KR102007898B1 - Soft magnetic powders for inductor core and method for manufacturing of the same - Google Patents

Abstract

The present invention relates to a soft magnetic powder for an inductor core and a method of manufacturing the same.
One embodiment of the present invention is for inductor cores, including Si: 0.5 to 6.5% by weight, Cr: 0.5 to 4.0% by weight, B: 0.1 to 1.0% by weight, balance Fe and other unavoidable impurities Provide a soft magnetic powder.

Description

Soft magnetic powder for inductor core and its manufacturing method {SOFT MAGNETIC POWDERS FOR INDUCTOR CORE AND METHOD FOR MANUFACTURING OF THE SAME}

One embodiment of the present invention relates to a soft magnetic powder and a preparation method thereof.

As the development of hybrid and electric vehicle (HEV / EV) technologies is becoming important, the characteristics of the inductor core for power conversion are also a major factor. Among them, high saturation magnetic flux density, current superimposition characteristics, and low iron loss are the most essential requirements for driving hybridization of vehicles.

In Japan, where a lot of previous research is being conducted on electric and hybrid vehicles, studies on inductor cores for power conversion using powder cores are being actively conducted. In addition, the trend is to apply the powder core product to the actual vehicle.

The alloy composition of the powder for inductor cores which is conventionally used is Fe-6.5wt.% Si, and shows excellent characteristics of saturation flux density of 1.6T or more and permeability of 60μ. However, the commercial powder has a problem in that the process cost is high by preparing the powder by the gas injection method. In addition, in accordance with the continuous demand for high-efficiency electric vehicles, it is necessary to improve the magnetic flux density.

Therefore, in one embodiment of the present invention, it is necessary to apply a method having a higher magnetic flux density than a conventional commercial powder and a lower process cost compared to gas injection.

The Fe-Si-B-Cr-based soft magnetic powder may be manufactured by a water spray method, but a soft magnetic powder for an inductor core having surface oxidation of the powder suppressed may be provided. Accordingly, it is possible to increase the price competitiveness by omitting the reduction step.

In addition, even if manufactured by the water spray method to provide a soft magnetic powder for the inductor core having the same sphericity at the time of gas injection and manufacturing.

Soft magnetic powder for an inductor core, which is an embodiment of the present invention, is based on 100 wt% Si: 0.5 to 6.5 wt%, Cr: 0.5 to 4.0 wt%, B: 0.1 to 1.0 wt%, balance Fe and other unavoidable impurities It may include.

The surface roughness of the soft magnetic powder for the inductor core may be 0.9 or more.

The oxygen concentration may be 0.5 wt% or less with respect to 100 wt% of the soft magnetic powder for the inductor core.

An oxide layer may be positioned on a surface of the soft magnetic powder for the inductor core, and the thickness of the oxide layer may be 1 μm or less.

The average particle diameter of the soft magnetic powder for the inductor core may be 30 to 50㎛.

The average grain size of the soft magnetic powder for the inductor core may be 200 to 500 nm.

The grain boundary of the soft magnetic powder for the inductor core may have a higher chromium content than the grain size.

In another embodiment, a method of manufacturing a soft magnetic powder for an inductor core may include Si: 0.5 to 6.5% by weight, Cr: 0.5 to 4.0% by weight, B: 0.1 to 1.0% by weight, and the balance relative to 100% by weight. Preparing an alloy molten metal including Fe and other unavoidable impurities, preparing a powder by water spraying the alloy molten metal, drying and heat-treating the prepared powder, and insulating coating the heat-treated powder surface. It may include.

In the step of producing a powder form by water spraying the molten alloy, the collision angle of the molten alloy and the water spray nozzle may be 30 to 50 °.

In the step of insulation coating the heat treated powder surface, the powder surface may be insulation coated with an aqueous sodium silicate solution. Specifically, the insulating coating may be performed by 100 parts by weight to 1 to 10 parts by weight of the powder.

By controlling the composition and composition of the alloy, it is possible to provide a soft magnetic powder for the inductor core is suppressed surface oxidation and excellent in roughness.

Specifically, surface oxidation of the soft magnetic powder for the inductor core can be suppressed through the addition of the Cr component. On the other hand, the addition of the Si and B components to improve the viscosity of the melt and to refine the crystal grains, it is possible to reduce the eddy current loss during the core molding.

1 is a result of observing the soft magnetic powder for the inductor core according to the embodiment by SEM.
Figure 2 is a result of observing the cross-sectional microstructure of the soft magnetic powder for the inductor core according to the embodiment by TEM.
3 is a graph illustrating a change in the average particle diameter of the powder produced according to the angle between the molten alloy and the water spray nozzle in the method of manufacturing the soft magnetic powder for the inductor core according to the embodiment of the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be embodied in various different forms, and the present embodiments merely make the disclosure of the present invention complete, and are common in the art to which the present invention pertains. It is provided to fully inform those skilled in the art of the scope of the invention, which is to be defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Thus, in some embodiments, well known techniques are not described in detail in order to avoid obscuring the present invention. Unless otherwise defined, all terms used in the present specification (including technical and scientific terms) may be used as meanings that can be commonly understood by those skilled in the art. When any part of the specification is to "include" any component, this means that it may further include other components, except to exclude other components unless otherwise stated. In addition, singular forms also include the plural unless specifically stated otherwise in the text.

Soft magnetic powder for inductor core according to an embodiment of the present invention, Si: 0.5 to 6.5% by weight, Cr: 0.5 to 4.0% by weight, B: 0.1 to 1.0% by weight, balance Fe and It may contain other unavoidable impurities.

Hereinafter, the reason which limited the component and the composition of the said powder is demonstrated.

Fe is a metal having the highest magnetic flux density, and the magnetic flux density gradually decreases as alloying elements are included in pure iron. However, since pure iron has a very low resistivity and a very large eddy current loss, it may be desirable to use an alloy in spite of a low magnetic flux density.

Specifically, the loss is composed of eddy current loss and hysteresis loss, and since the hysteresis loss is a negligible level due to the small composition difference in the same metal.

Therefore, the alloy element is added to reduce the saturation magnetic flux density and to reduce the loss due to the increase in the resistivity.

Specific alloy elements are as follows.

First, the content of Si may be 0.5 to 6.5% by weight.

Si serves to reduce grain anisotropy. In addition, it also serves to improve the viscosity of the molten alloy in the soft magnetic powder manufacturing step for the inductor core to be described later. When the viscosity of the molten metal is improved by the addition of Si, water may be sprayed onto the molten metal to prepare a powder having excellent surface roughness during powder preparation. Powders with good surface roughness can reduce losses by minimizing friction between powders when forming inductor cores.

Therefore, when the content of Si is in the above range, it is possible to reduce the eddy current loss. However, when the content of Si exceeds 6.5% by weight, the eddy current loss may increase again.

In addition, the content of Cr may be 0.5 to 4.0% by weight.

Cr may suppress the surface oxidation of the powder that may occur during the water spraying process in the step of manufacturing the soft magnetic powder for the inductor core described later. Specifically, Cr forms a thin oxide film on the surface of the powder and serves to suppress further oxidation.

Therefore, when the Cr content is in the above range, oxidation can be suppressed as much as possible. That is, the oxygen concentration in the soft magnetic powder for the inductor core can be reduced. However, when the content exceeds 4.0% by weight, the hardness of the powder may be increased, thereby making core molding difficult. In addition, the permeability can be lowered.

The content of B may be 0.1 to 1.0% by weight.

B serves to inhibit oxidation and improve mechanical properties through grain refinement. In addition, it also serves to improve the viscosity of the molten alloy in the soft magnetic powder manufacturing step for the inductor core to be described later. In addition, B may improve hardenability of the iron-based alloy.

Thus, when including as much as the above range may be excellent in the strength of the magnesium alloy plate. However, when it exceeds 1% by weight, core molding may be difficult due to the increase in hardness of the powder.

Accordingly, the surface roughness of the soft magnetic powder for the inductor core may be 0.9 or more.

Hereinafter, in this specification, roughness (convexity) means the degree of curvature of the powder surface.

Therefore, the surface roughness (convexity) of the soft magnetic powder for the inductor core is 0.9 or more means that the powder is in the form of a sphere. This means that the sphericity is high. Specifically, when the surface roughness of the soft magnetic powder for the inductor core is in the above range, the powder may have a regular shape. As a result, when the inductor core is formed using the powder, the friction between the powders is small, so that the eddy current loss can be reduced.

As will be described later, the surface roughness of the soft magnetic powder for the inductor core may be due to the viscosity of the molten alloy.

In addition, the average particle diameter of the soft magnetic powder for the inductor core may be 30 to 50㎛.

Specifically, as the average particle diameter of the soft magnetic powder for the inductor core is smaller, the eddy current loss in which the square of the area is proportional to be managed lower. Therefore, by controlling the average particle diameter of the soft magnetic powder for the inductor core according to the embodiment of the present invention as described above, the eddy current loss can be reduced.

More specifically, the particle diameter of the powder may be determined by various factors, as disclosed in the following relational formula 1.

------관계식 (1)

------ Relationship (1)

In this relation (1), P _w is the spray water pressure (water injection pressure), WMR (Water to melt flow ratio) is the ratio of water and the melt, α is the collision angle between the melt and the water nozzle, k Means the inner diameter of the melt nozzle.

Specifically, the particle diameter of the soft magnetic powder may be smaller as the water injection pressure, the ratio of water and molten metal, and the collision angle between the molten metal and the water jet nozzle are larger. On the other hand, the smaller the inner diameter of the melt nozzle may be a finer particle diameter.

However, the water injection pressure, the ratio of water and the melt, and the inner diameter of the melt nozzle may be fixed at the process design stage. Thus, the particle size control of the soft magnetic powder may be possible through the collision angle between the molten metal and the water spray nozzle.

In this regard, a more detailed description will be made in the method of manufacturing the soft magnetic powder for the inductor core.

The oxygen concentration may be 0.5 wt% or less with respect to 100 wt% of the soft magnetic powder for the inductor core manufactured as described above.

Specifically, an oxide layer is located on the surface of the soft magnetic powder for the inductor core, the thickness of the oxide layer may be 1㎛ or less.

The soft magnetic powder of the above oxygen concentration is a low level in the powder produced through the water spray method. This may be due to the microstructure of the soft magnetic powder.

Specifically, the average grain size of the soft magnetic powder for the inductor core may be 200 to 500nm.

More specifically, when the average grain size of the soft magnetic powder for the inductor core is within the above range, the oxygen concentration in the powder may be low as described above.

In addition, the grain refinement of the powder may be due to the cooling rate in the water spraying step and grain refinement by addition of boron.

The grain boundary of the soft magnetic powder for the inductor core may have a higher chromium content than the grain size. As a result, the powder may be excellent in the antioxidant effect.

In another embodiment, a method of manufacturing a soft magnetic powder for an inductor core may include Si: 0.5 to 6.5% by weight, Cr: 0.5 to 4.0% by weight, B: 0.1 to 1.0% by weight, and the balance relative to 100% by weight. Preparing an alloy molten metal containing Fe and other unavoidable impurities, preparing a powder by water spraying the alloy molten metal, drying and heat-treating the prepared powder, and insulating coating the heat-treated powder surface. It may include.

First, the reason for limiting the components and the composition of the molten alloy in the step of preparing the molten alloy is omitted in the soft magnetic powder for the inductor core as described above.

Thereafter, in the step of producing a powder by water spraying the molten alloy, the collision angle between the alloy melt and the water spray nozzle may be 30 to 50 °.

Specifically, when the collision angle between the molten alloy and the water spray nozzle in the water spraying range is the above range, the average particle diameter of the powder produced may be the finest. More specifically, when the impingement angle exceeds 50 °, the molten alloy may flow backward to cause the melt now forming and nozzle clogging.

Therefore, as the angle between the molten alloy and the water spray nozzle increases, the average particle diameter of the powder may also decrease, but the collision angle may be in the above range for the aforementioned reasons.

In addition, there may be little change in the average particle diameter of the powder at the collision angle of 40 to 50 °. Thus, other process variables may be needed to further control the average particle diameter of the powder.

In addition, in the step of producing a powder by water spraying the molten alloy, the water spray pressure may be in the range of 100 to 1000bar. The water injection amount may be 100 to 500 L / min. However, it is not limited thereto.

After preparing the powder by water spraying the molten alloy, a rust preventive agent may be added to the powder produced by water spraying.

The rust inhibitor may be silicate, zinc chromate, or a combination thereof. However, the present invention is not limited thereto, and any material that inhibits oxidation of the surface of the powder may be used. Specifically, it may be added in 1 to 5 parts by weight based on 100 parts by weight of the powder. In the above weight range, oxidation of the surface of the powder can be effectively suppressed.

In the drying and heat-treating the prepared powder, the drying may be dried for 1 to 3 hours in a temperature range of 50 to 100 ℃. This is to remove moisture on the surface of the powder made of water yarn. However, it is not limited thereto.

In addition, heat processing can be performed in nitrogen atmosphere. Specifically, annealing (heat treatment) may be performed for 1 to 3 hours in a temperature range of 300 to 500 ° C. By heat treatment under the above conditions, it is possible to remove the stress inside the powder generated in the water spraying step.

In the step of insulating coating the heat-treated powder surface, the surface of the powder may be coated using an aqueous sodium silicate solution.

Specifically, the soft magnetic powder for the inductor core may be subjected to the insulation coating as described above to reduce the losses that may occur during the core molding.

More specifically, it may be coated with 1 to 10 parts by weight insulation coating agent based on 100 parts by weight of the powder. However, it is not limited thereto.

Hereinafter, the embodiment will be described in detail. However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited by the following examples.

Example

A soft magnetic powder was prepared by water-spraying an alloy molten metal including Si: 3.5% by weight, Cr: 2.0% by weight, B: 0.1% by weight, balance Fe, and other unavoidable impurities.

At this time, the water injection pressure was 150bar, the injection flow rate was 100L / min. The water spray nozzle used a conic jet type. In addition, the collision angle of the said molten alloy and water spray nozzle was 40 degrees. Specifically, the molten nozzle is a quartz material having an internal diameter of 7mm.

Further, 2 parts by weight of a rust preventive agent was added to 100 parts by weight of the soft magnetic powder.

The powder was then dried at 80 ° C. for 2 hours.

The dried powder was annealed at 400 ° C. for 2 hours in a nitrogen atmosphere.

Finally, with respect to 100 parts by weight of the soft magnetic powder, 5 parts by weight of water glass was added to perform insulation coating.

Comparative example

In comparison with the examples, soft magnetic powder was prepared under the same conditions except that it did not contain chromium.

Experimental Example

In order to evaluate the magnetic properties of the soft magnetic powders prepared in Examples and Comparative Examples, a core was prepared using the powder.

Specifically, the core was manufactured by molding the coated powder using a ring-shaped core press having an outer diameter of 28 mm, an inner diameter of 14 mm, and a height of 12 mm. At this time, the molding pressure is 18ton / cm ² . Finally, the molded cores were annealed at 400 ° C. for 2 hours in a nitrogen atmosphere. Basic magnetic properties were evaluated through the copper wire winding.

Example Comparative example Saturated magnetic flux density (T) 1.65 1.6 Permeability (μ) 48 44 Convexcity 0.92 0.99

As a result, it can be seen that the saturation magnetic flux density and permeability of the powder according to the comparative example not containing chromium are inferior to those of the examples.

This can also be confirmed through the drawings of the present invention.

1 is a result of observing the soft magnetic powder for the inductor core according to the embodiment by SEM.

As shown in FIG. 1, it can be seen that the roughness of the soft magnetic powder for the inductor core according to the embodiment is spherical to approximately 1. In addition, it can be seen that the average particle diameter of the soft magnetic powder is about 40㎛ level.

Figure 2 is a result of observing the cross-sectional microstructure of the soft magnetic powder for the inductor core according to the embodiment by TEM.

As shown in Figure 2, it can be seen that the average grain size of the soft magnetic powder for the inductor core according to an embodiment of the present invention is 200 to 500nm level.

In addition, the dark region of the grain boundary portion is a chromium-rich (Cr-rich) region. Accordingly, it can be derived that the oxygen concentration of the soft magnetic powder for the inductor core may be low.

3 is a graph illustrating a change in the average particle diameter of the powder produced according to the angle between the molten alloy and the water spray nozzle in the method of manufacturing the soft magnetic powder for the inductor core according to the embodiment of the present invention.

In one embodiment of the present invention, the angle between the molten alloy and the water spray nozzle is limited to 30 to 50 °. As shown in Figure 3, it can be seen that the average particle diameter of the soft magnetic powder produced when the collision angle is in the above range is 30 to 50㎛.

This can be confirmed through the result that the average particle diameter of the soft magnetic powder for the inductor core according to the embodiment of the present invention in FIG.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that.

Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. .

Claims (11)

A soft magnetic powder for an inductor core comprising Si: 0.5 to 6.5% by weight, Cr: 0.5 to 4.0% by weight, B: 0.1 to 1.0% by weight, other unavoidable impurities and the balance Fe.
In claim 1,
The surface roughness of the soft magnetic powder for the inductor core is 0.9 or more soft magnetic powder for the inductor core.
In claim 2,
The soft magnetic powder for inductor core having an oxygen concentration of 0.5 wt% or less with respect to 100 wt% of the soft magnetic powder for inductor core.
In claim 3,
An oxide layer is located on the surface of the soft magnetic powder for the inductor core,
Soft magnetic powder for the inductor core thickness of the oxide layer is 1㎛ or less.
In claim 4,
Soft magnetic powder for the inductor core is an average particle diameter of 30 to 50㎛ soft magnetic powder for the inductor core.
In claim 5,
An average grain size of the soft magnetic powder for the inductor core is 200 to 500nm soft magnetic powder for the inductor core.
In claim 6,
The grain boundaries of the soft magnetic powder for the inductor core is soft magnetic powder for the inductor core having a higher chromium content than the grain size.
Preparing an alloy molten metal including Si: 0.5 to 6.5% by weight, Cr: 0.5 to 4.0% by weight, B: 0.1 to 1.0% by weight, other unavoidable impurities and the balance Fe;
Preparing a powder by spraying water on the molten alloy;
Drying and heat-treating the prepared powder; And
Method for producing a soft magnetic powder for the inductor core comprising the step of insulating coating the heat treated powder surface.
In claim 8,
In the step of producing a powder form by water spraying the molten alloy,
Method of producing a soft magnetic powder for the inductor core collision angle between the molten alloy and the water spray nozzle is 30 to 50 °.
In claim 8,
Insulating coating the heat treated powder surface,
Method for producing a soft magnetic powder for the inductor core for insulating coating the powder surface with an aqueous sodium silicate solution.
In claim 10,
Insulating coating the heat treated powder surface,
Method for producing a soft magnetic powder for inductor core which is coated with 1 to 10 parts by weight of sodium silicate aqueous solution based on 100 parts by weight of the powder.

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