EP0318131B1 - Method and assembly for producing extruded permanent magnet articles - Google Patents
Method and assembly for producing extruded permanent magnet articles Download PDFInfo
- Publication number
- EP0318131B1 EP0318131B1 EP88304916A EP88304916A EP0318131B1 EP 0318131 B1 EP0318131 B1 EP 0318131B1 EP 88304916 A EP88304916 A EP 88304916A EP 88304916 A EP88304916 A EP 88304916A EP 0318131 B1 EP0318131 B1 EP 0318131B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- core
- charge
- container
- permanent magnet
- assembly
- 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.)
- Expired - Lifetime
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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
- H01F1/06—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
- H01F1/08—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 pressed, sintered, or bound together
- H01F1/083—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 pressed, sintered, or bound together in a bonding agent
-
- 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
- B22F3/20—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by extruding
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0266—Moulding; Pressing
Definitions
- Cylindrical, extruded magnets as shown in Fig. 2, are conventionally produced by the use of a cylindrical extrusion container. Magnet alloy particles are introduced to the container, and the container is outgassed, evacuated and sealed. Thereafter, the container is heated to extrusion temperature and extruded to consolidate the particles to substantially full density.
- the hollow centre of the magnet is achieved by the use of a solid cylinder or mandrel of a diameter corresponding to the internal diameter of the magnet to be produced, which cylinder is attached to the extrusion ram. This solid cylinder moves with the extrusion ram during the extrusion operation and thereby maintains the desired inner diameter of the extruded magnet.
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
- Powder Metallurgy (AREA)
- Extrusion Moulding Of Plastics Or The Like (AREA)
Abstract
Description
- This invention relates to a method and assembly for producing extruded permanent magnet articles from particle charges of permanent magnet alloys.
- It is known to produce permanent magnet articles by powder metallurgy techniques, which include the consolidation of particles of the permanent magnet alloys. These practices are employed with permanent magnet alloys of at least one rare earth element and transition element. These conventional practices generally include the steps of aligning, pressing and sintering. With prior art practices of this type, high energy product (BHmax) and uniaxial anisotropic crystal alignment is achieved, and this combination finds utility in various permanent magnet applications.
- Uniaxial anisotropic crystal alignment, however, is not always advantageous for magnet applications for rotating machinery, motor rotors, beam focussing devices and the like. For these applications a [100] fibre texture wherein the C crystallographic axis is perpendicular to the axis of the magnet may be desired. One of the primary applications for magnets of this construction is for use in DC motors. In this application, with conventional practice, multiple segments of uniaxial anistropic magnets are needed to form the armature for the motor, which segments are identified as 2 positioned around a
motor shaft 4 in Fig. 1. - To obviate the need for the use of a plurality of magnet segments, as shown in Fig. 1, it is known to extrude a cylindrical magnet conforming to the required dimensions of the motor shaft. An
extruded magnet 6 in association with amotor shaft 4 is shown in Fig.2. - Cylindrical, extruded magnets, as shown in Fig. 2, are conventionally produced by the use of a cylindrical extrusion container. Magnet alloy particles are introduced to the container, and the container is outgassed, evacuated and sealed. Thereafter, the container is heated to extrusion temperature and extruded to consolidate the particles to substantially full density. The hollow centre of the magnet is achieved by the use of a solid cylinder or mandrel of a diameter corresponding to the internal diameter of the magnet to be produced, which cylinder is attached to the extrusion ram. This solid cylinder moves with the extrusion ram during the extrusion operation and thereby maintains the desired inner diameter of the extruded magnet. It is difficult to maintain concentricity of the inner and outer peripheries of the extruded magnet because the mandrel tends to wander and thus is not maintained in axial alignment during the extrusion operation. In addition, at the high extrusion ratios breaking of the mandrel may occur. It may be seen, therefore, that in producing cylindrical magnets by conventional extrusion practices, a cylindrical magnet having the required concentric dimensions is difficult to achieve.
- It is accordingly a primary object of the present invention to provide an extrusion method and assembly for use therewith that achieves improved concentricity in the production of extruded hollow cylindrical magnets.
- Another object of the invention is a method and assembly for use therewith that enables the production of a complete assembly, including a permanent magnet and associated shaft in a single extrusion operation.
- US 4640815 discloses a method and assembly for cladding an interior surface of a tubing with an alloy. A tubular insert is placed inside the tubing to be clad and the alloy particles are placed in the space between the tubular insert and the tubing. The assembly is then heated and extruded.
- Broadly, in accordance with the method of invention for producing a compacted fully dense permanent magnet article, a particle charge is provided of a permanent magnet alloy composition from which the permanent magnet article is to be made. The particle charge is placed in a cylindrical container having a generally axially positioned core with the charge surrounding the core within the container. The container is evacuated and sealed against the atmosphere. The container and particle charge are heated to elevated temperature and the container and charge are then extruded to compact the charge to substantially full density to thereby produce a substantially fully dense permanent magnet article having substantially identical magnetic properties along two orthogonal directions perpendicular to the extrusion direction to achieve a [100] fibre texture.
- To facilitate removal of the core to produce a cylindrical magnet article, a separating medium, such as magnesium oxide, may be provided on the core. The core may be of carbon steel, a soft magnet material or stainless steel. During the extrusion operation, the core may be bonded to the permanent magnet alloy. This is advantageous from the standpoint of producing a unitary magnet and shaft assembly during the extrusion operation.
- Extrusion ratios within the range of 1.5:1 to 50:1 may be employed with extrusion temperatures within the range of 500 to 1200°C.
- The method of the invention finds particular use in producing rare earth element containing permanent magnets. More specifically, it may be used in the production of magnets of this type wherein at least one rare earth element, such as samarium, neodymium and dysprosium, may be used with a transition element, such as iron and cobalt, plus boron and/or carbon.
- The invention also provides an assembly for use in producing a compacted, fully dense permanent magnet article by extrusion including a cylindrical container having a core generally axially positioned therein. The mandrel defines an annular chamber within the container. A particle charge of a permanent magnet alloy from which the article is to be made is provided within this annular chamber. Means are provided for sealing the annular chamber.
- A separating medium may be provided on the core. This facilitates removal of the core from the compacted magnet after extrusion. The core may be constructed of carbon steel, a soft magnet material or stainless steel.
- The invention will be more particularly described with reference to the accompanying drawings, in which:
- Fig. 1 shows a conventional assembly of permanent magnet segments in association with a motor shaft;
- Fig. 2 shows a conventional assembly of a motor shaft and an associated cylindrical permanent magnet;
- Fig. 3 shows in vertical cross-section an embodiment of an assembly in accordance with the invention for use in the method thereof to produce an extruded magnet; and
- Fig. 4 is a top view of the assembly of Fig.3.
- In accordance with one embodiment of the invention, with reference to Figs. 3 and 4, there is shown a
cylindrical container 8 havingend plates 10 withaxial openings 11 connected at opposite ends of the container, as by welding (not shown) to seal the container. Asolid core 12 is connected at opposite ends thereof to theplates 10 and a portion extends throughopenings 11. The core is axially positioned within thecontainer 8 to define therein anannular chamber 14 surrounding the core. Particles P of the magnet alloy composition from which the magnet is to be constructed are provided within theannular chamber 14 of thecontainer 8. - The assembly of Figs.3 and 4 so constructed is then after outgassing heated to extrusion temperature and extruded in conventional extruding apparatus to compact the particles in the container to substantially full density. Thereafter, the
core 12 may be removed from the compacted hollow cylindrical magnet. This may be facilitated by having the core provided with a separating medium, such as magnesium oxide, on the surface thereof. Alternately, the core may be bonded to the cylindrical magnet for use as an assembly in the production of a conventional motor rotor, as shown in Fig. 2. - A carbon steel extrusion container was made with a solid low-carbon rod, 3/4" (19mm) in diameter, welded axially to the top and bottom plates of a mild carbon steel can. Atomized (NdDy)₁₅Fe₇₉B₆ powder was put into the 3-1/8" (79.38mm) diameter can and the can was heated to 150°C, evacuated and sealed. The container was then heated to 927°C and extruded with a ratio of 13.8:1. The final extrusion consisted of a 0.3" (7.62mm) diameter steel rod surrounded by a ring shaped magnet with a wall thickness of about 0.25" (6.35mm). The magnetic properties are listed in Table 1. The identical properties along two orthogonal directions perpendicular to the extrusion direction indicates that a [100] fibre texture is obtained. This is the same magnetic behaviour as is observed for magnets extruded by conventional methods.
- These extruded magnets, with rods at their centres, can directly be magnetized into multiple poles and used for any type of rotating assembly.
TABLE I Sample Designation Test Direction Br kG Hc kOe Hci kOe BHmax MGOe EX-267 Axial 3.8 3.3 15.3 3.1 Transverse 1 7.3 6.4 15.8 12.3 Transverse 2 7.2 6.3 15.7 11.6 - To compare the practice of Example 1 with a conventional practice, the identical powder used in Example 1, (NdDy) ₁ ₅FE₇₉B₆, was placed into a 3-1/8" (79.38mm) diameter can and the can was heated to 150°C, evacuated and sealed. The can was then heated to 927°C and extruded with a ratio of 13.8:1. The magnetic properties of the resultant solid cylinder are presented in Table II. The magnetic properties are very similar to those obtained in Example 1. Thus, the extrusion technique of Example 1 in accordance with the invention will produce magnetic properties comparable to a conventional magnet extrusion method.
TABLE II Sample Designation Test Direction Br kG Hc kOe Hci kOe BHmax MGOe EX-235 Axial 3.6 3.1 13.9 2.7 Transverse 1 7.1 6.1 14.0 10.9 Transverse 2 7.1 6.1 14.1 11.0 - The same powder as used in Examples 1 and 2 was placed in a carbon steel extrusion container. This extrusion container was in the shape of a hollow circular cylinder, 3-1/8" (79.38mm) OD and 3/4" (19mm) ID. The container was evacuated, sealed and heated to 927°C and extruded at a 10:1 extrusion ratio. The inner diameter was maintained during extrusion by affixing a solid mandrel to the ram of the extrusion press in accordance with conventional practice. The magnetic properties, Table III, are similar to the properties presented in Tables I and II. The concentricity defined as the ratio of minimum to maximum wall thickness, was calculated to be 0.90. This value is poorer than the concentricity, 0.95, measured on the sample extruded in Example 1 in accordance with the invention.
TABLE III Sample Designation Test Direction Br kG Hc kOe Hci kOe BHmax MGOe EX-261 Axial 3.5 3.0 14.4 2.6 Transverse 7.4 6.5 16.5 12.4 - As may be seen from the above description and Examples, the invention provides for the production of a hollow permanent magnet by an extrusion practice wherein the desired dimensions of the magnet may be maintained while achieving permanent magnet properties comparable to conventional practices used for this purpose.
- It is to be understood that the shape of the core may include symmetrical geometries other than cylindrical. The particles of magnetic material for compaction may be produced by atomization, rapidly solidified ribbon, cast and pulverized particles, direct cast ingots or particles made by a reduction-diffusion practice.
- Since the core may be bonded to the compacted magnet during extrusion, an assembly may be produced having an outer shell of a permanent magnet alloy and a soft magnetic inner core, with the inner core acting to direct magnetic flux.
Claims (16)
- A method for producing a compacted fully dense permanent magnet article (6), said method comprising:
providing a particle (P) charge;
placing said charge in a cylindrical container; and
heating said container (8) and charge to an elevated temperature and extruding said container (8) and charge to compact said charge characterised in that the particle (P) charge is of a permanent magnet alloy composition from which said article (6) is to be made and the container (8) has a generally axially positioned core (12), with said charge surrounding said core (12) within said container (8) and the container (8) and charge are heated and extruded to form a substantially fully dense permanent magnet article (6) having substantially identical magnetic properties along two orthogonal directions perpendicular to the extrusion direction to achieve a [100] fiber texture. - A method according to Claim 1, wherein said core (12) is removed after compacting.
- A method according to Claim 1 or 2, wherein a separating medium is provided on said core (12).
- A method according to Claim 1, 2 or 3, wherein said core (12) is carbon steel.
- A method according to Claim 1, 2 or 3, wherein said core (12) is a soft magnetic material.
- A method according to Claim 1, 2 or 3, wherein said core (12) is stainless steel.
- A method according to Claim 1 or any one of Claims 3 to 6, wherein said core (12) is bonded to said permanent magnet alloy during said extrusion.
- A method according to any one of the preceding claims, wherein said extruding is performed with an extrusion ratio within the range of 1.5:1 to 50:1.
- A method according to any one of the preceding claims, wherein said extruding is performed with said charge at a temperature within the range of 500 to 1200°C.
- A method according to any one of the preceding claims, wherein said particle charge of a permanent magnet alloy comprises at least one rare earth element.
- An assembly adapted for use in producing a compacted, fully dense permanent magnet article (6) by extrusion, said assembly comprising a cylindrical container (8) and a particle (P) charge, characterised in that said container (8) has a solid core (12) generally axially positioned within said container (8) defining an annular chamber (14) within said container (8), and the particle (P) charge is of a permanent magnet alloy from which said article (6) is to be made and is provided within said annular chamber (14).
- An assembly according to Claim 11, wherein a separating medium is provided on said core (12).
- An assembly according to Claim 11 or 12, wherein said core (12) is carbon steel.
- An assembly according to Claim 11 or 12, wherein said core (12) is a soft magnet material.
- An assembly according to Claim 12 wherein said core (12) is stainless steel.
- An assembly according to any one of the preceding claims 11 to 15, wherein said particle charge of a permanent magnet alloy comprises at least one rare earth element.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT88304916T ATE87764T1 (en) | 1987-11-18 | 1988-05-31 | METHOD AND DEVICE FOR THE MANUFACTURE OF EXTRUDED BODIES FROM PERMANENT MAGNETIC MATERIAL. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12235187A | 1987-11-18 | 1987-11-18 | |
US122351 | 1998-07-24 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0318131A1 EP0318131A1 (en) | 1989-05-31 |
EP0318131B1 true EP0318131B1 (en) | 1993-03-31 |
Family
ID=22402192
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP88304916A Expired - Lifetime EP0318131B1 (en) | 1987-11-18 | 1988-05-31 | Method and assembly for producing extruded permanent magnet articles |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0318131B1 (en) |
JP (1) | JPH01151216A (en) |
AT (1) | ATE87764T1 (en) |
CA (1) | CA1301602C (en) |
DE (1) | DE3879886T2 (en) |
ES (1) | ES2040341T3 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE10312102B4 (en) * | 2003-03-19 | 2015-10-08 | Robert Bosch Gmbh | Device for measuring a level of a liquid in a container |
Family Cites Families (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3447230A (en) * | 1967-01-05 | 1969-06-03 | Sylvania Electric Prod | Art of making seamless hollow bodies from sinterable powders |
US3918867A (en) * | 1969-06-28 | 1975-11-11 | Philips Corp | Device for extruding permanent magnet bodies |
JPS5120592A (en) * | 1974-08-13 | 1976-02-18 | Matsushita Electric Ind Co Ltd | KYOJISEITAIFUNMATSUNO JIKAICHUSEIKEIYOKANAGATA |
JPS5176108A (en) * | 1974-12-27 | 1976-07-01 | Hitachi Metals Ltd | FUNMATSUYAKINHONYORUKANSEIZOHO OYOBIFUNMATSUJUTENYOKI |
GB1534221A (en) * | 1977-07-25 | 1978-11-29 | Ipari Szerelveny & Gepgyar | Process for the production of sleeves and like workpieces from hard metals of high cobalt content |
US4579607A (en) * | 1982-04-19 | 1986-04-01 | Matsushita Electric Industrial Company, Limited | Permanent Mn-Al-C alloy magnets and method for making same |
JPS60214515A (en) * | 1984-04-10 | 1985-10-26 | Seiko Epson Corp | Manufacture of cylindrical permanent magnet |
JPH0626169B2 (en) * | 1984-12-27 | 1994-04-06 | ティーディーケイ株式会社 | Method and apparatus for forming rare earth magnet in magnetic field |
US4602952A (en) * | 1985-04-23 | 1986-07-29 | Cameron Iron Works, Inc. | Process for making a composite powder metallurgical billet |
US4640815A (en) * | 1985-10-17 | 1987-02-03 | Crucible Materials Corporation | Method and assembly for producing extrusion-clad tubular product |
CA1269029A (en) * | 1986-01-29 | 1990-05-15 | Peter Vernia | Permanent magnet manufacture from very low coercivity crystalline rare earth-transition metal-boron alloy |
JPH0624176B2 (en) * | 1986-03-29 | 1994-03-30 | 信越化学工業株式会社 | Method for producing polar anisotropic long molded products |
-
1988
- 1988-05-04 CA CA000565893A patent/CA1301602C/en not_active Expired - Fee Related
- 1988-05-31 AT AT88304916T patent/ATE87764T1/en not_active IP Right Cessation
- 1988-05-31 ES ES198888304916T patent/ES2040341T3/en not_active Expired - Lifetime
- 1988-05-31 EP EP88304916A patent/EP0318131B1/en not_active Expired - Lifetime
- 1988-05-31 DE DE8888304916T patent/DE3879886T2/en not_active Expired - Fee Related
- 1988-10-04 JP JP63249177A patent/JPH01151216A/en active Pending
Also Published As
Publication number | Publication date |
---|---|
JPH01151216A (en) | 1989-06-14 |
DE3879886T2 (en) | 1993-08-26 |
EP0318131A1 (en) | 1989-05-31 |
DE3879886D1 (en) | 1993-05-06 |
ATE87764T1 (en) | 1993-04-15 |
ES2040341T3 (en) | 1993-10-16 |
CA1301602C (en) | 1992-05-26 |
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