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
• • 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
  • B22F9/00—Making metallic powder or suspensions thereof
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/07—Alloys based on nickel or cobalt based on cobalt
• • 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
  • H01F1/0551—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 in the form of particles, e.g. rapid quenched powders or ribbon flakes
• • 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
  • H01F1/0551—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 in the form of particles, e.g. rapid quenched powders or ribbon flakes
  • H01F1/0552—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 in the form of particles, e.g. rapid quenched powders or ribbon flakes with a protective layer

Definitions

• the present invention relates generally to the art of making permanent magnets and is more particularly concerned with new magnetic material powders having unique characteristics and with a novel method for producing these powders.
• the detrimental eifects of grinding upon the magnetic characteristics of the cobalt-rare earth materials can be eliminated and the coercive forceof mechanically-reduced materials of this kind can be enhanced to a surprising extent.
• the method of this invention centers in the key step of chemically treating the finely-divided, ground, magnetic material with an acid in a contact period sulficient to increase the coercive force of the powder significantly. Although the exact mechanism is not certain, it seems likely that the acid produces holes or channels in the particles in such a way that the form of the particle is changed with an attendant increase in coercive force.
• This invention thus centers in the concept of subjecting these ground materials to an acid treatment to eliminate the degrading effects of the grinding upon their magnetic properties.
• the invention is also based upon my discovery that such treatment can result in surprisingly large increases in coercive force of these cobalt-rare earth materials.
• the chemical treatment is carried out according to this invention by contacting cobalt-rare earth magnetic material with an acid, the material in powder form preferably being immersed in the acid for the required period of contact time and then promptly removed and rinsed free from that acid in order to arrest the acid attack.
• the acid will be at room temperature but it may be at any temperature at which the acid is a liquid. At room temperature, i.e. about 25 C., the contact period generally ranges from about a few seconds to about ninety minutes.
• the specific contact period necessary to obtain a maximum coercive force for a particular powder is determinable empirically and depends largely on particle size, the specific acid used and its concentration, and acid temperature. Generally, shorter contact periods are required when smaller particles are used or when more concentrated acids or acids substantially above room temperature are used. However, prolonged acid contact may lead to significantly diminishing magnet material yields, particularly if the treating acid temperature is substantially above room temperature.
• acids useful in the present invention are hydrochloric acid, nitric acid, phosphoric acid, sulphuric acid and acetic acid.
• concentration of the acid used may vary widely. Generally, the more dilute an acid, the longer is the contact time required to produce a maximum coercive force.
• cobalt-rare earth magnet material of particle size ranging from less than 30 microns to mesh (between 88 and 147 microns) (U.S. standard screen sizes).
• Materials of this kind may, however, be treated according to this invention with the foregoing results when the particles are twice as large, but the maximum coercive force obtainable is lower because of the fact that coercive force generally varies inversely with particle size.
• Much finer particles may likewise be treated in accordance with this method but at the cost of smaller product yields because of the relatively larger proportion of each particle dissolved in the acid attack.
• This invention method has been found in actual practice to be particularly beneficial in the treatment of cobaltbase permanent magnet materials including Co Y, Co Sm and Co M (cerium-rich misch metal).
• EXAMPLE 1 An ingot of cobalt-Samarium (Co Sni) was ground with mortar and pestle. The resulting powder was screened and the fraction passing through a 325 mesh screen was selected for test. Substantially equal portions of this fine powder fraction were used in the preparation of four samples.
• One sample was prepared by introducing a portion of the powder into a body of molten paraffin wax and cooling the wax in an aligning magnetic field of 21,000 oersteds until it was solidified.
• Another portion of the powder was immersed in 2% nitric acid at room temperature, i.e. about 25 C. At the end of 30 seconds, the powder was removed from the acid, rinsed with water and with acetone, and permitted to dry in air. Additional portions of the powder were treated in the same manner except that they were immersed in the 2% nitric acid for 60 seconds and 90 seconds, respectively. Each of the treated, dried, powder portions was then mounted in parafiin as described above.
• the coercive force of the cobalt-yttrium powder is increased significantly after relatively short period of immersion in the acid.
• Co Y Cobalt-yttrium
• the procedure in this example was the same as that disclosed in Example 1 except that the acids given in Table V were used, and the coercive force was measured after magare given in Table I. netization in a field of 21,000 oersteds.
• Table V illustrates the number of ditferent acids which As illustrated in Table II, the coercive force of cobaltsamarium powder as fine as less than 30 microns can be increased significantly by short periods of immersion in an acid as dilute as 1% nitric acid.
• EXAMPLE 3 In this example the procedure was the same as that disclosed in Example 1 except that the ground cobaltsamarium fraction passing a 250 mesh and returned on a 325 mesh screen was selected for test and 1% nitric acid was used. The results are given in Table III.
• EXAMPLE 6 In this example cobalt-yttrium (Co Y) was used. The procedure in this example was the same as that disclosed in Example 5 except that the ground fraction passing through a mesh screen and returned on a mesh screen was used for test and the acid was 2% nitric acid.
• the procedure in this example was the same as that disclosed in Example 1 except that the coercive force was measured after magnetization in a field of 21,000 oersteds.
• a sample of the powder was immersed in 2% nitric acid at room temperature for 30 seconds. At the end of this time its coercive force was measured as being 1725 oersteds.
• EXAMPLE 8 In this example cobalt-yttrium (Co -Y) was used. The procedure used in this example was the same as that disclosed in Example 5 except that the ground fraction passing through a 250 mesh screen and returned on a 325 mesh screen was used for test and the acid was 2% nitric acid.
• ground, fineparticle material ranges in size from less than 30 microns to up to about 147 microns.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Hard Magnetic Materials (AREA)
• Soft Magnetic Materials (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=24935903

Family Applications (1)

Country Status (7)

Cited By (5)

Families Citing this family (1)

• 1968
  • 1968-05-20 US US730577A patent/US3558371A/en not_active Expired - Lifetime
• 1969
  • 1969-05-02 GB GB22515/69A patent/GB1263382A/en not_active Expired
  • 1969-05-13 ES ES367179A patent/ES367179A1/es not_active Expired
  • 1969-05-14 NL NL6907474A patent/NL6907474A/xx not_active Application Discontinuation
  • 1969-05-17 DE DE1925269A patent/DE1925269C3/de not_active Expired
  • 1969-05-20 BE BE733308D patent/BE733308A/xx not_active IP Right Cessation
  • 1969-05-20 FR FR6916400A patent/FR2008948A1/fr not_active Withdrawn

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