KR20180038745A - Manufacturing method of high performance rare earth magnet - Google Patents

Abstract

The present invention provides a method for manufacturing a rare earth magnet which includes the steps of: preparing rare earth magnet powder containing R, Fe, and B as constituent components; mixing a heavy rare earth compound which essentially includes heavy rare earth hydride and further includes any one or more of heavy rare earth oxide and heavy rare earth fluoride, with the rare earth magnet powder; performing the magnetic field formation on the mixed powder; and sintering and diffusing the heavy rare earth at the same time. Accordingly, the present invention can improve the coercive force and the thermal stability of the magnet.

Description

TECHNICAL FIELD [0001] The present invention relates to a high-performance rare-earth sintered magnet,

The present invention relates to a method for manufacturing a high-performance rare-earth sintered magnet in which the coercive force is increased while suppressing a decrease in the residual magnetic flux density of the sintered magnet body.

Nd-Fe-B based permanent magnets are increasingly used because of their excellent magnetic properties. Recently, there has been a growing demand for Nd-Fe-B type magnets, particularly small or large magnets, in accordance with the ever-simplifying, high performance, and energy saving of light-weighted, high performance and energy saving of electronic devices including hard disk drives, CD players, DVD players, High-performance sintered magnets of thin Nd-Fe-B type sintered magnets are required.

As an index of the performance of the magnet, there are the residual magnetic flux density and the magnitude of the coercive force. The increase in the residual magnetic flux density of the Nd-Fe-B sintered magnet is achieved by increasing the volume ratio of the Nd2Fe14B compound and improving the crystal orientation, and various processes have been improved to date. With regard to the increase of coercive force, there are various approaches such as finer grain size, use of a composition alloy which increases the amount of Nd, or addition of an effective element, while the most common method at present is Dy or Tb Nd is replaced with a part of Nd. By substituting these elements for Nd of the Nd2Fe14B compound, the anisotropic magnetic field of the compound is increased and the coercive force is also increased. On the other hand, substitution by Dy or Tb reduces saturation magnetization of the compound. Therefore, if the coercive force is increased only by the above method, the decrease of the residual magnetic flux density can not be avoided.

In the Nd-Fe-B magnet, the magnitude of the external magnetic field generated by the nuclei of the inverse magnetic poles at the crystal grain interface becomes coercive force. The structure of the grain boundary interface strongly influences the nucleation of the spinel structure. The disorder of the crystal structure in the vicinity of the interface leads to the disorder of the magnetic structure and promotes the generation of the inverse tool. Generally, it is said that the magnetic structure from the crystal interface to the depth of about 5 nm contributes to the increase of the coercive force.

On the other hand, coercive force can be increased while reducing the residual magnetic flux density by increasing the anisotropic magnetic field only in the vicinity of the interface by concentrating a small amount of Dy or Tb only in the vicinity of the interface of the crystal grains, and the Nd2Fe14B compound composition alloy and the alloy containing Dy or Tb Is separately manufactured and then mixed and sintered. In this method, alloys rich in Dy or Tb become liquid during sintering and are distributed to surround the Nd2Fe14B compound. As a result, Nd and Dy or Tb are substituted only in the vicinity of the grain boundary of the compound, thereby effectively increasing the coercive force while suppressing the decrease of the residual magnetic flux density.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems,

The object of the present invention is to provide a rare earth magnet manufacturing method capable of improving the coercive force and thermal stability of a magnet while reducing the amount of heavy rare earths used.

In addition, a rare earth magnet containing a heavy rare earth hydride is mixed with a rare earth magnet powder, sintering and heat treatment are simultaneously carried out, and a rare earth magnet is uniformly distributed on the surface of the magnet and on the grain boundaries of the magnet, And a method thereof.

As means for achieving the above object,

The present invention provides a method for producing a rare earth magnet powder, comprising the steps of: preparing a rare earth magnet powder containing R, Fe, B as a component; Mixing a rare earth metal compound, which contains a heavy rare earth metal hydride, a heavy rare earth metal hydride hydride, a heavy rare earth hydride, a heavy rare earth oxide, and a heavy rare earth fluoride, with the rare earth magnet powder; Magnetic field shaping the mixed powder; And performing sintering and heavy rare earth diffusion at the same time.

Further, the heavy rare earth oxide is a rare earth oxide selected from at least one of Dy and Tb, and the heavy rare earth fluoride is at least one of Dy and Tb, and is a rare earth magnet.

A method for manufacturing a rare-earth magnet according to an embodiment of the present invention includes a heavy rare earth hydride and at least one of a heavy rare earth oxide and a heavy rare earth fluoride is mixed with a rare earth magnet powder to form a magnetic field Sintering and heat treatment are performed at the same time so that the heavy rare earth is uniformly distributed on the surface of the magnet and the grain surface of the magnet so that the magnetic performance is stable and the coercive force and thermal stability of the magnet can be improved while using a small amount of heavy rare earth.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it is needless to say that the present invention is not limited to these embodiments and can be modified into various forms.

Wherever certain parts of the specification are referred to as "comprising ", the description does not exclude other parts and may include other parts, unless specifically stated otherwise. Also, when a portion such as a layer, a film, an area, a plate, or the like is referred to as being "above" another portion, this includes not only the case directly above another portion but also the case where another portion is located in the middle. When a portion of a layer, film, region, plate, or the like is referred to as being "directly on" another portion, it means that no other portion is located in the middle.

A method of manufacturing a rare-earth magnet according to an embodiment of the present invention includes the steps of preparing a rare-earth magnet powder containing R, Fe, and B as a constituent component, mixing a rare earth metal compound containing a rare-earth hydride with the rare earth magnet powder , Subjecting the mixed powder to magnetic field shaping, and performing sintering and heavy rare earth diffusion at the same time. And optionally post-annealing after sintering and diffusion.

Each step will be described in detail below.

(1) Step of preparing rare earth magnet powder

In the rare earth magnet powder containing R, Fe and B as constituent components, R may be selected from one or more rare earth elements including Y and Sc, Or two or more species can be selected. Specific examples of M include Al, Ga, Cu, Ti, W, Pt, Au, Cr, Ni, Co, Ta and Ag. The rare earth magnet powder is not limited, but Nb-Fe-B sintered magnet powder can be used.

The composition of the rare earth magnet powder is not limited, but R is in the range of 27 to 36 wt%, M is in the range of 0 to 5 wt%, B is in the range of 0 to 2 wt%, and the balance Fe.

In one embodiment, the alloy of the above composition may be dissolved in a vacuum induction heating method and made into an alloy using a strip casting method. In order to improve the grindability of the gut of these alloys, hydrogen treatment and dehydrogenation treatment are carried out at a temperature ranging from room temperature to 600 ° C., and then grinding is carried out using a pulverizing method such as a jute mill, an atit tamil ball mill, It can be produced as a uniform and fine powder. It is preferable to carry out the step of producing the powder of 1 to 10 mu m from the gut as the alloy in a nitrogen or inert gas atmosphere in order to prevent oxygen from being contaminated and deteriorating the magnetic properties.

(2) mixing the rare earth compound with the rare earth magnet powder

The heavy rare earth compound includes a heavy rare earth hydride. As the rare earth metal, at least one of Dy and Tb may be selected, and Ho may further be included. Further, at least one of the oxide of heavy rare earth and the fluoride of heavy rare earth may be further included. The ratio of the heavy rare earth hydride to the total weight of the heavy rare earth compound is in the range of 50 to 100% by weight.

The rare earth compound powder is mixed with the rare earth magnet powder, and the content of the rare earth compound in the total content of the rare earth magnet powder and the heavy rare earth compound is in the range of 1 to 4 wt%, as shown in Examples described later.

As an example of the mixing method, it is possible to uniformly knead the mixture for 0.5 to 5 hours using a three-dimensional powder kneader after weighing the mixing ratio. For uniform kneading of the rare earth powder and the heavy rare earth compound powder, it is preferable to adjust the particle size of the heavy rare earth compound powder in the range of 10 nm to 50 탆. This mixing process is preferably performed in a nitrogen or inert gas atmosphere in order to prevent oxygen from being contaminated and deteriorating magnetic properties.

(3) Step of forming magnetic field

The magnetic powder is formed using the mixed powder. As an example thereof, a kneaded powder is filled in a mold, a direct current magnetic field is applied by electromagnets located on the left and right sides of the mold, the kneaded powder is oriented, and compression molding is performed by upper / can do. The magnetic field forming process is preferably performed in a nitrogen or inert gas atmosphere in order to prevent oxygen from being contaminated and deteriorating magnetic properties.

(4) Sintering and heavy rare earth diffusion step

When the magnetic field shaping is completed, sintering of the formed body and heavy rare earth diffusion are simultaneously performed. In the sintering and heavy rare earth diffusion steps, the heat treatment temperature and heating rate are very important. As shown in the following experimental example, it is preferable to perform the hardening and heavy rare earth diffusion at a temperature within the range of 900 to 1100 占 폚, and the temperature raising rate at 700 占 폚 or higher is preferably controlled within the range of 0.5 to 15 占 폚 / min.

As an example, a compact obtained by magnetic field molding is charged into a sintering furnace and sufficiently maintained at a temperature of 400 DEG C or lower in a vacuum atmosphere to completely remove the remaining impurity organic matter. The temperature is further raised to 900 to 1100 DEG C and maintained for 1 to 4 hours, It is possible to complete the heavy rare earth diffusion simultaneously with the densification. In the sintering and heavy rare earth metal diffusion step, the atmosphere is preferably performed in an inert atmosphere such as vacuum and argon, and at a temperature of 700 ° C or higher, the temperature raising rate is controlled to 0.1 to 10 ° C / min., Preferably 0.5 to 15 ° C / It is preferable to control so that the middle rare earth can be uniformly diffused at the interface of the crystal grains.

Optionally, the sintered body having completed sintering and diffusion may be stabilized by heat treatment in the range of 400 to 900 占 폚 for 1 to 4 hours, and then the rare earth magnet can be manufactured by processing to a predetermined size.

The rare-earth magnet manufactured by this method can uniformly distribute the heavy rare earth to the surface of the magnet and the grain boundary surface of the magnet so that the magnetic performance is stable and the coercive force and the thermal stability of the magnet can be improved while using a small amount of heavy rare earth. By using rare-earth hydrides, the problems due to the influx of impurities can be minimized.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

The alloy having a composition of 32 wt% R-66 wt% Fe-1 wt% M-1 wt% B (where R = rare earth element, M = 3d metal) which does not contain heavy rare earth is dissolved by a vacuum induction heating method, And the alloy was made into a base material.

In order to improve the crushability of the produced gut, the hydrogen was absorbed at a hydrogen atmosphere and at room temperature, and then subjected to vacuum and removal of hydrogen at 600 ° C. Thereafter, the powder was homogenized by a grinding method using a jet mill technique Min. At this time, in order to prevent the oxygen from being contaminated and deteriorate in the magnetic properties, the process for producing the alloy from the gut to the fine powder was performed in a nitrogen or inert gas atmosphere.

The weight of the ground rare earth powder: Dy-H or Tb-H was adjusted so that the ratio of the rare earth compound powder was in the range of 95 to 99.5: 5 to 0.5 wt%, and then homogeneously kneaded for 2 hours using a three-dimensional powder kneader. At this time, the heavy rare earth compound powder size used in the kneading used was 1 mu m.

Using the kneaded powder, magnetic field molding was carried out as follows. The kneaded powders were filled in a mold, and a direct current magnetic field was applied by electromagnets located on the left and right sides of the mold to orient the kneaded powder, and at the same time, compression molding was carried out by upper and lower punches to produce a molded article.

The kneading of the rare earth powder and the heavy rare earth compound powder and the magnetic field forming process were carried out in a nitrogen or inert gas atmosphere in order to prevent oxygen from being contaminated and deteriorate magnetic properties.

The compact obtained by the magnetic field molding was charged into a sintering furnace and sufficiently held at a temperature of 400 DEG C or lower in a vacuum atmosphere to completely remove the remaining impure organic matter. The temperature was further raised to 1020 DEG C and maintained for 2 hours to complete sintering densification and heavy rare earth diffusion Respectively. The sintering and medium rare earth diffusion steps were carried out in a vacuum and argon atmosphere, and at a temperature above 700 ° C, the rate of temperature increase was 1 ° C / min. So that the heavy rare earths can be uniformly diffused at the interface of the crystal grains. After sintering, the sintered body was annealed at 500 ℃ for 2 hours, and then its size was measured to 12.5 * 12.5 * 4mm.

As described above, the components of the samples and the comparative samples according to the present invention were analyzed by wet analysis using ICP and magnetic properties were measured by measuring the respective loops while applying a maximum magnetic field of 30 kOe using a BH loop tracer The results of the analysis are shown in Table 1. Sample 1-1 was prepared without addition of heavy rare earth powder in the powder kneading process. Samples 1-2 to 11-13 were prepared by mixing Dy-H or Tb-H with 0.5 to 5 wt% of rare earth magnet powder, In the range of < RTI ID = 0.0 >

Sample Middle rare
Compound type The heavy rare earth compound ^a
(wt%) Sintering / diffusion temperature
(° C) Sintering / diffusion heating rate
(° C / min.) Middle rare earth component
(wt%) Residual magnetic flux
density
(kG) Coercivity
(kOe) 1-1 × × 1020 One 0.00 13.50 14.5 1-2 Dy-H 0.5 1020 One 0.48 13.42 15.9 1-3 Dy-H One 1020 One 0.96 13.33 17.4 1-4 Dy-H 2 1020 One 1.92 13.16 20.3 1-5 Dy-H 3 1020 One 2.88 12.99 23.1 1-6 Dy-H 4 1020 One 3.84 12.82 26.0 1-7 Dy-H 5 1020 One 4.80 12.11 27.5 1-8 Tb-H 0.5 1020 One 0.48 13.42 16.6 1-9 Tb-H One 1020 One 0.95 13.34 18.8 1-10 Tb-H 2 1020 One 1.90 13.18 23.1 1-11 Tb-H 3 1020 One 2.85 13.02 27.3 1-12 Tb-H 4 1020 One 3.80 12.85 31.6 1-13 Tb-H 5 1020 One 3.75 12.15 33.8

(a: the content of the rare earth compound in the total content of the rare earth magnet powder and the heavy rare earth compound, and the following Tables 2 to 5 are also the same)

As shown in Table 1, when the mixing ratio of the heavy rare earth compound is less than 1 wt%, the coercive force increasing effect is insignificant, and when the mixing ratio is more than 4 wt%, the residual magnetic flux density is sharply reduced.

Example 2

The same procedure as in Example 1 was conducted except that the heavy rare earth compound powder was changed as shown in Table 2 below.

Sample Middle rare
compound
Kinds The heavy rare earth compound ^a
(wt%) Sintering / diffusion
Temperature
(° C) Sintering / diffusion heating rate
(° C / min.) Residual magnetic flux
density
(kG) Coercivity
(kOe) 1-1
× × 1020 One 13.50 14.5 1-4 Dy-H 2 1020 One 13.16 20.3 2-1 Dy-F 2 1020 One 13.14 19.5 2-2 Dy-O 2 1020 One 13.20 16.1 1-10 Tb-H 2 1020 One 13.18 23.1 2-3 Tb-F 2 1020 One 13.17 22.0 2-4 Tb-O 2 1020 One 13.21 17.5

As shown in the results of Table 2, it can be confirmed that the heavy rare earth hydride has better coercive force increasing effect than the heavy rare earth fluoride or the heavy rare earth oxide.

Example 3

Except that a heavy rare earth compound powder was mixed in the same manner as in Example 1, as shown in Table 3 below.

Sample Middle rare
compound
Kinds The heavy rare earth compound ^a
(wt%) Middle rare
Powder mixing ratio
(wt%) Sintering / diffusion
Temperature
(° C) Sintering / diffusion heating rate
(° C / min.) Residual magnetic flux
density
(kG) Coercivity
(kOe) 1-1 × × × 1020 One 13.50 14.5 3-1 Dy-H: Dy-F 2 25: 75 1020 One 13.14 19.7 3-2 Dy-H: Dy-F 2 50: 50 1020 One 13.14 19.9 3-3 Dy-H: Dy-F 2 75: 25 1020 One 13.15 21.1 1-4 Dy-H 2 100 1020 One 13.16 20.3 3-4 Tb-H: Tb-F 2 25: 75 1020 One 13.17 22.4 3-5 Tb-H: Tb-F 2 50: 50 1020 One 13.17 22.7 3-6 Tb-H: Tb-F 2 75: 25 1020 One 13.17 22.9 1-10 Tb-H 2 100 1020 One 13.18 23.1

As shown in the results of Table 3, it was found that the heavy rare earth hydride was contained in the range of 50 to 100 wt% with respect to the total heavy rare earth compound.

Example 4

The same procedure was performed as in Example 1, except that sintering diffusion temperature was varied as shown in Table 4 below.

Sample Middle rare
compound
Kinds The heavy rare earth compound ^a
(wt%) Sintering / diffusion
Temperature
(° C) Sintering / diffusion heating rate
(° C / min.) Residual magnetic flux
density
(kG) Coercivity
(kOe) 1-1 × × 1020 One 13.50 14.5 4-1 Dy-H 2 880 One 10.25 3.5 4-2 Dy-H 2 900 One 11.88 11.3 4-3 Dy-H 2 980 One 13.00 19.5 4-4 Dy-H 2 1000 One 13.11 20.0 1-4 Dy-H 2 1020 One 13.16 20.3 4-5 Dy-H 2 1040 One 13.17 20.1 4-6 Dy-H 2 1060 One 13.16 20.0 4-7 Dy-H 2 1100 One 13.14 18.6 4-8 Tb-H 2 880 One 10.55 5.7 4-9 Tb-H 2 900 One 11.93 12.8 4-10 Tb-H 2 980 One 13.05 22.5 4-11 Tb-H 2 1000 One 13.12 22.9 1-9 Tb-H 2 1020 One 13.18 23.1 4-12 Tb-H 2 1040 One 13.19 23.0 4-13 Tb-H 2 1060 One 13.18 22.8 4-14 Tb-H 2 1100 One 13.16 21.4

As shown in Table 4, it can be seen that the sintering and heavy rare earth diffusion temperature is excellent in the range of 900 to 1100 ° C.

Example 5

The same procedure was performed as in Example 1, except that the heating rate was varied at a temperature of 700 ° C or more as shown in Table 5 below.

Sample Middle rare
compound
Kinds The heavy rare earth compound ^a
(wt%) Sintering / diffusion
Temperature
(° C) Sintering / diffusion heating rate
(° C / min.) Residual magnetic flux
density
(kG) Coercivity
(kOe) 1-1 × × 1020 One 13.50 14.5 5-1 Dy-H 2 1020 0.1 13.19 20.3 5-2 Dy-H 2 1020 0.5 13.19 20.3 1-4 Dy-H 2 1020 One 13.16 20.3 5-3 Dy-H 2 1020 2 13.15 20.1 5-4 Dy-H 2 1020 5 13.15 20.1 5-5 Dy-H 2 1020 10 13.14 19.8 5-6 Dy-H 2 1020 15 13.11 19.2 5-7 Dy-H 2 1020 20 13.06 18.7 5-8 Tb-H 2 1020 0.1 13.19 23.1 5-9 Tb-H 2 1020 0.5 13.19 23.1 1-9 Tb-H 2 1020 One 13.18 23.1 5-10 Tb-H 2 1020 2 13.18 22.8 5-11 Tb-H 2 1020 5 13.16 22.7 5-12 Tb-H 2 1020 10 13.15 22.5 5-13 Tb-H 2 1020 15 13.11 22.1 5-14 Tb-H 2 1020 20 13.08 21.4

As shown in Table 1, the heating rate is excellent in the range of 0.1 to 15 ° C / min, and the heating rate is preferably in the range of 0.5 to 15 ° C / min in consideration of mass productivity.

Example  6

Except that heavy rare earth hydrides and fluorine were added in the same manner as in Example 1, as shown in Table 6 below.

Sample Middle rare
compound
Kinds The heavy rare earth compound ^a
(wt%) Sintering / diffusion
Temperature
(° C) Sintering / diffusion heating rate
(° C / min.) Residual magnetic flux
density
(kG) Coercivity
(kOe) 1-1 × × 1020 One 13.50 14.5 6-1 Dy-H, Dy-F 2 1020 One 13.17 20.63 6-2 Dy-H, Tb-F 2 1020 One 13.13 23.34

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (5)

Preparing a rare earth magnet powder containing R, Fe and B as compositional components, wherein R is at least one selected from rare earth elements including Y and Sc, and M is one or two of metals More than species);
A rare earth metal hydride,
Mixing a rare earth metal compound containing at least one of a heavy rare earth oxide and a heavy rare earth fluoride with the rare earth magnet powder;
Magnetic field shaping the mixed powder; And
Sintering and heavy rare earth diffusion at the same time.
The method according to claim 1,
Wherein the heavy rare earth oxide is an oxide of a rare earth rare earth selected from at least one of Dy and Tb.
The method according to claim 1,
Wherein the heavy rare earth fluoride is a rare earth fluoride selected from at least one of Dy and Tb.
The method according to claim 1,
Wherein the rare-earth magnet powder further contains M (metal).
The method according to claim 1,
After the sintering and the heavy rare earth metal diffusion are completed, post-heat treatment is performed in a temperature range of 400 to 600 占 폚.