KR101789726B1

KR101789726B1 - Manufacturing method of neodymium magnet

Info

Publication number: KR101789726B1
Application number: KR1020150186026A
Authority: KR
Inventors: 양혁; 김주영; 오윤석; 이영주
Original assignee: 주식회사 포스코; 재단법인 포항산업과학연구원
Priority date: 2015-12-24
Filing date: 2015-12-24
Publication date: 2017-10-25
Also published as: KR20170076138A

Abstract

The method for manufacturing a neodymium magnet according to an embodiment of the present invention includes the steps of melting a composition of a neodymium magnet in a melting furnace to form a strip, pulverizing the strip into powder, mixing the powder with a lubricant, , Measuring the carbon content of the powder, molding the powder in a magnetic field, and sintering the formed body, wherein the sintering step includes a step of heating the sintering furnace And a variable step of changing the time.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing a neodymium magnet,

The present invention relates to a method of manufacturing a neodymium magnet.

Neodymium magnets that use rare earths, including Neodymium (Nd), are the most powerful magnets of today's permanent magnets and are widely used in automotive motors, consumer electronics, and the like. However, neodymium magnets deteriorate at high temperatures, and Nd-Fe-B structure is vulnerable to oxidation. Therefore, neodymium magnets are required to be used in places where they do not come in contact with air during use of magnets or in other general conditions.

Neodymium magnets are susceptible to external oxidation even in the sintered state, but they are more susceptible to oxidation in the powder state. Therefore, when neodymium magnets are pulverized in the form of powders in the process of producing neodymium magnets, they have a characteristic of instantaneous ignition in the atmosphere. In order to prevent this, a small amount of lubricant for antioxidation is added almost always when dealing with powdered raw materials during the manufacturing process of neodymium magnets. As the lubricant, a hydrocarbon compound or a derivative thereof is mainly used.

However, these lubricants are substances that should eventually disappear after the magnets are sintered. If the hydrocarbonaceous lubricant remains until sintering, the carbon content in the sintered body becomes high. Neodymium magnets with high carbon content, like carbon steels, have very hardening properties, and cracking properties can lead to significant defects in machinability. Therefore, a sintering method that uses a lubricant and low carbon content should be used.

And to provide a manufacturing method for lowering the carbon content of neodymium magnets.

The sintering step may be a continuous sintering method and the sintering step may include a fixing step in which the sintering furnace is fixed in condition.

The pulverizing step may include a coarsely pulverizing step of pulverizing the strip into a coarse powder and a pulverizing step of pulverizing the coarse powder into a fine powder.

The kneading step may include a first kneading step of adding and mixing a lubricant to the crude powder, and a second kneading step of adding and mixing a lubricant to the fine powder.

The coarsely crushing step may be performed through a hydrogen crushing process.

The pulverization step may be performed through a jet mill process.

In the kneading step, the lubricant may be added to the powder in an amount of 0.1 wt.% To 0.3 wt.%, Followed by mixing the powders.

The composition of the neodymium magnet may include at least one of neodymium (Nd), neodymium (Nd) / praseodymium (Pr) alloy, dysprosium (Dy), terbium (Tb), holmium (Ho), boron (B), cobalt ), Gallium (Ga), zirconium (Zr), niobium (Nb), and iron (Fe).

The total amount of the rare earth elements in the composition of the neodymium magnet may be 28 wt.% Or more and 40 wt.% Or less.

Wherein the variable step is performed for 85 to 95 minutes when the measured carbon content is 0.2 wt.% Or less and then for 85 to 95 minutes after the temperature is raised to 450 DEG C for 85 to 95 minutes, and the measured carbon content exceeds 0.2 wt.% %, The temperature is raised to 500 ° C. for 85 minutes to 95 minutes and then maintained for 85 minutes to 95 minutes. When the measured carbon content is more than 0.3 wt.%, The temperature can be maintained for 115 to 125 minutes.

The fixing step may be performed after the variable step, and may include a first step of raising the temperature to 700 for 55 to 65 minutes and then maintaining the temperature for 115 to 125 minutes.

The fixing step may be performed after the first step, and may include a second step of maintaining the temperature elevated to 900 degrees for 55 minutes to 65 minutes and then for 115 minutes to 125 minutes.

The fixing step may be performed after the second step and may include a third step of maintaining the temperature for 350 minutes to 370 minutes after the temperature is raised to 1000 degrees or more for 55 minutes to 65 minutes.

The neodymium magnet according to an exemplary embodiment of the present invention includes at least one of neodymium (Nd), neodymium (Nd) / praseodymium (Pr) alloy, dysprosium (Dy), terbium (Tb), holmium (Ho), boron (B), cobalt ), Aluminum (Al), gallium (Ga), zirconium (Zr), niobium (Nb), iron (Fe) and the content of carbon is 0.15 wt.% Or less.

The sum of the rare earth elements can be from 28 wt.% To less than 40 wt.%.

% Or more and 35 wt.% Or less of the neodymium (Nd) or the neodymium (Nd) / praseodymium (Pr) alloy and the dysprosium (Dy), the terbium (Tb) or the holmium (Ho) % Of boron (B), 1.1 wt.% Or less of boron (B), 0.5 wt.% Or more and 1.5 wt.% Or less of cobalt (Co) And may contain 1 wt.% Or less of aluminum (Al), gallium (Ga), zirconium (Zr) or niobium (Nb), and other than iron (Fe).

According to the present invention, neodymium magnets having improved workability and magnet characteristics can be manufactured by providing a method of manufacturing a neodymium magnet that lowers the carbon content while using a lubricant to prevent oxidation of the neodymium magnet powdery raw material.

FIGS. 1 to 3 are graphs illustrating a continuous sintering method of a neodymium magnet manufacturing method according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

In addition, since the sizes and thicknesses of the respective components shown in the drawings are arbitrarily shown for convenience of explanation, the present invention is not necessarily limited to those shown in the drawings. In the drawings, the size is enlarged in order to clearly represent a part of the constitution.

Also, throughout the specification, when an element is referred to as "including" an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

A method of manufacturing a neodymium magnet according to an embodiment of the present invention will now be described in detail with reference to FIGS. 1 to 3. FIG.

A method of manufacturing a neodymium magnet according to an embodiment of the present invention includes the steps of melting a composition of a neodymium magnet in a melting furnace to form a strip, pulverizing the strip into powder, kneading the mixture with a lubricant, And a carbon content, measuring a powder in a magnetic field, and sintering the formed body.

The composition of the neodymium magnets may comprise from 28 wt.% To less than 35 wt.% Of neodymium (Nd) or neodymium (Nd) / praseodymium (Pr) alloys. (D), terbium (Tb), or holmium (Ho), and may contain not less than 0.9 wt.% And not more than 1.1 wt.% Of boron (B) and not less than 0.5 wt. % Or less cobalt (Co). (Al), gallium (Ga), zirconium (Zr) or niobium (Nb) in an amount of 1 wt.% Or less, and may be composed of iron (Fe).

A rare earth element such as neodymium (Nd), neodymium (Nd) / praseodymium (Pr) alloy, dysprosium (Dy), terbium (Tb) or holmium (Ho) has a total content of 28 wt.% To 40 wt. &Lt; / RTI >

The composition of neodymium magnets can be melted in the melting furnace of all 1400 ~ 1550 degrees through the strip casting process and then released into strip form.

The coarse grinding step can be accomplished through a hydrogen fracture process. In hydrogen crushing process, hydrogen is injected by adding hydrogen of 0.5atm to 1.5atm at 200degree under the condition of 200degree of vacuum, and when hydrogen is sufficiently injected, dehydrogenation is performed at 550degree or more and 600degree for 3hr to 5hr . &Lt; / RTI >

The milling step may be accomplished through a jet mill process. The coarse powder may be pulverized into a fine powder having an average particle size of 3 to 5 μm through a jet milling process.

The kneading step may include a first kneading step of adding a lubricant to the crude powder and mixing them, and a second kneading step of adding a lubricant to the fine powder and mixing them. The lubricant prevents the oxidation of the powder and increases the fluidity of the powder in the post-addition process. Therefore, even when the coarse powder is finely pulverized by the jet milling process, the collision between powders can naturally occur, and when the fine powder is molded in the magnetic field In the process of putting the powder into the mold and compressing it, it can be pressed smoothly so that the powder adheres to each other well.

The kneading step may be performed by adding 0.1 wt.% Or more and 0.3 wt.% Or less of a lubricant to the powder and then mixing the powders as a whole. As the lubricant, a hydrocarbon compound or a derivative thereof may be used.

Before going to the molding step, take a small sample of the jet milled finer powder and measure the amount of carbon contained in the sample.

In the molding step, a green compact can be produced by applying pressure while applying a specific magnetic field to the fine powder.

When the molded body is manufactured, the molded body is subjected to a sintering step. The continuous sintering method can be used in the sintering step, and the continuous sintering method is a continuous sintering method in which the sintering is carried out by sequentially charging the first to seventh chambers in seven spaces. One of them is a room to make a vacuum condition at room temperature. Seven rooms are a room where the sintered magnet is cooled to room temperature. There are five rooms, two to six rooms, where temperature is actually raised.

The continuous sintering method may include a variable step of changing the conditions of the sintering furnace according to the result of measuring the carbon content of the powder and a fixing step of fixing the conditions of the sintering furnace. The double variable stage corresponds to two rooms, and the fixed stage corresponds to three to six rooms. The variable step proceeds by changing the temperature and the holding time of the sintering furnace according to the result of measuring the carbon content of the powder. In the two-chamber sintering furnace in which the variable step is performed, a vacuum pump is present, and the lubricant inside the molded body which is volatilized in the variable step may be discharged.

When the measured carbon content is 0.2 wt.% Or less, the variable stage (two chambers) can be maintained at 450 DEG C for 90 minutes after starting at 200 DEG C for 90 minutes as shown in FIG. When the measured carbon content is greater than 0.2 wt.% And less than 0.3 wt.%, The variable stage (two chambers) may start at 200 degrees as shown in FIG. 2 and be heated to 500 degrees for 90 minutes and then maintained at 500 degrees for 90 minutes . When the measured carbon content is more than 0.3 wt.%, The variable stage (two chambers) can start at 200 degrees as shown in FIG. 3 and be heated to 500 degrees for 60 minutes and then maintained at 500 degrees for 120 minutes. FIG. 1 is a graph schematically showing a continuous sintering method of a neodymium magnet manufacturing method according to an embodiment of the present invention when the measured carbon content is 0.2 wt.% Or less. FIG. % Of the carbon content of the neodymium magnet according to an embodiment of the present invention when the measured carbon content is more than 0.3 wt.%, And FIG. 3 is a graph 1 is a graph schematically showing a continuous sintering method of a neodymium magnet manufacturing method according to an embodiment.

In this way, the sintering is performed by changing the temperature and the holding time of the sintering furnace in a customized manner in accordance with the result of measuring the carbon content of the powder.

The fixing step is carried out after the variable step. Regardless of the carbon content measured as in FIGS. 1 to 3, the fixing step is started at 600 ° C. for 60 minutes and then heated to 700 ° C. for 120 minutes. ), The second stage (4 rooms) in which the temperature is raised from 800 ° C. to 900 ° C. for 60 minutes and maintained at 900 ° C. for 120 minutes, the temperature is raised from 990 ° C. to the final sintering temperature of more than 1000 ° C. for 60 minutes, And a third step (5 rooms, 6 rooms).

By using the continuous sintering furnace as described above, a space for volatilizing the lubricant of the formed body and a space for sintering for 360 minutes reaching the final sintering temperature are physically separated.

The lubricant contained in the powder is a substance that should disappear after the magnet is finally sintered. If the lubricant remains after the sintering, the carbon content in the sintered body becomes high and the neodymium permanent magnet having a high carbon content causes a great defect in workability. When carbon is present in a neodymium magnet with 70% iron content in mass fraction, it hardens very much like carbon steel, and it is difficult to process the magnet because of its easily cracked nature.

When the neodymium magnet manufacturing method according to the present invention is used, it is possible to control the low-temperature holding period for each sintering furnace by the variable step and to perform the low-temperature section treatment according to the amount of the lubricant. It is possible to maximize the removal of the lubricant while minimizing the problem of nitrogen compound generation which occurs when the magnet is kept at a temperature for a long time and the consistency of each magnet is influenced by the time and temperature of the sintering process at 1000 degrees or more, It is possible to manufacture a magnet of a certain quality by a fixing step in which the temperature and time conditions are kept constant without receiving the magnetic force. When a neodymium magnet manufacturing method according to the present invention is used, manufacture of neodymium magnets of excellent quality with high average residual magnetic density (Br), coercive force (Hc) and magnetic energy product (BHmax) can do.

Hereinafter, a neodymium magnet according to an embodiment of the present invention will be described in detail.

Neodymium magnets are composed of neodymium (Nd), neodymium (Nd) / praseodymium (Pr) alloys, dysprosium (Dy), terbium (Tb), holmium (Ho), boron (B), cobalt (Ga), zirconium (Zr), niobium (Nb), iron (Fe), and the content of carbon is 0.15 wt.% Or less.

Neodymium magnets can contain between 28 wt.% And 35 wt.% Neodymium (Nd) or neodymium (Nd) / praseodymium (Pr) alloys and can contain less than 10 wt.% Of dysprosium (Dy), terbium (Tb) Ho), and may include not less than 0.9 wt.% And not more than 1.1 wt.% Boron (B) and not less than 0.5 wt.% And not more than 1.5 wt.% Cobalt (Co). (Al), gallium (Ga), zirconium (Zr) or niobium (Nb) in an amount of 1 wt.% Or less, and may be composed of iron (Fe).

A rare earth element such as neodymium (Nd), neodymium (Nd) / praseodymium (Pr) alloy, dysprosium (Dy), terbium (Tb) or holmium (Ho) may be less than 40 wt. have.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the following claims. Those who are engaged in the technology field will understand easily.

Claims

Dissolving the composition of the neodymium magnet in a melting furnace and discharging it as a strip;
A pulverizing step of pulverizing the strip into powder;
A kneading step of adding and mixing a lubricant to the powder;
Measuring a carbon content of the powder;
A shaping step of shaping the powder into a compact in a magnetic field;
A sintering step of sintering the formed body; / RTI >
Wherein the sintering step includes a variable step of changing the temperature or the holding time of the sintering furnace according to the content of the carbon measured.

The method of claim 1,
The sintering step uses a continuous sintering method,
Wherein the sintering step includes a fixing step in which a condition of the sintering furnace is fixed.

3. The method of claim 2,
Wherein the pulverizing step comprises a coarse grinding step of pulverizing the strip into a coarse powder and a pulverizing step of pulverizing the coarse powder into a fine powder.

4. The method of claim 3,
Wherein the kneading step includes a first kneading step of adding and mixing a lubricant to the crude powder, and a second kneading step of adding and mixing a lubricant to the fine powder.

4. The method of claim 3,
Wherein the coarse grinding step is performed through a hydrogen crushing step.

4. The method of claim 3,
Wherein the pulverizing step is performed through a jet mill process.

5. The method of claim 4,
Wherein the kneading step comprises adding 0.1 wt.% Or more and 0.3 wt.% Or less of a lubricant to the powder, and mixing the powders.

5. The method of claim 4,
The composition of the neodymium magnet includes neodymium (Nd) or neodymium (Nd) / praseodymium (Pr) alloys,
(Dy), Tb, Ho, Boron, Co, Al, Ga, Zr, Nb, Fe, &Lt; / RTI > further comprising one or more of the following.

9. The method of claim 8,
Wherein the sum of the rare earth elements in the composition of the neodymium magnet is 28 wt.% Or more and 40 wt.% Or less.

3. The method of claim 2,
Wherein the variable step is performed for 85 to 95 minutes when the measured carbon content is 0.2 wt.% Or less and then for 85 to 95 minutes after the temperature is raised to 450 DEG C for 85 to 95 minutes, and the measured carbon content exceeds 0.2 wt.% %, The temperature is raised to 500 ° C. for 85 minutes to 95 minutes and then maintained for 85 minutes to 95 minutes. When the measured carbon content is more than 0.3 wt.%, And maintaining the temperature for 115 to 125 minutes.

3. The method of claim 2,
Wherein the fixing step is performed after the variable step, and the first step of maintaining the temperature for from about 55 minutes to about 65 minutes to about 700 minutes for about 115 minutes to about 125 minutes.

12. The method of claim 11,
Wherein the fixing step is performed after the first step, and the second step of maintaining the temperature for from 115 minutes to 125 minutes after raising the temperature to 900 degrees for 55 minutes to 65 minutes.

The method of claim 12,
Wherein the fixing step is performed after the second step, and the third step of maintaining the temperature for 350 minutes to 370 minutes after the temperature is elevated to 1000 degrees or more for 55 minutes to 65 minutes.

delete