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
  • H01F1/086—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 sintered
• • 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
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B1/00—Single-crystal growth directly from the solid state
  • C30B1/02—Single-crystal growth directly from the solid state by thermal treatment, e.g. strain annealing
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B1/00—Single-crystal growth directly from the solid state
  • C30B1/02—Single-crystal growth directly from the solid state by thermal treatment, e.g. strain annealing
  • C30B1/06—Recrystallisation under a temperature gradient
  • C30B1/08—Zone recrystallisation
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/10—Inorganic compounds or compositions
  • C30B29/52—Alloys
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B31/00—Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor
  • C30B31/02—Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor by contacting with diffusion materials in the solid state
• • 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

Definitions

• This invention relates to sintered metallic permanent magnets.
• the invention is particularly concerned with magnets of the alnico type of the approximate composition of 10 to 40% Co, 10 to 22% Ni, to 14% Al, 0 to Cu, 0 to 10% Ti, 0 to 3% Si, the balance being Fe and not more than 1% of the conventional additives and/or impurities.
• magnets having a crystallographic texture. Such texture is due to the fact that one direction of the crystal edge [100] is oriented in parallel direction, the other crystal edges being evenly distributed in the two other spatial directions.
• the magnetic preferred direction, produced by a heat treatment in a magnetic field, as well as the direction of magnetization in the use of magnets coincide with the [100-]-direction common to all the crystallites.
• the magnets have been designated as magnets having columnar crystallization or columnar growth, whereby the [100]-direction, which is common to all the crystallites, is designated the columnar axis.
• said mixture Prior to being compressed to the ultimate shape, said mixture is subjected to a magnetic field which orients the alnico-monocrystal particles with one of their [1001-directions parallel to the magnetic field. Said oriented crystallites serve then again as crystallization nuclei.
• Wires of one of the alloying components are embedded into the mixture of the alloy-forming metal powders so as to determine the ultimate columnar axis by the wire axis.
• the amount of the component incorporated in wire form is to be taken into account when making up the mixture of the metal powders.
• the principal object of the present invention is to provide a method which avoids said drawbacks.
• the columnar crysallization is produced by means of a solid state reaction in the finished sintered body as a secondary recrystallization.
• Sintered bodies are very fine-grained and contain a large number of small pores.
• a very great num- 3,219,496 Patented Nov. 23, 1965 Ice her of grain boundaries would have to be eliminated or displaced. It was, therefore, not to be expected that a simple secondary recrystallization would produce oriented columnar crystallization.
• our novel method has the advantage that no modifications are required in the production process of the magnets including the sintering operation. It is only necessary to heat the finished sintered bodies to the recrystallization temperature. For this purpose, they are moved parallel to the desired direction of the columnar axes through a temperature range extending from a temperature immediately below their melting point to a temperature of C. below said melting point.
• the recrystallizing operation may be combined with the conventional heat treatment in a magnetic field; in this way, producing a columnar crystallization in accordance with our method requires only a small additional heat treatment of the magnets.
• the heating to recrystallization temperature may be carried out by means of an induction coil, by heat conduction, by heat radiation, or by means of electron or high energy ion beams.
• Example 1 Conventionally prepared sintered round alnico magnets having a diameter of 12 mm. and a height of 10 mm. were stacked upon each other. They were held together by means of a clamp and dipped into a mixture of finely ground quartz and ethyl silicate. The mass adhering to the surface of the magnet cylinder was dried and the procedure was repeated until a layer of about 7 mm. thickness had been deposited. Then the clamp was removed, and only a hook was left at the upper end.
• the thus obtained ceramic coat was baked by a heat treatment of 1 hour at 1200 C. in a muffle furnace whereby the heating up and cooling in the furnace was carried out together with the heating and cooling of the furnace.
• the lower end of the cylinder was heated to a temperature closely below the melting point of the alnico, which temperature was generally between 1390 and 1430 C.
• the temperature inside the coil was maintained at about 1400 C.
• the ceramic tube containing the magnets After the lower end of the ceramic tube containing the magnets had emerged from the lower end of the coil, it was placed on a water cooled chilling plate of copper of the same diameter. At the same time, a tubular furnace arranged below the medium frequency coil coaxially therewith was heated at about 1300 C. The chilling plate and ceramic tube were lowered through the tubular furnace while maintaining the above recited rate of speed.
• the ceramic tube was broken, and the magnets were subjected to the conventional heat and magnetizing treatment. Care was taken to arrange the magnetic field producing the preferential direction of magnetization parallel to the cylinder axis of the magnets.
• the (BH) values in the direction parallel to the cylinder axis were 6 to 7x10 gauss/oersted.
• Example 2 Magnets of the same dimensions as in Example 1 were stacked in a ceramic tube of 12.5 mm. inner and 16 mm. outer diameter to a height of 350 mm.
• the upper end of the tube was provided with a hook to manipulate the tube.
• At the lower end it had an inner collar of 10 mm. diameter to prevent the magnets from dropping out.
• the chilling plate applied after passage of the tube through the medium frequency coil had also a diameter of 10 mm. and could, therefore, be placed through said collar into direct contact with the lowermost magnet.
• Example 3 The test of Example 1 was repeated but the ceramic tube was not broken but carefully blown with compressed air until it had a temperature of about 900 C.; subsequently, it was placed for cooling into a cylindrical winding in which a magnetic field of 2000 oersted was maintained. In this manner, the magnetic field treatment was applied immediately following the recrystallization treatment without intermediate cooling of the magnets to room v temperature. The further heat treatment was the conventional one. The obtained magnets had (BI-I) values in the preferential direction of 6.3 to 7.4 10
• Example 4 In this example, test 2 was repeated but with the modification described in Example 3.
• the (BH), values were 6.2 to 7.5 10
• the conventional heat treatment referred to above consisted normally in heating the magnets to 1280 C. and cooling in a magnetic field of about 1500 oersted at 820 C., cooling in said field during 30 minutes to about 600 C., then cooling to room temperature, and finally a twostage annealing first 2 hours at 630 C. and then for 6 hours at 560 C., followed by cooling to room temperature.
• a method for producing a columnar crystal texture in sintered permanent magnets of the alnico type comprising heating a sintered alnico body to a temperature close to the melting point, passing the body through a zone where its temperature is lowered by about 100 0, thereby producing secondary recrystallization, and establishing in said body in the direction of its passage through said zone to a temperature gradient of 10 to 100 C./ cm. so as to produce oriented crystal growth in said direction.

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

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Citations (5)

• 1962
  • 1962-02-17 DE DEM51856A patent/DE1179967B/de active Pending
• 1963
  • 1963-02-12 US US257835A patent/US3219496A/en not_active Expired - Lifetime
  • 1963-02-15 GB GB6224/63A patent/GB978539A/en not_active Expired

Patent Citations (5)

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