and more preferably 6 ≦ x ≦ 8. x
Is less than 5, the precipitation amount of the hard magnetic crystal phase composed of the Nd ₂ Fe ₁₄ B ₁ type tetragonal crystal is insufficient, and if the coercive force does not exceed 3.5 kOe and exceeds 10, , Α
The amount of precipitated soft magnetic crystal phase including Fe, bccFe and a solid solution of these and M is insufficient, and a high residual magnetic flux density of Br ≧ 10 kG or more cannot be obtained.

The Fe content is in the range of 69 to 86 in atomic ratio. If it is less than 69, the residual magnetic flux density Br decreases,
The target of 10 kG or more of the present invention cannot be obtained. When it exceeds 86, the amount of R and the amount of Co are relatively reduced, and the coercive force iHc, which is the object of the present invention, is 3.5 kO.
e or more cannot be obtained.

Co is an essential element because it increases the coercive force, the magnetization, the corrosion resistance, and the Curie point together with the M element.

The amount of Co is 1.0 ≦ y ≦ 9.0, preferably 1.5 ≦ y ≦ 9.0, and more preferably 2.0 ≦ y ≦ 9.0.
y ≦ 9.0. If it is less than 1.0, the coercive force and the Curie point are not sufficiently increased, resulting in poor thermal stability. If it exceeds 9.0, the residual magnetic flux density B due to the decrease in iron-based components
The decrease of r becomes remarkable, and 10 kG or more cannot be obtained.

M is Ti, V, Cr, Zr, Nb, M
o, Hf, Ta, W, Mn, Cu, Ga, Ag and Si
One or two or more rare earth elements selected from the group consisting of: increasing the magnetocrystalline anisotropy of a hard magnetic crystal phase composed of a tetragonal crystal of Nd ₂ Fe ₁₄ B ₁ type; A large coercive force can be obtained by the effect. Also, αF
The soft magnetic crystal phase containing e, bccFe and a solid solution of these and M can be stabilized to improve the corrosion resistance and thermal stability of the permanent magnet.

When Mn, Cu, Ga, Ag and Si are added together with other M elements, a larger coercive force can be obtained due to the synergistic effect.

The amount of the element M is 1 ≦ z ≦ 5, preferably 0.2 ≦ z ≦ 4, more preferably 0.3 ≦ z ≦ 3.5.
It is. If it is less than 1, the effect of improving the coercive force is poor, and the thermal stability is poor. If it exceeds 5, Br will decrease due to a decrease in iron-based components.

Of the above M elements, Ti, Zr, Nb, H
f, Ta, Si and Ga contribute to the improvement of the coercive force, easily form an amorphous phase, the amorphous phase remains stably in the alloy, the corrosion resistance is exhibited, and the rust prevention is excellent. Magnet material is obtained.

B is an essential element for constituting a hard magnetic crystal phase composed of a Nd ₂ Fe ₁₄ B ₁ type tetragonal crystal, and its amount is 2 ≦ w ≦ 7, preferably 2. 5 ≦
w ≦ 6.5, more preferably 3 ≦ w ≦ 6. If it is less than 2, the precipitation amount of the hard magnetic crystal phase composed of the Nd ₂ Fe ₁₄ B ₁ type tetragonal crystal becomes insufficient, and iHc ≧ 3.5.
It does not become kOe. If it exceeds 7, B becomes excessive and the residual magnetic flux density Br decreases.

The sum of the R amount and the B amount is 9 ≦ (x + w), and is preferably 10 or more. If it is less than 9, a sufficient soft magnetic amorphous phase is not formed by quenching, and iHc ≧ 3.5 kOe cannot be realized even by heat treatment. In consideration of maintaining a high residual magnetic flux density Br, the upper limit is preferably 15 and more preferably 14.

The sum of the amount of Co and the amount of M satisfies 5 <(y + z), preferably 5.1 or more, more preferably 5.5 or more. If it is 5 or less, the effect of improving the coercive force and the thermal stability is hardly obtained. In consideration of maintaining a high residual magnetic flux density Br, the upper limit is preferably 11 and more preferably 10.

The alloy structure of the rare earth-iron-boron magnet alloy according to the present invention will be described.

The rare earth-iron-boron magnet alloy according to the present invention has a soft magnetic amorphous phase of 10 area% or less based on the entire alloy structure.

The soft magnetic amorphous phase is composed of 8 to 20 atomic% of rare earth, 70 to 90 atomic% of iron or an alloy of iron and the above element M, and 25 atomic% or less of boron. Since this soft magnetic amorphous phase has soft magnetism and can suppress the coarse growth of crystal grains and form a fine crystal phase in the heat treatment step for crystallization, The overall hard magnetism can be improved.

Further, since each of the soft magnetic crystal phase and the hard magnetic crystal phase is dispersed and precipitated in an island shape in the soft magnetic amorphous phase, the soft magnetic amorphous phase mainly has a magnetic role. Suppresses the progress of oxidation because it surrounds the soft magnetic crystal phase and the hard magnetic crystal phase, which is responsible for the effect of rust. it can.

When the soft magnetic amorphous phase exceeds 10 area% in the two-dimensional observation field of view of the entire alloy structure, the distance over which the magnetic exchange interaction between the soft magnetic crystal phase and the hard magnetic crystal phase can reach. Therefore, the magnetic coupling is weakened, and the effect of improving the magnet characteristics cannot be obtained. Considering the rust-preventing effect of the soft magnetic amorphous phase, the lower limit is preferably 1% by area.

The soft magnetic amorphous phase can be expected to have sufficient effects such as mechanical strength and chemical resistance normally possessed by the amorphous phase.

The soft magnetic crystal phase in the rare earth-iron-boron magnet alloy according to the present invention contains αFe, bccFe and a solid solution of these and M, and contains at least 50% by area of the entire crystal structure. . The soft magnetic crystalline phase
This contributes to the improvement of the residual magnetic flux density Br. If it is less than 50 area%, the high residual magnetic flux density B
A magnet alloy having r cannot be obtained. Coercive force iH
In consideration of the ratio of the hard magnetic crystal phase that plays a role of improving c, the upper limit is preferably 90 area%.

The crystal grain size of the soft magnetic crystal phase is 10 to 100.
nm, and more preferably in the range of 15 to 50 nm.

The soft magnetic crystalline phases include αFe, bccFe and solid solutions of these and M, as well as Fe ₃ B, Fe
₂ B, a solid solution of these with M, further, may be an intermetallic compound of Fe and M such as Fe ₂ Zr is contained on the inevitable condition diagrammatically or manufacturing process, but an object of the present invention There is no particular problem in obtaining a magnetic alloy having various characteristics.

The crystal size of the soft magnetic crystal phase which may be inevitably contained is preferably 100 nm or less, more preferably in the range of 15 to 35 nm.

The hard magnetic crystal phase in the rare earth-iron-boron magnet alloy according to the present invention is composed of Nd ₂ Fe ₁₄ B ₁ type tetragonal crystal and accounts for less than 50 area% of the entire crystal structure.

This hard magnetic crystal phase has an effect of expressing the coercive force Hc. Also, part of the M element may enter the hard magnetic crystal phase and improve the anisotropy constant.

If it exceeds 50% by area, the soft magnetic crystal phase becomes small, and a large residual magnetic flux density Br cannot be obtained.
Preferably it is 40 area% or less. Considering the coercive force iHc value which is the object of the present invention, the lower limit is 10
Area% is preferred.

The hard magnetic crystal phase may contain, in addition to the Nd ₂ Fe ₁₄ B ₁ type compound, a minute compound phase which inevitably precipitates in a phase diagram.

The crystal grain size of the hard magnetic crystal phase is preferably 100 nm or less, more preferably in the range of 10 to 50 nm.

The rare earth-iron-boron magnet alloy according to the present invention having the above alloy composition and the above alloy structure has a residual magnetic flux density Br of 10 kG or more, preferably 10.5 kG or more, and a coercive force iHc of 3.5 kOe. Or more, preferably 4.0 kOe or more, and the maximum energy product (BH) m
ax has 13 MGOe or more, preferably 15 MGOe or more. The upper limit is that the residual magnetic flux density Br is 13 k.
G, coercive force iHc is 8 kOe, maximum energy product (B
H) The max is 25MGOe.

Further, the rust prevention property is determined, for example, according to JIS Z 2
According to the salt spray test method based on 371, the elapsed time until rust accounts for 10 area% is at least 50 hours or more,
It is preferably 55 hours or more, more preferably 60 hours or more, and is clearly superior to the conventional Nd-Fe-B-based alloy as shown in Examples below.

Next, the rare earth according to the present invention, as described above,
A method for producing an iron-boron magnet alloy will be described.

The formula R _x Fe _100-xyzw Co _y M _z B
_w (where R is one or two or more rare earth elements selected from Nd, Pr, Dy, Tb and Ce, M is Ti,
V, Cr, Zr, Nb, Mo, Hf, Ta, W, Mn,
One, two or more elements selected from Cu, Ga and Si, x, y, z and w are each in atomic ratio of 5 ≦ x ≦ 1.
0, 1 ≦ y ≦ 9, 0.1 ≦ z ≦ 5, 2 ≦ w ≦ 7, and
An alloy is manufactured using a metal-like element raw material or an alloy-like raw material so as to have a composition ratio represented by 9 ≦ (x + w) and 5 <(y + z).

As the raw material of the metallic element, commercially available ones may be used, and the form may be various forms such as powder, lump, flake, plate and the like, and any of them can be used.

As the alloy-like raw material, commercially available ones may be used. For example, ferrobon for the boron element and ferroneody, misch metal, dymium and the like for the rare earth element may be used. There are various forms such as powder, lump, piece, and plate, and any of them can be used.

An alloy is manufactured from the above-mentioned metallic element raw material or alloy raw material blended so as to have the above composition ratio by a known arc melting method, high frequency melting method, or the like. These dissolutions
It is preferable to carry out in a vacuum or in an inert atmosphere such as argon gas.

The obtained alloy is heated and melted to obtain a molten alloy. The heating temperature at this time may be determined according to the alloy composition, and it is usually preferable to heat at a temperature 50 ° C. or more higher than the melting point of the alloy.

The molten alloy is quenched and solidified by a well-known rotating roll quenching method, splat quenching method, gas atomizing method or a combination thereof to form an amorphous alloy structure containing amorphous ribbons and amorphous coarse grains. obtain.

In the present invention, if necessary, heat melting and rapid solidification of the alloy may be continuously performed in the same apparatus.

Here, the amorphous alloy structure shows a broad peak by X-ray diffraction and is confirmed by observation with a transmission electron microscope. Depending on the quenching method or the alloy composition, 100% of the amorphous alloy structure may not be obtained, but it may be sufficient as long as the object of the present invention can be achieved.

This amorphous alloy structure has soft magnetism, and, together with its magnetic role, suppresses coarse growth of crystal grains and enables formation of a fine crystal phase in the course of crystallization heat treatment. It plays an important role in improving the hard magnetism of the entire alloy.

The heating temperature for crystallization of the obtained rapidly solidified product is generally in the range of 600 to 800 ° C. When the temperature is lower than 600 ° C., a hard magnetic crystal phase composed of a tetragonal crystal of Nd ₂ Fe ₁₄ B ₁ type does not sufficiently precipitate, so that 3.5.
A coercive force of kOe or more cannot be obtained. When the temperature exceeds 850 ° C., the coarse growth of the soft magnetic crystal phase including αFe, bccFe and a solid solution of these and M becomes remarkable, and coercive force is hardly developed. Further, the ratio of the residual soft magnetic amorphous phase is remarkably reduced, and it is difficult to exhibit rust prevention. The optimum heat treatment temperature for exhibiting good magnetic properties may be appropriately selected and set according to the alloy composition of the rapidly solidified product.

The atmosphere during the heat treatment step is not particularly limited as long as the magnetic properties of the obtained magnet alloy are not impaired.
A vacuum of ^-1 Torr or less is preferable.

If the heating time in the heat treatment step is less than 10 seconds, sufficient precipitation of the soft magnetic crystal phase and the hard magnetic crystal phase is not achieved, and if it exceeds 1 hour, the soft magnetic phase grows coarsely. A coercive force of 5 kOe or more cannot be obtained.

By the heat treatment, a crystalline phase is generated from the amorphous phase. At this time, it is important to perform heating so that the amorphous phase does not remain in an area of 10% by area or less with respect to the entire alloy structure without completely converting the amorphous phase into a crystalline phase.

As conditions for leaving the amorphous phase, it is necessary to set the conditions for the heat treatment so that the precipitation and growth of the crystal phase are not entirely achieved. In addition, since the effect of the additive element M can stabilize the amorphous phase and suppress the growth of the precipitated phase, setting an appropriate alloy composition is also important. Examples of the heat treatment method include a flash annealing method and a rapid heating and rapid cooling method, but depending on the alloy composition, a normal heat treatment method is sufficient.

The proportion of the residual amorphous phase is preferably 1 to 10 area%. When the area is less than 1% by area, the above-mentioned effects cannot be obtained, and no improvement in rust prevention performance can be expected.
If the area is 0% or more, the magnetic coupling between the amorphous phase and the crystalline phase or between the crystalline phases is weakened.

Next, the rare earth according to the present invention as described above
A method for manufacturing a bonded magnet using an iron-boron magnet alloy will be described.

The bonded magnet can be manufactured by a known method.

That is, the rare-earth-iron-boron-based magnet alloy is pulverized using a commercially available pulverizer such as a ball mill or a stamp mill, and the obtained rare-earth-iron-boron-based magnet alloy powder is converted into a resin as a binder. And kneading, kneading, injection molding the kneaded material,
It can be obtained by molding by a well-known molding method such as extrusion molding, compression molding, and calendar molding.

The average particle size of the rare-earth-iron-boron-based magnet alloy powder can be variously changed by a molding method depending on the purpose, but generally, the average particle size is preferably 150 μm or less. When a large amount of fine powder having an average particle diameter of 10 μm or less is mixed, magnetic properties are lowered. Therefore, the lower limit is about 10 μm. However, 15% by weight of the total powder
If it is less than 10 nm, fine particles of 10 nm or less may be mixed.

The mixing ratio of the rare earth-iron-boron magnet alloy powder in the bonded magnet is generally 85 to 99% by weight. The mixing ratio of the rare earth-iron-boron-based magnet alloy powder in the bonded magnet varies slightly depending on the molding method, but is generally about 88 to 93% by weight for injection molding and about 85 to 92% by weight for extrusion molding. 96 to 9 for compression molding
It is about 8.5% by weight, and about 85 to 90% by weight in calender molding.

If the amount is less than 85% by weight, the ratio of the magnet powder is too small, so that a bonded magnet having sufficient magnetic properties cannot be obtained. However, depending on the purpose, there may be applications with low magnetic properties, so that the content may be set to 85% by weight or less.
The upper limit of the mixing ratio of the magnet powder in each of the above molding methods is determined based on the requirements of the kneaded material with the moldable resin or the fluidity of the mixture and the mechanical strength of the molded product.

When manufacturing a bonded magnet, in order to facilitate molding and sufficiently bring out magnetic properties, if necessary, well-known additives such as a plasticizer, a lubricant and a coupling agent are used in addition to the resin. Is also good.

These additives may be selected appropriately according to the purpose. As the plasticizer, commercially available products corresponding to the respective resins used can be used. About 0.01 to 5.0% by weight can be used.

Examples of the lubricant include stearic acid and its derivatives, inorganic lubricants, oils and the like, and generally about 0.01 to 1.0% by weight based on the whole bonded magnet can be used.

As the coupling agent, commercially available products corresponding to the resin and filler used can be used, and generally about 0.01 to 3.0% by weight based on the resin used can be used.

When the rare earth-iron-boron-based magnet alloy according to the present invention is used as a magnetic material, the molded product becomes a bonded magnet by being magnetized by electromagnet or pulse.

The bonded magnet according to the present invention has a residual magnetic flux density Br of 6.0 kG or more, preferably 7.5 kG or more, and a coercive force iHc of 3.5 kOe or more, preferably 4.
Has a maximum energy product (BH) max of 0 kOe or more
Has 8 MGOe or more, preferably 9 MGOe or more.

The corrosion resistance is, for example, 80 ° C., 90%
In an environment of relative humidity, the elapsed time until rust accounts for 10% by area is at least 96 hours or more, preferably 120 hours or more.
More than an hour.

[0084]

First, the most important point in the present invention is that the formula R _{x
Fe 100-xyzw Co y M z} B w ( where, R represents, Nd,
One or more rare earth elements selected from Pr, Dy, Tb and Ce, and M is Ti, V, Cr, Zr, Nb,
Mo, Hf, Ta, W, Mn, Cu, Ga, Ag and S
One or more of the elements selected from i, x, y, z, and w are 5 ≦ x ≦ 10, 1.0 ≦ y ≦
9.0, 0.1 ≦ z ≦ 5, 2 ≦ w ≦ 7, and 9 ≦ (x
+ W), a soft magnetic crystal phase containing αFe, bccFe, and a solid solution thereof with M, and a Nd ₂ Fe ₁₄ B ₁ type tetragonal crystal having a composition represented by 5 <(y + z)). Each of the hard magnetic crystal phase has an alloy structure precipitated in the soft magnetic amorphous phase, and the soft magnetic amorphous phase accounts for 10 area% or less of the entire alloy structure, The balance is the soft magnetic crystal phase and the hard magnetic crystal phase, and the soft magnetic crystal phase has at least 5
The rare earth-iron-boron-based magnet alloy having 0 area% and the balance being the hard magnetic crystal phase has a high residual magnetic flux density Br of at least 10 kG and a large coercive force of at least 3.5 kOe. iHc, and as a result, the maximum energy product (BH) max is large, and it is a fact that it is excellent in rust prevention.

Regarding the reason why a rare earth-iron-boron-based permanent magnet having a large coercive force iHc can be obtained, the present inventor has shown that only the Co element is contained without including the specific M element as shown in a comparative example described later. In the case where only the specific M element is included without including the Co element, the sum total is out of the range of the specific amount even though the Co element and the specific element are included. In any case, a rare-earth-iron-boron-based permanent magnet having the properties aimed at by the present invention cannot be obtained. Therefore, the synergistic effect of the Co element and the specific M element causes Nd ₂ Fe It is thought that the effect of increasing the magnetocrystalline anisotropy of the ₁₄ B ₁ type tetragonal crystal and the effect of miniaturizing the precipitated phase were exhibited.

Regarding the reason why a rare earth-iron-boron-based permanent magnet excellent in rust resistance can be obtained, the present inventor has determined that the amorphous phase mainly plays a magnetic role in the soft magnetic crystal phase and the hard magnetic crystal phase. It is thought to be due to the fact that it exists around the periphery and that an appropriate amount is stably present.

[0087]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the present invention is as follows.

The phase structure of the alloy structure of the rare earth-iron-boron magnet alloy is as follows: a thin ribbon alloy (thickness: 20 μm) is obtained by using a high-resolution transmission electron microscope HR-TEM (manufactured by JEOL Ltd.) Observation and measurement were performed using an energy dispersive X-ray analyzer EDX (manufactured by JEOL Ltd.).

The magnetic structure of the alloy structure was confirmed to be soft magnetic by identifying an αFe type crystal and an Fe ₃ B type crystal by electron beam diffraction using the above nanobeam electron beam diffractometer.

Similarly, by identifying the Nd ₂ Fe ₁₄ B ₁ type crystal, it was confirmed that it was hard magnetic.

The area% means a transmission electron microscope (TEM)
And the like in observations in two-dimensional visual fields.

The alloy composition was shown by a value measured by chemical analysis.

The magnetic properties of the alloy were measured using a sample vibration magnetometer VS.
M (manufactured by Riken Denshi Co., Ltd.).

The magnetic properties of the bonded magnet were shown by values measured by a BH curve tracer (manufactured by Toei Kogyo Co., Ltd.) after applying a pulse magnetization of about 50 kOe in advance.

[0095] The rust-preventing performance of the alloy ribbon was determined in accordance with JIS Z 23
The salt spray test method based on No. 71 was used. That is, it is taken out at regular time intervals, and the presence or absence of rusting, and the increase and enlargement of the rusting point are observed with a 50-fold optical microscope.
The elapsed time until occupying the area% was shown.

The corrosion resistance of the bonded magnet was evaluated based on how many hours rust occurs in an environment of 80 ° C. and 90% relative humidity, or how the rust point increases or expands on the observation surface. Quantitatively, it was shown by the elapsed time until rust occupies 10 area% in the optical microscope visual field of 50 times.

Nd ₇ Fe _83.5 Co ₄ Nb ₁ Ga in atomic ratio
As a composition of _0.5 B _4, metal neodymium piece (purity 99.9%) (manufactured by Nippon Yttrium) 5.08
g, metallic iron pieces (electrolytic iron, purity 99.9%) (manufactured by Showa Denko KK) 23.02 g, metallic cobalt pieces (purity 99.9%).
9%, manufactured by Sumitomo Metal Mining Co., Ltd.) 1.164 g, metal niobium piece 0.458 g, metal gallium piece 0.172 g
And 0.214 g of crystal boron pieces were weighed to a total weight of 30 gr. These were arc-melted in a reduced pressure atmosphere of argon gas to produce alloy buttons. The arc melting was performed a total of four times by turning the front and back of the alloy button upside down for homogenization.

This alloy button was made into a small piece, and a quartz nozzle (tube diameter: 10 mm, length: 20 cm, nozzle diameter: 0.4 m)
m), and set in a liquid quenching device. After high-frequency melting under a reduced pressure atmosphere of argon gas to form a molten metal, while blowing a pressurized argon gas into the nozzle, a peripheral speed of
The molten metal is jetted onto a copper roll (diameter 20 cm) rotating at m / sec, rapidly solidified, and has a width of 1-2 mm and a thickness of 10-2.
A 0 μm ultra-quenched alloy ribbon was produced.

As a result of X-ray diffraction, the obtained alloy ribbon showed a broad peak as a whole. When the results of the X-ray diffraction and the results of the observation with a high-resolution transmission electron microscope were interpreted together, it was confirmed that at least the majority consisted of an amorphous phase. Also, as a result of measuring the constituent element ratio of this alloy ribbon by chemical analysis, it was found that Nd ₇ Fe _83.5 Co ₄ Nb
₁ Ga _0.5 B ₄ , which was confirmed to be approximately equal to the charged composition ratio.

The alloy ribbon was sealed in a quartz tube under a vacuum of 5 × 10 ⁻² Torr, and was heated at 750 ° C. for 3 minutes. As a result of X-ray diffraction, a clear peak based on two types of crystal structures, αFe type and Nd ₂ Fe ₁₄ B ₁ type, and a low peak thought to be Fe ₃ B type were detected in the heat-treated alloy ribbon. . Since the background had a broad and gentle peak, it was inferred that some amorphous phase also remained.

The fine structure of the heat-treated alloy ribbon was observed using a high-resolution transmission electron microscope, a nanobeam electron beam diffractometer, and an energy dispersive X-ray analyzer. As a result, the alloy structure is such that the soft magnetic crystal phase containing αFe is about 65% by area with respect to the total crystal phase (of the soft magnetic crystal phase, the soft magnetic crystal phase including Fe ₃ B type inevitably precipitated The hard magnetic crystal phase containing Nd ₂ Fe ₁₄ B ₁ accounts for about 28 area% of the total crystal phase, and The total sum was 91 area% with respect to the entire crystal structure, assuming that the entire two-dimensional visual field was 100 area%. Therefore, the remaining 9 area% was a soft magnetic amorphous phase.

The crystal grain size of the soft magnetic crystal phase containing αFe or bcc type Fe alloy is in the range of 20 to 45 nm, and the crystal grain size of the soft magnetic crystal phase containing Fe ₃ B type is 15 to 45 nm.
The hard magnetic crystal phase including the Nd ₂ Fe ₁₄ B ₁ type has a crystal grain size of 15 to 40 nm, and the respective phases are dispersed and precipitated by the heat treatment from the amorphous phase before the heat treatment. And crystallization was observed. Further, the analysis results confirmed that each element of Nd and B was enriched in the remaining amorphous phase, and they were 11.3 atomic% and 7.8 atomic%, respectively.

The magnetic properties at room temperature of the alloy ribbon after the heat treatment were measured with a sample vibrating magnetometer. As a result, the coercive force iHc was 3.
7 kOe, residual magnetic flux density Br was 11.2 kG, and maximum energy product (BH) max was 17.4 MGOe.

Further, in order to examine the rust prevention performance of the rare earth-iron-boron based magnet alloy, the alloy was taken out every 12 hours and the area ratio of red rust on the surface of the ribbon was observed with an optical microscope.
As a result, the elapsed time until rust accounted for 10% by area was 72 hours later, and thus it was found that the present alloy was also excellent in corrosion resistance.

The heat-treated alloy ribbon thus obtained was pulverized with a vibrating ball mill and sieved to obtain alloy magnetic powder having a particle size of 150 μm or less and 20 μm or more.

98 g of this alloy magnetic powder and epoxy resin XW-
2214 (trade name, manufactured by Nippon Pernox Co., Ltd.) 2 g
Is melted with an appropriate amount of methyl ethyl ketone and the alloy magnetic powder is mixed well, and then the methyl ethyl ketone is dried and vaporized to obtain a mixture for compression molding (alloy magnetic powder 98% by weight, epoxy resin 2
% By weight. ).

3.3 g of this mixture was placed in a cylindrical sample press jig having a diameter of 10 mm, and pressed at a pressure of about 7 ton / cm ² to obtain a cylindrical green compact having a diameter of 10 mm and a length of about 7 mm.

The green compact was heated at 150 ° C. for 1 hour to cure the epoxy resin, thereby obtaining a compression-molded bonded magnet having a density of 6.0 g / cm ³ .

After magnetizing the compression molded bond magnet with a pulse magnetizer at about 50 kOe, the magnet properties at room temperature were measured with a BH tracer. As a result, the residual magnetic flux density Br was 9.
0 kG, coercive force iHc was 4.6 kOe, and maximum energy product (BH) max was 10.2 MGOe.

Further, regarding this bonded magnet, the aforementioned 8
A corrosion resistance test was performed at 0 ° C. and 90% relative humidity, and the occurrence of rust over time was observed. As a result, as a result of an optical microscope (50 times) every 12 hours, rusting of several points of 0.1 mm maximum was observed in the visual field only after 72 hours. In the same visual field, observation was continued every 12 hours. As a result, even after 168 hours had passed, rust occupied only 10% by area in the visual field, indicating that the bonded magnet had excellent corrosion resistance.

[0111]

Next, examples and comparative examples will be described.

Examples 1 to 18 and Comparative Examples 1 to 9 The heat-treated alloy ribbon was produced in the same manner as in the embodiment of the invention except that the alloy composition and the heat treatment temperature in the alloy ribbon production process were variously changed. I got

The phase structure of the alloy structure of the heat-treated alloy ribbons obtained in Examples 1 to 18 was observed in the same manner as in the embodiment of the present invention.

As a result, the soft magnetic crystal phase containing αFe accounts for 60 to 75 area% of the total crystal phase (of the soft magnetic crystal phase,
The soft magnetic crystal phase including Fe ₃ B type that inevitably precipitates
The ratio was equivalent to about 7 area% with respect to the entire crystal phase. ), Wherein the hard magnetic crystal phase containing Nd ₂ Fe ₁₄ B ₁ is in a range of less than 40% by area and 25% by area or more with respect to the total crystal phase. Assuming that the whole is 100 area%, 90 to 9 with respect to the whole crystal structure
It was in the range of 5 area%. Therefore, the soft magnetic amorphous phase
It was in the range of 5 to 10 area%.

The crystal grain size of the soft magnetic crystal phase containing αFe and bcc type Fe alloy is in the range of 15 to 50 nm, and the crystal grain size of the soft magnetic crystal phase containing Fe ₃ B type is 15 nm.
And the crystal grain size of the hard magnetic crystal phase including the Nd ₂ Fe ₁₄ B ₁ type is in the range of 15 to 50 nm. It was observed that it had crystallized. Further, it was confirmed from the analysis results that the rare-earth element and the respective elements of B were concentrated in the residual amorphous phase, respectively, in the range of 10 to 15 at% and in the range of 7 to 9 at%.

Comparative Examples 1 and 3 are alloys containing no Co element and M element, Comparative Examples 2 and 4 are alloys containing no M element, and Comparative Examples 5 and 6 contain only specific M element without containing Co element. Comparative Example 7 is an alloy in which the sum of the amount of Co and M is 5 or less, and Comparative Examples 8 and 9 are F containing a large amount of the B element.
e ₃ B-based exchange spring magnet alloy.

The alloy structures and microstructures in Comparative Examples 1 to 4 are substantially the same as those of the present invention, and Comparative Examples 8 and 9
It was confirmed that the e ₃ B-type soft magnetic crystal phase occupies 60% by area or more, and that there is substantially no residual amorphous phase.

Table 1 shows the main manufacturing conditions and various characteristics at this time.

[0119]

[Table 1]

From the above results, it can be seen that the alloy according to the present invention is superior in magnetic properties and rust prevention performance as compared with the comparative example.

Examples 19 to 24 and Comparative Examples 10 to 13 Bonded magnets were obtained in the same manner as in the embodiment of the present invention, except that the type of the magnet alloy powder was variously changed.

Table 2 shows the main manufacturing conditions and various characteristics at this time.

[0123]

[Table 2]

The bonded magnet of the present invention is different from the comparative example in that
It can be seen that the magnetic properties and corrosion resistance are excellent.

[0125]

The rare earth-iron-boron permanent magnet alloy according to the present invention has a high residual magnetic flux density Br and a large coercive force iH.
c, so that the maximum energy product (BH) max
It is preferable as a material for a high-performance bonded magnet because of its high rust resistance and excellent rust resistance.

Since the rare earth-iron-boron permanent magnet alloy according to the present invention has a rare earth content of less than 10 atomic%, it can be obtained economically and industrially advantageously.

Further, the bonded magnet obtained by using the rare earth-iron-boron permanent magnet alloy according to the present invention has high properties due to the rare earth-iron-boron permanent magnet alloy having the above-mentioned various properties. It has a residual magnetic flux density Br and a large coercive force iHc, and as a result, the maximum energy product (BH) m
Because of high ax and excellent corrosion resistance, it is preferable as a high performance bonded magnet.

Claims (4)

[Claims] 1. The formula R _x Fe _100-xyzw Co _y M _z B _w
(However, R is one or more rare earth elements selected from Nd, Pr, Dy, Tb and Ce, M is Ti,
V, Cr, Zr, Nb, Mo, Hf, Ta, W, Mn,
One, two or more elements selected from Cu, Ga, Ag and Si, x, y, z and w each have an atomic ratio of 5 ≦
x ≦ 10, 1.0 ≦ y ≦ 9.0, 0.1 ≦ z ≦ 5, 2 ≦
a soft magnetic crystal phase having a composition represented by w ≦ 7 and 9 ≦ (x + w), 5 <(y + z)), and containing αFe, bccFe, and a solid solution of these and M with Nd ₂ F
Each of the hard magnetic crystal phase composed of e ₁₄ B ₁ type tetragonal crystal has an alloy structure precipitated in the soft magnetic amorphous phase, and the soft magnetic amorphous phase 10 for the organization
% Or less, the balance being the soft magnetic crystal phase and the hard magnetic crystal phase, and the soft magnetic crystal phase being at least 50 area% of the total crystal structure, and the balance being the hard magnetic crystal phase. A rare earth-iron-boron-based magnet alloy which is a phase. 2. The rare earth-iron-boron magnet alloy according to claim 1, wherein the coercive force iHc is 3.5 kOe or more, the residual magnetic flux density Br is 10 kG or more, and the maximum magnetic energy product (BH) max is 13 MGOe or more. Wherein formula _{R x Fe 100-xyzw Co y} M z B w
(However, R is one or more rare earth elements selected from Nd, Pr, Dy, Tb and Ce, M is Ti,
V, Cr, Zr, Nb, Mo, Hf, Ta, W, Mn,
One, two or more elements selected from Cu, Ga, Ag and Si, x, y, z and w each have an atomic ratio of 5 ≦
x ≦ 10, 1.0 ≦ y ≦ 9.0, 0.1 ≦ z ≦ 5, 2 ≦
An alloy produced so as to have a composition ratio represented by w ≦ 7 and 9 ≦ (x + w), 5 <(y + z)) is heated and melted to form a molten metal, then rapidly solidified, and then rapidly solidified. The method for producing a rare-earth-iron-boron-based magnet alloy according to claim 1, wherein the material is heat-treated in a temperature range of 600 to 850C. 4. A bonded magnet obtained by pulverizing the rare earth-iron-boron magnet alloy according to claim 1 using a resin as a binder, wherein the magnet alloy powder is A bonded magnet, which is mixed and blended at a ratio of 85 to 99% by weight.