JP3009804B2 - Method for producing raw material powder for R-Fe-B-based permanent magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an R-Fe-based alloy containing R (R is at least one of rare earth elements including Y), Fe and B as main components.
B system relates to a method of manufacturing a raw material powder used in the production of the permanent magnet, R ₂ obtained by dissolving pulverization method Fe ₁₄ B phase R ₂ obtained by direct reduction diffusion process in the main phase alloy powder to main phase Fe ₁₇
R-Fe-B with a reduced amount of B-rich and Nd-rich phases that degrade magnet properties
Relates to the production how raw material powder for the system permanent magnet.

[0002]

2. Description of the Related Art Today, a typical R-type high performance permanent magnet
Fe-B-based permanent magnet (JP-A-59-46008) exhibits high magnet properties in a structure having a main phase and an R-rich phase of a ternary tetragonal compound, iHc is 25 kOe or more, (BH) With a max of 45MGOe or more, it exhibits remarkably high performance even when compared with conventional high performance rare earth cobalt magnets. Further, R-Fe-B permanent magnets of various compositions have been proposed so as to exhibit various magnet properties selected according to the application.

[0003] In order to produce R-Fe-B sintered permanent magnets having the above-mentioned various compositions, it is necessary to produce alloy powders for magnets having a required composition, using a rare earth material reduced by electrolysis. Melt and cast into a mold to create an alloy lump of the required magnet composition, pulverize and melt and pulverize to an alloy powder of the required particle size (JP-A-60-63304, JP-A-60-119701) and , Rare earth oxides, direct reduction diffusion method of preparing alloy composition powder directly using Fe powder etc. (JP 59-219404, JP 60-77943)
There is.

In the dissolution pulverization method, primary Fe crystals are easily generated during casting, and the R-rich phase is largely segregated. However, since the ingot can be easily pulverized in the coarse pulverization step, oxidation can be prevented. An alloy powder having an oxygen content is obtained.

[0005] direct reduction diffusion method, an advantage that it is possible to omit the step of melting and coarse grinding, etc. when creating the raw material powder for a magnet as compared with the dissolution pulverization method, R ₂ Fe
_{14 The} R-rich phase is created with the R-rich phase surrounding the B main phase.The size of the R-rich phase is small and well dispersed compared to the former, so it is easily oxidized during production and contains a large amount of oxygen. However, depending on the magnet composition, there is a problem that the rare earth element is consumed and causes a variation in magnet characteristics.

[0006]

SUMMARY OF THE INVENTION The inventor has previously proposed R-Fe-B
In order to reduce the oxygen content in the alloy powder that degrades the magnet properties of the permanent magnet, an alloy powder with a composition close to the R ₂ Fe ₁₄ B phase with a small R-rich phase was created by the direct reduction diffusion method. R
R including rich alloy powder, R ₃ Co phase by the addition of Co element (except the part or most of Co can be substituted by Fe)
₂ (Fe, Co) An intermetallic compound powder composed of ₁₇ phases and the like was prepared, and a raw material powder for R-Fe-B-based permanent magnet in which both were mixed was proposed (Japanese Patent Application No. 2-229685).

The raw material powder for R-Fe-B permanent magnets proposed above is extremely effective in reducing the oxygen content in the alloy powder and the obtained magnet, but the main phase R _In addition to the ₂ Fe ₁₄ B phase, there is an R-rich phase as a B-rich phase and a grain boundary phase,
It is extremely difficult to precisely control the abundance of each of these phases, and this has caused variations in magnet properties.

According to the present invention, the B-rich phase and the R-rich phase of the magnet constituting phase, which hinder high performance of the R-Fe-B-based permanent magnet characteristics, can be reduced as much as possible, and the main phase of the R ₂ Fe ₁₄ B phase is reduced. The present invention provides a method for producing a raw material powder for R-Fe-B-based permanent magnets, which can increase and further reduce the oxygen content in the alloy powder, and can easily provide an alloy powder having a composition according to various magnet properties with good productivity. It is an object.

[0009]

In general, in an R-Fe alloy, for example, an Nd-Fe alloy, the Nd ₂ Fe ₁₇ phase has a Curie point near room temperature,
An intermetallic compound having an easy magnetization direction in the C plane.Conventionally, in an R-Fe-B based sintered permanent magnet, when the B content is less than 6 atomic%, for example, a Nd ₂ Fe ₁₇ phase is contained in the magnet. It has been said that the coercive force is reduced by generation. However, as a result of various studies, the inventor found that R-Fe-B-based alloy powder having R ₂ Fe ₁₄ B
₂ Fe ₁₇ phase, for example, a raw material powder in which a specific amount of R-Fe alloy powder containing Nd ₂ Fe ₁₇ phase is added and blended, Nd in the Nd-rich phase of the grain boundary phase
And the eutectic temperature 690 around ℃ the Nd ₂ Fe ₁₇ of R-Fe-based alloy powder, for example, by reaction of Nd + Nd ₂ Fe ₁₇ phase ← → the liquid phase takes place, the liquid phase of the low melting point It has been found that sintering of R-Fe-B alloy powder is promoted.

Preparation alloy powder containing Nd ₂ Fe ₁₇ phase and R ₂ Fe ₁₄ B
The R-Fe-B-based alloy powder having a main phase has the following reaction during sintering, and has an effect of increasing the R ₂ Fe ₁₄ B phase as a main phase. 13 / 17Nd ₂ Fe ₁₇ + 1 / 4Nd _1.1 Fe ₄ B ₄ + 133 / 6800Nd → Nd ₂ Fe ₁₄
B In other words, in the above reaction formula, the inventor newly obtained the reaction between the Nd ₂ Fe ₁₇ phase in the alloy powder for adjustment and the B-rich phase and the Nd-rich phase in the main phase R-Fe-B-based alloy powder. Nd ₂ Fe ₁₄ B
Since a phase is generated, the B-rich phase and Nd, which are one of the factors deteriorating the magnet properties, in the permanent magnet obtained only with the alloy powder having the main phase of the R ₂ Fe ₁₄ B phase according to the conventional method. It has been found that the amount of the rich phase can be reduced.

[0011] Furthermore, when producing the R-Fe-B-based magnet by powder metallurgy, obtaining the raw material alloy powder that is easily crushed is a great advantage in the production of the magnet.
As a result of various studies on the production method of the raw material powder for the Fe-B permanent magnet, a main phase alloy powder having a main phase of R ₂ Fe ₁₄ B phase was produced by a melting and pulverization method, and an R ₂ Fe ₁₇ phase was produced. For R-Fe-B permanent magnets, which are prepared by directly reducing the diffusion alloy method containing the adjustment alloy powder containing the main phase-based alloy powder and the adjustment alloy powder in the required amount. Raw material powder was found.

That is, in the present invention, obtaining the main phase alloy powder having the R ₂ Fe ₁₄ B phase as the main phase by the melting and pulverizing method is a step which can be easily prevented from being oxidized in the ingot rough pulverizing step. Since it can be pulverized, an alloy powder with a relatively low oxygen content is obtained, and crystallized in the alloy by making the R and B contents excess from the stoichiometric composition of the R ₂ Fe ₁₄ B phase It is possible to reduce the crystallization amount of Fe primary crystals, and as a result, it is possible to obtain an alloy ingot that is extremely easily crushed. Further, in the present invention, the composition can be adjusted by adding and mixing a required amount of the adjusting alloy powder containing the R ₂ Fe ₁₇ phase to the main phase alloy powder, so that the composition of the main phase alloy powder can be adjusted to the above-mentioned R. ₂ R-Fe-B permanent magnets with magnet properties far superior to those of magnets made from only alloy lumps with R and B contents set to be excessively higher than the stoichiometric composition of the Fe ₁₄ B phase Can be manufactured. On the other hand, the advantage of obtaining the adjusting alloy powder by the direct reduction diffusion method is generally that when the R-Fe-B ternary alloy powder is manufactured by the direct reduction diffusion method, the Nd-rich phase becomes the main phase or the B-rich phase. , The Nd-rich phase is easily oxidized or hydroxylated, the oxygen content of the obtained alloy powder increases, and the alloy raw material powder becomes extremely unstable, so that R-Fe-B permanent Special atmosphere measures are required when manufacturing magnets, but in the present invention, the R ₂ Fe ₁₇ phase of the alloy powder for adjustment is a relatively stable compound as a single phase, so it is manufactured by the direct reduction diffusion method. However, an alloy powder having a low oxygen content can be obtained.
Moreover, when the adjusting alloy powder containing the R ₂ Fe ₁₇ phase is produced by a melting and pulverization method, α-Fe and other R-Fe compound phases are crystallized in the obtained alloy mass depending on casting conditions, so that the alloy is stable. In order to obtain a raw material alloy powder, it is necessary to heat treat the alloy ingot and homogenize it, and the direct reduction diffusion method is more advantageous than the production cost of the alloy powder.

That is, the present invention relates to a method for producing a compound comprising R (where R is at least one of rare earth elements including Y) of 12 at% to 20 at%,
Atomic% to 15 atomic%, the (a part of provided that Fe Co, can be substituted by one or two of Ni) balance of Fe and unavoidable impurities,
In the alloy powder having a main phase of R ₂ Fe ₁₄ B phase obtained by the melting and pulverization method, R (where R is at least a rare earth element including Y)
One) 20 atomic% or less, a part of the remainder Fe (except Fe Co, can be substituted by one or two of Ni) and consists unavoidable impurities, R ₂ Fe ₁₇ obtained by direct reduction diffusion process A method for producing a raw material powder for an R-Fe-B-based permanent magnet, characterized in that an adjusting alloy powder containing a phase is added and blended in an amount of 60 wt % or less of the mixed powder .

In the present invention, R to be added and compounded to an alloy powder having a main phase of R ₂ Fe ₁₄ B having specific amounts of R, Fe, and B is
The addition amount of the R-Fe-based adjusting alloy powder containing the R ₂ Fe ₁₇ phase of 20 atomic% or less was set to 60 wt % or less of the mixed powder because if it exceeds 60 wt %, an anisotropic magnet is produced. This is because when formed in a magnetic field, the amount of the uniaxially anisotropic R ₂ Fe ₁₄ B phase decreases and the degree of orientation decreases, which is not preferable, and leads to a decrease in Br. A more preferable addition amount is 0.1 to 40 wt %.

The rare earth element R used in the present invention is a rare earth element including Y and including light rare earths and heavy rare earths,
At least one of these, preferably a light rare earth element such as Nd or Pr, or a mixture with Nd, Pr or the like is used. That is, as R, Nd, Pr, La, Ce, Tb, Dy, Ho, E
r, Eu, Sm, Gd, Pm, Tm, Yb, Lu, Y can be used. 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.

In order to obtain an alloy powder having the R ₂ Fe ₁₄ B phase as a main phase, when R is less than 12 atomic%, the residual iron portion where R and B do not diffuse increases, and when R exceeds 20 atomic%, R increases. R is set to 12 at% to 20 at% because the rich phase increases and the oxygen content increases during grinding. A more preferred amount of R is 13 atomic% to 16 atomic%. B is less than 6 atomic%, a high coercive force (iHc) cannot be obtained, and if it exceeds 15 atomic%, the residual magnetic flux density (Br) decreases. 6 atom%
To 15 atomic%. More preferable B amount is 6 atomic% to 10 atomic%.
It is. Further, the balance consists of Fe and unavoidable impurities, and the content of Fe is preferably in the range of 65 atomic% to 82 atomic%. If Fe is less than 65 atomic%, the rare earth element and B become relatively rich and R
When the rich phase and the B-rich phase increase, and when the content exceeds 82 atomic%, the rare earth element and B relatively decrease, and the residual Fe portion increases, which is not preferable because the alloy powder becomes non-uniform. A more preferred amount of Fe is 74 atomic% to 81 atomic%. In main phase alloy powder
One or two of Co and Ni are substituted with Fe in the R ₂ Fe ₁₄ B main phase to reduce the coercive force, so that Co is 10 atomic% or less, Ni is 3 atomic% or less.
Atomic% or less. However, when a part of Fe is substituted by Co or Ni described above, the content of Fe is in the range of 55 to 72 atomic%.

In order to obtain an adjusting alloy powder containing the R ₂ Fe ₁₇ phase, if R exceeds 20 atomic%, an R-rich phase increases during the preparation of the alloy powder, which causes problems such as oxidation. Is preferably 5 to 15 atomic%. Further, the balance consists of Fe and unavoidable impurities, and the content of Fe is preferably in the range of 85 atomic% to 95 atomic%.

[0018] In the present invention, the alloy powder as a main phase an R ₂ Fe ₁₄ B phase is produced by a known dissolution grinding method, also R ₂ Fe ₁₇
The adjustment alloy powder containing the phase is produced by a known direct reduction diffusion method.

When the obtained powder is used as it is, if the particle size of the alloy powder is too large, the magnetic properties of the permanent magnet, especially a high coercive force, cannot be obtained. If the average particle size is less than 1 μm, the process of preparing the permanent magnet, That is, press molding, sintering, oxidation in the aging process is remarkable, excellent magnetic properties are not obtained, and if it exceeds 80 μm, it causes a decrease in coercive force, so an average particle size of 1 to 80 μm is preferable, and In order to obtain excellent magnetic properties, an alloy powder having an average particle size of 2 to 10 μm is desirable. In addition, using the obtained alloy powder, in order to obtain an excellent R-Fe-B-based permanent magnet having both a high residual magnetic flux density and a high coercive force, the compounded raw material powder is R12 atomic% to 25 atomic%. , B4% -10%, Co0.1 atom
% To 10 at%, and 68 to 80 at% Fe.

Further, the compounded alloy powder containing the R ₂ Fe ₁₄ B phase as a main phase and / or the adjustment alloy powder containing the R ₂ Fe ₁₇ phase contains Cu 3.5 atomic% or less, S2.5 atomic% or less, Ti4.5 atomic% or less, Si15 atomic% or less, V9.5 atomic% or less, Nb12.5 atomic% or less, Ta10.5 atomic% or less, Cr8.5 atomic% or less, Mo9.5 atomic% or less, W9.5 Atomic% or less, Mn3.5 atomic% or less, Al9.5 atomic% or less, Sb2.5 atomic% or less, Ge7 atomic% or less, Sn3.5 atomic% or less, Zr5.5 atomic% or less, Hf5.5 atomic% or less , Ca 8.5 atom% or less, Mg 8.5 atom% or less, Sr 7.0 atom% or less, Ba 7.0 atom% or less, Be 7.0 atom% or less Higher coercive force, higher corrosion resistance, and improved temperature characteristics of the permanent magnet can be achieved.

When the composition of the permanent magnet manufactured by using the alloy powder according to the present invention is R11 atomic% to 25 atomic%, B4 atomic% to 10 atomic%, Co 30 atomic% or less, Fe 66 atomic% to 82 atomic%, The obtained magnetic anisotropic permanent magnet has a coercive force _i H _C ≧ 5 kOe, (BH) max
The magnetic properties of ≧ 20MGOe are exhibited, and the temperature coefficient of the residual magnetic flux density is 0.1% / ° C. or less, and excellent properties are obtained. In the case where the main component of R in the permanent magnet composition occupies 50% or more of the light rare earth metal, R12 atom% to 20 atom%, B4 atom% to 10 atom%, Fe66 atom% to 82 atom%, Co20 atom %, The most excellent magnetic properties are exhibited. Particularly, when the light rare earth metal is Nd, Pr, or Dy, the maximum value of (BH) max reaches 40 MGOe or more.

[0022]

According to the present invention, R ₂ Fe ₁₄
It is adjusted by adding and blending the adjustment alloy powder containing the Nd ₂ Fe ₁₇ phase obtained by the direct reduction diffusion method of 60 wt % or less of the total amount to the R-Fe-B alloy powder having the B phase as the main phase. Reaction between the Nd ₂ Fe ₁₇ phase in the alloy powder for use and the B-rich phase and the Nd-rich phase in the main phase R-Fe-B-based alloy powder generates a new Nd ₂ Fe ₁₄ B phase, Various magnets that can adjust and reduce the amount of the B-rich phase and Nd-rich phase that degrade the magnet properties of the permanent magnet, improve the performance of the resulting magnet, and reduce the oxygen content in the alloy powder An alloy powder having a composition according to characteristics can be easily provided.

[0023]

[Example] Example 1 Raw materials in the melting and pulverization method of the main phase were 160 g of Nd metal (98% purity), 10.5 g of Dy metal (98% purity), 299 g of electrolytic iron with 99% purity, and B content of 19.1. % Fe-B powder 34 g, using a jaw crusher or a disk mill, pulverize the alloy mass obtained in an Ar atmosphere, and powder 450 having an average particle size of 10 μm.
g was obtained. The obtained powder was Nd 14.2 atomic%, Pr 0.2 atomic%, Dy
It consisted of 0.8 atomic%, B 8 atomic%, and the balance Fe. Observation by EPMA confirmed that the R ₂ Fe ₁₄ B phase was the majority. The oxygen content was 800 ppm. When the structure of the alloy mass was observed by EPMA, almost no crystallization of the primary Fe crystal was observed.

In addition, Nd ₂ O ₃ (purity: 98%) 255 g Dy ₂ O ₃ (purity: 98%) 23 g Electrolytic iron having a purity of 99% 765 g was used as a raw material of the adjusting alloy powder containing the R ₂ Fe ₁₇ phase. , This is 99% pure metal Ca 180g, anhydrous CaCl ₂
Then, the mixture was charged into a stainless steel container, and reduced and diffused with Ca at 950 ° C. for 3 hours in an Ar gas stream.
After cooling, the resulting mixture was washed with water to remove unnecessary Ca. The obtained powder slurry was replaced with alcohol and the like, and then dried by heating under vacuum to obtain about 900 g of raw material powder.
The obtained powder has Nd 9.7 atom%, Pr 91 atom%, Dy 0.8 atom
%, The balance being Fe, and it was confirmed by EPMA that it was almost a single phase of R ₂ Fe ₁₇ . The oxygen content was 700 ppm.

Using the above two kinds of raw material powders, a 25 wt % adjusting alloy powder was mixed and mixed with the main phase alloy powder. This raw material powder is charged into a pulverizer such as a jet mill and pulverized to about 3 μm, and the obtained fine powder is oriented in a magnetic field of about 10 kOe, and a pressure of about 1.5 Ton / cm ² is applied in a direction perpendicular to the magnetic field. 8m
A molded body of m × 15 mm × 10 mm was prepared. 1100
Sintering was carried out in an Ar atmosphere at 3 ° C. for 3 hours, followed by aging at 550 ° C. for 1 hour. Table 1 shows the magnet properties of the obtained magnet. Incidentally, when the R ₂ Fe ₁₄ B phase, the B-rich phase, and the R-rich phase (including oxides) were calculated from the magnet composition, in the present invention, 94:
0.5: 5.5.

Comparative Example 1 Nd ₂ O ₃ (purity 98%) 263 g Dy ₂ O ₃ (purity 98%) 16 g B content 19.1% Fe-B powder 49 g Electrolytic iron of 99% purity Using 417 g, 180 g of 99% pure metal Ca and anhydrous CaCl ₂ were added thereto.
After mixing 28 g, the mixture was charged into a stainless steel container, and subjected to Ca reduction diffusion in an Ar gas flow at 930 ° C. for 5 hours, and then cooled, and the resulting mixture was washed with water to remove unnecessary Ca components. Thereafter, treatment was performed to obtain 600 g of a main phase alloy powder composed of 14.2 atomic% of Nd, 0.2 atomic% of Pr, 0.8 atomic% of Dy, 8 atomic% of B, and the balance Fe. To this was added 25 wt % of the adjusting alloy powder obtained by the direct reduction diffusion method of Example 1 and blended, and then a magnet was produced under the same conditions as in Example 1. However, the amount of O _{2 in} the blended alloy powder obtained in Comparative Example 1 was 28.
Since the content was as high as 00 ppm, sufficient sintering was not performed, and the magnetic properties were low as shown in Table 1.

Comparative Example 2 Nd metal (purity 98%) 111 g Dy metal (purity 98%) 10.5 g Electrolytic iron (purity 99%) 383 g was melted with high frequency in an Ar atmosphere to obtain Nd9. 7 atom%, Pr 0.1 atom
%, Dy 0.8 atomic%, after obtaining an alloy ingot consisting of the balance Fe, pulverization was attempted with a jaw crusher disk mill, etc., but it is extremely difficult to pulverize, and the powder after pulverization is easily oxidized,
The oxygen content was 2000 ppm. A magnet was prepared in the same manner as in Example 1 by adding and mixing 25 wt % of the adjusting alloy powder to the main phase alloy powder prepared in Example 1, and the magnetic properties are shown in Table 1.

Comparative Example 3 25% by weight of the raw material powder for adjustment prepared in Comparative Example 2 by the dissolution pulverization method with the raw material powder for main phase produced in Comparative Example 1 by the direct reduction diffusion method
After the addition and blending, a magnet was prepared in the same manner as in Example 1, and the magnetic properties are shown in Table 1.

[0029]

[Table 1]

[0030]

According to the present invention, in order to obtain a raw material powder for an R-Fe-B permanent magnet, a main phase alloy powder having a main phase of R ₂ Fe ₁₄ B phase is produced by a melting and pulverizing method. In addition, an adjustment alloy powder containing an R ₂ Fe ₁₇ phase is produced by a direct reduction diffusion method, and an R-Fe-B-based alloy powder having an R ₂ Fe ₁₄ B phase as a main phase has Nd of 60% or less of the total amount. ₂ By adding and blending the adjustment alloy powder containing the Fe ₁₇ phase, it is possible to obtain an alloy ingot that is extremely easy to grind, and to reduce the amount of the B-rich phase and the Nd-rich phase that deteriorate the magnet properties of the permanent magnet. As can be seen from the examples, it is possible to improve the performance of the magnet obtained, further reduce the oxygen content in the alloy powder, and easily provide an alloy powder having a composition according to various magnet properties. it can.

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Claims (1)

(57) [Claims] 1. R (where R is at least one of the rare earth elements containing Y) 12 to 20 atomic%, B6 to 15 atomic%, balance
Fe (except the part of Fe Co, can be substituted by one or two of Ni) and consists unavoidable impurities, the R ₂ Fe ₁₄ B phase obtained by dissolving pulverization method in the alloy powder as a main phase , R (where R is Y
At least one of the rare earth elements containing) 20 atomic% or less,
Remainder Fe (except the part of Fe Co, can be substituted by one or two of Ni) and consists unavoidable impurities, the adjusting alloy powder containing the R ₂ Fe ₁₇ phase obtained by direct reduction diffusion process Mixed powder
A method for producing a raw material powder for an R-Fe-B-based permanent magnet, wherein the raw material powder is added and blended in an amount of not more than 60 wt % of the powder.