KR101787549B1 - MANUFACTURING METHOD OF Nd-BASED SINTERED MAGNET AND Nd-BASED SINTERED MAGNET THEREBY - Google Patents
MANUFACTURING METHOD OF Nd-BASED SINTERED MAGNET AND Nd-BASED SINTERED MAGNET THEREBY Download PDFInfo
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- KR101787549B1 KR101787549B1 KR1020150178169A KR20150178169A KR101787549B1 KR 101787549 B1 KR101787549 B1 KR 101787549B1 KR 1020150178169 A KR1020150178169 A KR 1020150178169A KR 20150178169 A KR20150178169 A KR 20150178169A KR 101787549 B1 KR101787549 B1 KR 101787549B1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0266—Moulding; Pressing
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Hard Magnetic Materials (AREA)
- Powder Metallurgy (AREA)
Abstract
The method of manufacturing an Nd-based sintered magnet according to an embodiment of the present invention includes the steps of injecting hydrogen into an alloy strip, performing a dehydrogenation process on the alloy strip, pulverizing the alloy strip to form a fine powder, And sintering the fine powder, wherein the dehydrogenating step is performed at a temperature of from 350 ° C. to 450 ° C., and the step of sintering the fine powder includes a step of raising the temperature to a first temperature, Raising the temperature to a second temperature, maintaining the second temperature, and raising the temperature to a third temperature higher than the second temperature.
Description
The present invention relates to a method of manufacturing an Nd-based sintered magnet and an Nd-based sintered magnet produced therefrom.
As a method for producing the permanent magnet, a powder sintering method is generally used. Here, in the powder sintering method, the raw material is first pulverized, and a magnet powder finely pulverized by a jet mill (dry pulverization) is produced. Thereafter, the magnet powder is put into a mold, and a magnetic field is applied from the outside to press-mold the powder into a desired shape. Then, the magnet powder in a solid shape molded into a desired shape is produced by sintering at a predetermined temperature (for example, 800 DEG C to 1150 DEG C for an Nd-Fe-B type magnet).
On the other hand, the process of crushing the raw material includes a hydrogen crushing process. The hydrogen crushing process uses a Nd-rich phase expansion outside the coarse powder to form gold on the Nd-rich phase of the magnet and then to be pulverized in the jet mill process.
A problem to be solved by the present invention is to improve the brittleness that hydrogen can be absorbed in an alloy strip in a hydrogen crushing process and then the permanent magnet can be possessed by an inadequate dehydrogenation process. That is, an effective dehydrogenation process is performed from an alloy strip to provide an Nd-based sintered magnet having reliability and improved processability.
To solve these problems, a method of manufacturing an Nd-based sintered magnet according to an embodiment of the present invention includes the steps of injecting hydrogen into an alloy strip, performing a dehydrogenation process on the alloy strip, pulverizing the alloy strip, And sintering the fine powder, wherein the dehydrogenating step is performed at a temperature of from 350 ° C. to 450 ° C., and the step of sintering the fine powder includes a step of raising the temperature to a first temperature, Raising the temperature to a second temperature higher than the first temperature, maintaining the second temperature, and raising the temperature to a third temperature higher than the second temperature.
The first temperature may be 300 to 400 degrees, the second temperature may be 450 to 550 degrees, and the third temperature may be 800 degrees or more.
The step of maintaining the second temperature may be conducted for 1 to 3 hours.
The step of raising the temperature to the first temperature and raising the temperature to the second temperature may be carried out for 2 hours or less.
The dehydrogenation process may be performed for 2 hours to 4 hours.
The step of forming the fine powder may use a jet mill.
And forming the fine powder in a magnetic field atmosphere.
The Nd-based sintered magnet according to the embodiment of the present invention can be manufactured by the above-described manufacturing method.
The fine powder may contain 10% or less of 10% or less in particle size.
The maximum energy product (BHmax) of the Nd-based sintered magnet may be 48 or more.
According to the method of manufacturing the Nd-based sintered magnet as described above, the dehydrogenation process can be sufficiently performed from the alloy strip, whereby the brittleness of the sintered magnet can be reduced and the reliability can be improved.
FIG. 1 is a graph illustrating particle size of a powder raw material according to an embodiment of the present invention.
FIG. 2 is a graph according to the particle size of the powder raw material according to the comparative example.
BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
As will be readily understood by one of ordinary skill in the art, the following embodiments may be modified in various ways within the scope and spirit of the present invention. Wherever possible, the same or similar parts are denoted using the same reference numerals in the drawings.
All terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.
Hereinafter, a method of manufacturing an Nd-based sintered magnet according to an embodiment of the present invention will be described.
The method may include the steps of providing a powder raw material for forming the Nd-based sintered magnet and sintering the pulverized powder raw material.
Specifically, the step of preparing the powder raw material for forming the Nd-based sintered magnet comprises the steps of 1) producing an alloy strip having a predetermined composition, 2) performing hydrogen implantation on the alloy strip produced, and 3) Performing a dehydrogenation treatment on the alloy strip; and 4) pulverizing the dehydrogenated alloy strip to form a powder raw material.
In the alloy strip manufacturing step, an alloy having a predetermined composition is melted in a melting furnace at a temperature of 1400 to 1550 degrees, and then rapidly cooled through a strip caster to produce an alloy strip having a thickness of approximately 0.2 to 0.4 mm.
The alloy strip according to one embodiment described herein is the same as that of a common Nd rare earth magnet. Specifically, it is preferable that the alloy contains 28 to 35 wt% of Nd (or Nd / Pr alloy), 0 to 10 wt% of Dy (or Tb or Ho), 0.9 to 1.1 wt% of B, 0.5 to 1.5 wt% of Co, And 0 to 1 wt% of other transition metals such as Fe, and others. The sum of rare earth elements including Nd is 28 to 40 wt%.
Next, in the hydrogen implantation step, a hydrogen treatment may be performed for a predetermined time (for example, about 2 hours) with a predetermined hydrogen pressure (for example, about 0.1 MPa) for the produced alloy strip.
Specifically, this hydrotreating step comprises the steps of charging a chamber with a previously prepared alloy strip to form a vacuum in the chamber, injecting hydrogen into the chamber, and introducing hydrogen into the chamber to a predetermined hydrogen treatment temperature Maintaining the hydrotreating temperature for a predetermined time after heating, and cooling the alloy strip by injecting an inert gas into the chamber. At this time, in the step of forming a vacuum in the chamber, the vacuum in the chamber is approximately 1 × 10 -3 torr, and in the step of injecting hydrogen into the chamber, hydrogen can be injected to approximately 0.1 MPa.
Since the above-described hydrogen implantation process is an exothermic reaction, the temperature of the alloy strip rises from 200 ° C to 300 ° C. In this process, the Nd rich phase in the alloy strip expands due to the reaction with hydrogen, and a large number of cracks can be generated and crushed into coarse powder.
In the step of cooling the alloy strip by injecting an inert gas into the chamber, an inert gas such as argon (Ar) is injected into the chamber to cool the alloy strip in the chamber. At this time, an inert gas is used as the refrigerant for cooling the alloy strip Is to suppress the occurrence of unnecessary chemical reactions during the cooling process.
Next, in the dehydrogenating step, the alloy strip (or ground powder) is heated to a dehydrogenating temperature preferably in the range of 350 to 450 DEG C (more preferably around 400 DEG C) in the vacuum chamber for the hydrotreated alloy strip, It is possible to remove the hydrogen absorbed in the exhaust gas.
Specifically, the dehydrogenating step comprises the steps of: forming a vacuum in the chamber; heating the chamber to a dehydrogenation temperature in the range of 350 to 450 占 폚 and dehydrogenating the dehydrogenation treatment for a predetermined time (e.g., 2 hours to 4 hours) Maintaining the temperature and injecting an inert gas into the chamber to cool the alloy strip.
In the alloy strip pulverization step, the dehydrogenated alloy strip can be pulverized into powder having an average particle size of 3 to 7 탆 to form a magnet powder. That is, the magnet powder preferably has an average particle size of 3 to 7 mu m so that the sintering step can proceed smoothly. According to this grinding step, the raw material is formed into coarse powder.
Next, a fine milling step is carried out by using a jet mill to finely pulverize the particles so as to have an average grain size of 3 to 5 mu m measured by a laser diffraction method in a nitrogen gas atmosphere.
The pulverization of the raw material powder from the alloy strip to the fine powder is intended to pulverize the raw material in grain units so as to have a high degree of orientation when oriented through the molding process in the magnetic field. The coercive force, which is one of the physical properties of the Nd-based sintered magnet, is higher as the grain size of the powder is smaller.
Next, a step of sintering the fine powder prepared through the above-described steps in a vacuum state is carried out.
The sintering of the fine powder is performed by raising the temperature to a first temperature, raising the temperature to a second temperature higher than the first temperature, maintaining the second temperature, and sintering the third temperature Lt; / RTI >
In this case, the first temperature is 300 to 400 degrees, preferably 350 degrees, the second temperature is 450 to 550 degrees, preferably 500 degrees, and the third temperature may be 800 degrees or more. Also, the step of maintaining the second temperature may be performed for 1 to 3 hours.
That is, the sintering step according to the embodiment of the present invention may include 1) a step of raising the temperature from 300 ° C to 400 ° C, 2) a step of raising the temperature from 450 ° C to 550 ° C, 3) And 4) raising the temperature to 800 < 0 > C or higher. Wherein the step of raising the temperature to the first temperature corresponding to step 1) and step 2) and raising the temperature to the second temperature may be performed for 2 hours or less.
The subsequent sintering step is a well-known process in the art, and a detailed description thereof will be omitted. Prior to this sintering step, in the case of the anisotropic magnet powder, uniaxial magnetic field molding (not shown) may be performed on the magnet powder obtained through the above-described steps under a magnetic field of a certain size (for example, 1.9 T) .
Next, a step of performing a heat treatment in a vacuum state on the sintered body (sintered magnet) obtained in the above step may be performed. In this embodiment, the heat treatment step is not performed in one step but may include a heat treatment according to a plurality of steps having different heat treatment temperatures.
Hereinafter, properties of the sintered magnet according to the examples and comparative examples of the present invention will be described. Table 1 shows the physical properties of the sintered magnet according to the embodiment of the present invention, and Tables 2 and 3 show physical properties of the sintered magnet according to the comparative example. At this time, the numerical values representing the characteristics of the magnet include the residual magnetic density (Br) as the magnitude of the magnet, the coercive force (Hcj, Hk) as the magnitude of the magnet to resist the external magnetic pole, and the magnitude of the energy There is a maximum energy potential (BHmax).
Referring to Table 1, as a result of performing the dehydrogenation process at 400 ° C. for 3 hours as in the embodiment of the present invention. Hcj was 12.7 to 12.9, Hk / Hcj was 0.89 to 0.91, and BHmax was a level of 48.7 to 49.3.
Referring to the following Table 2, it was found that Hcj and Hk / Hcj were similar to or slightly higher than those of the experimental example in Table 1, but Br and BHmax were low. That is, it indicates that the strength of the magnet is weak as the sintered magnet. Referring to Table 3, according to the comparative example, when the dehydrogenation process was performed at 550 ° C for 3 hours, Hcj was not less than 12.5, and low Hk / Hcj and BHmax were exhibited. That is, it was found that the resistance against the external magnetic field was weak as the sintered magnet.
Hereinafter, the average particle size of the powder according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a graph according to a particle size of a raw material powder according to an embodiment of the present invention, and FIG. 2 is a graph according to a particle size of a raw material powder according to a comparative example.
1 and 2, according to an embodiment of the present invention, when the dehydrogenation process temperature is 450 ° C., the powder having a particle size of 10 μm or more occupies 8.18%, whereas when the dehydrogenation process temperature is 560 ° C., It can be seen that the powder having a particle size of 10 mu m or more used as a reference of the powder accounts for 13.62%. As described above, when coarse powder is present, Hc and Hk are lowered and the maximum energy product (BHmax) is relatively lowered. Therefore, it is important to reduce the coarse powder and it is possible to reduce the amount of coarse powder according to the embodiment of the present invention Respectively.
In summary, according to the dehydrogenation process performed at a predetermined process temperature, it is possible to reduce the brittleness of the sintered magnet to improve the reliability of the magnet and to provide the raw material powder as a uniform fine powder, thereby providing an excellent sintered magnet .
It will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the following claims.
Claims (10)
Subjecting the alloy strip to a dehydrogenation process,
Pulverizing the alloy strip to form a fine powder, and
And sintering the fine powder,
The dehydrogenation process is performed at a temperature of from 350 ° C to 450 ° C,
The step of sintering the fine powder comprises:
Raising the temperature to a first temperature,
Raising the temperature to a second temperature higher than the first temperature,
Maintaining said second temperature, and
And raising the temperature to a third temperature higher than the second temperature,
Wherein the first temperature is from 300 ° C to 400 ° C, the second temperature is from 450 ° C to 550 ° C, and the third temperature is at least 800 ° C. A method of manufacturing a magnet.
Wherein the step of maintaining the second temperature is performed for 1 to 3 hours.
Wherein the step of raising the temperature to the first temperature and the step of raising the temperature to the second temperature are performed for 2 hours or less.
Wherein the dehydrogenation step is performed for 2 hours to 4 hours.
Wherein the step of forming the fine powder is a method of manufacturing a Nd-based sintered magnet using a jet mill.
And forming the fine powder in a magnetic field atmosphere.
Wherein the fine powder contains 10% or less of a particle size of 10 탆 or more.
Wherein a maximum energy product (BHmax) of the Nd-based sintered magnet is 48 or more.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101451510B1 (en) * | 2013-05-14 | 2014-10-15 | 삼성전기주식회사 | Method for preparing Nd based rare earth sintered magnet |
| KR101492449B1 (en) * | 2014-02-24 | 2015-02-11 | 선문대학교 산학협력단 | Method for manufacturing rare earth sintered magnet using pre-sintering process |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR101451510B1 (en) * | 2013-05-14 | 2014-10-15 | 삼성전기주식회사 | Method for preparing Nd based rare earth sintered magnet |
| KR101492449B1 (en) * | 2014-02-24 | 2015-02-11 | 선문대학교 산학협력단 | Method for manufacturing rare earth sintered magnet using pre-sintering process |
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