EP0466246B1 - Method of manufacturing an isotropic permanently magnetic material, isotropic permanently magnetic material and synthetic resin-bound isotropic permanent magnet - Google Patents
Method of manufacturing an isotropic permanently magnetic material, isotropic permanently magnetic material and synthetic resin-bound isotropic permanent magnet Download PDFInfo
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- EP0466246B1 EP0466246B1 EP91201692A EP91201692A EP0466246B1 EP 0466246 B1 EP0466246 B1 EP 0466246B1 EP 91201692 A EP91201692 A EP 91201692A EP 91201692 A EP91201692 A EP 91201692A EP 0466246 B1 EP0466246 B1 EP 0466246B1
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- Prior art keywords
- isotropic
- magnetic material
- permanently magnetic
- alloy
- coercive force
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- 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.)
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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
- H01F1/058—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IVa elements, e.g. Gd2Fe14C
Definitions
- the invention relates to a method of manufacturing an isotropic, permanently magnetic material which comprises Nd and/or Pr, Fe and C, the constituents of the material being melted together to form an alloy which is subsequently subjected to a thermal treatment, so that phase transformation takes place.
- the invention also relates to an isotropic, permanently magnetic material and to a synthetic resin-bound isotropic permanent magnet.
- a method of the type mentioned in the opening paragraph is known per se .
- European Patent Application with publication number 320.064 a description is given of a method in which an alloy of Nd2Fe14C is subjected to a thermal treatment at 870°C for 500 hours to bring about a phase transformation.
- the tetragonal "2-14-1" crystal structure is formed which is characteristic of the hard magnetic phase of the known Nd2Fe14B compound.
- the thermal treatment must take place in a relatively small temperature range of 840°C to 890°C. Above 890°C, said tetragonal crystal structure is not formed. If the thermal treatment takes place at a temperature below 840°C, an impermissibly large quantity of Nd2Fe17 is formed in addition to the desired tetragonal phase.
- the known method has disadvantages. It has been found that the magnetic material manufactured by said method has hardly any or no coercive force (H c ) after the phase transformation. The value of the coercive force is smaller than 50 kA/m. Due to said small coercive force the known material is not very suitable for use in synthetic resin-bound isotropic permanent magnets.
- One of the objects of the invention is to improve the known method.
- the invention is more particularly aimed at providing a method of manufacturing an isotropic, permanently magnetic material of the type mentioned in the opening paragraph, which material has coercive force.
- the invention provides an isotropic, permanently magnetic material having a substantially single-phase crystal structure and a coercive force of at least 150 kA/m.
- the magnetic material should further have a high saturation magnetization.
- a further object of the invention is to provide a synthetic resin-bound isotropic permanent magnet.
- the alloy comprises 10-20 at.% of Nd and/or Pr, 70-85 at.% of Fe, 4-11 at.% of C and 0.1-2 at.% of B, and in that the thermal treatment takes place at a temperature between 900°C and 1050°C.
- the invention is based on, inter alia, the experimentally gained insight that the temperature range in which phase transformation takes place can be considerably extended by substituting a small quantity of C of the known Nd2Fe14C by B.
- phase transformation only takes place in the range from 840°C to 890°C, yet in the case of the material according to the invention the formation of the tetragonal phase takes place in the temperature range from 800 to 1050°C.
- the thermal treatment is carried out at 900-1050°C, the material exhibits a coercive force of at least 150 kA/m.
- the rare earth metal content in the alloy should consist exclusively or almost exclusively of Nd and/or Pr. This provides the magnetic material according to the inventive method with a high saturation magnetization. A small quantity of other rare earth metals (up to 10 at.%) may be suitable to influence certain magnetic properties of the material. Preferably, however, the material comprises only Nd as the rare earth metal. In this manner, the highest saturation magnetization is attained.
- the isotropic, permanently magnetic material obtained according to the inventive method comprises exclusively or substantially exclusively Fe as the transition metal. Under certain conditions it might be advantageous for the material to also comprise a small quantity of Co as the transition metal (up to 10 at.%). Co increases the Curie temperature and the corrosion resistance of the magnetic material. Co-containing magnets can moreover be oriented at much smaller fields than magnets containing only Fe as the transition metal. In the case of the latter magnets, fields of at least 5 T are required. Co-containing magnets can already be optimally oriented at 2.0 T. If, however, a maximum saturation magnetization is aimed at, only Fe is to be used as the transition metal.
- B takes up the lattice site of C in the crystallized "Nd2Fe14C"-structure.
- the molar quantity of B is at least 2.5 % of the overall content of B and C.
- the molar quantity of B is maximally 15 % of the overall content of B and C.
- recrystallization results in multiphase material being formed. This is regarded as a disadvantage.
- R2Fe14CxB 1-x -compounds are known from Fig. 1 of J. Appl. Phys. 61 3574 (1987).
- R denotes a rare earth metal.
- a range is indicated in which the Fe77R15(B, C)8-compounds form a continuous series.
- compositions which comprise only Nd as the rare earth metal and which, in addition to C comprise a small quantity of B. These compounds, however, have been subjected to a thermal treatment at 800°C and, consequently, have no appreciable coercive force.
- An interesting embodiment of the method according to the invention is characterized in that the alloy is subjected to the thermal treatment for maximally 4 days.
- a heat treatment of at least approximately one week is necessary to bring about the desired tetragonal crystal structure in the alloy. With a view to an economical production, such long thermal treatments are undesirable.
- a further advantageous embodiment of the method according to the invention is characterized in that the alloy is ground to form a magnetic powder having an average particle size of 2 to 40 »m. It has been found that the coercive force of the magnetic material increases considerably when, following the thermal treatment, the alloy is ground to form a magnetic powder having an average particle size of 2-40 »m.
- the grinding operation is carried out in, for example, a ball mill. After grinding, magnetic powders are obtained having a H c of at least 500 kA/m.
- the invention further relates to an isotropic permanently magnetic material.
- said material is characterized in that it comprises 10-20 at.% of Nd and/or Pr, 70-85 at.% of Fe, 4-11 at.% of C and 0.1-2 at.% of B, and in that the material has a coercive force of at least 150 kA/m.
- Said material is preferably powderous and has an average particle size of 2-40 »m and a coercive force of at least 500 kA/m. Such a powder can be advantageously used in a synthetic resin-bound, isotropic, permanent magnet.
- the invention further relates to a synthetic resin-bound, isotropic, permanent magnet.
- said magnet is characterized in that it comprises an isotropic, permanently magnetic material which is composed of 10-20 at.% of Nd and/or Pr, 70-85 at.% of Fe, 4-11 at.% of C and 0.1-2 at.% B, and which is powderous with an average particle size in the range between 2 and 40 »m, and in that the material has a coercive force of at least 500 kA/m.
- Fig. 1 shows the maximum temperature T(°C) at which the isotropic, magnetic material Nd2Fe14C 1-x B x or Pr2Fe14C 1-x B x can be formed as a function of the B-content x.
- Fig. 2 shows the effect of the grinding time t(min.) on the coercive force H c (kA/m) of an alloy of composition Nd15Fe77C 7.68 B 0.32 .
- Fig. 3 shows a hysteresis loop of a magnetic alloy of the composition Nd16Fe75C 8.55 B 0.45 .
- a number of alloys comprising 10-20 at.% of Nd and/or Pr, 70-85 at.% of Fe, 4-11 at.% of C and 0.1-2 at.% of B was manufactured.
- a mixture of the constituents in the desired ratio was melted together by means of an arc at approximately 1800°C.
- the alloys were subsequently sealed into glass capsules under a vacuum and then subjected to a thermal treatment to bring about phase transformation. The duration and the temperature of the thermal treatment were varied. X-ray analysis showed that the crystallized alloys were substantially completely single-phase and exhibited a tetragonal structure. The coercive force of the unground alloys was determined.
- the alloys were subsequently ground in a ball mill, under an inert atmosphere (nitrogen or vacuum), to form a powder having an average particle size ranging between 2 and 40 »m.
- the variation of the H c as a function of the grinding duration was investigated.
- the ground powders were fixed in a synthetic resin.
- the powder particles were oriented by means of a magnetic field.
- the alloys 1-9 were oriented using a field of 5 T.
- the alloys 10-12 were oriented using a field of 2.0 T.
- the H c of these magnets was measured by means of a vibrating sample magnetometer.
- the Table shows a number of compositions and properties of the alloys which were manufactured by the method according to the invention.
- Column 1 lists the number of the exemplary embodiment.
- Column 2 lists the composition of the alloys.
- the duration (days) and the temperature (°C) of the thermal treatment are listed in column 3 and column 4, respectively.
- the coercive force (kA/m) of the recrystallized alloy before and after the grinding operation are listed in column 5 and column 6, respectively.
- the grinding operation took place in a ball mill for 10-20 minutes, until an average grain size was attained which ranges between 2 and 40 »m.
- Column 7 lists the saturation magnetization (emu/g) of the synthetic resin-bound isotropic permanent magnets obtained by fixing the powder in wax.
- the energy product B.H max of the magnets based on alloys 10-12 was approximately 70 kJ/m3.
- Fig. 1 shows the effect of a small substitution of C by B in Nd2Fe14C on the maximum transformation temperature. Above the line shown, the intended tetragonal phase is not achieved. When approximately 2.5% of B is added, related to the overall content of C and B, it is found that the maximum transformation temperature has risen from 890°C to 1050°C.
- Fig. 2 shows the effect of grinding (duration t in min.) on the coercive force (H c , kA/m) of an alloy obtained according to the inventive method (exemplary embodiment 2).
- the grinding operation almost tripled the coercive force.
- the Figure further shows that too long a grinding treatment adversely affects the coercive force of the powder.
- Fig. 3 shows the hysteresis loop of a magnetic alloy having the composition Nd16Fe75C 8.55 B 0.45 at a magnetic field of 5 T.
- the alloy was heated at 950°C for 1 day.
- the remanence was 0.65 T.
Description
- The invention relates to a method of manufacturing an isotropic, permanently magnetic material which comprises Nd and/or Pr, Fe and C, the constituents of the material being melted together to form an alloy which is subsequently subjected to a thermal treatment, so that phase transformation takes place. The invention also relates to an isotropic, permanently magnetic material and to a synthetic resin-bound isotropic permanent magnet.
- A method of the type mentioned in the opening paragraph is known per se. For example, in European Patent Application with publication number 320.064, a description is given of a method in which an alloy of Nd₂Fe₁₄C is subjected to a thermal treatment at 870°C for 500 hours to bring about a phase transformation. In this thermal treatment, the tetragonal "2-14-1" crystal structure is formed which is characteristic of the hard magnetic phase of the known Nd₂Fe₁₄B compound. In the case of Nd₂Fe₁₄C, the thermal treatment must take place in a relatively small temperature range of 840°C to 890°C. Above 890°C, said tetragonal crystal structure is not formed. If the thermal treatment takes place at a temperature below 840°C, an impermissibly large quantity of Nd₂Fe₁₇ is formed in addition to the desired tetragonal phase.
- The known method has disadvantages. It has been found that the magnetic material manufactured by said method has hardly any or no coercive force (Hc) after the phase transformation. The value of the coercive force is smaller than 50 kA/m. Due to said small coercive force the known material is not very suitable for use in synthetic resin-bound isotropic permanent magnets.
- One of the objects of the invention is to improve the known method. The invention is more particularly aimed at providing a method of manufacturing an isotropic, permanently magnetic material of the type mentioned in the opening paragraph, which material has coercive force. According to a further object, the invention provides an isotropic, permanently magnetic material having a substantially single-phase crystal structure and a coercive force of at least 150 kA/m. The magnetic material should further have a high saturation magnetization. A further object of the invention is to provide a synthetic resin-bound isotropic permanent magnet.
- These and other objects are achieved by a method of the type mentioned in the opening paragraph, which is characterized according to the invention in that the alloy comprises 10-20 at.% of Nd and/or Pr, 70-85 at.% of Fe, 4-11 at.% of C and 0.1-2 at.% of B, and in that the thermal treatment takes place at a temperature between 900°C and 1050°C.
- The invention is based on, inter alia, the experimentally gained insight that the temperature range in which phase transformation takes place can be considerably extended by substituting a small quantity of C of the known Nd₂Fe₁₄C by B. In the known Nd₂Fe₁₄C, phase transformation only takes place in the range from 840°C to 890°C, yet in the case of the material according to the invention the formation of the tetragonal phase takes place in the temperature range from 800 to 1050°C. Surprisingly, it has further been found that when the thermal treatment is carried out at 900-1050°C, the material exhibits a coercive force of at least 150 kA/m. When the thermal treatment takes place at temperatures between 800°C and 900°C, an isotropic permanently magnetic material is obtained having a coercive force which is smaller than 150 kA/m. When the thermal treatment is carried out at temperatures above 1050°C hardly any or no tetragonal phase is obtained.
- The rare earth metal content in the alloy should consist exclusively or almost exclusively of Nd and/or Pr. This provides the magnetic material according to the inventive method with a high saturation magnetization. A small quantity of other rare earth metals (up to 10 at.%) may be suitable to influence certain magnetic properties of the material. Preferably, however, the material comprises only Nd as the rare earth metal. In this manner, the highest saturation magnetization is attained.
- The isotropic, permanently magnetic material obtained according to the inventive method comprises exclusively or substantially exclusively Fe as the transition metal. Under certain conditions it might be advantageous for the material to also comprise a small quantity of Co as the transition metal (up to 10 at.%). Co increases the Curie temperature and the corrosion resistance of the magnetic material. Co-containing magnets can moreover be oriented at much smaller fields than magnets containing only Fe as the transition metal. In the case of the latter magnets, fields of at least 5 T are required. Co-containing magnets can already be optimally oriented at 2.0 T. If, however, a maximum saturation magnetization is aimed at, only Fe is to be used as the transition metal.
- As mentioned above, the presence of a relatively small quantity of B in the magnetic material is essential for the inventive method. B takes up the lattice site of C in the crystallized "Nd₂Fe₁₄C"-structure. The molar quantity of B is at least 2.5 % of the overall content of B and C. At a smaller content of B, the tetragonal phase is insufficiently formed by recrystallization in the temperature range of 900-1050°C. The molar quantity of B is maximally 15 % of the overall content of B and C. At a larger quantity of B, recrystallization results in multiphase material being formed. This is regarded as a disadvantage.
- It is noted that a large number of R₂Fe₁₄CxB1-x-compounds are known from Fig. 1 of J. Appl. Phys. 61 3574 (1987). R denotes a rare earth metal. In said Figure, a range is indicated in which the Fe₇₇R₁₅(B, C)₈-compounds form a continuous series. In the Figure several compositions are given which comprise only Nd as the rare earth metal and which, in addition to C comprise a small quantity of B. These compounds, however, have been subjected to a thermal treatment at 800°C and, consequently, have no appreciable coercive force.
- Further, it is noted that in Mat. Lett. 4 378 (1986) a description is given of the compound Fe₇₇Nd₉Dy₆C7.2B0.8 which has a Hc of 12.5 kOe. It is known per se that the rare earth metal Dy provides a considerable coercive force to tetragonal 2-14-1-compounds of the type R₂Fe₁₄B.
- An interesting embodiment of the method according to the invention is characterized in that the alloy is subjected to the thermal treatment for maximally 4 days. In the case of the method known from EP 320.064, a heat treatment of at least approximately one week is necessary to bring about the desired tetragonal crystal structure in the alloy. With a view to an economical production, such long thermal treatments are undesirable.
- A further advantageous embodiment of the method according to the invention is characterized in that the alloy is ground to form a magnetic powder having an average particle size of 2 to 40 »m. It has been found that the coercive force of the magnetic material increases considerably when, following the thermal treatment, the alloy is ground to form a magnetic powder having an average particle size of 2-40 »m. The grinding operation is carried out in, for example, a ball mill. After grinding, magnetic powders are obtained having a Hc of at least 500 kA/m.
- The invention further relates to an isotropic permanently magnetic material. According to the invention, said material is characterized in that it comprises 10-20 at.% of Nd and/or Pr, 70-85 at.% of Fe, 4-11 at.% of C and 0.1-2 at.% of B, and in that the material has a coercive force of at least 150 kA/m. Said material is preferably powderous and has an average particle size of 2-40 »m and a coercive force of at least 500 kA/m. Such a powder can be advantageously used in a synthetic resin-bound, isotropic, permanent magnet.
- The invention further relates to a synthetic resin-bound, isotropic, permanent magnet. According to the invention, said magnet is characterized in that it comprises an isotropic, permanently magnetic material which is composed of 10-20 at.% of Nd and/or Pr, 70-85 at.% of Fe, 4-11 at.% of C and 0.1-2 at.% B, and which is powderous with an average particle size in the range between 2 and 40 »m, and in that the material has a coercive force of at least 500 kA/m.
- The invention will be explained in greater detail by means of exemplary embodiments and with reference to the accompanying drawing, in which
- Fig. 1 shows the maximum temperature T(°C) at which the isotropic, magnetic material Nd₂Fe₁₄C1-xBx or Pr₂Fe₁₄C1-xBx can be formed as a function of the B-content x.
- Fig. 2 shows the effect of the grinding time t(min.) on the coercive force Hc (kA/m) of an alloy of composition Nd₁₅Fe₇₇C7.68B0.32.
- Fig. 3 shows a hysteresis loop of a magnetic alloy of the composition Nd₁₆Fe₇₅C8.55B0.45.
- A number of alloys comprising 10-20 at.% of Nd and/or Pr, 70-85 at.% of Fe, 4-11 at.% of C and 0.1-2 at.% of B was manufactured. For this purpose, a mixture of the constituents in the desired ratio was melted together by means of an arc at approximately 1800°C. The alloys were subsequently sealed into glass capsules under a vacuum and then subjected to a thermal treatment to bring about phase transformation. The duration and the temperature of the thermal treatment were varied. X-ray analysis showed that the crystallized alloys were substantially completely single-phase and exhibited a tetragonal structure. The coercive force of the unground alloys was determined.
- The alloys were subsequently ground in a ball mill, under an inert atmosphere (nitrogen or vacuum), to form a powder having an average particle size ranging between 2 and 40 »m. For several alloys the variation of the Hc as a function of the grinding duration was investigated. For this purpose, the ground powders were fixed in a synthetic resin. During the fixing operation, the powder particles were oriented by means of a magnetic field. The alloys 1-9 were oriented using a field of 5 T. The alloys 10-12 were oriented using a field of 2.0 T. The Hc of these magnets was measured by means of a vibrating sample magnetometer.
- The Table shows a number of compositions and properties of the alloys which were manufactured by the method according to the invention.
Column 1 lists the number of the exemplary embodiment.Column 2 lists the composition of the alloys. The duration (days) and the temperature (°C) of the thermal treatment are listed in column 3 and column 4, respectively. The coercive force (kA/m) of the recrystallized alloy before and after the grinding operation are listed incolumn 5 and column 6, respectively. The grinding operation took place in a ball mill for 10-20 minutes, until an average grain size was attained which ranges between 2 and 40 »m. Column 7 lists the saturation magnetization (emu/g) of the synthetic resin-bound isotropic permanent magnets obtained by fixing the powder in wax. The energy product B.Hmax of the magnets based on alloys 10-12 was approximately 70 kJ/m³. - A number of alloys having the general composition Nd₁₆Fe₇₅(C1-xBx)₉ were subjected to closer investigation. As described above, the alloys were manufactured by arc melting. Subsequently, they were subjected to a heat treatment at 900°C for 5.5 days. The measured coercive force (Hc) values of these alloys were 290 kA/m (x=0.01); 430 kA/m (x=0.03); 500 kA/m (x=0.05) and 440 kA/m (x=0.1). At values of x=0 and x=0.25, the Hc of the alloys was smaller than 150 kA/m.
- Further, a number of alloys having the general formula Nd₁₆Fe74-xCoxC9.5B0.5 were manufactured by arc melting. In said alloys the value of x was varied between 0 and 10. It was found that after annealing and orienting the Co-containing alloys, the coercive force of said alloys was much higher than that of similar alloys which do not contain Co. Besides, the Co-containing magnets could be optimally oriented with a magnetic field of 2.0 T. Similar magnets which do not contain Co require fields of at least 5.0 T. Moreover, the duration of the necessary annealing treatment was shorter. Thus, it was found that after annealing for 6 hours at 950°C Nd₁₆Fe₇₀Co₄C9.5B0.5 already has a coercive force of 600 kA/m. Similar magnets without Co require a grinding step to attain said value (see Table). After an annealing treatment at 950°C for 15 minutes, it appeared that the alloy Nd₁₆Fe₇₂Co₂C9.5B0.5 already had a coercive force of 510 kA/m.
- Fig. 1 shows the effect of a small substitution of C by B in Nd₂Fe₁₄C on the maximum transformation temperature. Above the line shown, the intended tetragonal phase is not achieved. When approximately 2.5% of B is added, related to the overall content of C and B, it is found that the maximum transformation temperature has risen from 890°C to 1050°C.
- Fig. 2 shows the effect of grinding (duration t in min.) on the coercive force (Hc, kA/m) of an alloy obtained according to the inventive method (exemplary embodiment 2). The grinding operation almost tripled the coercive force. The Figure further shows that too long a grinding treatment adversely affects the coercive force of the powder.
- Fig. 3 shows the hysteresis loop of a magnetic alloy having the composition Nd₁₆Fe₇₅C8.55B0.45 at a magnetic field of 5 T. The alloy was heated at 950°C for 1 day. The remanence was 0.65 T.
Claims (6)
- A method of manufacturing an isotropic permanently magnetic material which comprises Nd and/or Pr, Fe and C, the constituents of the material being melted together to form an alloy which is subsequently subjected to a thermal treatment, so that phase transformation takes place, characterized in that the alloy comprises 10-20 at.% of Nd and/or Pr, 70-85 at.% of Fe, 4-11 at.% of C and 0.1-2 at.% of B, and in that the thermal treatment takes place at a temperature between 900°C and 1050°C.
- A method as claimed in Claim 1, characterized in that the alloy is subjected to the thermal treatment for maximally 4 days.
- A method as claimed in Claim 1 or 2, characterized in that the alloy is ground to form a magnetic powder having an average particle size of 2 to 40 »m.
- Isotropic permanently magnetic material, characterized in that the material comprises 10-20 at.% of Nd and/or Pr, 70-85 at.% of Fe, 4-11 at.% of C and 0.1-2 at.% of B, and in that the material has a coercive force of at least 150 kA/m.
- Isotropic permanently magnetic material as claimed in Claim 4, characterized in that the material also contains Co in a quantity of maximally 10 at%.
- A synthetic resin-bound, isotropic, permanent magnet, characterized in that the magnet comprises an isotropic, permanently magnetic material as claimed in Claim 4 or 5.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NL9001561 | 1990-07-09 | ||
NL9001561 | 1990-07-09 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0466246A1 EP0466246A1 (en) | 1992-01-15 |
EP0466246B1 true EP0466246B1 (en) | 1994-09-28 |
Family
ID=19857387
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP91201692A Expired - Lifetime EP0466246B1 (en) | 1990-07-09 | 1991-07-02 | Method of manufacturing an isotropic permanently magnetic material, isotropic permanently magnetic material and synthetic resin-bound isotropic permanent magnet |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0466246B1 (en) |
JP (1) | JPH04233201A (en) |
CN (1) | CN1059618A (en) |
DE (1) | DE69104284D1 (en) |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4849035A (en) * | 1987-08-11 | 1989-07-18 | Crucible Materials Corporation | Rare earth, iron carbon permanent magnet alloys and method for producing the same |
-
1991
- 1991-07-02 EP EP91201692A patent/EP0466246B1/en not_active Expired - Lifetime
- 1991-07-02 DE DE69104284T patent/DE69104284D1/en not_active Expired - Lifetime
- 1991-07-05 JP JP3191268A patent/JPH04233201A/en active Pending
- 1991-07-06 CN CN 91105306 patent/CN1059618A/en active Pending
Non-Patent Citations (1)
Title |
---|
308; F.Bolzoni et Al.: "MAGNETIC ANISOTROPY OF CARBON DOPED Nd2Fe14B" * |
Also Published As
Publication number | Publication date |
---|---|
CN1059618A (en) | 1992-03-18 |
DE69104284D1 (en) | 1994-11-03 |
EP0466246A1 (en) | 1992-01-15 |
JPH04233201A (en) | 1992-08-21 |
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