EP1607491B1 - Verfahren zur Herstellung einer Permanentmagnetischer Legierung mit hervorragenden wärmeresistenten Eigenschaften - Google Patents

Verfahren zur Herstellung einer Permanentmagnetischer Legierung mit hervorragenden wärmeresistenten Eigenschaften Download PDF

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EP1607491B1
EP1607491B1 EP05017546A EP05017546A EP1607491B1 EP 1607491 B1 EP1607491 B1 EP 1607491B1 EP 05017546 A EP05017546 A EP 05017546A EP 05017546 A EP05017546 A EP 05017546A EP 1607491 B1 EP1607491 B1 EP 1607491B1
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alloy
permanent magnet
temperature
irreversible demagnetization
magnet
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EP1607491A1 (de
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Masami Kamada
Michio Obata
Yuichi Sato
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Dowa Holdings Co Ltd
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Dowa Holdings Co Ltd
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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
    • H01F1/057—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
    • H01F1/0577—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 sintered
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
    • 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
    • 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
    • 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
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • 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
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

  • the present invention relates to a process for production of a permanent magnet alloy based on R (wherein R represents yttrium (Y) or a rare-earth element), boron (B), carbon (C), cobalt (Co) and iron (Fe), which exhibits particularly improved heat resistance as such that little degradation occurs on the magnetic force even in case it is used under ambient at a temperature as high as 200 °C.
  • R represents yttrium (Y) or a rare-earth element
  • B boron
  • C carbon
  • Co cobalt
  • Fe iron
  • a Sm-Co based magnet is known as a rare-earth magnet having improved heat resistance, but is expensive.
  • the term "heat resistance” as referred herein particularly signifies that the magnetic force of the magnet does not degrade by heat.
  • Patent No. 2740981 Japanese Patent Public Disclosure No. 4-116144 (Patent No. 2740981 )
  • one of inventors of the present invention and others have proposed a R-B-C-Co-Fe based permanent magnet alloy as a rare-earth magnet reduced in cost and yet improved in heat resistance.
  • This magnet alloy contains carbon (C) as an essential alloy element, and utilizes a combination of a light rare-earth element and a heavy rare-earth element for the rare-earth element (R).
  • the disclosure teaches that the irreversible demagnetization of the magnet alloy is improved remarkably (i.e., the negative irreverible demagnetization values approach 0%) by the incorporation of C, and that the irreversible demagnetization is further improved by partly incorporating a heavy rare-earth element for R.
  • an object of the present invention is to provide a permanent magnet having improved heat resistance feasible for use at such a high temperature of 200 °C, yet at a low production cost.
  • a permanent magnet alloy having an irreversible demagnetization in the range of 0 to -20% can be obtained by properly selecting the combination of Dy and Tb, e.g., a case in which Dy and Tb in total account for 0.5 to 5 at.% and in which Dy is in the range of 0.3 to 4.9 at.% and Tb is in the range of 0 .1 to 4 . 7 at.% (i.e., the compositional area defined by points A, B, C and D plotted in Fig. 1 ).
  • a permanent magnet alloy having an irreversible demagnetization in the range of 0 to -15% can be obtained by controlling the content of Dy and Tb to fall in the range defined by points B, C, H, E, F and G plotted in Fig. 1 .
  • the irreversible demagnetization at 200 °C serves as an index. More specifically, it is preferred to select a design that the value (a negative value) of irreversible demagnetization (200 °C) according to equation (1) above approaches 0 % as possible.
  • the irreversible demagnetization (160 °C) is a value obtained by magnetizing a specimen shaped as such that Pc be 3 and magnetized at 50 KOe, and by measuring the flux values A 25 and A 160 .
  • the incorporation of C is known to be effective for improving the heat resistance (and for imparting resistance against oxidation).
  • nothing is known about the irreversible demagnetization at 200 °C.
  • the existing R-(Fe,Co)-B based sintered magnet alloys which do not contain C as the alloy element, none is found to yield an irreversible demagnetization (200 °C) in a range of 0% to -20 %.
  • the present inventors have continued various types of tests and researches on the composition of the alloy and the process for the production thereof with an aim to improve the heat resistance of the R-Fe-Co-C-B based sintered magnet alloys, and have found that the combined addition of Dy and Tb in proper quantities results in a magnet alloy having a considerably low irreversible demagnetization.
  • the effect of the addition is not remarkable when Dy or Tb is added independent to each other, but a favorable heat resistance is achieved in case the both are added in combination.
  • the disadvantageous characteristic of a rare-earth magnet i.e., the tendency prone to oxidation
  • Carbon also contributes to the reduction of irreversible demagnetization. If the addition of C is less than 0.1 at.%, the effect thereof on improving the oxidation-resistance and the heat resistance is not sufficient. If the addition of C should exceed 15 at.%, on the other hand, the value of Br begins to drop. Accordingly, C is incorporated at a content in a range of 0.1 to 15 at.%, but a preferred range is 1.0 - 10 at.%, and more preferably, is in the range of 2.5 to 7 at.%.
  • B Boron
  • B is necessary for the formation of a magnetic phase, and it should be present at least 0.5 at.%.
  • B is added in an amount of 0.5 to 15 at. %, preferably 1.0 to 10 at. %, and more preferably, 1.5 to 7 at.%.
  • C and B in total must account for at least 2 at.%.
  • the incorporation of C and B in total exceeding 30 at.% impairs the magnetic properties; accordingly, C and B in total must account for 2 to 30 at.%.
  • Cobalt elevates the Curie point while maintaining the magnetic properties.
  • the addition of Co is essential, but an addition thereof in an amount exceeding 40 at.% considerably decreases the coercive force of the magnet. Accordingly, the addition of Co must be 40 at.% or less.
  • Dysprosium (Dy) and terbium (Tb) are the characteristic elements of the magnet of the present invention, and their combined addition remarkably lowers the irreversible demagnetization.
  • Dy and Tb must be added at an amount of 0.5 at.% or more in total, but their effect on improving the heat resistance saturates if a total addition of them is in excess of 5 at.% and it may reversibly affect the magnetic properties. Accordingly, their addition in total must be 0.5 to 5 at.%.
  • the addition of Dy or Tb alone does not contribute to the reduction of irreversible demagnetization. Presumably, Dy and Tb function synergetically to lower the irreversible demagnetization.
  • those elements are preferably added at a Tb(at.%)/Dy(at.%) ratio, expressed by percentage on atomic basis, in the range of 0.1 to 0.8.
  • Tb(at.%)/Dy(at.%) ratio expressed by percentage on atomic basis
  • the addition of 0.3 to 4.9 at.% of Dy and 0.1 to 4.7 at. % of Tb enables a magnet having improved heat resistance with a irreversible demagnetization at 200 °C at a permeance coefficient of 1 in a range of 0 to -20%, preferably 0 to -15%.
  • At least one element selected from the group consisting of Nd, Pr, Ce, La, Y, Gd, Ho, Er and Tm may be added either singly or in combination thereof at an amount of 8 to 20 at.%.
  • R a magnetic phase and a grain boundary phase are developed in the sintered magnet alloy to maintain iHc and Br at high values.
  • the elements for R particularly preferred are Nd and Pr, and the addition of Nd alone or a combination of Nd with Pr is most preferred. If the addition of R is less than 8 at. %, a sufficient high Br cannot be achieved, and the addition of R in excess of 20 at.% results in an insufficient value of Br.
  • a preferred range of R is 13 to 18 at.%.
  • a permanent magnet alloy according to the present invention having the composition above yields an irreversible demagnetization (200 °C) in accordance with equation (1) above at a low level as such in a range of 0 to -20 %, preferably 0 to -15 %, and most preferably, 0 to -5 %.
  • the present invention provides for the first time, a permanent magnet alloy other than a Sm-Co based magnet suitable for high temperature use.
  • known boron-containing rare-earth magnets having higher coercive force were used by taking the demagnetization at higher temperatures into account.
  • the magnet according to the present invention is almost free of demagnetization even at elevated temperatures, it can be used as it is as a permanent magnet having a high magnetic force.
  • the magnet according to the present invention can maintain the magnetic properties for use at elevated temperatures at an iHc of 13 KOe or higher, and preferably 15 KOe or higher.
  • the magnet according to the present invention can be regarded as an effective permanent magnet alloy.
  • the permanent magnet alloy according to the present invention can be produced by a process consisting of sequential steps of melting, casting, crushing, molding, and sintering.
  • a melt casting process there can be employed processes such as vacuum melting and casting, melting and casting under an inert gas atmosphere, quench rolling, atomization, etc.
  • a step of heat treatment between the steps of casting and crushing so as to subject the product before crushing to a heat treatment at a temperature of 600 °C or higher under an inert gas atmosphere. In this manner, the irreversible demagnetization can be further lowered.
  • the sintering step it is preferred to sinter the molding in the temperature range of 1,000 to 1,200 °C under an inert gas atmosphere and gradually cooling from the sintering temperature to a temperature in a range of 600 to 900 °C, followed by quenching therefrom.
  • the irreversible demagnetization can be further lowered by the quenching performed after the sintering.
  • the sintered magnet alloy according to the present invention can be produced in accordance with the production method for a sintered magnet described in Japanese Patent Public Disclosure No. 4-116144 , except for the heat treatment and the quench treatment after the sintering described above.
  • the process of production is outlined below.
  • the raw materials weighed as such to yield the desired alloy composition are molten in a vacuum melting furnace at a temperature of 1,600 °C or higher, and are casted by quenching in a water-cooled casting mold.
  • the cast ingot thus obtained is thermally treated under gaseous Ar at a temperature of 600 °C or higher, and subjected to coarse crushing by using a jaw crusher.
  • the coarse-grained powder thus prepared was finely milled by using a vibration ball mill to obtain a powder consisting of particles having an average diameter in a range of 2 to 10 ⁇ m. Those steps for such size reduction are carried out under gaseous Ar atmosphere.
  • a part of the raw material for C can be added in the latter step of milling.
  • Carbon black is suitable for use as the raw material of C, but also usable are organic materials containing C, such as an aliphatic hydrocarbon, a higher fatty acid alcohol, a higher fatty acid, a higher fatty acid amide, a metal soap, a fatty acid ester, etc.
  • the powder thus obtained is compaction molded while applying an external magnetic field.
  • the range for the molding pressure is 1 to 5 t/cm 2 , and that for the external magnetic field is 15 KOe or higher.
  • the molding step also is preferably carried out under a gaseous Ar atmosphere.
  • the molded product thus obtained is then sintered under gaseous Ar in the temperature range of 1,000 to 1,200 °C for a duration of about 2 hours.
  • the resulting product is gradually cooled to a temperature in the range of 600 to 900 °C, and quenched from the temperature.
  • a method of spraying a low temperature inert gas or a method of immersing the sintered product into water, an oil, or a liquid similar thereto there can be employed a method of spraying a low temperature inert gas or a method of immersing the sintered product into water, an oil, or a liquid similar thereto, and preferably, rapid cooling is performed from the quench initiation temperature in the range of 600 to 900 °C to a temperature of 400 °C or lower at a cooling rate of -50 °C/min or higher, preferably -100 °C/min or higher.
  • a process for producing a permanent magnet alloy having an improved heat resistance comprising melting and casting each of the raw materials of the alloying elements, subjecting the resulting alloy to pulverizing, compaction molding the resulting powder, and sintering the molding under an inert gas atmosphere in a temperature range of 1,000 to 1, 200 °C to obtain a sintered magnet alloy, characterized in that the alloy before pulverizing is thermally treated under an inert gas atmosphere at a temperature of 600 °C or higher, and/or that the process further comprises, after sintering the molding under an inert gas atmosphere in a temperature range of 1,000 to 1,200 °C, gradually cooling the sinter from the sintered temperature to a temperature range of 600 to 900 °C, followed by quenching.
  • a part of the raw material of C may be added during melting, and the rest may be added during the pulverizing of the alloy.
  • each of the raw materials weighed as such to yield the desired alloy composition above were molten in a vacuum melting furnace. A part of the raw material for C was not fed into the melting furnace but was reserved. The melt thus obtained was quench cast in a water-cooled copper casting mold from 1, 600 °C to obtain a cast alloy ingot. After heat treating under gaseous Ar at a temperature shown in Table 1, or without applying the heat treatment, the cast alloy ingot was coarsely crushed by using a jaw crusher, and the coarsely crushed product was fed into a vibration ball mill together with the reserved rest of the raw material for C to perform milling. Thus was obtained a powder having an average particle diameter of 5 ⁇ m.
  • the powder product thus obtained was molded under a magnetic field by applying a pressure of 2 t/cm 2 and an external magnetic field of 15 KOe.
  • the resulting molding was sintered under gaseous Ar at 1,100 °C for a duration of 2 hours, and was gradually cooled from the sintering temperature to the temperature of initiating quenching shown in Table 1, at which temperature rapid cooling was started at a cooling rate also given in Table 1 by blowing gaseous Ar to the molding.
  • the magnetic properties, heat resistance, and oxidation resistance of the resulting sinter were evaluated to obtain the results given in Table 1.
  • the heat resistance and the oxidation resistance of the sinter were evaluated as follows.
  • the specimen was shaped in such a manner that the permeance coefficient (Pc) thereof be 1. More specifically, the specimen was cut out to a size of 2.5 mm ⁇ 2.5 mm ⁇ 1.05 mm.
  • the specimen thus obtained was magnetized by applying an external magnetic field of 50 KOe to measure the flux value at room temperature (25 °C).
  • a flux meter manufactured by Toyo Jiki Kogyo Co. Ltd. equipped with an iron core coil was used to obtain the flux value.
  • the flux value thus obtained was designated A 25.
  • the magnetized specimen thus obtained was maintained at 200 °C for a duration of 120 minutes.
  • the heating held for a duration of 120 minutes was carried out in an oil bath filled with silicone oil.
  • the temperature of the oil bath was precisely controlled so that the fluctuation in temperature may fall within a range of ⁇ 0.1 °C.
  • the specimen taken out from the oil bath was cooled sufficiently at room temperature to measure the flux value again by using the flux meter above.
  • the flux value thus obtained was designated A 200 .
  • Temperature coefficient of coercive force % / °C 100 ⁇ B 1 - B 0 / B 0 / 160 - 25 where, B 0 is the coercive force at room temperature, and B 1 is the coercive force obtained at 160 °C by using the same vibrating-sample magnetometer.
  • the progressive formation of rust was measured by performing pressure cooker test (PCT). More specifically, the specimen was held in a testing chamber manufactured by Tabai Espec Corp. at 120 °C, 2 atm, and 100 % RH (saturated condition) for a duration of 100 hours, and the generation of rust was visually observed.
  • PCT pressure cooker test
  • the alloy a With respect to the conditions of production, it can be clearly seen by comparing the alloy a with the alloy b that the irreversible demagnetization can be lowered by performing heat treatment on the cast ingot. Furthermore, by comparing the results for alloys a, c and d, the coercive force can be improved and the irreversible demagnetization can be lowered by quenching the sintered alloy from a temperature of at least 700 °C or higher.
  • Example 2 5.0 1.8 2.5 1.0 13.0 12.0 64.7 3.5 0.4 11.0 17 31 - 4 - 0.7 - 0.26 None Example 3 4.0 3.0 2.5 0.5 13.0 12.0 65.0 3.0 0.2 12.0 17 32 -5 - 0.8 - 0.27 None Example 4 5.0 1.8 3.5 0.4 13.0 12.0 64.3 3.9 0.1 11.5 17 30 -7 - 0.9 - 0.28 None Example 5 5.0 1.8 0.4 0.3 13.0 12.0 67.0 0.7 0.8 13.5 13 38 -20 - 1.5 -0.42 None Example 6 5.0 1.8 3.8 0.7 15.0 12.0 61.7
  • the permanent magnet alloys of Examples 2 to 16 in which both Dy and Tb are added all yield a low irreversible demagnetization at 200 °C, and the irreversible demagnetization at 160 °C also is very close to 0 %. Furthermore, it can be seen that they not only have a low temperature coefficient of coercive force, but also exhibit excellent oxidation resistance.
  • the irreversible demagnetization at 200 °C for Comparative Example 1 in which no Dy nor Tb is added, is as large as -95 %, that for Comparative Example 2 containing no Tb and 0.5 at.% Dy is -95 %, and that for Comparative Example 4 containing no Dy and 0.5% by atomic Tb is -91 %. It can be understood therefrom that these permanent magnet alloys completely lose their magnetic force when heated to 200 °C. That is, the addition of Dy alone or Tb alone has no effect on the irreversible demagnetization at 200 °C.
  • Comparative Example 3 Although the addition of Dy alone in a large amount, as shown in Comparative Example 3, lowers the irreversible demagnetization to some extent, the effect is not sufficient. Referring to Comparative Example 5, the oxidation resistance is inferior because the content of C falls lower than the range specified in the present invention.
  • the alloy of Comparative Example 6 contains 3.0 at.% of Tb but no Dy. It can be seen that, although a favorable heat resistance is obtained, the irreversible demagnetization at 200 °C is as low as -30 %.
  • Fig. 1 is a diagram showing how the values of irreversible demagnetization at 200 °C are influenced by the contents of Dy and Tb; all of the magnets given in Table 2 are plotted in the diagram wherein the abscissa shows the content of Dy (at. %) and the ordinate shows the content of Tb (at.%).
  • the numerals provided in Fig. 1 each show the irreversible demagnetization at 200 °C for the plotted values.
  • a peak (a point closest to 0 %) in irreversible demagnetization at 200 °C is present for the area defined by 2 to 3 at.% Dy and 0.3 to 1.5 at.% Tb. More specifically, the straight lines indicated by numerals (1), (2), (3), (4), (5) and (6) define the areas with particular content of Dy and Tb, and the area which yield an irreversible demagnetization at 200 °C in the range of 0 to -20 % can be defined by the crossing points A, B, C and D.
  • the area which yield an irreversible demagnetization at 200 °C in a range of 0 to -15 % can be defined by the crossing points B, C, H, E, F and G.
  • the straight lines (1) to (6) can be expressed by the following equations:
  • Fig. 2 shows the observed irreversible demagnetization values at different temperatures for the magnet having the highest heat resistance among the magnets disclosed in Japanese Patent Public Disclosure No. 4-116144 as described in Example 24 thereof and those of Example 2 according to the present invention, in which the specimens are each shaped as such that the permeance coefficient (Pc) be 3 and magnetized by applying an external magnetic field of 50 KOe.
  • Fig. 3 is a diagram showing the observed irreversible demagnetization values similar to those shown in Fig. 2 , except that the specimens are shaped as such that they may yield a permeance coefficient (Pc) of 1.
  • Concerning the values of irreversible demagnetization at 200 °C, however, the value of the magnet according to Example 2 of the present invention is improved to -1.9 %, which can be contrasted to the value of -12.9 % for the disclosed magnet. This tendency can be more clearly observed on the specimens shaped to yield Pc 1, as shown in Fig. 3 .
  • the values of irreversible demagnetization at 160 °C for the disclosed magnet is -9.4 %, whereas that for the magnet according to Example 2 of the present invention is improved to -1.7 %; moreover, the values of irreversible demagnetization at 200 °C for the disclosed magnet is -22.3 %, whereas that for the magnet according to Example 2 of the present invention is far improved to -4 %.
  • the present invention provides a permanent magnet alloy having superior heat resistance and oxidation resistance never achieved in the field of R-Fe(Co)-B based magnets. Accordingly, the present invention provides materials having excellent magnetic properties at low cost, which can be advantageously assembled in appliances usable at elevated temperatures.

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Claims (3)

  1. Ein Verfahren zur Herstellung einer Permanentmagnetlegierung mit verbessertem Wärmewiderstand, wobei das Verfahren Folgendes aufweist: Schmelzen und Gießen jedes der Rohmaterialien der Legierungselemente, Pulverisieren der sich ergebenden Legierung, Press- bzw. Kompressionsformung des sich ergebenden Pulvers und Sintern der Form unter einer inerten Gasatmosphäre in einem Temperaturbereich von 1000 bis 1.200°C, um eine gesinterte Magnetlegierung zu erhalten, die ausgedrückt in Atomprozent Folgendes aufweist:
    0,1 bis 15 Atom% C,
    0,5 bis 15 Atom% B,
    vorausgesetzt, dass C und B insgesamt 2 bis 30 Atom% umfassen;
    40 Atom% oder weniger Co (ausschließlich 0%)
    0,3 bis 4,9 Atom% Dy,
    0,1 bis 4,7 Atom% Tb,
    vorausgesetzt, dass Dy und Tb insgesamt 0,5 bis 5 Atom% einnehmen;
    8 bis 20 Atom% R,
    wobei R mindestens ein Element, ausgewählt aus der aus Folgendem bestehenden Gruppe ist: Nd, Pr, Ce, La, Y, Gd, Ho, Er und Tm;
    wobei der Rest Eisen und nicht vermeidbare Verunreinigungen sind;
    dadurch gekennzeichnet, dass
    die Legierung vor der Pulverisierung thermisch unter einer inerten Gasatmosphäre bei einer Temperatur von 600°C oder höher behandelt wird, und
    dass die Pressformung mit einem Formdruck von 1 bis 5 t/cm2 ausgeführt wird, während ein externes Magnetfeld von 15 KOe oder höher angelegt wird.
  2. Verfahren zur Herstellung einer Permanentmagnetlegierung nach Anspruch 1, wobei das Verfahren ferner Folgendes aufweist: Nach dem Sintern der Form unter einer inerten Gasatmosphäre in einem Temperaturbereich von 1000 bis 1.200°C erfolgt das allmähliche Abkühlen der gesinterten Magnetlegierung von der gesinterten bzw. Sinter-Temperatur auf einen Temperaturbereich von 600 bis 900°C, wobei darauf eine Abkühlung (Quentching) erfolgt.
  3. Verfahren zur Herstellung einer Permanentmagnetlegierung gemäß Anspruch 1 oder 2, wobei ein Teil des Rohmaterials von C während des Schmelzens zugegeben wird und wobei der Rest während der Pulverisierung der Legierung zugegeben wird.
EP05017546A 1998-07-29 1999-07-28 Verfahren zur Herstellung einer Permanentmagnetischer Legierung mit hervorragenden wärmeresistenten Eigenschaften Expired - Lifetime EP1607491B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP22752298 1998-07-29
JP22752298 1998-07-29
EP99933132A EP1026279B1 (de) 1998-07-29 1999-07-28 Permanentmagnetische legierung mit hervorragenden waermeresistenten eigenschaften und verfahren zu deren herstellung

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EP1607491A1 EP1607491A1 (de) 2005-12-21
EP1607491B1 true EP1607491B1 (de) 2008-04-02

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EP99933132A Expired - Lifetime EP1026279B1 (de) 1998-07-29 1999-07-28 Permanentmagnetische legierung mit hervorragenden waermeresistenten eigenschaften und verfahren zu deren herstellung

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WO (1) WO2000006792A1 (de)

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US6866740B2 (en) * 2001-11-28 2005-03-15 Masonite Corporation Method of manufacturing contoured consolidated cellulosic panels with variable basis weight
JP4548127B2 (ja) * 2005-01-26 2010-09-22 Ｔｄｋ株式会社 Ｒ−ｔ−ｂ系焼結磁石
ES2563460T3 (es) * 2007-07-27 2016-03-15 Hitachi Metals, Ltd. Imán sinterizado de tierras raras R-Fe-B
RU2572243C1 (ru) * 2014-08-14 2016-01-10 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Астраханский государственный университет" Манганит с гигантским значением константы магнитострикции, стабильным в диапазоне температур
RU2578211C1 (ru) * 2014-10-29 2016-03-27 Федеральное государственное унитарное предприятие "Всероссийский научно-исследовательский институт авиационных материалов" (ФГУП "ВИАМ") Магнитный материал для постоянных магнитов и изделие, выполненное из него
CN104923790B (zh) * 2014-11-25 2018-08-17 安泰科技股份有限公司 一种钆块体材料及其制备方法

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JP2935376B2 (ja) * 1989-12-01 1999-08-16 住友特殊金属株式会社 永久磁石
JP3009687B2 (ja) * 1989-12-15 2000-02-14 住友特殊金属株式会社 高耐食性焼結永久磁石材料の製造方法
JP2740981B2 (ja) * 1990-09-06 1998-04-15 同和鉱業株式会社 不可逆減磁の小さい熱安定性に優れたＲ‐Ｆｅ‐Ｃｏ‐Ｂ‐Ｃ系永久磁石合金
JPH06287720A (ja) * 1993-03-31 1994-10-11 Daido Steel Co Ltd 永久磁石合金
JPH1097907A (ja) * 1996-09-20 1998-04-14 Hitachi Metals Ltd Ｒ−ｔｍ−ｂ系永久磁石の製造方法

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WO2000006792A1 (en) 2000-02-10
JP4034936B2 (ja) 2008-01-16
EP1026279A1 (de) 2000-08-09
CN1274394A (zh) 2000-11-22
DE69927931T2 (de) 2006-07-20
EP1026279A4 (de) 2003-04-09
EP1026279B1 (de) 2005-10-26
DE69938467D1 (de) 2008-05-15
EP1607491A1 (de) 2005-12-21
DE69938467T2 (de) 2009-04-09
HK1032247A1 (en) 2001-07-13
CN1098368C (zh) 2003-01-08
DE69927931D1 (de) 2005-12-01

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