JPH03278501A - Soft magnetic core material and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a flexible magnetic core material having both characteristics of high magnetic flux density and high permeability and small magnetic core loss at the same time by making the title material into a formed product, where a material containing the specific quantity of Si and Al with a remainder consisting substantially of Fe is deposited and solidified and where an oxide insulating layer is formed in a grain boundary and a relative density is not less than a specific value. CONSTITUTION:The title material is made into a formed product, where a material containing 0.2-17wt.% in total of one or two kinds of Si and Al with a remainder consisting substantially of Fe is deposited and solidified and where an oxide insulating layer is formed in a grain boundary and a relative density is not less than 95%. Also, an Fe-based alloy containing at least one kind of Si and Al is melted, and thereafter deposited and solidified in the form of droplets in an atmosphere containing oxygen or further fabricated and subsequently heat-treated, to manufacture the flexible magnetic core material. For example, an Fe-Si alloy containing 8.0wt.% Si is melted and thereafter dispersed by gas-atomizing method using Ar containing oxygen to be deposited on a metal plate, which is then rolled as it is at a high temperature and subjected to a heat treatment at 900 deg.C for 30 minutes in an inert gas.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high-frequency soft magnetic core material used in transformers, inductors, electromagnetic solenoids, motors, etc., and a method for manufacturing the same.

(Prior art) Conventionally, ferrite magnetic cores and thin metal plates such as insulated Fe-Si alloys and Fe-Ni alloys have been used as magnetic core materials for transformers, inductors, electromagnetic solenoids, motors, etc. that operate with alternating current or direct current pulses. Mainly used are laminated magnetic cores and powder magnetic cores made of metal-based magnetic powder that is insulated and then pressure-formed.

However, although the Ferrite+-m core has the advantage of high magnetic permeability and low core loss, it has a low magnetic flux density of 0.5
Although laminated magnetic cores made of thin metal plates have high magnetic flux density and magnetic permeability, magnetic core loss increases due to increased eddy current in the high frequency range, so generally several KHz to several tens of KH2 are obtained. This is the limit of frequencies that can be used.

On the other hand, powder magnetic cores have a relatively high magnetic flux density and low core loss, but have a problem of low magnetic permeability.

The reason why the permeability of the powder magnetic core is lower than that of the ferrite core or the laminated core of thin metal sheets is because the relative density in powder compacting is around 90% as disclosed in JP-A-63-137142. This is because the bulk magnetic permeability decreases due to the influence of interparticle gaps even if magnetic powder with high magnetic permeability is used because of its small size. In addition, even if efforts are made to increase the relative density by reducing the amount of insulating binder or increasing the molding pressure, the
It is extremely difficult to obtain a relative density that greatly exceeds , and the result is that the core loss increases due to an increase in interparticle eddy current due to poor insulation between the particles.

As described above, none of the conventional magnetic core materials has the characteristics of high magnetic flux density, high magnetic permeability, and low core loss.

(Problems to be Solved by the Invention) However, in recent years, as electronic devices have become smaller and more densely packed, demands for smaller size and higher frequency of transformers, inductors, etc. used in these devices have rapidly increased. Therefore, there is a need for a magnetic core material that has the characteristics of high magnetic flux density, high magnetic permeability, and low core loss.

In view of the above circumstances, the present invention aims to provide a soft magnetic core material having the characteristics of high magnetic flux density, high magnetic permeability, and low core loss, and a method for manufacturing the same.

(Means and effects for solving the problems) The soft magnetic core material of the present invention has the following characteristics.

A product formed by depositing and solidifying a material containing one or two types of Si or Al in a total of 0.2 to 17 t%, with the remainder essentially consisting of Fe, with oxide insulation at the grain boundaries. A layer is formed and the relative density is 95% or more.

Moreover, such a soft magnetic core material can be manufactured by the following method.

(1) After melting a Pe-based alloy containing at least one of Si and Al, it is deposited and solidified in the form of droplets in an oxygen-containing atmosphere.

(2) F containing at least one of S i and Al
After the e-based alloy is melted, it is deposited and solidified in the form of droplets in an oxygen-containing atmosphere, then molded and then heat treated.

Hereinafter, the reasons for the limitations of the present invention and its effects will first be described with respect to soft magnetic core materials.

In the present invention, the materials are Fe-based, Si,
One or two types of Al in total O,:l'-17wt
% content is used.

This is to reduce the decrease in magnetic flux density of the material and to increase the electrical resistivity of the material.

That is, the above range is selected because if St and At are less than 0.2 wt %, there will be no effect in terms of increasing the electrical resistivity, and if it exceeds 17-t %, the magnetic flux density will be greatly reduced. Further, the addition of Si and Aj is to form an oxide insulating layer having an electrically insulating effect by using the manufacturing method described later, and if it is less than 0.2 wt %, the effect of forming the oxide insulating layer is small.

Further, the oxide insulating layer at the grain boundary is for reducing eddy current loss in a high frequency range. This makes it possible to effectively prevent intergranular eddy currents without using an insulating binder like in conventional dust cores.

The relative density is limited to 95% or more for the purpose of obtaining a magnetic permeability greater than that of a powder magnetic core.

That is, as described in the section on the prior art, powder magnetic cores have a low relative density of around 90%, which is the main cause of the decrease in magnetic permeability. In the present invention, by setting this to 95% or more, it is possible to significantly improve magnetic permeability and improve magnetic flux density compared to conventional powder magnetic cores.

Next, the manufacturing method will be described.

First, a material having the above composition is melted and dispersed into fine droplets by gas atomization, centrifugation, thermal spraying, or the like, and these are deposited on a substrate. At this time, a bulk with very little porosity can be obtained by depositing droplets in a liquid phase or in a solid-liquid coexistence state. Here, the solid-liquid coexistence state refers to a state in which the droplets are in a semi-solidified state, leaving a liquid phase and not completely turning into a solid phase. In addition, by making the dispersed particles as fine as possible and dispersing and depositing them in an oxygen-containing atmosphere, we can ensure that the droplet surface is covered with oxides mainly composed of St or Al during droplet dispensation or deposition. Make it. This oxide coating is for forming an insulating layer at the grain boundaries, thereby reducing eddy current loss in the high frequency range.

On the other hand, in the production of conventional powder magnetic cores, magnetic powder is compression molded in a solid state, so the amount of deformation of the magnetic powder is small, and a binder is added to ensure the strength of the compact and to provide intergranular insulation. Therefore, it was difficult to increase the relative density to 95% or more.

By the above method, a magnetic material with the characteristics of high magnetic flux density, high magnetic permeability, and low core loss can be obtained.
In the as-deposited state, the dimensions and surface condition are not uniform and it is often not suitable for use as a magnetic core.

In that case, it is effective to process the material into the desired shape and dimensions by rolling or forging after deposition or after reheating, and then perform heat treatment. As a result, magnetic permeability and magnetic flux density can be further improved by the compression effect of the porosity slightly remaining in the bulk, and oxygen in the grain boundary portion is preferentially combined with SL or Al in the grains by heat treatment, It is possible to strengthen the oxide layer at grain boundaries. The temperature range for the heat treatment is 60°C in order to promote the reaction between Si, Al and grain boundary oxygen.
It is desirable to carry out in the range of 0-1200 degreeC.

(Example) The contents of the present invention will be explained in detail below using examples.

[Example 1] Fe- containing 0.5 evt% and 8.0 evt% of Si
After melting, the Si alloy was dispersed by gas atomization and deposited on a metal plate. At this time, the gas contains 10 vol of oxygen.
Ar containing 1% I was used. The average particle diameter was 34 m, and the relative density of the formed particles was about 97%. From this material,
A ring with an outer diameter of 25 cm, an inner diameter of 18 cm, and a height of 5 cm was manufactured by machining, and the magnetic properties were measured.The results are A in Table 1.
and B. In addition, as a comparative material, 0.5 wt% of St
The Fe-Si alloy containing Fe-Si alloy was dispersed by gas atomization, cooled and collected without depositing particles, mixed with 2st% epoxy resin, and then press-formed at a molding pressure of 8 t/d. As shown in C in Table 1, the soft magnetic core according to the present invention showed significant improvement in both magnetic permeability and magnetic flux density compared to the powder magnetic core of the comparative material.

Incidentally, an LCR meter was used to measure the magnetic permeability, a DC B-H measuring device was used to measure the magnetic flux density, and a U function needle was used to measure the magnetic core loss, and the same method was used hereinafter.

[Example 2] Fe-S containing 0.5 wt% and 8.0 wt% of Si
After depositing the i alloy under the same conditions as in Example 1, approximately 15
The material was rolled to a thickness of 7 mm at a high temperature, and heat treated at 900° C. for 30 minutes in an inert gas. From the obtained Fe-Si plywood, the outer diameter was 25cm by electrical discharge machining.
A ring with an inner diameter of 18 m and a height of 7 cm was prepared, and its magnetic properties were measured. The results are D and E in Table 1. As a result, the soft magnetic core according to the present invention had significantly improved magnetic permeability and magnetic flux density compared to the powder magnetic core of Comparative Material C, and also showed further improved properties than the as-deposited materials A and B. At this time, the relative density of the material had improved to about 98-99%.

In addition, in order to confirm the presence of oxide insulating layers in the grain boundary areas, the atomic distribution near the grain boundaries of material E was investigated using Auger electron spectroscopy. The results are shown in Figure 1.As can be seen from this figure, there are Oxygen and Si at a thickness of 50 to 150 μm from the grain boundary surface
A peak is observed, and the ratio of the atomic concentrations is approximately 2:1. This indicates that a very thin electrically insulating layer mainly composed of SiO□ is formed on the grain boundary surface.

[Example 3] Fe- containing Si: 9.5 wt% and 4224.5 wt%
After melting, the 5i-A1 alloy was dispersed by gas atomization and deposited on a metal plate. At this time, the atmosphere contained 5 oxygen
ν0! % of Ar was used. In addition, the average particle diameter is 53
This deposit was reheated and forged to a thickness of about 10 mm to 5 mm, and heat treated at 850° C. for 60 minutes in an inert gas. The obtained Fe-5i-A7 alloy plate was processed by electric discharge machining to have an outer diameter of 25 mm, an inner diameter of 18 mm, and a height of 5 mm.
F in Table 1 is the result of manufacturing a ring with a value of - and measuring its magnetic properties. The relative density of this material was 98%. In addition, as a comparative material, the alloy was dispersed by gas atomization method,
After cooling and collecting without depositing saccharides and mixing with an inorganic binder mainly composed of water glass, the same was press-molded using a molding press ZT/D, and then heat-treated at 1750°C for 30 minutes in an inert gas. The measurement results for 1° of size are shown in G in Table 1. As a result, the soft magnetic core according to the present invention has magnetic permeability,
A significant improvement in magnetic flux density was seen compared to the comparison powder core.

[Example 4] A Pe-Al alloy containing 3.0 wt% of Al was melted and then dispersed by a gas totomization method and deposited on a metal plate.

At this time, Ar gas containing 2 voj 2% of oxygen was used. Also, the average particle diameter is 38n and the relative density of the formed particles is about 9
It was 6%. From this material, the outer diameter is 25 mm by machining.
(2) A ring with an inner diameter of 18 mm and a height of 5 mm was prepared, and the magnetic properties were measured. The results are H in Table 1. In addition, as a comparison material, the alloy was dispersed by gas atomization, cooled and collected without depositing particles, mixed with 2 wt% epoxy resin, and then press-formed at a molding pressure of 8 t/d. Measurement results of a ring of the same size. The results are shown in (■) in Table 1. As a result, the soft magnetic core according to the present invention showed a significant improvement in both magnetic permeability and magnetic flux density compared to the comparative powder magnetic core.

Table 1 Magnetic properties of Examples [Measurement conditions] 1. : f=100K) lx, 8#: Ha-8000A
Layer iron loss: Bm-100mr, f-1 (IOKI (
z (Effect of the invention) According to the manufacturing method of the present invention, a soft magnetic core for high frequency is produced in the birch described above, which has a higher relative density than a conventional powder magnetic core and has an oxide insulating layer formed at the grain boundaries. The material can be easily manufactured.

In addition, this magnetic core material has the characteristics of high magnetic flux density, high magnetic permeability, and low magnetic core loss, so by using this material, it can be made smaller than conventional powder magnetic cores or ferrite magnetic cores. It has become possible to manufacture transformers and inductors, part 1. Figure 1 shows the results of measuring changes in the atomic concentration of major elements from the grain boundary surface to the depth within the grain using Auger electron spectroscopy for the material. .

Claims (3)

[Claims] (1) 0.2 to 1 total of one or two types of Si and Al
A material formed by depositing and solidifying a material containing 7 wt% with the remainder substantially consisting of Fe, characterized by having an oxide insulating layer formed at the grain boundaries and having a relative density of 95% or more. Soft magnetic core material. (2) The method for producing a soft magnetic core material according to claim 1, wherein the Fe-based alloy containing at least one of Si and Al is melted and then deposited and solidified in the form of droplets in an oxygen-containing atmosphere. (3) A Fe-based alloy containing at least one of Si and Al is melted, deposited and solidified in the form of droplets in an oxygen-containing atmosphere, and then formed and then heat treated. The method for manufacturing a soft magnetic core material according to claim 1.