KR102222483B1 - A method of Magnetic Powder and Magnetic Material - Google Patents

Abstract

A manufacturing method of Nd-Fe-B-based magnetic powder capable of further improving the magnetic properties according to the present invention includes the step of milling to prepare the Nd-Fe-B-based magnetic powder after rapidly solidifying the Nd-Fe-B-based alloy molten metal.

Description

Nd-Fe-B magnetic powder manufacturing method and magnetic material with excellent magnetic properties {A method of Magnetic Powder and Magnetic Material}

The present invention relates to a magnetic powder manufacturing method and a magnetic material capable of improving magnetic properties such as coercivity.

The conventional quenched magnetic powder (for example, MQ powder) obtains a uniform microstructure that contributes to excellent magnetic properties, so that the molten alloy is rapidly cooled at high speed. For example, in the case of manufacturing the conventional quenched magnetic powder by the single roll method, since rare earth magnets easily oxidize the magnetic powder in the atmosphere, there is a problem that the characteristics of the magnetic powder itself are deteriorated by heating during injection molding. There is a point in that a molded article having sufficient magnetic properties cannot be obtained.

In addition, this oxidation phenomenon may be particularly severe when the conventional quenched magnetic powder contains particles having an average particle diameter of 40 μm or less.

In order to solve the above problems, Korean Patent Laid-Open Publication No. 10-2018-0070522 discloses Nd-Fe-B alloy powder having a D50 of 30 to 50 µm, using a magnetic pulsed compaction (MPC) molding method that applies high pressure within a short time. Disclosed is a method of manufacturing an Fe-B-based molded article.

As a result of continuously carrying out such research, the present inventors have identified a peculiar phenomenon in which magnetic properties are deteriorated when using a simple spherical Nd-Fe-B alloy powder manufactured by the atomizer method and attempted to improve this.

Korean Patent Publication No. 10-2018-0070522

The present invention has been devised to solve the above problems, and is to provide a method of manufacturing a magnetic material capable of further improving magnetic properties than that of using a simple spherical Nd-Fe-B magnetic powder.

In addition, the present invention is to provide a magnetic powder and magnetic material having excellent magnetic properties through the above manufacturing method.

On the other hand, other objects not specified of the present invention will be additionally considered within a range that can be easily deduced from the detailed description and effects thereof below.

In order to achieve such an object, a method of manufacturing a Nd-Fe-B magnetic material according to an embodiment of the present invention rapidly solidifies an Nd-Fe-B-based alloy molten metal, and then milled to Nd-Fe-B. It includes the step of preparing the field powder.

In the method of manufacturing an Nd-Fe-B magnetic material according to an embodiment of the present invention, during the milling, the rotation speed of the miller and the rotation speed of the disk may be adjusted.

In the method of manufacturing an Nd-Fe-B magnetic material according to an embodiment of the present invention, the Nd-Fe-B magnetic material may be manufactured to have an average particle size of 11 to 25 μm, more preferably It can be prepared to have an average particle size of 12 ~ 22 ㎛.

In the method of manufacturing an Nd-Fe-B-based magnetic material according to an embodiment of the present invention, the Nd-Fe-B-based magnetic material may be manufactured to have a circularity of 80% or more.

In the method of manufacturing an Nd-Fe-B magnetic material according to an embodiment of the present invention, the step of manufacturing the magnetic powder may be rapid solidification by a gas atomizing method.

In the method of manufacturing an Nd-Fe-B-based magnetic material according to an embodiment of the present invention, the Nd-Fe-B-based molten alloy may further include at least one or more of Pr, Co, Ti, and Zr. .

In addition, the present invention includes an Nd-Fe-B-based magnetic powder produced by the above-described method for producing the Nd-Fe-B-based magnetic powder.

In addition, the present invention includes a Nd-Fe-B-based magnetic material manufactured by using a magnetic pulsed compaction method or an electrification pressurization sintering method of the Nd-Fe-B magnetic powder.

The manufacturing method of the Nd-Fe-B magnetic powder according to the present invention shows a coercive force that is about two times higher than that of the spherical Nd-Fe-B magnetic powder that is not milled.

On the other hand, even if it is an effect not explicitly mentioned herein, it is added that the effect described in the following specification and its provisional effect expected by the technical features of the present invention are treated as described in the specification of the present invention.

1 is a flowchart illustrating a method of manufacturing an Nd-Fe-B magnetic powder according to an embodiment of the present invention.
2 is a graph showing the particle size distribution of Nd-Fe-B magnetic powder according to an embodiment of the present invention.
3 is a SEM photograph showing the morphology of the Nd-Fe-B magnetic powder according to an embodiment of the present invention.
4 is a SEM photograph showing a microstructure of an Nd-Fe-B magnetic powder according to an embodiment of the present invention.
5 is a graph showing a circular diagram of an Nd-Fe-B magnetic powder according to an embodiment of the present invention.
6 is a graph showing magnetic properties of Nd-Fe-B magnetic powder according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The following embodiments and drawings are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art to which the present invention pertains. In addition, unless there are other definitions in the technical and scientific terms used in the present invention, the present invention has the meaning commonly understood by those of ordinary skill in the art to which this invention belongs, and the present invention in the following description and accompanying drawings Descriptions of known functions and configurations that may unnecessarily obscure the gist of are omitted.

The present invention is to provide a method of manufacturing an Nd-Fe-B-based magnetic powder capable of further improving magnetic properties than the conventional simple spherical Nd-Fe-B-based magnetic powder.

The manufacturing method of the Nd-Fe-B-based magnetic powder according to the present invention includes the step of rapidly solidifying an Nd-Fe-B-based alloy molten metal and then milling to produce an Nd-Fe-B-based magnetic powder.

The method of milling is not necessarily limited, but may be performed using a planetary mill in which rotation and revolution are simultaneously performed. The planetary mill is driven by including a miller and a disc, and the magnetic powder is driven by the rotational motion (or rotational motion) of the miller containing the raw material powder and the rotational motion (or rotational motion) of the disc revolving the miller. May be to crush.

In the manufacturing method of the Nd-Fe-B magnetic powder according to an embodiment of the present invention, the powder of the Nd-Fe-B magnetic powder finally produced by adjusting the rotation speed of the miller and the rotation speed of the disk during the milling The particle size, particle size distribution, and microstructure of the can be adjusted.

For example, during the milling, the rotational speed of the miller may be 100 to 1100 rpm, and the rotational speed of the disk may be 240 to 2640 rpm. Accordingly, the average particle size of the final manufactured Nd-Fe-B magnetic powder may be 11 to 25 μm.

In addition, the circularity of the Nd-Fe-B magnetic powder may be 80% or more.

According to an embodiment of the present invention, when the average particle size of the Nd-Fe-B-based magnetic powder after milling is 10 to 25 µm and the circularity of the Nd-Fe-B-based magnetic powder is 80% or more, the residual magnetization is large. It is possible to provide a Nd-Fe-B-based magnetic powder whose coercivity is greatly improved without decreasing.

On the other hand, in describing the present invention, the circularity of the powder may be determined by Equation 1 below.

[Equation 1]

(In Equation 1, A is the projection area of the powder (or particle) projected two-dimensionally, and P is the circumference length of the powder (or particle) projected two-dimensionally.)

According to an embodiment of the present invention, the circularity of the Nd-Fe-B magnetic powder may be 80% to 95%.

In addition, according to an embodiment of the present invention, the Nd-Fe-B magnetic powder may have a multimodal particle size distribution having two or more peaks.

Meanwhile, the magnetic powder according to an embodiment of the present invention may be prepared by rapidly solidifying the above-described molten Nd-Fe-B alloy by a gas atomizing method. At this time, the Nd-Fe-B-based alloy molten metal may be composed of Nd: 5-20 atomic%, Fe: 70-88 atomic%, and B: 1-10 atomic%, but the present invention is an Nd-Fe-B-based alloy It is not necessarily limited to the composition of the molten metal.

In addition, the molten Nd-Fe-B alloy according to an embodiment of the present invention may further include at least one or more of Pr, Co, Ti, and Zr. At this time, the Nd-Fe-B-based alloy molten metal is Nd: 5 to 20 atomic%, Fe: 70 to 88 atomic%, B: 1 to 10 atomic%, and among Pr, Co, Ti, Zr, Al, Cu, and Ga At least one or more may be made of 1 to 20 atomic%, but the present invention is not necessarily limited to the composition of the Nd-Fe-B-based molten alloy.

In addition, the present invention includes Nd-Fe-B-based magnetic powder produced by the above-described method for producing Nd-Fe-B-based magnetic powder.

For example, the Nd-Fe-B magnetic powder may have an average particle size of 10 to 25 μm. The circularity of the Nd-Fe-B-based magnetic powder may be 80% or more, more preferably 80% or more and 95% or less.

In addition, the residual magnetic density of the Nd-Fe-B magnetic powder may be about 50 to 80 emu/g, preferably 60 to 80 emu/g, more preferably 65 to 80 emu/g, but the present invention It is not necessarily limited thereto.

In addition, the coercive force of the Nd-Fe-B magnetic powder may be about 3,000 to 10,000 Oe, preferably 4,000 to 10,000 Oe, and more preferably 5,000 to 10,000 Oe, but the present invention is not necessarily limited thereto.

In addition, the present invention includes a magnetic material manufactured by using a magnetic pulsed compaction method or an electrification pressurization sintering method of the Nd-Fe-B magnetic powder.

Hereinafter, the present invention will be described in detail by examples. The examples described below are intended to make the present invention easily understood by those skilled in the art, and the present invention is not limited by the following examples.

Examples 1 to 3, Comparative Examples 1 and 2

Referring to Fig. 1, Embodiment 1 of the present invention will be described in more detail. 1 is a flowchart illustrating a method of manufacturing an Nd-Fe-B magnetic powder according to an embodiment of the present invention.

First, the molten Nd-Fe-B alloy having the above-described composition was rapidly solidified by spraying argon gas through an orifice to obtain a powder having a spherical shape. The powder was Nd2Fe14B (JCPDS No. 00-036-1296) crystal.

After that, the powder manufactured using high-energy ball milling was pulverized. Specifically, the powder rapidly solidified by gas atomizing was put into a miller equipped with a planetary mill equipment, and the rotation speed of the miller and the rotation speed of the disk It was pulverized by controlling.

Table 1 shows the residual magnetic density and coercivity of the Nd-Fe-B magnetic powder obtained by pulverization.

(In Table 1, the powder according to Comparative Example 1 was obtained by rapidly solidifying a molten Nd-Fe-B alloy.)

As for the magnetic properties, a green compact was prepared by compacting the powders each having an average powder size, and then sintered in a vacuum atmosphere by energizing pressurization sintering to prepare a specimen.

Magnetic properties, such as coercivity and residual magnetization density, were measured with each specimen prepared by sintering by the energizing pressurization sintering method.

The Nd-Fe-B magnetic powder prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were analyzed.

2 is a graph showing the particle size distribution of Nd-Fe-B magnetic powder according to Examples 1 to 3 and Comparative Examples 1 and 2. FIG. As shown in FIG. 2, the Nd-Fe-B-based magnetic powder according to Comparative Examples 1 and 2 has an average particle diameter of 9 and 40 um, and the Nd-Fe-B-based magnetic powder according to Example 1-3 has an average particle diameter of about 12. It was confirmed that it was -22 um.

In addition, as shown in FIG. 2, as the average particle diameter decreased by about 45% or more through the high-energy ball milling process, the particle size distribution was changed from single modal to a multimodal particle size distribution mode in which two or more peaks such as bimodal and three modal are present. .

Table 2 above is related to the average particle size of WPSD, D10, D50, D90 and Examples and Comparative Examples. Span is a value for each average particle size calculated by the calculation formula (D90-D10)/D50. As the graph of FIG. 2 increases, the width of the curve of the graph in the form of a parabolic line of FIG. 2 increases, and when the value of the span is small, the width of the parabolic line is narrow. The numbers on the horizontal axis of Table 2 indicate the average particle size, Dx on the vertical axis relates to the particle distribution ratio, and D50 refers to the size of the horizontal axis reaching 50%. For example, 41.48, which is a D50 of 40 µm in width, corresponds to 50% of particles having a size smaller than or equal to 41.48 µm in particles having an average particle size of 40 µm.

3 is a SEM photograph showing the morphology of Nd-Fe-B magnetic powder according to Examples 1 to 3 and Comparative Examples 1 and 2. FIG. 3, the Nd-Fe-B-based magnetic powder according to Comparative Example 2 has a spherical shape, but the Nd-Fe-B-based magnetic powder according to Examples 1 to 3 and Comparative Example 1 has an angular shape. And it was confirmed that the small powder and the large powder were mixed with each other in a size distribution.

4 is a SEM photograph showing the microstructure of the Nd-Fe-B magnetic powder according to Examples 1 to 3 and Comparative Examples 1 and 2. FIG. As shown in FIG. 4, the particles of the Nd-Fe-B-based magnetic powder according to Comparative Example 2 show a shape close to a spherical shape, but from Example 1, the inside of the spherical particles are sequentially divided, and as Example 3 proceeds, It was confirmed that the degree of cracking became severe. It can be seen that the Nd-Fe-B-based magnetic powder according to Examples 1 to 3 is pulverized to the size shown in FIG. 2 and separated into one particle.

5 is a graph showing the circularity of Nd-Fe-B magnetic powder according to Examples 1 to 3 and Comparative Examples 1 and 2. FIG. As shown in FIG. 5, as the average particle size of the powder decreases by the high-energy milling process described above, a phenomenon in which the circularity is initially decreased due to an irregular shape, and then the average particle size is about 12 μm or less. At, you can see the trend of gradually increasing circularity. It can be seen that the circularity of the Nd-Fe-B magnetic powder is controlled by the milling conditions (rotation speed) of Table 1 described above.

In addition, since the circularity of the Nd-Fe-B-based magnetic powder according to Examples 1 to 3 is distributed in about 85 to 93%, the circularity of the above-described Nd-Fe-B-based magnetic powder is satisfied that the circularity is at least 80% or more. I can see that.

6 is a graph showing magnetic properties of Nd-Fe-B magnetic powders according to Examples 1 to 3 and Comparative Examples 1 and 2. FIG. As shown in FIG. 6, the coercive force and residual magnetization density values of the Nd-Fe-B-based magnetic powder according to Example 1 having a finer average particle size than the magnetic properties of the Nd-Fe-B-based magnetic powder according to Comparative Example 2 were much higher. It was confirmed that the Nd-Fe-B magnetic powder according to Examples 2 and 3 had a lower residual magnetization density than Comparative Example 2, but showed about twice as high coercivity. However, it was confirmed that the powder according to Comparative Example 1 had a finely high coercivity despite the small average particle size, but the residual magnetization density rapidly decreased.

As described above, it can be seen that the magnetic powder produced by the method for producing the Nd-Fe-B-based magnetic powder according to the present invention has excellent coercivity and residual magnetization density and has a high circularity of 80% or more. The excellent magnetic properties appear to have increased the coercive force to the maximum value at 22㎛ as the size of the powder particles became almost the same as the domain size at 22㎛ while being pulverized. It is to do. As such, it was predicted that powders of a certain size or less were associated with the size of the domains, as well as sintering from a low temperature during sintering, resulting in a decrease in coercivity due to large recrystallization of some particles. On the other hand, at 22 µm or more, the coercive force gradually decreased in proportion to the particle size as a plurality of domains existed in one particle, indicating that it was only 2600 Oe at 40 µm. Accordingly, it can be interpreted that the size and magnetic properties of the powder are highly correlated, and in the present invention, it has been shown that it is desirable to manufacture by sintering a powder having a size of 11 to 25 μm showing a coercive force of 5000 Oe or more. In particular, it is more preferable to prepare a sintered body having a powder having a size of 12-22 µm because a magnetic body having a coercive force of a certain size can be obtained. In addition, having a circularity of 80% or more and a particle size distribution of more than bimodal is expected to be advantageous in improving the sintering density and magnetic properties by increasing the filling property when manufacturing a molded body or a sintered body.

As described above, the present invention has been described by specific matters and limited embodiments and drawings, but this is provided only to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention is Those of ordinary skill in the relevant field can make various modifications and variations from this description.

Therefore, the spirit of the present invention is limited to the described embodiments and should not be defined, and all things that are equivalent or equivalent to the claims as well as the claims to be described later fall within the scope of the spirit of the present invention. .

Claims (9)

In the manufacturing method of the Nd-Fe-B-based magnetic powder comprising the step of producing a Nd-Fe-B-based magnetic powder by rapidly solidifying the Nd-Fe-B-based alloy molten metal and then milling to a predetermined size,
The magnetic powder is composed of Nd: 5 to 20 atomic%, Fe: 70 to 88 atomic% and B: 1 to 10 atomic%,
A method of manufacturing Nd-Fe-B magnetic powder that is manufactured to have an average particle size of 11 to 25 μm. The method of claim 1,
During the milling, a method of manufacturing Nd-Fe-B magnetic powder for controlling the rotational speed of the miller and the rotational speed of the disk. delete The method of claim 1,
The method of manufacturing the Nd-Fe-B-based magnetic powder, wherein the magnetic powder is manufactured to have an average particle size of 12 to 22 μm. The method of claim 1,
The method of manufacturing Nd-Fe-B-based magnetic powder, wherein the magnetic powder is manufactured to have a circularity of 80% or more. The method of claim 1,
The step of producing the magnetic powder is a method for producing a Nd-Fe-B-based magnetic powder that is rapidly solidified by a gas atomizing method. The method of claim 1,
The Nd-Fe-B-based alloy molten metal further comprises at least one of Pr, Co, Ti, and Zr. A magnetic powder produced by the method for producing an Nd-Fe-B-based magnetic powder according to any one of claims 1 to 2 and 4 to 7. A magnetic material manufactured by using a magnetic pulsed compaction method or an electrification pressurization sintering method of the Nd-Fe-B magnetic powder according to claim 8.

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