JP2003183787A - Principal phase-based alloy for rare earth magnet, manufacturing method therefor, mixed powder for sintered rare earth magnet, and rare earth magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a principal phase-based alloy containing a small quantity of formed α-Fe, by substituting Pr for Nd, which is advantageous for the cost, and improves an anisotropic magnetic field, in a principal phase-based alloy for a rare earth magnet consisting of an R-T-B alloy, which is used in a two- alloys method. <P>SOLUTION: This method for manufacturing the principal phase-based alloy is characterized by greatly restraining precipitation of α-Fe, through improving heat transfer between the molten alloy and the roller, by changing casting conditions, particularly the surface conditions of the rotation roller, when casting the principal phase-based alloy for the rare earth magnet by an SC (strip casting) method. Thereby, the method can substitute a large quantity of Pr for Nd, in the principal phase-based alloy containing little TRE (Total Rare Earth content) used for the two-alloys method. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a main phase alloy for rare earth magnets for use in a two-alloy method containing Pr, a method for producing the same, a main phase alloy for rare earth magnets containing Pr, and a grain boundary phase alloy. The present invention relates to a mixed powder for a rare earth sintered magnet and a rare earth magnet produced by mixing and.

[0002]

2. Description of the Related Art Recently, Nd-F has been used as an alloy for rare earth magnets.
The production amount of the e-B alloy is rapidly increasing due to its high characteristics, and it is used for HD (hard disk), MRI (magnetic resonance imaging), various motors, and the like. Usually, a part of Nd is replaced with another rare earth element such as Pr or Dy, or a part of Fe is replaced with another transition element such as Co or Ni. Nd-Fe-B The alloys are collectively called R-T-B type alloys including type alloys. Here, R is at least one of rare earth elements including Y. In addition, T is a transition metal that requires Fe,
Can be partially replaced with Co or Ni, and as additive elements Cu, Al, Ti, V, Cr, Mn, Nb,
You may add Ta, Mo, W, Ca, Sn, Zr, Hf etc. individually or in combination of 2 or more types. B is boron and can be partially substituted with C or N.

The R-T-B type alloy is composed of a ferromagnetic phase R ₂ T ₁₄ B phase which contributes to the magnetization action and a non-magnetic R-rich phase having a low melting point and enriched with rare earth elements. Therefore, they are generally melted and cast in a vacuum or an inert gas. Conventionally, casting has been performed by die casting, but recently, rapid solidification methods such as strip casting method and centrifugal casting method have become popular. To make a sintered magnet by powder metallurgy from the alloy mass produced by this casting, 3μ
After crushing the alloy to about m (FSSS: measured by Fisher subsieve sizer), the alloy is press-molded in a magnetic field, sintered in a sintering furnace at a high temperature of about 1000 to 1100 ° C., and then heat-treated as necessary. It is usually machined, plated for corrosion resistance and magnetized.

In the sintered magnet, the R-rich phase plays an important role as follows. 1) It has a low melting point and becomes a liquid phase at the time of sintering, which contributes to increasing the density of the magnet and thus improving the magnetization. 2) Eliminates grain boundary irregularities, reduces nucleation sites in the reverse magnetic domain, and increases coercive force. 3) Magnetically insulate the main phase to increase coercive force. Therefore, if the dispersion state of the R-rich phase is poor, local sintering failure and deterioration of magnetism will occur, so it is important that the R-rich phase is uniform.

The distribution of the R-rich phase as the final magnet is greatly influenced by the structure of the alloy ingot after casting. That is, for example, in the case of an alloy ingot cast in a mold, since the cooling rate after casting is slow, the crystal grains of the R ₂ T ₁₄ B phase often become large, and at the same time, the R-rich phase also agglomerates to form a large pool. Form and become unevenly distributed. As a result, the grain size of the crushed alloy lump becomes much finer than the crystal grain size of the R ₂ T ₁₄ B phase or the dispersed state of the R-rich phase.
Granules containing only the main phase (R ₂ T ₁₄ B phase) without rich phase and R
-The rich phase only grains will be present separately. As a result, it becomes difficult to uniformly mix the main phase and the R-rich phase.

Another problem in die casting is that γ-Fe is likely to be produced as a primary crystal because of a slow cooling rate. γ-Fe transforms into α-Fe at about 910 ° C or lower. This transformed α-Fe deteriorates the pulverization efficiency during the production of sintered magnets, and if it remains after sintering, it deteriorates the magnetic properties. Therefore, in the case of an ingot cast with a mold, α-
It becomes necessary to erase Fe.

In order to solve the above-mentioned uneven distribution of the R-rich phase and the precipitation of α-Fe, the RT cooling rate is higher than that of the die casting method.
A strip casting method (abbreviated as SC method) or a centrifugal casting method (abbreviated as CC method) has been developed as a method for casting a B-based alloy, and is used in an actual process. In the SC method, the molten metal is poured on a rotating roll for casting of copper whose inside is water cooled,
The alloy is rapidly solidified by casting a thin strip of about 0.1 to 1 mm. This casting method can suppress the precipitation of α-Fe found in the die casting method, refine the crystal structure, and produce an alloy having a structure in which the R-rich phase is finely dispersed. As described above, since the R-rich phase in the alloy ingot cast by this method is finely dispersed, the dispersibility of the R-rich phase after crushing and sintering is also good, and the magnetism of the manufactured magnet is high. The characteristics are excellent (JP-A-5-222488 and JP-A-5-295).
490 publication).

On the other hand, the CC method is one in which a molten metal is supplied into a cylindrical rotating mold and solidified while depositing the molten metal, and an intermediate solidification rate between die casting and SC method can be obtained ( Japanese Patent No. 2817624). It has been confirmed that this unique solidification condition is effective for producing a grain boundary phase alloy for the two-alloy method (Japanese Patent No. 3234741).

Further, the SC method and the CC method are superior in the homogeneity of the structure as compared with the die casting method. The homogeneity of the structure can be compared not only with the presence or absence of α-Fe precipitation but also with the crystal grain size and the dispersed state of the R-rich phase. In the alloy ingot cast by the die casting method, the structure in the vicinity of the rapidly cooled mold is composed of fine equiaxed crystal grains called chill crystals, and the R-rich phase dispersion is also relatively fine. However, in the central portion of the alloy mass that finally solidifies, the solidification rate is very slow, so the crystal grain size is very large, and the R-rich phase also becomes a pooled state in which it is partially agglomerated.

On the other hand, in the alloy flakes cast by the SC method, chill crystals may be generated on the casting rotary roll side (hereinafter referred to as the mold surface side), but as a whole, they are appropriately fine and are brought by rapid solidification. A homogeneous structure can be obtained. α-F
Since the generation of e is also suppressed, in the sintered magnet, the homogeneity of the R-rich phase of the final magnet is enhanced, and it is possible to prevent the crushing by α-Fe and the adverse effect on magnetism.

Even in the alloy cast by the CC method, the molten metal gradually accumulates and accumulates a thin solidified layer, so that a chill crystal is generated in the vicinity of the mold surface, but the free surface is formed despite its thickness. Up to nearly uniform texture can be produced. However, the conventional CC method (for example, Japanese Patent No. 2817624) is used.
In Japanese Patent Laid-Open Publication No. 2003-264, since the molten metal supply rate is relatively high, the substantial solidification rate becomes slower than that of the SC method, and the α-Fe precipitation suppression effect was intermediate between the die casting and the SC method.

In recent years, replacement of Nd with Pr has become widespread in R-T-B type alloys for rare earth magnets. This is because even if Nd is replaced with Pr, there is little change in characteristics, Pr is cheaper than Nd, and cost can be reduced. R ₂ Fe ₁₄ B compound in which R is Nd and R is P
Comparing the case of r, the saturation magnetization at room temperature is higher in Nd by about 4%, but conversely, the anisotropic magnetic field is 5% in Pr.
It is known to be high. Further, in the case of R ₂ Fe ₁₄ B compound, R is Nd and R is Pr,
Correlation of neighboring R ₂ Fe ₁₄ B compound are almost identical, R ₂
Even if Nd of Fe ₁₄ B is replaced with Pr, there is no great change in the constituent phase, and there are few factors that reduce the magnetism in terms of texture.

[0013]

From the viewpoints of cost reduction and effective use of resources, replacement of R component from Nd to Pr is widely used in R-T-B type alloys for rare earth magnets. The ratio of Pr in R remains around 10% by mass. The reason is that Pr is chemically active as compared with Nd, so that oxidation during the manufacturing process of the magnet or after magnetization becomes a problem.

Further, in the two-alloy method, which is widely used as a method for producing high-performance magnets, the limitation on the amount of Pr added is even greater than in the one-alloy method. In the two-alloy method, R ₂ Fe which is the main phase is mainly used.
_The main phase-based alloy that supplies the ₁₄ B phase and has a composition close to that of R ₂ Fe ₁₄ B and the R-rich phase that is a grain boundary phase are mainly supplied, and TRE (Total Rare Earth c
Two types of raw material alloys, which are grain boundary phase-based alloys with a lot of ontents, are used.

In the two-alloy method, it is more convenient to add Pr to the main phase alloy. When Pr is added to the grain boundary phase alloy which originally contains a large amount of R-rich phase which is easily oxidized, it becomes more and more active. Therefore, oxidation of fine powder during and after crushing in the magnetizing step becomes remarkable, and it becomes necessary to strengthen measures to prevent deterioration of characteristics due to an increase in oxygen concentration of the magnet or to prevent oxidation. As a result, the process and equipment become complicated, which causes a cost increase. However, when Pr is added to the main phase alloy, Pr is mainly added to the R ₂ Fe ₁₄ B phase, which originally has no problem of corrosion resistance.
As a result, the problem of oxidation can be reduced.
Further, when Nd is replaced by Pr, the anisotropic magnetic field of the R ₂ Fe ₁₄ B phase is slightly increased, so that the fine powder is likely to be oriented during the magnetic field orientation, and it is possible to increase the orientation ratio of the magnet and increase the magnetization. is there.

As described above, it is more convenient to add Pr to the main phase alloy. However, when Nd of the main phase alloy having a low TRE is replaced with Pr, α-Fe tends to precipitate. It is considered that this is because the difference between the liquidus line where the formation of γ-Fe which is a high temperature phase starts and the peritectic temperature where the formation of the R ₂ Fe ₁₄ B phase starts is enlarged by Pr substitution. α
-Fe is difficult to be pulverized, so that productivity is reduced due to reduction in pulverization efficiency in the magnetizing process and composition change of fine powder is caused by remaining in the pulverizer without being pulverized. This will lead to a decrease.

In the SC method, the molten metal is made R by a high cooling rate.
_Since it can be supercooled to a temperature lower than the peritectic temperature at which the ₂ Fe ₁₄ B phase is formed, the precipitation of α-Fe can be suppressed. However, Nd-Fe-B is a main phase alloy composed of a ternary system.
When d is about 28.5 mass% or less, it becomes difficult to obtain a sufficient degree of supercooling, and α-Fe comes to be precipitated. Furthermore, if Nd is replaced with Pr, α-Fe will be more likely to precipitate, so it was necessary to increase the TRE of the main phase alloy in order to prevent the precipitation of α-Fe. On the other hand, in the two-alloy method, it is convenient to lower the TRE of the main phase alloy as much as possible in order to increase the mixing ratio of the grain boundary phase alloy.

It is known that increasing the B concentration is very effective in suppressing the precipitation of α-Fe. However, when the B concentration of the main phase alloy is increased, the B concentration of the grain boundary phase alloy must be lowered in order to keep the B concentration of the final magnet constant. In addition, addition of Co and heavy rare earth elements to the main phase alloy is also effective in suppressing the precipitation of α-Fe, but the method by adjusting these compositions reduces the degree of freedom in the composition design of the alloy for magnets. However, there is a great possibility that the optimal composition combination cannot be achieved even by the two-alloy method.

Further, since Co has an excellent effect of improving the corrosion resistance, it is more convenient to add it to the grain boundary phase system alloy (Kus.
unoki et al. T. IEEE Japan,
Vol. 113-A, No. 12,1993,849-
853). It has also been confirmed that the addition of heavy rare earth elements to grain boundary phase alloys is more effective in increasing the coercive force (Ito et al., Journal of the Japan Institute of Metals, Vol. 59, No. 1 (19).
95) 103-107).

Therefore, an object of the present invention is to provide a main phase alloy for rare earth magnets for use in a two-alloy method comprising an RTB type alloy in order to prevent precipitation of α-Fe. Nd was replaced by Pr, which is advantageous in terms of cost and improves the anisotropic magnetic field, without increasing the TRE and without adjusting the composition by adding B, Co or the like.
It is to provide a main phase alloy that produces a small amount of Fe.

[0021]

That is, the present invention includes (1) 26 to 30% by mass of R (R is at least one kind of rare earth element containing Y) and 0.9 to 1.1 of B. Contains by mass% and the balance is T (T is a transition metal in which Fe is essential)
In the main phase alloy for rare earth magnets for use in the two-alloy method, the R contains Pr in an amount of 5 mass% or more in the ratio of R, and α-Fe is contained in the structure of the main phase alloy. The main phase alloy for rare earth magnets, wherein the volume ratio of the region containing is 5% or less. (2) The main phase alloy for a rare earth magnet as described in (1) above, wherein the ratio of Pr in R is 15% by mass or more. (3) The main phase alloy for a rare earth magnet as described in (2) above, wherein the ratio of Pr in R is 30% by mass or more. (4) The surface roughness of at least one surface of the main phase alloy is 10 μm or more and 50 μm or less in terms of ten-point average roughness (Rz), described in (1) to (3) above. Main phase alloy for rare earth magnets. (5) The main component for a rare earth magnet as described in (4) above, wherein the surface roughness of at least one surface of the main phase alloy is 10 μm or more and 25 μm or less in terms of ten-point average roughness (Rz). Phase-based alloy. (6) The method for producing a main phase alloy for a rare earth magnet according to any one of (1) to (5), which is produced by a strip casting method. (7) The main phase alloy for rare earth magnets according to (6) above, wherein the surface roughness of the casting surface of the rotating roll for casting is 10 μm or more and 10 μm or less in terms of ten-point average roughness (Rz). Production method. (8) The main phase alloy for rare earth magnets according to the above (6), wherein the surface roughness of the casting surface of the rotating roll for casting is 10 μm or more and 50 μm or less in terms of ten-point average roughness (Rz). Production method. (9) The method for producing a main phase alloy for a rare earth magnet according to any one of (1) to (3) above, which is produced by a centrifugal casting method in which the molten metal is deposited and solidified on the inner surface of a rotating cylindrical mold. (10) The ratio of R to the main phase alloy for rare earth magnets according to the above (1) to (3) is higher than that of the main phase alloy, and R
A mixed powder for a rare earth sintered magnet, which is produced by mixing a grain boundary phase alloy having a lower Pr ratio therein than the main phase alloy. (11) The mixed powder for a rare earth sintered magnet according to the above (10), wherein the grain boundary phase-based alloy contains substantially no Pr. (12) A rare earth magnet produced by powder metallurgy from the mixed powder for rare earth sintered magnet according to the above (10) or (11). Is.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, R is obtained by the two-alloy method.
In the case of producing a rare earth magnet made of a -T-B type alloy, R
To add Pr to the alloy, it is preferable to add Pr to the main phase alloy. However, if Nd is replaced by Pr, α-Fe
Therefore, it has been conventionally required to add another element to the main phase alloy or to modify the composition of the main phase alloy. This greatly limits the degree of freedom in alloy design, which is an advantage of the two-alloy method, and has been an obstacle to the effective use of Pr in the production of rare earth magnets by the two-alloy method.

The inventors of the present invention changed the casting conditions when casting the main phase alloy for rare earth magnets by the SC method, particularly by changing the surface condition of the casting rotary roll, so that the heat transfer between the molten alloy and the roll was achieved. It was found that the precipitation of α-Fe could be greatly suppressed by improving it, and succeeded in substituting Pr substantially for Nd in the main phase alloy for the two-alloy method with less TRE.

The inventors of the present invention have found that when the deposition rate is lowered in the main phase alloy for rare earth magnets produced by the centrifugal casting method in which the molten metal is deposited and solidified on the inner surface of the rotating cylindrical mold, the deposition rate is lower than that of the conventional SC method. It was also confirmed that α-Fe was hard to precipitate. Then, using the centrifugal casting method, α-Fe
We have succeeded in producing a main phase alloy for the two-alloy method, which has a small amount of TRE and a high ratio of Pr, in which the formation of Al is greatly suppressed. here,
The centrifugal casting method is a method in which molten metal is poured into a rotating body, the molten metal is scattered by the rotation of the rotating body, and the scattered molten metal is deposited and solidified on the inner surface of a rotating cylindrical mold (hereinafter, centrifugal force-spraying centrifugal casting method). The present inventors have found that (referred to as “method”) is particularly preferable.

In addition, the present inventors prefer the rare earth magnet manufactured by the two-alloy method in which Pr is mainly added to the main phase alloy when the added amount of Pr in the final product rare earth magnet is equal. It was also confirmed that the oxidation in the magnetizing process is suppressed more than the rare earth magnet manufactured by the general one-alloy method, the process cost can be reduced, the oxygen concentration of the rare earth magnet can be lowered, and the characteristics can be improved.

TRE manufactured by the conventional SC method is 28.5.
Mass% (however, the ratio of Nd and Pr in R is half each),
FIG. 1 shows an example of a backscattered electron image obtained by observing a cross section of a main phase alloy thin piece for a rare earth magnet containing 1% by mass of B and the balance of Fe with a SEM (scanning electron microscope). In FIG. 1, the left is the mold surface side and the right is the free surface side. The surface roughness of the surface of the alloy flakes on the mold surface was a ten-point average roughness (Rz) of 3.4 μm. In FIG. 1, the white portion is the R-rich phase, which extends lamellarly in the thickness direction or forms a small pool having a directional shape such that the lamella is divided.

In the casting of a main phase alloy by the SC method, when the oxygen concentration in the atmosphere becomes high, it reacts with the rare earth element in the molten metal to form an oxide. This oxide serves as a nucleation site for α-Fe and promotes the precipitation of α-Fe. Further, when the temperature of the molten metal drops and cools near the liquidus line, α-Fe is generated in the molten metal. Further, as the cast piece becomes thicker, the solidification rate on the free surface side decreases in particular, so that α-Fe is easily generated. Therefore, in the casting by the SC method, by thoroughly controlling the oxygen concentration and the temperature of the molten metal at the time of casting, and casting the alloy flakes to a slightly thinner thickness of about 0.2 mm,
Attempts were made to prevent the formation of α-Fe. However, nevertheless, in the main phase alloy for rare earth magnets cast by the conventional SC method, α-Fe is partially precipitated on the free surface side as shown in FIG. α-Fe is a backscattered electron image shown in FIG.
The color appears darker than that of the R ₂ Fe ₁₄ B phase, which is the main phase, and is observed as black dots in FIG. 1.

Next, FIG. 2 shows a backscattered electron beam image of the alloy flakes having the same composition as in FIG. In FIG. 2, the left is the mold surface side and the right is the free surface side. The characteristic of the SC method of the present invention is that the production of α-Fe in the alloy is suppressed by controlling the surface roughness of the alloy flakes on the mold surface side. As shown in FIG. 2, α-Fe does not exist in the alloy flakes produced by the improved SC method according to the present invention, and the homogeneity of the dispersed state of the R-rich phase is good from the mold surface to the free surface. is there.

Even in the conventional SC method, a thin piece having a uniform structure without α-Fe as shown in FIG. 2 was included to some extent, but a thin piece containing α-Fe as shown in FIG. 1 was included. Was also generated at the same time. Therefore, the volume ratio of the region containing α-Fe in the structure of the main phase alloy could not be set to 5% or less. It is considered that the partial difference in the microstructure generated by the conventional SC method is caused by a change in the contact state between the roll surface and the molten metal or the alloy flakes, such as a subtle roll surface state, the molten metal supply state, and the atmosphere.

The volume fraction of the region containing α-Fe in the structure of the main phase alloy can be measured by the following method. Figure 3
Is a backscattered electron image of the same field of view as in FIG.
The area including is surrounded by a line. α-Fe precipitates in the form of particles or dendrites, but in both cases, it exists in a relatively wide range of several tens of μm or more, and the boundary of that part can be easily determined. The area ratio of the region containing α-Fe can be calculated. The area ratio in the cross section corresponds to the volume ratio in the alloy. As described above, the volume ratio of the region containing α-Fe is
In addition to the alloy composition, it is affected by the degree of contact between the rotating roll for casting and the molten metal or alloy flakes. However, the surface condition of the casting rotary roll is not completely uniform, and a subtle change in the pouring amount also affects the degree of contact between the casting rotary roll and the molten metal. Therefore, even if alloy flakes manufactured under the same conditions, α-F
The change in the volume ratio of the region including e is large even between the thin pieces and within the same thin piece. Therefore, by widening the observation field of view at a low magnification of about 100-200 times and randomly observing about 5-10 alloy flakes, the α-Fe of the entire alloy can be obtained.
It is possible to calculate the volume ratio of the region including.

The relationship between the surface roughness of the surface of the alloy flakes manufactured by the SC method on the mold surface side and the effect of suppressing the precipitation of α-Fe can be explained as follows. In order for the alloy flakes to have a smooth surface on the mold surface side, the surface of the casting rotating roll must be smooth and have good wettability with the molten alloy. In such a state, heat transfer from the molten metal to the mold is extremely good (the heat transfer coefficient is large), and the mold surface side of the alloy is rapidly cooled. As a result, rapid solidification shrinkage occurs, and the alloy peels off from the surface of the casting rotary roll and partially floats. In the raised portion, the heat transfer coefficient to the roll is extremely reduced, and the cooling thereafter becomes very slow on the contrary. It can be estimated that α-Fe precipitates on the free surface side due to such a large decrease in the solidification rate. Such a phenomenon is likely to occur when the surface roughness of the casting rotary roll is less than 5 μm.

In the method for producing a main phase alloy for rare earth magnets according to the SC method of the present invention, the surface roughness of the surface of the casting rotary roll is 10 μm or more and 100 μm or less in terms of ten-point average roughness (Rz),
The thickness is preferably 10 μm or more and 50 μm or less. When the surface roughness of the surface of the casting rotary roll is set to the above value, the molten metal of the alloy cannot enter the fine irregularities of the surface of the casting rotary roll completely because of its viscosity, resulting in a non-contact portion and heat transfer. The coefficient decreases. An excessive decrease in heat transfer causes α-Fe precipitation, but by controlling the surface roughness to the above value, α-Fe does not precipitate and the size of the heat transfer coefficient is controlled appropriately. be able to.

By providing the surface roughness of the above-mentioned size on the rotary roll for casting, excessive heat transfer at the initial stage of solidification of the molten metal can be suppressed, and as a result, shrinkage of the alloy flakes due to rapid solidification is prevented. You can Further, the surface of the casting rotary roll meshes with the irregularities of the alloy flakes, which also works effectively to prevent partial peeling of the alloy from the roll due to solidification shrinkage. As a result, it is considered that the change in the solidification rate decreased from the mold surface side where the solidification of the molten metal started to the free surface side where the solidification ended, and the generation of α-Fe in the alloy could be suppressed.

Further, if the surface roughness of the surface of the casting rotary roll is increased, the unevenness is transferred to the mold surface side of the alloy flakes to some extent, so that the surface roughness of the mold flank surface of the alloy flakes naturally increases. . In the present invention, the surface roughness of the surface of the rotary roll for casting is 10 μm or more in terms of ten-point average roughness (Rz), and
The thickness is 00 μm or less, preferably 10 μm or more and 50 μm or less. As a result, the surface roughness of at least one surface of the cast alloy is 5 μm or more and 50 μm or less, preferably 7 μm or more and 25 μm or less.

The surface roughness of the surface of the rotating roll for casting is 10
When it is larger than 0 μm, the molten metal can enter the irregularities on the contrary, the heat transfer coefficient increases again, and at the same time, the surface roughness of the produced alloy flakes on the mold surface side further increases. In such a case, although the lift of the alloy flakes can be suppressed by the large unevenness, the dispersion of the R-rich phase becomes uneven, which is not preferable.

As another method for producing a main phase alloy for rare earth magnets according to the present invention, a centrifugal casting method is used, and for example, a rotating tundish is used to scatter the molten metal to extremely reduce the molten metal supply rate. Even with an alloy having a low TRE, the production of α-Fe can be suppressed by epitaxially growing the main phase. FIG. 4 shows a backscattered electron beam image of a cross section of an alloy having the same composition as in FIGS. 1 and 2 produced by the above centrifugal casting method. In FIG. 4, the upper photograph shows the structure at 0.5 μm from the mold surface, the central photograph shows the central portion, and the lower photograph shows the structure at 0.5 μm from the free surface. From FIG. 4, the main phase alloy having the same composition as in FIGS. 1 and 2 produced by the above centrifugal casting method has no α-Fe at all from the mold surface side to the free surface side, and the R-rich phase dispersion is also very high. It can be seen that the structure is uniform.

Next, the constitution of the present invention will be described in detail below. TRE in Main Phase Alloy for Rare Earth Magnet In the present invention, TRE in main phase alloy for rare earth magnet is used.
Is 26-30% by mass. In order to increase the mixing ratio of the grain boundary phase alloy and facilitate mixing of the main phase alloy and the grain boundary phase alloy during the production of the sintered magnet by the two alloy method, the main phase system for the two alloy method is used. It is convenient that the TRE of the alloy is as low as possible. Considering that the TRE of the high-performance magnet using the R-T-B type alloy is generally about 32% by mass or less, the TRE of the main phase type alloy should be 30% by mass or less, preferably Is 29 mass% or less. On the other hand, in the stoichiometric composition of Nd ₂ Fe ₁₄ B, the lower limit is 26.
It is 7% by mass, and if it is less than this, precipitation of α-Fe will inevitably occur, so it is impossible to significantly lower TRE, and the lower limit is 26% by mass, preferably 27% by mass or more. is there.

Pr Ratio in R The present invention is characterized in that the ratio of Pr in R of the main phase alloy for rare earth magnets is at least 5% or more. Conventionally, N of R in the main phase alloy for the two-alloy method with low TRE
The substitution of d for Pr caused a problem of α-Fe precipitation. Alternatively, Pr is added to the main phase alloy after adjusting the concentrations of other components by increasing the B concentration or adding Co to reduce the tendency of α-Fe formation. However, in the improved SC method of the present invention or the centrifugal casting method capable of supplying molten metal at a low speed such that the molten metal is scattered by centrifugal force,
-Excellent effect of suppressing Fe precipitation, α-Fe even if Pr is added
Since it is hard to precipitate, the ratio of Pr in R can be set to at least 5% or more without such component adjustment. Further, the main phase alloy for rare earth magnets of the present invention is B
Since the concentration and the concentration of other components such as Co addition are not adjusted, the degree of freedom in alloy composition design is high. In order to enhance the effect of adding Pr by utilizing the characteristics of the present invention, Pr in R is added.
Is more preferably 15% by mass or more, and further preferably 30% by mass or more.

Volume Ratio of Region Containing α-Fe In the present invention, α-Fe in the structure of the main phase alloy is used.
It is characterized in that the volume ratio of the region including is 5% or less. α-Fe causes a decrease in the pulverizability of the main phase alloy and a change in the composition. If it remains in the magnet, the magnetism decreases. α
When the volume ratio of the region containing -Fe exceeds 5%, these adverse effects cannot be ignored. The main phase alloy for rare earth magnets of the present invention is produced by the above-mentioned SC method or centrifugal casting method of the present invention so that the proportion of Pr in R is 5% by mass or more, more preferably 15% by mass or more, Even if it is preferably 30% by mass or more, α-Fe in the structure of the main phase alloy
The volume ratio of the region including can be 5% or less.

Surface roughness of the alloy flakes produced by the SC method on the mold surface side In the present invention, the surface roughness of the main phase alloy flakes produced by the strip casting method is 5 μ in terms of ten-point average roughness (Rz).
m or more and 50 μm or less. As mentioned above, the surface roughness is 5
If the thickness is less than μm, the change in heat transfer between the casting roll and the alloy flakes becomes large in the course of solidification, the solidification rate of the molten metal becomes uneven, and partial α-Fe precipitation occurs. on the other hand,
When the surface roughness is 50 μm or more, the R-rich phase is not uniformly dispersed even if α-Fe does not precipitate, which is not preferable.
The surface roughness of the alloy flakes on the mold side is 7 μm or more 25
It is more preferable that the thickness is less than or equal to μm.

Here, the surface roughness means JIS B 060.
It was measured under the conditions shown in 1 "Definition and Display of Surface Roughness", and the ten-point average roughness (Rz) is also defined therein. Specifically, first, a curve (roughness curve) obtained by removing a surface waviness component longer than a predetermined wavelength with a phase compensation type high-pass filter etc. from the cut (cross-sectional curve) when cut on a plane perpendicular to the measurement surface. Ask. From the roughness curve, the reference length is extracted in the direction of the average line, and from the average line of this extracted portion, the average value of the absolute values of the altitudes (Yp) of the 5th peak from the highest peak and the lowest absolute value. The sum of the absolute value of the absolute value (Yv) of the valley bottom to the fifth from the valley bottom is called the ten-point average roughness (Rz). Regarding the measurement parameters such as the reference length, standard values are specified by the above JIS for the surface roughness. The surface roughness of the alloy flakes on the mold surface side may fluctuate greatly, and at least five flakes are measured,
The average value should be used.

(5) Strip Casting (SC) Method Here, a method for manufacturing the R-T-B type alloy for rare earth magnets by the strip casting method will be described with reference to the apparatus diagram shown in FIG. Because of their active nature, rare earth alloys are normally used in refractory crucibles 1 in a vacuum or in an inert gas atmosphere.
Is dissolved with. Molten alloy is 1350-1500 ℃
After being held for a predetermined time, it is supplied to the water-cooled casting rotary roll 3 through the tundish 2 provided with a rectifying mechanism and a slag removing mechanism as needed. The supply rate of the molten metal and the rotation speed of the roll are appropriately changed according to the desired alloy thickness. Generally, the rotation speed of the roll is about 1 to 3 m / s in terms of peripheral speed. The rotating roll for casting is
Copper or a copper alloy is suitable because of its high thermal conductivity and easy availability. Depending on the type of alloy and the surface condition of the roll, metal is likely to adhere to the surface of the casting roll. Therefore, if a cleaning device is installed as necessary, the quality of the alloy will be stable. The alloy 4 solidified on the roll separates from the roll on the opposite side of the tundish and is collected in the collection container 5. By providing a heating / cooling mechanism to this collection container, the state of the R-rich phase can be controlled (Japanese Patent Laid-Open No. 09-17005).
5, JP-A-10-36949).

(6) Centrifugal Casting Method The centrifugal casting method of the present invention, like the conventional centrifugal casting method, supplies molten metal to the inside of a cylindrical rotating mold and solidifies it while depositing the molten metal. . However, with the method of simply dropping by gravity from the hole of the conventional tundish,
It is difficult to reduce the deposition rate of the molten metal, and α-Fe is likely to precipitate in the alloy. Therefore, the method suitable for the present invention is to supply the molten metal to the rotating body, and then to spatter the molten metal into small droplets by centrifugal force to deposit the alloy on the inner wall of the mold. The speed can be increased, and the effect of suppressing the precipitation of α-Fe is greater than that of the conventional SC method (Japanese Patent Application No. 2000-26260).
5).

FIG. 6 shows an apparatus diagram of the centrifugal casting method in which the molten metal is scattered by centrifugal force and deposited on the inner wall of the mold. Because of their active nature, rare earth alloys are typically melted using a refractory crucible 6 in a vacuum or inert gas atmosphere. The molten alloy is held at 1350 to 1500 ° C. for a predetermined time and then supplied to the rotating body 8 via the runner 7. By rotating the rotating body 8, the molten metal is scattered on the inner wall of the cylindrical mold 9 and the pouring speed is controlled, so that the alloy 1 can be deposited at a desired deposition rate.
0 can be created. The shaft of the rotor 8 and the mold 9
By having an angle between the axes of the alloys, the alloy deposition surface can be spread over the entire length of the mold, which also controls the melt deposition rate.

(7) TRE and Pr Concentration of Grain Boundary Phase Alloy The main phase alloy for rare earth magnets used in the two-alloy method manufactured in the present invention is used for the rare earth magnet used in the two-alloy method prepared separately. An anisotropic magnet with high characteristics can be manufactured by mixing with a grain boundary phase-based alloy and then crushing, molding and sintering. The grain boundary phase-based alloy is more preferable than the main phase R ₂ T ₁₄ B phase.
Its TRE is higher than that of the main phase alloy because it mainly supplies the R-rich grain boundary phase. Further, the present invention is characterized in that the ratio of Pr in R of the grain boundary phase system alloy is lower than that of the main phase system alloy. As described above, in view of corrosion resistance and magnetic field orientation, it is preferable that Pr is added to the main phase alloy in a large amount and the addition amount to the grain boundary phase alloy is as low as possible. More preferably, the grain boundary phase-based alloy preferably contains substantially no Pr except for those contained as impurities in the raw material.

(8) Method for Producing Mixed Powder for Rare Earth Sintered Magnet and Rare Earth Magnet The main phase alloy and grain boundary phase alloy for the rare earth magnet according to the present invention are usually pulverized by hydrogen pulverization or fine pulverization. The steps are carried out in order, and a powder of about 3 μm (FSSS) is formed. here,
The hydrogen disintegration is divided into a hydrogen storage step as a pre-process and a dehydrogenation process as a post-process. In the hydrogen storage process, 266 hPa ~
In a hydrogen gas atmosphere with a pressure of 0.3 MPa · G, hydrogen is occluded mainly in the R-rich phase of the alloy lump, and the R-rich phase produced by this time expands the volume of the R-rich phase. , The alloy ingot itself is finely divided, or innumerable fine cracks are formed. This hydrogen storage is from room temperature to 600
It is carried out in the range of about 0 ° C, but in order to increase the volume expansion of the R-rich phase and efficiently divide it, it is preferable to increase the pressure and carry out in the range of room temperature to 100 ° C. The preferred processing time is 1 hour or more. The R-hydride produced in this hydrogen storage step is unstable in the atmosphere and is easily oxidized, so that the R-hydride is not stored in the hydrogen storage step after the hydrogen storage step.
It is preferable to perform a dehydrogenation treatment in which the temperature is maintained at about 0 to 600 ° C. and 1.33 hPa or less in vacuum. By this treatment, it is possible to change to an R-hydride that is stable in the atmosphere. The preferable processing time is 30 minutes or more. The dehydrogenation treatment can be omitted if the atmosphere is controlled to prevent oxidation in each process from hydrogen absorption to sintering.

Fine pulverization means pulverization to about 3 μm (FSSS). As a crusher for this purpose, a jet mill device is most suitable because it has good productivity and a narrow particle size distribution can be obtained. In this case, the atmosphere during pulverization is an inert gas atmosphere such as argon gas or nitrogen gas.
2% by mass or less, preferably 1% by mass or less of oxygen may be mixed in these inert gases. As a result, the pulverization efficiency is improved, and the oxygen concentration of the pulverized powder is 1000 to 10,000 ppm, and the oxidation resistance is improved. It is also possible to suppress abnormal grain growth during sintering.

The main phase alloy and the grain boundary phase alloy are blended and mixed in a desired ratio. The mixing is performed before hydrogen crushing, before fine pulverization,
Any step after pulverization is possible. If the two alloys have extremely different pulverizability, it is better to mix them after fine pulverization. However, if the difference in grindability is small, they may be mixed before hydrocracking.

During magnetic field molding of the rare earth magnet, the powder is lubricated with zinc stearate or the like to reduce the friction between the powder and the inner wall of the mold and also reduce the friction between the powders to improve the orientation. It is preferable to add an agent. The preferable addition amount is 0.01 to 1% by mass. The addition may be carried out before or after fine pulverization, but it is preferable to sufficiently mix it by using a V-type blender or the like in an inert gas atmosphere such as argon gas or nitrogen gas before molding in a magnetic field.

The powder pulverized to about 3 μm (FSSS) is press-molded in a magnetic field molding machine. The mold is manufactured by combining a magnetic material and a non-magnetic material in consideration of the magnetic field direction in the cavity. Molding pressure is 0.5-2t / cm
² is preferred. The magnetic field in the cavity during molding is 5 to 20
kOe is preferred. The atmosphere at the time of molding is preferably an inert gas atmosphere such as argon gas or nitrogen gas, but in the case of the above-mentioned powder subjected to the oxidation resistance treatment, it is also possible in the air. Molded by cold isostatic pressing (CIP: ColdIso)
Pseudo-hydrostatic press (RIP: Rubber Isosta) using static press) or rubber mold
tic Press) is also possible. CIP or R
Since the IP is hydrostatically compressed, the disorder of the orientation during molding is small, the orientation rate can be increased as compared with the die molding, and the maximum magnetic energy product can be increased.

The sintering of the molded rare earth magnet is 1000
Performed at ~ 1100 ° C. Before reaching the sintering temperature, the lubricant and hydrogen in the fine powder should be removed as much as possible. The preferable condition for removing the lubricant is 1.33 × 10 ^-2
300 in hPa vacuum or Ar reduced pressure flow atmosphere
Hold at ~ 500 ° C for 30 minutes or more. Further, a preferable condition for removing hydrogen is to hold at 700 to 900 ° C. for 30 minutes or more in a vacuum of 1.33 × 10 ⁻² hPa or less. The atmosphere during sintering is preferably an argon gas atmosphere or a vacuum atmosphere of 1.33 × 10 ^-2 hPa or less.
The holding time is preferably 1 hour or more.

After sintering, a heat treatment may be performed at 500 to 650 ° C., if necessary, in order to improve the coercive force. A preferred atmosphere is an argon gas atmosphere or a vacuum atmosphere.
The preferable holding time is 30 minutes or more.

A rare earth magnet manufactured by the two-alloy method using the Pr-containing main phase alloy of the present invention has the same P content.
The following points are considered to be superior to the rare earth magnet produced by the one-alloy method from the raw material alloy to which r is added.

When the one-alloy method is used, the composition of the raw material alloy of the rare earth magnet is almost the same as the composition of the final rare earth magnet, and is different by a slight composition variation during the process.
E is about 31-33 mass%. About 5 to 10% of R-rich phase exists in the powder of the raw material alloy. R is Nd
In the case of the base, Pr has a stronger tendency to form the R-rich phase than the R ₂ T ₁₄ B phase, and the Pr concentration in the R-rich phase becomes higher than the total addition ratio. Therefore, the active R-rich phase becomes more active and is more likely to be oxidized during or after the grinding process. The excessive increase in oxygen concentration that occurs here deteriorates the magnet characteristics. Therefore, when increasing the Pr concentration, it is necessary to further thoroughly take measures to prevent oxidation during the process, resulting in an increase in cost and a decrease in production efficiency. Also,
Even after forming the sintered magnet, if the Pr concentration in the R-rich phase is high, the R-rich phase is active like the alloy and the fine powder, so that the corrosion resistance of the magnet is reduced.

However, in the rare earth magnet manufactured by the two-alloy method of the present invention, Pr is supplied from the main phase alloy, and R is originally
_It is contained in a high concentration in the ₂ T ₁₄ B phase, and the concentration in the R rich phase is low. Due to diffusion during sintering, Pr may diffuse from the R ₂ T ₁₄ B phase to the R rich phase, and the Pr concentration in the R rich phase may increase to some extent. Even so, the increase in the Pr concentration in the R-rich phase can be suppressed and the corrosion resistance can be improved as compared with the magnet of the 1-alloy method in which the Pr concentration in the R-rich phase of the original alloy is high. Also,
Since the main phase alloy contains a high concentration of Pr in the raw material alloy, the anisotropic magnetic field of the R ₂ T ₁₄ B phase is increased, the magnetic field orientation is also improved, and the orientation ratio and magnetization of the magnet are increased. It is also possible to bring

[0056]

Example (Example 1) The alloy composition was TRE: 28.5.
Mass% (however, the ratio of Nd and Pr in R is half each),
B: 1.00% by mass, Al: 0.30% by mass, metal neodymium, metal praseodymium, ferroboron, aluminum, and iron are blended so that the balance becomes iron, and an argon gas at 1 atmospheric pressure is used using an alumina crucible. Inside, it was melted in a high-frequency melting furnace, and the molten metal was produced into strip pieces by strip casting. The diameter of the casting roll was 300 mm, the material was pure copper, the inside was water-cooled, and the surface roughness of the casting surface was adjusted to 20 μm in terms of ten-point average roughness (Rz). The peripheral speed of the roll during casting is 0.9 m / s and the average thickness is 0.26 mm.
Alloy flakes were produced.

The surface roughness of the surface of the obtained alloy flakes on the template surface was 9 μm in terms of ten-point average roughness (Rz). After embedding 10 alloy flakes and polishing, a backscattered electron beam image (BEI) was taken with a scanning electron microscope (SEM) at a magnification of 200 for each alloy flakes. When the photographed photograph was taken into an image analyzer and measured, the volume ratio of the region containing α-Fe was 1% or less.

(Example 2) An alloy having the same composition as in Example 1 was blended, high-frequency induction melting was performed using an alumina crucible in an argon gas atmosphere, and casting was performed by a centrifugal casting apparatus using a rotary tundish. It was The average deposition rate on the inner wall of the mold was 0.01 cm / sec. The mold rotation speed at this time was set so that the centrifugal force was 3 G, and about 20 G of centrifugal force was applied to the molten metal in the rotary tundish to scatter the molten metal.

The thickness of the obtained alloy flakes was 7 to 10 mm. The alloys of 7 mm, 8.5 mm, and 10 mm in thickness were sampled, embedded, and polished, and then a backscattered electron beam image (BEI) was photographed with a scanning electron microscope (SEM) at a magnification of 200 times. At that time, for each of the alloy pieces, four evenly photographed from the mold surface side to the free surface side were taken into an image analyzer and measured. The volume ratio of the region containing α-Fe was 1% or less. It was

(Comparative Example 1) An alloy having the same composition as in Example 1 was mixed, and melt casting was carried out in the same manner as in Example 1. However, the surface roughness of the surface of the casting roll is the ten-point average roughness (Rz).
Was 3.0 μm. The obtained alloy flakes were evaluated in the same manner as in Example 1. As a result, the surface roughness of the mold surface was 10 μm average roughness (Rz) of 3.4 μm, and the volume ratio of the region containing α-Fe was , 8%.

Next, an example of producing a rare earth magnet will be described. (Example 3) The main phase alloy flakes obtained in Example 1 were first hydrocracked. The conditions of the hydrogen storage step, which is a step prior to the hydrogen disintegration step, were a 100% hydrogen atmosphere and 2 atmospheric pressure for 1 hour. The temperature of the metal piece at the start of the hydrogen storage reaction is 2
It was 5 ° C. The conditions of the dehydrogenation process, which is a post process, are
It was kept at 500 ° C. for 1 hour in a vacuum of 0.133 hPa. Zinc stearate powder was added in an amount of 0.07% by mass to the powder prepared by hydrogenation, thoroughly mixed with a V-type blender in a 100% nitrogen atmosphere, and then finely pulverized with a jet mill device. The atmosphere at the time of pulverization was a nitrogen atmosphere mixed with 4000 ppm of oxygen. Then, it was thoroughly mixed again with a V-type blender in a 100% nitrogen atmosphere. The oxygen concentration of the obtained powder was 1800 ppm, and from the analysis of the carbon concentration of the powder, it was calculated that the zinc stearate powder mixed in the powder was 0.05% by mass.

The grain boundary phase system alloy is Nd: 35.0 mass%,
Dy: 20 mass%, B: 0.70 mass%, Al: 0.3
0% by mass, Co: 25.0% by mass, Cu: 1.00% by mass, with the balance being iron, metal neodymium, metal dysprosium, ferroboron, aluminum, cobalt,
Copper and iron were blended, and an alumina crucible was used to melt in an high-frequency melting furnace in an atmosphere of 1 atm of argon gas, and an alloy was produced by a centrifugal casting method. The average deposition rate on the inner wall of the mold was 0.03 cm / sec. The mold rotation speed at this time was set so that the centrifugal force was 20G. The thickness of the obtained alloy flakes was 8 to 11 mm.

The grain boundary phase-based alloy was hydrolyzed, finely pulverized and mixed in the same manner as the main phase-based alloy. The oxygen concentration of the obtained powder was 3000 ppm, and from the analysis of the carbon concentration of the powder,
The zinc stearate powder mixed with the powder is 0.05
Calculated to be% by weight.

The main phase alloy and the grain boundary phase alloy were weighed out in a weight ratio of 9: 1 and sufficiently mixed with a V-type blender. Next, the obtained mixed powder was press-molded in a transverse magnetic field molding machine in a 100% nitrogen atmosphere. Molding pressure is 1.2t /
cm ² and the magnetic field in the mold cavity is 15 kOe
And The obtained molded body was held at 500 ° C. for 1 hour in a vacuum of 1.33 × 10 ⁻⁵ hPa, and then 1.33 × 1
After holding at 800 ° C for 2 hours in a vacuum of 0 ^-5 hPa,
It was held at 1080 ° C. for 2 hours in a vacuum of 1.33 × 10 ⁻⁵ hPa for sintering. The sintered density was 7.5 g / cm ³ or more, which was a sufficiently large density. Further, this sintered body was heat-treated at 530 ° C. for 1 hour in an argon atmosphere.

Table 1 shows the results of measuring the magnet characteristics of the rare earth magnet manufactured as described above with a DC BH curve tracer. The oxygen concentrations of the main phase fine powder and the magnet are also shown in Table 1.

Example 4 The main phase alloy cast slab obtained in Example 2 was pulverized in the same manner as in Example 3 to obtain a powder. This powder was mixed with fine powder of the same grain boundary phase alloy as that produced in Example 3 in the same manner as in Example 3 to produce a rare earth magnet. Table 1 also shows the magnet characteristics of the rare earth magnet manufactured in Example 4 and the oxygen concentrations of the main phase fine powder and the magnet.

Comparative Example 2 The main phase alloy flakes produced in Comparative Example 1 were pulverized in the same manner as in Example 3 to obtain fine powder. At this time, the crushing speed in the jet mill was reduced by 10% on average as compared with the main phase alloy flakes produced in Example 1. This powder and the grain boundary phase alloy fine powder produced in Example 3 were mixed in the same manner as in Example 3 to produce a rare earth magnet. Table 1 also shows the magnet characteristics of the rare earth magnet produced in Comparative Example 2, and the oxygen concentrations of the main phase fine powder and the magnet.

[0068]

[Table 1]

As shown in Table 1, it is understood that the rare earth magnet of Comparative Example 2 has a smaller residual magnetization than those of Examples 3 and 4. It can be presumed that the cause of this is that the α-Fe was not pulverized during the jet mill and remained in the jet mill apparatus, so that the TRE of the fine powder was slightly increased.

Comparative Example 3 A rare earth magnet having the same composition as the magnet produced in Example 3 was produced by the one alloy method. The raw material alloy has a composition of TRE: 31.15 mass% (N in the R of the raw material alloy is 52.4 mass%, Pr41.2 mass% and Dy6.4 mass%), B: 0.97. mass%,
Al: 0.30% by mass, Co: 2.50% by mass, Cu:
Alloy flakes were produced by the same SC method as in Example 1 so that 0.10% by mass and the balance iron.

The flakes were pulverized in the same manner as in Example 3 to obtain fine powder, and a magnet was produced by using the fine powder alone in the same manner as in Example 3. Table 1 shows the oxygen concentration and magnet characteristics of the manufactured magnet.
Are shown together with. As a result of analyzing the magnet manufactured in Comparative Example 3, the difference in composition from the magnet manufactured in Example 3 was within the range of analysis error.

As shown in Table 1, the rare earth magnet of Comparative Example 3 has a higher oxygen concentration and a smaller residual magnetization than those of Examples 3 and 4. It can be presumed that this is due to the oxidation of fine powder in the magnet manufacturing process and the difference in orientation during magnetic field orientation.

[0073]

INDUSTRIAL APPLICABILITY The present invention provides an alloy for rare earth magnets in which α-Fe is not generated even if Nd is replaced by Pr, which is advantageous in terms of both cost and characteristics. When used as a phase-based alloy, it is extremely effective as a raw material for rare earth magnets having excellent magnet characteristics.

When a rare earth magnet is produced from the main phase alloy for rare earth magnets containing Pr of the present invention and the grain boundary phase alloy containing a small amount of Pr, Pr is supplied from the main phase alloy. It is possible to manufacture a magnet that has improved oxidation resistance during the process and corrosion resistance of the magnet, which were defects of the high Pr-added rare earth magnet, and improved magnetic field orientation.

[Brief description of drawings]

FIG. 1 is an electron micrograph of a cross section of a main phase alloy thin piece for a rare earth magnet produced by a conventional SC method.

FIG. 2 is an electron micrograph of a cross section of a main phase alloy flakes for rare earth magnets produced by the SC method of the present invention.

FIG. 3 is a cross-sectional photograph of FIG. 1 in which a region containing α-Fe is surrounded by a dotted line.

FIG. 4 is an electron micrograph of a cross section of a main phase alloy flakes for rare earth magnets produced by the centrifugal casting method of the present invention.

FIG. 5 is a diagram showing a casting device of a strip casting method (SC).

FIG. 6 is a view showing an apparatus for centrifugal casting in which molten metal is scattered by centrifugal force and deposited on the inner wall of the mold.

[Explanation of symbols]

1 refractory crucible 2 tundish 3 Casting rotating rolls 4 alloy 5 Collection container 6 Refractory crucible 7 runway 8 rotating bodies 9 molds 10 alloy

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) H01F 1/053 H01F 1/08 B 1/06 1/04 H 1/08 1/06 A

Claims (12)

[Claims] 1. R (R is at least one of rare earth elements including Y) is contained in an amount of 26 to 30% by mass, and B is included in an amount of 0.9 to 0.9.
A main phase alloy for rare earth magnets for use in a two-alloy method containing 1.1% by mass and the balance of T (T is a transition metal in which Fe is an essential element). Of 5% by mass or more and α- of the structure of the main phase alloy
A main phase alloy for rare earth magnets, characterized in that the volume ratio of the region containing Fe is 5% or less. 2. The main phase alloy for a rare earth magnet according to claim 1, wherein the ratio of Pr in R is 15% by mass or more. 3. The main phase alloy for a rare earth magnet according to claim 2, wherein the ratio of Pr in R is 30% by mass or more. 4. The surface roughness of at least one surface of the main phase alloy in terms of ten-point average roughness (Rz) is 5 μm or more and 50 μm or more.
The main phase alloy for rare earth magnets according to any one of claims 1 to 3, wherein: 5. The surface roughness of at least one surface of the main phase alloy is 10 μm or more and 25 μm in terms of ten-point average roughness (Rz).
The main phase alloy for rare earth magnets according to claim 4, wherein: 6. The method for producing a main phase alloy for a rare earth magnet according to claim 1, wherein the method is a strip casting method. 7. The main phase alloy for a rare earth magnet according to claim 6, wherein the surface roughness of the casting surface of the casting rotating roll is 10 μm or more and 100 μm or less in terms of ten-point average roughness (Rz). Manufacturing method. 8. The main phase alloy for a rare earth magnet according to claim 6, wherein the surface roughness of the casting surface of the casting rotary roll is 10 μm or more and 50 μm or less in terms of ten-point average roughness (Rz). Manufacturing method. 9. The method for producing a main phase alloy for rare earth magnets according to claim 1, wherein the molten metal is produced by a centrifugal casting method in which the molten metal is deposited and solidified on the inner surface of a rotating cylindrical mold. 10. A rare earth magnet main phase alloy according to claim 1, wherein the ratio of R is higher than that of the main phase alloy, and R
A mixed powder for a rare earth sintered magnet, which is produced by mixing a grain boundary phase alloy having a lower Pr ratio therein than the main phase alloy. 11. The mixed powder for a rare earth sintered magnet according to claim 10, wherein the grain boundary phase alloy contains substantially no Pr. 12. A rare earth magnet produced by powder metallurgy from the mixed powder for rare earth sintered magnet according to claim 10 or 11.