Search

WO-2025093444-A9 - FERROMAGNETIC POWDER COMPOSITION AND METHOD FOR PRODUCING THE SAME

WO2025093444A9WO 2025093444 A9WO2025093444 A9WO 2025093444A9WO-2025093444-A9

Abstract

Ferromagnetic powder composition comprising (i) soft magnetic iron-based core particles, and (ii) a first coating, at least partially covering and being in direct contact with the surface of the core particles, comprising a) a silicate of the general formula (K 2 O)α(SiO 2 )β, wherein α is moles of K 2 O, β is moles of SiO 2 , and the β/α molar ratio is in the interval from 0.5 to 4.1, wherein the silicate is present in an amount of 0.02 to 1.0 wt% calculated based on the total weight of the ferromagnetic powder composition, b) optionally, particles of a compound comprising bismuth and oxygen having a D 50 in the interval of 0.1 to 10 µm measured according to ISO 13320-1, and, c) a dopant dissolved as an oxo- or hydroxy- anion in the silicate (a). A second coating may be provided. Methods of producing the composition and manufacturing an object as well as objects comprising the composition.

Inventors

  • SKÅRMAN, Björn

Assignees

  • HÖGANÄS AB (PUBL)

Dates

Publication Date
20260507
Application Date
20241025
Priority Date
20231030

Claims (20)

  1. 1 . A ferromagnetic powder composition comprising: (i) soft magnetic iron-based core particles, and (ii) a first coating at least partially covering and being in direct contact with the surface of the core particles, the first coating comprising: a. a silicate of the general formula (K 2 O)a(SiO 2 )P, wherein a is moles of K 2 O, P is moles of SiO 2 , and the p/a molar ratio is in the interval from 0.5 to 4.1 , i. wherein the silicate is present in an amount of 0.02 to 1 .0 wt% calculated based on the total weight of the ferromagnetic powder composition, b. optionally, particles of a compound comprising bismuth and oxygen having a D 5 O measured according to ISO 13320-1 in the interval of 0.1 to 10 pm, and, c. a dopant dissolved as an oxo- or hydroxy-anion in the silicate (a).
  2. 2. The ferromagnetic powder composition according to claim 1 , wherein the first coating further comprises nanoparticles having a D 5 o measured according to ISO 13320-1 of I Q- 200 nm, or alternatively having a specific surface area (SSA) of 6-120 m 2 /g as determined according to ISO 9277:2022.
  3. 3. The ferromagnetic powder composition according to claim 2, wherein the nanoparticles are selected from the group consisting of Y 2 O3 nanoparticles, ZrO 2 nanoparticles, ZnO nanoparticles, Mg(OH) 2 nanoparticles, MgO nanoparticles, CaCOs nanoparticles, AI 2 Os nanoparticles, SiO 2 nanoparticles, and TiO 2 nanoparticles, and wherein the nanoparticles preferably comprise or consist of Y 2 O3 nanoparticles.
  4. 4. The ferromagnetic powder composition according to any of the claims 2-3, wherein the content of nanoparticles in the first coating is 1 -30 mol%, preferably 1 -20 mol% based on the molar content of K (Potassium) in the first coating.
  5. 5. The ferromagnetic powder composition according to of the claims 2-4, wherein the nanoparticles comprise or consist of Y 2 Os nanoparticles and wherein the content of nanoparticles in the first coating is 10-20 mol% based on the molar content of K (Potassium) in the first coating. 49
  6. 6. The ferromagnetic powder composition according to any preceding claim, wherein the dopant comprises at least one element from group 5, such as V (Vanadium) or Nb (Niobium), or comprises at least one element from group 6, such as Cr (Chromium), W (tungsten), or Mo (Molybdenum), or comprises Al (Aluminium) or P (Phosphorus).
  7. 7. The ferromagnetic powder composition according to any preceding claim, wherein: - the dopant comprises V and the content of dopant in the first coating is 1-30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K (Potassium) in the first coating, - the dopant comprises Nb and the content of dopant in the first coating is 1 -30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K in the first coating, - the dopant comprises Cr and the content of dopant in the first coating is 1 -30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K in the first coating, - the dopant comprises Mo and the content of dopant in the first coating is 1 -30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K in the first coating, - the dopant comprises W and the content of dopant in the first coating is 1-30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K in the first coating, - the dopant comprises Al and the content of dopant in the first coating is 0.5-5 mol%, preferably 1 -3 mol%, more preferably 1 .71-2.58 mol% based on the molar content of K in the first coating, and/or, - the dopant comprises P and the content of dopant in the first coating is 1-30 mol%, preferably 5-20 mol%, more preferably 5-15 mol%, based on the molar content of K in the first coating.
  8. 8. The ferromagnetic powder composition according to any preceding claim, wherein the dopant comprises V and the content of dopant in the first coating is 1-30 mol%, preferably 5-20 mol%, more preferably 10-15 mol%, based on the molar content of K in the first coating. 50
  9. 9. The ferromagnetic powder composition according to any preceding claim, wherein the p/a molar ratio is in the interval from 2.0 to 4.1 .
  10. 10. The ferromagnetic powder composition according to any preceding claim, wherein the first coating comprises particles of a compound comprising bismuth and oxygen having a D 5 O measured according to ISO 13320-1 in the interval of 0.1 to 10 pm.
  11. 11 . The ferromagnetic powder composition according to any preceding claim, wherein the oxo- or hydroxy-anion of the dopant is a mono anion.
  12. 12. The ferromagnetic powder composition according to any preceding claim, further comprising: (iii) a second coating at least partially covering the surface of the core particles and/or the first coating, the second coating comprising: a. at least one metal-organic compound having the general formula Rl[(Rl)x(R 2 )y(M)]nOn-lRl (I) or R2[M(OH)2(n+1)](n+1)O(n)R2 (II) wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; Ri is a hydrolysable group; R2 is an organic moiety and wherein at least one R2 contains at least one nitrogen containing group, preferably an amino group; wherein n is the number of repeating units being an integer between 1 and 20; wherein x is 0 or 1 ; and wherein y is 1 or 2, and x+y is 2, wherein the content of the at least one metal-organic compound is 0.05 to 0.40 wt%, preferably 0.10 to 0.30 wt%, based on the total weight of the ferromagnetic powder composition.
  13. 13. A ferromagnetic powder mixture comprising: 51 - the ferromagnetic powder composition according to any preceding claim, and - a further ferromagnetic powder composition, wherein the further ferromagnetic powder composition comprises soft magnetic ironbased core particles that are different from the soft magnetic iron-based core particles of the ferromagnetic powder composition, and wherein preferably the soft magnetic iron-based core particles of the further ferromagnetic powder composition comprise or consist of an iron alloy having a higher electrical resistivity and/or hardness than the soft magnetic iron-based core particles of the ferromagnetic powder composition.
  14. 14. The ferromagnetic powder mixture according to claim 13, wherein the soft magnetic iron-based core particles of the further ferromagnetic powder composition comprise or consist of an iron alloy selected from the group consisting of FeSi, FeAl, FeSiAl, FeNi, FeCo, and FeNiCo, or combinations or mixtures of such alloys.
  15. 15. The ferromagnetic powder mixture according to claim 14, wherein the iron alloy is selected from the group consisting of FeSi, preferably with 3-6.8 wt% Si, and FeSiAl, preferably with 9 wt% Si and 6 wt% Al or 3.5wt% Si and 3wt% Al.
  16. 16. The ferromagnetic powder mixture according to any of the claims 13-15, wherein the content of the further ferromagnetic powder composition is up to 90 wt%, such as 30-60 wt% or 10-50 wt%, preferably 20-40 wt%, such as 20-30 wt%, or alternatively 40-60 wt%, such as 45-55 wt%, based on the weight of the ferromagnetic powder mixture.
  17. 17. A method of producing a ferromagnetic powder composition comprising the steps of: (i) providing soft magnetic iron-based core particles, (ii) contacting the soft magnetic iron-based core particles with a first aqueous solution comprising: a. a silicate of the general formula (K 2 O)a(SiO 2 )P, wherein a is moles of K 2 O, P is moles of SiO 2 , and the p/a molar ratio is in the interval from 0.5 to 4.1 , i. wherein the silicate is present in an amount of 0.02 to 1 .0 wt% calculated based on the total weight of the ferromagnetic powder composition, b. optionally, particles of a compound comprising bismuth and oxygen having a D 5 O measured according to ISO 13320-1 in the interval of 0.1 to 10 pm, c. a dopant dissolved as an oxo- or hydroxy-anion in the silicate (a), and d. optionally, nanoparticles having a D 5 o measured according to ISO 13320-1 of 10-200 nm, or alternatively having a specific surface area (SSA) of 6- 120 m 2 /g as determined according to ISO 9277:2022.
  18. 18. The method according to claim 17, further comprising one or more of the steps of: (iii) drying the soft magnetic iron-based core particles, and/or (iv) contacting the soft magnetic iron-based core particles with at least one metalorganic compound having the general formula Rl[(Rl)x(R 2 )y(M)]nOn-lRl (I) or R2[M(OH)2(n+1)](n+1)O(n)R2 (II) wherein M is selected from the group consisting of Si, Ti, Al, and Zr; O is oxygen; Ri is a hydrolysable group; R2 is an organic moiety and wherein at least one R2 contains at least one nitrogen containing group, preferably an amino group; wherein n is the number of repeating units being an integer between 1 and 20; wherein x is 0 or 1 ; and wherein y is 1 or 2, and x+y is 2, wherein the content of the at least one metal-organic compound is 0.05 to 0.40 wt%, preferably 0.10 to 0.30 wt%, based on the total weight of the ferromagnetic powder composition, and/or (v) mixing the soft magnetic iron-based core particles with a lubricant, preferably a particulate lubricant.
  19. 19. A method of manufacturing an object from the ferromagnetic powder composition according to any of the claims 1 -12 or the ferromagnetic powder mixture according to any of the claims 13-16, comprising the steps of: (i) compacting the ferromagnetic powder composition according to any of the claims 1 -12 or the ferromagnetic powder mixture according to any of the claims 13-16 in a die at a compaction pressure in the range of 300-2000 MPa, preferably 400- 1200 MPa, to obtain a compacted part, and (ii) heat treating the compacted part in a nonreducing atmosphere, preferably comprising 0-22 wt%, more preferably 0.5 to 2 wt% oxygen (O2) at a temperature in the range of 300-800 °C, preferably 400-750 °C, more preferably 600-700 °C, to obtain the object.
  20. 20. The method according to claim 19, wherein step (ii) comprises heat treating the compacted part at a temperature of 670-700 °C, preferably 680-700 °C.

Description

FERROMAGNETIC POWDER COMPOSITION AND METHOD FOR PRODUCING THE SAME Technical field The technology proposed herein relates generally to the field of ferromagnetic powder compositions comprising soft magnetic iron-based core particles and methods for producing ferromagnetic powder compositions. Background Ferromagnetic powders include soft magnetic composite (SMC) powders which comprise soft magnetic core particles, usually iron-based, with an electrically insulating coating on each particle. Such powders may be used to obtain soft magnetic components or parts, such as by compacting the powders into the desired shape. These components or parts, also known as soft magnetic composites, may be used as an alternative to laminated steel components in electric motors, generators, electromagnets in a wide range of applications. Two key characteristics of a soft magnetic core particle and a corresponding component made from such particles, are magnetic permeability p and core loss characteristics Pc. The magnetic permeability p of a material is an indication of its ability to become magnetized or its ability to carry a magnetic flux. Maximum permeability (pmax) is defined as the highest value of B/H, i.e., the ratio of the magnetizing force B or field intensity to the induced magnetic flux H. 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 (DC-loss), which constitutes the majority of the total core losses in most motor applications, is brought about by the necessary expenditure of energy to overcome the retained magnetic forces within the part made from the soft magnetic core particles and is influenced by the retentivity, or remanence BR, and the coercivity Hc. The retained magnetic forces within the component may be minimized by increasing the quality and purity of the soft magnetic core particles and, in particular, by heat treating the component so as to cause a release of stress caused by the compaction shear forces within the component. Energy losses are further caused by Eddy current loss (AC-loss) which is caused by the induction of electric currents in the part due to the changing flux caused by alternating current (AC) conditions. The Eddy current loss is minimized by the electrically isolating coating on each particle which thereby isolates the soft magnetic core particles from each other. Accordingly, the resistivity R of the coating becomes an important parameter for defining the characteristics and useability of the soft magnetic core particles. The level of electrical resistivity R that is required to minimize the AC losses in a part made from soft magnetic core particles is dependent on the size distribution of the soft magnetic core particles, the size of the part, or the cross-sectional area of the magnetic flux, and the frequency of the alternating magnetic field in which the part is to be used. EP 2 252 419 B1 generally discloses a ferromagnetic powder composition comprising soft magnetic iron-based core particles, wherein the surface of the core particles is provided with a first inorganic insulating layer and at least one metal-organic layer, located outside the first layer. US 10,741 ,316 generally discloses a ferromagnetic powder composition including soft magnetic iron-based core particles, wherein the surface of the core particles is coated with at least one phosphorus-based inorganic insulating layer and then at least partially covered with metal-organic compound(s). EP 3 411 169 B1 generally discloses a powder mixture comprising phosphorous coated iron alloy particles and phosphorous coated iron particles. WO 2020/252551 generally concerns a particulate material comprising ferromagnetic particles covered by at least one oxide layer consisting of nanoparticles and at least one glassy layer covering the oxide layer. BE 44486 generally concerns a method of constructing magnetic cores by mixing particles of a magnetic material covered by an insulator with a particle separating material. Despite the advantages brought about by the technologies described in the above cited documents, there remains a need to provide further ferromagnetic powder compositions comprising soft magnetic core particles having improved electrical, magnetic, and/or structural properties. More particularly, there remains a need to allow heat treatment at higher temperatures while maintaining an acceptable electrical resistivity of the electrically insulating coating on each particle. Meeting this need would provide for improved ageing properties and higher resistivity for a given coercivity level and coating density/thickness level, inter alia due to an improved coverage of the coating. It would also provide for improving such properties for harder particles, which undergo less plastic deformation during compaction and therefore require higher relaxation temperatures during the heat treatment. First and second object