US3873379A - Method of producing rare earth-cobalt permanent magnet using special cooling rates - Google Patents

Method of producing rare earth-cobalt permanent magnet using special cooling rates Download PDF

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Publication number
US3873379A
US3873379A US377919A US37791973A US3873379A US 3873379 A US3873379 A US 3873379A US 377919 A US377919 A US 377919A US 37791973 A US37791973 A US 37791973A US 3873379 A US3873379 A US 3873379A
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temperature
rate
permanent magnet
cooled
sintered body
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Expired - Lifetime
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US377919A
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English (en)
Inventor
Kazuo Yamakawa
Tohru Oka
Masaaki Tokunaga
Takeshi Mizuhara
Chitoshi Hagi
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Proterial Ltd
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Hitachi Metals Ltd
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    • 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
    • B22F3/12—Both compacting and sintering
    • 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

Definitions

  • ABSTRACT A method of producing a rare earth-cobalt permanent magnet having high coercive force wherein powdery alloy containing rare earth elements and cobalt as principal component is compacted in magnetic field, the resulting green body is sintered at the temperature between l,OO0 to 1,200C, the sintered body is cooled from the above sintering temperature to quenching temperature in the range of 875i50C at a rate of 7C/min. or slower rate, and then further cooled successively from the quenching temperatures to room temperature at a rate of 20C/min. or faster rate.
  • FIG. 2 COOLING VELOCITY (C/min)
  • the present invention relates to a permanent magnet consisting of 'rare earth elements and cobalt.
  • Rare earth elements for the rare earth-cobalt permanent magnet of the present invention are selected from lanthanide series having atomic number 57 to 71, yttrium and scandium according to the required magnetic properties of the magnet.
  • the magnetic properties of the rare earthcobalt permanent magnet depend largely upon the preparation process thereof. At present, the following method consisting of the following steps is often used.
  • the final product shows the best magnetic properties, when the alloy is the mixture of intermetallic compounds as Co,-,R (R: rare earth elements) and Co-R intermetallic compounds containing richer rare earth elements than Co R does.
  • the above mentioned alloy contains 55-70 percent by weight of Co and 30-45 percent by weight of rare earth elements.
  • the alloy can contain slight amount of impurities and part of Co thereof can be replaced by Fe or Cu.
  • a permanent magnet has as high coercive force, residual induction and energy product as possible. It is well known that these magnetic properties depend largely upon preparation process thereof, above all on heat treatment process.
  • the object of the present invention is to provide a'method of producing a rare earth-cobalt permanent magnet having excellent magnetic properties without using aging process.
  • FIG. 1 shows the influence of the quenching temperature on the intrinsic coercive force ,I-I of cobaltsamarium alloy permanent magnet.
  • FIG. 2 shows the influence of the cooling rate from the sintering temperatures to the quenching temperatures on the intrinsic coercive force ,I-I of cobaltsamarium alloy permanent magnet.
  • FIG. 3 shows the influence of the cooling rate from the sintering temperatures to room temperature on the intrinsic coercive force H of cobalt-Samarium alloy permanent magnet.
  • the sintered body was cooled in a furnace from the sintering temperature to the quenching temperature of 900C at a rate of 6C/min. Then the sintered body was immediately and quickly cooled to room temperature by blasting it with argon gas at a rate of 200C/min.
  • the magnetic properties of the obtained sintered body of the present invention were determined.
  • the same powdery alloy as raw material was sintered under the same conditions, and then the sintered body was subjected to aging at 900C for 2 hours and cooled to room temperature at a rate of 200C/min in an argon atmosphere. This is the conventional method of producing rare earth-cobalt magnets.
  • the magnetic properties of the sintered body were determined. Table 1 shows the comparison between both determinations.
  • Br is residual magnetic flux density.
  • H normal coercive force found on B-H demagnetizing curve B: magnetic flux density, H: intensity of magnetic field
  • H intrinsic coercive force found on 4rrM-H demagnetizing curve (417M: intensity of magnetization)
  • Bl-U maximum energy product (Bl-U maximum energy product).
  • the permanent magnet according to the present invention is excellent, compared with the magnet produced by the conventional method.
  • EXAMPLE 2 The same mixed powdery alloy as in example 1 was sintered under the same conditions, and then the obtained sintered body was cooled from sintering temperature to various quenching temperatures at a rate of 6C/min. in a cooling rate controlled furnace. The sintered body thus cooled was immediately and quickly cooled successively from the quenching temperature to room temperature by blasting it with argon gas at the rate of about 200C/min.
  • FIG. 1 shows the influence of the quenching temperatures on the intrinsic coercive force H of the obtained sintered body.
  • the optimum quenching temperature is 875 50C.
  • Powdery alloy whose composition was Sm40%Co was added to powdery alloy whose composition was Sm-66.2%Co to obtain mixed powdery alloy whose composition was Sm63%Co.
  • the resulting mixed powdery alloy was ground by a vibration mill for 4 hours to an average particle diameter of 3.3 m.
  • the obtained fine powder was sintered by the same method and under the same conditions as that and those of the example 1. And then the sintered body was gradually cooled from the sintering temperature to quenching temperature of 900C at a rate of 0.8C/min. in a controlled furnace. The sintered body thus cooled was immediately and quickly cooled to room temperature.
  • the same powdery alloy was sintered under the same conditions as mentioned above and cooled to the quenching temperature of 900C at a rate of 16C/min.
  • the sintered body was cooled to the quenching temperature of 900C, it was immediately and quickly cooled to room temperature by blasting it with argon gas.
  • Table 2 shows comparison between the magnetic properties of the magnet of the present invention and those of the magnets made by the conventional method.
  • EXAMPLE 4 The same mixed powdery alloy as in the example 3 was sintered under the same conditions, and cooled from the sintering temperature to the quenching temperature of 900C at various cooling rates. When the sintered body was cooled to 900C, it was immediately and quickly cooled to room temperature at a rate of 200C/min.
  • the graph in F 16. 2 shows the influence of the cooling rates from the sintering temperature to the quenching temperature on the intrinsic coercive force ,H of the sintered body.
  • the preferable cooling rate of the sintered body is slower than 7C/min.
  • EXAMPLE 5 Powdery alloy whose composition was Sm40%Co was added to powdery alloy whose composition was Pr8.6% Sm-67.3%Co to obtain mixed powder alloy whose composition was Pr-16.7% Sm63%Co.
  • the resulting mixed powdery alloy was ground by a vibration mill for min. to an average particle diameter of 3.2 m.
  • the obtained fine powder was compressed to a green body by the same method as in example 1 and was sintered at l,l30C for 1 hour.
  • the sintered body was cooled from the sintering temperature to 900C in a furnace at a rate of 7C/min. After the sintered body was cooled to 900C, it was immediately and quickly cooled to room temperature at a rate of 200C/min.
  • the permanent magnet of the present invention has excellent magnetic properties, compared with the magnet produced by the conventional method.
  • Table 4 shows comparison between the magnetic properties of the magnet of the present invention and those a s of the magnet produced by the conventional method.
  • the magnet of the present invention has excellent magnetic properties, compared with the magnet produced by the conventional method.
  • EXAMPLE 7 Powdery alloy whose composition was Sm-40%Co was added to powdery alloy whose composition was Sm66.2%Co to obtain mixed powdery alloy whose composition was Sm-63%Co.
  • the resulting mixed powdery alloy was ground by a vibration mill for 4 hours to an average particle diameter of 3.3 m.
  • the obtained fine powder was compressed to a green body by the same way as that of the example 1.
  • the green body was sintered at l,l40C for 1 hour, and gradually cooled to 900C at a rate of 0.8C/min. When the sintered body was cooled to 900C, it was immediately cooled to room temperature at a rate of 100C/min. by oil quenching.
  • the same green body as mentioned above was sintered at 1,140C for 1 hour and cooled to 900C at a rate of 0.8C/min.
  • the sintered body was cooled to 900C, it was immediately cooled to room temperature at a rate of 4C/min. by furnace cooling.
  • Table 5 shows comparison between the magnetic properties of the magnet of the present invention and those of the magnet produced by the conventional method.
  • the magnet which was cooled at faster cooling rate of the present invention has excellent magnetic properties, compared with the magnet produced by the conventional method.
  • EXAMPLE 8 EXAMPLE 9 Alloy whose composition was Sm-63.8% was melted to obtain an ingot and the obtained ingot was preliminarily ground to prepare coarse powder.
  • the resulting coarse powdery alloy was ground by a vibration mill for 2% hours to an average particle diameter of 3.4 m.
  • the obtained fine powder was compressed to a green body by the same way as that of the example 1.
  • the green body was sintered at 1,1 10C for 1 hour, and cooled to 830C at a rate of 0.8C/min. When the sintered body was cooled to 830C, it was immediately cooled to room temperature at a rate of 200C/min.
  • the same powdery alloy was sintered under the same conditions and subjected to aging process at 900C for 14 hours. Table 6 shows comparison between the magnetic properties of the magnet of the present invention and those of magnet produced by the conventional method.
  • the magnet of the present invention has excellent magnetic properties.
  • EXAMPLE 10 1,000C/min. by blasting it with liquid carbonic acid gas.
  • the magnetic properties of the sintered body was as follows:
  • the reason why the cooling from the sintering temperature to the quenching temperature is done at a rate of 7C/min or slower rate is that when the cooling rate is faster than the above rate, coercive force is decreased remarkably.
  • the cooling rate is 2C/min or slower, the best results can be obtained.
  • the reason why the cooling is performed at a rate of 20C/min or faster rate in the quenching process is that if cooling is performed at a slower rate, coercive force is decreased.
  • cooling is performed at a rate of 100C/min or faster in the quenching process, the highest coercive force can be obtained.
  • the present invention is characterized in that a green body having given composition is sintered, an gradually cooled from the sintering temperature to a given quenching temperature, and then quickly cooled to room temperature, without requiring after heat treatment.
  • the magnet according to the present invention has excellent coercive force as well as excellent residual magnetic flux density and energy product.
  • a method of producing a permanent magnet having a residual magnetic flux density of at least 8000 Gauss, a normal coercive force of at least 8000 Oersted, an intrinsic coercive force of at least 27,000 Oersted and a maximum energy product of at least 17.6 X 10 Gauss Oersted comprising the steps of:
  • a powdery alloy from about 55-70% by weight of cobalt and about 30-45% by weight of at least one rare earth element, selected from the 8 group consisting of Y, La, Ce, Pr, Sm, Nd, Gd, Ho and Er,

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Power Engineering (AREA)
  • Hard Magnetic Materials (AREA)
  • Powder Metallurgy (AREA)
US377919A 1972-07-12 1973-07-10 Method of producing rare earth-cobalt permanent magnet using special cooling rates Expired - Lifetime US3873379A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4002508A (en) * 1974-08-27 1977-01-11 Aimants Ugimag S.A. Composition for permanent magnets of the family "rare earths-transition metals" and process for producing such a magnet
US4087291A (en) * 1974-08-13 1978-05-02 Bbc Brown, Boveri & Company, Limited Cerium misch-metal/cobalt magnets
US4090892A (en) * 1975-01-14 1978-05-23 Bbc Brown Boveri & Company Limited Permanent magnetic material which contains rare earth metals, especially neodymium, and cobalt process for its production and its use
US4217280A (en) * 1978-01-27 1980-08-12 Etablissements Nativelle S.A. Amino-3-cardenolide derivatives, process for their preparation, and pharmaceutical compositions containing same
US4382061A (en) * 1980-10-25 1983-05-03 Th. Goldschmidt Ag Alloy preparation for permanent magnets
CN106270505A (zh) * 2015-06-12 2017-01-04 成都锦粼科技有限公司 一种粉末冶金烧结工艺的降温处理方法

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4930474A (US06534493-20030318-C00166.png) * 1972-06-30 1974-03-18
JPS5927086B2 (ja) * 1974-10-23 1984-07-03 トウホクキンゾクコウギヨウ カブシキガイシヤ 希土類−コバルト系永久磁石の磁気誘導の温度係数調整法
JPS5248098A (en) * 1975-10-15 1977-04-16 Matsushita Electric Ind Co Ltd Method of preparing permanent magnets
US4597938A (en) * 1983-05-21 1986-07-01 Sumitomo Special Metals Co., Ltd. Process for producing permanent magnet materials
US4601875A (en) * 1983-05-25 1986-07-22 Sumitomo Special Metals Co., Ltd. Process for producing magnetic materials

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1752490A (en) * 1924-09-19 1930-04-01 Western Electric Co Process for changing the properties of silicon steel
US3663317A (en) * 1969-12-20 1972-05-16 Philips Corp Method of making a permanent-magnetisable body of compressed fine particles of a compound of m and r
US3682714A (en) * 1970-08-24 1972-08-08 Gen Electric Sintered cobalt-rare earth intermetallic product and permanent magnets produced therefrom
US3684593A (en) * 1970-11-02 1972-08-15 Gen Electric Heat-aged sintered cobalt-rare earth intermetallic product and process
US3755007A (en) * 1971-04-01 1973-08-28 Gen Electric Stabilized permanent magnet comprising a sintered and quenched body of compacted cobalt-rare earth particles
US3790414A (en) * 1967-11-15 1974-02-05 Matsushita Electric Ind Co Ltd As-CAST, RARE-EARTH-Co-Cu PERMANENT MAGNET MATERIAL

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1752490A (en) * 1924-09-19 1930-04-01 Western Electric Co Process for changing the properties of silicon steel
US3790414A (en) * 1967-11-15 1974-02-05 Matsushita Electric Ind Co Ltd As-CAST, RARE-EARTH-Co-Cu PERMANENT MAGNET MATERIAL
US3663317A (en) * 1969-12-20 1972-05-16 Philips Corp Method of making a permanent-magnetisable body of compressed fine particles of a compound of m and r
US3682714A (en) * 1970-08-24 1972-08-08 Gen Electric Sintered cobalt-rare earth intermetallic product and permanent magnets produced therefrom
US3684593A (en) * 1970-11-02 1972-08-15 Gen Electric Heat-aged sintered cobalt-rare earth intermetallic product and process
US3755007A (en) * 1971-04-01 1973-08-28 Gen Electric Stabilized permanent magnet comprising a sintered and quenched body of compacted cobalt-rare earth particles

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4087291A (en) * 1974-08-13 1978-05-02 Bbc Brown, Boveri & Company, Limited Cerium misch-metal/cobalt magnets
US4144105A (en) * 1974-08-13 1979-03-13 Bbc Brown, Boveri & Company, Limited Method of making cerium misch-metal/cobalt magnets
US4002508A (en) * 1974-08-27 1977-01-11 Aimants Ugimag S.A. Composition for permanent magnets of the family "rare earths-transition metals" and process for producing such a magnet
US4090892A (en) * 1975-01-14 1978-05-23 Bbc Brown Boveri & Company Limited Permanent magnetic material which contains rare earth metals, especially neodymium, and cobalt process for its production and its use
US4217280A (en) * 1978-01-27 1980-08-12 Etablissements Nativelle S.A. Amino-3-cardenolide derivatives, process for their preparation, and pharmaceutical compositions containing same
US4382061A (en) * 1980-10-25 1983-05-03 Th. Goldschmidt Ag Alloy preparation for permanent magnets
CN106270505A (zh) * 2015-06-12 2017-01-04 成都锦粼科技有限公司 一种粉末冶金烧结工艺的降温处理方法

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DE2335540A1 (de) 1974-01-24
JPS5113878B2 (US06534493-20030318-C00166.png) 1976-05-04
JPS4928897A (US06534493-20030318-C00166.png) 1974-03-14

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