KR101804313B1 - Method Of rare earth sintered magnet - Google Patents

Abstract

A method of manufacturing a rare-earth permanent magnet according to the present invention includes a preparation step of preparing a raw material powder having a particle size range of 2 to 10 탆 and made of a rare-earth alloy containing a rare earth element and iron; A pulse current applying step of applying a pulsed current of a high magnetic field to the filled raw material powder and a step of simultaneously compressing and applying a direct current of the author after the pulse current applying step.

Description

TECHNICAL FIELD [0001] The present invention relates to a rare earth permanent magnet,

The present invention relates to a method for manufacturing a rare-earth alloy powder, which comprises charging a powder of a rare-earth alloy containing a rare earth element and iron into a mold and compression-molding the magnetic field presses located on the left and right sides of the mold while applying a pulse current and a direct current to improve the magnetic field orientation degree To a method for manufacturing a rare earth permanent magnet.

In recent years, energy-saving and environmentally-friendly green growth projects have emerged as new issues. In the automobile industry, hybrid cars, which use internal combustion engines using fossil raw materials in parallel with motors, and hydrogen, which are environmentally friendly energy sources, And a fuel cell vehicle that drives a motor is actively being studied.

Since these environmentally friendly vehicles are driven by electric energy, permanent magnet type motors and generators are inevitably employed, and in order to further improve energy efficiency in terms of magnetic materials, rare earth permanent magnets exhibiting a higher residual magnetic flux density and stable coercive force Technical demand for magnets is on the rise.

In order to achieve weight reduction and miniaturization of a motor, for example, in addition to the design change of a motor, a permanent magnet material is required to be a ferrite It is essential to replace the magnets with rare earth permanent magnets that exhibit better magnetic performance.

Theoretically, when the residual magnetic flux density of the permanent magnet is high, it is possible to generate more sensible magnetic force to the outside, which is advantageous in improving the efficiency and performance of the device in various applications such as various motors, actuators and medical instruments. The magnitude of the residual magnetic flux density increases in proportion to the degree of improvement of the saturation magnetic flux density of the main phase constituting the magnet, the degree of anisotropy of the powder or the crystal grain, or the density of the magnet.

As mentioned above, among the parameters for improving the residual magnetic flux density, when the composition of the alloy is determined in the process of manufacturing the rare earth permanent magnet, the saturation magnetic flux density of the main phase is fixed and the density of the magnet is also close to the theoretical value It is the most important parameter to improve the magnetic field orientation degree, which is anisotropic process of rare earth alloy powder or crystal grains, by improving the manufacturing process of rare earth magnets.

Generally, a rare earth permanent magnet is manufactured by melting and casting an alloy composed of rare earth-iron-boron-other metal, preparing a rare earth metal powder by a milling method such as a ball mill or a jute mill, A step of charging the powdered powder into a metal mold and simultaneously carrying out compression molding while applying a magnetic field, thereby orienting the powder in one direction, and producing a dense sintered body by subjecting the magnetic field oriented pressed compacted body to vacuum or argon .

According to the conventional magnetic field orientation technique, the rare earth powder is filled in the mold, the powder is oriented by the direct current magnetic field generated by applying a direct current to the electromagnets positioned on the left and right sides of the mold, The molded body is subjected to a manufacturing process.

On the other hand, in the above magnetic field forming process, when a magnetic field is generated using a DC power source, the current applied is generally limited to a current of several tens to several hundreds of amperes (A), so that it is difficult to generate a magnetic field strength of 2 Tesla or more. There is a technical and technical problem that the improvement of the magnetic field orientation is limited.

In order to solve the above problems, Patent Document 1 discloses a method in which particles are rotated and oriented by applying a weak field of 1 to 2 Tesla to a powder compact, and an instantaneous pulse is applied in a direction different from the application direction of the weak field, And the powder compact is pressed while being applied with a magnetic field to increase the bulk density.

In the case of the fine powder particles having a particle diameter of 2 탆 or less, since the particle diameter of the powder compact is small and it is difficult to increase the degree of orientation upon application of the magnetic field, the weak magnetic field is first applied to act as a rotation moment for orientation. This is effective in the case of fine particles having a particle diameter of 2 탆 or less.

Korean Patent Publication No. 10-2014-0052926 (published on May 07, 2014) Korean Registered Patent No. 10-0543582 (registered on January 09, 2006) Korean Registered Patent No. 10-0524827 (registered on October 21, 2005)

In order to solve the problem that the enhancement of the magnetic field orientation of the powder is limited in the present invention, instead of using only the conventional direct current magnetic field or pulsed magnetic field, a pulse current and a direct current generator are connected in series to the magnetic field press, A method of manufacturing a rare earth permanent magnet capable of improving the magnetic field orientation degree of a powder by mixing a direct current magnetic field.

More specifically, a rare earth powder is filled in a mold, a pulse current is applied to the electromagnets positioned on the left and right sides of the mold to generate a high magnetic field, thereby completely orienting the powder, and then applying a direct current The powder is subjected to compression molding at the same time while maintaining the direction of the completely oriented powder by the generated direct magnetic field so that a molded body is manufactured.

When such a magnetic field forming method is used, a high magnetic field due to a pulse current can be utilized. Therefore, it is possible to overcome the limitation due to the conventional direct current magnetic field to improve the magnetic field orientation degree of the powder and to have a high residual magnetic flux density A rare earth permanent magnet can be manufactured.

In order to accomplish the above object, the present invention provides a method of preparing a rare-earth permanent magnet, comprising the steps of preparing a raw material powder having a particle size ranging from 2 to 10 탆 comprising a rare earth element and a rare- A step of charging the raw material powder into a mold, a pulse current applying step of applying a pulse current of a high magnetic field to the filled raw material powder, and a step of applying a direct current And simultaneously performing compression molding.

The method for producing a rare-earth permanent magnet according to the present invention is characterized in that the molding granularity of the raw material powder is in the range of 1.6 to 3.0 g / cc.

The method for manufacturing a rare-earth permanent magnet according to the present invention is characterized in that the pulse magnetic field is applied 1 to 10 times in the pulse magnetic field application step.

The method for manufacturing a rare-earth permanent magnet according to the present invention is characterized in that the direction of a pulse magnetic field applied in the pulse magnetic field application step is alternately applied.

A method of manufacturing a rare-earth permanent magnet according to the present invention includes a preparation step of preparing a raw material powder having a particle size range of 2 to 10 탆 and made of a rare-earth alloy containing a rare earth element and iron; And a step of compressing and molding simultaneously with application of a pulse current of a higher magnetic field than that of the direct current after the direct current application step .

The rare earth permanent magnet according to the present invention is characterized in that the rare earth alloy comprises 27 to 36 wt% RE - 64 to 73 wt% Fe - 0 to 5 wt% TM - 0 to 2 wt% Metal) composition.

The method for manufacturing a rare-earth permanent magnet according to the present invention is characterized in that the applied magnetic field of the pulse current is 3 to 5 tesla lines.

The method for manufacturing a rare-earth permanent magnet according to the present invention is characterized in that the applied magnetic field of the direct current is 1.5 to 2 tesla lines.

After the magnetic field orientation and shaping process according to the present invention, the sintering furnace is charged with the sintering furnace and the vacuum atmosphere is maintained at a temperature of 400 ° C or lower to completely remove the remaining solvent. The sintering is then performed by raising the temperature to 1000-1100 ° C do.

After the sintering according to the present invention, heat treatment is performed in a temperature range of 400 to 900 ° C.

According to the rare earth permanent magnet manufacturing method of the present invention, the rare earth powder is filled in a metal mold, a pulse current is applied to the electromagnets located on the left and right sides of the metal mold to generate a high magnetic field to completely orient the powder, A high magnetic field due to a high magnetic field pulse current can be utilized through a process of manufacturing a molded body by simultaneously performing compression molding while maintaining the direction of the powder completely aligned by the DC magnetic field generated by applying a direct current of the author It is possible to improve the magnetic field orientation degree of the powder by overcoming the limitation due to the conventional direct magnetic field and to carry out compression molding while maintaining the direction of the powder completely aligned by the direct current magnetic field generated by applying the direct current Through the process of manufacturing the molded body, the final residual magnetic flux density It is possible to obtain a rare earth permanent magnet having a high and high quality.

1 is a composite magnetic field press of a pulse current and a direct current according to the present invention.
2A to 2E are examples of a magnetic field application pattern of a press according to the present invention.

Hereinafter, the present invention will be described in more detail. In the following, the terms "upward", "downward", "forward" and "rearward" and other directional terms are defined with reference to the states shown in the drawings.

[Manufacturing method]

[Preparation process]

As a raw material powder, a powder composed of a rare earth alloy is prepared. The rare-earth alloy is at least one selected from RE = Y, La, Ce, Pr, Nd, Dy, Tb and Sm and Fe, TM = Alloy, or RE-Fe-TM alloy, RE-Fe-B alloy, RE-Fe-TM-B alloy. More specifically, Nd-Fe-B alloy, Nd-Fe-Co alloy, Nd-Fe-Co-B alloy and the like can be given. A powder composed of a known rare earth alloy used in a rare earth sintered magnet can be used for the raw material powder.

The raw material powder may be obtained by pulverizing a melt casting ingot made of an alloy of a desired composition or a foil obtained by a rapid solidification method by a grinder such as a jute mill, an atrit mill, a ball mill, a vibrating mill or the like, Can be prepared by using an atomization method such as a Mazze method. The powder obtained by the known powder production method or the powder produced by the atomization method may be further pulverized and used. By appropriately changing the grinding conditions and the production conditions, the particle size distribution of the raw material powder and the shape of each particle constituting the powder can be adjusted. The shape of the particles is not particularly limited, but the closer to the true sphere the more easily the particles are densified and the particles are more likely to rotate due to the application of the magnetic field. By using the atomization method, powder having high sphericity can be obtained.

At this time, it is preferable that the process for producing the raw material powder from the gut, which is an alloy, is performed in a nitrogen or inert gas atmosphere in order to prevent oxygen from being contaminated and deteriorate magnetic properties.

The raw material powder is characterized in that it contains fine particles having a particle diameter of 2 to 10 mu m. The particle size of the raw material powder is a value measured by a laser diffraction particle size distribution device.

The finer the powder, the easier it is to increase the filling density. Therefore, the maximum particle diameter is more preferably 10 m or less.

A lubricant may be added to the raw material powder. When a mixture containing a lubricant is used, each particle constituting the raw material powder tends to rotate at the time of application of the magnetic field, and the orientation can be easily increased. As the lubricant, various materials and forms (liquid or solid) which do not substantially react with the raw material powder can be used. Examples of the liquid lubricant include ethanol, machine oil, silicone oil, and castor oil. Examples of the solid lubricant include metal salts such as zinc stearate, hexagonal boron nitride, and wax. The amount of the lubricant to be added is 0.01% by mass to 10% by mass with respect to 100 g of the raw material powder in the liquid lubricant, and 0.01% by mass to 5% by mass with respect to the mass of the raw material powder in the solid state lubricant.

[Mold filling process]

A mold for molding having a desired shape and size is prepared so as to obtain a powder compact having a desired shape and size. The molding die is conventionally used for manufacturing a green compact used for a sintered magnet, and typically, a die equipped with a die and upper and lower punches can be used. Alternatively, a cold isostatic press may be used.

[Alignment process]

When the raw material powder is filled in the molding die, a pulsed current is applied to the electromagnets located on the left and right sides of the molding die to generate a high magnetic field, thereby completely orienting the powder, and then, by a direct current magnetic field generated by applying a direct current The molded body is produced by compression molding at the same time while maintaining the direction of the powder that has been completely aligned.

The pulse current applied in the present invention has a higher magnetic field strength than a direct current, a shorter duration of magnetic field application for a magnetic field application duration of 0.01 to 0.1 seconds to apply a magnetic field, and a direct current has a magnetic field strength And the duration of the magnetic field applied to the magnetic field is about 5 to 20 seconds. This is characterized in that it is relatively long compared to the magnetic field application time of the pulse current.

In order to increase the magnetic field orientation degree of the raw material powder, it is essential to increase the rotational magnetic moment of the raw material powder. In order to increase the rotational magnetic moment of the raw material powder, it is effective that the intensity of the applied magnetic field is high. It is also necessary that the magnetic field application duration is kept long for the magnetic field oriented magnetic field.

In order to enhance the magnetic field orientation of the raw material powder and to increase the duration of magnetic field application to the magnetic field oriented raw material powder, a magnetic field is formed by using a pulse current and a direct current in combination.

In order to further improve the magnetic field orientation of the powder, a method of using a pulse current and a direct current in a mixed manner is as follows: (1) the filling density of the powder filled in the mold, (2) the number of times each magnetic field is repeatedly applied, Or (4) changing the combination of the magnetic field application sequence and the magnetic field shaping.

The reason why the pulsed magnetic field and the DC magnetic field are sequentially applied as described above is that it is difficult to sustain the magnetic field application time while the pulse magnetic field can generate the high magnetic field while the DC current as the sperm magnetic field can sustain the magnetic field application time On the other hand, there is a drawback that a high magnetic field can not be applied.

This is because the magnetic field can be more completely formed by orienting the permanent magnet by applying a high magnetic field, which is an advantage of the pulse magnetic field, and then applying a direct current, a sperm field, to the oriented permanent magnet.

(Pulse current application step)

In the pulse current application step, a magnetic field of 3 to 5 Tesla is applied in a state in which relatively coarse particles of 2 탆 or more, particularly 5 탆 or more can be sufficiently rotated, that is, a state in which a gap is formed between particles, (Excitation) time in the range of 0.01 to 0.1 second.

The pulse current application process may be performed 1 to 10 times. The number of times of application of the pulse current depends on the particle diameter and shape of the raw material powder. In the case where the particle size distribution of the particles constituting the raw material powder is high and the particle shape is not spherical but has crushed protrusions, it is difficult to align all the particles in the same direction by application of one magnetic field , But does not rotate sufficiently outside a part of the particles. Therefore, since only one application of the magnetic field is sufficient, the number of times of application of the magnetic field must be increased. On the other hand, when the particle size of the raw material powder is large and the particle shape is spherical, the application of the magnetic field only once may suffice.

Since the fine particles are harder to rotate than the coarse particles even when a magnetic field is applied to them, even if a plurality of magnetic fields are applied in the same direction, the particles rotated by application of the first magnetic field are, It does not substantially rotate, and this fine particle becomes in a state where it can not rotate sufficiently. Therefore, instead of applying the magnetic field many times in the same direction, at least two magnetic fields are applied in different directions. Further, the direction of the first of the two times is set to be different from the direction to be oriented. By doing so, the particles rotated by the application of the first magnetic field are rotated in a direction different from the direction in which they are originally intended to be oriented, so that they are rotated by the application of the second magnetic field. As a result, when the second magnetic field is applied, the number of rotating particles increases, that is, the size of the coarse particles existing around the fine particles, the coarse particles, and the size of the fine particles not rotated first Fine particles of the particle size of the fine particles can be collected and rotated as a group of particles, so that the fine particles can be easily rotated in a direction to orient the fine particles.

Application of two or more magnetic fields or alternating magnetic field application in the pulse magnetic field application step has an action effect of increasing the number of rotating particles upon application of the magnetic field. Since particles larger than 2 占 퐉 and particles of 5 占 퐉 or more, particularly 8 占 퐉 or more can be rotated, a relatively small magnetic field such as 1T or more and 2T or less may be used. In addition, even when a raw material powder having a large number of fine particles of 3 占 퐉 or less, for example, a fine powder substantially consisting only of fine particles, is used, since there are particles rotating by a magnetic field of 1T to 2T, A large number of particles having a large rotation angle can be obtained. The larger the rotation angle, the larger the momentum of rotation is, so that it is less likely to be influenced by friction or the like which hinders rotation. Therefore, even when a lot of fine powder of fine particles is used, the powder is oriented by a plurality of excitations alternately in different directions, so that the powder is oriented by one excitation or by a plurality of excitations in the same direction A higher degree of orientation can be obtained than in the case of

The application of the magnetic field in the pulse magnetic field application step includes a magnet capable of applying a magnetic field of 3 to 5 tesla, specifically, a superconducting magnet having a superconducting coil such as a copper wire coil, a superconducting coil Superconducting magnets can be used.

(DC current application step)

The direct current application process is a process for more completely forming a magnetic field oriented in a molded product (hereinafter, referred to as a precompact) that has undergone a pulse current application process, and a magnetic field is applied in a direction to be oriented in the pulse current application process do.

In the DC current application process, a magnetic field of 1.5 to 2 tesla is applied in a magnetic field application (excitation) time of 5 to 20 seconds. With such a DC current application process, the raw material powder is uniformly filled and compressed in a filling density range of 1.6 to 3.0 g / cc.

The bulk density is defined as the apparent density immediately before the raw powder is pressed and compressed (the mass of the raw powder charged in the molding die / the volume of the molding region before compression / compression in the molding die) The apparent density after compression [the mass of the raw material powder filled in the molding die / the volume of the molding region after compression and compression (= the volume of the powder compact) in the molding die].

The magnitude of the pressing pressure at the time of molding can be appropriately selected depending on the filling density, for example, 0.5 ton / cm 2 to 1.5 ton / cm 2. As will be described later, also in the case of pressurizing and compressing by dividing into multiple layers, the pressing pressure at the time of molding may be selected depending on the filling density and the like.

[Sintered body]

The molded body for a magnet according to the present invention 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 solvent and further sintered at a temperature of 1000 DEG C to 1100 DEG C and a holding time of 0.5 hour ~ 3 hours, atmosphere: vacuum, argon and the like. After the sintering, a heat treatment (for example, an aging treatment) for adjusting the magnet characteristics can be appropriately performed. The heat treatment conditions include temperature: 500 to 800 占 폚, holding time: 1 to 10 hours, atmosphere: vacuum, argon, and the like. The obtained sintered body can be suitably used for a rare earth sintered magnet, typically a permanent magnet.

Hereinafter, more specific embodiments of the present invention will be described with reference to test examples.

As shown in Fig. 1, the pulse current supply device and the DC current supply device were disposed coaxially, and the molding die was disposed on the inner periphery of the pulse current supply device and the DC current supply device. The forming metal mold has a columnar lower punch inserted through a metal mold having a through hole and an upper punch disposed opposite to the lower punch and pressing and compressing the raw powder together with the lower punch. A molding space is formed by a mold die and a lower punch, the raw material powder is filled in the molding space, and the raw material powder is pressurized and compressed by the upper punch and the lower punch. At this time, by appropriately energizing each of the pulse current supply device and the DC current supply device, a magnetic field can be formed and a magnetic field is applied to the formed body in the molding space.

Each of the prepared raw material powders was charged into a molding die (molding space: diameter 10 mm), and a pulse current was applied. While applying a direct current, the pressure was adjusted so that the packing density was 1.6 or more and 3.0 or less of the molding density, · Compress.

[Example 1]

In this test, the alloy is composed of an alloy of 32 wt% RE - 66 wt% Fe - 1 wt% TM - 1 wt% B (where RE = rare earth element and TM = 3d transition metal) In order to improve the grindability of the gut, which is a manufactured alloy, hydrogen was absorbed at a hydrogen atmosphere and at room temperature, followed by removal of hydrogen at a vacuum and at 600 ° C. , And a homogeneous and fine powder having a particle size of 3.5 μm was prepared by a pulverizing method using a jet mill technique. 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 pulverized rare-earth powder was uniformly filled in the mold at a filling density of 1.8 to 2.6 g / cc, and a pulse current of 5 tesla magnetic field was applied to the electromagnets located on the left and right of the mold for 0.02 seconds to orient the powder in the magnetic field direction , Followed by direct current: 2 Tesla magnetic field for 15 seconds while simultaneously performing compression molding to produce a molded body. The obtained molded article was sintered, and the orientation and magnetic properties of the obtained sintered body were examined.

The compact obtained by the magnetic field forming technique by the pulsed magnetic field + DC magnetic field mixing method was 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 solvent. The temperature was further raised to 1060 DEG C for 2 hours The sintering densification was completed. The sintered sintered body was made of magnet by heat treatment at 500 ℃ for 2 hours.

The magnetic characteristics of the sample and the comparative sample according to the present invention were obtained by measuring the respective loops while applying a maximum magnetic field of 30 kOe using a B-H loop tracer. The results are shown in Table 1.

In the case of Examples 1-1-2 to 1-5-2 (total of 5 times), the case where the DC current was applied after applying the pulse current once and the case of Comparative Examples 1-1-1 to 1-5-1 (5 times in total), and the filling density was tested by increasing the packing density by 0.2 g / cc from 1.8 to 2.6 g / cc.

As a result of the test, the case where the pulse current and the DC current were sequentially applied was improved by about 0.13-0.3 kG than the residual magnetic flux density of the comparative example, and the residual magnetic flux density was about 1 % ~ 2.3%.

Magnetic properties change with filling density of powder in mixed magnetic field forming technology Sample Filling density
(g / cc) Applied magnetic field type Number of pulses applied Pulsed magnetic field application direction Residual magnetic flux density
(kG) 1-1-1 (comparative example) 1.8 direct current 13.18 1-1-2 (Example) 1.8 Pulse + direct current One N 13.31 1-2-1 (comparative example) 2.0 direct current 13.25 1-2-2 (Example) 2.0 Pulse + direct current One N 13.38 1-3-1 (comparative example) 2.2 direct current 13.30 1-3-2 (Example) 2.2 Pulse + direct current One N 13.45 1-4-1 (comparative example) 2.4 direct current 13.25 1-4-2 (Example) 2.4 Pulse + direct current One N 13.52 1-5-1 (comparative example) 2.6 direct current 13.17 1-5-2 (Example) 2.6 Pulse + direct current One N 13.47

[Example 2]

In this test, an alloy having a composition of 32 wt% RE - 66 wt% Fe - 1 wt% TM - 1 wt% B (where RE = rare earth element and TM = 3d transition metal) was dissolved by a vacuum induction heating method, To prepare alloy niobates.

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 pulverized rare-earth powder was uniformly filled into a mold at a filling density of 2.4 g / cc, and a pulse current of 5 tesla magnetic field was repeatedly applied to the electromagnets located on the left and right of the mold for 1 to 4 times for 0.02 seconds in the magnetic field direction , Followed by compression molding at the same time while applying a DC current of 2 Tesla magnetic field for 20 seconds to prepare a molded article.

The compact obtained by the magnetic field forming technique by the pulsed magnetic field + DC magnetic field mixing method was 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 solvent. The temperature was further raised to 1060 DEG C for 2 hours The sintering densification was completed. The sintered sintered body was made of magnet by heat treatment at 500 ℃ for 2 hours.

The magnetic characteristics of the sample and the comparative sample according to the present invention were obtained by measuring each loop while applying a maximum magnetic field of 30 kOe using a B-H loop tracer. The results are shown in Table 2.

In the case of Examples 2-1 to 2-4 (four times in total), a comparison was made between the case where the DC current was applied after applying the pulse current 1 to 4 times and the Comparative Example 1-4-1, and the filling density was 2.4 g / cc.

As a result of the test, it was found that the pulse current and the DC current were sequentially applied in the order of 0.27 to 0.3 kG higher than the residual magnetic flux density of the comparative example, and the residual magnetic flux density was about 2 % ~ 2.3%.

Change of magnetic properties according to the number of pulsed magnetic field application in mixed magnetic field forming technology Sample Filling density
(g / cc) Applied magnetic field type Number of pulses applied Pulsed magnetic field application direction Residual magnetic flux density
(kG) 1-4-1 (comparative example) 2.4 direct current 13.25 2-1 (Example) 2.4 Pulse + direct current One N 13.52 2-2 (Example) 2.4 Pulse + direct current 2 N-> N 13.53 2-3 (Example) 2.4 Pulse + direct current 3 N-> N-> N 13.55 2-4 (Example) 2.4 Pulse + direct current 4 N-> N-> N-> N 13.54

[Example 3]

The alloy having a composition of 32 wt% RE - 66 wt% Fe - 1 wt% TM - 1 wt% B (RE = rare earth element, TM = 3d transition metal) was dissolved by a vacuum induction heating method, .

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 pulverized rare-earth powder was uniformly filled into a mold at a filling density of 2.4 g / cc, and a pulsed current of 5 tesla magnetic field was alternately applied to the electromagnets located on the left and right sides of the mold in 0.02 sec. Followed by compression molding at the same time while applying a direct current of 2 Tesla magnetic field for 20 seconds to prepare a molded article. At this time, the direction of the direct current power was kept equal to the direction of the final pulse magnetic field.

The compact obtained by the magnetic field forming technique by the pulsed magnetic field + DC magnetic field mixing method was 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 solvent. The temperature was further raised to 1060 DEG C for 2 hours The sintering densification was completed. The sintered sintered body was made of magnet by heat treatment at 500 ℃ for 2 hours.

As described above, the magnetic characteristics of the samples and the comparative samples according to the present invention were obtained by measuring the respective loops while applying a maximum magnetic field of 30 kOe using a B-H loop tracer. The results are shown in Table 3.

In the case of Examples 3-1 to 3-3 (three times in total), a pulse current was applied four times, Example 3-1 was applied in the same direction, and then a direct current was applied. In Example 3-2, When a direct current was applied after applying a pulse current in Example 3-3, when a direct current was applied after applying a pulse current alternately in two times in the same direction as in Example 3-3, 1, and the filling density was tested on the basis of 2.4 g / cc.

As a result of the test, it was found that the alternating application of the pulse current and the direct current was improved by about 0.32-0.35 kG than the residual magnetic flux density of the comparative example when compared with the case of applying only the direct current, And 2.4% ~ 2.6%, respectively.

Change of magnetic properties according to direction of pulse magnetic field application in mixed magnetic field forming technology Sample Filling density
(g / cc) Applied magnetic field type Number of pulses applied Pulsed magnetic field application direction Residual magnetic flux density
(kG) 1-4-1 (comparative example) 2.4 direct current 13.25 3-1 (Example) 2.4 Pulse + direct current 4 N-> N-> N-> N 13.54 3-2 (comparative example) 2.4 Pulse + direct current 4 N-> S-> N-> S 13.60 3-3 (Example) 2.4 Pulse + direct current 4 N-> N-> S-> S 13.57

The results of Examples 1 to 3 show that the magnetic field orientation method of mixing the pulse current and the direct current improves the residual magnetic flux density in comparison with the conventional magnetic field orientation method of applying the direct current only, It can be seen that it is more effective to apply the direct current after the circuit is applied.

Further, the present invention is not limited to the above-described embodiments, but can be appropriately changed without departing from the gist of the present invention. For example, the composition of the raw material powder, the shape and size of the molded body, the magnetic field application speed, the sintering conditions, and the like can be appropriately changed.

Claims (5)

A manufacturing method for manufacturing a sintered magnet by using a powder made of a rare earth alloy containing a rare earth element and iron,
A preparation step of preparing a raw material powder composed of the rare earth alloy and having a particle size ranging from 2 to 10 mu m,
A step of charging the raw material powder into a molding die,
A pulse current application step of applying a high-field pulse current to the charged raw material powder,
And simultaneously compressing and applying a direct current of the author to the pulse current after the pulse current application step;
The molding granularity of the raw material powder is in the range of 1.6 to 3.0 g / cc,
A pulse magnetic field is applied 1 to 10 times in the pulse current application step,
The direction of the pulse magnetic field applied in the pulse current application step is alternately applied,
The particle size of the raw material powder is measured by a laser diffraction particle size distribution apparatus,
To the raw powder, a lubricant is added;
The lubricant is a solid phase lubricant of hexagonal boron nitride,
The solid lubricant is 0.01% by mass or more and 5% by mass or less based on the mass of the raw material powder,
The pulse current is applied in a magnetic field of 3 to 5 tesla for 0.01 to 0.1 second in the application step,
The direct current is applied in the range of 5 ~ 20 seconds in magnetic field of 1.5 ~ 2 tesla in the application process,
The raw material powder preparing step is,
The rare earth alloy is melted by this cobalt heating method, is made into an alloy ingot using a strip casting method,
The prepared alloy ingot absorbs hydrogen in a hydrogen atmosphere to improve the crushability,
Subsequently, after performing a treatment for removing hydrogen at a vacuum and at 600 ° C,
A process for producing a uniform and fine powder having a particle size of 3.5 mu m by a pulverizing method using a jute mill technique is sequentially performed;
The process for producing a fine powder is performed in a nitrogen or inert gas atmosphere to prevent the oxygen from being contaminated and deteriorating the magnetic properties,
Characterized in that the molded sintered magnet is subjected to heat treatment at 500 DEG C for 2 hours to produce a rare earth permanent magnet delete delete delete delete

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