Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F3/00—Brightening metals by chemical means
  • C23F3/04—Heavy metals
  • C23F3/06—Heavy metals with acidic solutions
• • 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
  • B22F1/145—Chemical treatment, e.g. passivation or decarburisation
• • 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
  • H01F1/06—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

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 eiTects of grinding upon the magnetic characteristics of the cobalt-rare earth materials can be eliminated and the coercive force of 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 smoothing the surfaces of finely-divided, ground, magnetic material. This step is carried out with an acid mixture in a contact period of from a few seconds to 30 minutes during which time the individual powder particles preferably are not substantially reduced in size but their sharp edges and points are rounded and smoothed by acid attack.
• This invention thus centers in the concept of subjecting these ground materials to a chemical treatment to eliminate the degrading effects of the grinding upon their magnetic properties.
• the invention is also based upon my discoveries that such treatment can result in surprisingly large increases in coercive force of these cobalt-rare earth materials, and that this result can be obtained without incurring a significant product yield penalty or other substantial dis advantage.
• the chemical treatment is carried out according to this invention by contacting cobalt-rare earth magnetic material with a suitable acid solution, the material in powder form preferably being immersed in the acid solution for the required period of contact time and then promptly removed and rinsed free from that solution in order to arrest the acid attack.
• Time and temperature are interrelated factors in this method, I have found, however, that practical operating ranges of these variables are so broad that the necessity for precise control of the method can readily be avoided. Thus, except for threshold or marginal conditions of time and temperature, the operating conditions or a combination of these conditions is not critical to the success or failure of the method in terms of the products obtained.
• the acid mixture will be at rooom temperature but it may be at any temperature at which the acid mixture is a liquid.
• the period of immersion or contact may likewise be anywhere from one or two seconds to 30 minutes, my present preference being about 30 seconds. Prolonged acid contact may lead to significantly diminishing magnet material yields, particularly if the treating solution temperature is substantially above room temperature.
• the mechanical or manipulative limitation which generally is the important one. Acid solutions I prefer for this process act rapidly enough that momentary contact is sufficient to insure consistently good results and it remains only to device means enabling immersion and removal of the powder materials at the rate desired in a batchwise or a continuous chemical treatment operation. In any event a second or two would appear to be a reasonable immersion contact period and five to 10 seconds would be an easier goal to reach in production operations.
• cobalt-rare earth magnet material of particle size in the range between 250 mesh and +325 mesh (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 particle size is generally inversely proportional to coercive force.
• 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.
• Acid A Three parts nitric acid One part sulfuric acid One part orthophosphoric acid Five parts glacial acetic acid One part nitric acid One part sulfuric acid One part orthophosphoric acid Five parts glacial acetic acid 200 grams chromic oxide grams nitric acid 10 grams sodium sulfate Water to one liter volume. 4 Microns.
• Co Y was prepared by arc-melting cobalt and yttrium together under an argon atmosphere and then casting the melt to form an ingot.
• a piece of the resulting very brittle ingot weighing about one half gram was ground with mortar and pestle and the resulting powder was screened and the fraction passing a 250 mesh screen and return on a 325 mesh screen was selected for test.
• the remainder of the -250 +325 mesh powder fraction was placed in a dish with ml. of a mixture of 3 parts nitric acid, one part sulfuric acid, one part orthophosphoric acid and five parts glacial acetic acid.
• the acid mixture was at C., and the powder was permitted to remain in the acid mixture for seconds whereupon the powder was removed from the acid mixture and rinsed with water and with acetone and permitted to dry in air.
• This sample was then mounted inparaffin and tested as described above with the result that the coercive force was found to be 3340 oersteds, as stated in the third entry of Table I.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Power Engineering (AREA)
• Hard Magnetic Materials (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=24818894

Family Applications (1)

Country Status (7)

Cited By (7)

• 1968
  • 1968-01-31 US US701840*A patent/US3558372A/en not_active Expired - Lifetime
  • 1968-12-31 BE BE726341D patent/BE726341A/xx unknown
• 1969
  • 1969-01-03 GB GB579/69A patent/GB1210332A/en not_active Expired
  • 1969-01-10 DE DE19691901056 patent/DE1901056A1/de active Pending
  • 1969-01-15 NL NL6900668A patent/NL6900668A/xx unknown
  • 1969-01-16 ES ES362575A patent/ES362575A1/es not_active Expired
  • 1969-01-30 FR FR6901903A patent/FR2001038A1/fr not_active Withdrawn

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