Classifications

• • 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
  • H01F1/032—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 hard-magnetic materials
  • H01F1/04—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 hard-magnetic materials metals or alloys
  • H01F1/047—Alloys characterised by their composition
  • H01F1/053—Alloys characterised by their composition containing rare earth metals
  • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
  • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
  • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
  • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
  • H01F1/0576—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together pressed, e.g. hot working
• • 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
  • B22F1/14—Treatment of metallic powder
  • B22F1/142—Thermal or thermo-mechanical treatment
• • 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
  • H01F41/0253—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 for manufacturing permanent magnets
  • H01F41/0273—Imparting anisotropy

Definitions

• the invention relates to a method for producing a material with a hard magnetic phase, in which a powder mixture of the elementary and / or powdery components of the material present as compounds or alloys is subjected to a grinding process in the manner of mechanical alloying and the hard magnetic phase in the powder particles formed in this way are formed by means of a heat treatment.
• a method for producing a material with a hard magnetic phase in which a powder mixture of the elementary and / or powdery components of the material present as compounds or alloys is subjected to a grinding process in the manner of mechanical alloying and the hard magnetic phase in the powder particles formed in this way are formed by means of a heat treatment.
• magnetic materials have been known which, in terms of the most important hard magnetic size, namely the energy product, far exceed all previously known materials.
• a material that has at least largely a hard magnetic tetragonal phase of the composition Nd2Fe14B. Partial substitution of the individual elements of the material and / or slight deviations from the stoichiometry of the tetragonal phase are possible in order to optimize the microstructure of the material. Since the magnetic values such as the remanence and in particular the energy product for magnetically anisotropic materials are much better than for magnetically isotropic materials, efforts are being made to develop processes with which the powder produced can be made magnetically anisotropic or a magnetically anisotropic compact body from this powder can be manufactured.
• an intermediate product is first produced by rapid quenching from the melt of the starting components, which is then compacted by hot pressing and finally in a further process step, the so-called "die-upsetting" Compression presses, is aligned in the magnetic preferred direction (see, for example, "Appl.Phys.Lett.”, Vol. 46, No. 8, June 15, 1985, pages 790 and 791).
• the powder is first compacted at a high temperature in a hot press.
• the compact is then in turn deformed at a high temperature of about 700 ° C. in a widened die, with a magnetic anisotropy with the slight direction occurring parallel to the pressing direction.
• powders of the elements involved which may also be in the form of master alloys or as compounds, are first converted into a mixed powder by grinding in a powder mill. This mixed powder then reacts in a subsequent annealing treatment to the desired NdFeB alloy with high coercive force.
• the resulting powder is magnetically isotropic, however, because each powder particle consists of a large number of grains with an arbitrary crystal orientation.
• the object of the present invention is therefore to design the method of the type mentioned at the outset such that it can also be used to produce magnetically anisotropic powders in a relatively simple manner.
• This object is achieved in that the heat treatment for forming the hard magnetic phase is provided during the grinding process and that the resulting powder particles of the hard magnetic phase are further subjected to the grinding process at elevated temperature in such a way that a magnetically anisotropic structure results in them.
• the invention is based on the one hand on the knowledge that the desired hard magnetic phase can be generated in situ in the known grinding process if a simultaneous heat treatment is provided.
• the powder particles with the hard magnetic phase can be deformed, which leads to a magnetic anisotropy of the material with the slight direction of magnetization parallel to the direction of deformation.
• the heating of the individual powder particles during the process according to the invention can be carried out either directly due to impact processes of the grinding balls and / or by an external heating.
• the minimum temperatures for the formation of the hard magnetic phase or the texturing in the powder particles must be taken into account.
• powders of the starting components involved are assumed. Elemental powders are advantageously used.
• the elements involved can also be present in the form of alloys and / or compounds.
• the powdered starting components are placed with hardened steel balls in a suitable grinding device, the ratio of the three powder types of the powder mixture being determined by the predetermined resulting atomic concentration of the hard magnetic material to be produced from these powders.
• These three powders with predetermined, generally familiar particle sizes are then subjected to a grinding process, as is known in principle from mechanical alloying processes.
• the duration of the grinding process depends in particular on the grinding parameters. Important parameters are the ball diameter, the number of balls and the materials used for the grinding device.
• the grinding speed and the ratio of the steel balls to the amount of powder are further parameters that determine the necessary grinding time.
• the method according to the invention is also of crucial importance that the powders are heated considerably during the grinding process.
• temperatures of at least 500 ° C., preferably at least 600 ° C. should be present.
• Corresponding temperatures can be generated, for example, by means of sufficient grinding intensity due to the impact processes of the grinding balls.
• the heating to the temperatures mentioned can also be supported or ensured by an external heating device.
• the grinder can be heated to approximately 300 ° C. The required higher temperatures on the regrind are then achieved due to the impact processes of the grinding balls.
• powder particles of a mixed powder initially form. These powder particles consist of an intimate mixture of Fe and Nd with embedded B-particles, the particle size of which is significantly smaller than 1 ⁇ m. The powder particles themselves have a diameter of approximately 1 to 200 ⁇ m. As the grinding process progresses, these powder particles of the mixed powder are then converted into powder particles with the desired hard magnetic Nd2Fe14B phase by a diffusion reaction due to the temperature conditions according to the invention. The grinding time required for this can easily be determined by examining the powder particles.
• the powder particles of the hard magnetic phase formed in this way are further deformed at high temperature by means of the milling process until the desired anisotropic structure (or texturing) is established due to deformation and / or recrystallization effects.
• the alignment mechanisms acting here are similar to those in the so-called “die-upsetting” (cf. "Appl.Phys.Lett.”, Vol. 46, No. 8, June 15, 1985, pages 790 and 791 or Vol. 53, No. 4, 25.7.88, pages 342 and 343).
• the temperature conditions to be provided for this part of the grinding process do not necessarily have to match those during the previous formation of the hard magnetic phase.
• the minimum temperature required for the formation of the desired texturing of the powder particles is in fact many times higher than the minimum temperature for the formation of the hard magnetic phase. A corresponding increase in temperature can therefore be provided in the method according to the invention. However, it is equally possible to form the hard magnetic phase at the higher temperature. In general, the minimum temperature for forming the anisotropic structure is around 650 ° C. Here, too, the required grinding time can easily be determined by experimentally examining the resulting powder particles.
• the process step for the formation of the hard magnetic phase and the process step for the formation of the anisotropic structure need not take place successively. Rather, a smooth transition between these two process steps can be observed. This is particularly the case if the measurement process is carried out in such a way that the powder particles reach temperatures above the minimum temperature of, for example, 650 ° C. during the collision processes to form the anisotropic structure.
• the hard magnetic powder produced according to the invention can then be processed further in a known manner. For example, it can be compacted after magnetic alignment.
• a plastic-bonded anisotropic permanent magnet can also be produced from the hard magnetic powder by casting with a plastic without a special compacting step.
• the composition of the material on which the exemplary embodiment is based can differ from the stoichiometric composition Nd2Fe14B during weighing.
• Nd can be selected from a heavy rare earth element such as partially replaced by Dy or Tb or completely by Pr.
• another element from the group of late transition metals such as Provide Co or Ni.
• substitution of Fe by Zr or Ti can also be advantageous.
• partial replacement by Al is also possible.
• B can be partially substituted by another metalloid.
• the method according to the invention is not restricted to these materials. It can equally well be applied to other types of hard magnetic materials, provided that they can also be made by mechanical alloying.
• a corresponding example are materials with a ThMn 12 structure, such as from the Fe-Mo-Sm material system (see, for example, EP-A-0 278 342).

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Hard Magnetic Materials (AREA)

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• 1988
  • 1988-09-23 DE DE3832472A patent/DE3832472A1/de not_active Withdrawn
• 1989
  • 1989-09-11 EP EP89116775A patent/EP0360120A1/fr not_active Ceased

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