JP2014515880A - Novel compositions and methods - Google Patents

Abstract

  The present invention relates to a composite iron-based powder mixture suitable for soft magnetic applications such as inductor cores. The invention also relates to a method of manufacturing a soft magnetic component and a component manufactured by this method.

Description

  The present invention relates to a soft magnetic composite powder material for preparing a soft magnetic component and a soft magnetic component obtained by using this soft magnetic composite powder. Specifically, the present invention relates to such powders for preparing soft magnetic component materials that operate at high frequencies, which components are suitable as inductors or reactors for power electronics.

  Soft magnetic materials are used in a variety of applications such as inductors, stators and rotors in electrical machines, actuators, sensors, and core materials for transformer cores. Traditionally, soft magnetic cores such as rotors and stators in electrical machines are made of laminated steel laminate. Soft magnetic composites can be based on normally iron-based soft magnetic particles with an electrically insulating coating on each particle. Soft magnetic parts can be obtained by compressing the insulating particles, optionally with a lubricant and / or binder, using traditional powder metallurgy. Since the part can provide a three-dimensional magnetic flux and the three-dimensional shape is obtained by the compression process, the use of powder metallurgy technology can produce parts with a higher degree of design freedom than using a steel laminate. Is possible.

  The present invention is an iron-based soft magnetic composite powder, the core particles of which are carefully selected coatings that give the material suitable material properties for manufacturing inductors through powder compaction and subsequent heat treatment steps. It relates to the powder being coated.

  An inductor or reactor is a passive electrical component that can store energy in the form of a magnetic field created by the current passing therethrough. Inductance (L), the ability of an inductor to store energy, is measured in Henry (H).

  Typically, an inductor is an insulated wire wound as a coil. The current flowing through the coil turns creates a magnetic field around the coil, the strength of the magnetic field being proportional to the current and the coil turns / length unit. A changing current creates a changing magnetic field that induces a voltage opposite to the change in current that created it.

The electromagnetic force (EMF) opposite to the change in current is measured in volts (V) and the equation v (t) = L di (t) / dt
(L is inductance, t is time, v (t) is a time-varying voltage between inductors, and i (t) is a time-varying current)
Is related to the inductance by That is, an inductor with an inductance of 1 Henry produces an EMF of 1 volt when the current through the inductor changes at 1 ampere / second.

  Ferromagnetic or iron-core inductors are magnetic cores made of ferromagnetic or ferrimagnetic materials, such as iron or ferrite, that increase the inductance of the coil by increasing the magnetic field due to the high permeability of the core material. use.

The magnetic permeability of the material, μ, is an indicator of the ability to provide magnetic flux or magnetize. The permeability is indicated as B and is the induced magnetic flux measured in Newton / Ampere ^* meter or Volts ^* sec / Meter ² and is indicated as H and the magnetizing force or magnetic field measured in Amps / meter, A / m. Defined as the ratio of strength. Thus, the permeability has dimensions of volts ^* second / ampere ^* meter. Usually, the permeability is expressed as the relative permeability μ _r = μ / μ ₀ relative to the permeability of free space, μ ₀ = 4 ^* Π ^* 10 ⁻⁷ Vs / Am.

  Permeability can also be expressed as inductance per unit length, Henry / meter. The permeability depends not only on the material that provides the magnetic flux, but also on the applied electric field and its frequency. In technical systems, this is usually referred to as the maximum relative permeability, which is the maximum relative permeability measured during one cycle of the changing electric field.

Inductor cores can be used in power electronics systems to filter unwanted signals such as various harmonics. To function efficiently, inductor cores for such applications have a low maximum relative permeability, i.e. stable incremental permeability, which implies that the relative permeability has a more linear characteristic with respect to the applied electric field. Should have magnetic susceptibility, μ _Δ (defined according to ΔB = _μΔ ^* ΔH), and high saturation flux density. This allows the inductor to work more efficiently with a wider range of currents, which can also be described as having a “good DC bias”. The DC bias can be expressed in terms of the percentage of maximum incremental permeability at a specified applied electric field, eg, 4000 A / m. Further lower maximum relative permeability and stable incremental permeability combined with high saturation flux density allows the inductor to conduct higher currents, which is particularly advantageous when size is a limiting factor, and therefore smaller inductors Can be used.

  One important parameter to improve the performance of soft magnetic components is to reduce its core loss characteristics. When a magnetic material is exposed to a changing magnetic field, energy loss occurs due to both hysteresis loss and eddy current loss. Hysteresis loss is proportional to the frequency of the alternating magnetic field, while eddy current loss is proportional to the square of the frequency. Therefore, at high frequencies, eddy current loss is a major problem, and it is particularly necessary to maintain low level hysteresis loss while reducing eddy current loss. This implies that it is desirable to increase the resistivity of the magnetic core.

  Various methods have been used and proposed in the search for methods to improve resistivity. One method is based on providing an electrically insulating coating or film on these particles before subjecting them to compression. For example, there are numerous patent publications that teach various types of electrically insulating coatings. Examples of published patents relating to inorganic coatings are US Pat. No. 6,309,748, US Pat. No. 6,348,265 and US Pat. No. 6,562,458. Organic coatings are known, for example, from US Pat. No. 5,595,609. Coatings comprising both inorganic and organic materials are known, for example, from US Pat. Nos. 6,372,348 and 5,063,011 and German Patent Publication 3,439,397, and these publications. According to this, the particles are surrounded by an iron phosphate layer and a thermoplastic material. European patent EP 1246209B1 describes a ferromagnetic metal-based powder in which the surface of the metal-based powder is coated with a coating consisting of silicone resin and fine clay mineral particles having a layered structure such as bentonite or talc.

  US Pat. No. 6,756,118 discloses a soft magnetic powder metal composite comprising at least two oxides encapsulating powdered metal particles, the oxide forming at least one common phase. ing.

  JP 2002-170707 describes alloy iron particles coated with a phosphorous-containing layer, where the alloy element can be silicon, nickel or aluminum. In the second step, the coated powder is mixed with an aqueous sodium silicate solution and subsequently dried. The powder magnetic core is manufactured by molding the powder and heat-treating the molded part at a temperature of 500-1000 ° C.

  Sodium silicate is mentioned in JP 51-089198 as a binder for iron powder particles in the production of powder magnetic cores by forming iron powder and subsequently heat treating the molded article.

  In order to obtain high performance soft magnetic composite parts, it is usually desirable to obtain high density parts, so it must be possible to subject the electrically insulating powder to compression molding at high pressure. High density usually improves magnetic properties. A particularly high density is required to maintain the hysteresis loss at a low level and to obtain a high saturation magnetic flux density. Furthermore, the electrical insulation must withstand the required compression pressure without damage when the compressed part is removed from the die. This also means that the extraction force must not be too high.

  In addition, stress relief heat treatment of the compressed parts is necessary to reduce hysteresis loss. In order to obtain effective stress relief, the heat treatment should preferably be carried out at a temperature above 300 ° C. and below the temperature at which the insulating coating is damaged, for example in an atmosphere of nitrogen, argon or air or in a vacuum.

  The present invention takes into account the need for a powder core primarily intended for use at higher frequencies where higher resistivity and lower core loss are essential, ie above 2 kHz, especially 5-100 kHz. It was done. Preferably, the saturation flux density should be high enough for core miniaturization. Furthermore, it should be possible to produce cores without the need to compress metal powder using die wall lubrication and / or high temperatures. Preferably these steps should be removed.

  In contrast to many uses and proposed methods where low core loss is desired, it is a particular advantage of the present invention that it is not necessary to use an organic binder in a powder composition that is subsequently compressed in a compression step. Therefore, the green compact heat treatment can be performed at a higher temperature without the risk of decomposition of the organic binder, and the higher heat treatment temperature also improves the magnetic flux density and reduces core loss. The absence of organic material in the final heat treated core also allows the core to be used in high temperature environments without incurring strength loss due to softening and decomposition of the organic binder, and thus temperature stable Sexual improvement is achieved.

  It is an object of the present invention to provide a novel iron-based composite powder comprising a core of iron-based powder coated on the surface with a novel composite electrical insulation coating. The novel iron-based composite powder is particularly suitable for use in the manufacture of inductor cores for power electronics.

  Another object of the present invention is to provide a method of manufacturing such an inductor core.

  Yet another object of the present invention is to provide an inductor core having “good” DC bias, low core loss and high saturation flux density.

  The present invention provides, for example, an iron powder mixture that can be used to prepare an inductor having a high saturation magnetic flux density, low core loss, and a process method for processing the mixture, and simplifies the manufacturing process. Can do.

At least one of these objectives is achieved by:
A coated iron-based powder composition, the coating comprising a first phosphorus-containing layer and a second layer comprising a combination of particles of clay containing alkali silicate and a defined phyllosilicate; An iron-based powder composition comprising a mixture of iron powder and sendust (in one embodiment, the coating consists of only the two layers).
-A) providing a coated iron powder composition as described above;
b) compressing the coated iron and sendust powder mixture, optionally mixed with a lubricant, in a die in a uniaxial press motion at a compression pressure of 400-1200 MPa;
c) extracting the compressed part from the die;
d) heat treating the part extracted at a temperature up to 800 ° C.
-Parts such as inductor cores manufactured according to the above.

The composition may be a composite iron-based powder composition comprising core particles coated with a layer comprising an alkali silicate combined with a clay mineral comprising a phyllosilicate, the combined silicon-oxygen tetrahedral layer and its water The oxide octahedral layer is preferably electrically neutral and the core particles are (a) 7% to 13% by weight silicon, 4% to 7% aluminum, and the balance. A mixture of iron alloy particles consisting essentially of iron, and (b) atomized iron particles.

  The iron alloy particles may also be referred to as “sendust” or “sendust particles”.

  In one embodiment, Sendust particles are coated with a phosphorus-containing layer prior to coating with the alkali silicate in combination with a clay mineral comprising phyllosilicate. For simplicity, this coating can be referred to as an “alkali silicate coating” or “clay coating”. This coating can be based, for example, on kaolin or talc.

  In another embodiment, both iron alloy particles and atomized particles are coated with a phosphorus-containing layer prior to coating with the alkali silicate coating.

  Throughout this specification, the terms “layer” and “coating” may be used interchangeably.

  The iron particles can be in the form of pure iron powder with a low content of contaminants such as carbon or oxygen. The iron content is preferably above 99.0% by weight, but it may also be possible to utilize iron powders alloyed with silicon, for example. For pure iron powders or iron-based powders alloyed with intentionally added alloying elements, in addition to iron and possible existing alloying elements, the powder contains trace amounts resulting from inevitable impurities introduced by the manufacturing process. Contains elements. Trace elements are present in small amounts that do not affect (or only slightly) the properties of the material. Examples of trace elements can be up to 0.1% carbon, up to 0.3% oxygen, up to 0.3% sulfur and phosphorus, respectively, and up to 0.3% manganese.

  The particle size of the iron-based powder is determined by the intended use, i.e. for which frequency the component is suitable. The average particle size of the iron-based powder, which is also the average particle size of the coated powder because the coating is very thin, can be between 20 and 300 μm. Examples of average particle sizes for suitable iron-based powders are, for example, 20-80 μm, so-called 200 mesh powder, 70-130 μm, 100 mesh powder or 130-250 μm, 40 mesh powder.

  The iron alloy particles can consist essentially of 7 wt% to 13 wt% silicon, 4 wt% to 7 wt% aluminum, and the balance iron. The rest are impurities. Such powders are known in the art as sendust. Typically, Sendust contains essentially 84-86% Fe, 9-10% Si, and 5-6% Al by weight.

  The iron particles can be water atomized or gas atomized. Methods for atomizing iron are known in the literature.

  Phosphorus-containing coatings commonly applied to bare iron-based powders can be applied according to the method described in US Pat. No. 6,348,265. This means that iron or iron-based powder is mixed with phosphoric acid dissolved in a solvent such as acetone and subsequently dried to obtain a thin phosphorus and oxygen containing coating on the powder. The amount of solution added depends in particular on the particle size of the powder, but this amount should be sufficient to obtain a coating having a thickness of 20-300 nm.

  Alternatively, a thin phosphorus-containing coating can be added by mixing the iron-based powder with a solution of ammonium phosphate dissolved in water or by using other combinations of phosphorus-containing materials and other solvents. there will be. The resulting phosphorus-containing coating results in an increase in the phosphorus content of the iron-based powder from 0.01 to 0.15%.

The powder is mixed with particles of clay or a mixture of clays containing the defined phyllosilicate and a water-soluble alkali silicate commonly known as water glass, followed by a drying step at a temperature of 20-250 ° C. or in a vacuum. Apply an alkaline silicate coating to the phosphorus-coated iron-based powder. The phyllosilicate constitutes a silicate of the type in which silicon tetrahedra are connected to each other in the form of layers having the formula (Si ₂ O ₅ ²⁻ ) _n . These layers combine with at least one octahedral hydroxide layer to form a combined structure. The octahedral layer can include, for example, either aluminum hydroxide or magnesium hydroxide, or a combination thereof. Silicon in the silicon tetrahedral layer may be partially substituted with other atoms. These combined layered structures can be electrically neutral or charged depending on which atoms are present.

  It has been found that the type of phyllosilicate is extremely important for realizing the object of the present invention. Accordingly, the phyllosilicate should be of the type having an uncharged or electrically neutral layer of combined silicon tetrahedron- and hydroxide octahedron-layers. Examples of such phyllosilicates are kaolinite present in clay kaolin, phyllite present in phyllite, or magnesium-containing mineral talc. The average particle size of the clay comprising the phyllosilicate as defined should be less than 15 μm, preferably less than 10 μm, preferably less than 5 μm and even more preferably less than 3 μm. The amount of clay containing the defined phyllosilicate mixed with the coated iron-based powder should be 0.2-5% by weight of the coated composite iron-based powder, preferably 0.5-4% It is.

The amount of alkali silicate calculated as solid alkali silicate mixed with the coated iron-based powder is 0.1-0.9% by weight of the coated composite iron-based powder, preferably of this iron-based powder. Should be between 0.2 and 0.8% by weight. It has been shown that various types of water-soluble alkali silicates can be used, for example, sodium silicate, potassium silicate and lithium silicate. In general, water-soluble alkali silicates are characterized by their ratio, that is, the amount of SiO ₂ ÷ the amount of Na ₂ O, K ₂ O or Li ₂ O (as either a molar or weight ratio depending on the case). It is done. The molar ratio of water soluble alkali silicate should be 1.5-4 (inclusive). If the molar ratio is less than 1.5, the solution becomes too alkaline, and if the molar ratio exceeds 4, SiO ₂ precipitates.

  It may be possible to omit the second kaolin-sodium silicate coating on the sendust particles and still achieve excellent magnetic properties. However, in order to further enhance the magnetic properties, the second coating layer should cover both Sendust and iron powder.

  In an alternative embodiment, the alkali silicate (or clay) coating can be replaced with a metal-organic coating (second coating).

In this case, at least one metal-organic layer is arranged outside the first phosphorus base layer. The metal-organic layer has the general formula R ₁ [(R ₁ ) _x (R ₂ ) _y (MO _n-1 )] _n R ₁
[Where:
M is a central atom selected from Si, Ti, Al or Zr;
O is oxygen,
R ₁ is a hydrolyzable group,
R ₂ is an organic moiety, at least one R ₂ contains at least one amino group,
n is the number of repeatable units, which is an integer from 1 to 20,
x is an integer from 0 to 1 and y is an integer from 1 to 2 (thus x can be 0 or 1 and y can be 1 or 2)]
A metal-organic compound layer having

  The metal-organic compound may be selected from the following group: surface modifier, coupling agent or crosslinker.

R ₁ in the metal-organic compound may be an alkoxy group having less than 4, preferably less than 3 carbon atoms.

R ₂ is an organic moiety, which means that the R ₂ group contains an organic moiety or moiety. R ₂ can contain 1 to 6, preferably 1 to 3 carbon atoms. R ₂ can further include one or more heteroatoms selected from the group consisting of N, O, S and P. The R ₂ group can be linear, branched, cyclic or aromatic.

R ₂ includes one or more of the following functional groups: amine, diamine, amide, imide, epoxy, hydroxyl, ethylene oxide, ureido, urethane, isocyanato, acrylate, glyceryl acrylate, benzyl-amino, vinyl-benzyl-amino. be able to. The R ₂ group can vary between any of the mentioned R ₂ -functional groups and a hydrophobic alkyl group with respect to repeatable units.

  The metal-organic compounds may be selected from silanes, siloxanes and silsesquioxanes or the corresponding titanate, aluminate or zirconate derivatives, intermediates or oligomers.

  According to one embodiment, at least one metal-organic compound in one metal-organic layer is a monomer (n = 1).

  According to another embodiment, the at least one metal-organic compound in one metal-organic layer is an oligomer (n = 2-20).

  According to another embodiment, the metal-organic layer disposed outside the first layer is a metal-organic compound monomer layer, wherein the outermost metal-organic layer is a metal-organic compound oligomer. Layer. The chemical functionality of the monomer and oligomer is not necessarily the same. The ratio by weight of the metal-organic compound monomer layer to the metal-organic compound oligomer layer may be between 1: 0 and 1: 2, preferably between 2: 1 and 1: 2.

  When the metal-organic compound is a monomer, it can be selected from the group of trialkoxy and dialkoxysilanes, titanates, aluminates or zirconates. Therefore, the monomer of the metal-organic compound is 3-aminopropyl-trimethoxysilane, 3-aminopropyl-triethoxysilane, 3-aminopropyl-methyl-diethoxysilane, N-aminoethyl-3-aminopropyl-tri Methoxysilane, N-aminoethyl-3-aminopropyl-methyl-dimethoxysilane, 1,7-bis (triethoxysilyl) -4-azaheptane, triamino-functional propyl-trimethoxysilane, 3-ureidopropyl-triethoxy Silane, 3-isocyanatopropyl-triethoxysilane, tris (3-trimethoxysilylpropyl) -isocyanurate, O- (propargyloxy) -N- (triethoxysilylpropyl) -urethane, 1-aminomethyl-triethoxy Silane, 1-aminoethyl - methyl - it may be selected from silane or a mixture thereof.

  The oligomer of the metal-organic compound may be selected from alkoxy-terminated alkyl-alkoxy-oligomers of silane, titanate, aluminate or zirconate. Thus, oligomers of metal-organic compounds are methoxy, ethoxy or acetoxy-terminated amino-silsesquioxane, amino-siloxane, oligomer 3-aminopropyl-methoxy-silane, 3-aminopropyl / propyl-alkoxy-silane, N -Aminoethyl-3-aminopropyl-alkoxy-silane or N-aminoethyl-3-aminopropyl / methyl-alkoxy-silane or mixtures thereof.

  The total amount of metal-organic compound is 0.05-0.6% by weight of the composition, preferably 0.05-0.5% by weight, more preferably 0.1-0.4% by weight, most preferably 0. It may be from 2 to 0.3% by weight. These types of metal-organic compounds are available from Evonik Ind. , Commercially available from companies such as Wacker Chemie AG, Dow Corning and the like.

  The metal-organic compound has alkaline properties and can also include coupling properties, i.e. so-called coupling agents that are linked to the first inorganic layer of the iron-based powder. This material should neutralize excess acid and acidic by-products from the first layer. If an aminoalkylalkoxy-silane, -titanate, -aluminate, or -zirconate group of coupling agents is used, this material will hydrolyze and partially polymerize (thus some of the alkoxy groups are It will be hydrolyzed by the formation of alcohol). Metal-organic compound coupling or cross-linking properties may also be associated with metal or metalloid particulate compounds, which may improve the mechanical stability of the compressed composite part.

Metal or metalloid fine particle compound The coated soft magnetic iron-based powder may also comprise at least one metal or metalloid fine particle compound. The metal or metalloid particulate compound should be soft and have a Mohs hardness of less than 3.5 and constitute a particulate or colloid. The compound can preferably have an average particle size of less than 5 μm, preferably less than 3 μm, most preferably less than 1 μm. The metal or metalloid particulate compound can have a purity of greater than 95 wt%, preferably greater than 98 wt%, and most preferably greater than 99 wt%. The Mohs hardness of the metal or metalloid fine particle compound is preferably 3 or less, more preferably 2.5 or less. SiO ₂ , Al ₂ O ₃ , MgO and TiO ₂ are abrasive and have a Mohs hardness well above 3.5 and therefore are not within the scope of the present invention. Abrasive compounds, even nano-sized particles, cause irreversible damage to the electrically insulating coating, resulting in poor extraction of heat treated parts and poor magnetic and / or mechanical properties.

  The metal or metalloid fine particle compound may be at least one selected from the following group: lead, indium, bismuth, selenium, boron, molybdenum, manganese, tungsten, vanadium, antimony, tin, zinc, cerium.

  The metal or metalloid particulate compound can be an oxide, hydroxide, hydrate, carbonate, phosphate, fluoride), sulfide, sulfate, sulfite, acid chloride or a mixture thereof.

  According to a preferred embodiment, the metal or metalloid particulate compound is bismuth, more preferably bismuth (III) oxide. The metal or metalloid fine particle compound can be mixed with a second compound selected from alkali metals or alkaline earth metals, which compounds are carbonates, preferably calcium, strontium, barium, lithium, potassium or sodium. It can be carbonate.

  The metal or metalloid fine particle compound or compound mixture is in an amount of 0.05 to 0.5% by weight of the composition, preferably 0.1 to 0.4% by weight, most preferably 0.15 to 0.3% by weight. Can exist in

  A metal or metalloid particulate compound is adhered to at least one metal-organic layer. In one embodiment of the present invention, a metal or metalloid particulate compound is adhered to the outermost metal-organic layer.

The metal-organic layer is first composed of a basic aminoalkyl-alkoxysilane (Dynasylan (registered trademark in any country) Ameo, Evonik Inc), followed by an aminoalkyl / alkyl-alkoxysilane (Dynasylan (any country)). ) 1146, manufactured by Evonik Inc.), each in various amounts, for example by mixing using a 1: 1 relationship, and may be formed by mixing the powder. The composition can be further mixed with various amounts of fines of bismuth (III) oxide (> 99% by weight; D ₅₀ about 0.3 μm).

  This good saturation flux density achieved with the material according to the invention makes it possible to miniaturize the inductor component and still maintain good magnetic properties.

Compression and heat treatment Prior to compression, the coated iron-based composition may be mixed with a suitable organic lubricant, such as waxes, oligomers or polymers, fatty acid derivatives or combinations thereof. Examples of suitable lubricants are EBS, ie, ethylene bisstearamide, Hoganas AB, Kenolube (registered trademark in any country) commercially available from Sweden, metal stearates or fatty acids such as zinc stearate or These are other derivatives. The lubricant can be added in an amount of 0.05 to 1.5% by weight, preferably 0.1 to 1.2% by weight of the total mixture.

  The compression can be carried out at a compression pressure of 400 to 1200 MPa at ambient or elevated temperature.

  After compression, the compressed part is subjected to a heat treatment at a temperature up to 800 ° C, preferably at a temperature of 600-750 ° C. An example of a suitable atmosphere in the heat treatment is an inert atmosphere such as nitrogen or argon or an oxidizing atmosphere such as air.

  The powder magnetic core of the present invention can be obtained by pressure molding iron-based magnetic powder covered with a novel electrically insulating coating. The core can be characterized by a low total loss of less than about 12 W / kg at a frequency of 20 kHz and an induction of 0.05 T in the frequency range 2-100 kHz, usually 5-100 kHz. Further, the resistivity, ρ, is greater than 1000 μΩm, preferably greater than 2000 μΩm, most preferably greater than 3000 μΩm, and the saturation magnetic flux density Bs is greater than 1.1 T, preferably greater than 1.2 T, and most preferably greater than 1.3 T. Furthermore, the coercivity should be less than 210 A / m, preferably less than 200 A / m, most preferably less than 190 A / m, and the DC bias should be greater than 50% at 4000 A / m.

  The following examples are intended to illustrate particular embodiments and should not be construed as limiting the scope of the invention.

(Example 1)
Two types of iron powder were used as core particles; water atomized pure iron powder having an iron content of more than 99.5% by weight and pure sponge iron having an iron content of more than 99.5% by weight. The average particle size of both types of powder was about 45 μm. The core particles were mixed with ground sendust (typically 85% Fe, 9.5% Si and 5.5% Al) and then the powder mixture was treated with a phosphorus-containing solution according to WO2008 / 069749. Briefly, a coating solution was prepared by dissolving 30 ml of 85% by weight phosphoric acid in 1000 ml of acetone, and 40 ml to 60 ml of acetone solution was used per 1000 g of powder. After mixing the phosphoric acid solution with the metal powder, the mixture is dried.

  The resulting dry phosphorus coated iron-sendust mixed powder was further blended with kaolin and sodium silicate according to Table 1 below. After drying at 120 ° C., the powder was mixed with 0.6% Kenolube (registered trademark in any country) and compressed at 800 MPa into a ring with an inner diameter of 45 mm, an outer diameter of 55 mm and a height of 5 mm. Thereafter, the compressed part was subjected to a heat treatment step at 700 ° C. for 0.5 hour in a nitrogen atmosphere.

The specific resistivity of the obtained sample was measured by a four-point measurement method. The ring was “wound” 100 turns for the primary circuit and 100 turns for the secondary circuit for maximum permeability, μ _max and coercivity measurements. This makes it possible to measure the magnetic properties using the hysteresis graph, Blockhouse MPG100. Due to core loss, Walker Scientific Inc. Using an AMH-401 POD device, the ring was “rolled” 30 times for the primary circuit and 30 times for the secondary circuit.

  When measuring incremental permeability, the ring was wound with a third winding that supplied a DC bias current of 4000 A / m. DC bias was expressed as a percentage of maximum incremental permeability.

  Unless otherwise stated, all tests in the following examples were conducted in this manner.

To show the effect of using sponge or atomized iron in combination with milled sendust on the properties of the compressed and heat treated parts, the effect of the phosphorus coating layer and the presence of kaolin and sodium silicate in the second coating Samples A to H were prepared according to Table 1. Table 1 also shows the results of part testing. In Table 1, the present invention was also compared to the use of sponge iron (Sample D) without the first phosphorus coating layer according to US 4177089.

  As can be seen from Table 1, the combination of atomized iron, Sendust, the first phosphorus coating layer and the second coating layer consisting of kaolin and sodium silicate significantly improves resistivity and thus reduces core loss. This also results in better saturation flux density compared to 100% sendust.

(Example 2)
To demonstrate the possibility of doping pure phosphorus with kaolin-sodium silicate coating atomized iron powder with only the first phosphorus coating layer and significantly enhancing the magnetic properties of the compressed parts Samples were prepared. Table 2 also shows the results of part testing.

  As can be seen from Table 2, it is advantageous to have a first phosphorus coating layer on the sendust particles.

(Example 3)
By changing the sendust content in the atomized iron powder, it is possible to control the magnetic properties of the compressed and heat treated parts. All of the following samples were similarly treated with a first layer of phosphorus coating and a second layer coating consisting of 2% kaolin clay and 0.4% sodium silicate, compressed to 800 MPa, and 0 ° C. at 700 ° C. in a nitrogen atmosphere. Heat treated for 5 hours. The difference between the samples is that the sendust content of atomized iron powder was changed. Table 3 also shows the results of part testing.

  As can be seen from Table 3, Sendust in atomized iron powder enhances the magnetic properties of parts that have been compressed and heat treated even in small amounts.

(Example 4)
This example shows that the phosphorus-clay-silicate coating concept according to the present invention can be applied to iron powders of various particle sizes-Sendust powder has a fixed particle size of about 45 μm. For sample V), iron powder having an average particle size of ˜45 μm was used. For sample W), iron powder having an average particle size of ˜100 μm was used. For sample X), iron powder having an average particle size of ˜210 μm was used. The iron-sendust powder mixture was coated with a first phosphorus-containing layer. Several samples were then further treated with 1% kaolin and 0.4% sodium silicate as described above. The heat treatment was performed at 700 ° C. for 0.5 hours under nitrogen.

Results of tests on samples V to X) according to Table 4

  Table 4 shows that a clear improvement in resistivity and core loss is obtained for the parts according to the invention regardless of the particle size of the iron powder.

(Example 5)
Example 5 illustrates that it is possible to use clays containing different types of waterglass and different types of defined phyllosilicates. A 60% atomized iron-40% sendust powder mixture was used with various silicates (Na, K and Li) having an electrically neutral layer and clays (kaolin and talc) containing various phyllosilicates. Except for coating as above. In the comparative examples, clay containing phyllosilicate with charged layer, Veegum (registered trademark in any country) and mica were used. Veegum (registered trademark in any country) is a trade name for smectite group clay. The mica used was muscovite. In all tests, the second layer contained 1% clay and 0.4% by weight water glass. The heat treatment was performed at 700 ° C. for 0.5 hours under nitrogen.

Table 5 below shows the results of part testing.

  As can be seen from Table 5, various types of waterglass and clays containing phyllosilicates defined can be used as long as the phyllosilicate is of the type having an electrical neutral layer.

(Example 6)
Example 6 illustrates that by varying the amount of clay and alkali silicate in the second layer, the properties of the compressed and heat treated parts can be controlled and optimized. Samples were prepared and tested as described above. The heat treatment was performed at 700 ° C. for 0.5 hours under nitrogen.

Table 6 below shows the results of the test.

  As can be seen from Table 6, when the content of sodium silicate in the second layer exceeds 0.7% by weight, the resistivity decreases. The resistivity also decreases as the sodium silicate content decreases, so that the silicate content is between 0.2 and 0.7% by weight of the total 60% atomized iron-40% sendust powder mixture, preferably Should be between 0.3 and 0.6% by weight. As the clay content in the second layer further increases to a maximum of about 4%, the resistivity increases but the core loss decreases due to the increased coercivity. Therefore, the upper limit of the clay in the second layer is 5% by weight, preferably 4% by weight of the iron-based composite powder. If the clay content is too low, it will adversely affect the resistivity and core loss, so the lower limit of the clay content is 1%, preferably 3%.

(Example 7)
Example 7 below illustrates that the powder produced according to the present invention can be compressed to various compression pressures at various compression die temperatures. The following samples were processed as described above. 60% atomized iron and 40% sendust are coated with phosphorus and clay-sodium silicate, the content of kaolin in the second layer is 2% by weight of the composite iron-sendust powder and the content of sodium silicate is 0.4% %Met.

Samples ov) were compressed between 400 and 1200 MPa at a compression die temperature of either 20 ° C. or 60 ° C. and heat treated at 700 ° C. for 0.5 hours under nitrogen.
Results of tests according to Table 7;

  Table 7 shows that high resistivity and low core loss are obtained with parts according to the invention compressed to various compression pressures and compressed at various compression die temperatures. When the compression pressure is increased from 400 to 800 MPa and the compression pressure is further increased, an increase in density and a decrease in loss can be observed, but only a slight effect. The compression die temperature only slightly increases the resistivity and does not provide further improvement in magnetic properties.

(Example 8)
Example 8 below illustrates that parts made from powders according to the present invention can be heat treated at various atmospheres and at various temperatures. The following samples were processed as described above. Phosphorus- and clay-sodium silicate coatings of 60% atomized iron and 40% sendust, the kaolin content in the second layer is 2% by weight of the composite iron-sendust powder, and the sodium silicate content is 0. It was 4% by weight.

Samples w-Dd) were heat treated between 550-750 ° C. under nitrogen and air, respectively. Results of tests according to Table 8;

  Table 8 shows that high resistivity and low core loss can be obtained with parts according to the invention heat treated between 650 ° C. and 750 ° C. in a nitrogen atmosphere or in a mixed atmosphere containing nitrogen and air.

(Example 9)
Example 9 below illustrates that by adding gas atomized FeSi to the mixture, it is possible to enhance the magnetic properties of parts made from the powder according to the invention. The iron-sendust powder mixture has a first phosphorus coating layer and a second layer consisting of 2% kaolin and 0.4% sodium silicate. The powder mixture was compressed to 800 MPa and heat-treated at 700 ° C. for 30 minutes in a nitrogen atmosphere.

  As can be seen in Table 9, the addition of 10% FeSi to the phosphorus and kaolin-sodium silicate coated iron-sendust mixture increases resistivity and decreases coercivity and core loss.

(Example 10)
Water atomized pure iron powder having an iron content of more than 99.5% by weight was used as the core particles. The average particle size of the powder was about 45 μm. The core particles were mixed with Sendust (typically 85% Fe, 9% Si and 6% Al) and the powder mixture was treated with a phosphorus-containing solution according to WO2008 / 069749. The resulting dry phosphorus-coated iron powder-Sendust mixture is prepared as described in WO 2009/116938, ie first a basic aminoalkyl-alkoxysilane (Dynasylan (registered trademark in any country) Ameo, Evonik Inc). And then an oligomer of aminoalkyl / alkyl-alkoxysilane (Dynasylan (registered trademark in any country) 1146, manufactured by Evonik Inc.), each in various amounts, using a 1: 1 relationship. The powder was mixed and further treated with a second (metal organic) coating layer. The composition was further mixed with various amounts of fine powders of bismuth (III) oxide (> 99% by weight; D ₅₀ about 0.3 μm).

  After coating, the powder was mixed with 0.4% amide wax and compressed to 800 MPa in a ring with an inner diameter of 45 mm, an outer diameter of 55 mm and a height of 5 mm. Thereafter, the compressed part was subjected to a heat treatment step at 700 ° C. for 0.5 hour in a nitrogen atmosphere.

  Unless otherwise stated, all tests in the following examples were conducted in this manner.

Samples Hh to Ii) were prepared according to Table 10. Table 10 also shows the results of part testing.

  As can be seen from Table 10, the combination of atomized iron, sendust, first phosphorus coating layer, and second (metal organic) coating layer is significantly more resistant, DC, compared to using 100% atomized iron powder. Improve bias and reduce core loss and coercivity.

(Example 11)
By changing the sendust content of the atomized iron powder, it is possible to control the magnetic properties of the compressed and heat treated parts. The following samples were all treated in the same way-a first layer of phosphorus coating and a second (metal organic) coating layer. The difference between the samples is that the sendust content of atomized iron powder was changed. All samples were compressed to 800 MPa and heat-treated at 700 ° C. for 0.5 hours in a nitrogen atmosphere. Table 11 also shows the results of part testing.

For clay / sodium silicate-coated atomized iron- and Sendust-powder-mixtures, increasing Sendust occupancy significantly improves resistivity and DC bias, thus reducing core loss and coercivity.

Claims (15)

A composite iron-based powder composition comprising core particles, wherein the core particles consist essentially of (a) 7 wt% to 13 wt% silicon, 4 wt% to 7 wt% aluminum, and the balance iron. The composite iron-based powder composition as described above, wherein the core particle is coated with a first phosphorus-containing layer. The atomized iron particles are (a) an alkali silicate combined with a clay mineral containing phyllosilicate, and the combined silicon-oxygen tetrahedral layer and its hydroxide octahedral layer are electrically neutral. 2. The composite iron-based powder according to claim 1, which has a second layer containing an alkali silicate or (b) a metal organic layer. The iron alloy particles are (a) an alkali silicate combined with a clay mineral containing phyllosilicate, and the combined silicon-oxygen tetrahedral layer and its hydroxide octahedral layer are electrically neutral. 3. The composite iron-based powder according to claim 2, which has a second layer including an acid alkali or (b) a metal organic layer.   The composite iron-based powder according to claim 3, wherein the iron alloy particles and the atomized iron particles have the same second layer.   The composite iron-based powder composition according to any one of claims 2 to 4, wherein the second layer contains kaolin and sodium silicate.   The composite iron-based powder composition according to any one of claims 1 to 5, further comprising atomized FeSi.   The composite iron-based powder composition according to any one of claims 1 to 6, wherein the phosphorus-containing layer has a thickness of 20 to 300 nm.   The composite iron group according to any one of claims 1 to 7, wherein the phosphorus coating is provided by removing the solvent by contacting the core particles with a phosphorus compound in a solvent and then drying. Powder.   The composite iron-based powder according to any one of claims 1 to 8, wherein the phosphorus compound is phosphoric acid or ammonium phosphate.   The content of alkali silicate is 0.1 to 0.9% by weight of the composite iron-based powder, preferably 0.2 to 0.8% by weight, according to any one of claims 2 to 9. Composite iron-based powder.   The composite iron-based powder according to any one of claims 2 to 10, wherein the content of clay is 0.2 to 5% by weight, preferably 0.5 to 4% by weight of the composite iron-based powder. a) preparing the composite iron-based powder according to any one of claims 1 to 11;
b) compressing the composite iron-based powder, optionally mixed with a lubricant, in a die at a compression pressure of 400 to 1200 MPa in a uniaxial press motion;
c) extracting the compressed part from the die;
d) heat treating the extracted part in a non-reducing atmosphere at a temperature up to 800 ° C. to produce a compressed and heat-treated part.   A part manufactured by the method according to claim 12.   The component of claim 13, wherein the component is an inductor core.   Resistivity greater than 1000 μΩm, preferably greater than 2000 μΩm, most preferably greater than 3000 μΩm, ρ; saturation flux greater than 1.1 (T), preferably greater than 1.2 (T), most preferably greater than 1.3 (T) Density Bs; core loss of less than 12 W / kg at a frequency of 20 kHz, induction at 0.05 T; coercivity of less than 210 A / m, preferably less than 200 A / m, most preferably less than 190 A / m; and 50 at 4000 A / m The inductor core of claim 14, wherein the inductor core has a DC bias of at least%.