EP0258609B1 - Aimant permanent à bonne stabilité thermique - Google Patents

Aimant permanent à bonne stabilité thermique Download PDF

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Publication number
EP0258609B1
EP0258609B1 EP87110634A EP87110634A EP0258609B1 EP 0258609 B1 EP0258609 B1 EP 0258609B1 EP 87110634 A EP87110634 A EP 87110634A EP 87110634 A EP87110634 A EP 87110634A EP 0258609 B1 EP0258609 B1 EP 0258609B1
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Prior art keywords
magnets
resulting
flux
ihc
coercive force
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EP0258609A3 (en
EP0258609A2 (fr
Inventor
Masaaki Tokunaga
Minoru Endoh
Hiroshi Kogure
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Proterial Ltd
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Hitachi Metals 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
    • 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

Definitions

  • the present invention relates to rare earth permanent magnet materials, particularly to R-Fe-B permanent magnet materials having good thermal stability.
  • R-Fe-B permanent magnet materials have been developed as new compositions having higher magnetic properties than R-Co permanent magnet materials (Japanese Patent Laid-Open Nos. 59-46008, 59-64733 and 59-89401, and M. Sagawa et al, "New Material for Permanent Magnets on a Basis of Nd and Fe," J. Appl. Phys. 55 (6) 2083(1984)).
  • an alloy of Nd15Fe77B8[Nd(Fe 0.91 B 0.09 ) 5.67 ] has such magnetic properties as (BH)max of nearly 280 kJ/m3 and iHc of nearly 800 kA/m.
  • the R-Fe-B magnets have low Curie temperatures, so that they are poor in thermal stability.
  • attempts were made to elevate Curie temperature by adding Co (Japanese Patent Laid-Open No. 59-64733).
  • the R-Fe-B permanent magent has Curie temperature of about 300°C and at highest 370°C (Japanese Patent Laid-Open No. 59-46008), while the substitution of Co for part of Fe in the R-Fe-B magnet serves to increase the Curie temperature to 400-800°C (Japanese Patent Laid-Open No. 59-64733).
  • the addition of Co decreases the coercive force iHc of the R-Fe-B magnet.
  • Permanent magnets having compositions partly overlapping with those of claim 1 are disclosed in EP-A-216254 and EP-A-248981.
  • An object of the present invention is, therefore, to provide an R-Fe-B permanent magnet with raised Curie temperature and sufficient coercive force and thus improved thermal stability.
  • the permanent magnet having good thermal stability consists essentially of a composition represented by the general formula: R(Fe 1-x-y-z Co x B y Ga z ) A wherein R is Nd alone or one or more rare earth elements mainly composed of Nd, Pr or Ce, 0 ⁇ x ⁇ 0.7, 0.02 ⁇ y ⁇ 0.3, 0.001 ⁇ z ⁇ 0.15, and 4.0 ⁇ A ⁇ 7.5.
  • the amount of Co represented by "x" is 0-0.7. When it exceeds 0.7, the residual magnetic flux density Br of the resulting magnet becomes too low.
  • the lower limit of Co is preferably 0.01, and to have a well-balanced combination of such magnetic properties as iHc and Br and Tc, the upper limit of Co is preferably 0.4.
  • the most preferred amount of Co is 0.05-0.25.
  • the addition of Ga leads to remarkable improvement of coercive force. This improvement appears to be provided by increasing the Curie temperature of a BCC phase in the magnet.
  • the BCC phase is a polycrystalline phase having a body-centered cubic crystal structure surrounding in a width of 10-500nm a main phase of the Nd-Fe-B magnet (Nd2Fe14B). This BCC phase is in turn surrounded by a Nd-rich phase (Nd: 70-95 at. % and balance Fe).
  • the Curie temperature of this BCC phase corresponds to a temperature at which the coercive force of the magnet becomes lower than 50 Oe, greatly affecting the temperature characteristics of the magnet.
  • the addition of Ga serves to raise the Curie temperature of the BCC phase, effective for improving the temperature characteristics.
  • the amount of Ga represented by “z” is 0.001-0.15. When it is less than 0.001, substantially no effect is obtained on improving the Curie temperature of the magnet. On the other hand, when “z” exceeds 0.15, extreme decrease in saturation magnetization and Curie temperature ensues, providing undesirable permanent magnet materials.
  • the preferred amount of Ga is 0.002-0.10, and the most preferred amount of Ga is 0.005-0.05.
  • the amount of B When the amount of boron represented by "y" is less than 0.02, Curie temperature is low and high coercive force cannot be obtained. On the other hand, when the amount of B "y” is higher than 0.3, the saturation magnetization are decreased, forming phases undesirable to magnetic properties. Accordingly, the amount of B should be 0.02-0.3. The preferred range of "y” is 0.03-0.20. The most preferred amount of B is 0.04-0.15.
  • the permanent magnet of the present invention may further contain an additional element generally represented by "M" in the following formula: R(Fe l-x-y-z-u Co x B y Ga z M u ) A wherein R is Nd alone or one or more rare earth elements mainly composed of Nd, Pr or Ce, part of which may be substituted by Dy, Tb or Ho, M is one or more elements selected from Nb, W, V, Ta and Mo, 0 ⁇ x ⁇ 0.7, 0.02 ⁇ y ⁇ 0.3, 0.001 ⁇ z ⁇ 0.15, 0.001 ⁇ u ⁇ 0.1, and 4.0 ⁇ A ⁇ 7.5.
  • M is one or more elements selected from Nb, W, V, Ta and Mo, 0 ⁇ x ⁇ 0.7, 0.02 ⁇ y ⁇ 0.3, 0.001 ⁇ z ⁇ 0.15, 0.001 ⁇ u ⁇ 0.1, and 4.0 ⁇ A ⁇ 7.5.
  • Nb, W, V, Ta or Mo is added to prevent the grain growth.
  • the amount of these elements represented by "u" is 0.001-0.1. When it is less than 0.001, sufficient effects cannot be obtained, and when it exceeds 0.1, the saturation magnetization is extremely decreased, providing undesirable permanent magnets.
  • Nb does not decrease Br as much as the addition of Ga does, while it slightly increases iHc.
  • Nb is effective for increasing corrosion resistance, and so in the case of highly heat-resistant alloys likely to be exposed to relatively high temperatures, it is a highly effective additive.
  • u the amount of Nb represented by "u"
  • u the amount of Nb represented by "u"
  • u the amount of Nb represented by "u"
  • u the amount of Nb represented by "u"
  • u When the amount of Nb represented by "u" is less than 0.001, sufficient effects of increasing iHc cannot be achieved, neither does the magnet alloy have sufficiently high corrosion resistance.
  • the amount of Nb exceeds 0.1, undesirably large decrease in Br and Curie temperature ensues.
  • the preferred range of Nb is 0.002 ⁇ z ⁇ 0.04.
  • tungsten serves to extremely improve the temperature characteristics.
  • W("u) exceeds 0.1, the saturation magnetization and the coercive force are extremely decreased. And when "u" is less than 0.001, sufficient effects cannot be obtained.
  • the preferred amount of W is 0.002-0.04.
  • the rare earth element "R” it may be Nd alone, or a combination of Nd and a light rare earth element such as Pr or Ce, or Pr plus Ce.
  • a light rare earth element such as Pr or Ce, or Pr plus Ce.
  • Pr and/or Ce are contained, the proportion of Pr to Nd may be 0:1 - 1:0, and that of Ce to Nd may be 0:1 - 0.3:0.7.
  • Nd may also be substituted by Dy which acts to somewhat raise Curie temperature and enhance coercive force iHc.
  • Dy acts to somewhat raise Curie temperature and enhance coercive force iHc.
  • the addition of Dy is effective to improve the thermal stability of the permanent magnet of the present invention.
  • an excess amount of Dy leads to the decrease in residual magnetic flux density Br.
  • the proportion of Dy to Nd should be 0.03:0.97-0.4:0.6 by atomic ratio.
  • the preferred atomic ratio of Dy is 0.05-0.25 .
  • the permanent magnet of the present invention can be produced by a powder metallurgy method, a rapid quenching method or a resin bonding method. These methods will be explained below.
  • a magnet alloy is obtained by arc melting or high-frequency melting.
  • the purity of starting materials may be 90% or more for R, 95% or more for Fe, 95% or more for Co, 90% or more for B, 95% or more for Ga and 95% or more for M(Nb, W, V, Ta, Mo), if any.
  • a starting material for B may be ferroboron and a starting material for Ga may be ferrogallium.
  • a starting material for M(Nb, W, V, Ta, Mo) may be ferroniobium, ferrotungsten, ferrovanadium, ferrotantalum or ferromolybdenum. Since the ferroboron and the ferrogallium contain inevitable impurities such as Al and Si, high coercive force can be obtained by synergistic effect of such elements as Ga, Al and Si.
  • Pulverization may be composed of the steps of pulverization and milling.
  • the pulverization may be carried out by a stamp mill, a jaw crusher, a brown mill, a disc mill, etc., and the milling may be carried out by a jet mill, a vibration mill, a ball mill, etc.
  • the pulverization is preferably carried out in a non-oxidizing atmosphere to prevent the oxidation of the alloy.
  • the final particle size is desirably 2-5 ⁇ m (FSSS).
  • the resulting fine powders are pressed in a magnetic field by a die. This is indispensable for providing the alloy with anisotropy that the magnet powders to be pressed have C axes aligned in the same direction.
  • Sintering is carried out in an inert gas such as Ar, He, etc., or in vacuum, or in hydrogen at 1050°C-1150°C.
  • Heat treatment is carried out on the sintered magnet alloy at 400°C-1000°C.
  • a magnet alloy is prepared in the same manner as in the powder metallurgy method (1).
  • a melt of the resulting alloy is rapidly quenched by a single-roll or double-roll quenching apparatus. That is, the alloy melted, for instance, by high frequency is ejected through a nozzle onto a roll rotating at a high speed, thereby rapidly quenching it.
  • the resulting flaky products are heat-treated at 500-800°C. Materials provided by this rapid quenching method may be used for three kinds of permanent magnets.
  • the starting material may be an R-Fe-Co-B-Ga alloy obtained in the above (1), sintered bodies obtained by pulverization and sintering of the above alloy, rapidly quenched flakes obtained in the above (2), or bulky products obtained by hot-pressing or upsetting the flakes. These bulky products are pulverized to 30-500 ⁇ m in particle size by a jaw crusher, a brown mill, a disc mill, etc. The resulting fine powders are mixed with resins and formed by die molding or injection molding. The application of a magnetic field during the molding operation provides anisotropic magnets in which their C axes are aligned in the same direction.
  • starting materials used were 99.9%-pure Nd, 99.9%-pure Fe, 99.9%-pure Co, 99.5%-pure B, 99.9999%-pure Ga, 99.9%-pure Nb and 99.9%-pure W, and all other elements used were as pure as 99.9% or more.
  • Alloys of the compositions Nd(Fe 0.82 Co 0.1 B 0.07 Ga 0.01 ) 6.5 and Nd(Fe 0.93 B 0.07 ) 6.5 were prepared by arc melting. The resulting alloys were rapidly quenched from their melts by a single roll method. The resulting flaky materials were heat-treated at 700°C for 1 hour. The samples thus prepared were pulverized to about 100 ⁇ m by a disc mill. The resulting coarse powders of each composition were separated into two groups: (a) one was blended with an epoxy resin and molded by a die, and (b) the other was hot-pressed. The magnetic properties of each of the resulting magnets are shown in Table 7.
  • the iHc was as high as 1600 kA/m or more, thus providing magnets with good thermal stability.
  • Alloys having the compositions: Nd(Fe 0.82 Co 0.1 B 0.07 Ga 0.01 ) 5.4 and Nd(Fe 0.92 B 0.08 ) 5.4 were prepared by arc melting.
  • the resulting alloys were processed in two ways: (a) one was pulverized to 50 ⁇ m or less, and (b) the other was rapidly quenched from its melt by a single roll method, and the resulting flaky product was subjected to hot isotropic pressing (HIP) and made flat by upsetting, and thereafter pulverized to 50 ⁇ m or less.
  • HIP hot isotropic pressing
  • An alloy having the composition of (Nd 0.8 Dy 0.2 )(Fe 0.835 Co 0.06 B 0.08 Nb 0.015 Ga 0.01 ) 5.5 was formed into an ingot by high-frequency melting.
  • the resulting alloy ingot was coarsely pulverized by a stamp mill and a disc mill, and then finely pulverized in a nitrogen gas as a pulverization medium to provide fine powders of 3.5- ⁇ m particle size (FSSS).
  • the fine powders were pressed in a magnetic field of 1200 kA/m perpendicular to the compressing direction.
  • the compression pressure was 2000 kbar.
  • the resulting green bodies were sintered at 1100°C for 2 hours in vacuo, and then cooled to room temperature in a furnace. A number of the resulting sintered alloys were heated at 900°C for 2 hours and then slowly cooled at 1.5°C/min. to room temperature.
  • an alloy of (Nd 0.8 Dy 0.2 )(Fe 0.86 Co 0.06 B 0.08 ) 5.5 was prepared in the same manner as above.
  • the annealing temperature was 600°C.
  • the magnetic properties of the resulting magnet were as follows: Br of nearly 1.12 T, bHc of nearly 852 kA/m, iHc of nearly 1910 kA/m and (BH)max of nearly 273 kJ/m3.
  • Each of the resulting green bodies was sintered in vacuum at 1090°C for 1 hour, and then heat-treated at 900°C for 2 hours, and thereafter cooled down to room temperature at a rate of 1°C/min. It was again heated for annealing in an Ar gas flow at 600°C for 1 hour and rapidly cooled in water. Magnetic properties were measured on each sample. The results are shown in Tables 11(a)-(c).
  • the irreversible loss of flux by heating is also shown in Tables 12(a)-(c).
  • the increase in the Co content leads to the decrease in iHc without substantially changing (BH)max.
  • the irreversible loss of flux becomes larger with the increase in the Co content.
  • the amount of Co is 0.06, the highest heat resistance can be provided.
  • the comparison of these three types of alloys shows that those containing both Ga and Nb have the highest heat resistance.
  • Alloys represented by the compositions of Nd(Fe 0.86 Co 0.06 B 0.08 ) 5.6 , Nd(Fe 0.84 Co 0.06 B 0.08 Ga 0.02 ) 5.6 , and Nd(Fe 0.825 Co 0.06 B 0.08 Ga 0.02 W 0.015 ) 5.6 were prepared by arc melting.
  • the resulting ingots were coarsely pulverized by a stamp mill and a disc mill, and after sieving to finer than 32 mesh milling was carried out by a jet mill.
  • a pulverization medium was an N2 gas, and fine powders of 3.5 ⁇ m in particle size (FSSS) were obtained.
  • the resulting powders were formed in a magnetic field of 1200 kA/m whose direction was perpendicular to the pressing direction. Press pressure was 2000 kbar.
  • the resulting green bodies were sintered in vacuum at 1080°C for two hours. Heat treatment was carried out at 500-900°C for one hour, followed by quenching. The results are shown in Table 19.
  • Table 20 Magnetic Properties of Nd(Fe 0.85-z Co 0.06 B 0.08 Ga z W 0.01 ) 5.4 Magnets z 4 ⁇ Ir(T) iHc (KOe)(kA/m) (BH)max(kJ/m3) 0 1.26 995 301 0.01 1.232 1210 285 0.02 1.206 1385 276 0.03 1.177 1473 263 0.04 1.152 1568 252 0.05 1.129 1671 233
  • Table 21 Magnetic Properties of Nd(Fe 0.825 Co 0.06 B 0.08 Ga 0.02 W 0.015 ) 6.0 Magnets Method 4 ⁇ Ir (T) iHc (kA/m) (BH)max(kJ/m3) (a) 0.6 1799 57 (b) 0.8 1608 100 (c) 1.24 1266 287
  • the resulting ingots were coarsely pulverized by a stamp mill and a disc mill, and after sieving to finer than 32 mesh milling was carried out by a jet mill.
  • a pulverisation medium was an N2 gas, and fine powders of 3.5 ⁇ m in particle size (FSSS) were obtained.
  • the resulting powders were formed in a magnetic field of 1200 kA/m whose direction was perpendicular to the pressing direction. Press pressure was 1500 kbar.
  • the resulting green bodies were sintered in vacuum at 1040°C for two hours. Heat treatment was carried out at 600-700°C for one hour, followed by quenching. The results are shown in Fig. 6.
  • the magnets containing Ga had higher coercive force and smaller decrease in 4 ⁇ Ir and (BH)max than those containing Dy or Al.
  • the variation of magnetic flux with temperature has two inflection points; one on the side of lower temperature corresponding to the Curie temperature of the BCC phase, and the other on the side of higher temperature corresponding to the Curie temperature of the main phase.
  • the magnets with Ga have lower Curie temperatures in their main phases than those containing no additive.
  • the former is higher than the latter.
  • the addition of Al greatly decreases the Curie temperatures of the main phase and of the BCC phase, providing undesirable thermal stability.
  • Example 16 pulverization, milling, sintering and heat treatment were carried out in the same mannner as in Example 16 on alloys having the compositions: Nd(Fe 0.67 Co 0.25 B 0.08 ) 5.6 , Nd(Fe 0.65 Co 0.25 B 0.08 Ga 0.02 ) 5.6 , and Nd(Fe 0.635 Co 0.25 B 0.08 Ga 0.02 W 0.015 ) 5.6 .
  • the magnetic properties of the resulting magnets are shown in Table 22.
  • the addition of Ga or Co and Ga together to Nd-Fe-B magnets increases Curie temperature and coercive force of the magnets, thereby providing magnets with better thermal stability.
  • M one or more of Nb, W, V, Ta, Mo

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  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
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Claims (2)

  1. Aimant permanent fritté présentant une bonne stabilité thermique, comportant une phase principale à structure tétragonale et une phase magnétique riche en R, et essentiellement constitué de la composition représentée par la formule générale:



            R(Fe1-x-y-zCoxByGaz)A



    où R est principalement composé de Nd; 0,01 < x < 0,4, 0,03 < y < 0,2, 0,02 < z < 0,1, et 4,0 < A < 7,5.
  2. Aimant permanent de la revendication 1 dans lequel R est Nd, dont une partie est remplacée par Pr t/ou Ce, et dans lequel 4,5 ≦ A ≦ 7,0.
EP87110634A 1986-07-23 1987-07-22 Aimant permanent à bonne stabilité thermique Expired - Lifetime EP0258609B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP90121313A EP0421488B1 (fr) 1986-07-23 1987-07-22 Aimant permanent à bonne stabilité thermique

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
JP172987/86 1986-07-23
JP17298786 1986-07-23
JP185905/86 1986-08-07
JP18590586 1986-08-07
JP243490/86 1986-10-14
JP24349086 1986-10-14
JP85787/87 1987-01-06
JP85787 1987-01-06

Related Child Applications (1)

Application Number Title Priority Date Filing Date
EP90121313.2 Division-Into 1990-11-07

Publications (3)

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EP0258609A2 EP0258609A2 (fr) 1988-03-09
EP0258609A3 EP0258609A3 (en) 1989-04-26
EP0258609B1 true EP0258609B1 (fr) 1993-02-03

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EP90121313A Expired - Lifetime EP0421488B1 (fr) 1986-07-23 1987-07-22 Aimant permanent à bonne stabilité thermique

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EP (2) EP0258609B1 (fr)
JP (1) JP2751109B2 (fr)
KR (1) KR910001065B1 (fr)
CN (1) CN1036554C (fr)
DE (2) DE3750661T2 (fr)

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JPS647503A (en) 1989-01-11
EP0421488B1 (fr) 1994-10-12
EP0258609A3 (en) 1989-04-26
DE3750661D1 (de) 1994-11-17
EP0258609A2 (fr) 1988-03-09
DE3783975T2 (de) 1993-05-27
CN1036554C (zh) 1997-11-26
CN87105186A (zh) 1988-02-03
DE3750661T2 (de) 1995-04-06
KR910001065B1 (ko) 1991-02-23
EP0421488A3 (en) 1991-08-28
EP0421488A2 (fr) 1991-04-10
DE3783975D1 (de) 1993-03-18
KR880002202A (ko) 1988-04-29
JP2751109B2 (ja) 1998-05-18

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