KR101387961B1 - Iron based nanocrystalline soft magnetic alloy powder cores and preparation thereof - Google Patents

Abstract

The present invention relates to a nanocrystalline soft magnetic alloy powder core having a composition in which calcium (Ca) is added to an iron (Fe) based alloy and a method for producing the same. The nanocrystalline soft magnetic alloy powder core according to the present invention comprises iron (Fe) A method of manufacturing an amorphous alloy ribbon, comprising the steps of: adding calcium (Ca) to a base alloy to produce an amorphous alloy ribbon; grinding the amorphous alloy ribbon to form an amorphous alloy powder; classifying the amorphous alloy powder formed; Forming a powder core by pressurizing the powder mixed with the binder, and heat treating the formed powder core for nanocrystallization.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an iron-based nano-crystal soft magnetic alloy powder core and an iron-

The present invention relates to an Fe-based soft magnetic alloy powder core having good magnetic properties, particularly excellent core loss properties, and a method for producing the same.

Recently, due to the advancement of the industry, products in almost all fields are making rapid progress in the direction of high precision, high performance, and miniaturization. Particularly, electric and electronic devices including computers are becoming a necessity of high efficiency, small size, and light weight, and researches for developing soft magnetic materials suitable for these products have been actively promoted around the world, and some of them have already been put to practical use.

Examples of the material for the powder cores using the conventional powder metallurgy method include Ni-Fe permalloy alloys and Fe-Si-Al Sendust alloys. In recent years, studies have been made to utilize Fe-based amorphous alloys and nanocrystalline alloys or powders as materials for powder cores to form cores in terms of application technology development of soft magnetic materials.

Generally, the electric steel sheet has a saturation magnetic flux density as high as 2.0 T, but the saturation magnetic flux density starts to decrease sharply at a high frequency range of 1 kHz or more and its characteristics become very poor. In recent years, studies on powder molding composites having excellent magnetic permeability, saturation magnetic flux density and core loss characteristics in a high frequency region of 1 kHz or more and 1 MHz or less, which can replace electric steel sheets having low characteristics in a high frequency region, have been actively conducted.

The powder-formed composite has magnetic and thermal isotropy, has very low eddy current loss from low frequency to high frequency, relatively low loss, high magnetic permeability, high saturation magnetization value, high resistance, low inherent coercivity and high Curie temperature .

In addition, powdered composites have many advantages over existing laminated steel sheets. Powder forming composites have the advantages of three-dimensionally uniform soft magnetic properties, flexible design and assembly characteristics, very low eddy current loss, weight and cost reduction compared to existing laminated electrical steel sheet cores. In the case of nanocrystalline alloy ribbon cores, there are disadvantages of heat treatment and strip shorting at the time of ribbon winding, high production cost, limited range of use compared to amorphous alloys, and low reproducibility of magnetization characteristics, . In contrast, nanocrystalline powder can compensate for the disadvantages of nanocrystalline alloys.

Nanocrystalline soft magnetic alloys have higher saturation magnetization and higher magnetic permeability than amorphous alloys and have low magnetic deformation and low core loss as well as high frequency characteristics and are expected to be widely used for power conversion, energy storage materials and transformers.

Regarding this, Korean Patent Registration No. 531253 discloses a method for producing an amorphous ribbon having a composition of Fe _73.5 Cu ₁ Nb ₃ Si _13.5 B ₉ prepared by the rapid coagulation method (RSP method) by heat treating the amorphous ribbon at 540 ° C. for 40 minutes under a nitrogen atmosphere, Discloses a method of forming an annular core by mixing 3% by weight of a low melting point glass into a nanocrystalline powder obtained by pulverizing and classifying the nanocrystalline ribbon with a pulverizer.

In addition, Korean Patent Registration No. 721501 of the present applicant discloses an amorphous alloy ribbon of a composition Fe ₇₃ -Si ₁₆ -B ₇ -Nb ₃ -Cu ₁ (at%) prepared by a rapid coagulation method (melt spinning method) , Preferably 300-450 占 폚, for 1 hour, and then pulverized, and then a binder of a polyimide resin is mixed to prepare a core.

Korean Patent Application Laid-Open No. 2011-0071021 discloses a Fe-based soft magnetic alloy capable of obtaining low core loss and high direct current superimposition characteristics, and a powder core using the same, wherein Fe has an element R and the element R has P, C, B and Si and has a temperature difference of 20 占 폚 or more between the precipitation temperature of the? -Fe crystal phase and the precipitation temperature of the Fe compound, and is formed into a mixed phase structure of amorphous phase and? -Fe crystal phase , The crystallite diameter of the α-Fe crystal is 50 nm or less, and the volume fraction of the α-Fe crystal phase is 40% or less of the total.

Although studies on soft magnetic alloy powder have been actively conducted, there is a continuing need for a soft magnetic alloy having a better magnetic property, particularly a more excellent core loss property, of a high-frequency powder core.

Korean Patent No. 531253 Korea Patent No. 721501 Korean Patent Application Publication No. 2011-0071021

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a stable nanocrystalline soft magnetic material and a method of manufacturing the same, which can reduce the core loss of the powder molding composite.

In order to achieve the above object, the present invention provides a nanocrystalline soft magnetic alloy powder core having a composition in which calcium (Ca) is added to an iron (Fe) based alloy.

The present invention also relates to a method of manufacturing an amorphous alloy, comprising the steps of: preparing an amorphous alloy ribbon by adding calcium (Ca) to an iron (Fe) alloy; milling an amorphous alloy ribbon to form an amorphous alloy powder; Mixing the classified powder with a binder, molding the powdered core by pressurizing the powder mixed with the binder, and heat treating the formed powdered core for nanocrystallization of the powdered core, Of the present invention.

 The nanocrystalline soft magnetic alloy powder produced by the method of the present invention can be molded into an optimal nano-sized crystal structure to form a powder composite having excellent core loss. In addition, the nanocrystalline soft magnetic alloy powder cores not only have excellent magnetization properties, but also have a low high frequency core loss and miniaturization of parts.

According to the present invention, the amorphous alloy ribbon to which Ca is added increases the brittleness of the alloy ribbon due to the effect of Ca, thereby shortening the processing time in the crushing process, thereby lowering the production cost. In addition, since the molding density is high, the permeability does not change even in the high-frequency band, and the core-loss in the frequency band is low due to the excellent inter-powder insulating property, the alloy powder composite can be utilized on a large scale in electric and electronic devices in a high frequency band.

1 is a core loss value (Pcm) (core loss measurement condition: 50 kHz, 0.1 Tesla) according to a chemical composition of a nanocrystalline soft magnetic alloy powder composite according to an embodiment of the present invention and a heat treatment temperature.
FIG. 2 is a graph showing the core permeability (μ _a ) according to the chemical composition and the heat treatment temperature of the nanocrystalline soft magnetic alloy powder composite according to the embodiment of the present invention (permeability measurement condition: 10 kHz, 0.1 Tesla).

Hereinafter, a novel nanocrystalline soft magnetic alloy powder core according to the present invention and its manufacturing method will be described in detail.

The present invention provides a nanocrystalline soft magnetic alloy powder core having a composition in which calcium (Ca) is added to an iron (Fe) based alloy and a method of manufacturing the same.

The alloy used for the soft magnetic alloy powder core according to the present invention preferably contains Ca at 0.01 to 2 at% in Fe-Si-B-Nb-Cu (at%). More specifically, it includes 10 to 15 atomic percent of silicon (Si), 5 to 15 atomic percent of boron (B), 1 to 7 atomic percent of niobium (Nb), 0.5 to 3 atomic percent of copper (Cu) 2 at% and iron (Fe) as the other composition (at%). It is more preferable that the content of calcium (Ca) is 0.01 to 0.5 at%.

The soft magnetic alloy powder core according to the present invention comprises the steps of preparing an amorphous alloy ribbon by adding calcium (Ca) to an iron (Fe) based alloy, pulverizing the amorphous alloy ribbon to form an amorphous alloy powder, Comprising the steps of: classifying alloy powder, mixing the classified powder with a binder, pressing powder mixed with the binder to form a powder core, and heat treating the formed powder core for nanocrystallization ≪ / RTI >

According to a preferred embodiment of the present invention, when the alloy is molten and in a liquid state, rapid solidification can be performed at a rapid cooling rate of about 1,000,000 K / s so as not to form a rule of atomic crystal.

The amorphous alloy production method as it is in a liquid state is typically a manufacturing method by a single-roll method and a twin-roll method. In a preferred embodiment of the present invention, an Fe-based amorphous alloy ribbon is produced by a single-roll method. Although the production method using the mono-roll is widely used because it can produce a large number of strips having a wide width of 20 to 30 탆 in thickness although the shape of the strip is sensitively influenced by process parameters, the melt spinning process process.

The amorphous alloy ribbon may be made into a powder by a crushing process such as ball milling.

According to a preferred embodiment of the present invention, the method may further comprise preliminary heat treatment of the amorphous alloy ribbon prior to the step of forming the alloy powder for faster fracture. The preliminary heat treatment is preferably performed at 400 to 500 ° C. for 5 to 100 minutes. Reduction of process time due to preliminary heat treatment is advantageous for economical production process and cost reduction.

The step of classifying the amorphous alloy powder is to classify the powder so as to have a uniform optimum particle size.

The binder used in the production method of the present invention is preferably an aqueous solution of sodium silicate. The sodium silicate aqueous solution binder is preferably diluted with deionized water and then mixed with the classified amorphous powder and uniformly coated in liquid phase.

On the other hand, the binder used for preparing the amorphous alloy powder composite should have a lower softening point than the crystallization temperature of the amorphous alloy, and should have a proper bonding strength at room temperature so as to suppress cracking while maintaining the powder composite molding shape.

It is preferable that the aqueous solution of the silicate is uniformly dispersed. To this end, it is possible to facilitate mixing by adding deionized water to dilute it. The preferred aqueous solution concentration is 20 to 50% by weight.

The amorphous and nanocrystalline soft magnetic alloy powder using the sodium silicate binder has a characteristic of being relatively high in mechanical strength, high thermal and chemical stability and heat resistance. In addition, since the sodium silicate binder has a high combustion point, it is coated on the surface of the powder without burning even in the crystallization heat treatment process for preparing the amorphous alloy powder as the nanocrystalline alloy powder, and has good properties as a binder.

When the sodium silicate aqueous solution is uniformly coated on the surface of the powder, the resistivity is increased due to the insulating effect between the powder and the powder, thereby improving the magnetic properties such as the eddy current loss and the core loss (iron loss) reduction.

The amount of the binder to be mixed is preferably such that sodium silicate other than deionized water is used within 0.5 to 3% by weight of the total mass of the amorphous alloy powder. When the amount of the binder is less than 0.5% by weight, the bonding strength of the binder is low and the bonding strength with the powder is low, so bulk molding of the amorphous alloy powder is difficult. When the amount of the binder is more than 3% by weight, However, mixing of the powder and the binder becomes difficult, and the amount of the amorphous alloy powder in the amorphous alloy composite is decreased, so that the soft magnetic properties are lowered.

The powder mixed with the binder is pressed into a powder composite under a cold forming process. Specifically, after the solvent of the diluted binder is dried, a pressure of 25 to 40 ton / cm < ³ > is applied to the amorphous alloy powder composite in the pressing step for cold forming. If the forming pressure is too low, the density of the composite is lowered to deteriorate the strength and characteristics of the composite. If the molding pressure is too high, the wear of the die is accelerated, which shortens the life of the die and increases the production cost. If the molding process is performed without drying the solvent of the diluted binder, voids in the composite body are generated due to vaporization of the solvent during the crystallization heat treatment process, resulting in deterioration of characteristics.

The nanocrystallized powder composite may be heat treated at a temperature above the heat treatment initiation temperature to form nanocrystalline grains. It is preferable that the annealing step for forming nanocrystalline grains of the amorphous alloy powder composite molded into a bulk shape is heat-treated at a temperature not less than the crystal growth start temperature of 500 to 550 DEG C for 5 to 60 minutes.

 The heat treatment temperature for forming the nanocrystalline structure is preferably higher than the crystallization starting temperature (Tx) by 50 占 폚. Too high a heat treatment temperature results in a sudden coarsening of crystals, which degrades the binder and weakens the bonding force. Further, in order to improve the magnetic properties of the amorphous alloy powder composite, accumulation energy is generated in the powder during powder molding and processing. As a result, the crystallization starting temperature in the powder form is lower than the crystallization starting temperature (Tx) of the amorphous alloy ribbon The crystallization initiation temperature is lowered due to a somewhat lower temperature and a surface area that increases sharply than the ribbon state. Therefore, consideration should be given to lowering the crystallization temperature due to the above-mentioned accumulation energy relaxation and surface area increase, and the crystallization temperature condition of the nanocrystalline grains can be controlled in the heat treatment temperature range as described above to finally control the nanocrystal grain size. In addition, when the heat treatment process is performed under the above conditions, fine nanocrystalline grains of about 10 to 15 nm can be obtained and excellent soft magnetic characteristics can be expected.

Hereinafter, embodiments of the present invention will be described.

[Example]

Amorphous alloy ribbon of Fe ₇₃ -Si ₁₄ -B ₉ -Nb ₃ -Cu ₁ (at%) composition prepared by melt spinning and a ribbon prepared by adding 0.37 at% Ca to the alloy composition , Preliminarily heat-treated at 400 to 500 ° C for 90 minutes to obtain fine and uniform powder, and then ball milled for 10 hours at a rotating speed of 110 to 120 rpm to break the ribbon.

For the core molding of the amorphous alloy powder (average particle size of about 30 μm) obtained by the crushing process, 4.5 g of an aqueous solution of sodium silicate (concentration 33.3 wt%) diluted with deionized water was poured into 100 g of the crushed powder for about 5 hours, The composite powder was charged into the molding die at a room temperature of about 6 g and then cold-formed at a molding pressure of about 30 ton / cm ^{2 to obtain} a toroidal powder having an outer diameter of 17.28 mm, an inner diameter of 9.7 mm, and an average height of 6.27 mm ).

As the crystallization temperature of the Fe-based amorphous soft magnetic alloy powder thus prepared was measured at 521.3 ° C, the powder cores were heat-treated for 1 hour under a nitrogen atmosphere in a temperature range of 500-550 ° C for crystallization heat treatment.

[Comparative Example]

Powder cores were prepared in the same manner as in Example except that calcium was not added at all.

Characterization of powder cores

Particle sizes of the powders prepared in Examples and Comparative Examples were observed by SEM (Scanning Electron Microscope), and the grain sizes of the powders were observed by TEM (Transmission Electron Microscope).

Fig. 1 shows the core loss value (Pcm) according to the chemical composition and the heat treatment temperature of the nanocrystalline soft magnetic alloy powder composite according to the comparative example in which Ca and Ca were not added at all, 0.1 Tesla).

FIG. 2 is a graph comparing permeability characteristics according to temperature of cores prepared in Examples and Comparative Examples (permeability measurement condition: 10 kHz, 0.1 Tesla).

Referring to FIGS. 1 and 2, the Ca-containing Fe-based alloy exhibits excellent characteristics in which the core loss is reduced by about 20% as compared with the Fe-based alloy not containing Ca, and the permeability is reduced by about 10% It can be seen that the magnetization characteristics are improved.

Claims (7)

delete delete (1) At least one element selected from the group consisting of silicon (Si) 10 to 15 (at%), boron (B) 5 to 15 (at%), niobium (Nb) 1 to 7 (At%), copper (Cu) at 0.5 to 3 at%, calcium (Ca) at 0.01 to 2 at%, and iron (Fe) as the remainder of the composition (at%).
(2) pulverizing the amorphous alloy ribbon to form an amorphous alloy powder;
(3) classifying the formed amorphous alloy powder;
(4) mixing the classified powder with an aqueous sodium silicate solution binder;
(5) pressing the powder mixed with the binder to form a powder core; And
(6) heat-treating the formed powder core at 500 to 550 ° C for 5 to 60 minutes for nanocrystallization of the powder core.
delete The method of claim 3,
Further comprising the step of preheating the amorphous alloy ribbon produced in the step (1) before the step (2) of forming the alloy powder.
delete delete

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