WO2013108643A1

WO2013108643A1 - Compressed soft magnetic powder body

Info

Publication number: WO2013108643A1
Application number: PCT/JP2013/050033
Authority: WO
Inventors: 和也西; 青野　泰久; 憲一相馬; 今川　尊雄; 北条　啓文; 友綱上條; 大脇　武史; 三谷　宏幸
Original assignee: 株式会社日立産機システム; 株式会社神戸製鋼所
Priority date: 2012-01-17
Filing date: 2013-01-07
Publication date: 2013-07-25
Also published as: JP2013149659A; JP5916392B2

Abstract

Provided is a compressed soft magnetic powder body which does not suffer from an increase in iron loss and which exhibits excellent magnetic characteristics. A compressed soft magnetic powder body produced by applying insulating coatings to the surfaces of metal powder particles which comprise iron powder particles as the main component and then compression-molding the resulting metal powder particles, wherein an oxidation -affected layer that contains iron oxides (11, 12, 13) and a layer-shaped Si oxide (14) is present in each iron-particle interface (10) which is the boundary between iron powder particles, said oxidation-affected layer being formed by heat treatment conducted in an oxidizing atmosphere after the compression molding.

Description

Powdered soft magnetic material

The present invention relates to a powder soft magnetic material produced by compression molding soft magnetic powder.

BACKGROUND ART A powder soft magnetic material produced by compression molding soft magnetic powder represented by iron powder or the like at a high pressure is used for a magnetic core of a motor, a reactor for a power supply circuit, or the like. The advantage of dust cores is that the magnetic properties are isotropic and the fabrication of three-dimensional shaped cores is easy. For this reason, when applied to a motor such as a motor core, the dust core is expected to contribute to downsizing and weight reduction of the motor as compared with a laminated core manufactured by laminating silicon steel plates. In particular, a powder soft magnetic material using pure iron as soft magnetic powder is inexpensive and has high ductility of iron powder and high density of magnetic material, and has an advantage of increasing magnetic flux density. Development towards the target has been activated.

In addition to the high magnetic flux density, it is important that the energy loss due to heat generation under the fluctuation of an alternating magnetic field called iron loss is small as the characteristics required for the powder magnetic soft magnetic material. Iron loss is mainly represented by the sum of eddy current loss and hysteresis loss. The cause of the eddy current loss is the heat generated by the eddy current flowing between the particles of iron powder constituting the powder soft magnetic material. In order to reduce the eddy current loss, it is necessary to coat the insulating layer on the iron powder surface.

On the other hand, the cause of the hysteresis loss is heat generation caused by the movement of the domain wall inside the iron powder. Hysteresis loss is lattice distortion inside iron powder, that is, vacancies that are structural defects that generate distortion, interstitial atoms, dislocations, lattice defects such as dislocations and grain boundaries, and impurities atoms other than Fe and precipitates composed of them. It is strongly influenced by To reduce hysteresis loss, it is necessary to perform heat treatment on the soft magnetic material after compression molding in order to reduce distortion inside iron powder introduced by molding.

Heat treatment of a molded body for the purpose of strain reduction (hereinafter, referred to as “strain reduction heat treatment”) is generally performed in an inert gas atmosphere such as nitrogen gas in many cases. During heat treatment of the compact in the atmosphere or in an oxidizing atmosphere such as water vapor, the insulating film on the powder surface constituting the powder soft magnetic material is partially destroyed to increase the eddy current loss, or the inside of the iron powder The iron loss increases due to the diffusion of oxygen to the metal and the increase in hysteresis loss. By heat-treating the compact in an inert gas, it is possible to reduce the increase in iron loss due to oxidation.

On the other hand, the strain reduction heat treatment in the air which does not require atmosphere control can simplify the heat treatment equipment and shorten the treatment time, and is advantageous from the viewpoint of reducing the process cost in manufacturing. However, when the compacted soft magnetic material is subjected to heat treatment in a high temperature atmosphere at 500 ° C. or higher, there is a problem that the iron loss is increased due to the above-mentioned oxidation.

As a report which performed atmospheric heat processing for the purpose of distortion reduction to a powder compact soft magnetic material, there are examples which are indicated in patent documents 1 and 2.

Patent Documents 1 and 2 disclose a technology in which iron powder coated with a phosphoric acid inorganic insulating layer on its surface is mixed with an organic lubricant, compacted, and heat-treated in an oxidizing atmosphere. Patent Literatures 1 and 2 describe heat treatment in a steam atmosphere at 300 to 600 ° C. for the purpose of strengthening, and prior to this heat treatment, Patent Literature 1 is performed at 250 to 550 ° C. in the air. In Patent Document 2, heat treatment in an inert gas at 500 ° C. or lower or in the air is carried out for the purpose of removing the lubricant of the compact. The phosphoric acid inorganic insulating layer used here has high adhesion and is excellent in the deformation followability of the powder surface at the time of molding, but has a disadvantage that the oxidation resistance in a high temperature oxidizing atmosphere is low. In these inventions, there is a concern that the iron powder surface is easily oxidized after the heat treatment in an oxidizing atmosphere such as air or water vapor, the insulating layer is destroyed, and the iron loss increases.

Japanese Patent Application Publication No. 2007-535134 Japanese Patent Publication No. 2008-544520

As described above, in the case of subjecting the powder soft magnetic material to heat treatment for reducing strain in an oxidizing atmosphere such as the atmosphere, there are many problems with the techniques reported so far. As shown in Patent Documents 1 and 2, when the phosphoric acid inorganic insulating layer is coated, since the insulating layer has low oxidation resistance, it is easily broken during heat treatment and iron loss increases. A highly heat-resistant substance such as SiO ₂ or Al ₂ O ₃ can also be used for the insulating film. However, since these insulating layers are very brittle and have a low ability to follow deformation of iron powder, when applied to highly ductile powders such as pure iron powder, the insulating layer is easily destroyed and iron loss increases. Have a challenge to

An object of the present invention is to provide a powder soft magnetic material having excellent magnetic properties without an increase in iron loss.

The powder soft magnetic material according to the present invention has the following features. A powder soft magnetic material produced by subjecting the surface of a metal powder containing iron powder as a main component to an insulation coating treatment and compacting this metal powder, and in the oxidizing atmosphere after the compacting. As a result of the heat treatment in step (b), an oxidation-influenced layer, which is a layer containing an iron oxide and a layered Si oxide, is formed at the boundary between the iron powders (iron powder interface).

According to the present invention, it is possible to provide a powder soft magnetic material having excellent magnetic properties without an increase in iron loss.

It is a cross-sectional schematic diagram of the powder-powder soft-magnetic body by this embodiment. It is a schematic diagram of the iron powder interface of an oxidation influence layer. It is a schematic diagram which shows the microstructure of the iron powder interface of an unoxidized area | region. It is a TEM image in the iron powder interface of the oxidation influence layer of Example material 1. FIG. It is a TEM image in the iron powder interface of the unoxidized area | region of Example material 1. FIG.

The inventors conducted technical studies based on the problems described above, and even after heat treatment in an oxidizing atmosphere such as the air, iron loss of the powder soft magnetic material does not increase, and it has excellent magnetic properties and low process cost. In addition, we have found a technology for obtaining a novel powder soft magnetic material.

The powder soft magnetic material according to the present invention uses the composite powder produced as follows as a raw material. First, the surface of a metal powder containing iron powder as a main component is covered with an Fe-P-based composite oxide as an inorganic insulating layer by a phosphorylation treatment. Further, an organic layer containing Si is applied in the form of a solution to the upper layer portion, and dried. A lubricant is mixed with the metal powder to prepare a composite powder as a raw material of the powder soft magnetic material. The composite powder is compacted into a soft magnetic material, and the subsequent strain reduction heat treatment is carried out in an oxidizing atmosphere under appropriate temperature and time conditions. According to the present invention, it is possible to prevent an increase in iron loss of the powder soft magnetic material by suppressing the growth of the oxide film generated on the surface of the iron powder and the influence of oxidation to the inside of the iron powder.

In the present invention, the particle size of iron powder constituting the powder soft magnetic material is further controlled, and the proportion of relatively fine iron powder having a particle size of less than 100 μm is made less than 30% by weight. By controlling the particle size of iron powder, the volume ratio occupied by the boundary between iron powder (hereinafter referred to as "iron powder interface") inside the magnetic body is reduced to prevent the progress of oxidation inside the magnetic body. Further, by increasing the density of the powder soft magnetic material, the iron powder interface is narrowed to prevent the progress of oxidation inside the magnetic material. By having the above features, according to the present invention, it is possible to obtain a dusted soft magnetic material having both excellent magnetic properties and low cost.

Hereinafter, a powder soft magnetic material according to an embodiment of the present invention will be described. Although the best mode will be described below, the powder soft magnetic material according to the present invention is not limited to this mode.

1) Best Mode of Insulating Coating Layer The powder soft magnetic material according to the present embodiment comprises an inorganic insulating layer containing phosphoric acid, an organic layer containing Si, and an iron powder (composite iron powder) compounded with a lubricant as raw materials. Do. The composite iron powder is compacted into a soft magnetic material, and the subsequent strain reduction heat treatment is carried out in an oxidizing atmosphere under appropriate temperature and time conditions to obtain the surface area of the powder soft magnetic material (surface And an oxidation affected layer) in the region including the vicinity of the surface.

The oxidation-influenced layer in the present embodiment is a region in which an oxide of iron and an oxide of Si are formed at the interface between iron powders (the boundary between iron powders) constituting the powder soft magnetic material. And formed on the surface area of the powder soft magnetic material. Iron oxide and Si oxide in the oxidation affected layer are formed as the iron powder, the insulation coating, the forming aid, and the lubricant are denatured by heating and oxidation reaction.

FIG. 1 is a schematic cross-sectional view of the powder soft magnetic material according to the present embodiment, showing a cross-sectional texture. The powder compact soft magnetic body 1 is constituted by the bonding of a large number of iron powders 2, and in FIG. 1 has a ring shape and shows a cross section perpendicular to the circumferential direction. The powder soft magnetic body 1 is composed of a surface area including the surface and the vicinity of the surface, and an inner area which is an inner portion of the powder soft magnetic body 1, the surface area is an oxidation affected layer 3, and the inner area is oxidized. The unoxidized region 4 is not formed. The powder soft magnetic body 1 of the present embodiment is characterized in that the influence of oxidation is limited only to the oxidation affected layer 3 formed in the surface area, and the internal area is made an unoxidized area 4 which is in an unoxidized state. is there.

In this embodiment, the surface of the iron powder is coated with an inorganic material having a chemical composition close to that of the complex oxide containing Fe and P, or an inorganic layer as the insulating layer. The coating treatment of the insulating layer is performed by phosphate chemical conversion treatment. At the stage of the phosphate chemical conversion treatment, the surface of the iron powder of the substrate is dissolved by oxidation and reacted with phosphoric acid, whereby a composite oxide layer mainly composed of Fe-P is formed on the surface of the iron powder.

The Fe-P complex oxide layer, while having very high adhesion to the pure iron of the base material, is more resistant to deformation of iron powder compared with other oxide systems such as SiO ₂ and Al ₂ O ₃ . The ability to follow is very good.
For this reason, the Fe—P-based composite oxide layer does not receive any damage that would cause the insulation deterioration such as peeling or breakage even during surface deformation during compacting. The Fe—P-based composite oxide layer has a glass (amorphous) structure up to about 550 ° C., and crystallizes by heating at a high temperature exceeding 550 ° C. However, even after crystallization, the insulating property of the Fe—P-based composite oxide layer is maintained as long as the insulating layer is stably present on the surface of the iron powder and significant damage such as peeling does not occur.

In the present embodiment, the upper layer portion of the Fe—P-based composite oxide layer is covered with an organic layer containing Si in an overlapping manner. The organic layer containing Si can be coated with an organic substance such as a silicone resin in the form of a solution, uniformly coated on the iron powder surface and then dried. By covering the iron powder surface with the organic layer containing Si, when heat treating the powder soft magnetic material in a reducing atmosphere to reduce strain, an oxidation suppression layer mainly composed of Si is formed on the iron powder interface of the oxidation affected layer. Be done. The oxidation suppressing layer has an effect of reducing the iron loss of the powder soft magnetic material.

A lubricant is preferably added to the iron powder coated with the two insulating layers of the Fe—P-based composite oxide layer and the organic layer containing Si of the present embodiment for the purpose of imparting formability. The material of the lubricant is not particularly limited, but conventionally known ones may be used. Specific examples thereof include metal salts such as zinc stearate and lithium stearate, and other waxes. When the amount of lubricant added is excessively increased, the density of the powder soft magnetic material is reduced, which causes the inhibition of the magnetic characteristics. In addition, when the addition amount is small, extraction after compression molding becomes difficult, and the formability is reduced. The lubricant is preferably added in the range of 0.05 to 0.8% by mass.

2) Best mode of green compact structure considering oxidation resistance In the present embodiment, the above-described composite iron powder is compacted into a soft magnetic material, and a heat treatment for reducing strain is performed in an oxidizing atmosphere. At this time, the heat treatment is carried out under appropriate temperature and time conditions to form an oxidation-influenced layer on the surface area of the powder soft magnetic material.

In the initial process of heat treatment, in the iron powder in the surface area of the powder soft magnetic material, oxygen (O) passes through and diffuses through the Fe-P-based composite oxide layer, and easily oxidizes with the pure Fe in the base, An oxide mainly composed of Fe such as ₃ O ₄ is formed. As pure Fe reacts with O to form an oxide, an increase in volume occurs, and the Fe—P-based composite oxide layer and the organic layer containing Si undergo excessive deformation. At the same time, the adhesion between the two insulating layers and the base material is sharply reduced, and the insulating layer is peeled off and decomposed, whereby the formation of the oxide mainly composed of Fe further progresses. In this process, most of the lubricant initially charged at the interface between the iron powders is vaporized and disappears by oxidation. The oxide mainly composed of Fe fills the gap of the interface where the lubricant disappeared and grows while taking in the remaining part of the peeled and decomposed two insulating layers.

As a result of the above, as the main substance formed at the iron powder interface of the oxidation affected layer,
1) Oxide mainly composed of Fe (eg Fe ₃ O ₄ etc.)
2) Complex oxides in which Fe is bonded to Si (Fe-Si complex oxides such as Fe ₂ SiO ₄ etc.)
3) Complex oxides in which Fe is combined with elements constituting the insulating layer such as P and Si (Fe-P-Si complex oxides)
4) An oxide mainly containing Si (eg SiO ₂ ) containing almost no Fe
Is generated.

The “Fe-based oxide” in 1) is mainly produced by the oxidation of iron powder. The “Fe—Si complex oxide” in 2) is formed by complex oxidation of Si in the organic layer with the Fe oxide. The “Fe—P—Si complex oxide” in 3) is produced by peeling off the insulating layer on the surface of the iron powder and reacting / aggregating with Fe. The “Fe-based oxide” containing almost no Fe in 4) is generated by oxidizing, aggregating, and rearranging Si contained in the organic layer containing Si by a thermal reaction.

FIG. 2 is a schematic view of the iron powder interface of the oxidation affected layer. As shown in FIG. 2, in the oxidation-influenced layer, the iron powder interface 10 is formed of Fe-based oxide 11 (Fe ₃ O ₄ ) and Fe—Si composite oxide 12, and massive Fe—P—Si composite oxidation. things 13, and an oxide of layered that the Si mainly contains almost no Fe 14 is composed of 3 tissue named (SiO _2).

The oxidation reaction of the powder soft magnetic material at the time of heat treatment proceeds by the diffusion of oxygen atoms entering from the surface of the soft magnetic material into the interior of the powder soft magnetic material through the iron powder interface. That is, the iron powder interface is a diffusion path of oxygen at the time of heat treatment. In the present embodiment, the role of the oxide 14 (for example, SiO ₂ ) mainly containing Si, which does not substantially contain Fe in 4) present at the iron powder interface 10 of the oxidation affected layer, is important.

The Si-based oxide 14 is reacted and generated simultaneously with the Fe-based oxides 11 and 2) of the 1) Fe-Si composite oxide 12. As a result, the structure of the oxide 14 mainly composed of Si becomes a layer having a thickness of several tens of nm, and is arranged so as to divide the iron powder interface 10 longitudinally and laterally. The Fe-based oxide 11 (Fe ₃ O ₄ etc.) of 1) and the Fe-Si complex oxide 12 of 2) have a thickness of several tens of nm and a gap of the Si-based oxide 14 of mainly Si. It is formed to fill the

The layered oxide 14 mainly composed of Si in 4) is very excellent in oxidation resistance as compared with the oxides 1) to 3) containing Fe. It is presumed that this layered oxide mainly composed of Si functions as an oxidation suppressing layer that blocks the diffusion of oxygen during heat treatment by dividing and arranging the iron powder interface 10. It is a major feature of the powder soft magnetic material according to the present embodiment that an oxide mainly composed of Si not containing Fe is present in the oxidation affected layer as an oxidation suppression layer.

The microstructure of the lower part of these oxidation-influenced layers, that is, the internal region of the powder soft magnetic material, has a different appearance from the oxidation-influenced layers. A dense composite oxide layer containing Fe, P and Si is formed as an insulating layer on the surface of the iron powder in the inner region of the powder soft magnetic material. This composite oxide layer has a two-layer structure consisting of a lower layer in contact with the iron powder surface and an upper layer on the upper side thereof, and the compounding ratio of P to Si is different in each layer. In the lower layer, P is relatively abundant together with Fe, but the content of Si is small.
On the other hand, the upper layer is characterized in that the content of P is small and Si is contained more than in the lower layer. Such a two-layered composite oxide layer consisting of a "Fe-P-based lower layer" rich in Fe and P and a "Si-rich upper layer" rich in Si is initially present on the surface of iron powder. A structure in which the Fe—P-based composite oxide layer and the organic layer containing Si are stacked is changed by heating and formed.

In the inner region of the powder soft magnetic material, the insulating layer having a two-layer structure on the surface of the iron powder preferably has a total thickness of 10 to 200 nm. If the total thickness of the insulating layers is less than 10 nm, the insulation property is unfavorably reduced. If the total thickness of the two layers exceeds 200 nm, the distance between the iron powders increases, which is not preferable because it leads to a decrease in magnetic flux density.

The outer interface (the interface which is not in contact with the iron powder) of the two-layered insulating layer is filled with an organic substance mainly containing C and O and containing some Si. The organic substance filling the interface is presumed to be a structure in which chemical components such as metal soap or wax of the organic layer containing Si and the lubricant before heat treatment are changed by heating.

As described above, the interface microstructure in the inner region of the powder soft magnetic material is the structure found in the oxidation affected layer (ie, an oxide mainly composed of Fe, an Fe-Si composite oxide, an Fe-P-Si composite) It shows a different aspect from the structure of oxide) and a structure containing an oxide mainly containing Si and containing almost no Fe. Such an inner region of the powder soft magnetic material is referred to as an "unoxidized region" because oxidation hardly occurs. In the unoxidized region, almost no reaction with oxygen which penetrates and diffuses from the outside through the iron powder interface occurs. This unoxidized region is shown as unoxidized region 4 in FIG.

FIG. 3 is a schematic view showing the microstructure of the iron powder interface in the unoxidized region. As shown in FIG. 3, in the unoxidized region, two layers of a lower layer 21 mainly composed of Fe-P and a Si-rich upper layer 22 are formed on the surface of the iron powder. The lower layer 21 mainly composed of Fe-P is an inorganic insulating covering layer, and the Si-rich upper layer 22 is an oxide insulating layer, so these two layers are dense insulating layers. Furthermore, an organic layer 23 mainly composed of C and O and containing Si is present between the insulating layers, and fills the iron powder interface 10. As a result, the insulation between the iron powder is maintained in the unoxidized region, and the eddy current loss is reduced.

On the other hand, in the oxidation-influenced layer on the surface area of the powder soft magnetic material, the insulating layer on the surface of the iron powder is broken, and the eddy current loss increases. If the effect of oxidation during atmospheric heat treatment affects the entire compacted soft magnetic material, the unoxidized tissue disappears. As a result, the iron loss of the powder soft magnetic material increases, leading to the deterioration of the magnetic properties. Therefore, it is not preferable that the whole of the powder soft magnetic material is affected by oxidation.

Therefore, in order to reduce the iron loss of the powder soft magnetic material after heat treatment, the formation of the oxidation affected layer is limited to the surface region of the powder soft magnetic material only, and the internal region of the powder soft magnetic material is not oxidized It is important to keep the condition. In the present embodiment, as described above, diffusion of oxygen to the inner region of the powder soft magnetic material can be achieved by forming an oxidation suppression layer of an oxide mainly composed of Si in the iron powder interface of the oxidation affected layer. It is possible to suppress the internal region into an unoxidized state (to be an unoxidized region).

3) Best form of composition and particle size of iron powder In the present embodiment, the iron powder as the raw material of the powder soft magnetic material has a content of elements other than Fe such as Mn, Cr, Si, P and S. Iron powder as low as possible is preferred. In the powder production process, it is preferable to use water atomization or gas atomization treatment. Since the iron powder after atomization treatment contains many gas impurities such as O, C, N, etc., it is necessary to carry out a heat treatment in a reducing atmosphere containing hydrogen at 800 to 1000 ° C. to purify the iron powder. . It is preferable to reduce the content of O in the iron powder to 500 ppm or less for the purpose of preventing an increase in iron loss. Similarly, it is preferable to reduce the C content to 30 ppm or less and the N content to 10 ppm or less for the purpose of preventing an increase in iron loss.

The size (particle size) of the iron powder constituting the powder soft magnetic material affects the magnetic properties after the strain reduction heat treatment. When the proportion of fine iron powder having a particle size of less than 100 μm is large, the volume proportion of the iron powder interface increases in the inside of the powder soft magnetic material. The iron powder interface serves as a diffusion path of oxygen to the inside of the powder soft magnetic material at the time of strain reduction heat treatment. For this reason, in the case of a powder soft magnetic material having the same density, when the volume ratio of the interface portion is high, the oxidation-affected layer easily grows to the inside, and the core loss increases.

For this reason, as for the particle size of the iron powder, it is preferable that the proportion in the range of 100 to 400 μm is 70% or more by weight, and the proportion of the fine iron powder below 100 μm is less than 30% by weight. If it is such a ratio, the growth to the inside of the oxidation influence layer at the time of distortion reduction heat processing will be suppressed, and an iron loss will fall. The average particle size of the entire iron powder is preferably 120 to 250 μm from the viewpoint of core loss reduction. An excessively large particle size of the iron powder is not preferable because it leads to an increase in eddy current loss. The proportion of coarse iron powder having a particle size of more than 400 μm is preferably less than 30% by weight.

4) Best mode of molding conditions and compact density The composite powder as a raw material of the powder soft magnetic material obtained by the above method is subjected to excessive plastic deformation under high pressure by die molding, It is magnetic. The molding pressure is usually 800 MPa or more, and it is preferable to increase the density so that the ratio of metal Fe to the powder soft magnetic material is 94% or more in volume ratio.

When the density of the powder soft magnetic material is low, the distance between the iron powders constituting the magnetic body, that is, the width of the iron powder interface is increased. When the width of the iron powder interface is wide, during the strain reduction heat treatment, oxygen is contained in the gaps of the oxidation-inhibited layer of the oxidation-affected layer (an oxide distributed in a thin layer containing mostly Fe and containing Si). It diffuses inside the compacted soft magnetic material. As a result, the core loss increases as the proportion of the unoxidized area inside the dusted soft magnetic material decreases. Therefore, making the density of the powder soft magnetic material sufficiently high to narrow the width of the iron powder interface is effective in reducing iron loss.

The density of the powder soft magnetic material is preferably at least 7.45 g / cm ³ or more, preferably 7.50 g / cm ³ or more. The ratio of metal Fe to the powder soft magnetic material is more preferably 94.0% or more, preferably 95.0% or more in volume ratio. When the density of the powder soft magnetic material is less than 7.45 g / cm ³ , the diffusion of oxygen to the inside of the powder soft magnetic material is promoted during heat treatment, and the proportion of the oxidation affected layer increases, and the powder soft magnetic material This is not preferable because it causes an increase in iron loss of the magnetic substance. For the same reason, even when the proportion of the iron powder itself is less than 94.0% by volume, it is not preferable because it causes an increase in iron loss of the powder soft magnetic material after heat treatment. It is difficult in terms of molding process to increase the density of powder soft magnetic material to over 7.75 g / cm ³ , and there is also the possibility of an increase in eddy current loss due to breakage of the insulating layer, so the density is 7.75 g It is preferable to set it as / cm < ³ > or less. The occupancy rate of the iron powder itself (the ratio of the iron powder to the powder soft magnetic material represented by the volume ratio) is preferably 98.5% or less.

5) Optimal Thickness of Oxidation Affected Layer The optimum thickness of the oxidation affected layer in the dusted soft magnetic material will be described below.

First, the “thickness” of the powder soft magnetic material is defined. At any point on the surface of the powder soft magnetic material, a straight line is drawn in the direction perpendicular to the surface toward the inside of the powder soft magnetic material. In this straight line, the length of a line segment from the surface to the other surface on the opposite side of the powder soft magnetic material (the back side of the powder soft magnetic material) is the powder softness at any given location. It is defined as the thickness of the magnetic body.
When explaining using FIG. 1, the thickness of the powder soft magnetic material is D. When the surface of the powder soft magnetic material is a curved surface, a straight line is drawn in the direction perpendicular to the contact surface on the surface to define the thickness. That is, the thickness at any place of the powder soft magnetic material is the length of the powder soft magnetic material at that place in the direction perpendicular to the surface of the place.

Similarly for the oxidation affected layer, the length of the oxidation affected layer in the above-mentioned line segment is referred to as "thickness". However, the thickness of the oxidation-influenced layer is not defined where the above-mentioned line segment passes only the surface area, but is defined as where the above-mentioned line segment passes through the inner area and the two surface areas sandwiching the inner area. Do. The two surface areas are located on opposite sides of the soft magnetic powder body. As described with reference to FIG. 1, the thickness of the oxidation affected layer is d1 and d2, and d3 is not the thickness of the oxidation affected layer.

The thickness (length of the above-mentioned line segment) of the powder soft magnetic material may differ depending on the measurement site.

The thickness of the oxidation-influenced layer may be different from the thickness at an arbitrary position and the thickness at a position on the opposite side of the dusted soft magnetic material (the back side of the dusted soft magnetic material) with respect to this position. If it demonstrates using FIG. 1, d1 and d2 do not need to be equal. That is, the thickness of the oxidation affected layer may not be uniform.

The thickness of the oxidation-influenced layer is preferably in the following ratio with respect to the thickness of the powder soft magnetic material in the case of a simple ring-shaped powder soft magnetic material having a circular or rectangular cross section, etc. . The thickness of the oxidation-influenced layer is the thickness (d1 in FIG. 1) at any location of the powder soft magnetic material and the opposite side of the powder soft magnetic material with respect to this location (the back side of the powder soft magnetic material The total of the thickness (d2 in FIG. 1) and the thickness of the portion at 1) is 1/16 or more and 1⁄2 or less of the thickness (D in FIG. 1) of the powder soft magnetic material It is optimal from the magnetic properties of the soft magnetic material. At this time, this arbitrary place (the place where d1 in FIG. 1 is defined) and the place on the opposite side of the powder soft magnetic material with respect to this place (place where d2 in FIG. 1 is defined) , On the straight line mentioned above.

If the total thickness of the oxidation-affected layer at a point opposite to any part of the powder soft magnetic material is less than 1/16 of the thickness of the powder soft magnetic material, it is estimated that the heat treatment time is short It is not preferable because strain reduction is insufficient to cause an increase in iron loss. In addition, when this total exceeds 1⁄2 of the thickness of the powder soft magnetic material, the ratio of the volume of the unoxidized region in the powder soft magnetic material decreases. In this case, the core loss of the powder soft magnetic material is increased to deteriorate the magnetic properties, which is not preferable.

When the powder soft magnetic material is applied to a rotor core or a stator core of a motor, the cross section may not have a simple ring shape such as a circle or a rectangle, but may have a three-dimensional complex shape having a projection such as a claw. In the powder soft magnetic material of complicated shape, the difference in the shape causes a difference in thickness in the powder soft magnetic material. In this case, it is conceivable that the proportion of the oxidation-influenced layer relatively increases to exceed 1/2 at portions where the thickness of the powder soft magnetic material is small. In the powder soft magnetic material having a complex cross section other than a circular or rectangular cross section, the total thickness of the oxidation affected layer is the thickness of the powder soft magnetic material at a location where the thickness of the powder soft magnetic material is averaged. It is preferable that it is 1/16 or more and 1/2 or less.

In the present embodiment, as a method of evaluating the thickness of the oxidation affected layer of the powder soft magnetic material, it is also possible to evaluate by observing the microstructure of the cross section of the powder soft magnetic material. SEM (scanning electron microscope) equipped with EDS (energy dispersive X-ray spectroscopy) analysis function for cross-sectional structure after cutting any part of the powder soft magnetic material and performing resin embedding and polishing on the cross-sectional part By observing with, it is possible to clearly distinguish the structure of the oxidation affected layer and the unoxidized region. In the oxidation affected layer, an oxide mainly composed of Fe is formed at the iron powder interface, while an oxide mainly composed of Fe does not exist at the iron powder interface in the unoxidized region. Therefore, in the observation of the microstructure of the cross section of the powder soft magnetic material, the width from the surface of the powder soft magnetic material is measured at a plurality of points in the region where the oxide containing Fe is present at the iron powder interface. It becomes possible to evaluate the thickness of the oxidation affected layer directly.

6) Best Mode of Heat Treatment Process The strain reduction heat treatment of the powder soft magnetic material is preferably carried out mainly in an air atmosphere from the viewpoint of reduction of the process cost. As another heat treatment atmosphere, a steam atmosphere or an oxidation atmosphere in which a pure oxygen gas of 20% or less (preferably 0.5 to 20%) by volume ratio is added to an inert gas such as nitrogen, argon or helium, The same effect is obtained.

The maximum holding temperature of the heat treatment is preferably in the range of 500 ° C. or more and less than 650 ° C. When the holding temperature is less than 500 ° C., the strain reduction of the iron powder constituting the powder soft magnetic material becomes insufficient, and the iron loss increases, which is not preferable. When the holding temperature is 650 ° C. or more, it is not preferable because the iron powder is excessively oxidized and the ratio of the unoxidized region inside the green compact is decreased to increase iron loss.

The holding time at the maximum temperature should be at least 5 minutes in the above temperature range. If the holding time is less than 5 minutes, the strain reduction of the iron powder becomes insufficient, and the iron loss of the powder soft magnetic material increases, which is not preferable. If the retention is excessive for a long time, the oxidation of iron powder is promoted and the iron loss is increased. The optimum holding time depends on the heat treatment temperature.

When the heat treatment temperature is maintained at 500 ° C. or more and less than 550 ° C., the maximum heat treatment time is preferably 2 hours. If it exceeds 2 hours, the iron powder is excessively oxidized, and the proportion of the unoxidized region inside the green compact decreases, which is not preferable because iron loss increases. When the heat treatment temperature is maintained at 550 ° C. or more and less than 600 ° C., the heat treatment temperature is preferably 1 hour at maximum. When it exceeds 1 hour, it is not preferable because the iron powder is excessively oxidized and iron loss increases. When the heat treatment temperature is maintained at 600 ° C. or more and less than 650 ° C., the maximum heat treatment time is preferably 30 minutes. If it exceeds 30 minutes, it is not preferable because the iron powder is excessively oxidized to increase iron loss.

After the end of the holding, it is preferable to take out the heat-treated body from the heating furnace to room temperature and air-cool as soon as possible. When it is placed in a heating furnace and cooled, it is not preferable because oxidation of iron powder becomes excessive and iron loss increases.

Hereinafter, the powder soft magnetic material according to the present invention will be described in more detail by way of examples.

The pure iron ingot material was pulverized by water atomizing treatment after being dissolved in air. The atomized iron powder was purified by repeating the hydrogen reduction heat treatment at 950 ° C. for 2 hours twice. The oxygen concentration contained as an impurity after purification was 500 mass ppm or less. The iron powder after purification was sieved to a particle size of 100 to 300 μm by a mesh, and then the Fe—P-based composite oxide layer was coated on the iron powder surface as an insulating layer by a phosphorylation treatment. The thickness of the Fe—P based composite oxide layer was in the range of 20 to 50 nm.

A silicone resin solution was applied to iron powder coated with Fe—P based composite oxide and dried to prepare iron powder (Example material 1). To the iron powder of Example Material 1, 0.4% by mass of a zinc stearate based lubricant was added, and mixed by a V mixer to obtain a soft magnetic composite powder. As a comparative material, an iron powder (comparative material 1) coated with only the Fe-P based composite oxide layer was prepared, and 0.4 mass% of zinc stearate based lubricant was added to the iron powder of comparative material 1 A mixed powder was also prepared.

The above soft magnetic composite powder was pressed at a molding pressure of 1200 MPa to form a ring-shaped powder soft magnetic material having an outer diameter of 50 mm, an inner diameter of 40 mm, and a thickness of 5 mm. The density of the ring-shaped powdery soft magnetic material measured by the Archimedes method was 7.50 to 7.54 g / cm ³ . The compacted soft magnetic material after molding was subjected to strain reduction heat treatment in a box-shaped air heat treatment furnace. The holding temperature of the heat treatment was 550 ° C., the temperature was raised from room temperature to 550 ° C. at a heating rate of 5 ° C./min, and after holding for 30 minutes, it was taken out of the furnace and air cooled. The surface of the soft magnetic powder after heat treatment had a black color overall due to the influence of oxidation.

Conduct the winding of 200 turns on the primary side and 60 turns on the secondary side using 0.5 mm copper wire to the powder soft magnetic material after heat treatment, and iron loss at a frequency of 400 Hz (W / kg) I asked for. As a result of measurement of iron loss, Example Wound 1 was 37 W / kg, and Comparative Wound 1 was 53 W / kg. From the above results, it was found that Example Material 1 had a core loss of 16 W / kg lower than that of Comparative Material 1 and exhibited excellent magnetic properties.

For the purpose of examining the state of the microstructure of the example material 1 in detail, the microstructure of the cross section of the powder soft magnetic material was observed using a transmission electron microscope (TEM). The ring-shaped test piece of the example material 1 after magnetic property evaluation was used for TEM observation. Thin film test pieces were collected from two points of the oxidation affected layer 3 in the surface area of the powder soft magnetic body 1 and the unoxidized area 4 in the inner area shown in FIG. 1 using the FIB (focused ion beam) method. For observation, a TEM apparatus (FE-TEM) having an electron emission type of electron emission type and capable of reducing the diameter of a probe of an electron beam to 1 nm level was used.

FIG. 4 is a TEM image (bright field image) at the iron powder interface of the oxidation affected layer of the example material 1. FIG. 4 shows two different iron powders and an interface 10 between these iron powders. The width of the iron powder interface 10 is about 200 to 500 nm. It can be seen that a white network 31 exists inside the iron powder interface 10, and the gray tissue 32 is filling the gaps. The white network 31 inside the iron powder interface 1 has a width of 5 to 100 nm. As a result of electron diffraction performed with an electron beam probe being several nm, it was found that the white network 31 had an amorphous structure.
Further, it was found from the compositional analysis by EDS that only Si and O were detected from the white network 31 and Fe was not present. From this result, it is presumed that the white network 31 present inside the iron powder interface 10 is an Si oxide having an amorphous structure, probably SiO ₂ .

Similarly, as a result of carrying out the same electron beam diffraction for the gray tissue 32 filling the gaps of the white network 31 inside the iron powder interface 10, a ring-like diffraction pattern was observed. From the analysis of the diffraction pattern, it was found that the gray structure 32 was Fe ₃ O ₄ , an oxide mainly composed of Fe, and Fe ₂ SiO ₄ of a composite oxide containing Fe and Si. Since the probe diameter of the electron beam is several nm, the gray structure 32 filling the gaps of the network structure 31 is Fe ₃ O ₄ and Fe ₂ SiO ₄ composed of nano-sized fine crystal grains. I understand.

At the iron powder interface 10, in addition to this, a massive oxide having a diameter of several tens to several hundreds of nm containing Fe and P was present. It is inferred that this massive oxide is formed as the Fe—P based complex oxide coated on the surface of iron powder is detached and aggregated by oxidation.

FIG. 5: is a TEM image in the iron powder interface of the unoxidized area | region of the example material 1, and shows a part (one iron powder and its interface) of FIG. In FIG. 5, the white part is the iron powder interface 10, and the dark part is the iron powder. The structure of the unoxidized region is different from the structure of the oxidation affected layer shown in FIG. 2 and FIG. As shown in FIG. 5, a surface layer having a thickness of less than 100 nm was present on the surface of the iron powder, and Fe, P, Si and O were detected from this surface layer by EDS analysis. A relatively large amount of P was detected on the iron powder side (lower layer) of this surface layer, and a small amount of Si was detected. On the other hand, on the interface side (upper layer) of this surface layer, P was small and Si was detected more than in the lower layer. In FIG. 5 this distinction between lower and upper layers can not be seen due to the resolution of the picture.

From this result, an oxide-based insulating layer containing Fe, P, Si and O is present on the surface of the iron powder in the unoxidized region, and this insulating layer consists of two layers of different chemical compositions It has been found that it is composed of a layer and a Si-rich upper layer). The two layers are the lower layer 21 mainly composed of Fe-P and the upper layer 22 of Si-rich described with reference to FIG.

Moreover, C and O were detected from the white site | part (iron powder interface 10 of an unoxidized area | region) shown in FIG. As for the metal element, low concentration of Si was detected, but Fe was not detected. From this result, the iron powder interface 10 in the unoxidized region is filled with a substance containing C and O, and this substance is probably formed during the heat treatment of the zinc stearate-based substance that is a lubricant. It is guessed that. The white portion is the organic layer 23 mainly composed of C, O, and Si described with reference to FIG.

The two insulating layers on the surface of the iron powder in the unoxidized region shown in FIG. 5 do not exist at the iron powder interface 10 of the oxidation affected layer of FIG. From the comparison of the structure of each region in FIGS. 4 and 5 by TEM observation, in the surface region of the ring-shaped test piece of the example material 1 subjected to the strain reduction heat treatment in the atmosphere, the iron powder is oxidized and the insulating coating layer is broken. It was found that an oxidation affected layer was formed. At the iron powder interface of the oxidation affected layer, oxides such as Fe ₃ O ₄ , Fe ₂ SiO ₄ and SiO ₂ were formed. On the other hand, it was found that oxidation did not reach the inner region of the ring-shaped test piece, and an insulating layer having a two-layer structure different in chemical composition was present on the surface of the iron powder.

In the same manner as in Example 2, TEM observation of the cross-sectional portion was performed on the ring-shaped test piece of the comparative material 1 after the magnetic property evaluation. As in the second embodiment, the observation position was set to two parts, the surface area and the inner area of the powder soft magnetic material. As a result of observation of the surface area of the comparative material 1, it was found that most of the iron powder interface was filled with an oxide mainly composed of Fe. At the iron powder interface, in addition to this, massive oxides of several tens to several hundreds nm in diameter containing Fe and P were present. It is inferred that this massive oxide is formed as the Fe—P based complex oxide coated on the surface of iron powder is detached and aggregated by oxidation. At the iron powder interface in the surface region of Comparative Example 1, the network-like oxidized layer containing Si, which was seen in Example material 1, did not exist.

As a result of observation of the inner region of the comparative material 2, the structure of the iron powder interface in the inner region is almost the same structure as that of the surface region, and the iron powder interface is filled with Fe-based oxide, and Fe, P It has been found that massive oxides of several tens to several hundreds of nm in diameter are present. In Example 2, the inner region of Example material 1 was in the unoxidized state, and the insulating layer having a two-layer structure was present on the surface of the iron powder. On the other hand, in the inner region of the comparative material 2, it was found that the iron powder was oxidized similarly to the surface region, and the insulating layer on the surface of the iron powder was detached and aggregated.

From the TEM observation results of Examples 2 and 3, in Example material 1, the SiO ₂ layer distributed in the form of a mesh at the iron powder interface of the oxidation affected layer functions as an oxidation suppression layer, It was found that the iron loss is reduced by suppressing the progress of the oxidation to the inside and stably holding the insulating layer on the surface of the iron powder. On the other hand, it is considered that in Comparative Material 1, the network-like SiO ₂ layer was not present at the iron powder interface, and the oxidation preventing effect as in Example Material 1 did not work. As a result, in the comparative material 1, the internal area of the powder soft magnetic material is affected by the oxidation, and it is presumed that the core loss is increased by the falling off and aggregation of the insulating layer on the surface of the iron powder.

The iron powder subjected to the water atomizing treatment and the hydrogen reduction heat treatment under the same conditions as in Example 1 was sieved using meshes having different openings to prepare a plurality of iron powder samples having different particle sizes.
For each iron powder sample after sieving, the insulation coating of Fe-P based complex oxide layer and Si resin is carried out in the same manner as in Example 1 and 0.4% of zinc stearate based lubricant is added. By mixing, a plurality of composite powders with different particle sizes were produced. Thereafter, press molding, heat treatment in air, winding, and magnetic property evaluation were performed under the same conditions as in Example 1 to compare the properties of the respective powder soft magnetic materials.

Table 1 shows the average particle diameter and particle size of the powder soft magnetic material obtained by forming and heat treating five types of iron powder (example materials 1, 2, 3 and comparative materials 2 and 3) having different particle sizes. The ratio of iron powder having a diameter of less than 100 μm, the evaluation result of iron loss (iron loss value), and the thickness of the oxidation affected layer are shown.

In Table 1, the average particle diameter of the iron powder decreases in the order of the example materials 1, 2, 3 and the comparative materials 2, 3. On the other hand, when the proportion (weight%) containing fine iron powder having a particle size of less than 100 μm is compared, the proportion of iron powder having a particle size of less than 100 μm tends to increase as the average particle size decreases. In the example materials 1, 2 and 3, the iron powder having a particle size of less than 100 μm is 20% or less. On the other hand, it can be seen that iron powder having a particle size of less than 100 μm is about half in Comparative Material 2 and iron powder having a particle size of less than 100 μm occupies 80% or more in Comparative Material 3.

In Table 1, as the core loss value, the result of heat treatment at 550 ° C. in the air and the result of heat treatment in vacuum at the same temperature and for the same time are also described. The core loss value after heat treatment in the atmosphere is 41 W / kg for Example Material 3 and 37 W / kg of Example Material 1 or so. On the other hand, Comparative Material 2 had 59 W / kg, Comparative Material 3 had 83 W / kg, and these iron loss values increased by about 20 to 40 W / kg as compared with Example Material 3. .

On the other hand, the core loss value after heat treatment in vacuum is almost the same as that of heat treatment in the atmosphere (the reduction of 1 to 2 W / kg by vacuum heat treatment). On the other hand, in the comparative materials 2 and 3, it was found that the core loss after the heat treatment in vacuum was significantly reduced (a reduction of 12 to 15 W / kg) than the heat treatment in air. When the insulation is maintained, the iron loss value of the powder soft magnetic material tends to increase reflecting the increase in the coercive force as the iron powder particle size becomes finer. The iron loss value after heat treatment in vacuum in Table 1 is presumed to reflect the tendency of iron powder particle size. Further, it can be seen from Table 1 that, in the case of heat treatment in the atmosphere, the increase in iron loss accompanying the miniaturization of iron powder tends to be further promoted.

The powder soft magnetic material after five types of heat treatments shown in Table 1 was cut, resin embedding and polishing were performed on the cross section, and the thickness of the oxidation affected layer was measured by SEM observation and EDS analysis. In the example materials 1, 2 and 3, the thickness of the oxidation affected layer was as thin as less than 1 mm. On the other hand, in Comparative Material 2, the thickness of the oxidation affected layer increased to 1.6 mm. In Comparative Material 3, it was found that the influence of oxidation was applied to almost the entire cross section. From the above results, as the iron powder constituting the powder soft magnetic material becomes finer, the effect of oxidation at the time of heat treatment in the atmosphere proceeds to the inside of the powder soft magnetic material, and the iron loss increases Was shown to promote.

After preparing five sets of the same iron powder as Example material 1, changing the pressure to 1400MPa, 1300MPa, 1000MPa, 700MPa and 600MPa respectively, heat treatment in the atmosphere at 550 ° C, five types of powder soft Magnetic materials were produced (Example materials 4 to 6, comparative materials 4 and 5). Then, the iron loss of the example materials 4 to 6 and the comparative materials 4 and 5 was evaluated.

Table 2 shows the evaluation results of molding pressure, density and iron loss (iron loss value) for six types of powder soft magnetic materials (example materials 1, 4 to 6 and comparative materials 4 and 5) having different molding pressures. And the thickness of the oxidation affected layer.

The density of the powder soft magnetic material is 7.62 g / cm ³ (example material 4), 7.59 g / cm ³ (example material 5), 7.54 g / cm ³ (example examples) as the molding pressure decreases. Material 1) decreases to 7.47 g / cm ³ (example material 6), 7.39 g / cm ³ (comparative material 4), and 7.33 g / cm ³ (comparative material 5). The core loss value is 35 W / kg (example materials 4 and 5), 37 W / kg (example material 1), 41 W / kg (example material 6), 46 W / kg (comparative material 4) as the molding pressure decreases. ), 51 W / kg (comparative material 5) was found to increase.

As in Example 4, the cross section of the powder soft magnetic material was observed by SEM observation and EDS analysis to determine the thickness of the oxidation affected layer. As a result, it was found that the thickness of the oxidation affected layer increased as the density of the powder soft magnetic material decreased. Since the comparative materials 4 and 5 have lower density than the example materials 1 and 4 to 6, the distance between the iron powder interfaces is wide, and as a result, the oxidation through the iron powder interface at the time of heat treatment is promoted. It is thought that the loss increased.

Nine sets of iron powder identical to Example material 1 were prepared, and a powder soft magnetic material molded at the same molding pressure (1200 MPa) was subjected to heat treatment in air at different temperatures and times respectively to evaluate core loss. .

Table 3 shows the evaluation results of the heat treatment temperature, the holding time, and the iron loss for 10 types of powder soft magnetic materials (example materials 1, 7 to 10, and comparative materials 6 to 10) having different heat treatment temperatures and holding times The core loss value) and the thickness of the oxidation affected layer are shown.

In the example materials 8 and 9, the heat treatment temperature is 500 ° C., and the holding time is 30 minutes and 120 minutes, respectively. The heat treatment temperature of the example materials 1 and 7 is 550 degreeC, and holding time is respectively 30 minutes and 60 minutes. The example material 10 has a heat treatment temperature of 600 ° C. and a holding time of 30 minutes. The comparative material 10 has a heat treatment temperature of 450 ° C. and a holding time of 30 minutes. The comparative material 7 has a heat treatment temperature of 500 ° C. and a holding time of 180 minutes. The comparative material 6 has a heat treatment temperature of 550 ° C. and a holding time of 120 minutes. The comparative material 8 has a heat treatment temperature of 600 ° C. and a holding time of 60 minutes. The comparative material 9 has a heat treatment temperature of 650 ° C. and a holding time of 30 minutes. The powder soft magnetic materials of Examples 1 and 7 to 10 were heat-treated at the heat treatment temperature and the holding time described above in “6) Best mode of heat treatment process”. The dusted soft magnetic bodies of Comparative Materials 6 to 10 were heat-treated outside the range of the heat-treatment temperature and the holding time.

In the powder soft magnetic material of each of the example materials 1 and 7 to 10, the core loss value is relatively small at 35 to 40 W / kg. On the other hand, in the case of the soft magnetic powder bodies of comparative materials 6 to 8 having a long holding time, the core loss value was a large value exceeding 40 W / kg. The core loss of the comparative material 9 held for 30 minutes at a heat treatment temperature of 650 ° C. also had a large value of 52 W / kg. In the pressed soft magnetic material of each of the example materials 1 and 7 to 10, the thickness of the oxidation affected layer is 0.6 mm or less. In the powder soft magnetic material of Comparative materials 6 to 9, the thickness of the oxidation affected layer is 1 mm or more, and the influence of oxidation is greater than that of Example materials 1 and 7 to 10 to the inside of the powder soft magnetic material. It is estimated that the iron loss has been increased by promoting it.

The powder soft magnetic material of the comparative material 10 was subjected to a heat treatment for 30 minutes at a temperature lower than the temperature range of the example materials 1 and 7 to 10 at 450 ° C. The powder soft magnetic material of the comparative material 10 had a very small thickness of 0.1 mm for the oxidation affected layer, but the core loss was a relatively large value of 48 W / kg. Although the effect of oxidation is small, the powder soft magnetic material of the comparative material 10 is presumed to have failed to sufficiently reduce iron loss since the heat treatment temperature is low and the reduction in strain in the iron powder is not sufficient.

From the above results, it was found that it is important to set the conditions of the temperature and holding time of the atmospheric heat treatment in an appropriate range in order to effectively extract the characteristics of the powder soft magnetic material according to the present invention .

INDUSTRIAL APPLICABILITY The powder soft magnetic material according to the present invention can be used for electromagnetic components in general, and for example, can be used for a rotor core and a stator core of a motor, an electromagnetic valve, a reactor, and the like.

DESCRIPTION OF SYMBOLS 1 ... Powdered-powder soft-magnetic body, 2 ... Iron powder, 3 ... Oxidation affected layer, 4 ... Unoxidized area | region, 10 ... Iron powder interface, 11 ... Oxide mainly containing Fe, 12 ... Fe-Si complex oxide, 13: massive Fe-P-Si complex oxide, 14: layered oxide mainly composed of Si, 21: lower layer mainly composed of Fe-P, 22: upper layer of Si-rich, 23: C, Organic layer mainly composed of O and Si, 31: white network, 32: gray structure.

Claims

A powder soft magnetic material produced by subjecting the surface of a metal powder containing iron powder as a main component to an insulation coating treatment and compacting the metal powder,
By heat treatment in an oxidizing atmosphere after the compacting, an oxidation affected layer which is a layer containing an iron oxide and a layered Si oxide is formed at the boundary between the iron powders.
Powdered soft magnetic material characterized by
The powder soft magnetic material according to claim 1, wherein
The surface of the iron powder is coated with an inorganic insulating layer containing phosphoric acid, and the inorganic insulating layer is further coated with an organic layer containing Si, whereby the insulating coating process is performed.
A dusted soft magnetic material produced by mixing a lubricant and compacting the metal powder.
It is a dust-powder soft-magnetic body of Claim 1 or 2, Comprising:
The oxidation-influenced layer contains Fe 2 SiO 4 and Fe 3 O 4 as oxides of iron and a layer of amorphous structure of SiO 2 with a thickness of 5 to 100 nm as oxides of layered Si. Powdered soft magnetic material.
It is a powder-powder soft-magnetic body of any one of Claim 1 to 3, Comprising:
It comprises a surface area including a surface and an inner area inside the surface area,
The oxidation affected layer is formed in the surface region, and the oxidation affected layer is not formed in the inner region,
The oxidation effect in the linear direction at an arbitrary point on the surface of the powder soft magnetic material and at a point where a straight line perpendicular to the surface passes through the inner area and the two surface areas sandwiching the inner area The powder soft magnetic material, wherein the total thickness of the layers is 1/16 or more and 1/2 or less of the thickness of the powder soft magnetic material in the linear direction.
It is a powder-powder soft-magnetic body of any one of Claim 1 to 4, Comprising:
When the temperature is 500 ° C. or more and less than 550 ° C., the oxidation influence layer has a holding time of 5 minutes or more 120 in an air atmosphere, a water vapor atmosphere, or an oxidation atmosphere in which 20% or less by volume of oxygen is added to an inert gas. The heat treatment under the condition that the holding time is 5 minutes or more and 60 minutes or less when the temperature is 550 ° C. or more and less than 600 ° C., and the holding time is 5 minutes or more and 30 minutes or less when the temperature is 600 ° C. or more and less than 650 ° C. Powdered soft magnetic material formed by
It is a powder-powder soft-magnetic body of Claim 4, Comprising:
In the inner region, the iron powder has an insulating covering layer containing Fe and P on the surface, and an organic layer containing C and O is formed at the boundary between the iron powders.
A powder soft magnetic material according to any one of claims 1 to 6, wherein
Density 7.45 g / cm 3 or more 7.75 g / cm 3 or less is powder soft magnetic material.
It is a powder-powder soft-magnetic body of any one of Claim 1 to 7, Comprising:
The powder soft magnetic material, wherein a ratio of the iron powder in the powder soft magnetic material is 94.0% to 98.5% by volume ratio.
It is a powder-powder soft-magnetic body of any one of Claim 1 to 8, Comprising:
The ratio of the iron powder having a particle size of 100 μm to 400 μm in the powder magnetic powder is 70% or more by weight, and the iron powder having a particle size of less than 100 μm is 30 by weight Powdered soft magnetic material which is less than 10%.
A motor using the powder soft magnetic material according to any one of claims 1 to 9 as at least one of a rotor core and a stator core.