US3891476A - Method of magnetizing a body of M{HD 5{B R at high temperatures - Google Patents

Method of magnetizing a body of M{HD 5{B R at high temperatures Download PDF

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US3891476A
US3891476A US418124A US41812473A US3891476A US 3891476 A US3891476 A US 3891476A US 418124 A US418124 A US 418124A US 41812473 A US41812473 A US 41812473A US 3891476 A US3891476 A US 3891476A
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temperature
field
magnetization
strength
magnetic
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US418124A
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Pieter Aart Naastepad
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US Philips Corp
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US Philips Corp
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F13/00—Apparatus or processes for magnetising or demagnetising
    • H01F13/003—Methods and devices for magnetising permanent magnets

Definitions

  • Steinhauser 5 7 ABSTRACT A method for the magnetization of a sintered magnetic body mainly consisting of a material of the type M R, in which M may be cobalt and R a rare earth metal.
  • the magnetization proceeds most easily when magnetization is carried out consistently in one direction or when magnetization is carried out at a temperature between 200C and the Curie point.
  • the body to be magnetized is preferably first annealed at a temperature between the sintering temperature and a temperature which is 300C lower and magnetized during the subsequent cooling.
  • the invention relates to a method for the magnetization of a magnetic body principally consisting of a material of the type M R, in which M is Co or a combination of Co with at least one representative of the group consisting of Fe, Ni and Cu, and in which R is at least one representative of the group consisting of Y. Th and the rare earth metals.
  • Such a magnetic body is usually magnetized in a very strong magnetic field (two to three times the intrinsic coercive field strength of the material) so as to saturate the material in such mannerthat the hysteresis loop is closed.
  • the intrinsic coercive field strength for example, of SmCo is approximately l2,000 Oe and it is usual to use a field of approximately 40,000 Oe for the magnetization.
  • SmCo is approximately l2,000 Oe and it is usual to use a field of approximately 40,000 Oe for the magnetization.
  • Such a high field is difficult to realize in series production of permanent magnets so that one would have to be satisfied with a final product which does not have the optimum magnetic value. This problem is the more urgent when a magnet of the present type is to be incorporated in an apparatus in the demagnetized state.
  • a field strength equal to the intrinsic coercive field strength of the material is sufficient to magnetically saturate a body of M R. provided magnetization is carried out in only one direction. Magnetization with a field equal to the coercive field strength proves to be impossible when magnetization is not consequently carried out in one direction, but, for example, first in a first direction and then in the opposite direction. In that case, a field of at least two to three times the coercive field strength is necessary to magnetize the material to saturation.
  • a second embodiment of the method for magnetically saturating a sintered magnetic body consisting principally of a material of the type M R involves carrying out magnetization at a temperature between 200C and the Curie point of the material in a field whose strength is less than two times the intrinsic coercive field strength of the material.
  • the use of the method according to the invention results in the advantage that magnetization can be carried out in certain cases in which this is not possible when using the usual method or when the latter would result in undesired complications. This is the case, for example, when the magnetization must be carried out in a place which is difficult to reach for the field to be applied or in manufacturing a multipolar magnet.
  • a magnetization field is sufficient whose strength corresponds to or is even smaller than the intrinsic coercive field strength of the material, provided the magnetization is carried out at a sufficiently high temperature, in particular above 400C.
  • the magnetizing field When magnetization is carried out at a temperature above 200C, according to a preferred embodiment of the method according to the invention, the magnetizing field, during the subsequent cooling to room temperature, is maintained to a temperature below 200C, and preferably to room temperature. If this is not done, the possibility exists that the magnetized body demagnetizes itself entirely or partly.
  • the magnetic body is sintered and subsequently is annealed at a temperature between the sintering temperature and a temperature which is 300C lower before it is introduced into the magnetizing field.
  • a magnetic body pretreated in such manner is not only found to be easier to magnetize but in addition the resulting magnet has a higher intrinsic coercive force.
  • the magnetic body When the magnetic body is to be magnetized immediately after the annealing treatment, it is preferrable to cause the magnetisation field to influence the body during the cooling from the annealing temperature to room temperature. This makes an additional heating- /cooling phase superfluous.
  • FIG. 1 shows the dependence of the intrinsic coer' cive force ,H,. as a function of various magnetization fields H.
  • FIG. 2 shows for magnets treated in various manners the dependence of the intrinsic coercive force ,H,. as a function of various magnetizing fields H.
  • FIG. 3 shows for various magnetizing fields the dependence of the relative intrinsic coercive force ,H (rel) as a function of various magnetization temperatures T.
  • FIG. 4 shows a series of magnetisations with increasing field in one sense for an SmCo -magnet.
  • EXPERIMENT l A compressed block consisting of powder particles of the compound SmCo was sintered at 1,100C. The resulting sintered body was magnetized at room temperature in a field of 45,000 Oe. The B-H curve of the thus magnetized body was measured. The intrinsic coercive force ,H proved to be 11,000 Oe. The body was then demagnetized at 500C in an alternating field having a maximum field strength of 2,000 Oe. It was then measured at room temperature to show how the ,H,. depends upon the strength of the magnetizing field (FIG. 1). A magnetizing field of 25,000 Oe proved to be necessary to regain the ,H,. of 1 1,000 Oe, that is to say to reach again the outer loop of the 8-H curve. It is to be noted that the body was not always consistently magnetized in one direction.
  • EXPERIMENT III The SmCo magnet used in the preceding experiments was demagnetized at 500C in an alternating field and it was investigated in three different magnetization fields of 5,000 0e, 8,000 Oe and 10,000 Oe, respectively, how the magnetization depends upon the temperature.
  • FIG. 3 shows the results of the investigation.
  • the relative ,H,., i.e. the ,H of the magnet divided by the ,H, after magnetization at room temperature in a field of 45,000 Oe is plotted on the vertical axis.
  • the temperature T at which magnetization was carried out is plotted on the horizontal axis.
  • Curve I shows the variation of the relative ,H when using a magnetization field of 5,000 Oe
  • curve 11 shows the variation when using a field of 8,000 Oe
  • curve 111 shows the variation when using a field of 10,000 Oe.
  • magnetization fields may be used which are much weaker than the field to be derived from FIG. 1 (which has a strength of 25,000 Oe), provided that a suitable magnetization temperature is chosen. However, this higher temperature is still far below the Curie temperature which is approximately 730C).
  • FIG. 4 shows with reference to a number of B-H curves how in a certain experiment an SmCoS magnetic body was consistently magnetized in one direction.
  • the body was first introduced into a small field, said field was caused to decrease and then to grow in the original direction to a larger value than the initial value, caused to decrease again, and so on.
  • inner loops in the direction of the outer loop of the 8-H characteristic. It may be established from this experiment that the ,H,. values of the successive inner loops are always much larger than the required magnetization fields. It is still to be noted that the direction of magnetization does not depend upon the material, but only upon the direction with which has been started.
  • a method of magnetizing a body consisting principally of a material of the composition M R, M consisting of an element selected from the group consisting of Co and Co in combination with one of the elements Fe, Ni, and Cu, and R being an element selected from the group consisting of Y, Th, and the rare earth metals comprising the steps of, subjecting said body to a magnetic field having a strength sufficient to magnetically saturate the material and less than twice the intrinsic coercive field strength of the material at a temperature between 200C and 0.5 times the Kelvin temperature of the Curie point of said material.
  • the magnetic body is formed by compressing the material into a body which is heated at about l,l00C and subsequently said body is annealed at a temperature between said temperature and a temperature which is 300C lower before it is subjected to the magnetic field.
US418124A 1972-12-15 1973-11-21 Method of magnetizing a body of M{HD 5{B R at high temperatures Expired - Lifetime US3891476A (en)

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NL7217051A NL7217051A (de) 1972-12-15 1972-12-15

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US (1) US3891476A (de)
JP (1) JPS5344679B2 (de)
CH (1) CH568643A5 (de)
DE (1) DE2358595C3 (de)
FR (1) FR2327615A1 (de)
GB (1) GB1449687A (de)
NL (1) NL7217051A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4156623A (en) * 1974-11-29 1979-05-29 General Electric Company Method for increasing the effectiveness of a magnetic field for magnetizing cobalt-rare earth alloy
US4347201A (en) * 1978-11-04 1982-08-31 Fujitsu Limited Process and apparatus for producing a temperature sensitive element
US20080172861A1 (en) * 2007-01-23 2008-07-24 Holmes Alan G Methods for manufacturing motor core parts with magnetic orientation
CN110610789A (zh) * 2018-06-14 2019-12-24 中国科学院宁波材料技术与工程研究所 永磁材料的稳磁处理方法

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH604342A5 (de) * 1976-10-04 1978-09-15 Bbc Brown Boveri & Cie
US4114532A (en) * 1976-10-12 1978-09-19 Dataproducts Corporation Impact printer magnet assembly
JPS6021325U (ja) * 1983-07-18 1985-02-14 株式会社東洋クオリティワン 樹脂廃棄物の溶解装置
HU190975B (en) * 1984-09-28 1986-12-28 Elzett Muevek,Hu Magnetizing device for magnetizing key-magnets and rotor magnets of magnetic system safety lock
DE3609530C2 (de) * 1986-03-21 1995-08-31 Erich Dr Ing Steingroever Verfahren zum automatischen Einstellen des Arbeitspunktes von Dauermagneten
JPH0346205A (ja) * 1989-07-01 1991-02-27 Jionkoo Kantee Guufun Yousenkonsuu 交流ないしパルス電流による磁化特性改善方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3138494A (en) * 1961-05-01 1964-06-23 Allegheny Ludlum Steel Method of annealing magnetic materials
US3639182A (en) * 1969-03-27 1972-02-01 Gen Electric Method for improving the effectiveness of a magnetic field for magnetizing permanent magnets
US3660175A (en) * 1969-09-18 1972-05-02 Philips Corp Method of manufacturing a magnetically anisotropic magnet body
US3684593A (en) * 1970-11-02 1972-08-15 Gen Electric Heat-aged sintered cobalt-rare earth intermetallic product and process
US3723197A (en) * 1969-09-20 1973-03-27 K Buschow Method of manufacturing a body having anisotropic, permanent magneticproperties
US3802935A (en) * 1972-05-25 1974-04-09 Geeral Electric Co Demagnetization of cobalt-rare earth magnets

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3138494A (en) * 1961-05-01 1964-06-23 Allegheny Ludlum Steel Method of annealing magnetic materials
US3639182A (en) * 1969-03-27 1972-02-01 Gen Electric Method for improving the effectiveness of a magnetic field for magnetizing permanent magnets
US3660175A (en) * 1969-09-18 1972-05-02 Philips Corp Method of manufacturing a magnetically anisotropic magnet body
US3723197A (en) * 1969-09-20 1973-03-27 K Buschow Method of manufacturing a body having anisotropic, permanent magneticproperties
US3684593A (en) * 1970-11-02 1972-08-15 Gen Electric Heat-aged sintered cobalt-rare earth intermetallic product and process
US3802935A (en) * 1972-05-25 1974-04-09 Geeral Electric Co Demagnetization of cobalt-rare earth magnets

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4156623A (en) * 1974-11-29 1979-05-29 General Electric Company Method for increasing the effectiveness of a magnetic field for magnetizing cobalt-rare earth alloy
US4347201A (en) * 1978-11-04 1982-08-31 Fujitsu Limited Process and apparatus for producing a temperature sensitive element
US4459248A (en) * 1978-11-04 1984-07-10 Fujitsu Limited Process and apparatus for producing a temperature sensitive element
US20080172861A1 (en) * 2007-01-23 2008-07-24 Holmes Alan G Methods for manufacturing motor core parts with magnetic orientation
CN110610789A (zh) * 2018-06-14 2019-12-24 中国科学院宁波材料技术与工程研究所 永磁材料的稳磁处理方法
EP3660873A4 (de) * 2018-06-14 2020-09-30 Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences Behandlungsverfahren zur magnetisierungsstabilisierung für permanent magnetisierbares material
US11538611B2 (en) 2018-06-14 2022-12-27 Ningbo Institute Of Materials Technology And Engineering, Chinese Academy Of Sciences Magnetization stabilizing treatment method for permanently magnetizable material

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Publication number Publication date
DE2358595A1 (de) 1974-06-20
FR2327615A1 (fr) 1977-05-06
JPS5344679B2 (de) 1978-11-30
NL7217051A (de) 1974-06-18
DE2358595C3 (de) 1979-11-08
JPS4989199A (de) 1974-08-26
GB1449687A (en) 1976-09-15
DE2358595B2 (de) 1979-03-08
CH568643A5 (de) 1975-10-31
FR2327615B1 (de) 1978-04-21

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