US3655464A - Process of preparing a liquid sintered cobalt-rare earth intermetallic product - Google Patents

Process of preparing a liquid sintered cobalt-rare earth intermetallic product Download PDF

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US3655464A
US3655464A US33347A US3655464DA US3655464A US 3655464 A US3655464 A US 3655464A US 33347 A US33347 A US 33347A US 3655464D A US3655464D A US 3655464DA US 3655464 A US3655464 A US 3655464A
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rare earth
cobalt
percent
alloy
sintered
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Mark G Benz
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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
    • H01F1/047—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
    • 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

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  • a A particulate mixture is formed of a base CoR alloy and an additive CoR alloy, where R is a rare earth metal.
  • the base CoR alloy is one which, at sinten'ng temperature, exists as a solid Co R intermetallic single phase.
  • the additive CoR alloy is richer in rare earth metal than the base CoR alloy, and at sintering temperature is at least partly liquid.
  • the base and additive alloys, in particulate form are each used in an amount to form a mixture which has a cobalt and rare earth metal content substantially corresponding to that of the final desired sintered product. The mixture is pressed into compacts and sintered to the desired sintered product phase composition and density.
  • the final sintered product has a phase composition lying outside the Co R single phase on the rare earth richer side.
  • the final sintered product contains a major amount of the Co -,R single phase on the solid intermetallic phase and up to about 35 percent by weight of the product of a second solid CoR intermetallic phase which is richer in rare earth content than the Co R phase.
  • the present invention relates generally to the art of permanent magnets and is more particularly concerned with novel sintered cobalt-rare earth intermetallic products having unique characteristics and with a sintering method for producing such products.
  • Cobalt-rare earth intermetallic compounds exist in a variety of phases, but the Co R intermetallic single phase compounds (in each occurrence R designates a rare earth metal) have exhibited the best magnetic properties.
  • FIG. 1 is the cobalt-samarium phase diagram. It is assumed herein, that the phase diagram at 300 C., which is the lowest temperature shown in the figure, is substantially the same at room temperatures.
  • FIG. 2 in chart bearing curves which illustrate the effect of samarium content on the magnetic properties of permanent magnets including two produced in accordance with the present invention.
  • the process of the present invention comprises the steps of forming a particulate mixture of a base cobalt-rare earth alloy and an additive cobalt-rare earth alloy,
  • the base alloy is one which at sintering temperature exists as a solid Co R intermetallic single phase where R is a rare earth metal.
  • the additive cobalt-rare earth alloy is richer in rare earth metal than the base alloy and at sintering temperature it is at least partly in liquid form and thus increases the sintering rate.
  • the base and additive alloys, in particulate form, are each used in an amount to form a mixture which has a cobalt and rare earth metal content substantially corresponding to that of the final desired sintered product.
  • the mixture is pressed into compacts, preferably in an aligning magnetic field, and sintered to the desired sintered product phase composition and desired density.
  • the final sintered product has a composition lying outside the Co R single phase region on the rare earthrich side.
  • the final sintered product contains a major amount of the Co R solid intermetallic phase and up to about 35 percent by weight of the product of a second CoR intermetallic phase which is richer in rare earth content than Co R phase.
  • the base cobalt-rare earth alloy used in the present process is one which at sintering temperature exists as a Co R single intermetallic phase. Since the Co R single phase may vary in composition, the base alloy may vary in composition which can be determined from the phase diagram for the particular cobalt-rare earth system, or empirically. For example, FIG. 1 shows that for the cobalt-samarium system, the base alloy at room temperature may vary in samarium content from about 32 to 36 percent by weight since this particular composition is single phase at sintering temperatures ranging from about 950 to 1,200 C. Preferably, for simplicity, the base alloy at room temperature is a Co R intermetallic phase.
  • the additive cobalt-rare earth alloy is one which is richer in rare earth metal content than the base alloy. It must also be one that exists at least partly in a liquid form at sintering temperature.
  • the additive alloy may vary in composition and can be determined from the phase diagram for the particular cobalt-rare earth system or it can be determined empirically.
  • FIG. 1 shows that for the cobalt-samarium system, there are phases which are partly or completely liquid at the temperature ranging from about 950 to 1,200 C. which is a suitable sintering temperature range for Co-Sm in the present process. Any alloy within the range shown in FIG. 1 which forms at least a partly liquid phase at the particular sintering temperature would be a satisfactory additive alloy in the present process. For example, as illustrated in FIG.
  • the Co-Sm additive alloy can vary upward in samarium content from which 46 percent by weight of the additive.
  • an additive alloy can be empirically selected by a number of methods, such as by means of a composition scan at the sintering temperature, i.e., heating samples of various additive alloy compositions to the desired sintering temperature and observing the extent of the development of the liquid phase.
  • suitable additive CoR alloys fall within a general composition range, the preferred ones are comparatively low in rare earth metal content so that undesirable characteristics of the pure rare earth metal in the additive alloy are minimized.
  • pure samarium is both pyrophoric and very ductile and consequently difficult to crush and to blend with the base alloy since it has a tendency to separate out and fall to the bottom of the container.
  • the additive CoSm alloy of samarium content preferably less than 70 percent by weight, is substantially nonreactive at room temperature in air, it can be crushed by conventional techniques, and being slightly magnetic, it clings to the base alloy resulting in a substantially thorough stable mixture.
  • the additive alloy becomes more reactive and more difficult to blend.
  • the higher the cobalt content of the additive alloy the stronger are its magnetic properties and the more stable is the particulate mixture it forms with the base alloy.
  • the rare earth metals useful in forming the present cobaltrare earth alloys and intermetallic compounds are the 15 elements of the lanthanide series having atomic numbers 57 to 71 inclusive.
  • the element yttrium (atomic number 39) is commonly included in this group of metals and, in this specification, is considered a rare earth metal.
  • a plurality of rare earth metals can also be used to form the present desired cobalt-rare earth alloys or intermetallic compounds which, for example may be ternary, quartenary or which may contain an even greater number of rare earth metals as desired.
  • cobalt-rare earth alloys useful as base and additive alloys in the present invention are cobalt-cerium, cobalt-praseodymium, cobalt-neodymium, cobalt-promethium, cobalt-samarium, cobalt-europium, cobalt-gadolinium, cobalt-terbium, cobalt-dysprosium, cobalt-holmium, cobalterbium, cobalt-thulium, cobalt-ytterbium, cobalt-lutecium, cobalt-yttrium, cobalt-lanthanum and cobalt-misch metal.
  • Misch metal is the most common alloy of the rare earth metals which contains the metals in the approximate ratio in which they occur in their most common naturally occurring ores.
  • specific ternary alloys include cobalt-samariummisch metal, cobalt-cerium-praseodymium, cobalt-yttriumpraseodymium, and cobalt-praseodymium-misch metal.
  • the solid base and additive alloys can be converted to particulate form in a conventional manner. Such conversion can be carried out in air at room temperature since the alloys are substantially non-reactive. For example, each alloy can be crushed by mortar and pestle and then pulverized to a finer form by jet milling.
  • the particle size of the base and additive cobalt-rare earth alloys used in forming the mixture of the present process may vary. Each can be in as finely divided a form as desired. For most applications, average particle size will range from about 1 micron or less to about microns. Larger sized particles can be used, but as the particle size is increased, the maximum coercive force obtainable is lower because the coercive force generally varies inversely with particle size. In addition, the smaller the particle size, the lower is the sintering temperature which may be used.
  • the base and additive alloys are each used in an amount so that the resulting mixture has a cobalt and rare earth metal content substantially corresponding to that of the final desired sintered product phase composition.
  • the alloy additive should be used in an amount sufficient to promote sintering. This amount depends largely on the specific composition of the alloy additive and can be determined empirically, but generally, the additive alloy should be used in an amount of at least 0.5 percent by weight of the base-additive alloy mixture. Specifically, the larger the rare earth metal component of the additive alloy, the less is the amount of the additive alloy which need be used.
  • the final sintered product at sintering temperature, should have a phase composition lying outside the Co R single phase on the rare earth-rich side. Magnetization of such a product results in a permanent magnet with superior magnetic properties.
  • a final sintered product at sintering or room temperatures consists only of a single Co R intermetallic phase, or if it contains a second cobalt-rare earth intermetallic phase of lesser rare earth content than the Co R phase, a permanent magnet of only inferior magnetic properties can be produced no matter how the magnetization step is carried out.
  • the final sintered product contains a major amount of the Co R solid intermetallic phase, generally at least about 65 percent by weight of the product, and up to about 35 percent by weight of the product of a second solid CoR intermetallic phase which is richer in rare earth metal content than the Co R phase. Traces of other cobalt-rare earth intermetallic phases, in most instances less than one percent by weight of the product, may also be present.
  • Sintered products having the highest energy products are those having the smallest content of the second CoR phase.
  • the preferred final sintered product is comprised predominantly of the Co R intermetallic phase, i.e., about 95 percent by weight or higher but less than 100 percent, with only a detectable content of the second CoR phase, i.e., 5 percent or lower by weight of the product.
  • a composition scan i.e., a series of runs at the same sintering temperature with proportionately varying mixtures of base and additive alloys, may be made to determine the specific sintered product composition which produces the best magnetic properties.
  • Determination of the second CoR phase can be made by a number of techniques, such as for example, X-ray diffraction as well as standard metallographic analysis.
  • the base alloy is admixed with the additive alloy in any suitable manner to produce a substantially thorough particulate mixture.
  • the particulate mixture can then be compressed into a green body of the desired size and density by any of a number of techniques such as hydrostatic pressing or methods employing steel dies.
  • the mixture is compressed in the presence of an aligning magnetizing field to magnetically align the particles along their easy axis, or if desired, the mixture may be compressed after magnetically aligning the particles.
  • the greater the magnetic alignment of the particles the better are the resulting magnetic properties.
  • compression is carried out to produce a green body with as high a density as possible, since the higher its density, the greater the sintering rate. Green bodies having a density of about 40 percent or higher of theoretical are preferred.
  • the green body is sintered to produce a sintered body of desired density.
  • the green body is sintered to produce a sintered body wherein the pores are substantially non-interconnecting.
  • Such non-interconnectivity stabilizes the permanent magnet properties of the product because the interior of the sintered product or magnet is protected against exposure to the ambient atmosphere.
  • the sintering temperature used in the present process depends largely on the particular cobalt-rare earth mixture to be sintered, and to a lesser degree, on particle size.
  • the minimum sintering temperature must be sufficiently high for sintering to occur in a particular cobalt-rare earth system, i.e., it must be high enough to coalesce the component particles.
  • sintering is carried out so that the pores in the sintered product are substantially non-interconnecting.
  • a sintered body having a density or packing of at least about 87 percent of theoretical is generally one wherein the pores are substantially non-interconnecting.
  • Such non-interconnectivity is determinable by standard metallographic techniques, as for example, by means of transmission electron micrographs of a cross-section of the sintered product.
  • the maximum sintering temperature is preferably one at which significant growth of the component particles or grains does not occur, since too large an increase in grain size deteriorates magnetic properties such as coercive force.
  • the green body is sintered in a substantially inert atmosphere such as argon, and upon completion of the sintering, it is preferably cooled to room temperatures in a substantially inert atmosphere.
  • the density of the sintered product may vary. The particular density depends largely on the particular permanent magnet properties desired. Preferably, to obtain a product with substantially stable permanent magnet properties, the density of the sintered product should be one wherein the pores are substantially non-interconnecting and this occurs usually at a density or packing of about 87 percent. Generally, for a number of applications, the density may range from about percent to percent. For example, for low temperature applications, a sintered body having a density ranging down to about 80 percent may be satisfactory. The preferred density of the sintered product is one which is the highest obtainable without producing a growth in grain size which would deteriorate magnetic properties significantly, since the higher the density the better are the magnetic properties.
  • a density of at least about 87 percent of theoretical, i.e., of full density, and as high as about 96 percent of theoretical is preferred to produce permanent magnets with suitable magnetic properties which are substantially stable.
  • the sintered product of the present invention has the appearance of having been liquid sintered. Examination of a polished cross-section of the sintered bulk product under an X-ray microprobe or light microscope shows that its grains differ significantly in appearance from the original particles used in forming the green body. Specifically, the original particles have an angular rough surface structure. In contrast, substantially all of the grains of the present sintered product are rounded and have a smooth surface, i.e., the appearance is that of a liquid-sintered-smooth surface. In addition, under a light microscope as well as under an X-ray microprobe, there can be seen a material in a number of the pores that appears to have been liquid at high temperatures. Apparently, during sintering, some of the liquid becomes trapped in closing the pores. The pores of the sintered product are preferably substantially non-interconnecting. Generally, for the sintered product to have good magnetic properties, the component grains of the bulk product should preferably not have an average size larger than about 30 microns.
  • the sintered product of the present invention is useful as a permanent magnet. Its permanent magnet properties can be significantly enhanced, however, by subjecting it to a magnetizing field.
  • the resulting permanent magnet is substantially stable in air and has a wide variety of uses.
  • the permanent magnets of the present invention are useful in telephones, electric clocks, radios, television, and phonographs. They are also useful in portable appliances, such as electric toothbrushes and electric knives, and to operate automobile accessories.
  • the present permanent magnets can be used in such diverse applications as meters and instruments, magnetic separators, computers and microwave devices.
  • the sintered bulk product of the present invention can be crushed to a desired particle size preferably a powder, which is particularly suitable for alignment and matrix bonding to give a stable permanent magnet.
  • the matrix material may vary widely and may be plastic, rubber or metal such as, for example, lead, tin, zinc, copper or aluminum.
  • the powdercontaining matrix can be cast, pressed or extruded to form the desired permanent magnet.
  • the aligning magnetizing field was used to magnetically align along the easy axis.
  • the sintering furnace was a ceramic tube.
  • All sintering was carried out in an inert atmosphere of purified argon and upon completion of the sintering, the sintered product was cooled in the same purified argon atmosphere.
  • Particle size was determined by a standard metallographic method.
  • the density of the green body as well as the sintered product is given as packing. Packing is the relative density of the material, i.e., it is a percent of theoretical. Packing was determined by a standard method using the following equatron:
  • Weight Volume X 100: percent packing EXAMPLE 1 A base alloy melt and an additive alloy melt of cobaltsamarium were made under purified argon by arc-melting and cast into ingots. The base alloy was formed from 33.3 weight percent samarium and 66.7 weight percent cobalt. The additive alloy was formed from 60 weight percent samarium and 40 weight percentcobalt. Each ingot was initially crushed by means of mortar and pestle and then reduced by fluid energy jet milling to a powder ranging in size from approximately 1 to 10 microns in diameter and generally had an average particle size of about 6 microns.
  • the samples for Run Nos. 1 through 10 were taken from 12 gram mixtures formed by admixing 10 grams of the base alloy powder with 2.14 gram of the additive alloy powder by tumbling to form a substantially thorough mixture composed of 62 weight percent cobalt and 38 weight percent samarium. Since the additive alloy was substantially non-reactive in air and was slightly magnetic, a stable mixture of the two powders was produced. Wet chemical analysis of portions of the mixture showed 37.4 t 0.3 percent Sm. Portions of the mixture were then compressed into green bodies which were sintered and their magnetic properties determined.
  • Table l tabulates the specific procedure used for each run made. Specifically, in Runs 1 through 10 a portion of the mixture was weighed and then compressed into a circular disc. Compression was carried out in a steel die in an aligning magnetizing field ranging from 7 to 15 kilo-oersteds provided by an iron electromagnet. Each disc was then sintered and its properties determined after sintering. After magnetization at room temperatures in a field of 25 kilo-oersteds, the magnetic properties of the disc were determined.
  • Runs 11 through 16 the procedure was substantially the same as in Runs 1 through 10 except that the sample for each run was taken from a master batch formed of 173 grams of the base alloy and 37 grams of the additive alloy to give a mixture composed of 62 weight percent cobalt and 38 weight percent samarium.
  • each sample was placed in a rubber tube and magnetically aligned therein.
  • the aligning magnetizing field was provided by an electromagnet and ranged from 7 to 15 kilooersteds.
  • the aligning magnetizing field was provided by a superconducting coil which in Runs 14 and 15 was kilo-oersteds and in Run 16 was 60 kilo-oersteds.
  • the tube was evacuated to freeze the alignment and then it was pressed hydrostatically to form the green body.
  • the tabulated sintering temperature of 1,050 or 1,100 C. is one at which the additive is in a partly liquid phase.
  • Table I shows that sintering of the green body produces a sintered product which weighs about the same as the green body indicating no loss in the cobalt and samarium components. However, the green body does undergo some shrinkage during sintering as illustrated by the packing of the sintered product which was significantly higher in every run than that of the green body. In Runs 1 through 10 the energy product was estimated due to the geometric limitations of the product.
  • Runs Nos. 1 through 16 specifically illustrate the significantly better magnetic properties obtained by present process as compared to Run No. 17, the control, where no additive alloy of the present invention was used.
  • the intrinsic coercive force of the sintered cobalt-rare earth powder was measured at room temperature in the same manner. Specifically, a specimen of the powder was prepared for magnetic measurement by introducing it into a body of molten paraffin wax in a small glass tube and cooling the wax in an aligning magnetic field of about 17,500 oersteds until the paraffin solidified. The intrinsic coercive force of each such prepared sample was then measured after magnetization in a field of 17,500 oersteds. The results are shown in Table 11.
  • Portions of the base alloy (66.7 percent by weight cobalt and 33.3 percent by weight samarium) powder and the additive alloy (40 percent by weight cobalt and 60 percent by weight samarium) powder disclosed in Example 1 were used to prepare the three mixtures of this example. Specifically, for Run No. 21, 13.12 grams of the base alloy were admixed with 0.88 grams of the additive alloy to form a mixture composed of 65 percent by weight cobalt and 35 percent by weight samarium. For Run No. 22, 12.08 grams of the base alloy were admixed with 1.92 grams of the additive alloy to form a mixture composed of 63 percent by weight cobalt and 37 percent by weight samarium. For Run No.
  • the abscissa of the graph is the magnetic field (H) in kilo-oersteds and the ordinate is magnetization 417M in kilogauss.
  • H magnetic field
  • the ordinate magnetization 417M in kilogauss.
  • FIG. 2 shows poor magnetic properties for the sintered product of Run No. 21 composed of 65 percent cobalt and 35 percent by weight samarium which according to FIG. 1 is the composition for a single intermetallic phase. Microscopic analysis of the product of Run No. 21 showed it to be a single phase.
  • EXAMPLE 4 In this example, the procedure and materials used were substantially the same as that set forth in Example 1 for preparing the compressed disc of Run No. l and a number of sintering runs were carried out in substantially the same manner as Run No. l of Example 1.
  • EXAMPLE 5 In this example, a permanent magnet was formed comprised of the sintered powder of the present invention distributed in a metal matrix.
  • the sintered powder of Run No. 18 of Example 2 was initially demagnetized by heating it to a temperature of 900 C. for minutes. The demagnetized powder was then mixed with a l00 mesh (U.S. Standard Screen Size) aluminum powder to produce a mixture of 80 volume percent of the sintered powder and 20 volume percent of the aluminum powder.
  • a l00 mesh U.S. Standard Screen Size
  • a slurry of the mixture was made with isopropyl alcohol and placed in a die press in an aligning magnetizing field of kilooersteds and pressed under a pressure of 200 K psi.
  • the resulting compressed body had a diameter of 0.336 inch and a length of 0.351 inch. After it was magnetized in a field of 15 kilo-oersteds, the resulting magnet had an open circuit induction B of 2395 gauss.
  • EXAMPLE 6 A base alloy melt and an additive alloy melt were formed under purified argon by arc-melting and were cast into ingots.
  • the base alloy was formed from 68 weight percent cobalt, 16 weight percent samarium and 16 weight percent cerium-misch metal.
  • the additive alloy was formed from 40.8 weight percent cobalt and 59.2 weight percent samarium.
  • Each ingot was formed into a powder in the same manner as disclosed as in Example 1 ranging in size from approximately 1 to about 10 microns in diameter with an average particle size of about 6 microns.
  • the sintered bar was magnetized in a field of 16.5 kilooersteds, it had an intrinsic coercive force ,,,H, of 4,600 oersteds and an open circuit induction B of 6160 gauss in a self-demagnetizing field of 300 oersteds.
  • a process for producing a sintered cobalt-rare earth intermetallic product containing a Co R intermetallic phase and a CoR intermetallic phase which is richer in rare earth metal content than said Co R intermetallic phase which comprises providing a particulate mixture of a base cobalt-rare earth metal alloy and an additive cobalt-rare earth metal alloy, said base alloy existing at sintering temperature as a solid Co R intermetallic phase and said additive CoR alloy existing at sintering temperature as at least a partly liquid phase, said base alloy and said additive alloy each being used to form a mixture which has a cobalt and rare earth metal content substantially corresponding to that of the final sintered product with said additive CoR alloy being present in an amount of at least 0.5 percent by weight of said mixture, pressing said mixture into a green body, and sintering said green body in a substantially inert atmosphere to produce a sintered product having a density of at least about 80 percent of theoretical and containing the Co R intermetallic phase in an amount of at least 65 percent
  • said base cobaltrare earth alloy is a cobalt-samarium-cerium mischmetal alloy.
  • a process according to claim 1 wherein the particle size of said particulate mixture ranges from about 1 to 10 microns.
  • a process according to claim 1 WhlCh includes the steps of crushing said sintered product into particles, and bonding the resulting particles of sintered product to a matrix material.
  • a process according to claim 1 which includes the step of subjecting said sintered product to a magnetizing field to produce a magnetized sintered product.
  • a process according to claim 14 which includes the step of subjecting said bonded particles in said matrix material to a magnetizing field to magnetize said particles.

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US3887395A (en) * 1974-01-07 1975-06-03 Gen Electric Cobalt-rare earth magnets comprising sintered products bonded with cobalt-rare earth bonding agents
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US3905839A (en) * 1971-12-17 1975-09-16 Gen Electric Liquid sintered cobalt-rare earth intermetallic product
US3909647A (en) * 1973-06-22 1975-09-30 Bendix Corp Rotor assembly for permanent magnet generator
US3919004A (en) * 1970-04-30 1975-11-11 Gen Electric Liquid sintered cobalt-rare earth intermetallic product
US3933535A (en) * 1974-01-28 1976-01-20 General Electric Company Method for producing large and/or complex permanent magnet structures
US3979619A (en) * 1973-09-24 1976-09-07 Canadian General Electric Co. Ltd. Permanent magnet field structure for dynamoelectric machines
US4092184A (en) * 1975-10-08 1978-05-30 General Electric Company Method of preparing and installing cobalt-rare earth permanent magnets
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RU2136068C1 (ru) * 1998-06-18 1999-08-27 Савич Александр Николаевич Магнитный материал для постоянных магнитов и способ его изготовления
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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3919004A (en) * 1970-04-30 1975-11-11 Gen Electric Liquid sintered cobalt-rare earth intermetallic product
US3892603A (en) * 1971-09-01 1975-07-01 Raytheon Co Method of making magnets
US3905839A (en) * 1971-12-17 1975-09-16 Gen Electric Liquid sintered cobalt-rare earth intermetallic product
DE2326960A1 (de) * 1972-06-22 1974-01-10 Gen Electric Wandler
US3909647A (en) * 1973-06-22 1975-09-30 Bendix Corp Rotor assembly for permanent magnet generator
US3979619A (en) * 1973-09-24 1976-09-07 Canadian General Electric Co. Ltd. Permanent magnet field structure for dynamoelectric machines
US3887395A (en) * 1974-01-07 1975-06-03 Gen Electric Cobalt-rare earth magnets comprising sintered products bonded with cobalt-rare earth bonding agents
US3933535A (en) * 1974-01-28 1976-01-20 General Electric Company Method for producing large and/or complex permanent magnet structures
JPS50111599A (https=) * 1974-02-04 1975-09-02
US4092184A (en) * 1975-10-08 1978-05-30 General Electric Company Method of preparing and installing cobalt-rare earth permanent magnets
US4857118A (en) * 1986-10-13 1989-08-15 U.S. Philips Corporation Method of manufacturing a permanent magnet
RU2136068C1 (ru) * 1998-06-18 1999-08-27 Савич Александр Николаевич Магнитный материал для постоянных магнитов и способ его изготовления
US6696015B2 (en) * 1999-03-03 2004-02-24 Sumitomo Special Metals Co., Ltd. Method for producing rare-earth magnet

Also Published As

Publication number Publication date
GB1343536A (en) 1974-01-10
DE2121514A1 (de) 1971-11-18
CA929383A (en) 1973-07-03
NL174571C (nl) 1984-07-02
NL7105959A (https=) 1971-11-02
JPS5230451B1 (https=) 1977-08-08
NL174571B (nl) 1984-02-01
DE2121514B2 (de) 1980-12-04

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