WO2005035171A1 - Method of producing a soft magnetic composite component with high resistivity - Google Patents

Method of producing a soft magnetic composite component with high resistivity Download PDF

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Publication number
WO2005035171A1
WO2005035171A1 PCT/SE2003/001579 SE0301579W WO2005035171A1 WO 2005035171 A1 WO2005035171 A1 WO 2005035171A1 SE 0301579 W SE0301579 W SE 0301579W WO 2005035171 A1 WO2005035171 A1 WO 2005035171A1
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WO
WIPO (PCT)
Prior art keywords
soft magnetic
iron
magnetic composite
resistivity
powder
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Application number
PCT/SE2003/001579
Other languages
French (fr)
Inventor
Lars Hultman
Erich Brandner
Original Assignee
Höganäs Ab
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Publication date
Application filed by Höganäs Ab filed Critical Höganäs Ab
Priority to AU2003269761A priority Critical patent/AU2003269761A1/en
Priority to PCT/SE2003/001579 priority patent/WO2005035171A1/en
Publication of WO2005035171A1 publication Critical patent/WO2005035171A1/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
    • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
    • C22C32/0094—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with organic materials as the main non-metallic constituent, e.g. resin
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0206—Manufacturing of magnetic cores by mechanical means
    • H01F41/0246—Manufacturing of magnetic circuits by moulding or by pressing powder
    • 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
    • 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
    • H01F1/28—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 dispersed or suspended in a bonding agent

Definitions

  • the present invention relates to a method of improving the resistivity of a soft magnetic composite component. More specifically, the invention concerns a method of improving the resistivity of a moulded, heat treated component made of a mixture of an iron-based powder and an organic resin.
  • Soft magnetic materials are used for applications, such as core materials in inductors, stators and rotors for electrical machines, actuators, sensors and transformer cores.
  • soft magnetic cores such as rotors and stators in electric machines, are made of stacked steel laminates.
  • Soft Magnetic Composite, SMC materials are based on soft magnetic particles, usually iron-based, with an electrically insulating coating on each particle.
  • SMC parts are obtained.
  • This powder metallurgical technique it is possible to produce materials having a higher degree of freedom in the design of the SMC component than by using the steel laminates, as the SMC material can carry a three dimensional magnetic flux and as three dimensional shapes can be obtained by the compaction process.
  • Two key characteristics of an iron core component are its magnetic permeability and core loss characteristics.
  • the magnetic permeability of a material is an indication of its ability to become magnetised or its ability to carry a magnetic flux. Permeability is defined as the ratio of the induced magnetic flux to the magnetising force or field intensity.
  • the desired powder properties include suitability for compression moulding techniques, which i.e. means that the powder can be easily moulded to a high density component, which can be easily ejected from the moulding equipment.
  • compression moulding techniques which i.e. means that the powder can be easily moulded to a high density component, which can be easily ejected from the moulding equipment.
  • the resistivity of the coating surrounding the particles of the soft magnetic metal powder By altering for example the chemical composition or the thickness of the coating, the resisitivity is affected.
  • improvements of the resistivity normally have a negative effect on the magnetic permeability of a soft magnetic composite component at a given density.
  • a large number of patent publications teach different types of electrically insulating coatings.
  • Heat treatment of the obtained soft magnetic composite body is applied in order to reduce the induced strains during moulding and promote the magnetic permeability.
  • a higher heat treatment temperature is favourable in terms of permeability but reduces the resistivity.
  • the allowable heat-treating temperature is restricted by the decomposition temperature of the resin.
  • Lubricants used could be traditionally used lubricants for moulding of PM-components, such as Kenolube, metal stearates, ethylene-bis-stearamide or derivates of fatty acids, or materials which apart from being utilised as a binder for the soft magnetic composite component also will act as a lubricating agent, such as thermoplastic or thermosetting resins.
  • the total amount of organic additives could be limited enabling the possibility of reaching higher green densities of the moulded body.
  • a crucial aspect when moulding components based on insulated soft magnetic composite powder is that the insulation of the individual particles are maintained after moulding and ejection and especially that the coating of the particles which is in contact with the die wall are not deteriorated, i.e. that the resistivity of the surface of the component is not decreased. According to the present invention it has been found that a remarkable improvement in resistivity for a moulded, heat treated soft magnetic composite component (containing thermoplastic or thermosetting resins) can be obtained provided the moulding is performed with, the aid of die wall lubrication.
  • EXAMPLE 1 This example describes the effect off die wall lubrication on the conductivity for a soft magnetic composite component compared with similar components produced without the aid of die wall lubrication .
  • Ten magnetic rings with the dimensions 55x47x4 mm were produced by uniaxial moulding at three different moulding pressures. Five rings were produced with the aid of die wall lubrication and five rings without s uch lubrication.
  • Two different compositions containing soft magnetic composite powder mixed with a binder we e tested.
  • the soft magnetic composite powder was produced according to US Patent 6 348 265. Organsol in amounts of 0.4% and 0.6% by weight, respectively, was used as binder.

Abstract

This invention concerns a method of improving the resistivity of an iron based soft magnetic composite component comprising the steps of providing a mixture consisting of an iron-based powder and a binder; moulding the mixture in a lubricated die; ejecting the compacted body from the die and optionally heat-treating the obtained body.

Description

METHOD OF PRODUCING A SOFT MAGNETIC COMPOSITE COMPONENT WITH HIGH RESISTIVITY
FIELD OF THE INVENTION The present invention relates to a method of improving the resistivity of a soft magnetic composite component. More specifically, the invention concerns a method of improving the resistivity of a moulded, heat treated component made of a mixture of an iron-based powder and an organic resin. BACKGROUND OF THE INVENTION Soft magnetic materials are used for applications, such as core materials in inductors, stators and rotors for electrical machines, actuators, sensors and transformer cores. Traditionally, soft magnetic cores, such as rotors and stators in electric machines, are made of stacked steel laminates. Soft Magnetic Composite, SMC, materials are based on soft magnetic particles, usually iron-based, with an electrically insulating coating on each particle. By compacting the insulated particles optionally together with lubricants and/or binders using the traditionally powder metallurgy processes, SMC parts are obtained. By using this powder metallurgical technique it is possible to produce materials having a higher degree of freedom in the design of the SMC component than by using the steel laminates, as the SMC material can carry a three dimensional magnetic flux and as three dimensional shapes can be obtained by the compaction process. Two key characteristics of an iron core component are its magnetic permeability and core loss characteristics. The magnetic permeability of a material is an indication of its ability to become magnetised or its ability to carry a magnetic flux. Permeability is defined as the ratio of the induced magnetic flux to the magnetising force or field intensity. When a magnetic material is exposed to a varying field, energy losses occur due to both hysteresis losses and eddy current losses. The hysteresis loss is brought about by the necessary expenditure of energy to overcome the retained magnetic forces within the iron core component. The eddy current loss is brought about by the production of electric currents in the iron core component due to the changing flux caused by alternating current (AC) conditions . Research in the powder-metallurgical manufacture of magnetic core components using coated iron-based powders has been directed to the development of iron powder compositions that enhance certain physical and magnetic properties without detrimentally affecting other properties of the final component. Desired component properties include e.g. a high permeability through an extended frequency range, low core losses, high saturation induction, and high strength. Normally an increased density of the component enhances all of these properties. The desired powder properties include suitability for compression moulding techniques, which i.e. means that the powder can be easily moulded to a high density component, which can be easily ejected from the moulding equipment. In order to minimize the eddy current losses in components made of soft magnetic composite powders much effort have been directed to increase the resistivity of the coating surrounding the particles of the soft magnetic metal powder. By altering for example the chemical composition or the thickness of the coating, the resisitivity is affected. However, improvements of the resistivity normally have a negative effect on the magnetic permeability of a soft magnetic composite component at a given density. A large number of patent publications teach different types of electrically insulating coatings. Examples of recently published patents concerning inorganic coatings are the US Patents 6 309 748 and US 6 348 265. Coatings of organic materials are known from e.g. the US Patent 5 595 609. Coatings comprising both inorganic and organic material are known from e.g. the US Patent 6 372 348 and 5 063 011, according to which publication the particles are surrounded by an iron phosphate layer and a thermoplastic material . The traditional method of compaction in rigid tooling at ambient or elevated temperature is the most prevalent form of consolidation of an iron-based soft magnetic composite composition. A lubricant is necessary in the composition to enable the pressed green part to be ejected from the die. Heat treatment of the obtained soft magnetic composite body is applied in order to reduce the induced strains during moulding and promote the magnetic permeability. A higher heat treatment temperature is favourable in terms of permeability but reduces the resistivity. Furthermore, when a thermoplastic or thermosetting resin is used for bonding the soft magnetic composite body the allowable heat-treating temperature is restricted by the decomposition temperature of the resin. Lubricants used could be traditionally used lubricants for moulding of PM-components, such as Kenolube, metal stearates, ethylene-bis-stearamide or derivates of fatty acids, or materials which apart from being utilised as a binder for the soft magnetic composite component also will act as a lubricating agent, such as thermoplastic or thermosetting resins. By utilising a lubricant/binder the total amount of organic additives could be limited enabling the possibility of reaching higher green densities of the moulded body. A crucial aspect when moulding components based on insulated soft magnetic composite powder is that the insulation of the individual particles are maintained after moulding and ejection and especially that the coating of the particles which is in contact with the die wall are not deteriorated, i.e. that the resistivity of the surface of the component is not decreased. According to the present invention it has been found that a remarkable improvement in resistivity for a moulded, heat treated soft magnetic composite component (containing thermoplastic or thermosetting resins) can be obtained provided the moulding is performed with, the aid of die wall lubrication. EXAMPLE 1 This example describes the effect off die wall lubrication on the conductivity for a soft magnetic composite component compared with similar components produced without the aid of die wall lubrication . Ten magnetic rings with the dimensions 55x47x4 mm were produced by uniaxial moulding at three different moulding pressures. Five rings were produced with the aid of die wall lubrication and five rings without s uch lubrication. Two different compositions containing soft magnetic composite powder mixed with a binder we e tested. The soft magnetic composite powder was produced according to US Patent 6 348 265. Organsol in amounts of 0.4% and 0.6% by weight, respectively, was used as binder. An EDS (electrostatic deposition) equipment from Gasberre together with was a die wall lubricant, Promold™, was used. All rings were heat treated at 225°C for 60 minutes in an atmosphere of air. The conductivity of the rings were further tested with a four point mesuring method according to reference "Koefoed 0., 1979, Geosounding Principles 1: Resistivity sounding measurements. Elsevier Science Publishing Company, Amsterdam. Table 1 shows remarkably decreased conductivity (= improved resistivity), for the rings produced with the aid of die wall lubrication. TABLE 1
Figure imgf000006_0001

Claims

Claims
1. A method of improving the resistivity of an iron based soft magnetic comoposite component comprising the steps of providing a mixture comprising an iron-based powder and a binder; moulding the mixture in a lubricated die; ejecting the compacted body from the die and optionally heat-treating the obtained body.
2. Method according to claim 1 wherein the iron-based powder is an essentially pure iron powder, the particles of which are provided with an electrically insulating layer.
3. Method according to claim 2 wherein the electrically insulating layer is a phosphorus containing layer.
4. Method according to any one of the claims 1 -3 wherein the binder is a thermoplastic or thermosetting resin.
PCT/SE2003/001579 2003-10-10 2003-10-10 Method of producing a soft magnetic composite component with high resistivity WO2005035171A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU2003269761A AU2003269761A1 (en) 2003-10-10 2003-10-10 Method of producing a soft magnetic composite component with high resistivity
PCT/SE2003/001579 WO2005035171A1 (en) 2003-10-10 2003-10-10 Method of producing a soft magnetic composite component with high resistivity

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SE2003/001579 WO2005035171A1 (en) 2003-10-10 2003-10-10 Method of producing a soft magnetic composite component with high resistivity

Publications (1)

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WO2005035171A1 true WO2005035171A1 (en) 2005-04-21

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5980603A (en) * 1998-05-18 1999-11-09 National Research Council Of Canada Ferrous powder compositions containing a polymeric binder-lubricant blend
US6331270B1 (en) * 1999-05-28 2001-12-18 National Research Council Of Canada Manufacturing soft magnetic components using a ferrous powder and a lubricant
US6372348B1 (en) * 1998-11-23 2002-04-16 Hoeganaes Corporation Annealable insulated metal-based powder particles
WO2002089154A1 (en) * 2001-05-02 2002-11-07 National Research Council Of Canada Manufacturing soft magnetic components using a ferrous powder and a lubricant
US20020189714A1 (en) * 2000-02-09 2002-12-19 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Method for the compaction of soft magnetic powder

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5980603A (en) * 1998-05-18 1999-11-09 National Research Council Of Canada Ferrous powder compositions containing a polymeric binder-lubricant blend
US6372348B1 (en) * 1998-11-23 2002-04-16 Hoeganaes Corporation Annealable insulated metal-based powder particles
US6331270B1 (en) * 1999-05-28 2001-12-18 National Research Council Of Canada Manufacturing soft magnetic components using a ferrous powder and a lubricant
US20020189714A1 (en) * 2000-02-09 2002-12-19 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Method for the compaction of soft magnetic powder
WO2002089154A1 (en) * 2001-05-02 2002-11-07 National Research Council Of Canada Manufacturing soft magnetic components using a ferrous powder and a lubricant

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