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GB2235700A - Methods of manufacture of neodymium-iron-boron alloy pressings - Google Patents

Methods of manufacture of neodymium-iron-boron alloy pressings Download PDF

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Publication number
GB2235700A
GB2235700A GB9018079A GB9018079A GB2235700A GB 2235700 A GB2235700 A GB 2235700A GB 9018079 A GB9018079 A GB 9018079A GB 9018079 A GB9018079 A GB 9018079A GB 2235700 A GB2235700 A GB 2235700A
Authority
GB
United Kingdom
Prior art keywords
neodymium
iron
boron alloy
manufacture
pressings
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9018079A
Other versions
GB9018079D0 (en
GB2235700B (en
Inventor
Maria Jose Pinto Dias Wyborn
Peter Henry Dawson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alstom Holdings SA
Original Assignee
GEC Alsthom SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by GEC Alsthom SA filed Critical GEC Alsthom SA
Publication of GB9018079D0 publication Critical patent/GB9018079D0/en
Publication of GB2235700A publication Critical patent/GB2235700A/en
Application granted granted Critical
Publication of GB2235700B publication Critical patent/GB2235700B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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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
    • H01F1/047—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
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0576—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together pressed, e.g. hot working
    • 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
    • B22F3/14—Both compacting and sintering simultaneously

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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)
  • Manufacturing Cores, Coils, And Magnets (AREA)

Abstract

A method of manufacture of neodymium-iron-boron alloy pressings comprising the steps of: moulding correspondingly- shaped preforms from neodymium-iron-boron alloy in granular form in a die; and hot pressing each preform using a lubricant comprising boron nitride, at a temperature of 500 DEG - 1000 DEG C. The method is particularly useful in the manufacture of neodymium-iron-boron alloy magnets.

Description

Methods of Manufacture of Neodymium-Iron-Boron Alloy Pressings This invention relates to methods of manufacture of neodymium-iron-boron alloy pressings, and is particularly useful in the manufacture of permanent magnets.
In one known method, neodymium-iron-boron powder is pressed into a pellet shape and sintered to form a magnet. A disadvantage of this method is that the powder is susceptible to self-ignition.
In another known method, hot pressing is used to form such a magnet, at around 7500 - 800"C. A disadvantage of this method is that the high-strength graphite die used is not practical since it wears rapidly. Other die materials such as metals, cermets, carbon fibre reinforced carbon and ceramics give rise to the problem that the pressing sticks to the die or is not easily ejected from the die.
Lubricants tried to date to alleviate this sticking have been found to be not satisfactory, particularly in view of the fact that they adversely affect the surface finish of the magnet.
It is an object of the present invention to provide a method of manufacturing neodymium-iron-boron alloy pressings wherein the above problems are overcome.
According to a first aspect of the present invention there is provided a method of manufacture of neodymium-iron-boron alloy pressings comprising the steps of: moulding correspondingly-shaped preforms from neodymium-iron-boron alloy in granular form in a die; and hot pressing each preform using a lubricant comprising boron nitride, at a temperature of 500 - 1000it.
According to a second aspect of the present invention there is provided a permanent magnet comprising a neodymium-iron-boron alloy pressing manufactured by a method as just specified.
One method of manufacture of neodymium-iron-boron alloy pressings in accordance with the present invention will now be described by way of example.
Comminuted neodymium-iron-boron, obtained by crushing rapidly solidSfied ribbon, is first pre-pelletised in a cold-press die. The lubricant used in this pre-pelletising stage is boron nitride in an appropriate carrier, such as the DAG5711 lubricant supplied by Acheson Colloids Company, and is supplied to the cold-press prior to the addition of the comminuted neodymium-iron-boron. The shape of the die is that of a cylindrical pellet, about 0.010" - 0.015" (0.25 - 0.38mum) smaller in diameter than that of the intended final product which has a diameter of about i" (1.26 cm), and about three times longer than the i" (1.26 cm) length of the final product, to allow for axial compaction and transverse expansion in a subsequent hot-pressing stage.
The pre-pellets are then removed from the cold-press die, coated by spraying with the same lubricant as is used in the pre-pelletising stage, and fed singly into a tunsten carbide die at 750 - 800it in which they are left without being pressed in a protective atmosphere of argon for between about 10 to 40 seconds to pre-heat them. Such pre-heating tends to release any boron nitride lubricant that might have become trapped in the pre-pellets during the pre-pelletising stage. To release such boron nitride lubricant improves the magnetic properties of the final magnet. Finally, the pre-pellets are pressed in the hot die to their final shape in the protective atmosphere of argon.
Alternatively shaped preforms are washers, tubes and rectangular plates, with dimensions typically from i" to 1" (0.6 cm to 2.5 cm), but clearly any fairly regular shapes appropriate to the intended final magnet shape are possible. Dimensions from 2.5 mm to 15 to 30 cm are contemplated for magnets and are technically feasible.
In a modification of the above method mineral oil replaces the boron nitride in an appropriate carrier as the lubricant used in the pre-pelletising stage. In such a modified method the lubricant used in the hot pressing stage remains boron nitride in an appropriate carrier, the use of a lubricant comprising boron nitride in the hot pressing stage being an essential step of the method.
However, in the modified method the pre-heating time in the hot press must be increased to at least 60 seconds to release any mineral oil trapped in the pre-pellet during the cold pressing stage. Such mineral oil if not released would adversely affect the magnetic properties of the final magnet.
It is to be appreciated that the phrase 'neodymium-iron-boron alloy' refers to any alloy, the principal constituents of which are neodymium, iron and boron.

Claims (9)

1. A method of manufacture of neodymium-iron-boron alloy pressings comprising the steps of: moulding correspondingly-shaped preforms from neodymium-iron-boron alloy in granular form in a die; and hot pressing each preform using a lubricant comprising boron nitride, at a temperature of 500 - 1000"C.
2. A method according to Claim 1 wherein said lubricant is applied to the preforms before the step of hot pressing.
3. A method according to Claim 1 or Claim 2 wherein the hot-pressing is performed in a tungsten carbide die.
4. A method according to Claim 1 or Claim 2 or Claim 3 wherein the hot-pressing is performed in an inert atmosphere.
5. A method according to any one of the preceding claims wherein said temperature is 750 - 8000C.
6. A method according to any one of the preceding claims wherein mineral oil is used as a lubricant in said step of moulding corresponding-shaped preforms.
7. A method according to any one of Claims 1 to 5 wherein boron nitride is used as a lubricant in said step of moulding correspondingly-shaped preforms.
8. A method of manufacture of neodymium-iron-boron alloy pressings substantially as hereinbefore described.
9. A permanent magnet comprising a neodymium-iron-boron alloy pressing manufactured by a method according to any one of the preceding claims.
GB9018079A 1989-08-18 1990-08-17 Methods of manufacture of neodymium-iron-boron alloy pressings Expired - Fee Related GB2235700B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB898918915A GB8918915D0 (en) 1989-08-18 1989-08-18 Hot pressing of metal alloy

Publications (3)

Publication Number Publication Date
GB9018079D0 GB9018079D0 (en) 1990-10-03
GB2235700A true GB2235700A (en) 1991-03-13
GB2235700B GB2235700B (en) 1993-06-09

Family

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Family Applications (2)

Application Number Title Priority Date Filing Date
GB898918915A Pending GB8918915D0 (en) 1989-08-18 1989-08-18 Hot pressing of metal alloy
GB9018079A Expired - Fee Related GB2235700B (en) 1989-08-18 1990-08-17 Methods of manufacture of neodymium-iron-boron alloy pressings

Family Applications Before (1)

Application Number Title Priority Date Filing Date
GB898918915A Pending GB8918915D0 (en) 1989-08-18 1989-08-18 Hot pressing of metal alloy

Country Status (1)

Country Link
GB (2) GB8918915D0 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0513890A1 (en) * 1991-05-15 1992-11-19 General Motors Corporation Method of producing magnetic bodies using a lubrified cold-press die
EP0513891A1 (en) * 1991-05-15 1992-11-19 General Motors Corporation Hot-pressed magnets in open-air presses
EP0647180A4 (en) * 1991-05-17 1994-03-11 Hoeganaes Corp Thermoplastic coated magnetic powder compositions and methods of making same.
EP3163591A1 (en) * 2015-10-29 2017-05-03 Wilo Se Method and apparatus for producing permanent magnets

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3871200A (en) * 1973-02-06 1975-03-18 Sumitomo Electric Industries Method and apparatus for producing sintered metal product
US4050932A (en) * 1975-04-07 1977-09-27 General Motors Corporation Colloidal graphite forging lubricant and method
GB1509675A (en) * 1975-07-23 1978-05-04 Borg Warner Production of high density powdered metal parts
US4270951A (en) * 1978-12-08 1981-06-02 Ford Motor Company Sintering of coated briquette
US4321091A (en) * 1978-09-27 1982-03-23 Sumitomo Electric Industries, Ltd. Method for producing hot forged material from powder
US4808224A (en) * 1987-09-25 1989-02-28 Ceracon, Inc. Method of consolidating FeNdB magnets

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3871200A (en) * 1973-02-06 1975-03-18 Sumitomo Electric Industries Method and apparatus for producing sintered metal product
US4050932A (en) * 1975-04-07 1977-09-27 General Motors Corporation Colloidal graphite forging lubricant and method
GB1509675A (en) * 1975-07-23 1978-05-04 Borg Warner Production of high density powdered metal parts
US4321091A (en) * 1978-09-27 1982-03-23 Sumitomo Electric Industries, Ltd. Method for producing hot forged material from powder
US4270951A (en) * 1978-12-08 1981-06-02 Ford Motor Company Sintering of coated briquette
US4808224A (en) * 1987-09-25 1989-02-28 Ceracon, Inc. Method of consolidating FeNdB magnets

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0513890A1 (en) * 1991-05-15 1992-11-19 General Motors Corporation Method of producing magnetic bodies using a lubrified cold-press die
EP0513891A1 (en) * 1991-05-15 1992-11-19 General Motors Corporation Hot-pressed magnets in open-air presses
EP0647180A4 (en) * 1991-05-17 1994-03-11 Hoeganaes Corp Thermoplastic coated magnetic powder compositions and methods of making same.
EP0647180A1 (en) * 1991-05-17 1995-04-12 Hoeganaes Corporation Thermoplastic coated magnetic powder compositions and methods of making same
EP3163591A1 (en) * 2015-10-29 2017-05-03 Wilo Se Method and apparatus for producing permanent magnets

Also Published As

Publication number Publication date
GB8918915D0 (en) 1989-09-27
GB9018079D0 (en) 1990-10-03
GB2235700B (en) 1993-06-09

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Legal Events

Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 19960817