WO2005031023A1

WO2005031023A1 - Raw material alloy for r-t-b permanent magnet and r-t-b permanent magnet

Info

Publication number: WO2005031023A1
Application number: PCT/JP2004/014580
Authority: WO
Inventors: Futoshi Kuniyoshi; Yuji Kaneko; Hiroshi Hasegawa; Shiro Sasaki
Original assignee: Neomax Co., Ltd.; Showa Denko K.K.
Priority date: 2003-09-30
Filing date: 2004-09-28
Publication date: 2005-04-07
Also published as: JP4366360B2; JPWO2005031023A1; CN1860248A

Abstract

A raw material alloy for R-T-B permanent magnet of thin-sheet form comprising an R2T14B columnar crystal and an R enriched phase (R: at least one rare earth element including Y, T: Fe or Fe and at least one transition metal element other than Fe, and B: boron or boron and carbon), wherein in the alloy structure observed on any arbitrary section including the normal direction of the thin sheet, the aspect ratio is 10 or higher and the area ratio of R enriched phase whose longitudinal direction is 90±30° against the surface of the thin sheet is 30% or higher based on all the R enriched phases existing in the alloy.

Description

Specification

Raw material alloy for R-T-B series permanent magnets and R-T-B series permanent magnets

The present invention relates to a raw material alloy for an RTB-based permanent magnet, and more particularly to a raw alloy flake for an RTB-based permanent magnet manufactured by a strip casting method. Still, the present invention relates to an R—T—B-based permanent magnet produced from the above-mentioned raw material alloy for an R-T-B-based permanent magnet. Background art

R-T-B permanent magnets, which have the largest magnetic energy product among permanent magnets, are used for HD (hard disk), MRI (magnetic resonance imaging), and various motors due to their high characteristics. ing. In recent years, in addition to the improvement of heat resistance, the demand for energy-saving lugi in the market has increased, and the ratio of motors, including automobiles, has increased.

Here, “R” in “RT—B-based permanent magnet” is mainly the one in which a part of Nd is replaced by other rare earth elements such as Pr and Dy, and Y is a rare earth element. It is at least one of the elements. “Ding” is a substitution of a part of Fe with another transition metal such as Co or Ni. "B" is boron, part of which is C Or those substituted with N. The "RT-B-based permanent magnet" is composed of "Nd_Fe-B-based magnet" or "R-Fe-B-based magnet" because its main components are Nd, Fe, and B. Collectively.

In the present specification, “RT—B permanent magnet” refers to Cu,

One or more of elements such as Al, Ti, V, Cr, Ga, Mn, Nb, Ta, Mo, W, Ca, Sn, Z It is known that magnets added in combination can be used to improve various properties such as magnetic properties.

R-T-B alloys have a main phase of R ₂ T i ₄ B phase, which is a ferromagnetic phase that contributes to the magnetizing action, and coexist with a nonmagnetic, rare earth-enriched, low melting point R-rich phase. Alloy. Since R-T-B alloys are active metals, they are generally melted in a vacuum or inert gas. In addition, in order to manufacture a sintered magnet from the manufactured R—T—B series alloy ingot by powder metallurgy, the alloy ingot is crushed to about 3 m (FSSS: measurement with a fisher subsizer). After the alloy powder is formed, it is pressed in a magnetic field. The powder compact obtained by press molding is sintered at a high temperature of about 100 ° C to 110 ° C in a sintering furnace. It is general that the sintered body produced in this way is subjected to hemp heat treatment, machining, and plating to improve corrosion resistance as necessary. The R-rich phase in R—T—B sintered magnets plays an important role as follows.

1) The melting point of the R-rich phase is low and becomes a liquid phase during sintering, contributing to the higher density of magnets and the improvement of magnetization.

2) Eliminate irregularities at grain boundaries, reduce nucleation sites in reverse magnetic domains, and increase coercive force.

3) Increase the coercive force by magnetically insulating the main phase.

Therefore, if the dispersion state of the R-rich phase in the formed magnet is poor, local sintering failure and magnetism will be reduced, so that the R-rich phase is uniformly dispersed in the formed magnet. Is important. The distribution of the R-rich phase in the RTB-based sintered magnet is greatly affected by the microstructure of the RTB-based alloy as the raw material.

A strip cast method (hereinafter abbreviated as “SC method”) has been developed as a method for producing R—T-B alloys, and is used in actual processes. In the SC method, a thin section of about 0.1 to 1 mm in thickness is produced by flowing molten metal of an alloy on a copper roll and rapidly cooling and solidifying the molten alloy. According to the SC method, since the crystal structure of the alloy is refined, it is possible to produce an RTB alloy having a structure in which the R-rich phase is finely dispersed. As described above, in the alloy manufactured by the SC method, since the internal R-rich phase is finely dispersed, the dispersibility of the R-rich phase in the magnet after pulverization and sintering is good. Thus, the magnetic properties of the magnet can be improved.

(Japanese Unexamined Patent Application Publication Nos. H5-222488 and H5-295490).

The alloy flakes produced by the SC method have excellent structural homogeneity. The homogeneity of the structure can be compared by the dispersion state of the crystal grain size and the R-rich phase. In alloy flakes produced by the SC method, chill crystals (equiaxed crystals) may be generated on the production roll side (hereinafter referred to as the 錄 -shaped surface side) of the alloy flakes, but the whole is quenched. A moderately fine and homogeneous structure obtained by solidification can be obtained.

As described above, the R-T-B alloy produced by the SC method has a finely dispersed R-rich phase and excellent structure homogeneity. As a result, the homogeneity of the R-rich phase in the final magnet is improved, and the magnetic properties can be improved. As described above, the R—T—B-based alloy ingot produced by the SC method has an excellent structure for producing a sintered magnet. However, as the properties of the magnet improve, the raw material mixture becomes more and more. There is a growing demand for advanced control of the gold structure, especially the state of the R-rich phase.

First, the present inventors studied the relationship between the structure of the manufactured R—T—B system alloy and the behavior during hydrogen cracking and fine grinding. It is important to control the dispersion state of the R-rich phase in order to control the grain size of the alloy powder uniformly. (Japanese Patent Application Laid-Open No. 2003-188806). The region in which the dispersion state of the R-rich phase formed on the side of the mold in the alloy is extremely fine (fine R-rich phase region) is finely pulverized and the pulverization stability of the alloy is reduced. In addition to reducing the particle size distribution of the powder, and found that it is necessary to reduce the fine R-rich phase area to improve the magnet properties.

According to the alloy disclosed in Japanese Patent Publication No. 2003-188680, which has a small fine R-rich phase region, it is possible to improve the pulverization stability and magnetic properties. However, reducing the fine R-rich phase region alone does not allow the full role of the R-rich phase as described above to be fully exerted, and further improving the magnetic properties of the permanent magnet by controlling the alloy structure. Is desired.

The present invention provides an R—T—B-based permanent magnet raw material alloy capable of improving magnetic properties by controlling the R-rich phase present in the alloy on a more microscopic scale. The purpose is to: Disclosure of the invention

The present inventors observed the R-rich phase present in the RTB-based alloy on a more microscopic scale, and found that there was a great relationship between the shape of the R-rich phase and the magnetic properties. Out. That is, the present invention is as follows. (1) R-T-B-based permanent magnet material alloy containing R ₂ T ₄ B columnar crystal and R-rich phase (R is at least one rare earth element containing 丫, T is F e or at least one of the transition metal elements other than Fe and Fe, and B is boron or boron and carbon), and in the alloy structure observed in any cross section including the normal direction of the thin plate, The aspect ratio of the R-rich phase whose aspect ratio is 10 or more and its major axis direction is 90 ± 30 ° to the surface of the thin plate is 3096 or more of all the R-rich phases present in the alloy. A raw material alloy for R-T-B series permanent magnets characterized by the following characteristics.

(2) The area ratio of the R-rich phase, whose aspect ratio is 90 or more and its major axis direction is 90 ± 30 ° to the surface of the thin plate, is the ratio of all R-rich phases present in the alloy. The raw material alloy for R—T—B series permanent magnets according to the above (1), wherein the content is 50% or more.

(3) The area ratio of the R-rich phase whose aspect ratio is 10 or more and its major axis direction is 90 ± 3〇 ° to the surface of the thin plate is equal to the ratio of all the R-rich phases present in the alloy. The raw material alloy for an RT-B-based permanent magnet according to the above (1), wherein the alloy is 70% or more of the total.

(4) The raw material alloy for R—T—B permanent magnet according to (1) to (3), wherein the aspect ratio is 20 or more. (5) R-T-B-based permanent magnets containing R ₂ T ₄ B columnar crystals and an R-rich phase (R is at least one rare earth element containing Y, T is Fe or at least one of the transition metal elements other than Fe and Fe, B is boron or boron and carbon) and was observed in any cross section including the normal direction of the thin plate In the alloy structure, the area ratio of the R-rich phase whose aspect ratio is 1% or more and whose major axis direction is 3% or less or 15% or more with respect to the surface of the thin plate is determined by A raw material alloy for R-T-B-based permanent magnets, characterized in that it accounts for 50% or less of all R-rich phases present in the steel.

(6) The area ratio of the R-rich phase having an aspect ratio of 1% or more and its major axis direction being 30 ° or less or 150 ° or more with respect to the sheet surface exists in the alloy. The raw material alloy for an RT—B-based permanent magnet according to the above (5), wherein the content is 3% or less of all R-rich phases.

(7) R-T-B-based permanent magnet raw alloy containing R ₂ T ₄ B columnar crystals and R-rich phase (R is at least one rare earth element containing 丫, T is F e or at least one of the transition metal elements other than Fe and Fe, and B is boron or boron and carbon), and the alloy structure observed in any cross section including the normal direction of the thin plate At

The area ratio of the R-rich phase with an aspect ratio of 1% or more and its major axis direction being 90 ± 30 ° with respect to the surface of the thin plate is found in the alloy. 3% or more of all R rich phases present, and the aspect ratio is 1% or more and the major axis direction is 30 ° or less or 150 ° or more with respect to the sheet surface R-T-B material alloy for permanent magnets, characterized in that the area ratio of the R-rich phase is 50% or less of all the R-rich phases present in the alloy.

(8) The area ratio of the R-rich phase having an aspect ratio of 1 mm or more and its major axis direction being 9 ° ± 30 ° with respect to the surface of the thin plate is equal to the ratio of all R-rich phases present in the alloy. And the area ratio of the R-rich phase whose aspect ratio is 10 ° or more and the major axis direction is 30 ° or less or 150 ° or more with respect to the surface of the thin plate, The raw material alloy for an R—T—B-based permanent magnet according to the above (1), wherein the content of the R-rich phase present in the alloy is 3% by weight or less.

(9) The raw material alloy for an RTB-based permanent magnet according to the above (1) to (8), which is produced by a strip casting method.

(10) The raw material alloy for an R—T—B system permanent magnet according to (9), wherein the average thickness is at least 0.11 171 and 0.50 mm.

(11) An R—T—B-based permanent magnet produced from the R—T—B-based alloy according to (1) to (10). Brief Description of Drawings

FIG. 1 is a diagram showing a cross-sectional structure of a rare-earth magnet alloy flake containing an agglomerated R-rich phase manufactured by a conventional SC method.

FIG. 2 is a view showing a cross-sectional structure of a rare-earth magnet alloy flake containing an R-rich phase having a higher-order dendrite manufactured by a conventional SC method.

FIG. 3 is a view showing a cross-sectional structure of a rare-earth magnet alloy flake according to the present invention.

FIG. 4 is a schematic view of a manufacturing apparatus of the strip cast method. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a raw material alloy for an RTB-based permanent magnet according to the present invention will be described with reference to the drawings.

First, refer to FIG. 1 and FIG. These figures show the cross section of a thin section of a Nd-Fe-B alloy (Nd31.5 mass%) recorded by the conventional SC method and observed by SEM (scanning electron microscope). It is an electronic image. In both figures, the left side of the drawing is the mold side of the alloy, and the right side is the free side of the alloy. When rapid solidification of the molten alloy by the SC method is performed, the molten alloy is rapidly quenched from the side of the mold and crystallized.

The white part in Fig. 1 indicates the Nd rich phase (when R is Nd, the R rich phase is called the “Nd rich phase”). There is. ). As can be seen from Fig. 1, the Nd rich phase is aggregated in a pool. On the other hand, Fig. 2 shows that in order to produce a sintered magnet from an R-TB-based alloy in which a very fine Nd-rich phase exists in a dendritic form, the R-T-B-based alloy was ground. Then, it is necessary to produce a compact by pressing. As a method of pulverizing the RTB alloy, it is preferable to first embrittle the RTB alloy by hydrogen absorption and then pulverize it finely. R-T-B alloys are coarsely crushed (crushed) by embrittlement due to hydrogen storage. In the hydrogen crushing process of this RTB-based alloy, hydrogen is absorbed from the R-rich phase, expands, becomes brittle, and becomes hydride. Therefore, in hydrogen crushing, fine cracks are introduced into the alloy along the R-rich phase or starting from the R-rich phase. In the subsequent pulverization process, a large amount of fine cracks generated by hydrogen disintegration caused the alloy to break, so that the dispersion state of the R-rich phase tended to affect the pulverization efficiency and fine powder shape. . Therefore, the present inventors observed the R-rich phase on a more microscopic scale, and found that the shape of each R-rich phase and the fine cracks formed by hydrogen disintegration are related to the magnetic properties. I found that.

From the rough pooled R-rich phase shown in Fig. 1, fine cracks are formed radially during hydrogen cracking, and at the same time, they themselves become embrittled. Therefore, during the subsequent jet milling, the R embrittled and pool-shaped R-rich phase was largely separated from the main phase. It is very finely ground. Extremely fine powder consisting of such an R-rich phase is separated by a cyclone and cannot be recovered at a high rate, which causes a fluctuation in the composition during grinding. In addition, since the fine powder composed of the R-rich phase is very active, it causes a decrease in the magnetic properties due to an increase in the oxygen concentration, necessitating the strengthening of safety measures in the process, reducing the production efficiency, and reducing the cost. Leading to a rise.

On the other hand, as shown in Fig. 2, the very fine R-rich phase existing in the form of dendrites has a small distance between adjacent fine-branched R-rich phases for general sintered magnets. It is smaller than the ground particle size. For this reason, the proportion of fine branch-shaped R-rich phases incorporated into the fine powder after jet milling increases. As described above, the R-rich phase becomes a liquid phase during sintering and contributes to sintering. For this purpose, the R-rich phase exists on the surface of each fine powder, and it is necessary to wet the fine powder during sintering. However, such an effect cannot be expected for the R-rich phase that has entered the powder, and it cannot provide a sufficient effect even if it oozes out on the surface. Causes decline.

Moreover, when very fine R Li pitch phase present dendrite Bok shape there are many, Den branching portion of the dry Bok becomes possible abundant in the interior powder, R ₂ T i ₄ the orientation of the anisotropy different Since the proportion of the phase B coexisting inside the powder is increased, the degree of orientation of the obtained permanent magnet is reduced, which causes a problem. Next, the Nd-Fe-B alloy (Nd31.5% by mass) according to the present invention manufactured by the SC method will be described with reference to Fig. 3. FIG. 3 shows a reflected electron image when a cross section of a piece of the Nd—Fe—B alloy according to the present invention was observed by SEM (scanning electron microscope).

As can be seen from Fig. 3, the Nd-rich phase in the cross-sectional photograph shows a layered (lamella-like) Nd-rich phase extending within a limited angle range centered on the thickness direction. The dominant proportion is dominant. The pool-shaped R-rich phase shown in Fig. 1 and the twig-shaped R-rich phase shown in Fig. 2 are slightly present, but their abundance is low. If an alloy having such a structure is pulverized by jet milling after hydrogen disintegration, the problems with alloys having the structures shown in FIGS. 1 and 2 may be caused by changes in composition and increases in oxygen and nitrogen concentrations. It is possible to solve problems such as lower magnetic properties, lower sintering density and lower degree of orientation. As a result, it is possible to obtain an optimal raw material alloy for R—T-B permanent magnets that can sufficiently fulfill the essential role of the R-rich phase, and use such a raw material alloy. This makes it possible to obtain an RTB permanent magnet having high magnetic properties.

It is an existing R—T—B alloy, and the structure shown in Fig. 3 partially exists. In addition, the dispersion state of the R-rich phase in the RT-B-based alloy depends on the cooling after the molten metal solidifies during the manufacturing. It is described in Japanese Patent Application Laid-Open No. H09-170555 and Japanese Patent Application Laid-Open No. H10-36949 that the cooling speed can be controlled or the heat treatment can be controlled. However, even if the existing R—T—B alloy has a partial structure as shown in Fig. 3, most of the structure as shown in Figs. The essential role of the rich phase cannot be fully demonstrated.

Hereinafter, the raw material alloy for the R—T—B permanent magnet according to the present invention will be described in detail.

(1) Strip cast method

First, with reference to FIG. 4, a description will be given of a structure of a raw material alloy for an RT—B-based permanent magnet by a strip casting method. Fig. 4 shows a schematic view of an apparatus for forming by the strip cast method.

Generally, RT-B alloys are melted in a vacuum or an inert gas atmosphere using a refractory material 1 due to their active properties. After the molten alloy is held at 130 ° C to 150 ° C for a predetermined time, the inside is water-cooled via a tundish 2 equipped with a rectification mechanism and a slag removal mechanism as necessary. It is supplied to the produced rotating roll 3 for production.

The supply speed of the molten metal and the number of rotations of the rotating rolls should be controlled appropriately according to the required thickness of the alloy. The rotating peripheral speed of the rotating roll is preferably set to about 0.5 to 3 m / s. Yes. Copper or copper alloy is suitable for the material of the manufacturing rotary roll because it has good thermal conductivity and is easily available. Depending on the material of the rotating roll and the surface condition of the roll, the metal may adhere to the surface of the rotating roll for manufacturing, causing the metal to adhere to the surface of the rotating roll. The quality of the base alloy is stable. The alloy 4 solidified on the rotating roll separates from the roll on the opposite side of the tandem tissue and is recovered in the recovery container 5. By providing a heating and cooling mechanism in this collection container, the state of the R-rich phase structure can be controlled.

When manufacturing the alloy of the present invention, cooling on a forming roll

(This is called “primary cooling”) and cooling in the collection container (this is called “secondary cooling”) needs to be set appropriately.

-The next cooling is, specifically, to set the temperature of the alloy at 60 ° to 85 ° C. when leaving the production roll.合金 It is necessary that the temperature of the alloy when leaving the casting hole be higher than the melting point of the R-rich phase. The melting point of the R-rich phase is slightly higher or lower depending on the composition, but is more than 600 ° C.場合 If the temperature of the alloy when it is separated from the forming roll is lower than the melting point of the R-rich phase, the solidification of the R-rich phase has been completed and the structure will be as shown in Fig. 2. On the other hand, when the temperature is higher than 850 ° C, the R-rich phase aggregates into a pool after the roll detaches, and the structure becomes as shown in Fig. 1.好ましい More favorable temperature of the alloy when leaving the forming roll The range is 600 ~ 8〇0 ° C. A more preferred temperature range is 64 ° C to 5 ° C. However, the preferred temperature range slightly fluctuates depending on the alloy composition.

The dispersion state and shape of the R-rich phase greatly depend on TRE (total rare earth content). For example, in an alloy with a low TRE and a small R rich phase, 錄 the amount of heat cut off on the forming roll is small, 、 the alloy temperature tends to increase when the forming roll is removed, and the R rich phase aggregates and pools. The tendency to form. On the other hand, alloys with a high TRE and a high R-rich phase have a high tendency to generate a structure having higher-order dendritic arms due to a large amount of heat cut on the 鎵 roll. Therefore, in order to keep the alloy temperature when leaving the recording roll within the above-mentioned appropriate temperature range, the alloy thickness must be reduced when the TRE is small, and thickened when the TRE is large. . Specifically, when the guideline of TRE is 30 wt% or less, the average thickness of the alloy is preferably set to 0.10 to 0.30 mm in order to increase the degree of primary cooling. More preferably, it is 0.15 to 0.27 mm. More preferably, the standard of the TRE, which is 0.20 to 0.25 mm, is 30 to 33 wt%, and the preferable average thickness of the alloy is 0.25 to 0.35 mm. More preferably, it is 0.26 to 0.32 mm. When the target of TRE is 33 wt% or more, the preferable average thickness of the alloy is from 0.2 to 0.5 mm. More preferably 0.28 ~. · It is 35 mm.

The degree of primary cooling can also be controlled by appropriately selecting the surface roughness of the mirror forming roll and controlling the heat loss from the alloy on the forming roll. This method is especially effective when the TRE is less than 33 wt% or more than 33 wt%.以上 Unnecessary heat cutting can be suppressed by increasing the surface roughness of the forming roll. When the TRE is 33 wt% or more, high heat transfer to the forming roll caused by a large amount of the R-rich phase can be appropriately suppressed by roughening the surface roughness of the forming roll. it can. Surface roughness of the guide in this case is 2 0 microns or more in ten-point mean roughness R _Z. In the case of TRE 3 〇 wt% or less, the surface roughness should be about 2 μm or less to prevent primary cooling on the roll, and excessive aggregation of the R-rich phase should be prevented. Is preferred. However, the surface roughness is affected by other factors such as the roll surface material, and is not limited to the above values.

鐽 The surface temperature of the forming roll affects the wettability of the molten alloy and the roll. If the temperature is too low, the wettability of the molten alloy and the roll tends to be poor, and there is a tendency for macroscopic nonuniformity in contact between the alloy and the alloy. When the temperature is too high, the wettability between the molten alloy and the roll is good if the temperature is too high. Tona May cause partial burn-in. The seizure of the alloy on the roll surface causes a change in heat transfer and wettability in that area, and causes a change in the alloy structure. It is difficult to generate. In addition, if the amount of seized alloy is further increased, stable operation becomes difficult, and the production efficiency is reduced. Therefore, the production roll surface temperature is suitably from 50 to 400 ° C, preferably from 100 to 300 ° C. More preferably, it is 150 to 200 ° C. The temperature of the roll surface shown here is the temperature at which the molten metal comes into contact with the roll, and it is difficult to measure it directly. It is possible to calculate from the thermocouple measurement value by touching the roll surface of the part. On the other hand, in secondary cooling, for example, a partition plate is installed in the collection container, the interval between the partition plates is set appropriately, and the inside of the partition plate is cooled with an inert gas water such as A Therefore, it is effective to control the cooling rate of the recovered alloy.In the case of manufacturing the alloy of the present invention, when the temperature of the alloy when recovered in the recovery container is 65 ° C to 700 ° C, it is preferable that the temperature be up to 600. The cooling rate is 3 to 30 ° CZ min, more preferably 3 to 20 ° CZ min.If the temperature of the alloy when collected in the collection container is 00 to 8 ° C 0 ° C, 6 ° 0 ° C C is preferred, cooling rate is 10 ~ 4〇CZ min, more preferably 1 ~ 3 o ° c min. When the temperature of the alloy when collected in the collection container is 80〇 to 85〇 C, the preferred cooling rate up to 60〇 is 20 to 5〇 CZ minutes, more preferably 3 to 5〇 CZ. Minutes. In these temperature ranges, if the temperature exceeds the upper limit, the structure shown in Fig. 2 becomes more likely. Below the lower limit, the structure shown in Fig. 1 becomes more likely.

The alloy of the present invention defines the structure, and the production method is not limited to the above method.

The thickness of the alloy flake of the present invention is preferably 0.1 mm or more and 0.5 mm or less. When the thickness of the alloy flakes is less than 0.1 mm, the solidification rate increases excessively, and the dispersion of the R-rich phase becomes too fine. If the thickness of the alloy flakes is more than 0.5 mm, problems such as a decrease in the dispersibility of the R-rich phase due to a decrease in the solidification rate are caused.

(2) R-rich phase in alloy

The present invention relates to a raw material alloy for a R-T-B-based permanent magnet in the form of a thin plate containing R ₂ Τ ₄ B columnar crystals and an R- _rich phase (R is at least one kind of rare earth element containing 丫, T is Fe or at least one of the transition metal elements other than Fe and Fe, and B is boron or boron and carbon. The R-rich phase, which has an aspect ratio of 1% or more and whose major axis direction is 90 ± 30 ° with respect to the surface of the sheet, is observed in any cross section including the normal direction of the sheet. Area ratio is determined by all R It is 30% or more of the horn phase. As a result, there is little variation in the composition during the pulverization in the sintered magnet manufacturing process, no decrease in the magnetic properties due to the increase in the oxygen and nitrogen concentrations, no decrease in the sintered density and orientation, The most suitable alloy can be obtained for R—T—B permanent magnets that can fulfill their role. Further, by using this raw material alloy, it becomes possible to obtain an RTB-based permanent magnet having high magnetic properties.

When the aspect ratio of the R-rich phase in the alloy is less than 1%, the R-rich phase is agglomerated and in the form of a pool, and when the proportion of the R-rich phase increases, it is pulverized. At the time, the composition change due to dropout of the R-rich phase and over-milling increases.

Furthermore, even if the aspect ratio is 10 or more, if the major axis direction is out of the range of 90 ± 30 ° with respect to the surface of the thin plate, the R-rich phase is more than necessary, Is likely to be The five R-rich phases can be described as higher-order dendrites in metallography, but in actual alloy structures, primary dendrites and higher-order dendrites higher than the second order are considered. Since there is a high possibility that individual differences will occur in the identification of birds, it is determined geometrically and this range is defined.

As a result, the area ratio of the R-rich phase having an aspect ratio of at least 10 and its major axis direction being 90 ± 3 ° with respect to the surface of the thin plate is reduced by all R 30% or less of the rich phase As a result, the magnetic properties are significantly reduced.

Preferably, the area ratio of the R-rich phase having an aspect ratio of at least 10 and its major axis direction being 90 ± 3 ° relative to the surface of the thin plate is equal to all R-rich phases present in the alloy. More than 50% of the phase. More preferably, the area ratio of the R-rich phase having an aspect ratio of 10 or more and its major axis direction being 9 ± 30 ° with respect to the surface of the thin plate is equal to all R-rich phases present in the alloy. It must be at least 0% of the Tsuchi phase.

More preferably, in the above alloy, the aspect ratio is 2% or more. More preferably, the above alloy has an aspect ratio of 30 or more.

Alternatively, the area ratio of the R-rich phase whose aspect ratio is 1 mm or more and the major axis direction is 30 ° or less or 150 ° or more with respect to the surface of the thin plate is reduced to all R-rich phases present in the alloy. It should be less than 50% of the phase. Even when the aspect ratio is 10 or more, the R-rich phase whose major axis direction is 30 ° or less or 15 °° or more with respect to the thin plate surface is a twig-shaped high-order dendritic arm with a small interval. It is particularly likely.

Preferably, the area ratio of the R-rich phase having an aspect ratio of not less than 10 and the major axis direction thereof being not more than 30 ° or not less than 150 ° with respect to the surface of the thin plate is all present in the alloy. This is less than 30% of the R-rich phase of the above.

Alternatively, if the aspect ratio is 1 mm or more and its major axis The area ratio of the R-rich phase, which is 90 ° 30 ° with respect to the surface of the thin plate, is 30% or more of all the R-rich phases present in the alloy, and The ratio of the area of the R rich phase whose ratio is 10 or more and its major axis direction is 30 ° or less or 150 ° or more with respect to the sheet surface is equal to all the R rich phases present in the alloy. Less than 50% of the total.

Preferably, the area ratio of the R-rich phase having an aspect ratio of at least 10 and its major axis direction being 90 ± 30 ° with respect to the surface of the thin plate is the same as that of all the R-rich phases present in the alloy. Of the R-rich phase with an aspect ratio of at least 10 and a major axis direction of 30 ° or less or “150 ° or more” with respect to the metal surface. The area ratio is less than 30% of all R-rich phases present in the alloy.

The above-mentioned R-rich phase with an aspect ratio of 10 or more, an aspect ratio of 2 or more, or an aspect ratio of 30 or more has a major axis dimension of 5% or more, preferably 10% or more of the thin plate thickness dimension. It preferably has a length.

The aspect ratio of the R-rich phase in the alloy, the angle in the major axis direction to the sheet surface, and the area ratio of such an R-rich phase are different from those of the main phase. Since the brightness is high in BEI, it is possible to analyze after distinguishing the main phase and the R-rich phase with the image analyzer. For example, randomly selected and photographed the BEI of the cross section of 10 alloy flakes at an appropriate magnification, In each of the photographs, the total area of the R-rich phase in the photograph and the total area of the R-rich phase whose major axis is within a predetermined angle range at a predetermined aspect ratio are image-analyzed. Then, the total of the total areas of the R-rich phases whose major axis directions are within a predetermined angle range at a predetermined aspect ratio determined in each photograph was calculated for each of the 10 images. By calculating the value obtained by dividing the total area of the R-rich phase in the photograph, the area ratio of the predetermined R-rich phase can be considered.

(3) R ₂ T _{1 4} B phase in alloy

The thin plate-shaped raw material alloy for RTB-based permanent magnet according to the present invention has a main phase of R ₂ Ti ₄ B phase which is a ferromagnetic phase. The R ₂ T ₄ B phase is columnar, and the R ₂ T ₄ B columnar crystal preferably has a major axis within an angle of 90 ± 30 ° with respect to the thin plate surface. The length of the long axis is preferably 30% or more, and more preferably 5% or more of the thickness of the thin plate. Further, it is preferable that the above-mentioned preferable R ₂ Tt ₄ B columnar crystal is contained in 30% or more, preferably 50% or more of R ₂ T ₁₄ B columnar crystal in the whole thin plate.

In this case, the R ₂ T i ₄ B columnar crystal refers to a column 1 in which the crystal orientations observed by a polarizing microscope using the magnetic K err effect are uniform.

Hereinafter, Examples and Comparative Examples of the present invention will be described.

(Example 1) Nd: 31.5% by mass>, B: 1.0% by mass, Co: 1.0% by mass, AI: 0.30% by mass, Cu: 0.1 Metal neodymium, ferropolon, cobalt, aluminum, copper, and iron are combined so that 0% by mass and the balance is iron, the raw materials are melted in a high-frequency melting furnace, and the molten metal is subjected to a strip casting method. To produce alloy flakes.

The diameter of the rotating roll for production is 300 mm, the material is pure copper with a thickness of 50 mm, the inside is water-cooled, the peripheral speed of the roll during production is 1. 1 mZ s, and the average thickness is 0.2. Mm alloy flakes were produced. At that time, the average roughness of the surface of the roll was 12 microns in Rz. By visual observation, the alloy was evenly placed on the ロール roll, and no seizure on the ロール roll was observed.

In addition, a thermocouple was brought into contact with the bottom of the production roll surface, and the surface temperature of the production roll during the production was measured. In addition, the amount of cooling water for the production hole and the temperature difference between the entrance and exit, and the temperature of the water discharged from the production roll were measured.From these measured values, the molten tundish was in contact with the production roll. The surface temperature of the structure roll at the location was calculated to be 1 ° C.

When the temperature of the alloy flakes from which the roll had been separated was measured by an infrared thermometer, the temperature was 3〇 ° C. In the collection container to be housed, a partition plate for cooling A “gas” was installed. A thermocouple was inserted from the side of the collection container into the alloy. When the temperature change was measured, the maximum temperature was 20 ° C, and the average cooling rate up to 60 ° C was 22 ° C. After embedding and polishing 10 pieces of the obtained alloy flakes, a reflected electron beam image (BEI) of each alloy flake was taken at a magnification of 10 × with a scanning electron microscope (SEM). When the taken pictures were taken into an image analyzer and measured, the area ratio of the R-rich phase with an aspect ratio of 10 or more and its major axis direction being 90 ± 30 ° with respect to the metal surface was found in the alloy. 80% of all R-rich phases present in In addition, the area ratio of the R-rich phase having an aspect ratio of at least 20 and its major axis direction being 90 ± 3 ° with respect to the metal surface is determined by the ratio of all R-rich phases present in the alloy. 65% of the touch phase. On the other hand, the area ratio of the R-rich phase whose aspect ratio is 10 or more and whose major axis direction is 30 ° or less or 150 ° or more with respect to the metal surface exists in the alloy. 6% of all R-rich phases.

(Comparative Example 1)

The raw materials were blended in the same composition as in Example 1, and dissolution and production by the SC method were performed in the same manner as in Example 1. However, the thickness of the 鎵 roll is 90 mm, and the average roughness of the ロール roll surface is 7 μm in Rz. The average thickness of the alloy flakes was 〇. 35 mm. Visual observation revealed that a small amount of abnormally high alloy temperature occurred on the 鐯 roll and a seizure phenomenon was observed in some parts. The surface temperature of the production roll at a position where the molten metal of the tundish was in contact with the production roll was 400 C, which was obtained in the same manner as in Example 1.

The temperature of the alloy flakes without seizure was measured by removing the roll with an infrared thermometer and found to be 820 ° C. No special cooling mechanism has been installed in the collection container that stores the alloy flakes that have been separated from the rolls. When the temperature change of the alloy was measured with a thermocouple inserted from the side of the recovery container into the inside, the maximum temperature was 810 ° C, and the average cooling rate up to 600 ° C was 6 ° CZ minutes. Ah .

The obtained alloy flakes without seizure were evaluated in the same manner as in Example 1. As a result, many of the R-rich phases aggregated to form a pool. The area fraction of one R-rich phase is 26% of all R-rich phases present in the alloy.

(Comparative Example 2)

The raw materials were blended in the same composition as in Example 1, and dissolution and production by the SC method were performed in the same manner as in Example 1. However, the thickness of the ロール roll is 25 mm, and the average roughness of the ロール roll surface is 10 microns in Rz. The average thickness of the alloy flakes was 0.22 mm. According to the visual observation, a part of the alloy on the 鐯 roll had a slightly higher temperature.

The molten tundish obtained in the same manner as in Example 1 The surface temperature of the forming roll at a position in contact with the forming roll was 80 ° C.

The average temperature of the alloy flakes measured by removing the roll with an infrared thermometer was 67 ° C. In addition, in the collection container that stores the alloy flakes that have separated from the roll, a partition plate through which water is circulated is installed. When the temperature change of the alloy was measured with a thermocouple inserted from the side of the recovery container into the inside, the maximum temperature was 660 ° C, and the average cooling rate up to 60 ° C was 35 ° C / min. there were.

The obtained alloy flakes were evaluated in the same manner as in Example 1. As a result, the R-rich phase contained a large amount of twig-like high-order dendrites, and the aspect ratio was 10 or more and its major axis direction The area ratio of the R-rich phase which is 90 ± 30 ° with respect to the metal surface was 23% of all the R-rich phases present in the alloy. On the other hand, the area ratio of the R-rich phase having an aspect ratio of 10 or more and its major axis direction being 30 ° or less or 15 °° or more with respect to the metal surface is determined by all the alloys present in the alloy. It was 54% of the R-rich phase.

Next, examples of the sintered magnet will be described.

(Example 2)

The alloy flakes obtained in Example 1 were coarsely pulverized by a known hydrogen pulverization treatment, and 0.01% of zinc stearate powder was added to the obtained coarsely pulverized powder, and the mixture was added to a rocking mixer. More After mixing in an elementary atmosphere, the mixture was finely pulverized by a jet mill apparatus. The atmosphere during the jet mill pulverization was a nitrogen atmosphere mixed with 100 ppm of oxygen. The oxygen concentration of the body was 50 の 0 ppm. The obtained powder was mixed with a cold leap embedding resin, cured, polished, and the cross section of the powder was observed by SEM-BEI to investigate the dispersion state of the R-rich phase in the powder. As a result, the R-rich phase was attached to the surface of the grains mainly composed of the main phase.

Next, the obtained powder was press-molded under a magnetic field of 1.5 T of orientation magnetic field at a pressure of 1.0 Ot / cm ² , and the compact was held at 160 ° C. for 4 hours for sintering. did. The resulting sintered body has a sintering density of at least S g Z cm ^3, which is a sufficient density. Further, this sintered body was heat-treated at 560 ° C. for 1 hour in an argon atmosphere to produce a sintered magnet.

Table 1 shows the results of measuring the magnetic properties of this sintered magnet with a BH curve tracer.

(Comparative Example 3)

The alloy flake obtained in Comparative Example 1 was ground in the same manner as in Example 2 to obtain a fine powder. At this time, the cross section of the powder was observed in the same manner as in Example 2, and most of the R-rich phase was separated from the main phase and existed as relatively small grains composed of only the R-rich phase. I confirmed that. Further, through the same molding and sintering steps as in Example 2, a sintered magnet was produced. The magnetic properties of the sintered magnet produced in Comparative Example 3 were measured with a BH cap tracer, and the results are shown in Table 1.

(Comparative Example 4)

The alloy flake obtained in Comparative Example 2 was ground in the same manner as in Example 2 to obtain fine powder. At this time, the cross section of the powder was observed in the same manner as in Example 2, and it was confirmed that the ratio of grains in which the R-rich phase was present was about 7 times that of Example 2. Further, through the same molding and sintering steps as in Example 2, a sintered magnet was produced.

Table 1 shows the results of measuring the magnetic properties of the sintered magnet produced in Comparative Example 4 using a BH force implanter.

(table 1 )

As shown in Table 1, the density of Comparative Example 3 is lower than that of Example 2, and the magnetization and coercive force are also low in characteristics. This is due to the poor dispersion of the R-rich phase in the alloy stage, so that the R-rich phase is separated as an active fine powder in the grinding process in the cyclone of the pulverizer and the TRE tends to decrease. And the R-rich phase It is presumed that the bias did not function effectively during sintering due to the decrease in sinterability. On the other hand, Comparative Example 4 showed the same behavior, though not as much as Comparative Example 3, indicating that the contribution of the R-rich phase to sintering was insufficient. Industrial applicability

According to the raw material alloy for R—T—B permanent magnets of the present invention, the R-rich phase in the alloy can be utilized to the utmost extent. Also exhibit excellent magnet properties. In other words, the R-Rich cannot fully fulfill its original role, there is little variation in composition during fine grinding in the sintered magnet manufacturing process, there is no decrease in magnetic properties due to an increase in oxygen concentration, and there is a reduction in sintering density. It has excellent effects that cannot be obtained with conventional alloys, such as a decrease in the degree of orientation and the like. Further, by using the above-mentioned alloy, an RTB-based permanent magnet having high magnetic properties can be obtained.

INDUSTRIAL APPLICABILITY The present invention can be suitably used for various kinds of electronic equipment and electric machines that require a high-performance sintered magnet.

Claims

The scope of the claims

1. R 2 T i ₄ B column Raw material alloy for R-T-B-based permanent magnet containing R-rich phase and U-dog crystal (R is at least one rare earth element containing 丫) , Τ is Fe or at least one of the transition metal elements other than Fe and Fe, and B is porone or porone and carbon),

In the alloy structure observed in an arbitrary cross section including the normal direction of the thin plate, the aspect ratio is 10 or more and the major axis direction is 9 ° ± 30 ° with respect to the surface of the thin plate. A raw material alloy for R—T—B-based permanent magnets, wherein the area ratio of the h phase is 30% or more of all R rich phases present in the alloy.

2. The area ratio of the R-rich phase whose aspect ratio is more than 10 and its major axis direction is 90 ± 3〇 ° with respect to the surface of the thin plate is the same as that of all the R-rich phases present in the alloy. The raw material alloy for RT—B-based permanent magnets according to claim 1, which is 50% or more.

3. The area ratio of the R-rich phase, whose aspect specific force is 10 or more and its major axis direction is 90 ± 3 〇 ° to the surface of the thin plate, is the ratio of all R-rich phases present in the alloy. The raw material alloy for R—T—B permanent magnets according to claim 1, wherein the content is 7% or more.

4. The raw material alloy for an RT—B-based permanent magnet according to any one of claims 1 to 3, wherein an aspect ratio is 20 or more.

5. R ₂ Ti ₄ B columnar crystal and R-rich phase

R—T-B material alloy for permanent magnets (R is at least one rare earth element containing Y, T is Fe or at least one of Fe and transition metal elements other than Fe, B Is boron or boron and carbon)

In the alloy structure observed at an arbitrary cross section including the normal direction of the thin plate, the aspect ratio is 10 or more and the major axis direction is 30 ° or less or 150 ° with respect to the thin plate surface. The raw material alloy for R-II type permanent magnets, wherein the area ratio of the R-rich phase is 50% or less of all the R-rich phases present in the alloy.

6. The area ratio of the R-rich phase, whose aspect ratio is 10 or more and its major axis direction is 30 ° or less or 15 ° or more with respect to the thin plate surface, exists in the alloy. The raw material alloy for an R—Choichii type permanent magnet according to claim 5, wherein the alloy content is 3% or less of all the R rich phases to be formed. R 2 Τ1 ₄ R Raw material alloy for columnar crystals and R-rich phase for R -—- based permanent magnets (R is rare earth containing Υ) At least one kind of element, T is Fe or at least one kind of transition metal element other than Fe and Fe, and B is boron or boron and carbon),

In the alloy structure observed in an arbitrary cross section including the normal direction of the thin plate, the R-rich phase having an aspect ratio of 1% or more and the major axis direction of which is 90 ± 3 ° with respect to the surface of the thin plate. Area ratio of all R-rich phases present in the alloy is 30% or more, and the aspect ratio is 10 or more and its major axis direction is 30 ° or less or 150 ° to the thin plate surface. The raw material alloy for R-T-B system permanent magnets, in which the area ratio of the R-rich phase is not less than 50% of all the R-rich phases present in the alloy is 50% or less.

8. The area ratio of the R-rich phase having an aspect ratio of 10 or more and its major axis direction being 9 ± 30 ° to the surface of the thin plate is equal to the total area of the R-rich phase present in the alloy. Of the R-rich phase whose aspect ratio is 1% or more and whose major axis direction is 3 ° or less or 150 ° or more with respect to the surface of the thin plate. The raw material alloy for an R-II-III-based permanent magnet according to claim 7, wherein the raw material alloy accounts for 30% or less of all R-rich phases present in the alloy.

9. R—— 一 Τ 系永永 according to any one of claims 1 to 8, characterized by being manufactured by a strip casting method. Raw material alloy for magnets.

10. The raw material alloy for an RT—B-based permanent magnet according to claim 9, wherein the average thickness is 〇.10 mm or more and 〇.50 mm or less.

11. An RT—B-based permanent magnet produced from the raw material alloy for an RT—B-based permanent magnet according to any one of claims 1 to 10.