US3501358A - Method of making permanent magnet material powders having superior magnetic characteristics - Google Patents

Method of making permanent magnet material powders having superior magnetic characteristics Download PDF

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Publication number
US3501358A
US3501358A US664295A US3501358DA US3501358A US 3501358 A US3501358 A US 3501358A US 664295 A US664295 A US 664295A US 3501358D A US3501358D A US 3501358DA US 3501358 A US3501358 A US 3501358A
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Prior art keywords
powder
permanent magnet
magnet material
bulk
thiourea
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US664295A
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English (en)
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Joseph J Becker
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General Electric Co
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General Electric Co
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    • 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

Definitions

  • the present invention relates generally to the art of making permanet magnets and is more particularly concerned with new magnetic material powders having unique characteristics and with a novel method of producing these powders.
  • this operation or method of this invention centers in the key step of contacting bulk permanent magnet material with an aqueous mineral acid solution containing an organic compound corrosion inhibitor. Contact is relatively brief, as from 30 seconds to 30 minutes, and does not result in the dissolution of any significant amound of the bulk material, but the beneficial effect of a grinding step is obtained in that the bulk magnetic material is reduced to fine particle size. 7.
  • This invention method thus is predicated upon my surprising discovery that under certain circumstances a brief chemical treatment can take the place of a grinding step or even a series of heavy grinding steps in reducing bulk permanent magnet material to fine powder form. It is also based upon my discovery that there are a number of alternative treating solutions which can be used for this purpose with uniformly good results and without any penalty of reduced yield of magnet material or other substantial disadvantage.
  • the chemical treatment is carried out in accordance with this invention by contacting the bulk magnet material with a solution of hydrochloric acid, sulfuric acid or nitric acid diluted with water to intermediate or lower strength.
  • the magnet material is in the form of a coarse powder and is immersed in the acid solution and thereafter rinsed free of the solution.
  • the solution content has as an essential ingredient a small amount of an organic corrosion-inhibitor such as thiourea, p-thiocresol or benzaldehyde.
  • Time, temperature, acid concentration and particle size of the permanent magnet material to be treated are interrelated factors in this method. I have found, however, that the practical operating ranges of these variables are so broad that the necessity for precise control of the method can readily be avoided. Except for threshold conditions of time, temperature, concentration and bulk material size, none of the operating conditions or combination of these conditions is highly critical, making the difference between operability and inoperability. Rather, there is a practical range of each variable in relation to the others which lies between the somewhat arbitrary limits of the economies of the method of this invention. This bulk material in the form of coarse powder is more rapidly and efliciently treated to produce a given amount of desired fine particle powder product than bulk material in the form of somewhat larger pieces can be, assuming the other conditions of the operation are the same.
  • the process is accelerated by increasing the temperature of the treating solution and the yield of desired product is increased within limits by prolonging the treatment period.
  • Acid concentration exerts only a small influence on the product quality so far as has been observed as long as acid is present in an amount from 0.25 percent to 20 percent.
  • the treating solution during use will be about room temperature, although it can be any temperature at which the solution exists in the liquid state so that the bulk magnet material may be immersed in it for the required time of treatment.
  • the period of immersion may likewise be varied from a minimum of 30 seconds to 30 minutes or more with my preference being from one toten minutes. Longer times may lead to diminishing product yields, particularly if the treating solution temperature is in the range approaching the solution boiling point temperature. On the other hand, periods shorter than 30 seconds are not sufiicient for the production of good product yields even when solution temperature is high and the bulk material is a coarse powder.
  • the bulk magnet material to be treated by this new method be of particle size less than microns and suitably less than 25 microns.
  • permanent magnet materials can be ground to such sizes without significantly impairing the desired properties of the powder product ultimately obtained by subjecting these ground materials to the present invention method.
  • thioeresol 635 5% H2SO4+.1% tlnourea. l0 2, 800 402 10% HNOa+-2% thiourea. 5 1, 500
  • the powder products set out in Table I are new in the art in that the several cobalt-base permanent magnet materials have never before existed in the form of powders having the combination of magnetic properties, and especially the very high coercive forces, possessed by these novel products. They are also new in that they have X- ray diffraction patterns which in respect to line width are essentially identical to those of the bulk or unground starting material from which they are obtained. These materials owe these unique properties to the novel method of their production which also serves to characterize and distinguish them from permanent magnet material powders of the prior art.
  • Co Y was prepared by arc-melting together the ele- /2 gram was ground with a mortar and pestle for a few seconds. The resulting powder was washed with water through a coarse fritted glass filter, using suction, yielding several milligrams of 25 micron powder. This was rinsed with acetone and allowed to dry. A portion of it was removed for magnetic testing. This portion was mounted in a glass sample holder in molten parafiin. A magnetic field of about 1000 oersteds was applied as the paraffin solidified. The sample holder was then placed in a vibrating-sample magnetometer.
  • the coercive force measured in this instrument after applying a magnetizing field of 21,000 oersteds was 660 oersteds.
  • the rest of the sample was placed in a dish with 10 ml. of a solution of 20% HCl-,
  • the coercive force was 6750 oersteds.
  • Example II The experiment of Example I was repeated with induction-melted Co Sm being substituted for Co Y. All the conditions and operations were as stated in Example I except that the powder particles were in contact with the acid solution for only two minutes. The coercive force of the resulting powder product was measured to be 6850 oersteds, as reported in Table I.
  • EXAMPLE III A product nominally C0 Ce was prepared by arc-melting together cobalt and cerium-rich misch metal in a protective atmosphere of argon. Following the procedure stated in Example I except that the acid solution contact period was limited to one minute, a powder product was obtained which had a coercive force of 2000 oersteds, as reported in Table 1.
  • Example v Another experiment like that of Example IV was performed to test the eifect of an aqueous 5% HCl treating solution containing 0.4% thiourea. Thus, all other conditions were as stated in Example IV.
  • the ultimate powder product had a coercive force of 1-690 oersteds.
  • EXAMPLE VI Still another experiment to test the elfect of varying the acid concentration in the aqueous treating solution was performed using Co Ce produced and prepared as a 20 micron powder as set forth in Examples IV and V. In this instance, however, the aqueous treating solution had an HCl content of 1.0% and a thiourea content of 0.4%. With all other conditions being the same as those stated in Examples IV and V, a final product powder was obtained which was measured to have a coercive force of 1750 oersteds.
  • the bulk magnet material is Co Y in the form of coarse minus 25 micron powder and the contacting step consists in submerging the Co Y bulk material in a 5 percent H solution containing 0.1 percent thiourea.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Hard Magnetic Materials (AREA)
US664295A 1967-08-30 1967-08-30 Method of making permanent magnet material powders having superior magnetic characteristics Expired - Lifetime US3501358A (en)

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US66429567A 1967-08-30 1967-08-30

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US (1) US3501358A (enrdf_load_stackoverflow)
DE (1) DE1758807A1 (enrdf_load_stackoverflow)
FR (1) FR1597498A (enrdf_load_stackoverflow)
GB (1) GB1188059A (enrdf_load_stackoverflow)
NL (1) NL6812333A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3652343A (en) * 1970-09-14 1972-03-28 Gen Electric Permanent magnet material powders having superior magnetic characteristics
DE2326960A1 (de) * 1972-06-22 1974-01-10 Gen Electric Wandler
US3790414A (en) * 1967-11-15 1974-02-05 Matsushita Electric Ind Co Ltd As-CAST, RARE-EARTH-Co-Cu PERMANENT MAGNET MATERIAL
CN108526489A (zh) * 2018-05-08 2018-09-14 重庆科技学院 溶胶-凝胶法制备Sm-Co纳米颗粒的方法及产品

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2336901C2 (de) * 1973-07-20 1982-06-09 Magnetfabrik Bonn Gmbh Vorm. Gewerkschaft Windhorst, 5300 Bonn Verfahren zum Herstellen von Dauermagneten und Ätzmittel zum Druchführen des Verfahrens

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3424578A (en) * 1967-06-05 1969-01-28 Us Air Force Method of producing permanent magnets of rare earth metals containing co,or mixtures of co,fe and mn

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3424578A (en) * 1967-06-05 1969-01-28 Us Air Force Method of producing permanent magnets of rare earth metals containing co,or mixtures of co,fe and mn

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3790414A (en) * 1967-11-15 1974-02-05 Matsushita Electric Ind Co Ltd As-CAST, RARE-EARTH-Co-Cu PERMANENT MAGNET MATERIAL
US3652343A (en) * 1970-09-14 1972-03-28 Gen Electric Permanent magnet material powders having superior magnetic characteristics
DE2326960A1 (de) * 1972-06-22 1974-01-10 Gen Electric Wandler
CN108526489A (zh) * 2018-05-08 2018-09-14 重庆科技学院 溶胶-凝胶法制备Sm-Co纳米颗粒的方法及产品

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Publication number Publication date
FR1597498A (enrdf_load_stackoverflow) 1970-06-29
NL6812333A (enrdf_load_stackoverflow) 1969-03-04
DE1758807A1 (de) 1971-02-25
GB1188059A (en) 1970-04-15

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