EP2053138A1 - Composite material made from metal powder, starting material and process of preparation - Google Patents

Composite material made from metal powder, starting material and process of preparation Download PDF

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Publication number
EP2053138A1
EP2053138A1 EP09100109A EP09100109A EP2053138A1 EP 2053138 A1 EP2053138 A1 EP 2053138A1 EP 09100109 A EP09100109 A EP 09100109A EP 09100109 A EP09100109 A EP 09100109A EP 2053138 A1 EP2053138 A1 EP 2053138A1
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EP
European Patent Office
Prior art keywords
metal
material according
powder
starting material
release agent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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EP09100109A
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German (de)
French (fr)
Inventor
Hans-Peter Koch
Andreas Harzer
Wilfried Aichele
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Robert Bosch GmbH
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Robert Bosch GmbH
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Publication of EP2053138A1 publication Critical patent/EP2053138A1/en
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0207—Using a mixture of prealloyed powders or a master alloy
    • C22C33/0228—Using a mixture of prealloyed powders or a master alloy comprising other non-metallic compounds or more than 5% of graphite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/16—Metallic particles coated with a non-metal
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
    • H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
    • H01F1/22—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
    • H01F1/24—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
    • Y10T428/2991—Coated
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
    • Y10T428/2991—Coated
    • Y10T428/2993—Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]

Definitions

  • the invention relates to a metal powder composite material with high electrical resistivity and a starting material and a method for producing such a composite material.
  • Metal powder composite materials with high electrical resistivity find technical application, for example as high-resistance steels and as soft magnetic components in high-speed solenoid valves.
  • special metal powder-plastic composites have been developed. They are produced by techniques of powder metallurgy by pressing metal powder particles which are coated with electrically insulating plastic. The pressed metal powder particles are glued together over the plastic.
  • These metal powder-plastic composites have a very high electrical resistance compared to pure iron. However, they show reductions in strength, permeability, magnetic saturation and temperature and fuel resistance over the classic sintered materials.
  • the metal powders are mixed with small amounts of release agent or lubricant before being pressed. This addition results in a higher density of the molded articles because it promotes slippage of the metal powder particles during compaction, reduces mold release forces, and increases the life of the press tool by lubricating the ram and die.
  • the release agents or lubricants are usually added in amounts between 0.1 and 1.5 wt .-% of the metal powders.
  • the shaping by axial pressing is usually followed by a heat treatment.
  • the added processing agents pyrolyze at temperatures between 150 and 500 ° C far below the sintering temperature of the metal powder (sintering temperature of iron 1120 ° C to 1280 ° C).
  • metal soaps in the powder dressing leave metal oxides.
  • the sintered, axially pressed soft magnetic metal powder would have a substantially (about a factor of 100) higher electrical resistance in order to achieve a good switching dynamics.
  • oxides in composites consisting mainly of metal powder have some of the negative effects on properties such as mechanical and possibly magnetic properties, the inventors have found that multiple oxides which form at least one common phase give composites very good mechanical, thermal and chemical resistance convey.
  • the starting material according to the invention for the production of a metal powder composite material having a high electrical resistivity can be composed without problems in such a way that the composite material produced therefrom not only has a high resistance but also a satisfactory compression density. If the amount of release agent required for a high resistance in the composite material is too large to simultaneously obtain an optimum compression density, oxidic fine powder may be added to the at least one release agent in at least one of the at least one release agent can form a common phase. You do not have to accept any deterioration in the properties of the composite material.
  • the process according to the invention is therefore particularly advantageous because the oxides formed by pyrolysis of the release agents used in powder metallurgy can be used to produce the common phase.
  • the inventive high-resistance composite materials can be used in the embodiment as soft magnetic composites also due to their high magnetic saturation and high permeability, especially for solenoid valves with good switching dynamics.
  • the metal powder consists essentially of iron materials, such as those of iron, iron silicon, iron cobalt and iron nickel or mixtures of the materials mentioned, with iron being particularly preferred. "consisting essentially of " in this context means that other substances can only be present in amounts such that the soft magnetic properties do not deteriorate appreciably.
  • the glass serves as the at least one common phase, such as silicate or boron-containing glass, or a defined compound from the group of mixed oxides with spinel structure, the metal phosphates and the metal silicates.
  • At least one metal soap and / or at least one material from the group of mono-, di- or triesters of phosphoric acid, boric acid and silicic acid with long-chain alcohols and / or polydimethyldisiloxane is (are) contained in the starting material as release agent.
  • At least one metal oxide and / or silicic acid is preferably used as the fine powder.
  • the particle diameter (primary particle diameter) of the fine powder is ⁇ about 100 nm.
  • a satisfactory compression density in the molded body combined with a sufficiently high electrical resistance in the metal powder composite material can be achieved in an advantageous manner when based on the weight of the metal powder, the proportion of release agent is between about 0.1 and about 1.5 wt .-% or the sum of the proportions of release agent and fine powder between about 0.2 and about 3 wt .-%.
  • the ratio of the added amounts of release agent or fine powder, optionally taking into account the amounts of mitreagierendem metal from the metal powder surfaces, with respect to the at least one to be formed in the reaction of the oxides defined compound is approximately stoichiometric.
  • the soft magnetic composite materials with high specific resistance consist of pressed powdered metal powder, which are provided with a coating mainly of defined chemical compounds which adhere well to the bare or surface-modified, for example phosphated metal particles and depending on the application in addition a high electrical resistance, temperature and Provide fuel resistance and / or protect the metal from corrosion.
  • the coating prevents electrical connection between the metal particles.
  • the defined chemical compounds are derived from mixed oxides with spinel structure, such as mixed oxides from the group Al2MgO4 (spinel), Al2ZnO4 (zinc spinel), Al2MnO4 (manganese spinel), Al2FeO4 (iron spinel), Fe2MgO4 (magnoferrite), Fe304 (magnetite), Fe2Zn04 (Franklinite), Fe2MnO4 (Jakobsite), Fe2Ni04 (Trevirite), Cr2Fe04 (Chromite) and Cr2MgO4 (Magnochromite), metal phosphates such as zinc and iron phosphate, silicate glasses, boron-containing glasses and metal silicates such as CoSiO3.
  • mixed oxides from the group Al2MgO4 (spinel), Al2ZnO4 (zinc spinel), Al2MnO4 (manganese spinel), Al2FeO4 (iron spinel), Fe2Mg
  • novel soft magnetic composites thus contain no thermosets or thermosets as insulation and binder as the metal-plastic composites. Nevertheless, in comparison to these, they also have a high electrical resistivity, comparable or better mechanical strength, better temperature and fuel resistance, comparable magnetic saturation and comparable permeability.
  • the soft magnetic composite materials according to the invention are therefore suitable for use in fast-switching magnetic valves, in particular those used in automotive engineering.
  • metal powders are mixed with combinations of novel or known release agents or lubricants or coated with these combinations (see above).
  • the release agents are also used in the invention to provide a composite material to generate a high electrical resistance.
  • the optimum proportion of release agent based on the amount of metal powder is ⁇ about 1% by weight. Release agent levels of> about 2% by weight are therefore generally not useful.
  • the release agents oxide fine powder primary particle diameter preferably ⁇ about 100 nm
  • Separating agents react, instead of increasing the proportion of release agent significantly above the optimum in terms of press density.
  • the amount ratio of the release agent or the release agent and fine powder depends on the composition of the desired by the reaction of the pyrolysis and optionally the fine powder common phase. If these are mixed oxides with spinel structure, metal phosphates or metal silicates, the release agent or the release agent / fine powder combinations should be composed so that a stoichiometric conversion takes place in said compounds.
  • the components of the defined compounds may also originate from the surface of the metal powder.
  • the correct composition of the release agent or release agent / fine powder combination must be determined by simple tests. If a common phase in the form of glasses forms in the reaction instead of defined compounds, then larger tolerances can be permitted in the composition of the release agent or release agent / fine powder combinations.
  • Examples of the said release agents are metal soaps, such as the stearates of calcium, magnesium, aluminum, zinc, cobalt, iron, nickel, copper, molybdenum and manganese, or esters of higher alcohols of phosphoric, boronic or silicic acid.
  • Examples of the fine powders mentioned are oxides such as Fe 2 O 3 and silicic acid.
  • the mixture of metal powder, release agent and optionally Fine powder is pressed axially into shaped bodies. Subsequently, the moldings are heated in a non-reducing atmosphere, for example in a nitrogen or argon atmosphere, to a temperature which is well below the sintering temperature of the metal powder, ie preferably below about 800 ° C. and more preferably between about 150 and about 550 ° C., so that the release agents pyrolyze. Below about 150 ° C., at most incomplete pyrolysis and the reactions proceed very slowly. At temperatures below 550 ° C., it is impossible for the metal particles to sinter together and thereby form electrical current paths. The pyrolysis residues react at the temperatures used either together and / or with the added fine powders and optionally with the surface of the metal particles to said defined chemical compounds.
  • a non-reducing atmosphere for example in a nitrogen or argon atmosphere
  • a mixture of iron powder and zinc stearate and a mono-, di-triester of phosphoric acid with long-chain alcohols, such as a mixture of phosphoric acid monostearyl ester and phosphoric acid distearyl ester having a melting point of 70 ° C, as a release agent was pressed into a molded article, wherein the proportion of the release agent based on the weight of the iron powder was about 1.7% by weight and the atomic ratio Zn: P was about 3: 2.
  • the shaped body was heated in a non-reducing atmosphere, for example in nitrogen, to a maximum temperature of about 550 ° C., whereby the separating agents pyrolyzed to ZnO or P 2 O 5 and the resulting oxides reacted with one another to give zinc phosphate.
  • zinc phosphate has a high electrical resistivity, adheres well to metals and specifically protects iron from corrosion.
  • the resulting composite material was suitable as a soft magnetic material for high-speed electrical valves.
  • a mixture of iron powder and cobalt stearate and reactive group-modified polydimethylsiloxane as a release agent was pressed into a molded article, wherein the proportion of the release agent based on the weight of the iron powder was about 1.6 wt .-% and the atomic ratio Co: Si was about 1 ,
  • the molding was further treated as described in Example 1.
  • the resulting from the release agents pyrolysis CoO and SiO 2 thereby reacted to form CoSiO3.
  • the cobalt silicate had good adhesion to the iron powder, was well electrically insulating and well protected against corrosion.
  • a mixture of iron powder, cobalt stearate as a release agent, to which a stoichiometric amount of fumed silica (primary particle diameter ⁇ about 100 nm) was added was pressed into a molded article, wherein the proportion of the release agent based on the weight of the iron powder at about 1.3 wt .-% was.
  • the molding was further treated as described in Example 1. The resulting from the release agent pyrolysis CoO reacted with the SiO 2 of the silica to CoSiO3.
  • a mixture of iron powder and as a release agent zinc stearate and iron stearate was pressed into a molded article, wherein the proportion of the release agent based on the weight of the iron powder was about 1.4 wt .-% and the atomic ratio Zn: Fe was about 1: 2.
  • the molding was further treated as described in Example 1.
  • the resulting from the release agents pyrolysis ZnO and Fe203 reacted with each other to the spinel Fe2Zn04 (Franklinite).
  • Spinels have - as stated - a good adhesion to iron powder, they are electrically good insulating and they protect iron excellent against corrosion.
  • the molding was further treated as described in Example 1.
  • the pyrolysis product ZnO formed from the release agent reacted with the Fe 2 O 3 to form the spinel Fe 2 ZnO 4.
  • the molding was further treated as described in Example 1.
  • the resulting pyrolysis products NiO and Fe2O3 reacted with each other to form the spinel Fe2Ni04.

Abstract

The composite includes two or more oxides encasing the metal powder particles. The oxides form one or more common phase(s). The composite has a high magnetic susceptibility, i.e. is a soft-magnetic material. The powder comprises essentially a ferrous metal. The common phase is a glass such as a silica- or borate glass. It is alternatively a defined compound selected from: mixed oxides with spinel structure, metal phosphates and metal silicates. The mixed oxide is selected from spinel, zinc spinel, manganese spinel, iron spinel, magnoferrite, magnetite, franklinite, jakobsite, trevirite, chromite and magnochromite. Zinc- and iron phosphates are used as metal phosphates. CoSiO 3is used as a metal silicate. The starting material (also claimed) contains metal powder and separating materials with oxidic pyrolysis residues and oxidic fine powder. The separating material comprises one or more metal soaps and/or at least one of: mono-, di-, or tri-esters of phosphoric acid, of boric acid or of silicic acid with long chain alcohols and/or, if appropriate, with polydimethyl-di-siloxanes modified with reactive groups. At least one metal soap is a stearate. The metal ion in the soap is Ca, Mg, Al, Zn, Co, Fe, Ni, Cu, Mo, or Mn. The metal powder is formed from at least one metal oxide and/or silicic acid. The metal oxide is selected from Fe 2O 3, NiO, ZnO, CoO, MnO, MgO, Cr 2O 3, CuO and MoO 2. The particle diameter of the fine powder is up to about 1 mu m and no greater than 100 mu m. The proportion of separation agent, based on the weight of metal powder, is 0.1-2 wt%, or the sum of the fractions of separation agent and fine powder is 0.2-3 wt%. Further proportions are specified.

Description

Stand der TechnikState of the art

Die Erfindung betrifft einen Metallpulver-Verbundwerkstoff mit hohem spezifischem elektrischem Widerstand und ein Ausgangsmaterial und ein Verfahren zur Herstellung eines solchen Verbundwerkstoffs.The invention relates to a metal powder composite material with high electrical resistivity and a starting material and a method for producing such a composite material.

Metallpulver-Verbundwerkstoffe mit hohem spezifischem elektrischem Widerstand finden technische Anwendung beispielsweise als hochohmige Stähle und als weichmagnetische Komponenten in schnellschaltenden Magnetventilen. Für die letztere Anwendung sind spezielle Metallpulver-Kunststoffverbunde entwickelt worden. Sie werden mit Techniken der Pulvermetallurgie durch Verpressen von Metallpulverteilchen erzeugt, welche mit elektrisch isolierendem Kunststoff beschichtet sind. Die verpressten Metallpulverteilchen sind über den Kunststoff miteinander verklebt. Diese Metallpulver-Kunststoffverbunde haben im Vergleich zu Reineisen einen sehr hohen elektrischen Widerstand. Jedoch ist es so, dass sie gegenüber den klassischen Sinterwerkstoffen Abminderungen bezüglich Festigkeit, Permeabilität, magnetischer Sättigung und Temperatur- und Kraftstoffbeständigkeit zeigen.Metal powder composite materials with high electrical resistivity find technical application, for example as high-resistance steels and as soft magnetic components in high-speed solenoid valves. For the latter application special metal powder-plastic composites have been developed. They are produced by techniques of powder metallurgy by pressing metal powder particles which are coated with electrically insulating plastic. The pressed metal powder particles are glued together over the plastic. These metal powder-plastic composites have a very high electrical resistance compared to pure iron. However, they show reductions in strength, permeability, magnetic saturation and temperature and fuel resistance over the classic sintered materials.

In der Pulvermetallurgie (PM) werden die Metallpulver vor dem Verpressen mit kleinen Anteilen an Trenn- bzw. Gleitmitteln versetzt. Dieser Zusatz bewirkt eine höhere Dichte der Formkörper, da er ein Aneinandergleiten der Metallpulverteilchen während der Verdichtung fördert, er verringert die Entformungskräfte, und er erhöht die Lebensdauer des Presswerkzeugs durch Schmierung von Pressstempel und Gesenk.In powder metallurgy (PM), the metal powders are mixed with small amounts of release agent or lubricant before being pressed. This addition results in a higher density of the molded articles because it promotes slippage of the metal powder particles during compaction, reduces mold release forces, and increases the life of the press tool by lubricating the ram and die.

Die Trenn- bzw. Gleitmittel werden üblicherweise in Mengen zwischen 0,1 und 1,5 Gew.-% den Metallpulvern zugesetzt. Neben dem reinen Mischen von feinpulverisierten Trennmitteln mit den Metallpulvern ist es auch möglich, die Metallpulverteilchen mit Trennmitteln zu überziehen. Dies kann mit einer Lösung der Trennmittel in einem geeigneten Lösungsmittel erfolgen, wie es beispielsweise in der EP 0 673 284 B1 beschrieben ist, oder indem die Metallpartikel mit der Schmelze der Trennmittel benetzt werden. An die Formgebung durch axiales Pressen schliesst sich üblicherweise eine Wärmebehandlung an. Dabei pyrolysieren die zugesetzten Verarbeitungsmittel bei Temperaturen zwischen 150 und 500 DEG C weit unterhalb der Sintertemperatur der Metallpulver (Sintertemperatur von Eisen 1120 DEG C bis 1280 DEG C).The release agents or lubricants are usually added in amounts between 0.1 and 1.5 wt .-% of the metal powders. In addition to the pure mixing of finely pulverized release agents with the metal powders, it is also possible to coat the metal powder particles with release agents. This can be done with a solution of the release agent in a suitable solvent, as for example in the EP 0 673 284 B1 described or by the metal particles are wetted with the melt of the release agent. The shaping by axial pressing is usually followed by a heat treatment. The added processing agents pyrolyze at temperatures between 150 and 500 ° C far below the sintering temperature of the metal powder (sintering temperature of iron 1120 ° C to 1280 ° C).

Während Trennmittel auf rein organischer Basis, wie Wachse und Fettsäuren, unter Schutzgas weitgehend rückstandsfrei pyrolysieren, hinterlassen beispielsweise Metallseifen im Pulververband Metalloxide. Diese, wie beispielsweise ZnO, schwächen das Gefüge, sofern sie sich nicht, wie beispielsweise Eisen-, Cobalt-, Nickel-, Kupfer-, Molybdän- oder Manganoxide beim anschliessenden Sinterprozess in reduzierender Atmosphäre zu den Metallen reduzieren lassen. So beschreibt die EP 0 673 284 B1 wie durch Kombination verschiedenen Metallseifen als Trennmittel durch Reduktion der bei der Pyrolyse erzeugten Oxide in einer Wasserstoffatmosphäre und durch Sintern gezielt metallische Legierungen untereinander oder mit den verpressten Metallpulvern erzeugt werden.While release agents on a purely organic basis, such as waxes and fatty acids, pyrolysis largely residue-free under protective gas, for example, metal soaps in the powder dressing leave metal oxides. These, such as ZnO, weaken the microstructure, unless they can be reduced to the metals in a subsequent sintering process in a reducing atmosphere, such as, for example, iron, cobalt, nickel, copper, molybdenum or manganese oxides. That's how it describes EP 0 673 284 B1 as by combination of different metal soaps as release agents by reduction of the oxides produced in the pyrolysis in a hydrogen atmosphere and by sintering targeted metallic alloys with each other or with the pressed metal powders are generated.

Auf diese Weise lassen sich auch weichmagnetische Verbundwerkstoffe für Magnetventile-herstellen. Jedoch müssten die gesinterten, axial verpressten weichmagnetischen Metallpulver einen wesentlich (etwa um den Faktor 100) höheren elektrischen Widerstand aufweisen, um eine gute Schaltdynamik zu erzielen.In this way, soft magnetic composites for solenoid valves can be produced. However, the sintered, axially pressed soft magnetic metal powder would have a substantially (about a factor of 100) higher electrical resistance in order to achieve a good switching dynamics.

Die Erfindung und ihre VorteileThe invention and its advantages

Es ist die Aufgabe der Erfindung, einen Metallpulver-Verbundwerkstoff mit hohem spezifischem elektrischem Widerstand mit guter mechanischer Festigkeit, sehr guter Temperatur- und Kraftstoffbeständigkeit und ein Ausgangsmaterial und ein Verfahren für die rationelle Herstellung eines solchen Verbundwerkstoffs anzugeben.It is the object of the invention, a metal powder composite material with high electrical resistivity with good mechanical strength, very good temperature and fuel resistance and a starting material and a method for the rational production of such a composite material.

Diese Aufgabe wird mit einem Metallpulver-Verbundwerkstoff der eingangs genannten Art mit den Merkmalen des kennzeichnenden Teils des Anspruchs 1, mit einem Ausgangsmaterial der eingangs genannten Art mit den Merkmalen des kennzeichnenden Teils des Anspruchs 9 und mit einem Verfahren der eingangs genannten Art mit den Merkmalen des kennzeichnenden Teils des Anspruchs 20 gelöst.This object is achieved with a metal powder composite material of the type mentioned above with the features of the characterizing part of claim 1, with a starting material of the type mentioned above with the features of the characterizing part of claim 9 and with a method of the type mentioned above with the features of characterizing part of claim 20 solved.

Während Oxide in hauptsächlich aus Metallpulver bestehenden Verbundwerkstoffen zum Teil die Eigenschaften, wie mechanische und gegebenenfalls magnetische Eigenschaften, negativ beeinflussen, haben die Erfinder festgestellt, dass mehrere Oxide, welche mindestens eine gemeinsame Phase bilden, den Verbundwerkstoffen eine sehr gute mechanische, thermische und chemische Beständigkeit vermitteln.While oxides in composites consisting mainly of metal powder have some of the negative effects on properties such as mechanical and possibly magnetic properties, the inventors have found that multiple oxides which form at least one common phase give composites very good mechanical, thermal and chemical resistance convey.

Das erfindungsgemässe Ausgangsmaterial für die Herstellung eines Metallpulver-Verbundwerkstoffs mit hohem spezifischem elektrischem Widerstand lässt sich problemlos so zusammensetzen, dass der daraus hergestellte Verbundwerkstoff neben dem hohen Widerstand auch eine zufriedenstellende Pressdichte aufweist. Sofern die für einen hohen Widerstand im Verbundwerkstoff erforderliche Trennmittelmenge zu gross ist, um gleichzeitig eine optimale Pressdichte zu erhalten, kann in solchen Fällen dem mindestens einen Trennmittel oxidisches Feinpulver zugesetzt werden, das bei der Weiterverarbeitung mit dem aus dem mindestens einen Trennmittel entstandenen Pyrolyseprodukt mindestens eine gemeinsame Phase zu bilden vermag. Dabei muss man keine Verschlechterung der Eigenschaften des Verbundwerkstoffs in Kauf nehmen.The starting material according to the invention for the production of a metal powder composite material having a high electrical resistivity can be composed without problems in such a way that the composite material produced therefrom not only has a high resistance but also a satisfactory compression density. If the amount of release agent required for a high resistance in the composite material is too large to simultaneously obtain an optimum compression density, oxidic fine powder may be added to the at least one release agent in at least one of the at least one release agent can form a common phase. You do not have to accept any deterioration in the properties of the composite material.

Das erfindungsgemässe Verfahren ist deshalb besonders vorteilhaft, weil sich die durch Pyrolyse der in der Pulvermetallurgie eingesetzten Trennmittel entstehenden Oxide zur Erzeugung der gemeinsamen Phase einsetzen lassen.The process according to the invention is therefore particularly advantageous because the oxides formed by pyrolysis of the release agents used in powder metallurgy can be used to produce the common phase.

In vorteilhafter Weise lassen sich die erfindungsgemässen hochohmigen Verbundwerkstoffe in der Ausgestaltung als weichmagnetische Verbundwerkstoffe auch aufgrund ihrer hohen magnetischen Sättigung und hohen Permeabilität insbesondere für Magnetventile mit guter Schaltdynamik einsetzen. Dabei ist es besonders günstig, wenn das Metallpulver im wesentlichen aus Eisenwerkstoffen, beispielsweise solchen aus Eisen, Eisensilicium, Eisencobalt und Eisennickel oder Mischungen der genannten Materialien besteht, wobei Eisen besonders bevorzugt ist. "im wesentlichen aus ... besteht" bedeutet in diesem Zusammenhang, dass weitere Stoffe nur in solchen Mengen vorhanden sein können, dass sich die weichmagnetischen Eigenschaften nicht beachtlich verschlechtern.Advantageously, the inventive high-resistance composite materials can be used in the embodiment as soft magnetic composites also due to their high magnetic saturation and high permeability, especially for solenoid valves with good switching dynamics. It is particularly advantageous if the metal powder consists essentially of iron materials, such as those of iron, iron silicon, iron cobalt and iron nickel or mixtures of the materials mentioned, with iron being particularly preferred. "consisting essentially of ..." in this context means that other substances can only be present in amounts such that the soft magnetic properties do not deteriorate appreciably.

Es ist vorteilhaft, wenn als die mindestens eine gemeinsame Phase ein Glas, wie silikatisches oder borhaltiges Glas, oder eine definierte Verbindung aus der Gruppe der Mischoxide mit Spinellstruktur, der Metallphosphate und der Metallsilikate dient.It is advantageous if the glass serves as the at least one common phase, such as silicate or boron-containing glass, or a defined compound from the group of mixed oxides with spinel structure, the metal phosphates and the metal silicates.

Es ist günstig, wenn als Trennmittel mindestens eine Metallseife und/oder mindestens ein Material aus der Gruppe Mono-, Di- oder Triester der Phosphorsäure, der Borsäure und der Kieselsäure mit langkettigen Alkoholen und/oder Polydimethyldisiloxan in dem Ausgangsmaterial enthalten ist (sind).It is advantageous if at least one metal soap and / or at least one material from the group of mono-, di- or triesters of phosphoric acid, boric acid and silicic acid with long-chain alcohols and / or polydimethyldisiloxane is (are) contained in the starting material as release agent.

Bei der Kombination eines Trennmittels mit oxidischem Feinpulver in dem erfindungsgemässen Ausgangsmaterial wird als Feinpulver bevorzugt mindestens ein Metalloxid und/oder Kieselsäure eingesetzt.In the combination of a release agent with oxidic fine powder in the starting material according to the invention, at least one metal oxide and / or silicic acid is preferably used as the fine powder.

Um eine hohe Reaktionsfähigkeit der Feinpulver mit den Pyrolyserückständen der Trennmittel zu gewährleisten, ist es besonders vorteilhaft, wenn der Teilchendurchmesser (Primärkorndurchmesser) des Feinpulvers ≤ etwa 100 nm ist.In order to ensure a high reactivity of the fine powders with the pyrolysis residues of the release agents, it is particularly advantageous if the particle diameter (primary particle diameter) of the fine powder is ≦ about 100 nm.

Eine zufriedenstellende Pressdichte im Formkörper kombiniert mit einem ausreichend hohen elektrischen Widerstand im Metallpulver-Verbundmaterial lässt sich in vorteilhafter Weise erreichen, wenn
bezogen auf das Gewicht des Metallpulvers der Anteil der Trennmittel zwischen etwa 0,1 und etwa 1,5 Gew.-% oder die Summe aus den Anteilen an Trennmittel und Feinpulver zwischen etwa 0,2 und etwa 3 Gew.-% liegt.A satisfactory compression density in the molded body combined with a sufficiently high electrical resistance in the metal powder composite material can be achieved in an advantageous manner when
based on the weight of the metal powder, the proportion of release agent is between about 0.1 and about 1.5 wt .-% or the sum of the proportions of release agent and fine powder between about 0.2 and about 3 wt .-%.

Es ist vorteilhaft, wenn das Verhältnis der zugefügten Mengen an Trennmittel bzw. an Trennmittel und Feinpulver, gegebenenfalls unter Berücksichtigung der Mengen an mitreagierendem Metall von den Metallpulveroberflächen, im Hinblick auf die mindestens eine bei der Reaktion der Oxide zu bildende definierte Verbindung angenähert stöchiometrisch ist.It is advantageous if the ratio of the added amounts of release agent or fine powder, optionally taking into account the amounts of mitreagierendem metal from the metal powder surfaces, with respect to the at least one to be formed in the reaction of the oxides defined compound is approximately stoichiometric.

Es ist vorteilhaft, wenn beim Pyrolysieren und Reagieren auf eine Temperatur deutlich unterhalb der Sintertemperatur des Metallpulvers und besonders bevorzugt - sofern das Metall Eisen ist - auf eine Temperatur zwischen etwa 150 und etwa 550 DEG C erhitzt wird. Bei Temperaturen oberhalb etwa 550 DEG C können Strompfade zwischen den Metallteilchen entstehen, und bei Temperaturen unter etwa 150 DEG C ist die Pyrolyse unvollständig und dauert für ein industrielles Verfahren zu lange.It is advantageous when, when pyrolyzing and reacting to a temperature well below the sintering temperature of the metal powder and more preferably - if the metal is iron - is heated to a temperature between about 150 and about 550 ° C. At temperatures above about 550 ° C., current paths may form between the metal particles, and at temperatures below about 150 ° C., pyrolysis is incomplete and takes too long for an industrial process.

Es ist vorteilhaft, wenn in einer nicht reduzierenden Atmosphäre erhitzt wird, und besonders vorteilhaft, wenn dabei die Atmosphäre auf den Pyrolyseprozess abgestimmt wird.It is advantageous to heat in a non-reducing atmosphere, and particularly advantageous if the atmosphere is tuned to the pyrolysis process.

Weitere vorteilhafte Ausgestaltungen des erfindungsgemässen Metallpulver-Verbundmaterials, des erfindungsgemässen Ausgangsmaterials und des erfindungsgemässen Verfahrens sind in den Unteransprüchen aufgeführt.Further advantageous embodiments of the inventive metal powder composite material, the inventive starting material and the inventive method are listed in the dependent claims.

Im folgenden wird die Erfindung anhand von weichmagnetischen Verbundwerkstoffen und von Ausgangsmaterialien und von Verfahren zu ihrer Herstellung detailliert beschrieben. Es sei aber klargestellt, dass sich zwar die Erfindung anhand dieser Beispiele besonders anschaulich erläutern lässt, dass aber die Erfindung nicht auf diese Beispiele beschränkt ist, und von ihnen im Rahmen der Ansprüche mannigfaltige Abweichungen möglich sind.In the following, the invention will be described in detail with reference to soft magnetic composites and starting materials and to methods of making them. It should be understood, however, that while the invention may be particularly clearly illustrated with reference to these examples, the invention is not limited to these examples, and various variations are possible within the scope of the claims.

Die weichmagnetischen Verbundwerkstoffe mit hohem spezifischem elsktrischen Widerstand bestehen aus verpressten Metallpulverteilchen, die mit einem Überzug hauptsächlich aus definierten chemischen Verbindungen versehen sind, welche an den blanken oder oberflächenmodifizierten, beispielsweise phosphatierten Metallteilchen gut haften und je nach Anwendungsfall zusätzlich einen hohen elektrischen Widerstand, Temperatur- und Kraftstoffbeständigkeit vermitteln und/oder das Metall vor Korrosion schützen. Der Überzug verhindert eine elektrische Verbindung zwischen den Metallteilchen. Die definierten chemischen Verbindungen werden von Mischoxiden mit Spinellstruktur, wie Mischoxide aus der Gruppe Al2MgO4 (Spinell), Al2ZnO4 (Zinkspinell), Al2MnO4 (Manganspinell), Al2FeO4 (Eisenspinell), Fe2MgO4 (Magnoferrit), Fe304 (Magnetit), Fe2Zn04 (Franklinit), Fe2MnO4 (Jakobsit), Fe2Ni04 (Trevirit), Cr2Fe04 (Chromit) und Cr2MgO4 (Magnochromit), Metallphosphaten, wie Zink- und Eisenphosphat, silikatischen Gläsern, borhaltigen Gläsern und Metallsilikaten, wie CoSiO3, gebildet.The soft magnetic composite materials with high specific resistance consist of pressed powdered metal powder, which are provided with a coating mainly of defined chemical compounds which adhere well to the bare or surface-modified, for example phosphated metal particles and depending on the application in addition a high electrical resistance, temperature and Provide fuel resistance and / or protect the metal from corrosion. The coating prevents electrical connection between the metal particles. The defined chemical compounds are derived from mixed oxides with spinel structure, such as mixed oxides from the group Al2MgO4 (spinel), Al2ZnO4 (zinc spinel), Al2MnO4 (manganese spinel), Al2FeO4 (iron spinel), Fe2MgO4 (magnoferrite), Fe304 (magnetite), Fe2Zn04 (Franklinite), Fe2MnO4 (Jakobsite), Fe2Ni04 (Trevirite), Cr2Fe04 (Chromite) and Cr2MgO4 (Magnochromite), metal phosphates such as zinc and iron phosphate, silicate glasses, boron-containing glasses and metal silicates such as CoSiO3.

Die erfindungsgemässen weichmagnetischen Verbundwerkstoffe enthalten also keine Thermo- oder Duroplaste als Isolations- und Bindemittel wie die Metall-Kunststoffverbunde. Trotzdem haben sie im Vergleich zu diesen auch einen hohen spezifischen elektrischen Widerstand, eine vergleichbare oder bessere mechanische Festigkeit, eine bessere Temperatur- und Kraftstoffbeständigkeit, eine vergleichbare magnetische Sättigung und eine vergleichbare Permeabilität.The novel soft magnetic composites thus contain no thermosets or thermosets as insulation and binder as the metal-plastic composites. Nevertheless, in comparison to these, they also have a high electrical resistivity, comparable or better mechanical strength, better temperature and fuel resistance, comparable magnetic saturation and comparable permeability.

Die erfindungsgemässen weichmagnetischen Verbundwerkstoffe sind deshalb geeignet für den Einsatz in schnell schaltenden Magnetventilen insbesondere von solchen, die in der Kraftfahrzeugtechnik eingesetzt werden.The soft magnetic composite materials according to the invention are therefore suitable for use in fast-switching magnetic valves, in particular those used in automotive engineering.

Zur Herstellung der erfindungsgemässen weichmagnetischen Verbundwerkstoffe werden Metallpulver mit Kombinationen aus neuen oder bekannten Trenn- bzw. Gleitmitteln gemischt oder mit diesen Kombinationen beschichtet (s.o.). Wie erläutert werden die Trennmittel bei der Erfindung auch gebraucht, um einen Verbundwerkstoff mit
einem hohen elektrischen Widerstand zu erzeugen. Es ist aber so, dass ein zu hoher Trennmittelanteil die Pressdichte im Formkörper wieder vermindert. Hinsichtlich der Pressdichte liegt der optimale Trennmittelanteil bezogen auf die Metallpulvermenge bei < etwa 1 Gew.-%. Trennmittelanteile von > etwa 2 Gew.- % sind deshalb im allgemeinen nicht brauchbar. In den Fällen, in denen der optimale Trennmittelanteil nicht ausreicht, um den gewünschten hohen elektrischen Widerstand zu erzeugen, ist es deshalb günstiger, in den Trennmitteln oxidische Feinpulver (Primärkorndurchmesser bevorzugt ≤ etwa 100 nm) zu dispergieren, die mit den Pyrolyserückständen (s.u.) der Trennmittel reagieren, statt den Trennmittelanteil wesentlich über das Optimum hinsichtlich der Pressdichte zu erhöhen. Das Mengenverhältnis der Trennmittel bzw. der Trennmittel und Feinpulver richtet sich nach der Zusammensetzung der durch die Reaktion der Pyrolyseprodukte und gegebenenfalls der Feinpulver angestrebten gemeinsamen Phase. Handelt es sich dabei um Mischoxide mit Spinellstruktur, um Metallphosphate oder Metallsilikate, sollten die Trennmittel- bzw. die Trennmittel/Feinpulverkombinationen so zusammengesetzt sein, dass eine stöchiometrische Umwandlung in die genannten Verbindungen stattfindet. Dabei ist zu berücksichtigen, dass ein Teil der Bestandteile der definierten Verbindungen auch aus der Oberfläche der Metallpulver stammen kann. Im Einzelfall muss die richtige Zusammensetzung der Trennmittel- bzw. Trennmittel- /Feinpulverkombination durch einfache Versuche festgelegt werden. Entstehen bei der Reaktion statt definierter Verbindungen eine gemeiname Phase in Form von Gläsern, so können bei der Zusammensetzung der Trennmittel- bzw. Trennmittel-/Feinpulverkombinationen grössere Toleranzen zugelassen werden.To produce the novel soft magnetic composite materials, metal powders are mixed with combinations of novel or known release agents or lubricants or coated with these combinations (see above). As explained, the release agents are also used in the invention to provide a composite material
to generate a high electrical resistance. However, it is so that too high a proportion of release agent reduces the density in the molding again. With regard to the compacting density, the optimum proportion of release agent based on the amount of metal powder is <about 1% by weight. Release agent levels of> about 2% by weight are therefore generally not useful. In cases in which the optimum proportion of release agent is not sufficient to produce the desired high electrical resistance, it is therefore better to disperse in the release agents oxide fine powder (primary particle diameter preferably ≤ about 100 nm) with the pyrolysis residues (see below) Separating agents react, instead of increasing the proportion of release agent significantly above the optimum in terms of press density. The amount ratio of the release agent or the release agent and fine powder depends on the composition of the desired by the reaction of the pyrolysis and optionally the fine powder common phase. If these are mixed oxides with spinel structure, metal phosphates or metal silicates, the release agent or the release agent / fine powder combinations should be composed so that a stoichiometric conversion takes place in said compounds. It should be noted that some of the components of the defined compounds may also originate from the surface of the metal powder. In individual cases, the correct composition of the release agent or release agent / fine powder combination must be determined by simple tests. If a common phase in the form of glasses forms in the reaction instead of defined compounds, then larger tolerances can be permitted in the composition of the release agent or release agent / fine powder combinations.

Beispiele für die genannten Trennmittel sind Metallseifen, wie die Stearate von Calcium, Magnesium, Aluminium, Zink, Cobalt, Eisen, Nickel, Kupfer, Molybdän und Mangan, oder Ester höherer Alkohole der Phosphor-, der Bor- oder der Kieselsäure. Beispiele der genannten Feinpulver sind Oxide, wie Fe203 und Kieselsäure.Examples of the said release agents are metal soaps, such as the stearates of calcium, magnesium, aluminum, zinc, cobalt, iron, nickel, copper, molybdenum and manganese, or esters of higher alcohols of phosphoric, boronic or silicic acid. Examples of the fine powders mentioned are oxides such as Fe 2 O 3 and silicic acid.

Das Gemisch aus Metallpulver, Trennmittel und gegebenenfalls Feinpulver wird zu Formkörpern axial verpresst. Anschliessend werden die Formkörper in einer nicht reduzierenden Atmosphäre, beispielsweise in einer Stickstoff- oder Argonatmosphäre, auf eine Temperatur erhitzt, die deutlich unterhalb der Sintertemperatur des Metallpulvers, d.h. bevorzugt unter etwa 800 DEG C und besonders bevorzugt zwischen etwa 150 und etwa 550 DEG C, liegt, damit die Trennmittel pyrolysieren. Unterhalb etwa 150 DEG C wird allenfalls unvollständig pyrolysiert und die Reaktionen verlaufen sehr langsam. Bei Temperaturen unterhalb 550 DEG C ist ausgeschlossen, dass die Metallteilchen zusammensintern und sich dabei elektrische Strompfade bilden können. Die Pyrolyserückstände reagieren bei den angewandten Temperaturen entweder miteinander und/oder mit den zugesetzten Feinpulvern und gegebenenfalls mit der Oberfläche der Metallteilchen zu den genannten, definierten chemischen Verbindungen.The mixture of metal powder, release agent and optionally Fine powder is pressed axially into shaped bodies. Subsequently, the moldings are heated in a non-reducing atmosphere, for example in a nitrogen or argon atmosphere, to a temperature which is well below the sintering temperature of the metal powder, ie preferably below about 800 ° C. and more preferably between about 150 and about 550 ° C., so that the release agents pyrolyze. Below about 150 ° C., at most incomplete pyrolysis and the reactions proceed very slowly. At temperatures below 550 ° C., it is impossible for the metal particles to sinter together and thereby form electrical current paths. The pyrolysis residues react at the temperatures used either together and / or with the added fine powders and optionally with the surface of the metal particles to said defined chemical compounds.

Die Erfindung soll im folgenden durch sechs spezielle Ausführungsbeispiele noch mehr im Detail besprochen werden.The invention will be discussed in more detail below by six specific embodiments.

Beispiel 1example 1

Ein Gemisch aus Eisenpulver und Zinkstearat und einem Mono-, Dioder Triester der Phosphorsäure mit langkettigen Alkoholen, wie beispielsweise einem Gemisch von Phosphorsäuremonostearylester und Phosphorsäuredistearylester mit einem Schmelzpunkt von 70 DEG C, als Trennmittel wurde zu einem Formkörper gepresst, wobei der Anteil der Trennmittel bezogen auf das Gewicht des Eisenpulvers etwa 1,7 Gew.-% betrug und das Atomverhältnis Zn:P bei etwa 3:2 lag. Der Formkörper wurde in einer nicht reduzierenden Atmosphäre, beispielsweise in Stickstoff, auf eine Temperatur von maximal etwa 550 DEG C erhitzt, wobei die Trennmittel zu ZnO bzw. P205 pyrolysierten und die entstandenen Oxide mit einander zu Zinkphosphat reagierten. Zinkphosphat hat - wie festgestellt wurde - einen hohen spezifischen elektrischen Widerstand, haftet gut an Metallen und schützt speziell Eisen vor Korrosion. Der erhaltene Verbundwerkstoff eignete sich als weichmagnetisches Material für schnellschaltende elektrische Ventile.A mixture of iron powder and zinc stearate and a mono-, di-triester of phosphoric acid with long-chain alcohols, such as a mixture of phosphoric acid monostearyl ester and phosphoric acid distearyl ester having a melting point of 70 ° C, as a release agent was pressed into a molded article, wherein the proportion of the release agent based on the weight of the iron powder was about 1.7% by weight and the atomic ratio Zn: P was about 3: 2. The shaped body was heated in a non-reducing atmosphere, for example in nitrogen, to a maximum temperature of about 550 ° C., whereby the separating agents pyrolyzed to ZnO or P 2 O 5 and the resulting oxides reacted with one another to give zinc phosphate. As has been stated, zinc phosphate has a high electrical resistivity, adheres well to metals and specifically protects iron from corrosion. The resulting composite material was suitable as a soft magnetic material for high-speed electrical valves.

Beispiel 2Example 2

Ein Gemisch aus Eisenpulver und Cobaltstearat und mit reaktiven Gruppen modifiziertem Polydimethylsiloxan als Trennmittel wurde zu einem Formkörper gepresst, wobei der Anteil der Trennmittel bezogen auf das Gewicht des Eisenpulvers etwa 1,6 Gew.-% betrug und das Atomverhältnis Co:Si bei etwa 1 lag. Der Formkörper wurde, wie im Beispiel 1 beschrieben, weiterbehandelt. Die aus den Trennmitteln entstandenen Pyrolyseprodukte CoO und Si02 reagierten dabei zu CoSiO3. Das Cobaltsilikat hatte auf dem Eisenpulver eine gute Haftung, war elektrisch gut isolierend und schützte Eisen gut vor Korrosion.A mixture of iron powder and cobalt stearate and reactive group-modified polydimethylsiloxane as a release agent was pressed into a molded article, wherein the proportion of the release agent based on the weight of the iron powder was about 1.6 wt .-% and the atomic ratio Co: Si was about 1 , The molding was further treated as described in Example 1. The resulting from the release agents pyrolysis CoO and SiO 2 thereby reacted to form CoSiO3. The cobalt silicate had good adhesion to the iron powder, was well electrically insulating and well protected against corrosion.

Beispiel 3Example 3

Ein Gemisch aus Eisenpulver, Cobaltstearat als Trennmittel, welchem eine stöchiometrische Menge an pyrogener Kieselsäure (Primärkorndurchmesser < etwa 100 nm) zugesetzt worden war, wurde zu einem Formkörper gepresst, wobei der Anteil des Trennmittels bezogen auf das Gewicht des Eisenpulvers bei etwa 1,3 Gew.-% lag. Der Formkörper wurde, wie im Beispiel 1 beschrieben, weiterbehandelt. Das aus dem Trennmittel entstandene Pyrolyseprodukt CoO reagierte dabei mit dem Si02 der Kieselsäure zu CoSiO3.A mixture of iron powder, cobalt stearate as a release agent, to which a stoichiometric amount of fumed silica (primary particle diameter <about 100 nm) was added was pressed into a molded article, wherein the proportion of the release agent based on the weight of the iron powder at about 1.3 wt .-% was. The molding was further treated as described in Example 1. The resulting from the release agent pyrolysis CoO reacted with the SiO 2 of the silica to CoSiO3.

Beispiel 4Example 4

Ein Gemisch aus Eisenpulver und als Trennmittel Zinkstearat und Eisenstearat wurde zu einem Formkörper gepresst, wobei der Anteil der Trennmittel bezogen auf das Gewicht des Eisenpulvers etwa 1,4 Gew.-% betrug und das Atomverhältnis Zn:Fe bei etwa 1:2 lag. Der Formkörper wurde, wie im Beispiel 1 beschrieben, weiterbehandelt. Die aus den Trennmitteln entstehenden Pyrolyseprodukte ZnO und Fe203 reagierten dabei miteinander zu dem Spinell Fe2Zn04 (Franklinit). Spinelle haben - wie festgestellt wurde - eine gute Haftung auf Eisenpulver, sie sind elektrisch gut isolierend und sie schützen Eisen ausgezeichnet gegen Korrosion.A mixture of iron powder and as a release agent zinc stearate and iron stearate was pressed into a molded article, wherein the proportion of the release agent based on the weight of the iron powder was about 1.4 wt .-% and the atomic ratio Zn: Fe was about 1: 2. The molding was further treated as described in Example 1. The resulting from the release agents pyrolysis ZnO and Fe203 reacted with each other to the spinel Fe2Zn04 (Franklinite). Spinels have - as stated - a good adhesion to iron powder, they are electrically good insulating and they protect iron excellent against corrosion.

Beispiel 5Example 5

Ein Gemisch aus Eisenpulver und Zinkstearat als Trennmittel, welchem eine stöchiometrische Menge von feinem Fe203 zugemischt worden war, das beispielsweise von der BASF AG als Pigment mit 100 nm Korngrösse erhältlich ist, wurde zu einem Formkörper gepresst, wobei der Anteil des Trennmittels bezogen auf das Gewicht des Eisenpulvers etwa 1 Gew.-% betrug. Der Formkörper wurde, wie im Beispiel 1 beschrieben, weiterbehandelt. Das aus dem Trennmittel entstandene Pyrolyseprodukt ZnO reagierte mit dem Fe203 zu dem Spinell Fe2Zn04.A mixture of iron powder and zinc stearate as a release agent to which a stoichiometric amount of fine Fe 2 O 3 was added, which is available, for example, from BASF AG as a pigment of 100 nm grain size, was pressed into a molded article, wherein the proportion of the release agent by weight of the iron powder was about 1% by weight. The molding was further treated as described in Example 1. The pyrolysis product ZnO formed from the release agent reacted with the Fe 2 O 3 to form the spinel Fe 2 ZnO 4.

Beispiel 6Example 6

Ein Gemisch, das Eisenpulver und als Trennmittel Nickelstearat und Eisenstearat enthielt, wurde zu einem Formkörper gepresst, wobei der Anteil der Trennmittel bezogen auf das Gewicht des Eisenpulvers etwa 1,5 Gew.-% betrug und das Atomverhältnis Ni: Fe bei etwa 1:2 liegt. Der Formkörper wurde, wie im Beispiel 1 beschrieben, weiterbehandelt. Die aus den Trennmitteln entstandenen Pyrolyseprodukte NiO und Fe2O3 reagierten miteinander zu dem Spinell Fe2Ni04.A mixture containing iron powder and releasing agents, nickel stearate and iron stearate, was pressed into a molded article, wherein the proportion of the releasing agent based on the weight of the iron powder was about 1.5% by weight and the atomic ratio Ni: Fe was about 1: 2 lies. The molding was further treated as described in Example 1. The resulting pyrolysis products NiO and Fe2O3 reacted with each other to form the spinel Fe2Ni04.

Claims (19)

Metallpulver-Verbundwerkstoff mit hohem spezifischem elektrischem Widerstand, dadurch gekennzeichnet, dass er mindestens zwei die Metallpulverteilchen einhüllenden Oxide enthält, wobei die Oxide mindestens eine gemeinsame Phase bilden.High electrical resistivity metal powder composite, characterized in that it contains at least two oxides enveloping the metal powder particles, the oxides forming at least one common phase. Verbundwerkstoff nach Anspruch 1, dadurch gekennzeichnet, dass er weichmagnetisch ist.Composite material according to claim 1, characterized in that it is soft magnetic. Verbundwerkstoff nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Metallpulver im wesentlichen aus Eisenwerkstoffen besteht.Composite material according to claim 1 or 2, characterized in that the metal powder consists essentially of iron materials. Verbundwerkstoff nach Anspruch 3, dadurch gekennzeichnet, dass das Metallpulver im wesentlichen aus Eisen besteht.Composite material according to claim 3, characterized in that the metal powder consists essentially of iron. Verbundwerkstoff nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass als die mindestens eine gemeinsame Phase ein Glas, wie silikatisches oder borhaltiges Glas, oder eine definierte Verbindung aus der Gruppe der Mischoxide mit Spinellstruktur, der Metallphosphate und der Metallsilikate dient.Composite material according to one of claims 1 to 4, characterized in that as the at least one common phase, a glass, such as silicate or boron-containing glass, or a defined compound from the group of mixed oxides with spinel structure, the metal phosphates and the metal silicates used. Verbundwerkstoff nach Anspruch 5, dadurch gekennzeichnet, dass die Mischoxide ausgewählt sind aus der Gruppe Al2MgO4 (Spinell), Al2ZnO4 (Zinkspinell), Al2MnO4 (Manganspinell), Al2FeO4 (Eisenspinell), Fe2MgO4 (Magnoferrit), Fe304 (Magnetit), Fe2Zn04 (Franklinit), Fe2MnO4 (Jakobsit), Fe2Ni04 (Trevirit), Cr2Fe04 (Chromit) und Cr2MgO4 (Magnochromit).Composite material according to claim 5, characterized in that the mixed oxides are selected from the group Al2MgO4 (spinel), Al2ZnO4 (zinc spinel), Al2MnO4 (manganese spinel), Al2FeO4 (iron spinel), Fe2MgO4 (magnoferrite), Fe304 (magnetite), Fe2Zn04 (Franklinite) , Fe2MnO4 (Jakobsite), Fe2Ni04 (Trevirite), Cr2Fe04 (Chromite) and Cr2MgO4 (Magnochromite). Verbundwerkstoff nach Anspruch 5, dadurch gekennzeichnet, dass Zink- und Eisenphosphat als Metallphosphate eingesetzt sind.Composite material according to claim 5, characterized in that zinc and iron phosphate are used as metal phosphates. Verbundwerkstoff nach Anspruch 5, dadurch gekennzeichnet, dass CoSiO3 als Metallsilikat eingesetzt ist.Composite material according to claim 5, characterized in that CoSiO3 is used as metal silicate. Metallpulver enthaltendes Ausgangsmaterial für die Herstellung eines Metallpulver-Verbundwerkstoffs mit hohem spezifischem elektrischem Widerstand insbesondere nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, dass es mindestens zwei Trennmitttel mit oxidischem Pyrolyserückstand oder mindestens ein Trennmittel mit oxidischem Pyrolyserückstand und oxidisches Feinpulver beinhaltet.Metal powder-containing starting material for the production of a metal powder composite material with high electrical resistivity in particular according to one of claims 1 to 8, characterized in that it contains at least two Trennmitttel with oxidic pyrolysis residue or at least one release agent with oxidic pyrolysis residue and oxide fine powder. Ausgangsmaterial nach Anspruch 9, dadurch gekennzeichnet, dass als Trennmittel mindestens eine Metallseife und/oder mindestens ein Material aus der Gruppe Mono-, Di- oder Triester der Phosphorsäure, der Borsäure oder der Kieselsäure mit langkettigen Alkoholen und/oder - gegebenenfalls - mit reaktiven Gruppen modifiziertes Polydimethyldisiloxan enthalten ist (sind).Starting material according to claim 9, characterized in that as release agent at least one metal soap and / or at least one material from the group mono-, di- or triester of phosphoric acid, boric acid or silica with long-chain alcohols and / or - optionally - with reactive groups modified polydimethyldisiloxane is (are) included. Ausgangsmaterial nach Anspruch 10, dadurch gekennzeichnet, dass die mindestens eine Metallseife ein Stearat ist.Starting material according to claim 10, characterized in that the at least one metal soap is a stearate. Ausgangsmaterial nach Anspruch 10 oder 11, dadurch gekennzeichnet, dass das Metallion in der Metallseife ausgewählt ist aus der Gruppe Ca-, Mg-, Al-, Zn-, Co-, Fe-, Ni-, Cu-, Mo- und Mn-Ion.Starting material according to claim 10 or 11, characterized in that the metal ion in the metallic soap is selected from the group Ca, Mg, Al, Zn, Co, Fe, Ni, Cu, Mo and Mn. Ion. Ausgangsmaterial nach einem der Ansprüche 9 bis 12, dadurch gekennzeichnet, dass das Feinpulver aus mindestens einem Metalloxid und/oder Kieselsäure gebildet ist.Starting material according to one of claims 9 to 12, characterized in that the fine powder is formed from at least one metal oxide and / or silica. Ausgangsmaterial nach Anspruch 13, dadurch gekennzeichnet, dass das mindestens eine Metalloxid ausgewählt ist aus der Gruppe Fe203, NiO, ZnO, CoO, MnO, MgO, Cr203, CuO, MoO2.Starting material according to claim 13, characterized in that the at least one metal oxide is selected from the group Fe203, NiO, ZnO, CoO, MnO, MgO, Cr203, CuO, MoO2. Ausgangsmaterial nach einem der Ansprüche 9 bis 14, dadurch gekennzeichnet, dass der Teilchendurchmesser (Primärkorndurchmesser) des Feinpulvers < etwa 1 mu m ist.Starting material according to one of claims 9 to 14, characterized in that the particle diameter (primary particle diameter) of the fine powder is <about 1 μm. Ausgangsmaterial nach Anspruch 15, dadurch gekennzeichnet, dass der Teichendurchmesser ≤ etwa 100 nm ist.Starting material according to claim 15, characterized in that the pond diameter ≤ about 100 nm. Ausgangsmaterial nach einem der Ansprüche 9 bis 16, dadurch gekennzeichnet, dass bezogen auf das Gewicht des Metallpulvers der Anteil der Trennmittel zwischen etwa 0,1 und etwa 2 Gew.-%, oder die Summe aus den Anteilen an Trennmittel und Feinpulver zwischen etwa 0,2 und etwa 3 Gew.-% liegt.Starting material according to one of claims 9 to 16, characterized in that based on the weight of the metal powder, the proportion of the release agent between about 0.1 and about 2 wt .-%, or the sum of the proportions of release agent and fine powder between about 0, 2 and about 3 wt .-% is. Ausgangsmaterial nach Anspruch 17, dadurch gekennzeichnet, dass die Summe aus den Anteilen an Trennmittel und Feinpulver ≤ etwa 2 Gew.-% ist.Starting material according to claim 17, characterized in that the sum of the amounts of release agent and fine powder is ≤ about 2 wt .-%. Ausgangsmaterial nach Anspruch 17 oder 18, dadurch gekennzeichnet, dass der Anteil der Trennmittel bzw. die Summe aus den Anteilen an Trennmittel und Feinpulver zwischen etwa 0,5 und etwa 1,5 Gew.-% liegt.Starting material according to claim 17 or 18, characterized in that the proportion of the release agent or the sum of the proportions of release agent and fine powder is between about 0.5 and about 1.5 wt .-%.
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DE10110341A1 (en) 2002-10-31
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