JP2007126696A - METHOD FOR MANUFACTURING IRON POWDER HAVING SURFACE COATED WITH HIGH-Si LAYER - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide iron powder having a surface coated with high-Si layer in which a high-concentration Si diffusion layer is formed on the surface of iron powder and which is used for the production of various electromagnetic circuit components requiring high specific resistance. <P>SOLUTION: Iron powder is held at >900 to 1,250°C in a nonoxidizing atmosphere to undergo preliminary heat treatment, followed by pulverization. Then Si powder or ferrosilicon powder is added to the resultant pulverized iron powder and these are mixed. The resultant powder mixture is heated at 920 to 1,100°C in a hydrogen atmosphere to undergo heat treatment, followed by pulverization. By this method, the iron powder having a surface coated with high-Si layer can be manufactured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface high Si layer coated iron powder having a Si thermal diffusion layer on the surface of the iron powder and a method for producing the same, and a soft magnetic material produced using the surface high Si layer coated iron powder has a low It is used as a material for various electromagnetic circuit components that require iron loss, for example, various electromagnetic components such as motors, actuators, yokes, cores, and reactors.

  In general, soft magnetic materials used in various electromagnetic circuit components are required to have low iron loss. Therefore, electrical resistance is increased to reduce eddy current loss, and coercive force is reduced to reduce hysteresis loss. It is known. Furthermore, in recent years, since the miniaturization and high response of the electromagnetic circuit have been demanded, higher magnetic flux density is also regarded as important.

As an example of a raw material powder for producing such a soft magnetic material having a high specific resistance, Si is diffused on the surface of the iron powder, and the surface of the iron powder contains high Si containing a higher concentration of Si than Si contained in the iron powder. A surface high Si layer-coated iron powder having an average particle diameter of 1 to 200 μm formed with a concentration coating layer is provided. The surface high Si layer coated iron powder is obtained by converting the iron powder obtained by the atomization method to a temperature of 500 to After performing a pre-heat treatment to be held in an Ar atmosphere at 900 ° C., temperature: 800 to 900 ° C., a silicidation treatment to be held in an atmosphere of 10 to 50 Vol% SiCl ₄ + Ar, and further to a temperature of 500 to 900 ° C., Ar It is known to manufacture by performing a thermal diffusion treatment held in an atmosphere (see Patent Document 1).
Japanese Patent Laid-Open No. 11-87123

However, in the conventional method for producing a surface high Si layer-coated iron powder, the surface high Si layer-coated iron powder obtained by using SiCl ₄ gas contains chlorine, and this surface containing chlorine The high Si layer-coated iron powder is easily corroded, and it is difficult to handle the SiCl ₄ gas itself. Further, the coercive force of the surface high Si layer-coated iron powder obtained by the conventional method for producing a surface high Si layer-coated iron powder is as follows. As a raw material powder for producing a soft magnetic material, for example, it was not possible to sufficiently lower the temperature, satisfactory characteristics could not be obtained.

Therefore, the inventors of the present invention are to manufacture a surface high Si layer-coated iron powder having a further excellent magnetic property as a raw material powder for producing a soft magnetic material without using a difficult gas such as SiCl ₄ gas. I did research.
As a result, when the pre-heat treatment of the iron powder is performed in a non-oxidizing atmosphere such as vacuum, hydrogen, argon, etc. at a temperature higher than the conventional temperature: over 900 to 1250 ° C., the grain size of the iron powder grows. An iron pulverized powder having a large crystal grain size is obtained, and a mixed powder obtained by adding and mixing Si powder or ferrosilicon powder to the iron pulverized powder having a large crystal grain size is heated in a hydrogen atmosphere at a temperature of 920 to 1100 ° C. The result of the study was that the surface high Si layer-coated iron powder, which was further excellent in magnetic properties, was obtained as a raw material powder for producing a soft magnetic material when heated and ground.
This invention was made based on these research results,
(1) The iron powder is preheated by holding the iron powder in a non-oxidizing atmosphere at a temperature of over 900 to 1250 ° C. and then pulverized to produce an iron pulverized powder. The iron pulverized powder is mixed with Si powder or ferrosilicon powder. It is characterized by a method for producing a surface-high Si layer-coated iron powder that is added and mixed, then subjected to heat treatment at a temperature of 920 to 1100 ° C. in a hydrogen atmosphere, and then pulverized.

  The preliminary heat treatment performed in the method for producing the surface high Si layer-coated iron powder of the present invention is performed at a temperature exceeding 900 to 1250 ° C., even if the iron powder is subjected to the preliminary heat treatment at 900 ° C. or less, sufficient crystal grains are obtained during the preliminary heat treatment. The surface high Si layer coated iron powder produced by using the preheat-treated powder with no crystal growth and fine grain is not preferable because the coercive force cannot be lowered, while preheat treatment at a temperature exceeding 1250 ° C. Then, the sintering progressed too much and subsequent pulverization became difficult. Even if pulverization was possible, the residual amount of strain increased due to difficult pulverization, and the crystal grains were refined again. This is because the magnetic characteristics are not desirable because they are not desired.

  The reason why the heat treatment performed in the method for producing the surface high Si layer-coated iron powder of the present invention is performed at 920 to 1100 ° C. in a hydrogen atmosphere is the shortest in the non-oxidizing atmosphere by performing the heat treatment in the hydrogen atmosphere. This is because a high-concentration Si diffusion layer can be efficiently formed on the surface of the iron pulverized powder. If the temperature is less than 920 ° C., it is not preferable because only a normal slow diffusion rate can be obtained, while exceeding 1100 ° C. When the heat treatment is performed at a high temperature, sintering of the iron pulverized powder proceeds excessively, making pulverization difficult, and even if pulverized, the surface has a high Si concentration coating layer on the surface of the iron powder. This is because it is not preferable since the above cannot be obtained.

The iron powder used in the method for producing the surface high Si layer-coated iron powder of the present invention is preferably pure iron powder, but it is sufficient if the purity is 98.5% by mass or more, and carbon steel powder or the like may be used. I can do it. The particle size of the iron powder is not particularly limited, but it is preferable that the average particle size is in the range of 50 to 150 μm. Therefore, the present invention
(2) The iron powder has a feature in the method for producing a surface high Si layer-coated iron powder according to (1), which is an iron powder having a purity of 98.5% by mass or more.
The Si powder or ferrosilicon (Si: ferrosilicon containing 50% or more) powder added to and mixed with the iron powder used in the method for producing the surface high Si layer-coated iron powder of the present invention is a fine powder having a particle size of 10 μm or less. Preferably there is. The reason is that when the particle size of the Si powder or ferrosilicon powder exceeds 10 μm, it is larger than the iron powder of the raw material powder and does not disperse unevenly around the iron powder during mixing. Is not preferable because the surface of the iron powder is not coated with a uniform thickness. Therefore, the present invention
(3) The Si powder or ferrosilicon powder has a feature in the method for producing a surface high Si layer-coated iron powder according to (1), which is a fine powder having a particle size of 10 μm or less.

A soft magnetic material having further improved specific resistance and strength by mixing an organic insulating material or inorganic insulating material as a binder or a mixed material of an organic insulating material and an inorganic insulating material with the surface high Si layer-coated iron powder of the present invention. Can be produced. In this case, as the organic insulating material, epoxy resin, fluorine resin, phenol resin, urethane resin, silicone resin, polyester resin, phenoxy resin, urea resin, isocyanate resin, acrylic resin, polyimide resin, PPS resin, or the like can be used. . As the inorganic insulating material, phosphates such as iron phosphate, various glassy insulators, water glass mainly composed of sodium silicate, insulating oxides, and the like can be used. And it is preferable that the amount of binders added to surface high Si layer coating iron powder exists in the range of 0.2-3 mass%. The amount added is within a generally known range.
The mixed powder obtained by adding and mixing the binder to the surface high Si layer-coated iron powder of this invention is compacted, and the resulting compacted body is sintered at a temperature of 500 to 900 ° C. to produce a soft magnetic material. can do. This sintering temperature is a generally known temperature.
The soft magnetic material produced using the surface high Si layer coated iron powder of the present invention has high density, high strength, high specific resistance, high magnetic flux density and low coercive force, and this soft magnetic material has high magnetic flux density. Since it has the characteristics of high-frequency and low iron loss, it can be used as a material for various electromagnetic circuit components utilizing this characteristic. Examples of the electromagnetic circuit component include a magnetic core, a motor core, a generator core, a solenoid core, an ignition core, a reactor, a transformer, a choke coil core, and a magnetic sensor core. In addition, an electric device incorporating an electromagnetic circuit component made of a soft magnetic material using the oxide film-coated Fe-Si iron-based soft magnetic powder of the present invention includes an electric motor, a generator, a solenoid, an injector, an electromagnetically driven valve, an inverter There are converters, transformers, relays, magnetic sensor systems, etc., which can improve the efficiency, performance, size and weight of electrical equipment.

  When a soft magnetic material is manufactured using the surface high Si layer coated iron powder of this invention, it has a low specific eddy current loss due to its high specific resistance, and also has a low hysteresis loss due to its low coercive force. The material can be produced stably at a low cost, and has an excellent effect in the electric and electronic industries.

Pure iron powder having an average particle size of 80 μm obtained by atomization as a raw material powder and carbon steel powder having an average particle size of 80 μm obtained by atomization (component composition, mass%, C: 0.01% Si: 0.1%, Mn: 0.35%, P: 0.01%, S: 0.02%, the balance being Fe and inevitable impurities), and an average particle size of 5 μm A commercially available ferrosilicon powder having an Si powder having an average particle size of 5 μm and containing Si: 75% was prepared.
Example 1
First, pure iron powder is preheated in a vacuum, hydrogen, and argon atmosphere under the conditions shown in Table 1, and then pulverized to produce pure iron pulverized powder. Pure iron powder is then pulverized with pure Si powder. Powder: Pure Si powder = 97% by mass: 3% by mass, mixed to prepare a mixed powder, and the obtained mixed powder is heat-treated under the conditions shown in Table 1 and then pulverized. By carrying out 1 to 8 and Comparative Methods 1 to 5, the surface high Si layer-coated iron powder having a particle size of 150 or less with a high-concentration Si diffusion layer formed on the surface of the pure iron powder was produced.

After applying silane coupling treatment to the surface high Si layer-coated iron powder obtained by the present invention methods 1-8 and comparative methods 1-5, a silicone resin: 1.5% by mass is added as a binder, and then mixed. And pressed into a plate-shaped green compact having a length of 55 mm, a width of 10 mm, and a thickness of 5 mm, and a ring-shaped powder having an outer diameter of 35 mm, an inner diameter of 25 mm, and a height of 5 mm. The body was molded, and the obtained green compact was fired in a vacuum atmosphere at a temperature of 800 ° C. and held for 30 minutes to produce a soft magnetic material composed of a plate-like and ring-like fired body. The specific resistance of the soft magnetic material made of the fired body was measured and the results are shown in Table 2. Further, the soft magnetic material made of the ring-like fired body was wound, and the magnetic flux density, coercive force, magnetic flux density 1T, frequency Iron loss and magnetic flux density at 1 kHz 0.1 T, the magnetic properties such as iron loss at a frequency 10kHz were measured. The results are shown in Table 2.
Conventional Example 1
The pre-prepared pure iron powder was preliminarily heat-treated in a vacuum, hydrogen and Ar atmosphere at a temperature of 800 ° C. for 0.5 hours, and then the temperature was 800 ° C. and 15 Vol. The surface of the pure iron powder is obtained by performing the conventional method 1 by performing a siliconizing treatment for 0.5 hours in an atmosphere of% SiCl ₄ + Ar, and further maintaining in an Ar atmosphere at a temperature of 800 ° C. for 0.5 hours. The surface high Si layer coating iron powder in which the high concentration Si diffusion layer was formed was prepared.

  The obtained surface high Si layer-coated iron powder is subjected to a silane coupling treatment, and then added and mixed with a silicone resin: 1.5% by mass as a binder, and then put into a mold, press-molded, and length: 55 mm, width: A plate-shaped green compact having dimensions of 10 mm, thickness: 5 mm, and a ring-shaped green compact having dimensions of outer diameter: 35 mm, inner diameter: 25 mm, height: 5 mm, and forming the green compact into nitrogen Firing is performed in an atmosphere at a temperature of 500 ° C. for 30 minutes to produce a soft magnetic material made of a plate-like and ring-like fired body, and the specific resistance of the soft magnetic material made of the plate-like fired body is measured. The results are shown in Table 2, and a soft magnetic material made of a ring-shaped fired body is wound, and magnetic flux density, coercive force, magnetic flux density 1T, iron loss and magnetic flux density 0.1T at a frequency of 1 kHz, Iron at a frequency of 1 kHz The magnetic characteristics such as measured, The results are shown in Table 2.

From the results shown in Tables 1 and 2, the soft magnetic material using the surface-high Si layer-coated iron powder produced in the inventive methods 1 to 8 of Example 1 is the surface height produced in the conventional method 1 of Conventional Example 1. Compared with the soft magnetic material using the Si layer-coated iron powder, there is no significant difference in density, but the soft magnetic material using the surface high Si layer-coated iron powder produced by the inventive methods 1 to 8 of Example 1 is Compared with the soft magnetic material using the surface high Si layer-coated iron powder produced by the conventional method 1 of the conventional example 1, the magnetic flux density is high, the coercive force is small, and the specific resistance is high, so that the iron loss, particularly 1 kHz. It turns out that it has the characteristic that the iron loss in the above high frequency region becomes small. However, it can be seen that the soft magnetic material using the surface high Si layer-coated iron powder produced by Comparative Methods 1 to 5 under conditions deviating from the conditions of the present invention has some undesirable characteristics.
Example 2
Next, the prepared carbon steel powder is preheated in a vacuum, hydrogen, argon atmosphere under the conditions shown in Table 3 and then pulverized to produce a pulverized carbon steel powder. The obtained ferrosilicon powder was blended so that the pulverized carbon steel powder: ferrosilicon powder = 98% by mass: 2% by mass and mixed to prepare a mixed powder. The obtained mixed powder was subjected to the conditions shown in Table 3. By carrying out the present invention methods 9 to 16 and comparative methods 6 to 10 which were heat-treated and then ground, a high-Si surface-coated iron powder having a high-concentration Si diffusion layer formed on the surface of the carbon steel powder was produced.

After applying silane coupling treatment to the surface high Si layer-coated iron powder obtained by the present invention methods 9 to 16 and comparative methods 6 to 10, a silicone resin: 1.5% by mass is added as a binder, and then mixed. And pressed into a plate-shaped green compact having a length of 55 mm, a width of 10 mm, and a thickness of 5 mm, and a ring-shaped powder having an outer diameter of 35 mm, an inner diameter of 25 mm, and a height of 5 mm. The body was molded, and the obtained green compact was fired in a nitrogen atmosphere at a temperature of 500 ° C. for 30 minutes to produce a soft magnetic material comprising a plate-like and ring-like fired body. The specific resistance of the soft magnetic material made of the fired body was measured and the results are shown in Table 4. Further, the soft magnetic material made of the ring-like fired body was wound, and the magnetic flux density, coercive force, magnetic flux density 1T, frequency Iron loss and magnetism at 1 kHz Density 0.1 T, the magnetic properties such as iron loss at a frequency 10kHz were measured. The results are shown in Table 4.
Conventional example 2
The previously prepared carbon steel powder was pre-heated in an Ar atmosphere at a temperature of 800 ° C. and held for 0.5 hours, and then the temperature was 800 ° C. and 15 Vol. The surface of the carbon steel powder is obtained by performing the conventional method 2 by performing a siliconization treatment for 0.5 hours in a% SiCl ₄ + Ar atmosphere, and further maintaining the temperature in the Ar atmosphere at 800 ° C. for 0.5 hours. The surface high Si layer coating iron powder in which the high concentration Si diffusion layer was formed was prepared.

  Epoxy resin as a binder is added to the obtained surface high Si layer-coated iron powder, mixed in 1% by mass, put into a mold, and press-molded to have dimensions of 55 mm in length, 10 mm in width, and 5 mm in thickness. A plate-shaped green compact and a ring-shaped green compact having dimensions of an outer diameter of 35 mm, an inner diameter of 25 mm, and a height of 5 mm were formed, and the obtained green compact was placed in a nitrogen atmosphere at a temperature of 500 ° C. for 30 minutes. Firing is performed under the holding conditions to produce a soft magnetic material made of a plate-like and ring-like fired body, the specific resistance of the soft magnetic material made of this plate-like fired body is measured, and the results are shown in Table 4, Winding is applied to a soft magnetic material made of a ring-shaped fired body, and magnetic flux density, coercive force, and magnetic loss such as iron loss at a magnetic flux density of 1T and a magnetic flux density of 0.1T and a magnetic flux density of 0.1T and a frequency of 10 kHz. Measure the properties and It is shown in Table 4.

From the results shown in Tables 3 to 4, the soft magnetic material using the surface high Si layer-coated iron powder produced by the inventive methods 9 to 16 of Example 2 is the surface height produced by the conventional method 2 of Conventional Example 2. Compared with the soft magnetic material using the Si layer-coated iron powder, the density is not much different, but the soft magnetic material using the surface high Si layer-coated iron powder produced by the inventive methods 9 to 16 of Example 2 is Compared with the soft magnetic material using the surface high Si layer-coated iron powder prepared by the conventional method 2 of the conventional example 2, the magnetic flux density is high, the coercive force is small, and the specific resistance is high, so that the iron loss, particularly 1 kHz. It turns out that it has the characteristic that the iron loss in the above high frequency region becomes small. However, it can be seen that the soft magnetic material using the surface high Si layer-coated iron powder produced by Comparative Methods 6 to 10 under conditions other than the conditions of the present invention has some undesirable characteristics.

Claims (8)

The iron powder is preheated by holding the iron powder in a non-oxidizing atmosphere at a temperature exceeding 900 to 1250 ° C. and then pulverized to produce an iron pulverized powder. The iron pulverized powder is mixed with Si powder or ferrosilicon powder. After that, a method for producing a surface high Si layer-coated iron powder characterized by heating in a hydrogen atmosphere at a temperature of 920 to 1100 ° C. and then pulverizing. The method for producing a surface high Si layer-coated iron powder according to claim 1, wherein the iron powder is an iron powder having a purity of 98.5% by mass or more. 2. The method for producing a surface high Si layer-coated iron powder according to claim 1, wherein the Si powder or ferrosilicon powder is a fine powder having a particle size of 10 [mu] m or less. The surface high Si layer-coated iron powder produced by the method according to claim 1, 2 or 3 is added with 0.2 to 3 mass% of binder and then compacted, and the compact is fired at 500 to 900 ° C. A method for producing a composite soft magnetic material, comprising: The binder according to claim 4 is an epoxy resin, a fluororesin, a silicone resin, a polyimide resin, a polyester resin, a polyamide resin, an organic resin such as a phenol resin, a phosphate, a glassy insulator, or water mainly composed of sodium silicate. A method for producing a composite soft magnetic material, characterized by being made of glass or an insulating oxide. An electromagnetic circuit component comprising a composite soft magnetic material produced by the method according to claim 4. The electromagnetic circuit component according to claim 6, wherein the electromagnetic circuit component is a magnetic core, a motor core, a generator core, a solenoid core, an ignition core, a transformer core, a choke coil core, or a magnetic sensor core. An electric device incorporating the electromagnetic circuit component according to claim 7.