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
  • H01F1/06—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 in the form of particles, e.g. powder
  • H01F1/08—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 in the form of particles, e.g. powder pressed, sintered, or bound together
• • 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
  • H01F1/0555—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together
  • H01F1/0557—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together sintered
• • 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

• This invention relates to a method for producing magnets with improved remanence.
• magnets from powdered magnetic alloys, including rare earth cobalt magnets, by compacting as by die pressing a charge of aligned or oriented fine powder of a magnetic alloy of the desired magnet composition. Thereafter, the compacted charge is heat treated at temperatures of the order of 1093 to 1143°C (2000 to 2090°F). It is known that by increasing the density in the production of magnets of this type from particle charges of the magnetic material that remanence can be improved. Conventionally, density is increased by raising the sintering temperature after die pressing; however, this results in a corresponding lowering of coercive force.
• Another object of the invention is in the production of magnets to provide for improved alignment or orientation to achieve higher remanence values.
• the present invention provides a method for producing magnets with improved remanence by consolidating a particle charge of a magnet alloy to form a magnet article, characterised in that said method comprises applying a magnetic field to said particle charge within a container to magnetically align said particles, said magnetic field being applied as at least one pulse with each said pulse having a duration not exceeding one second and a power level of at least 50,000 oersted (39789 ampere turns per centimetre) and thereafter consolidating said particle charge to a final density.
• the present invention also provides a method for producing magnets with improved remanence by consolidating a particle charge of a magnet alloy to form a magnet article, characterised in that said method comprises applying a magnetic field to said particle charge to magnetically align said particles, and thereafter hot isostatically pressing said particles to consolidate the same to full density.
• samarium to a temperature that is below the full density sintering temperature but above the temperature necessary to produce a close-pore structure and then subjects the material while at this temperature to isostatic compacting, increased density and thus improved remanence is achieved while maintaining good coercive force.
• Coercive force is maintained by maintaining the temperature below the full density sintering temperature.
• remanence is improved by aligning or orienting the material by the use of a pulsating magnetic field within a container.
• the container may be a collapsible container within which the material can thereafter be isostatically compacted.
• the pulsating magnetic field should have a pulse duration not exceeding one second per pulse and each pulse typically will be of the order of 15 millisecond.
• At least one pulse and preferably two pulses at a power level of at least 50,000 Oe (39789 ampere turns per centimetre) is suitable for the purpose.
• the particles may be compacted to an intermediate density by additional pulsing.
• highly oriented SmCo S magnets have been produced by the use of superconducting solenoids to generate the high-intensity magnetic fields.
• These superconducting solenoids must be operated at cryogenic temperatures (-268°C (-450°F)) to pass the high-density current necessary to generate these high-intensity magnetic fields.
• the required high-intensity magnetic fields are preferably produced by discharging an assemblage of capacitors, e.g. four hundred to one thousand capacitors, thereby eliminating the need for superconducting solenoids.
• the container may be a rubber bag and preferably after alignment the bag is evacuated in the presence of a constant DC field which serves to maintain alignment.
• the particles of magnet material may be aligned within a preformed container, which will be collapsible and of a material such as stainless steel.
• the step of subjecting the aligned material to a steady DC field in an evacuated container has been found to "lock in” the alignment and thus ensure improved remanence.
• Consolidation of the particles may be effected in any suitable manner, eg., by die pressing plus sintering, by cold isostatic compactions plus sintering or by hot isostatic pressing.
• the sintered magnet was loosely wrapped with stainless steel foil (not pressure tight; for handling convenience only) and as-hot-isostatically pressed (HIPed) at 954 0 C (1750°F).
• the as-HIPed magnet had the properties as set forth in Table I.
• the HIPed magnet was reheat treated at 910°C (1670°F) for three hours and quenched.
• the magnetic properties after HIPing and heat treatment are set forth in Table I.
• Example 2 Another magnet prepared according to the same procedures prescribed as in Example 1 had the properties set forth in Table II.
• Example 3 Another magnet of SmCo S from a batch other than in Examples 1 and 2 was prepared as described in Example 1. The properties are recorded in Table III.
• Example 4 Using the powder from the same batch as in Example 3, a magnet was made by sintering SmCo S powder that was previously oriented and cold isostatically pressed. The magnet had the properties set forth in Table IV.
• Example 5 SmCo5 alloy was loaded into a stainless container and hydrogen admitted into the container. The pressure was built up to 30 atmospheres; hydrogen absorption by the alloy results in a disintegration of the alloy to about -80 mesh powder. The dehydrided powder was jet milled to about 4 particle size.
• the fine powder was loaded into a rubber bag of 19.05mm (3/4") diameter and the bag was contained in a stainless or plastics sheath.
• the bag was then pressurized and the powder oriented by placing the rubber bag along with the sheath inside a coil, and pulsing the coil, at least three times, with enough power to generate 60,000 Oe (47746 ampere turns per centimetre) within the coil.
• the oriented powder was then placed in a steady DC field of ⁇ 10 kOe and the bag evacuated to lock the alignment.
• the evacuated bag containing the powder was then placed in an isostatic press chamber and compressed with a pressure up to 7040 Kg/cm 2 (100,000 psi).
• the green compact was subsequently sintered between 1000-1200°C and post sinter aged between 870-930°C.
• the magnets prepared from these four batches of powder in the manner described above had the properties set forth in Table V, which Table also shows magnetic properties of conventional commercial magnets.
• Example 6 Powder of SmCo 5 was loaded in a rubber bag and oriented in the poles of an electromagnet in a field of 25 kOe. The oriented powder was then evacuated maintaining the steady DC field. The evacuated bag containing the oriented powder was isostatically pressed followed by.sintering and heat treatment. The magnet had the following properties as shown in Table VI.
• Example 7 A fourth batch of SmCo S was processed into magnets by procedures as described in Example 1 except for a change in the compaction method.
• the powder contained in the bag after alignment was initially compacted inside the bag by placing the bag towards the end of the coil and employing the field gradient present in the coil during pulsing to bring forth an initial compaction to an intermediate density by additional pulsing.
• the oriented compacted powder placed in a steady DC field was evacuated, isostatically pressed and sintered.
• the sintered sample was of uniform diameter and had a flat top and bottom contrary to the samples prepared without the field gradient packing which had a pyramidal top.
• the magnetic properties of the sintered magnet prepared as per this example are shown in Table VII.
• Example 8 A rectangular preform which has the dimensions of a die cavity was loaded with powder and the powder was oriented in a pulse coil. The oriented powder in the preform was transferred to a die press and placed between the upper and lower punches. After all the powder had transferred into the die cavity the powder was pressed between the upper and lower punches under the application of a DC field. The die pressed part was sintered and post sintered. The magnet prepared in this manner had the following properties set forth on Table VIII.
• Example 9 From the same batch of powder one magnet was pressed by directly feeding the powder into the die cavity, applying the DC field, and pressing. The properties of these two magnets are set forth in Table VIII.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Manufacturing Cores, Coils, And Magnets (AREA)
• Powder Metallurgy (AREA)
• Hard Magnetic Materials (AREA)

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Cited By (4)

Citations (3)

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• 1982
  • 1982-01-21 CA CA000394598A patent/CA1176814A/en not_active Expired
  • 1982-02-01 EP EP19820300510 patent/EP0066348B1/de not_active Expired
  • 1982-02-01 DE DE8282300510T patent/DE3266728D1/de not_active Expired
  • 1982-05-10 JP JP57078057A patent/JPS57194512A/ja active Granted

Patent Citations (3)

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