JPH08330118A - Manufacture of r-fe-b-c permanent magnet material with excellent corrosion resistance - Google Patents

Abstract

PURPOSE: To provide a magnet having excellent orientation and corrosion resistance by forming R-Fe-B-C molten alloy containing specific composition in a cast piece having a specific plate thickness by strip casting, adding specific lubricant to the alloy powder roughly crushed from the piece, and magnetizing the comminuted fine powder. CONSTITUTION: After a molten alloy containing 10-30at% of R (R is at least one of rare earth elements including Y) 4 to 15at% of B + C (B of 2at% or less) and the residue of Fe (the part of the Fe may be substituted for one or more of Co and Ni) is cast in a cast piece of a thin plate having a plate thickness of 0.03 to 10mm and composition finely separated in R-rich phase to 10μm or less by a strip casting method, 0.02 to 5.0wt.% of liquid-like or solid-like lubricant is added to be mixed with roughly crushed powder having a mean particle size of 10 to 500μm phase comminuted from the piece, finely comminuted, the fine powder having mean particle size of 1 to 10μm is filled in a mold up to filling density of 1.4 to 3.5g/cm<3> , oriented by a pulse magnetic field of 10kOe or more, then molded, sintered and aged.

Description

Detailed Description of the Invention

[0001]

The present invention relates to R (provided that R contains at least one rare earth element including Y), Fe,
A method for producing a raw material powder for permanent magnets containing B and C as a main component. A molten alloy containing R, Fe, B and C as a main component is specified by a strip casting method such as a single roll method or a twin roll method. A slab having a homogeneous structure in which a thick R-rich phase is finely separated is obtained, coarsely pulverized, added with a lubricant, and finely pulverized to enable efficient fine pulverization. R has excellent corrosion resistance and orientation, and has excellent magnetic properties by being subjected to a pulsed magnetic field for orientation, and then being molded and sintered.
The present invention relates to a manufacturing method for obtaining a -Fe-B-C based permanent magnet material.

[0002]

2. Description of the Related Art Today, R is a typical high-performance permanent magnet.
-Fe-B system permanent magnet (JP-A-59-46008)
Has high magnet characteristics due to the structure of the ternary tetragonal compound having the main phase and the R-rich phase, and is used in a wide range of fields from various household electrical appliances to large computer peripherals, depending on the application. R-Fe-B-C permanent magnets having various compositions have been proposed so as to exhibit various magnet characteristics.

The R-Fe-B system permanent magnet has extremely excellent magnetic properties, but has problems in corrosion resistance and temperature characteristics. A method of coating the surface of the magnet with a corrosion resistant metal film or a resin film has been proposed (JP-A-60-54406 and JP-A-60-63901), and in order to improve the temperature characteristics of the magnetic characteristics of the magnet, the magnet has been proposed. Various compositions have been studied by substituting Co for a part of Fe in JP-A No. 59-6.
No. 4733), it was not enough.

Recently, a part of B of the R-Fe-B system magnet is replaced with C
R-Fe-, which has excellent corrosion resistance and has improved temperature characteristics, by forming a grain boundary phase having excellent corrosion resistance by substitution with
A B-C system magnet has been proposed (JP-A-3-82744). The R-Fe-B-C magnet is obtained by casting a molten alloy into a mold to prepare an ingot, and then magnetizing the ingot by a powder metallurgy method of crushing, molding, sintering and aging, or After solution treatment of ingot or coarse powder after crushing ingot,
It is pulverized and magnetized by the powder metallurgy method to improve the corrosion resistance and temperature characteristics.

[0005]

However, the R-F
There is a strong demand for cost reduction for the e-B permanent magnet material, and it has become extremely important to efficiently produce the raw material powder for high-performance permanent magnets. Further, it is necessary to improve the manufacturing conditions to bring out the characteristics that are close to the limit. Furthermore, today's electric and electronic devices are becoming smaller and lighter, and (B
H) There is a strong demand for higher functionality than max 40 MGOe,
There is a demand for higher performance and cost reduction of R-Fe-B based permanent magnets.

The main phase of the R-Fe-B-C type magnet in which a part of B of the R-Fe-B type magnet is replaced by C is replaced by C of 1 part of B of the R ₂ Fe ₁₄ B tetragonal compound. R ₂ Fe ₁₄ (B
It becomes a _1-x C _x ) tetragonal compound and the crystal structure does not change.
To increase the residual magnetic flux density of the R-Fe-B-C sintered magnet (Br) is 1) a ferromagnetic phase, the main phase R ₂ Fe
₁₄ Increasing the content of the (B _1-x C _x ) phase 2) Increasing the density of the sintered body to the theoretical density of the main phase 3) Furthermore, the degree of orientation of the main phase crystal grains in the easy axis direction of magnetization Is required to increase.

That is, in order to achieve the above item 1),
It is important to bring the composition of the magnet close to the stoichiometric composition of the above R ₂ Fe ₁₄ (B _1-x C _x ). As R-
If an attempt is made to produce a Fe-B-C based sintered magnet, pulverization becomes difficult especially during fine pulverization because α-Fe crystallized in the alloy lump and the R-rich phase are locally distributed. ,
There was a problem such as composition deviation.

More specifically, in the case of the conventional ingot crushing method in which a mold is cast, since the α-Fe is present, the crushing efficiency at the time of fine crushing is poor, and the particle size distribution of the powder after fine crushing is broad. Since the R-rich phase is locally ubiquitous, the crystal structure of the sintered magnet becomes coarse, and high magnet characteristics cannot be obtained. Therefore, the alloy lump or the coarse powder obtained by crushing the alloy is homogenized, and solution treatment is performed in order to eliminate α-Fe. However, this not only leads to an increase in cost, but also coarsens the main phase crystal grains and segregates the R-rich phase. However, it is difficult to improve the magnet characteristics of the sintered magnet.

The present invention enables efficient pulverization,
In addition, the corrosion resistance is excellent, and high iHc is expressed by making the crystal grains of the magnet finer, and the degree of orientation of each crystal grain in the easy magnetization direction is increased to obtain a high (BH) max value. Excellent corrosion resistance and high performance. An object is to provide a method for producing an R-Fe-B-C based permanent magnet material.

[0010]

The inventors of the present invention firstly investigated the R-F.
Using an e-B-C type alloy as a starting material, the fine grinding efficiency is improved, the corrosion resistance is excellent, and the magnetic characteristics of the sintered magnet, especially i
As a result of various studies on the crushing method for the purpose of improving Hc, the R-Fe-B-C alloy having a fine and uniform structure obtained by the strip casting method was roughly crushed, and then the coarsely crushed alloy powder was lubricated with a lubricant. When added and compounded and finely pulverized, the finely pulverizing ability is improved to about twice as much as that of the conventional one, and the fine powder is oriented by applying a pulse magnetic field, then shaped and sintered to obtain a sintered magnet. (BH) max and i of the magnetic properties of
It was found that Hc is further improved.

That is, an R-Fe-B-C type alloy having a specific composition having a structure in which the R-rich phase having a specific plate thickness finely separated by strip casting is roughly pulverized, and then a lubricant is added to the coarsely pulverized powder. By finely pulverizing it, it is possible to subdivide the crystal grains of the main phase constituting the alloy ingot, and it is possible to produce a powder having a uniform grain size distribution and excellent fluidity. As a coarse crushing method, a H ₂ storage-disintegration method is preferable, and when H _{2 is} stored in an R-Fe-B-C based alloy having a structure in which an R-rich phase is finely separated,
It was found that the R-rich phase finely dispersed produces a hydride and expands in volume, whereby the alloy can be spontaneously collapsed.

At this time, in particular, it is important that the R-rich phase is finely dispersed and the R ₂ Fe ₁₄ (B _1-x C _x ) phase is fine. However, in the method of smelting an alloy ingot by using an ordinary template, when the alloy composition is brought close to the stoichiometric composition of R ₂ Fe ₁₄ (B _1-x C _x ), crystallization of Fe primary crystal occurs. It is unavoidable and becomes a factor that greatly reduces the fine pulverization ability in the next step. Therefore, heat treatment is applied for the purpose of homogenizing the alloy ingot, and a means for eliminating α-Fe is taken,
This leads to an increase in cost, coarsening of the main phase crystal grains, and segregation of the R-rich phase, which makes it difficult to improve the magnetic characteristics of the sintered magnet.

Further, it is also an essential condition for attaining a high Br that the magnetization easy axis directions of the main phase crystal grains are aligned, that is, the degree of orientation is increased. Therefore, the permanent magnet material manufactured by the powder metallurgy method is used. , For example, hard ferrite magnets,
The Sm-Co magnet and the R-Fe-B magnet employ a method of pressing the powder in a magnetic field. However, when considering the coil and the power source of the magnetic field generation source arranged in a usual press device (hydraulic press, mechanical press) for generating a magnetic field for the purpose of increasing the degree of orientation, a magnetic field of 10 kOe to 20 kOe at most is examined. However, in order to generate a higher magnetic field, it is necessary to increase the number of turns of the coil, and also to increase the size of the device that requires a high power supply.

The present inventors analyzed the relationship between the magnetic field strength during pressing and Br of the sintered body, and the higher the magnetic field strength, the higher the Br, and the momentary strong magnetic field is generated. It was found that the Br value can be further increased by using a pulsed magnetic field capable of achieving this.

Furthermore, as a result of further studying the improvement of the filling property into the mold and the improvement of the orientation for the purpose of improving the performance of the magnet, it was obtained from strip cast ribbon which has been H ₂ occluded and de H ₂ treated. Filling into the mold by adding a solid lubricant or liquid lubricant to the coarsely crushed powder, pulverizing with a jet mill in an inert gas stream, and pulverizing to an average particle size of 1 to 5 μm. It has been found that a fine powder having excellent magnetic properties and magnetic orientation can be obtained. Furthermore, when this fine powder is used to instantaneously orient in a pulsed magnetic field, Br can be made even higher, and the powder can be kept cold and stable. High-performance R-Fe-B-C with excellent corrosion resistance and excellent magnetic properties by being formed by hydraulic pressing or by press forming in a magnetic field by combining a pulse magnetic field and a static magnetic field by an electromagnet.
Finding that it is possible to obtain a permanent magnet material
Completed this invention.

That is, according to the present invention, R (provided that R is at least one of rare earth elements including Y) is 10 at% to
30at%, B + C = 4 to 15at%, but B2at%
Hereinafter, the remaining molten Fe (however, a part of Fe can be replaced with one or two of Co and Ni) and the unavoidable impurities were melted by the strip casting method to a plate thickness of 0.
A thin lubricant of 03 mm to 10 mm, cast into a slab having an R-rich phase finely separated structure of 10 μm or less, and then coarsely crushed the slab to obtain a coarsely pulverized powder having an average particle size of 10 to 500 μm and a liquid lubricant. Or 0.02-5.0 wt% solid lubricant
% Added and mixed and finely pulverized to obtain an average particle size of 1 to 10 μm.
Filling density of fine powder of m in the mold is 1.4 to 3.5 g /
cm ³ filling, momentarily applying a pulsed magnetic field of 10 kOe or more to orient, and then forming, sintering, and aging treatment, R-Fe-B-C based permanent magnet material having excellent corrosion resistance. Is a manufacturing method.

Further, the present invention is characterized in that, in the constitution of the method for producing the R-Fe-B-C permanent magnet material having excellent corrosion resistance, the coarsely pulverized powder is obtained by the H ₂ storage and collapse method. At least one fatty acid ester dissolved in a solvent is used as a liquid lubricant, and at least solid zinc lubricant such as zinc stearate, copper stearate, aluminum stearate, and ethylene vinylniamide is used. One type is used, the pulsed magnetic fields to be applied are characterized in that the magnetic field directions are applied in the same direction, and the pulsed magnetic field to be applied is characterized in that the magnetic field directions are repeatedly inverted and applied. Each manufacturing method is also proposed.

Regarding the magnetic characteristics of the R-Fe-B-C permanent magnet according to the present invention, the required magnetic characteristics can be obtained by appropriately selecting the composition, manufacturing conditions and the like. The details will be described below. The cast slab of the magnetic material having the structure in which the R-rich phase of the specific composition is finely separated according to the present invention is manufactured by the alloy casting of the specific composition by the strip casting method by the single roll method or the twin roll method. The obtained slab is a thin plate material having a plate thickness of 0.03 mm to 10 mm, and the single roll method and the twin roll method are used properly depending on the desired slab plate thickness, but when the plate thickness is thick, the twin roll method is used. Further, when the plate thickness is thin, it is preferable to adopt the single roll method.

The reason for limiting the plate thickness of the cast slab to 0.03 mm to 10 mm is that if it is less than 0.03 mm, the quenching effect becomes large, the crystal grain size becomes smaller than 3 μm, and it is easily oxidized when pulverized. It is not preferable because it causes deterioration of magnetic properties, and when it exceeds 10 mm, the cooling rate becomes slow, α-Fe is easily crystallized, and the crystal grain size becomes large.
This is because the Nd-rich phase is unevenly distributed, which deteriorates the magnetic characteristics, which is not preferable.

The cross-sectional structure of the R-Fe-BC alloy having a specific composition obtained by the strip casting method of the present invention has a main phase R ₂ Fe ₁₄ (B _1-x C _x ) crystal as a conventional template. Compared to that of the ingot obtained by casting, it is about 1/10 or less finer, for example, the dimension in the minor axis direction is 0.1
μm to 50 μm, the long axis direction is 5 μm to 200 μm, and the R-rich phase is finely dispersed so as to surround the main phase crystal grains, and even in a locally unevenly distributed region, The size is 20 μm or less.

By finely separating the R-rich phase to 10 μm or less, volume expansion when the R-rich phase forms a hydride during the H ₂ occlusion treatment is uniformly generated and finely divided, and thus finely pulverized. As a result, the crystal grains of the main phase are subdivided to obtain fine powder having a uniform particle size distribution. The slab remains H
_Although it may be subjected to H ₂ occlusion treatment, it is preferable to break it to a required size to expose the metal surface and perform H ₂ occlusion treatment.

For H ₂ occlusion treatment, for example, a slab of 0.03 mm to 10 mm thickness, which is broken to a predetermined size, is inserted into a raw material case, and the raw material case is placed in a container which can be closed by closing a lid. Then, the inside of the container is sufficiently evacuated, and then H ₂ gas having a pressure of 200 Torr to 50 kg / cm ² is supplied to occlude H ₂ in the slab. This H
_{(2) Since the} occlusion reaction is an exothermic reaction, a cooling pipe for supplying cooling water is provided around the outer periphery of the container to prevent the temperature inside the container from rising and to supply H ₂ gas at a predetermined pressure for a certain period of time. As a result, H ₂ gas is absorbed, and the slab is spontaneously disintegrated and pulverized. Further, after cooling the powdered alloy, it is subjected to H ₂ degassing treatment in vacuum. Since the alloy powder of the above treatment has fine cracks in the grains, it can be finely pulverized in a short time by a ball mill, a jet mill or the like to obtain an alloy powder having a required grain size of 1 μm to 10 μm.

In the present invention, the inside of the processing container may be previously replaced with air by an inert gas, and then the inert gas may be replaced by H ₂ gas. Also, the smaller the fracture size of the slab, the smaller the H ₂ crushing pressure can be made, and the H ₂ gas pressure is such that the fractured slab absorbs H ₂ and is pulverized even under reduced pressure. The higher the atmospheric pressure, the more likely it is to be pulverized. However, since it is less than 200Torr powdering becomes poor, although preferred in view of powdering by H ₂ absorption exceeds 50 kg / cm ^2, not desirable from the safety of the device and work, H ₂ gas pressure 200Torr~ 50 kg / c
m ² 2 kg / cm ^{2 to} 10 kg /
cm ² is preferred. In the present invention, the processing time for pulverization by H ₂ occlusion varies depending on the size of the closed container, the size of the fragments, and the H ₂ gas pressure, but it is required to be 5 minutes or more.

After cooling the alloy powder pulverized by H ₂ occlusion, primary H ₂ degassing treatment is performed in vacuum. Further, the powdered alloy is heated to 100 ° C. in vacuum or argon gas.
When heated to ~ 750 ° C and subjected to secondary H ₂ gas treatment for 0.5 hour or more, it is possible to prevent oxidation of the powder or press-molded product due to long-term storage and prevent deterioration of magnetic properties of the obtained permanent magnet. . Since the dehydrogenation treatment of heating to 100 ° C. or higher according to the present invention has an excellent dehydrogenation effect, the above primary dehydrogenation treatment in vacuum is omitted, and the disintegrated powder is directly vacuumed at 100 ° C. or higher. You may perform a dehydrogenation process inside or in an argon gas atmosphere.

[0025] That is, after H ₂ absorption and disintegration reaction vessel for H ₂ occlusion reaction described above, performs the dehydrogenation process subsequently resulting collapse powder is heated to above 100 ° C. in an atmosphere of the same container be able to. Alternatively, after dehydrogenation treatment in a vacuum, the dehydrogenation treatment of the present invention may be carried out in which the disintegrated powder is taken out from the treatment container, finely crushed and then heated to 100 ° C. or higher in the treatment container.

The heating temperature in the above dehydrogenation treatment is 1
If the temperature is lower than 00 ° C, it takes a long time to remove H ₂ remaining in the disintegrated alloy powder, which is not mass-productive. Further, at a temperature of higher than 750 ° C., a liquid phase appears and the powder is solidified, which makes fine pulverization difficult and deteriorates the formability at the time of pressing. Therefore, it is preferable in the case of producing a sintered magnet. Absent.
Further, considering the sinterability of the sintered magnet, the preferable dehydrogenation treatment temperature is 200 ° C to 600 ° C. Further, the treatment time varies depending on the treatment amount, but 0.5 hours or more is required.

A feature of the present invention is that 0.02 to 0.02 of a liquid lubricant or a solid lubricant is added to coarsely pulverized powder having an average particle size of 10 μm to 500 μm obtained by the H ₂ storage-disintegration method.
After adding and mixing 5 wt%, it is to be jet-milled in an inert gas stream to obtain fine powder having an average particle diameter of 1 to 10 μm. As the liquid lubricant in the present invention, a saturated or unsaturated fatty acid ester and a boric acid ester as an acid salt can be used, and they are dispersed in a petroleum solvent or an alcohol solvent. The amount of fatty acid ester in the liquid oil lubricant is preferably 5% by weight to 50% by weight.

The saturated fatty acid ester is an ester represented by the general formula RCOOR 'R = C _n H _{2n + 2} (alkane), and the unsaturated fatty acid ester is a general formula R = C _n H _2n (alkene) RCOOR ′ Or R = C _n H _2n-2 (alkyne).

The solid lubricant is at least one of zinc stearate, copper stearate, aluminum stearate, ethylene vinylamide and the like, and when the average particle size of the solid lubricant is less than 1 μm, it is industrially produced. If it exceeds 50 μm, it is difficult to uniformly mix it with the coarsely pulverized powder, so that the average particle size is 1 μm.
˜50 μm is preferred.

In the present invention, if the addition amount of the liquid lubricant or the solid lubricant is less than 0.02 wt%, the powder particles are not uniformly coated and the mold filling property and the crystal orientation property are improved and improved. If it exceeds 5% by weight, the non-volatile residue in the lubricant remains in the sintered body, resulting in a decrease in the sintered density and deterioration of the magnetic properties, which is not preferable. The amount is set to 0.02 wt% to 5 wt%.

In the present invention, the reason why the average particle size of the coarsely crushed powder is limited is that it is difficult to safely handle the raw material powder in the air when the average particle size is less than 10 μm, and the magnetic properties are deteriorated by the oxidation of the raw material powder. Is not preferable, and when it exceeds 500 μm, it becomes difficult to supply the raw material powder to the jet mill crusher, and the pulverization efficiency is remarkably lowered.
It is set to 500 μm.

Next, for fine pulverization, an inert gas (for example, N 2
_2. Fine pulverize with a jet mill using Ar). Of course, it is also possible to use a ball mill using an organic solvent (for example, benzene, toluene, etc.) or attritor grinding.

Further, if the average particle size of the finely pulverized powder according to the present invention is less than 1 μm, the powder becomes extremely active and there is a risk of ignition in steps such as press molding, which is not preferable because the magnetic properties are deteriorated and 10 μm. If it exceeds, the crystal grains of the permanent magnet obtained by sintering become large, the magnetization reversal easily occurs, and the coercive force is lowered, which is not preferable. Therefore, the average grain size is set to 1 μm to 10 μm. A preferable average particle size is 2.5 μm to 4 μm.

The following method is proposed for molding using a pulsed magnetic field. The finely pulverized powder is filled in a mold in an inert gas atmosphere. The mold may be made of non-magnetic metal, oxide, ceramics or the like, or may be an organic compound such as plastic or rubber. The packing density of the powder is
Resting bulk density of the powder (packing density 1.4 g / cm
³ ), the bulk density after tapping (filling density 3.5 g /
The range of cm ³ ) is preferred. Therefore, the packing density is 1.4 ~
Limited to 3.5 g / cm ³ .

To the finely pulverized powder filled in the mold, a pulsed magnetic field from an air-core coil or a condenser power source is applied to orient the powder. At the time of orientation, the pulsed magnetic field is applied while compressing using the upper and lower punches. carry out. The higher the strength of the pulse magnetic field, the better, and at least 10 kOe or more is required. Preferred pulse magnetic field strength is 20 kOe
~ 60 kOe. In order to continuously perform the orientation and the pressing by the pulsed magnetic field, a coil for generating the pulsed magnetic field is embedded in the die, the orientation is performed by using the pulsed magnetic field, and then the ordinary magnetic field pressing method is used for molding. Is possible.

The pulsed magnetic field can be applied only once or repeatedly. When repeatedly applied, the magnetic field direction is not only the required direction, but it is possible to further improve the orientation by alternately inverting and applying the magnetic field direction. Furthermore, in addition to repeatedly applying the same magnetic field strength, The magnetic field strength can be gradually reduced and applied, and when the magnetic field direction is alternately inverted and applied, the strength can be gradually reduced to apparently deplete the molded body. Has the advantage of being easier. Pulse magnetic field time is 1 μsec to 1
0 sec is preferable, and further 5 μsec to 100 ms
ec is preferable, and the pulse magnetic field is applied 1 to 10 times,
Furthermore, it is preferably 1 to 5 times.

When applying a magnetic field, it is necessary to appropriately select the above-mentioned application method, number of times of application, pulse magnetic field strength, and application time, taking into consideration the degree of improvement in the desired orientation. For example, in the manufacturing method according to the present invention, when the applied pulse magnetic field is once, the maximum energy product (B
H) High-performance R-F with max value of 40 MGOe or more
It is possible to obtain an e-B-C system permanent magnet material, and the characteristic value is 44 MGOe or more when alternately reversing a plurality of times, and the characteristic value is alternately reversing a plurality of times when the magnetic field strength gradually decreases. Is a high-performance R that shows a value of 42 MGOe or more
It is possible to obtain a —Fe—B—C based permanent magnet material.

Further, it is most preferable that the powder after the orientation is molded by compression molding with a cold isostatic press. At this time, it is necessary to appropriately select the hardness and thickness of the plastic mold, and it is necessary to select various types. It is possible to manufacture large magnet materials including shaped products. The hydrostatic pressing conditions are as follows.
A pressing force of 0 ton / cm ^{2 to} 3.0 ton / cm ² is preferable, and the hardness of the mold is preferably Hs = 20 to 80.
In that case, the magnetic field strength of the static magnetic field is preferably 5 to 20 kOe. Further, the hydrostatic pressing can also be performed in a static magnetic field. For example, at the time of orientation, after repeatedly applying the magnetic field with the same magnetic field strength, the powder after orientation is subjected to hydrostatic pressing in a static magnetic field. , The characteristic value is 46 MGOe
It is possible to obtain a high performance R-Fe-B-C based permanent magnet material exhibiting the above values.

In the present invention, any known powder metallurgical means can be used for conditions and methods such as molding, sintering and heat treatment. An example of preferable conditions is shown below. Before sintering, a general method of heating in a vacuum or a temperature increase of 100 to 200 ° C./hour in flowing hydrogen to 300 to 600
It is preferable to perform the binder removal treatment by a method of holding at 1 ° C for about 1 to 2 hours. Almost all carbon in the binder is decarburized by applying the debinding process,
It leads to improvement of magnetic properties. Since the alloy powder containing the R element easily absorbs hydrogen, it is preferable to perform the dehydrogenation treatment step after the debinding treatment in flowing hydrogen. In the dehydrogenation process, the temperature rising rate in vacuum is 50 to 200.
The stored hydrogen is almost completely removed by increasing the temperature at a temperature of 500 ° C./hour and maintaining the temperature at 500 to 900 ° C. for about 1 to 2 hours.

Further, after the dehydrogenation treatment, it is preferable to carry out sintering by raising the temperature and heating, and the temperature raising rate after the temperature exceeds 500 ° C. may be arbitrarily selected, for example, from 100 to
A well-known temperature rising method that is taken during sintering, such as 300 ° C./hour, can be adopted. The sintering of the molded product after the orientation and the heat treatment condition after the sintering are appropriately selected according to the selected alloy composition.
Sintering process of holding at 0 to 1180 ° C. for 1 to 6 hours, 45
An aging treatment step of holding at 0 to 950 ° C for 1 to 8 hours is preferable.

The R-Fe-B in the present invention will be described below.
The reasons for limiting the composition of the slab for a C-based permanent magnet alloy will be described.
The rare earth element R contained in the cast slab for permanent magnet alloy of the present invention is a rare earth element including yttrium (Y) and including light rare earths and heavy rare earths. As R, a light rare earth element is sufficient, and Nd and Pr are particularly preferable. Also usually R
One of them is sufficient, but in practice, a mixture of two or more (Missille metal, didymium, etc.) can be used for reasons such as convenience in obtaining, and Sm, Y, La, Ce, Gd.
Etc. can be used as a mixture with other R, especially Nd, Pr, etc. It should be noted that this R does not have to be a pure rare earth element, and may contain impurities that are unavoidable in production within the industrially available range.

R is an essential element of the alloy slab for producing the R-Fe-B-C type permanent magnet. If it is less than 10 atomic%, high magnetic properties, especially high coercive force cannot be obtained, and R is 30 atomic%. If it exceeds, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, R is 10 atom% to 3
The range is 0 atomic%.

B and C are essential elements of the alloy slab for producing R-Fe-B-C type permanent magnets. If B + C is less than 4 atomic%, a high coercive force (iHc) cannot be obtained, and 15 %
When the number of atoms exceeds, the residual magnetic flux density (Br) decreases,
An excellent permanent magnet cannot be obtained, and when B is 2 at% or more, high corrosion resistance of the sintered magnet cannot be obtained. Therefore, B + C
Is 4 at% to 15 at% and B2 at% or less.

When Fe is less than 55 atomic%, the residual magnetic flux density (Br) is lowered, and when it exceeds 86 atomic%, a high coercive force cannot be obtained, so Fe is limited to 55 atomic% to 86 atomic%. The reason for substituting a part of Fe with one or two of Co and Ni is that the effect of improving the temperature characteristics of the permanent magnet and the effect of further improving the corrosion resistance can be obtained. When 1% or 2% exceeds 50% of Fe, a high coercive force cannot be obtained and an excellent permanent magnet cannot be obtained. Therefore, one or two substitutions of Co and Ni are Fe
50% of the upper limit.

In order to obtain an excellent permanent magnet having both a high residual magnetic flux density and a high coercive force in the magnet alloy slab of the present invention, R12 atom% to 18 atom%, B + C =
5 to 10 at%, B2 at% or less, Fe 72 atom% to 8
3 atom% is preferable. Further, the magnet alloy slab according to the present invention can tolerate the presence of impurities inevitable in industrial production in addition to C, R, B and Fe. By substituting at least one of S of 0.5 atomic% or less and Cu of 3.5 atomic% or less with a total amount of 4.0 atomic% or less, the manufacturability of the magnet alloy can be improved and the cost can be reduced. is there.

Further, in the R-Fe-BC alloy containing R, B, C and Fe, 9.5 atomic% or less of Al,
4.5 atomic% or less Ti, 9.5 atomic% or less V, 8.
5 atomic% or less Cr, 8.0 atomic% or less Mn, 5 atomic% or less Bi, 12.5 atomic% or less Nb, 10.5 atomic% or less Ta, 9.5 atomic% or less Mo, W of 9.5 atomic% or less, Sb of 2.5 atomic% or less, Ge of 7 atomic% or less, Ga of 7 at% or less, Sn of 3.5 atomic% or less,
By adding at least one of Zr of 5.5 atomic% or less and Hf of 5.5 atomic% or less, a high coercive force of the permanent magnet alloy becomes possible. R-B-Fe of this invention
In a -C permanent magnet, it is essential that the main phase of the crystal phase is a tetragonal crystal, and in particular, in order to obtain a fine and uniform alloy powder and to produce a sintered permanent magnet having excellent magnetic properties. It is effective.

[0047]

According to the present invention, a strip-cast R-Fe-B-C type alloy having a specific composition with a specific plate thickness is roughly pulverized, and then a specific lubricant is added to the obtained coarsely pulverized powder.
By finely pulverizing with a jet mill, it is possible to subdivide the crystal grains of the main phase forming the alloy ingot, and it is possible to produce a powder with a uniform grain size distribution. When finely pulverized after adding a lubricant to the alloy powder in which the R ₂ Fe ₁₄ (B _1-x C _x ) phase is also finely dispersed and finely pulverized, the fine pulverizing ability is improved to about twice as much as the conventional one. , The production efficiency is significantly improved, and the fine powder is momentarily oriented in the mold using a pulsed magnetic field, and then pressed and sintered to improve mold filling property and crystal orientation property, and corrosion resistance. And R-Fe-B- with excellent magnetic properties
A C-based permanent magnet can be obtained.

[0048]

【Example】

Example 1 Composition 13.5 Nd-obtained by melting in a high frequency melting furnace
1.0 Dy-10Co-1.5B-5.5C-68.5
Using a twin roll type strip caster provided with two copper rolls having a diameter of 200 mm, the molten alloy of Fe was used to obtain a thin plate-shaped slab having a plate thickness of about 0.3 mm. The crystal grain size in the slab is 0.5 μm to 15 μm in the minor axis direction, 5 μm to 80 μm in the major axis direction, and the R-rich phase is finely separated to about 3 μm so as to surround the main phase. To do. After breaking the slab into 50 mm square or less, 1000 g of the broken piece was housed in a closed container capable of sucking and exhausting, and N ₂ gas was allowed to flow into the container for 30 minutes to be replaced with air, and then, inside the container. 3 kg / cm ² of H ₂ gas was supplied for 2 hours to occlude the slab by H ₂ occlusion, and after de-H ₂ treatment in vacuum, it was cooled to room temperature and further pulverized to 100 mesh. .

Next, 800 collected from the coarsely crushed powder
g fatty acid ester as liquid lubricant (active ingredient 50%
After adding 1 wt% of cyclohexane (50%), the mixture was pulverized by a jet mill to obtain an alloy powder having an average particle size of 3.5 μm.
The obtained powder was filled into a urethane rubber mold (inner diameter φ25 × height 20 mm) having a hardness Hs = 40 so as to have a packing density of 3.3 g / cm ³ , and then the pulse magnetic field strength was 40 kO.
e, applying once for 8/100 seconds for orientation,
The oriented sample was cold isostatically pressed at a pressing pressure of 1.2 ton / cm ² to obtain a molded body. The molded body taken out of the mold was sintered under conditions of 1040 ° C. for 3 hours and was subjected to an aging treatment at 900 ° C. for 1 hour to obtain a permanent magnet. Table 1 shows the magnetic properties and corrosion resistance of the obtained permanent magnets.

Example 2 When a fine powder of alloy having an average particle size of 3.5 μm obtained under the same composition and under the same conditions as in Example 1 was used to produce a permanent magnet under the same conditions as in Example 1, a pulse magnetic field of 20 kOe was applied. ~ 80k
When variously changed to Oe, the maximum energy product value (BH) max (MGOe) of the obtained permanent magnet was examined, and the relationship with the pulse magnetic field strength is shown by the broken line in FIG.

Example 3 A disintegrated alloy powder obtained by subjecting a strip casting slab having the same composition as in Example 1 to H ₂ occlusion treatment under the same conditions as in Example 1 was heated and held in vacuum at 500 ° C. for 5 hours. Then, after removing H ₂ and adding 0.1 wt% of zinc stearate as a solid lubricant to 20 μm of coarsely pulverized powder, 7 kg
/ Jet-milled in an Ar gas of cm ^2, 1 times a pulse magnetic field similarly about 40kOe Example 1, 8/10
After applying for 0 seconds for orientation, cold isostatic pressing was performed, followed by sintering and aging treatment to obtain a permanent magnet. Table 1 shows the magnetic properties and corrosion resistance of the obtained permanent magnets.

Comparative Example 1 A molten alloy having the same composition as in Example 1 was used to measure dimensions of 30 mm × 100.
50 mm of the ingot obtained by casting in a mm × 200 mm mold
After fractured to less than mm mm, the fractured pieces were subjected to H ₂ occlusion treatment and de-H ₂ treatment under the same conditions as in Example 1 and then subjected to the same conditions as in Example 1 without adding a lubricant. Pulverization, pressing in a magnetic field, sintering, and aging treatment were performed to obtain a permanent magnet.
The grain size of the ingot is 30μm in the short axis direction and 300μ in the long axis direction.
m, and the R-rich phase was locally scattered in a size of about 60 μm. Table 1 shows the results of the obtained magnetic properties and corrosion resistance. The particle size distribution of the finely pulverized powder obtained is shown in FIG.

Comparative Example 2 An ingot having the same composition as that of Comparative Example 1 was ruptured to 50 mm or less and subjected to solution treatment at 900 ° C. for 10 hours in an inert gas atmosphere. H ₂ occlusion treatment and thermal dehydrogenation H ₂ treatment were performed, and after fine pulverization under the same conditions as in Example 1 without adding a lubricant, pressing in a magnetic field, sintering,
Aging treatment was performed to obtain a permanent magnet. Table 1 shows the results of the obtained magnetic properties and corrosion resistance. The particle size distribution of the finely pulverized powder obtained is shown in FIG.

Comparative Example 3 An ingot having the same composition as that of Comparative Example 1 was ruptured to 50 mm or less and subjected to solution treatment at 900 ° C. for 10 hours in an inert gas atmosphere, and then H _{2 under the} same conditions as in Example 3. and storage de-H ₂ treatment,
The same lubricant as in Example 1 was added to 20 μm coarsely pulverized powder and finely pulverized with a jet mill to obtain an alloy powder with an average particle size of 3.5 μm, which was subjected to a pulse magnetic field of about 40 kOe at 1
It was applied once every 8/100 seconds for orientation, and after compression molding, sintering and aging treatment were performed to obtain a permanent magnet. Table 1 shows the results of the obtained magnetic properties and corrosion resistance.

Comparative Example 4 The composition is 13.5Nd-1.0Dy-7B-78.5Fe.
A permanent magnet was obtained under the same conditions and method as in Example 1 except for the above. The results of the obtained magnetic properties and corrosion resistance are shown in Table 1.

[0056]

[Table 1]

Example 4 In Example 1, a pulse magnetic field of about 40 kOe was applied once,
Permanent magnets were manufactured under exactly the same conditions, except that they were applied four times for 8/100 seconds and oriented. Table 2 shows the results of the magnetic characteristics obtained by applying four times. FIG. 3 shows the relationship between the maximum energy product value (BH) max (MGOe) of the obtained permanent magnet and the number of pulse magnetic fields, the first time, the second time, the third time, and the fourth time.

Example 5 In Example 1, a pulse magnetic field of about 40 kOe was applied once,
A permanent magnet was manufactured under exactly the same conditions except that the magnetic field directions were alternately inverted and applied four times for 8/100 seconds, and the orientation was performed. Table 2 shows the results of the obtained magnetic characteristics obtained by applying four times. FIG. 3 shows the relationship between the maximum energy product value (BH) max (MGOe) of the obtained permanent magnet and the number of pulse magnetic fields, the first time, the second time, the third time, and the fourth time. Furthermore, when manufacturing a permanent magnet under the same conditions as above, the number of pulse magnetic fields was set to 4 and the pulse magnetic field was 20 kOe to 80 kO.
The maximum energy product value (BH) max (MGOe) of the obtained permanent magnet was examined in the case of various changes with e, and the relationship with the pulse magnetic field strength is shown by the solid line in FIG.

Example 6 In Example 5, raw material powder was filled in a rubber mold, and the magnetic field of about 12 kOe was applied by a hydrostatic pressing device after orientation was performed by alternately inverting and applying the pulse magnetic field direction four times. A permanent magnet was manufactured under exactly the same conditions except that cold isostatic pressing was performed at a pressure of 2.5 T / cm ² . The results of the obtained magnetic properties are shown in Table 2.

Comparative Example 5 In Example 4, the finely pulverized powder pulverized by the jet mill was mixed with 9
A pulsed magnetic field of kOe in the same direction was applied once for 10/100 seconds four times, and compression molding was performed under the same conditions except for orientation, followed by sintering and aging treatment to obtain a permanent magnet. The results of the obtained magnetic properties are shown in Table 2.

[0061]

[Table 2]

[0062]

The production method according to the present invention is obtained by forming an R-Fe-B-C alloy melt having a specific composition by strip casting into a slab of a specific plate thickness, and roughly crushing the slab. By adding and blending a specific lubricant to the alloy powder and finely pulverizing with a jet mill, it becomes possible to subdivide the crystal grains of the main phase forming the alloy lump, and as shown in the examples, the grain size A powder with a uniform distribution is
The R-rich phase and the R ₂ Fe ₁₄ B phase are also finely divided at the time of crushing, and when magnetized by hydrostatic pressing using a unidirectional or reversal pulse magnetic field, the orientation is improved. It is possible to obtain an R-Fe-B-C based permanent magnet having improved and excellent corrosion resistance and extremely high magnetic properties.

[Brief description of drawings]

FIG. 1 is a graph showing a particle size distribution of finely pulverized powder in an example.

FIG. 2 is a graph showing the relationship between the pulse magnetic field strength and the maximum energy product value.

FIG. 3 is a graph showing the relationship between the number of pulsed magnetic fields and the maximum energy product value.

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[Procedure amendment]

[Submission date] August 17, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0056

[Correction method] Change

[Correction content]

[0056]

[Table 1]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0061

[Correction method] Change

[Correction content]

[0061]

[Table 2]

Claims (6)

[Claims] 1. R (where R is at least one of rare earth elements including Y) 10 at% to 30 at%, B + C
= 4 to 15 at%, B2 at% or less, the balance Fe (however, one part of Fe can be replaced by one or two kinds of Co and Ni) and the unavoidable impurities, and the molten alloy is plated by a strip casting method. Thickness 0.03mm-10mm
Of a thin plate of R-rich phase having a structure in which the R-rich phase is finely separated to 10 μm or less, and then coarsely crushed to obtain coarsely pulverized powder having an average particle size of 10 to 500 μm, which is a liquid lubricant or solid. 0.02-5.0 wt% of a lubricant was added and mixed and finely pulverized, and the obtained fine powder having an average particle size of 1 to 10 μm was filled in a mold to a packing density of 1.4 to 3.5 g / cm ^3. A method for producing an R-Fe-B-C based permanent magnet material having excellent corrosion resistance, which comprises subjecting a magnetic field to momentarily applying a pulse magnetic field of 10 kOe or more, followed by forming, sintering and aging. 2. The R-Fe-B-C excellent in corrosion resistance according to claim 1, wherein the coarsely pulverized powder is obtained by a H ₂ storage-disintegration method.
Of manufacturing a permanent magnet material. 3. The method for producing an R—Fe—B—C permanent magnet material having excellent corrosion resistance according to claim 1, wherein the liquid lubricant has at least one fatty acid ester dissolved therein. 4. A solid lubricant comprising at least one of zinc stearate, copper stearate, aluminum stearate and ethylene vinylamide, R-Fe- having excellent corrosion resistance according to claim 1. A method for manufacturing a BC permanent magnet material. 5. The R-Fe-B excellent in corrosion resistance according to claim 1, wherein the applied magnetic fields have the same magnetic field direction.
-A method for producing a C-based permanent magnet material. 6. The method for producing an R—Fe—B—C permanent magnet material having excellent corrosion resistance according to claim 1, wherein the applied pulse magnetic field is applied by reversing the magnetic field direction repeatedly.