JPH066727B2 - Method for producing raw material powder for permanent magnet material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a powder for a raw material of a Fe—BR permanent magnet material, and in particular, it is safe to handle and press-molded in the atmosphere. Possible and stable Fe-BR
The present invention relates to a method for producing a raw material powder for a permanent magnet material.

BACKGROUND ART At present, there is a demand for a permanent magnet material that has high magnetic properties and is inexpensive, and there is a strong demand for a permanent magnet material that is rich in resources and that can be stably supplied in the future with a composition element. As a new high-performance permanent magnet containing no expensive Sm or Co, an Fe-BR type permanent magnet (R is at least one of rare earth elements including Y) is proposed (Japanese Patent Laid-Open No. 59-4600).
No. 8, JP-A-59-64733, JP-A-59-89401, JP-A-59-
No. 132104). This permanent magnet uses a resource-rich light rare earth centered on Nd and Pr as R, and has an extremely high energy product of 20 MGOe or more with Fe as the main component.
It is an excellent permanent magnet.

The rare earth metal as a starting material for producing the novel Fe-B-R system, Fe-Co-B-R system (R is at least one of rare earth elements including Y) permanent magnet is generally C
a Reduction method and electrolysis method are used, and the novel permanent magnet is manufactured by using the rare earth raw material, for example, in the following step.

As a starting material, electrolytic iron having a purity of 99.9%, a ferroboron alloy containing B19.4% and the balance being Fe and impurities such as Al, Si and C, a rare earth metal having a purity of 99.7% or more, or further, having a purity of 99.9%. Electrolytic Co is melted by high frequency, then cast in a water-cooled copper mold, roughly crushed by a stamp mill to a size of 35 mesh through, then crushed by a ball mill attritor, for example, 300 g of coarsely crushed powder for 6 hours, and finely ground to 3 to 10 μm. Form into powder, orient in a magnetic field (10 kOe) and form (pressurize at 1.5 t / cm ² ), sinter, 1000 ° C. to 1200 ° C., 1 hour, let stand to cool after sintering in Ar.

As described above, this alloy powder for permanent magnets can be obtained by mechanically pulverizing and finely pulverizing an ingot of the required composition.However, this alloy for magnets is extremely difficult to pulverize, and coarsely pulverized powder is flattened. In addition, the load of the crusher is high and it is easily worn, and it is difficult to mass-produce the 35-mesh through powder required in the next fine crushing step, and the yield and crushing efficiency of the coarsely crushed powder are high. There were problems such as badness.

Therefore, the applicant has previously proposed a production method by the Ca reduction method as a production method of alloy powder for permanent magnets which does not require mechanical coarse pulverization (Japanese Patent Laid-Open No. 59-219404), and further, Proposed a method for producing alloy powder for rare earth magnets by Ca reduction with reduced carbon and carbon contents (Japanese Patent Application No. 59-182574)
No., Japanese Patent Application No. 59-248798).

The gist is that at least one of rare earth oxides and at least one of iron powder, pure boron powder, ferroboron powder and boron oxide, or alloy powder or mixed oxide of the above welfare elements should be provided so that the required composition is obtained. In a mixed powder of the above composition, the amount of metal Ca and the rare earth oxide is 1.5 to 3.5 times (the weight ratio) the stoichiometrically necessary amount with respect to the amount of oxygen contained in the raw material powder such as the above rare earth oxide. 1 wt% to 15 wt% of CaCl2
Are mixed and subjected to reduction diffusion at 900 ° C. to 1200 ° C. in an inert gas atmosphere, the obtained reaction product is put into water to form a slurry, and the slurry is further treated with water, or further, the slurry is added. Is treated with ion-exchanged water cooled to 15 ° C or lower.

The raw material powder obtained by the Ca reduction method is effective in reducing the manufacturing cost, because the melting, agglomeration, and coarse crushing steps such as ingot crushed powder are omitted.

However, the coarsely pulverized powder obtained by the Ca reduction method is further finely pulverized, and such fine pulverization is performed by wet pulverization with a ball mill attritor or the like. Input, finely pulverized, Ca
In the Fe-BR rare earth magnet material powder obtained by the reduction method, the reduced rare earth element and B are mainly infiltrated and diffused into the Fe powder, and the central portion of the obtained reduced powder is R. ₂ Fe ₁₄ B
The compound having a tetragonal structure represented by the following chemical formula is a R-rich phase in which the peripheral portion is rich in rare earth elements, and the R-rich phase easily reacts with C or Cl in an organic solvent to produce a product magnet. Reduces magnetic properties. In particular, C adversely affects the magnetic properties and corrosion resistance. Further, since problems such as mixing of foreign matters due to wear of the balls occur, a dry pulverization method has been recently adopted.

However, since the surface of finely pulverized powder produced by a jet mill for dry pulverization is extremely activated, there is concern about ignition associated with oxidation when it is taken out from the pulverizer or when press-molded in the atmosphere, and its handling is difficult. There was a problem that press molding was difficult.

As measures against this, means such as gradually oxidizing the jet mill pulverized powder in a small amount of O ₂ -containing atmosphere before press molding, or stabilizing the fine powder in an O ₂ -containing organic solvent. However, the above method has a problem that it is difficult to form a strong oxide film on the surface of the fine powder after the stabilization treatment, the powder is difficult to stabilize, and the manufacturing cost increases.

The object of the present invention is to improve the jet mill pulverization method in the production of raw material powders for permanent magnet materials containing rare earths, boron and iron as main components, to obtain more stable fine powders, and to perform press molding in the atmosphere. Fe-B-R, which enables high press efficiency, prevents deterioration of product quality, and has excellent magnet characteristics.
An object of the present invention is to provide a method for producing a raw material powder capable of producing a permanent magnet material.

Structure and Effect of the Invention The inventors have made various studies on a method for obtaining a raw material powder of a permanent magnet material capable of preventing ignition in the air after fine pulverization or performing press molding in the air and having stable magnet characteristics. As a result, the finely pulverized powder obtained by finely pulverizing the coarsely pulverized powder having a specific particle size obtained by the above Ca reduction method into a fine powder in a supersonic inert gas flow containing a specific amount of O ₂ is obtained. , A stable oxide film is formed on the surface, ignition is prevented when taken out from the crusher or when press molding in the atmosphere, stable press molding is possible, press efficiency is improved, product magnet It was found that the characteristics, shapes, and dimensional variations were reduced, and that it had a great effect on improving the product yield.

That is, the present invention provides R (R is at least one of Nd, Pr, Dy, Ho, Tb, or further La, Ce, Sm, Gd, Er, EuTm, Yb, Lu, Y).
In the method for producing an alloy powder for a rare earth magnet, which comprises 12 atomic% to 20 atomic%, B4 atomic% to 20 atomic%, Fe65 atomic% to 81 atomic% as a main component, a Ca reduction method is used. The coarsely pulverized powder having an average particle size of 500 μm to 10 μm obtained in 1. is injected into a pulverization chamber for supersonic inert gas flow pulverization containing O ₂ at 50 ppm to 60,000 ppm, and finely pulverized to a fine powder having an average particle size of 1.5 μm to 5 μm. A method for producing a raw material powder for a permanent magnet material, comprising:

The permanent magnet material obtained by the above production method has a compound having a tetragonal crystal structure having an average crystal grain size in the range of 1 to 80 μm as a main phase and a nonmagnetic phase of 1% to 50% by volume. (Excluding oxide phase) is included, and R is mainly a light rare earth which is rich in resources centered on Nd or Pr, and Fe, B, and R are the main components. 20
It is possible to inexpensively obtain an Fe-BR type permanent magnet material having an extremely high energy product equal to or higher than MGOe, a high residual magnetic flux density, and a high coercive force.

Disclosure of the Invention Based on the Drawings The first is a vertical cross-sectional explanatory view of a jet mill crusher.

In the manufacturing method according to the present invention, first, Nd oxide (Nd ₂ O ₃ )
Or at least one light rare earth oxide such as Pr oxide (Pr ₆ O ₁₁ ) or a heavy rare earth oxide such as Tb oxide (Tb ₃ O ₄ ) or Dy oxide (Dy ₂ O ₃ ). At least one, Fe powder, pure boron powder, ferroboron powder (Fe-B powder), B
_When at least one raw material powder of boron oxide such as ₂ O ₃ powder, or Co or an additive element is contained, the respective metal powders, alloy powders, and oxide powders are mixed so as to have a required composition, and necessary. Depending on the, metal powder, oxide powder (including mixed oxide with constituent elements), alloy powder (including mixed oxide with constituent elements)
Alternatively, an additive element is added as another Ca-reducible compound powder to obtain a raw material mixed powder.

Furthermore, metallic Ca powder as a reducing agent for rare earth elements and CaCl ₂ powder for facilitating the decomposition of the reduction reaction product are added to the above raw material mixed powder. The required amount of metal Ca is 1.1 to 3.5 times the stoichiometrically required amount with respect to the amount of oxidation contained in the raw material powder such as rare earth oxide, and CaC1 ₂ is 1 wt% to 15 wt% of the rare earth oxide. To do.

After arranging a predetermined amount of the above-mentioned rare earth oxide, raw material powder and reducing agent, mixing is performed in an inert gas atmosphere using, for example, a V-type mixer. Then, the mixed powder is heated in an inert gas atmosphere at a temperature range of 900 ° C to 1200 ° C for 0.5
The reduction / diffusion reaction is carried out for 5 hours. At this time, the temperature rising rate is preferably 5 ° C./min or less in order to remove the adsorbed moisture gas component contained in the starting raw material powder.

The obtained reduction reaction product is put into ion-exchanged water cooled to 15 ° C. or lower, and the reaction by-product is reacted with H ₂ O to form Ca (OH) ₂ , that is, stoichiometrically. The required amount
The reduction reaction product obtained by blending 1.1 to 3.5 times the reducing agent is heated in water and spontaneously disintegrates into a slurry state, which is advantageous in that it does not require special mechanical pulverization. This slurry was further subjected to a treatment for sufficiently removing Ca by using ion-exchanged water cooled to 15 ° C. or less, and further vacuum dried at room temperature to obtain an alloy for a Fe-BR permanent magnet of 10 to 500 μm. Get a powder.

The obtained coarsely pulverized powder (1) having an average particle size of 500 μm to 10 μm is charged into the raw material popper (2) of the jet mill pulverizer, and the cutout port of the raw material hopper (2) is connected to the O ₂ supply pipe (3). It is connected and fitted in the middle of a gas introduction pipe (5) branched from the arranged inert gas supply main pipe (4).

The coarsely pulverized powder (1) is crushed by the supersonic inert gas containing 50 ppm to 60,000 ppm of O ₂ flowing in the gas introduction pipe (5).
Injected in (6) tangentially to the circulating flow therein.

At this time, the raw material powder and the supersonic inert gas collide with each other, the powders collide with each other, or the powder collides with the wall of the grinding chamber, and is finely ground by friction.

The ultra-fine powder descends into a cyclone (7) connected to the center of the crushing chamber (6), floats and swirls, and further passes through a vertical discharge pipe (8) arranged in the center of the cyclone, and then an inert gas. Along with this, it is discharged to the outside and further classified.

On the other hand, the fine powder that fell with the ultrafine powder was a cyclone.
(7) The hopper (9) for cutting out at the bottom is opened in a state where it is deposited on the bottom and the feeding of the inert gas is stopped, and the product is taken out as a product to obtain a fine powder raw material powder having an average particle size of 1.5 μm to 5 μm.

The obtained fine powder is subjected to the above-mentioned powder metallurgical manufacturing process, for example, after being formed into the required shape and size in the limit orientation, sintered in a vacuum and allowed to cool, and further subjected to an aging treatment in an Ar atmosphere. A permanent magnet material is obtained through the process.

Preferred Embodiment of the Invention In the present invention, when the amount of O ₂ mixed in the supersonic inert gas is 50 ppm, a stable oxide film cannot be formed on the fine powder surface, and when it exceeds 60,000 ppm, the fine powder surface is not formed. Since the oxide film formed in 1) is too thick and the magnetic properties of the product are deteriorated, it is not preferable, and the O ₂ amount is limited to 50 ppm to 60,000 ppm. A preferred range is 80 ppm to 30,000 ppm.
A more preferable range is 100 ppm to 10,000 ppm.

Further, in the present invention, if the average particle size of the coarsely pulverized powder due to natural disintegration by the Ca reduction method is less than 10 μm, it is difficult to handle the raw material as a whole in the air, and the magnet characteristics are deteriorated by the oxidation of the raw material powder. Not preferred, 500 μm
If it exceeds, the crushing efficiency of the crusher is remarkably reduced, and the average particle size of the coarsely crushed powder is 10 μm to 500 μm.
Becomes

If the average particle size of the finely pulverized powder according to the present invention is less than 1.5 μm, the degree of oxidation of the powder increases, which is not preferable, and if it exceeds 5 μm, the sintered permanent magnet of Since the particle size becomes large, the magnetization reversal easily occurs, and the coercive force is lowered, which is not preferable.
The average particle size is μm to 5 μm.

Further, in the present invention, the magnetic field condition when the finely pulverized raw material powder is molded into a required shape and size in a magnetic field is 7 kOe to 20 k.
Oe are preferable, pressing ^{conditions, 0.5t / cm 2 ~8t / cm} 2 is preferred.

The temperature condition in sintering is preferably 900 ° C to 1200 ° C, more preferably 1000 ° C.
The temperature is preferably 1150 ° C, and the time is preferably 30 minutes to 8 hours. 900 ° C
If it is less than 12%, sufficient strength as a sintered magnet body cannot be obtained.
If the temperature exceeds 00 ° C, the sintered body is deformed, the orientation is disturbed, the magnetic flux density is lowered, the squareness is lowered, and the crystal grains are coarsened to lower the coercive force, which is not preferable.

Further, in this invention, in order to improve and improve the residual magnetic flux density, coercive force, and squareness of the demagnetization curve of the magnet material,
~ Aging treatment at a sintering temperature is preferable. If the aging temperature is lower than 350 ° C, there is no effect because the diffusion rate decreases, and if it exceeds the sintering temperature, re-sintering occurs and oversintering occurs.

Furthermore, the aging treatment temperature is preferably in the range of 450 ° C. to 800 ° C., and the aging treatment time is preferably 5 minutes to 40 hours. 5
If it is less than 5 minutes, the effect of aging treatment is small and the variation of the magnetic properties of the obtained magnet material becomes large. If it exceeds 40 hours, it takes a long time industrially and is not practical. The aging treatment time is preferably 30 minutes to 8 hours from the viewpoint of preferable expression of magnet characteristics and practical use. Further, as the aging treatment, a multi-step aging treatment having two or more steps can be used.

Also, instead of the multi-step aging treatment, a cooling method from the aging treatment temperature of 400 ° C to the sintering temperature to room temperature may be performed by cooling with air cooling or water cooling, or by a method of cooling at a cooling rate of 0.2 ° C / min to 20 ° C / min. It is possible to obtain a permanent magnet material having the same magnetic characteristics as those of the above-mentioned aging treatment.

Reasons for Limiting Components of Raw Material Powder for Permanent Magnet Material The rare earth element R used in the raw material powder for permanent magnet material of the present invention occupies 12 atom% to 20 atom% of the composition, but Nd, P
At least one of r, Dy, Ho, Tb, or further La, Ce, Sm, Gd, Er, EuhTm, Yb, Lu, Y
Among them, those containing at least one kind are preferable.

In addition, usually one of R (preferably Nd, Pr, Dy, H
O, Tb, etc.) is sufficient, but in practice, a mixture of two or more kinds (Misch metal, didymium, etc.) can be used for reasons such as availability.

Further, it is preferable that Sm and La in R constituting the main phase are as small as possible, for example, Sm is 1 atom% or less, more preferably 0.5 atom% or less.

In addition, in order to improve the temperature characteristics, as an R mixed system, N
Desirably, d, Pr, or a combination of 0.005 atom% to 5 atom%, preferably 0.2 atom% to 3 atom% of Dy, Ho, Tb, etc., is added.

Furthermore, from the viewpoint of characteristics, cost and resources, R is
Nd and Pr are preferably 50% or more, and more preferably 80% or more of the total R.

R is the raw material powder for the above new permanent magnet material,
It is an essential element, and if it is less than 12 atomic%, the crystal structure is a-
Since a cubic crystal structure having the same structure as iron is deposited, high magnetic properties, especially high coercive force cannot be obtained.
The rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, the rare earth element content is in the range of 12 atom% to 20 atom%.

B is an essential element in the raw material powder for a permanent magnet according to the present invention. If it is less than 4 atomic%, the rhombohedral structure becomes the main phase and a high coercive force (iHc) cannot be obtained, and if it exceeds 20 atomic%. , B-rich non-magnetic phase increases and residual magnetic flux density
Since (Br) is lowered, an excellent permanent magnet cannot be obtained. Therefore, B is in the range of 4 atom% to 20 atom%.

Fe is an essential element in the new raw material powder for permanent magnet materials, and if the content is less than 65 atom%, the residual magnetic flux density
If (Br) is lowered and exceeds 81 atom%, a high coercive force cannot be obtained, so Fe is contained at 65 atom% to 81 atom%.

Further, in the raw material powder for a permanent magnet material according to the present invention, substituting a part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet. Although the oxidation resistance can be improved, if the Co substitution amount exceeds 25% of Fe, the magnetic characteristics are deteriorated, which is not preferable. The atomic ratio of Co is Fe and C
In the case where the total amount of o is 5% to 15, (Br) is increased as compared with the case where no substitution is carried out, which is preferable for obtaining a high magnetic flux density.

Further, the permanent magnet material according to the present invention can tolerate the presence of impurities unavoidable in industrial production in addition to R, B and Fe, but part of B is 4.0 atomic% or less of C and 2.0 atomic% or less of P. , S of 2.0 atomic% or less and Cu of 2.0 atomic% or less, by substituting 2.0 atomic% or less in total, it is possible to improve the manufacturability and reduce the cost of the permanent magnet.

Further, at least one of the following additional elements is RB-
It can be added to the Fe-based permanent magnet material because it is effective in improving the coercive force, the squareness of the demagnetization curve, the productivity, and the cost.

5.0 atomic% or less A1, 3.0 atomic% or less Ti, 5.5 atomic% or less V, 4.5 atomic% or less Cr, 5.0 atomic% or less Mn, 5.0 atomic% or less Bi, 9.0 atomic% or less Nb, 7.0 Ta less than atomic%, Mo less than 5.2 atomic%, W less than 5.0 atomic%, Sb less than 1.0 atomic%, Ge less than 3.5 atomic%, Sn less than 1.5 atomic%, Zr less than 3.3 atomic%, 6.0 atomic % Ni or less, 5.0 atom% or less Si, 1.1 atom% or less Zn, and 3.3 atom% or less Hf, at least one kind is added, but when two or more kinds are contained, the maximum content is By containing at most atomic% of the additive element having the maximum value,
It is possible to increase the coercive force of the permanent magnet. The upper limit of the amount of addition is set to a range that satisfies the condition because (Br) must be at least 9 kG or more in order to set (BH) max of the magnetic material to 20 MGOe or more.

The main phase of the crystal phase is tetragonal, which is indispensable for producing a sintered permanent magnet having excellent magnetic properties from a fine and uniform alloy powder.

In addition, the permanent magnet material of the present invention can be magnetically anisotropic magnet by press molding in a magnetic field, and can be magnetically isotropic magnet by press molding in a non-magnetic field. .

The permanent magnet material according to the present invention exhibits a coercive force iHc ≧ 5 kOe and a residual magnetic flux density Br> 9 kG, a maximum energy product (BH) max of 20 MGOe or more, and in a preferable composition range, the maximum value reaches 30 MGOe or more. .

Further, when the main component of R of the raw material powder for a permanent magnet material of the present invention is 50% or more of the light rare earth metal mainly composed of Nd and Pr, R12 atom% to 15 atom%, B6 atom% to 9
In the composition range of atomic%, Fe of 78 atomic% to 81 atomic%, and the amount of substitution of Co of 20 atomic% or less, excellent magnetic properties of (BH) max 35 MGOe or more are exhibited, especially when the light rare earth metal is Nd. , Its maximum value reaches 45 MGOe or more.

Examples Example 1 Nd ₂ O ₃ powder 174.3 g Dy ₂ O ₃ powder 17.3 g, Fe powder 216.9 g Ferroboron powder 21.9 g (19.5 B-Fe alloy powder) Metal Ca powder 162.9 g (chemically necessary amount for reduction) 2.4 times more) 6.7 g of CaCl ₂ powder (3.5 wt% of rare earth oxide raw material) Using 600 g of the total raw material powder, 30.5 Nd-3.6 Dy-1.15 B-64.75 Fe (wt%), 14.1 Nd-1.5 Dy- Targeting 7.1B-77.3Fe (at%), V
Mixing was performed in an Ar gas atmosphere using a mold mixer.

Then, the mixed powder was accelerated in the reducing gas diffusion atmosphere in an Ar gas flowing atmosphere of a reducing furnace at 1050 ° C. for 2.0 hours, and then cooled to room temperature.

600 g of the obtained reduction reaction product was put into ion-exchanged water cooled to 7 ° C. to form a slurry, and then the slurry-like alloy powder was washed several times with ion-exchanged water cooled to 7 ° C. After vacuum drying, an alloy powder according to the present invention was obtained.

Alloy powder obtained, component _{composition, N d 30.6wt%, Dy 3.5wt} %, B 1.11wt%, Fe 62.5wt%, O2 2000ppm, C 480pm, Ca 500ppm, particle size was 10~300μm .

Using the jet mill shown in FIG. 1, this coarsely pulverized powder is inert gas; N ₂ gas, gas pressure; 7 kg / cm ² gas velocity; Mach 2.5-containing O ₂ ; 5000 ppm N ₂ gas consumption; 2 m ³ / Jet pulverization was carried out under the condition of min to obtain fine pulverization having a pulverization particle size; 3.1 μm powder O ₂ content; 5500 ppm.

This fine powder is loaded into a die of a press machine, oriented in a magnetic field of 12 kOe, and shaped horizontally in the magnetic field at a pressure of 2.5 t / cm ² to obtain a molded body of 20 mm × 15 mm × 15 mm dimensions. Obtained.

The obtained molded body was sintered under the conditions of 1100 ° C. for 1 hour in Ar atmosphere, and further, aged at 570 ° C. for 1 hour in Ar atmosphere.

The magnetic properties of the obtained permanent magnet material were measured, and the results are shown in Table 1 together with the press efficiency.

Incidentally, Comparative Example 1 in Table 1, obtained by a wet attritor pulverization method, a fine powder of the same average particle size, under the conditions of the present invention, the required size, after molding in a magnetic field into a shape, sintering, It is the magnetic characteristics of the permanent magnet material that has been aged.

Further, Comparative Example 2 shows the magnet characteristics and press efficiency of the permanent magnet manufactured under the same conditions as those of the examples of the present invention, except that jet milling was performed with N ₂ gas containing no O ₂ during jet milling. .

[Brief description of drawings]

FIG. 1 is a vertical cross sectional view of a jet mill used in the present invention. 1 ... Coarse crushed powder, 2 ... Raw material hopper, 3 ... O ₂ supply pipe, 4 ...
Inert gas supply main pipe, 5 ... Gas introduction pipe, 6 ... Grinding chamber, 7
… Cyclone, 8… Discharge pipe, 9… Cutout hopper.

Claims (1)

[Claims] 1. R (R is at least one of Nd, Pr, Dy, Ho and Tb, or further La, Ce, Sm, Gd, Er and EuT.
of at least one of m, Yb, Lu and Y) 12 atom% to 20 atom%, B4 atom% to 20 atom%, Fe65 atom% to 81 atom% of the alloy powder for rare earth magnets In the manufacturing method, coarse pulverized powder having an average particle size of 500 μm to 10 μm obtained by the Ca reduction method is injected into a pulverizing chamber for supersonic inert gas gas flow pulverization containing O ₂ in an amount of 50 ppm to 60,000 ppm to obtain an average particle size of 1.5 μm to 5 μm. The method for producing a raw material powder for a permanent magnet material, comprising: