KR20200019020A - Preparation method of Fe-Si magnetic powder - Google Patents

Abstract

An embodiment of the present invention provides a preparation method of Fe-Si powder, which comprises the following steps of: preparing a Fe-Si alloy having 4.0-9.0 wt% of Si contents; grinding the prepared alloy after crushing the same; distributing the ground and crushed alloy; and spheroidizing and quenching the distributed alloy by using RF plasma. Accordingly, a precision part with high functionality using a soft magnetic alloy can be manufactured.

Description

Preparation method of Fe-Si magnetic powder {Preparation method of Fe-Si magnetic powder}

The present invention relates to a method for producing Fe-Si magnetic powder, and more particularly, to a method for producing Fe-Si magnetic powder by crushing and classifying a Fe-Si alloy having a Si content of 4 wt% or more, spheroidizing by quenching and quenching. It is about.

In general, Fe-Si-based alloy is a representative soft magnet material and is widely used as a component material of motors and generators that are important for energy efficiency in the automotive, electronics, battery, and communication industries, and require high performance, automation, and miniaturization of devices. Accordingly, various studies on mechanical or magnetic properties have been conducted.

It is well known that increasing iron content in Fe-Si alloys reduces iron loss. This is because the magnetic anisotropy and the crystal anisotropy of the Fe-Si alloy decrease with increasing Si content, and the electrical resistivity thereof increases. Increasing the amount of silicon contained in the Fe-Si alloy from 3% by weight to 6.5% by weight, the electrical resistivity increases from 48 μΩ / m to 82 μΩ / m, while the eddy current loss decreases rapidly and the iron loss at high frequency. Decrease, so small that the magnetostriction is close to zero.

Therefore, since the noise and vibration can be reduced, Fe-Si-based alloy containing 6.5% by weight of silicon is close to the ideal soft magnetic alloy. However, as the amount of silicon increases, the alloy becomes increasingly fragile, so that Fe-Si alloys containing 4% by weight or more of silicon are very difficult to cold roll.

In the prior art, a powder core is used to solve the formability of the Fe-Si alloy. However, since the Fe-Si alloy powder core containing a large amount of silicon also has poor workability, the density of the powder core decreases due to the deterioration of deformation during compression molding. Conventional Fe-Si-based alloy powder core is made of gas or water yarn, the average particle diameter is about 100㎛ there is a limit to the filling density, there is a problem that the quality is reduced by forming the B2 phase, DO ₃ phase during manufacture.

Republic of Korea Patent Publication No. 10-2015-0055901

The technical problem to be achieved by the present invention is to solve the above problems, to provide a method for producing Fe-Si magnetic powder by crushing and classifying the Fe-Si alloy of Si content of 4wt% or more, spheroidized by RF plasma and quenched will be.

In addition, the technical problem to be achieved by the present invention is to provide a Fe-Si magnetic powder prepared by the above manufacturing method to be spherical, miniaturized and do not form a B2 phase, DO ₃ phase.

The technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. There will be.

In order to achieve the above technical problem, an embodiment of the present invention comprises the steps of preparing a Fe-Si alloy having a Si content of 4.0 to 9.0wt%; Pulverizing and then crushing the prepared alloy; Classifying the crushed and pulverized alloy; And spheroidizing and quenching the classified alloy by using an RF plasma.

In one embodiment of the present invention, the Fe-Si alloy may be a Si content of 5.0 to 8.0wt%.

In one embodiment of the present invention, the preparing of the Fe-Si alloy may include a process of manufacturing an ingot of the alloy by a vacuum arc remelting process.

In one embodiment of the present invention, the step of crushing the prepared alloy may be to use the brittleness of Si in the Fe-Si alloy.

In one embodiment of the present invention, the step of crushing the prepared alloy after crushing may include a process of being crushed and crushed by a ball mill, jet mill, attrition mill or planetary mill.

In one embodiment of the present invention, the step of classifying the crushed and pulverized alloy may be to classify the alloy particles having an average particle diameter of less than 50㎛.

In one embodiment of the present invention, the step of spheroidizing and quenching the classified alloy using an RF plasma comprises: generating an RF plasma in an inert gas atmosphere chamber; Injecting the classified powder into the chamber; And quenching the powder spherical by the RF plasma while passing through the chamber.

In one embodiment of the present invention, the temperature of the RF plasma may be 3,000 to 10,000K.

In one embodiment of the present invention, the step of injecting the classified powder in the chamber may be to inject the powder at a rate of 5 to 20g / min.

In one embodiment of the present invention, the step of quenching the spheroidized powder by the RF plasma while passing through the chamber is performed by applying a DC voltage to the spheroidized powder while exposing the spherical powder to the quench gas. Can be.

In order to achieve the above technical problem, another embodiment of the present invention provides a Fe-Si magnetic powder prepared by the manufacturing method.

In another embodiment of the present invention, the Fe-Si magnetic powder may have a purity of 99% or more and a spheroidization rate of 95% or more.

According to the embodiment of the present invention, by providing the Fe-Si magnetic powder with excellent workability while showing the properties of the ideal soft magnetic alloy, there is an effect that can be manufactured high-functional precision parts.

The effects of the present invention are not limited to the above-described effects, but should be understood to include all the effects deduced from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a flow chart showing a method of manufacturing Fe-Si magnetic powder according to an embodiment of the present invention.
2 is a flowchart illustrating a step of spheroidizing and quenching the Fe—Si alloy using RF plasma according to an embodiment of the present invention.
Figure 3 is a graph showing the phase change with the temperature of the Fe-Si alloy.

Hereinafter, with reference to the accompanying drawings will be described the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to be "connected (connected, contacted, coupled) with another part, it is not only" directly connected "but also" indirectly connected "with another member in between. "Includes the case. In addition, when a part is said to "include" a certain component, it means that it may further include other components, without excluding the other components unless otherwise stated.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprise" or "have" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present disclosure does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, the manufacturing method of Fe-Si magnetic powder is demonstrated.

Referring to Figure 1, an embodiment of the present invention comprises the steps of preparing a Fe-Si alloy having a Si content of 4.0 to 9.0wt% (S100); Grinding the prepared alloy and then grinding (S200); Classifying the crushed and pulverized alloy (S300); And spheroidizing and quenching the classified alloy using RF plasma (S400).

The step S100 may include a process of manufacturing an ingot of the alloy by a vacuum arc remelting process.

Vacuum Arc Remelting (VAR) refers to a method of casting primary refined metal in the form of a thin electrode and then melting it sequentially from the tip of the electrode when the arc is generated in a water-cooled mold in a vacuum chamber and dropping it into the mold. . Since the process of degassing, etc. during the dropping, there is an advantage that the degree of refinement is increased, it is used for dissolving high-strength metals having a high melting point.

Fe-Si alloy having a Si content of 4.0 to 9.0wt% has a problem in that cold rolling is difficult due to the brittleness of Si. In the present invention, the density of the powder core can be increased by miniaturizing this and spheroidizing using RF plasma. More specifically, the Fe-Si alloy may be a Si content of 5.0 to 8.0wt%.

The step of crushing the alloy prepared in step S200 may be to use the brittleness of Si in the Fe-Si alloy. The Fe-Si alloy having a Si content of 4.0 to 9.0 wt% is very brittle of Si, and thus is easily broken by lattice expansion in the ingot state. When the lattice expansion becomes severe, the ingot is broken and broken into large pieces, and the higher the content of Si, the brittle becomes stronger. You can choose the content of.

The step S200 may include a process of being crushed and crushed by a ball mill, a jet mill, an attention mill or a planetary mill. The crushing and grinding may be performed simultaneously by the above-described milling apparatus, or the milling may be performed by preparing an alloy crushed into relatively large pieces before adding the milling apparatus. If necessary, more than one milling device may be used. For example, the ingot is crushed by a hammer mill, and the crushed product is put into a jet mill to carry out grinding. The size of the powder in the hammer mill may be determined according to the rotational speed of the hammer and the size of the screen mesh. The milling apparatus described above is illustrative and not limited thereto.

The step S300 may be to classify the alloy particles having an average particle diameter of less than 50 μm. In the prior art, the powder prepared by gas or water yarn had an average particle diameter of 50 to 100 μm, but it was spherical but limited in packing density. In addition, the powder in the above range had a problem of low yield when performing the MIM for higher density. In the present invention, by using an alloy particle having an average particle diameter of less than 50 μm as a powder for spheroidizing by performing an RF plasma, it is possible to provide a powder having a much higher packing density while increasing the yield. Classification may be performed using a centrifugal classifier, air classifier, wet classifier, etc. The classification apparatus is exemplary and is not limited thereto.

When using the jet mill in the step S200 can be performed simultaneously to the step S300 according to the speed of the classifier (rotator). As the speed of the rotating body increases, the average particle diameter of the pulverized alloy powder tends to decrease, and by using this, the speed of the rotating body having an average particle diameter of less than 50 µm can be selected to simultaneously perform grinding and classification.

Referring to FIG. 2, the step S400 may include generating an RF plasma in an inert gas atmosphere chamber (S410); Injecting the classified powder into the chamber (S420); And quenching the powder spheroidized by the RF plasma while passing through the chamber (S430).

The temperature of the RF plasma in step S410 may be 3,000 to 10,000K. Refining using the RF plasma is an important step for high purity and spheroidization of the alloy powder. The temperature of the RF plasma can be determined by the power consumption of the heat source, and affects the purity and sphericity of the alloy powder. If less than 3,000K may not be sufficiently spheroidized, if it exceeds 10,000K is not preferable because the power consumption of the heat source is excessive because the economic efficiency worsens.

The step S420 may be to add the powder at a rate of 5 to 20g / min. The feed rate of the powder may affect the average particle diameter of the prepared Fe-Si alloy powder. The lower the feed rate, the larger the average particle size, and the higher the feed rate, the smaller the average particle size. The above range is critical in terms of formability of the resulting Fe-Si alloy powder. If it exceeds the above range it may be difficult to achieve sufficient purity and high density.

The step S430 may be performed by applying a DC voltage to the spherical powder while exposing the spherical powder to a quench gas.

Slow cooling of the spheroidized powder causes a problem of deterioration due to the formation of B2 phase and DO ₃ phase. Referring to FIG. 3, when the Fe-Si alloy powder having an alloy ratio of the present invention is slowly cooled after RF plasma, B2 and DO ₃ phases are formed along the right region indicated by a blue line in FIG. 3 (b). Therefore, in the present invention, Fe-Si powder is prepared by the method of rapid cooling after the RF plasma.

The quench gas may be argon, hydrogen or a mixture thereof. When the RF plasma is generated and two or more holes are drilled through the powder passing through the RF plasma in the chamber in which the alloy powder is introduced and the quench gas is supplied through the RF plasma, the temperature is different from the temperature of the quench gas itself. The temperature at which the powder is received can be relatively low to obtain a quenching effect. The quenching effect may be adjusted by independently controlling the flow rate of the argon or hydrogen, and the quenching effect may be increased by separately flowing cooling water into the supply pipe of the quenching gas. By adjusting the height of the perforation hole can be designed by optimizing the temperature distribution inside the chamber and thus the purity and sphericity of the final powder can be adjusted.

The electrode plate may be installed together at a position where the quench gas is supplied to quench the gas by applying a DC voltage to the powder passing through the RF plasma. The electrode plate is applied with a negative voltage. Since the RF plasma maintains a high temperature due to the collision between ions and neutrons, when the ion density decreases due to the negative voltage, the plasma temperature decreases rapidly.

The quenching effect can be enhanced by simultaneously using the method of using the quench gas and the method of applying the DC voltage.

Another embodiment of the present invention provides a Fe-Si magnetic powder prepared by the above production method. The Fe-Si magnetic powder may have a purity of 99% or more and a spheroidization rate of 95% or more.

Hereinafter, the present invention will be described in more detail with reference to specific preparation examples.

<Manufacture example 1>

An Si—6.5 wt% Fe—Si alloy was prepared in an ingot by vacuum arc remelting. The ingot was crushed with a hammer mill and the crushed product was put into a jet mill and pulverized. The rotor speed of the jet mill was 12,000 rpm and the average particle diameter of the pulverized alloy was 20 µm. RF plasma was generated in the RF plasma chamber, and the alloy powder having an average particle diameter of 20 μm was introduced at a rate of 10 g / min. Argon was supplied as a quench gas to the lower part of the chamber so that the alloy powder passed through the RF plasma was quenched. The quenched powder was captured to prepare Fe-Si magnetic powder.

<Manufacture example 2>

A magnetic powder of Fe-Si was prepared in the same manner as in Preparation Example 1, except that Fe-Si alloy having a Si content of 4.0 wt% was used.

<Manufacture example 3>

A magnetic powder of Fe-Si was prepared in the same manner as in Preparation Example 1, except that Fe-Si alloy having a Si content of 9.0 wt% was used.

Comparative Example 1

Fe-Si magnetic powder was prepared in the same manner as in Preparation Example 1, except that an Fe-Si alloy having a Si content of 3.0 wt% was used.

Comparative Example 2

A magnetic powder of Fe-Si was prepared in the same manner as in Preparation Example 1, except that the Fe-Si alloy having a Si content of 10.0 wt% was used.

Comparative Example 3

The Fe-Si magnetic powder was prepared in the same manner as in Preparation Example 1, except that the alloy powder passed through the RF plasma was not quenched.

The purity and sphericity of the Fe-Si magnetic powder prepared in Preparation Examples 1 to 3 and Comparative Examples 1 to 3 were measured and shown in Table 1 below.

division Si content (wt%) Quenching water(%) Nodularity (%) Preparation Example 1 6.5 O 99.5 96.0 Preparation Example 2 4.0 O 99.1 95.6 Preparation Example 3 9.0 O 99.2 95.1 Comparative Example 1 3.0 O 94.7 94.7 Comparative Example 2 10.0 O 95.5 94.3 Comparative Example 3 6.5 X 93.1 95.5

According to Table 1, the Fe-Si magnetic powder according to Preparation Examples 1 to 3 of the present invention satisfies a condition of purity of 99% or more and sphericity of 95% or more, but the Fe-Si magnetic powder according to Comparative Examples 1 to 3 It can be seen that the purity and sphericity of the silver is inferior. The above description of the present invention is for illustration, and those skilled in the art to which the present invention pertains can change the technical spirit or essential features of the present invention without changing the technical spirit or essential characteristics of the present invention. It will be appreciated that the modification can be easily made in specific forms. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is represented by the following claims, and it should be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention.

Claims (12)

Preparing a Fe—Si alloy having a Si content of 4.0 to 9.0 wt%;
Pulverizing and then crushing the prepared alloy;
Classifying the crushed and pulverized alloy; And
And spheroidizing and quenching the classified alloy using an RF plasma.
The method of claim 1,
The Fe-Si alloy is a method of producing a Fe-Si magnetic powder, characterized in that the Si content of 5.0 to 8.0wt%.
The method of claim 1,
The preparing of the Fe-Si alloy includes a process of manufacturing an ingot of the alloy by a vacuum arc remelting process.
The method of claim 1,
The crushing of the prepared alloy is Fe-Si magnetic powder manufacturing method characterized in that using the brittleness of Si in the Fe-Si alloy.
The method of claim 1,
The pulverizing and then crushing the prepared alloy is a method of producing a Fe-Si magnetic powder, characterized in that it comprises a process of being crushed and crushed by a ball mill, jet mill, attrition mill or planetary mill.
The method of claim 1,
The classifying the crushed and pulverized alloy is a method for producing a Fe-Si magnetic powder, characterized in that for classifying the alloy particles having an average particle diameter of less than 50㎛.
The method of claim 1,
The spheroidizing and quenching of the classified alloy using RF plasma,
Generating an RF plasma in an inert gas atmosphere chamber;
Injecting the classified powder into the chamber; And
Method for producing a Fe-Si magnetic powder characterized in that it comprises the step of quenching the powder spheroidized by the RF plasma while passing through the chamber.
The method of claim 7, wherein
The temperature of the RF plasma is a manufacturing method of Fe-Si magnetic powder, characterized in that 3,000 to 10,000K.
The method of claim 7, wherein
The step of injecting the classified powder into the chamber is a method for producing Fe-Si magnetic powder, characterized in that the powder is added at a rate of 5 to 20g / min.
The method of claim 7, wherein
The step of quenching the powder spheroidized by the RF plasma while passing through the chamber is performed by applying a DC voltage to the spheroidized powder while exposing the spheroidized powder to the quench gas. Manufacturing method.
Fe-Si magnetic powder prepared by the method according to claim 1.
The method of claim 11,
The Fe-Si magnetic powder has a purity of 99% or more and a spheroidization rate of 95% or more.

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