CA1252310A - Sm.sub.2co in17 xx alloys suitable for use as permanent magnets - Google Patents
Sm.sub.2co in17 xx alloys suitable for use as permanent magnetsInfo
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- CA1252310A CA1252310A CA000474046A CA474046A CA1252310A CA 1252310 A CA1252310 A CA 1252310A CA 000474046 A CA000474046 A CA 000474046A CA 474046 A CA474046 A CA 474046A CA 1252310 A CA1252310 A CA 1252310A
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- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 119
- 239000000956 alloy Substances 0.000 title claims abstract description 119
- 229910052772 Samarium Inorganic materials 0.000 claims abstract description 45
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 41
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 28
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 26
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000001301 oxygen Substances 0.000 claims abstract description 26
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 26
- 229910052802 copper Inorganic materials 0.000 claims abstract description 18
- 229910052742 iron Inorganic materials 0.000 claims abstract description 18
- 229910017052 cobalt Inorganic materials 0.000 claims abstract description 16
- 239000010941 cobalt Substances 0.000 claims abstract description 16
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims abstract description 11
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 claims description 36
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 30
- 239000012071 phase Substances 0.000 claims description 28
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 13
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 claims description 12
- 239000000243 solution Substances 0.000 claims description 11
- 230000032683 aging Effects 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 9
- 239000006104 solid solution Substances 0.000 claims description 9
- 229910052735 hafnium Inorganic materials 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 5
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 claims description 5
- 238000005245 sintering Methods 0.000 claims description 5
- 239000000843 powder Substances 0.000 claims description 4
- 239000000470 constituent Substances 0.000 claims description 3
- 239000007790 solid phase Substances 0.000 claims description 3
- 230000009466 transformation Effects 0.000 claims description 3
- 230000007704 transition Effects 0.000 claims description 3
- 230000002730 additional effect Effects 0.000 claims 2
- 239000007791 liquid phase Substances 0.000 claims 1
- 239000011159 matrix material Substances 0.000 claims 1
- 238000010791 quenching Methods 0.000 claims 1
- 230000000171 quenching effect Effects 0.000 claims 1
- 238000003303 reheating Methods 0.000 claims 1
- 239000007787 solid Substances 0.000 claims 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 27
- 239000010949 copper Substances 0.000 description 16
- 239000000203 mixture Substances 0.000 description 13
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 10
- 239000000047 product Substances 0.000 description 10
- 230000006698 induction Effects 0.000 description 8
- 239000013078 crystal Substances 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 229910052761 rare earth metal Inorganic materials 0.000 description 6
- 230000008901 benefit Effects 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 150000002910 rare earth metals Chemical class 0.000 description 5
- 238000007792 addition Methods 0.000 description 4
- 229910052723 transition metal Inorganic materials 0.000 description 4
- 150000003624 transition metals Chemical class 0.000 description 4
- 238000012937 correction Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 230000001427 coherent effect Effects 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- NLZUEZXRPGMBCV-UHFFFAOYSA-N Butylhydroxytoluene Chemical compound CC1=CC(C(C)(C)C)=C(O)C(C(C)(C)C)=C1 NLZUEZXRPGMBCV-UHFFFAOYSA-N 0.000 description 1
- 101100114362 Caenorhabditis elegans col-7 gene Proteins 0.000 description 1
- 229910000531 Co alloy Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 241000218652 Larix Species 0.000 description 1
- 235000005590 Larix decidua Nutrition 0.000 description 1
- 229910000612 Sm alloy Inorganic materials 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 230000004308 accommodation Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000001413 cellular effect Effects 0.000 description 1
- 229940000425 combination drug Drugs 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000005381 magnetic domain Effects 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- MMKQUGHLEMYQSG-UHFFFAOYSA-N oxygen(2-);praseodymium(3+) Chemical compound [O-2].[O-2].[O-2].[Pr+3].[Pr+3] MMKQUGHLEMYQSG-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910003447 praseodymium oxide Inorganic materials 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Landscapes
- Hard Magnetic Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An Sm2Co17 alloy contains by weight 22.5 to 23.5% Sm as an effective amount, 20.0 to 25.0% Fe, 3.0 to 5.0% Cu, 1.4 to 2.0% Zr as an effective amount, minor amounts of oxygen and carbon, an additional amount of Sm in the range of from about 4 to about 9 times the oxygen content of the alloy, an additional amount of Zr in the range of from about 5 to about 10 times the carbon con-tent of the alloy, the balance being cobalt. The alloy has a crystallographic structure comprising cells of 2-17 Sm-Co rhombohedral phase surrounded by a continuous network of the 1-5 Sm-Co nexagonal phase.
An Sm2Co17 alloy contains by weight 22.5 to 23.5% Sm as an effective amount, 20.0 to 25.0% Fe, 3.0 to 5.0% Cu, 1.4 to 2.0% Zr as an effective amount, minor amounts of oxygen and carbon, an additional amount of Sm in the range of from about 4 to about 9 times the oxygen content of the alloy, an additional amount of Zr in the range of from about 5 to about 10 times the carbon con-tent of the alloy, the balance being cobalt. The alloy has a crystallographic structure comprising cells of 2-17 Sm-Co rhombohedral phase surrounded by a continuous network of the 1-5 Sm-Co nexagonal phase.
Description
Sm2Col7 ALLOYS SU I TAB LE FOR US E
AS PERMANENT MAGNETS
This invention relates to Sm~Col7 alloys suit-able for use as permanent magnets.
~ he advantages of rare earth cobalt alloy mag-nets are now well known. Such magnets are specially suitable for use in electric motors, such as DC servo-motors. It is also known that Sm2Col7 alloys have potentlal advantages for use as permanent magnets over SmCos alloys(l). For example, DC motors using Sm2Col7 alloy magnets have lower weight and inertia and increased torque and acceleration compared to the use of SmCo5 alloy magnets.
Various attempts have been made to provide Sm2Col7 alloys which can form permanent magnets having a high energy product (sH)max and a high intrinsic coercivity iH~. Typical prior art is shown for example in United States patent No. 4,172,717 issued October 30, 1979 to Tokunaga et al(2), United States patent No.
4,213,803 issued July 22, 1980 to Yoneyama et al(3), United States patent No. ~,221,613 issued September 9, 1980 to Imaizumi et al(4) and United States patent No. 4,375,996 issued ~larch 8, 1983 to Tawara et al(5). Other prior art is shown in the published literature(~,7,8,9,10) .
As disclosed in the above-mentiGned prior art, Sm2Col7 alloys are known which can form magnets having an energy product (BH)maX in the range of 22 to 30 MGOe and an intrinsic coercivity iHC in the range of 5.8 to 6.3 kOe(6~7)~ Later developments have resulted in the pro-duction of Sm2Col7 alloys which can produce magnets with higher coercivity, but this advantage has been offset by loss in energy product. ~or example, one Sm2Col7 alloy is now known which can produce magnets having an energy product (BH)maX of 26 ~IGOe and an intrinsic coercivity iHC of 15.0 kOe(7). Another Sm2Col7 alloy now known has an energy product (BH)maX of 27 MGOe and an intrinsic coercivity iHC of 10.0 kOe, see United States patent No.
4,375,996 mentioned above(5).
It is also known that, because of different magnetic hardening mechanisms, Sm2Col7 alloys are harder to magnetize from an unmagnetized state than SmCos alloys. For example, in the construction of electric motors, it is the preferred practice to construct the field or stator assembly with unmagnetized magnets, and then magnetize the finished assembly as a single unit.
This preferred industrial practice imposes an upper limit of about 25 kOe on the intensity of the magnetizing field which can be applied to the unmagnetized magnets of a typical assembly. Thus, in order to be useful in practice, an unmagnetized magnet must be capable of attaining its specified properties in a magnetizing field of 25 kOe. To date, it has not been possible to achieve - this requirement with Sm2Col7 alloys with an energy product greater than 30 MGOe(6).
Thus, although it is acknowledged that Sm2Col7 alloys have po-tential advantages over other rare earth/transition metal alloys such as SmCo5 alloys, Sm2Col7 alloys have not yet become practically useful because improved coercivity has only been obtainable at ~L2~3:~
the expense of energy product and also because such alloys have not been capable of attaining their speci-fied properties in a magnetizing field up to about 25 kOe.
It is therefore an object of the invention to provide an Sm2Col7 alloy which overcomes these disad-vantages.
According to the present invention, an Sm2Col7 alloy contains by weight:
22.5 to 23.5% Sm as an effective amount, 20.0 to 25.0~ Fe, 3.0 to 5.0% C~, 1.4 to 2.0~ Zr as an effective amount.
Further, in order to compensate for minor amounts of oxygen and carbon which are inevitably present in practice, it has been found that an additional amount of Sm should be provided to compensate for the oxygen content and that an additional amount of Zr should be provided to compensate for the carbon content. Thus, an alloy in accordance with the invention also includes an additional amount of Sm in the range of from about 4 to about 9 times the oxygen content of the alloy, preferably 6.2~5 times the oxygen content, and an additional amount of Zr in the range of from about 5 to about 10 times the carbon content of the alloy, preferably 7.595 times the carbon content. The remainder of the alloy content is cobalt.
The function of the "effective samarium" is to develop the desired crystallographic structure consisting of cells of the 2-17 Sm-Co rhornbohedral phase surrounded by a continuous network of the 1-5 Sm-Co hexagonal phase(11~12~13). It is necessary that the 1-5 network be continuous to develop the desired second quadrant loop squareness, that is to say a maximum value of HK, and this is dependent upon the "effective samarium" present.
Sufficient samarium must be present for this purpose but 3 3L~
too much samarium results in the breakdown of the 2-17 rhombohedral phase and loss of remanent induction Br.
The function of the "effectiYe samarium" present is therefore to develop the 2-17 Sm-Co rhombohedral phase having high remanent induction Br and to develop a com-plete 1 5 Sm-Co hexagonal phase network to develop the coercivity or magnetic hardening. Too little samarium results in an incomplete 1-5 Sm~Co network and incomplete hardening, that is to say a low HK, and too much samarium resul~s in breakdown of the 2-17 Sm-Co phase and loss of remanent induction Br and energy product (sH)max Precise control of the "effective samarium"
content is necessary to obtain optimum properties and this can be achieved by the present invention.
The function of the "effective zirconium" is to facilitate the dissolution oE all the desired constitu-ents into one single phase solid solution in the solution heat treatment stage of the processing. Only when this is achieved is it possible to establish complete homo-genei-ty as the necessary starting point to develop in the subsequent aging heat treatment the desired structure consisting of 2-17 Sm-Co cells surrounded by a continuous network of the 1-5 Sm-Co boundary phase. The presence of zirconium distorts the Sm-Co lattice so as to reduce the c/a ratio of the hexagonal unit cell(14) and this facil-itates the accommodation of the desired elements in single phase solid solution during the solution heat treatment at 1140-1170C. At elevated temperatures the 2-17 Sm-Co composition has a hexagonal crystal lattice but at room temperature it transforms to a rhombohedral crystal lattice. These two crystal systems are closely related and the rhombohedral lattice can be reg~rded as an imperfect hexagonal lattice containing stacking faults.
The desired equilibrium structure at room temperature consists of cells of the 2-17 Sm-Co rhombohedral phase :~25~
surrounded by a continuous network of the 1-5 Sm-Co hexagonal phase. It has also been observed that for a fixed copper content the coercivity increases with the zirconium content. Thus to achieve the objective of easier magnetization it is necessary to keep the zirconium content to a minimum commensurate with the above stated requirements regarding the single phase solid solution. The necessary precise control of the "effective zirconium" content can be achieved by the 0 present invention.
sy using an Sm2Col7 alloy in accordance with the invention, it is possible to produce a permanent magnet which attains its specified properties in a magnetizing field of about 25 kOe, has an energy product (BH)maX f at least 30 MGOe and has a satisfactory coercivity iHC of 14-16 kOe. A magnet in accordance with the present invention can also have a satisEactory remanent induction Br oE at least about 11.5 kG, and a better loop squareness in the second quadrant, i.e. HK
of approximately 9.0 kOe.
Preferably, the oxygen content of the alloy is not greater than about 0.6% by weight, and the carbon content of the alloy is not greater than about 0.1% by weight.
Also, the alloy preferably contains:
23.0~ Sm as an effective amount, 22.0~ Fe, 4.6~ Cu, 1.5% Zr as an effective amount, minor amounts of oxygen and carbon, additional amounts of Sm and Zr as specified above.
and the balance being cobalt.
The invention is at least partly based upon the realization that it is possible to compensate for small traces of carbon present in many of the elements that are used in the production of the alloy and which have an adverse effect on the magnetic properties of the alloy.
In accordance with the invention, compensation is made for the carbon content by providing an additional amount of zirconium as specified above.
The additional zirconium may be incorporated in the alloy by adding zirconium in the form of a master alloy to an Sm2Col7 base alloy at a convenient stage in the processing, for example prior to compactinq and sintering the alloy powder. The master alloy may be of a simple form such as ferrozirconium, which is a low melting point (about 935C) eutectic containing 83% Zr and 17% Fe by weight. Ferrozirconium may be successfully used when only a small additional amount of zirconium is required. In other words, only up to about 2%
ferrozirconium by weight should be added.
If a larger additional amount of zirconium has to be added, it is preferable to utilize a master alloy with the same composition as the base alloy with the exception that the master alloy should contain a larger amount of zirconium, for example from about 5 to 10% by weight, the increase in the zirconium content being achieved at the expense of the cobalt content.
The following table illustrates the compensa-tion of zirconium content for carbon present and the optimum zirconium level at about 1.5%.
.. .
Total Zr C Cx6.265 ~ffective Zr Br iHc HK
(%) (%) (%) (~) (kG) (kOe) (kOe) . _ _
AS PERMANENT MAGNETS
This invention relates to Sm~Col7 alloys suit-able for use as permanent magnets.
~ he advantages of rare earth cobalt alloy mag-nets are now well known. Such magnets are specially suitable for use in electric motors, such as DC servo-motors. It is also known that Sm2Col7 alloys have potentlal advantages for use as permanent magnets over SmCos alloys(l). For example, DC motors using Sm2Col7 alloy magnets have lower weight and inertia and increased torque and acceleration compared to the use of SmCo5 alloy magnets.
Various attempts have been made to provide Sm2Col7 alloys which can form permanent magnets having a high energy product (sH)max and a high intrinsic coercivity iH~. Typical prior art is shown for example in United States patent No. 4,172,717 issued October 30, 1979 to Tokunaga et al(2), United States patent No.
4,213,803 issued July 22, 1980 to Yoneyama et al(3), United States patent No. ~,221,613 issued September 9, 1980 to Imaizumi et al(4) and United States patent No. 4,375,996 issued ~larch 8, 1983 to Tawara et al(5). Other prior art is shown in the published literature(~,7,8,9,10) .
As disclosed in the above-mentiGned prior art, Sm2Col7 alloys are known which can form magnets having an energy product (BH)maX in the range of 22 to 30 MGOe and an intrinsic coercivity iHC in the range of 5.8 to 6.3 kOe(6~7)~ Later developments have resulted in the pro-duction of Sm2Col7 alloys which can produce magnets with higher coercivity, but this advantage has been offset by loss in energy product. ~or example, one Sm2Col7 alloy is now known which can produce magnets having an energy product (BH)maX of 26 ~IGOe and an intrinsic coercivity iHC of 15.0 kOe(7). Another Sm2Col7 alloy now known has an energy product (BH)maX of 27 MGOe and an intrinsic coercivity iHC of 10.0 kOe, see United States patent No.
4,375,996 mentioned above(5).
It is also known that, because of different magnetic hardening mechanisms, Sm2Col7 alloys are harder to magnetize from an unmagnetized state than SmCos alloys. For example, in the construction of electric motors, it is the preferred practice to construct the field or stator assembly with unmagnetized magnets, and then magnetize the finished assembly as a single unit.
This preferred industrial practice imposes an upper limit of about 25 kOe on the intensity of the magnetizing field which can be applied to the unmagnetized magnets of a typical assembly. Thus, in order to be useful in practice, an unmagnetized magnet must be capable of attaining its specified properties in a magnetizing field of 25 kOe. To date, it has not been possible to achieve - this requirement with Sm2Col7 alloys with an energy product greater than 30 MGOe(6).
Thus, although it is acknowledged that Sm2Col7 alloys have po-tential advantages over other rare earth/transition metal alloys such as SmCo5 alloys, Sm2Col7 alloys have not yet become practically useful because improved coercivity has only been obtainable at ~L2~3:~
the expense of energy product and also because such alloys have not been capable of attaining their speci-fied properties in a magnetizing field up to about 25 kOe.
It is therefore an object of the invention to provide an Sm2Col7 alloy which overcomes these disad-vantages.
According to the present invention, an Sm2Col7 alloy contains by weight:
22.5 to 23.5% Sm as an effective amount, 20.0 to 25.0~ Fe, 3.0 to 5.0% C~, 1.4 to 2.0~ Zr as an effective amount.
Further, in order to compensate for minor amounts of oxygen and carbon which are inevitably present in practice, it has been found that an additional amount of Sm should be provided to compensate for the oxygen content and that an additional amount of Zr should be provided to compensate for the carbon content. Thus, an alloy in accordance with the invention also includes an additional amount of Sm in the range of from about 4 to about 9 times the oxygen content of the alloy, preferably 6.2~5 times the oxygen content, and an additional amount of Zr in the range of from about 5 to about 10 times the carbon content of the alloy, preferably 7.595 times the carbon content. The remainder of the alloy content is cobalt.
The function of the "effective samarium" is to develop the desired crystallographic structure consisting of cells of the 2-17 Sm-Co rhornbohedral phase surrounded by a continuous network of the 1-5 Sm-Co hexagonal phase(11~12~13). It is necessary that the 1-5 network be continuous to develop the desired second quadrant loop squareness, that is to say a maximum value of HK, and this is dependent upon the "effective samarium" present.
Sufficient samarium must be present for this purpose but 3 3L~
too much samarium results in the breakdown of the 2-17 rhombohedral phase and loss of remanent induction Br.
The function of the "effectiYe samarium" present is therefore to develop the 2-17 Sm-Co rhombohedral phase having high remanent induction Br and to develop a com-plete 1 5 Sm-Co hexagonal phase network to develop the coercivity or magnetic hardening. Too little samarium results in an incomplete 1-5 Sm~Co network and incomplete hardening, that is to say a low HK, and too much samarium resul~s in breakdown of the 2-17 Sm-Co phase and loss of remanent induction Br and energy product (sH)max Precise control of the "effective samarium"
content is necessary to obtain optimum properties and this can be achieved by the present invention.
The function of the "effective zirconium" is to facilitate the dissolution oE all the desired constitu-ents into one single phase solid solution in the solution heat treatment stage of the processing. Only when this is achieved is it possible to establish complete homo-genei-ty as the necessary starting point to develop in the subsequent aging heat treatment the desired structure consisting of 2-17 Sm-Co cells surrounded by a continuous network of the 1-5 Sm-Co boundary phase. The presence of zirconium distorts the Sm-Co lattice so as to reduce the c/a ratio of the hexagonal unit cell(14) and this facil-itates the accommodation of the desired elements in single phase solid solution during the solution heat treatment at 1140-1170C. At elevated temperatures the 2-17 Sm-Co composition has a hexagonal crystal lattice but at room temperature it transforms to a rhombohedral crystal lattice. These two crystal systems are closely related and the rhombohedral lattice can be reg~rded as an imperfect hexagonal lattice containing stacking faults.
The desired equilibrium structure at room temperature consists of cells of the 2-17 Sm-Co rhombohedral phase :~25~
surrounded by a continuous network of the 1-5 Sm-Co hexagonal phase. It has also been observed that for a fixed copper content the coercivity increases with the zirconium content. Thus to achieve the objective of easier magnetization it is necessary to keep the zirconium content to a minimum commensurate with the above stated requirements regarding the single phase solid solution. The necessary precise control of the "effective zirconium" content can be achieved by the 0 present invention.
sy using an Sm2Col7 alloy in accordance with the invention, it is possible to produce a permanent magnet which attains its specified properties in a magnetizing field of about 25 kOe, has an energy product (BH)maX f at least 30 MGOe and has a satisfactory coercivity iHC of 14-16 kOe. A magnet in accordance with the present invention can also have a satisEactory remanent induction Br oE at least about 11.5 kG, and a better loop squareness in the second quadrant, i.e. HK
of approximately 9.0 kOe.
Preferably, the oxygen content of the alloy is not greater than about 0.6% by weight, and the carbon content of the alloy is not greater than about 0.1% by weight.
Also, the alloy preferably contains:
23.0~ Sm as an effective amount, 22.0~ Fe, 4.6~ Cu, 1.5% Zr as an effective amount, minor amounts of oxygen and carbon, additional amounts of Sm and Zr as specified above.
and the balance being cobalt.
The invention is at least partly based upon the realization that it is possible to compensate for small traces of carbon present in many of the elements that are used in the production of the alloy and which have an adverse effect on the magnetic properties of the alloy.
In accordance with the invention, compensation is made for the carbon content by providing an additional amount of zirconium as specified above.
The additional zirconium may be incorporated in the alloy by adding zirconium in the form of a master alloy to an Sm2Col7 base alloy at a convenient stage in the processing, for example prior to compactinq and sintering the alloy powder. The master alloy may be of a simple form such as ferrozirconium, which is a low melting point (about 935C) eutectic containing 83% Zr and 17% Fe by weight. Ferrozirconium may be successfully used when only a small additional amount of zirconium is required. In other words, only up to about 2%
ferrozirconium by weight should be added.
If a larger additional amount of zirconium has to be added, it is preferable to utilize a master alloy with the same composition as the base alloy with the exception that the master alloy should contain a larger amount of zirconium, for example from about 5 to 10% by weight, the increase in the zirconium content being achieved at the expense of the cobalt content.
The following table illustrates the compensa-tion of zirconium content for carbon present and the optimum zirconium level at about 1.5%.
.. .
Total Zr C Cx6.265 ~ffective Zr Br iHc HK
(%) (%) (%) (~) (kG) (kOe) (kOe) . _ _
2.24 0.07 0.53 1.71 11.6 19.1 8.3 2.1 0.072 0.55 1.55 11.7 16~9 9.8 2.05 0.068 0.52 1.53 11.6 15.2 ~.9 2.0 0.195 1.48 0.52 1.6 0.2 0.
:~S~3;~
The present invention is also at least partly based on the realization that it is possible to compensate for the small traces of oxygen which are pic~ed up by the alloy during its manufacture and which have an adverse effect on the magnetic properties of the alloy. In accordance with the invention, the small traces of oxygen are compensated for by addition of an additional amount of samarium as specified above. The amount of oxygen in the final product can be estimated from the oxygen content of the starting material or more preferably determined by analyzing a sample product.
The samarium addition may be accomplished by adding a samarium rich alloy to a Sm2Col7 base alloy at a convenient stage in the processing, for example prior to compacting and sintering the alloy powder. It is not practicable to add elemental samarium because of its high rate of oxidation. The samarium rich alloy preferably has the same composition as the base alloy except that the samarium content would be about 1 to 3~ higher than in the base alloy, the higher samarium content being achieved at the expense of the cobalt content. A simple binary master alloy (such as 60% Sm, 40% Co) can also be used to add Sm.
The following table illustrates the compensa-tion of samarium content for oxygen present and theoptimum effective samarium in the range 22.5-23.5%.
Total Sm 2 02x6.2~5 Effective Sm 3r iHc HK
(%) (~) (%) (~) (kG) (kOe) (kOe) 24.6 0.44 2.7621.8 9.62 4.0 1~85 25.1 0.42 2.6322.5 11.64 19.45 6.25 25.3 0.42 2.6322.7 11.73 17.9 g.l 26.0 0.55 3.4522.6 11.65 16.9 9.8 26.1 0.56 3.5122.6 11.54 17.7 8.9 26.0 0.38 2.3823.6 11.3 15.9 6.3 ~ y adding additional zirconium and samarium to compensate for the inevitable presence of small traces of carbon and oxygen in the alloy, it has been found to be possible to define more precisely the alloy composition in order to produce the preferred magnetic properties.
Thus, the preferred samarium range is 22.5 to 23.5% with the preferred samarium value being 23.0% Sm.
This is the effective amount, as compared to the additional amount provided as specified to compensate for oxygen content. The range of effective samarium content is considerably narrower than has been specified in the prior art.
The effective zirconium range has been specified to be from 1.4 to 2.0% with the preferred value being 1O5~. Thus, with the present invention, it has been possible to specify a zirconium range which is considerably narrower than that taught by the prior art.
It has also been found possible to optimize the iron and copper contents. The composition limits of iron, copper and zirconium are interrelated and each can critically affect the existence of the single phase structure. It is known that the addition of iron to the 2-17 Sm-Co system increases the remanent induction ~z~
provided that the structure can be maintained as a single 2-17 Sm-Co phase. If the optimum iron content is exceeded the alloy breaks down into an Fe-rich eutectoid structure having lower remanent induction. It has been observed that the copper content acts to increase the coercivity or magnetic hardness of the alloy. It is believed that copper concentrates in the 1-5 Sm-Co phase network and enhances the coherent nucleation of regions of 2-17 Sm-Co phase within the 1-5 Sm-Co phase network during cooling from the aging temperature, thereby creating lattice strain and magnetic hardness or coercivity(15).
The iron content has been specified to be 20.0 to 25.0%, preferably 22.0~, and the copper content has 15 been specified to be 3~0 to 5 0%, preferably 4.6~. The iron content has also been defined within a much narrower range than has been taught by the prior art. Similar remarks apply to the copper content~ As previously indicated, cobalt forms the balance of the composition.
~n Sm2Col7 alloy in accordance with the inven-tion is preferably made in the following manner. The alloy oE the desired composition was produced by pul-veri~ing melted and cast alloy into particles of 3-8 m size. Small additions of ferrozirconium and a samarium rich alloy of similar composition to the parent alloy were then blended in to compensate for the deleterious effects of the trace amounts o~ carbon and oxygen present according to the present invention. The blended powders were aligned in a die under a transverse magnetic field of 12 kOe and compacted under a pressure of ~0 kpsi. The green compact was sintered in hydrogen at 1150C for 30 min. The atmosphere was then changed to argon and the compact was heated to 1205C at a rate of 4-5C/min, held at 1205QC for 10 min and then cooled to 1160C at 2C/min. The sample was then solution treated at ~2~
1140-llhOC for 2 hours, quenched from 1140 300C at 10C/s and air cooled from 800C to room temperature. It was then reheated to 845~5C and held for 20 hours, cooled at about 2C/min from 845C to about 600~C and at about lDC/min from about 600C to 410C, held at 410C
for 10 hours and cooled to room temperature.
An Sm2Col7 alloy having the previously men-tioned preferred composition in accordance with the invention and produced in the above described manner achieved the following properties:
(BH)max Br iHc Hc HK
MGOe kG kOe kOe kOe_ _ 30.8 11.7 15.8 11.0 9.0 The advantage of the invention can readily be seen from the above Table.
It has also been found that praseodymium can be substituted in part for samarium in the alloy of the present invention without decreasing the aforementioned desirable properties. To preserve the required 2-17 Sm-Co rhombohedral crystal structure the substitution of praseodymium must be made on an atomic basis, that is to say since praseodymium has a lower atomic weight than samarium, on a weight percent basis less praseodymium will be required in the alloy than the weight percent of samarium replaced. In the example illustrated below it was found that whereas optimum properties were obtained with 23.0% effective samarium in the standard alloy, when a combination of samarium and praseodymium was used the optimum properties were obtained with an effective amount 30 of 22.5% (Sm + Pr), comprising 2000% Sm -~ 2.5% Pr.
Furthermore, in calculating the effective amount of praseodymium present with respect to that amount which has been rendered ineffective by combination with oxygen, account must be taken of the molecular weight of the praseodymium oxide and the correction factor of 6.265
:~S~3;~
The present invention is also at least partly based on the realization that it is possible to compensate for the small traces of oxygen which are pic~ed up by the alloy during its manufacture and which have an adverse effect on the magnetic properties of the alloy. In accordance with the invention, the small traces of oxygen are compensated for by addition of an additional amount of samarium as specified above. The amount of oxygen in the final product can be estimated from the oxygen content of the starting material or more preferably determined by analyzing a sample product.
The samarium addition may be accomplished by adding a samarium rich alloy to a Sm2Col7 base alloy at a convenient stage in the processing, for example prior to compacting and sintering the alloy powder. It is not practicable to add elemental samarium because of its high rate of oxidation. The samarium rich alloy preferably has the same composition as the base alloy except that the samarium content would be about 1 to 3~ higher than in the base alloy, the higher samarium content being achieved at the expense of the cobalt content. A simple binary master alloy (such as 60% Sm, 40% Co) can also be used to add Sm.
The following table illustrates the compensa-tion of samarium content for oxygen present and theoptimum effective samarium in the range 22.5-23.5%.
Total Sm 2 02x6.2~5 Effective Sm 3r iHc HK
(%) (~) (%) (~) (kG) (kOe) (kOe) 24.6 0.44 2.7621.8 9.62 4.0 1~85 25.1 0.42 2.6322.5 11.64 19.45 6.25 25.3 0.42 2.6322.7 11.73 17.9 g.l 26.0 0.55 3.4522.6 11.65 16.9 9.8 26.1 0.56 3.5122.6 11.54 17.7 8.9 26.0 0.38 2.3823.6 11.3 15.9 6.3 ~ y adding additional zirconium and samarium to compensate for the inevitable presence of small traces of carbon and oxygen in the alloy, it has been found to be possible to define more precisely the alloy composition in order to produce the preferred magnetic properties.
Thus, the preferred samarium range is 22.5 to 23.5% with the preferred samarium value being 23.0% Sm.
This is the effective amount, as compared to the additional amount provided as specified to compensate for oxygen content. The range of effective samarium content is considerably narrower than has been specified in the prior art.
The effective zirconium range has been specified to be from 1.4 to 2.0% with the preferred value being 1O5~. Thus, with the present invention, it has been possible to specify a zirconium range which is considerably narrower than that taught by the prior art.
It has also been found possible to optimize the iron and copper contents. The composition limits of iron, copper and zirconium are interrelated and each can critically affect the existence of the single phase structure. It is known that the addition of iron to the 2-17 Sm-Co system increases the remanent induction ~z~
provided that the structure can be maintained as a single 2-17 Sm-Co phase. If the optimum iron content is exceeded the alloy breaks down into an Fe-rich eutectoid structure having lower remanent induction. It has been observed that the copper content acts to increase the coercivity or magnetic hardness of the alloy. It is believed that copper concentrates in the 1-5 Sm-Co phase network and enhances the coherent nucleation of regions of 2-17 Sm-Co phase within the 1-5 Sm-Co phase network during cooling from the aging temperature, thereby creating lattice strain and magnetic hardness or coercivity(15).
The iron content has been specified to be 20.0 to 25.0%, preferably 22.0~, and the copper content has 15 been specified to be 3~0 to 5 0%, preferably 4.6~. The iron content has also been defined within a much narrower range than has been taught by the prior art. Similar remarks apply to the copper content~ As previously indicated, cobalt forms the balance of the composition.
~n Sm2Col7 alloy in accordance with the inven-tion is preferably made in the following manner. The alloy oE the desired composition was produced by pul-veri~ing melted and cast alloy into particles of 3-8 m size. Small additions of ferrozirconium and a samarium rich alloy of similar composition to the parent alloy were then blended in to compensate for the deleterious effects of the trace amounts o~ carbon and oxygen present according to the present invention. The blended powders were aligned in a die under a transverse magnetic field of 12 kOe and compacted under a pressure of ~0 kpsi. The green compact was sintered in hydrogen at 1150C for 30 min. The atmosphere was then changed to argon and the compact was heated to 1205C at a rate of 4-5C/min, held at 1205QC for 10 min and then cooled to 1160C at 2C/min. The sample was then solution treated at ~2~
1140-llhOC for 2 hours, quenched from 1140 300C at 10C/s and air cooled from 800C to room temperature. It was then reheated to 845~5C and held for 20 hours, cooled at about 2C/min from 845C to about 600~C and at about lDC/min from about 600C to 410C, held at 410C
for 10 hours and cooled to room temperature.
An Sm2Col7 alloy having the previously men-tioned preferred composition in accordance with the invention and produced in the above described manner achieved the following properties:
(BH)max Br iHc Hc HK
MGOe kG kOe kOe kOe_ _ 30.8 11.7 15.8 11.0 9.0 The advantage of the invention can readily be seen from the above Table.
It has also been found that praseodymium can be substituted in part for samarium in the alloy of the present invention without decreasing the aforementioned desirable properties. To preserve the required 2-17 Sm-Co rhombohedral crystal structure the substitution of praseodymium must be made on an atomic basis, that is to say since praseodymium has a lower atomic weight than samarium, on a weight percent basis less praseodymium will be required in the alloy than the weight percent of samarium replaced. In the example illustrated below it was found that whereas optimum properties were obtained with 23.0% effective samarium in the standard alloy, when a combination of samarium and praseodymium was used the optimum properties were obtained with an effective amount 30 of 22.5% (Sm + Pr), comprising 2000% Sm -~ 2.5% Pr.
Furthermore, in calculating the effective amount of praseodymium present with respect to that amount which has been rendered ineffective by combination with oxygen, account must be taken of the molecular weight of the praseodymium oxide and the correction factor of 6.265
3~S~3~
times the oxygen content for samarium must be changed to 5.871 for the praseodymium added. In a co-pending appli-cation the process for the production of high strength 2-17 Sm-Co permanent magne~s of the present composition is described. Of particular importance is the selection of the solution treatment temperature which is marginally below the liquid plus solid phase transformation tempera-ture for the specific alloy composition. In the case where praseodymium has been partially substituted for samarium care must be taken since the liquid plus solid phase transformation temperature will be lower than that of the standard samarium alloy by an amount depending on the level of praseodymium substituted. The following example illustrates the partial replacement of samarium 15 by praseodymium, An alloy containing 20.3% Sm and 2017%
Pr as effective amounts was prepared as described earlier with the exception that the solution treatment step was carried out in the range 1130-1150C. The following properties were obtained and are compared with those of a similar alloy containing only samarium as the rare earth element.
Eff. Sm Eff. Pr Fe Cu ~r Co Br iHc ~
(%) (%) (~) (%) (%) (%) (kG) (kOe) (kOe) _ _ 20.32.17 20.5 5.2 2.5 bal 11.6 22.65 8.7 23.8_ 20.5 5.2 2.5 bal 11.5 22.4 9.7 It has also been found that other group Ivs or VB transition elements may be substituted full or in part for zirconium in the alloy of the present invention. Since the function oE the group IVB or VB transition element is to reduce the c/a ratio of the 2-17 Sm-Co hexagonal unit cell, the replacement of zirconium by other elements must 5~
be made on an atomic basis. Furthermore in calculating the effective amount of the transition metal present with respect to that amount rendered ineffective by combina-tion with carbon, account must be taken of the molecular weight of the transition metal carbide and the correc-tion factor of 7.595 times the carbon content of the alloy must be adjusted accordingly. For example~ in the case of hafnium the correction factor would be 14.862 times the carbon content of the alloy. In a co-pending application the process for the production of high strength 2-17 Sm-Co permanent magnets is described and it is noted therein that the aging temperature is critically dependent upon the zirconium content. In the case where other group IVB or VB transition elements are substituted for zirconium in the alloy of the present invention the optimum aging temperature and time may be different. The following example illustrates the substitution of hafnium for zirconium in an alloy of the present invention. An alloy was prepared as described earlier for the standard alloy except that zirconium as an effective amount was replaced by hafnium as an effective amount. In calculat-ing the additional amount of hafnium required to arrive at the effective amount the carbon content of the alloy was multiplied by the factor 14.862. The alloy was pro-cessed as described earlier for the standard alloy with the exception that after ~uenching from the solution temperature to room temperature the alloy was reheated to an aging temperature of 845~5C and held there for 24 hours.
The following table illustrates the replacement of zirconium by hafni~m as an effective amount.
Total Zr ¦ Cx7.595 Effective Zr Br(l) ~%) (~) (%) (%) (kG) 5 1.78 0.07 0.53 1.25 10.6 1.90 0.07 0.53 1.37 10.9 10Total Hf C Cx14.862Effective Hf Br(l) (%) (%) (%) (%) (kG) 3.65 0.082 1.22 2.43 10.6 3.80 0.082 1.22 2.58 10.7 _ (1) The results in the above table are for parallel aligned magnets. The residual induction (Br) for the same magnets transversely aligned would be approximately 1.0 kG higher, i.e. 11.6-11.9 kG.
The invention thus also provides an Sm2Col7 alloy permanent magnet containing also iron, copper and zirconium or similar group IVB or VB transition metals, said alloy containing: an effective amount of samarium, in addition to that samarium combined with oxygen, such that after the aging stage of the process the crystal structure of the alloy consists of the single phase 2-17 Sm-Co rhombohedral structure containing a continuous network of the 1-5 Sm-Co phase, an effective amount of zirconium, in addition to that zirconium combined with carbon, such that during the solution heat treatment stage of the process the 2-17 Sm-Co crystal lattice is distorted to facilitate the dissolution of all the con-stituents of said alloy into a uniform single phase soli solution, an amount of iron being as high as possible to maximize the remanent induction of said alloy whilst :~2~
- 12a -still maintalning the single phase ~-17 Sm-Co uniform solid solution in the solution heat treatment stage of the process, an amount of copper such that during the cooling stage from the aging temperature the coherent nucleation of 2-17 Sm-Co phase within the 1-5 Sm-Co phase network is enhanced to produce lattice strain and coercivity, it being understood that both zirconium and copper levels must be controlled to permit the iron level to be optimized whilst still maintaining a uniform solid solution in the solution heat treatment stage.
(continued on page 133 The optimi~ation of composition must be based on the requirement that all the alloying elements are first put into a uniform solid solution. In the studies of composition variations in Fe, Cu and Zr it was found that the optimum effective samarium content remained constant at 23+0.5%. However, it was found that the effective samarium content can be partly replaced by praseodymium with the added observation that slightly less (Sm+Pr) is required for optimum properties. From an economic point of view this could be an attractive alternative.
_ Other embodiments and examples of the invention will be clearly apparent to a person skilled in the art, the scope of the invention being defined in the appended claims.
The process is more fully described in our co-pending application Serial No. 474,045 filed on the same date as -this application.
References 1. Wallace, W.E., "Rare Earth Intermetallics", Academic Press, New York, 1973.
2. Tokunaga, M., Hagi, C. and Murayama, H.~ "Permanent Magnet Alloy", U.S. Patent No. 4,172,717, October 30, 1979.
3. Yoneyama, T., Tomizawa, S., Hori, T. and Ojima, T., "R2Col7 Rare Type Earth Cobalt Permanent Magnet Material and Process for Producing the Same", U.S. Patent No.
times the oxygen content for samarium must be changed to 5.871 for the praseodymium added. In a co-pending appli-cation the process for the production of high strength 2-17 Sm-Co permanent magne~s of the present composition is described. Of particular importance is the selection of the solution treatment temperature which is marginally below the liquid plus solid phase transformation tempera-ture for the specific alloy composition. In the case where praseodymium has been partially substituted for samarium care must be taken since the liquid plus solid phase transformation temperature will be lower than that of the standard samarium alloy by an amount depending on the level of praseodymium substituted. The following example illustrates the partial replacement of samarium 15 by praseodymium, An alloy containing 20.3% Sm and 2017%
Pr as effective amounts was prepared as described earlier with the exception that the solution treatment step was carried out in the range 1130-1150C. The following properties were obtained and are compared with those of a similar alloy containing only samarium as the rare earth element.
Eff. Sm Eff. Pr Fe Cu ~r Co Br iHc ~
(%) (%) (~) (%) (%) (%) (kG) (kOe) (kOe) _ _ 20.32.17 20.5 5.2 2.5 bal 11.6 22.65 8.7 23.8_ 20.5 5.2 2.5 bal 11.5 22.4 9.7 It has also been found that other group Ivs or VB transition elements may be substituted full or in part for zirconium in the alloy of the present invention. Since the function oE the group IVB or VB transition element is to reduce the c/a ratio of the 2-17 Sm-Co hexagonal unit cell, the replacement of zirconium by other elements must 5~
be made on an atomic basis. Furthermore in calculating the effective amount of the transition metal present with respect to that amount rendered ineffective by combina-tion with carbon, account must be taken of the molecular weight of the transition metal carbide and the correc-tion factor of 7.595 times the carbon content of the alloy must be adjusted accordingly. For example~ in the case of hafnium the correction factor would be 14.862 times the carbon content of the alloy. In a co-pending application the process for the production of high strength 2-17 Sm-Co permanent magnets is described and it is noted therein that the aging temperature is critically dependent upon the zirconium content. In the case where other group IVB or VB transition elements are substituted for zirconium in the alloy of the present invention the optimum aging temperature and time may be different. The following example illustrates the substitution of hafnium for zirconium in an alloy of the present invention. An alloy was prepared as described earlier for the standard alloy except that zirconium as an effective amount was replaced by hafnium as an effective amount. In calculat-ing the additional amount of hafnium required to arrive at the effective amount the carbon content of the alloy was multiplied by the factor 14.862. The alloy was pro-cessed as described earlier for the standard alloy with the exception that after ~uenching from the solution temperature to room temperature the alloy was reheated to an aging temperature of 845~5C and held there for 24 hours.
The following table illustrates the replacement of zirconium by hafni~m as an effective amount.
Total Zr ¦ Cx7.595 Effective Zr Br(l) ~%) (~) (%) (%) (kG) 5 1.78 0.07 0.53 1.25 10.6 1.90 0.07 0.53 1.37 10.9 10Total Hf C Cx14.862Effective Hf Br(l) (%) (%) (%) (%) (kG) 3.65 0.082 1.22 2.43 10.6 3.80 0.082 1.22 2.58 10.7 _ (1) The results in the above table are for parallel aligned magnets. The residual induction (Br) for the same magnets transversely aligned would be approximately 1.0 kG higher, i.e. 11.6-11.9 kG.
The invention thus also provides an Sm2Col7 alloy permanent magnet containing also iron, copper and zirconium or similar group IVB or VB transition metals, said alloy containing: an effective amount of samarium, in addition to that samarium combined with oxygen, such that after the aging stage of the process the crystal structure of the alloy consists of the single phase 2-17 Sm-Co rhombohedral structure containing a continuous network of the 1-5 Sm-Co phase, an effective amount of zirconium, in addition to that zirconium combined with carbon, such that during the solution heat treatment stage of the process the 2-17 Sm-Co crystal lattice is distorted to facilitate the dissolution of all the con-stituents of said alloy into a uniform single phase soli solution, an amount of iron being as high as possible to maximize the remanent induction of said alloy whilst :~2~
- 12a -still maintalning the single phase ~-17 Sm-Co uniform solid solution in the solution heat treatment stage of the process, an amount of copper such that during the cooling stage from the aging temperature the coherent nucleation of 2-17 Sm-Co phase within the 1-5 Sm-Co phase network is enhanced to produce lattice strain and coercivity, it being understood that both zirconium and copper levels must be controlled to permit the iron level to be optimized whilst still maintaining a uniform solid solution in the solution heat treatment stage.
(continued on page 133 The optimi~ation of composition must be based on the requirement that all the alloying elements are first put into a uniform solid solution. In the studies of composition variations in Fe, Cu and Zr it was found that the optimum effective samarium content remained constant at 23+0.5%. However, it was found that the effective samarium content can be partly replaced by praseodymium with the added observation that slightly less (Sm+Pr) is required for optimum properties. From an economic point of view this could be an attractive alternative.
_ Other embodiments and examples of the invention will be clearly apparent to a person skilled in the art, the scope of the invention being defined in the appended claims.
The process is more fully described in our co-pending application Serial No. 474,045 filed on the same date as -this application.
References 1. Wallace, W.E., "Rare Earth Intermetallics", Academic Press, New York, 1973.
2. Tokunaga, M., Hagi, C. and Murayama, H.~ "Permanent Magnet Alloy", U.S. Patent No. 4,172,717, October 30, 1979.
3. Yoneyama, T., Tomizawa, S., Hori, T. and Ojima, T., "R2Col7 Rare Type Earth Cobalt Permanent Magnet Material and Process for Producing the Same", U.S. Patent No.
4,213,803, July 22, 19~0.
Imaizumi, N. and Wakana, K., "Rare Earth-Cobalt System Permanent Magnetic Alloys and Method of Preparing Same", ~ U.S. Patent No. 4,221,613, September 9, 1980.
Imaizumi, N. and Wakana, K., "Rare Earth-Cobalt System Permanent Magnetic Alloys and Method of Preparing Same", ~ U.S. Patent No. 4,221,613, September 9, 1980.
5. Tawara, Y., Chino, T. and Ohasi, K., "Rare Earth Metal Containing Alloys for Permanent Magnets", U.S. Patent No~ 4,375,996, March 8, 1983.
6. Semones, B.C., "High Energy Density Rare Earth-Cobalt Magnets and D.C. Servo Motors: A Valuable Union", Sixth International Workshop on Rare Earth-Cobalt Permanent Magnets, Baden, Vienna, Austria, 1982.
7. Hadjipanayis, G.C., "Microstructure and Magnetic Domain Structure of 2:17 Permanent Magnets", 5ixth International Workshop on Rare Earth-Cobalt Permanent Magnets, Baden, Vienna, Austria, 1982.
8. Yoneyama, T., Tomizawa, S., Hori, T. and Ojima, T., "i~ew Type Rare Earth-Cobalt Magnets Based on Sm2(Co,Cu,Fe,M)17", Third International Workshop on Rare Earth-Cobalt Permanent Magnets, La Jolla, California, 1978.
g. Yoneyama, T., Fukuno, A. and Ojima, T., "Sm2(Co,Cu,Fe,Zr)l7 Magnets Having High iHC and (BH)maX", Third International Conference on Ferrites~ Kyoto, Japan, 1980.
10. Hadji~anayis, G.C., Hazelton, R.C., Wollins, S.H., Wysiekierski, A. and Lawless, K.R., "The Effect of Heat Treatment on the Microstructure and Magnetic Properties of a Sm(Co,Fe,Cu,Zr)7.2 Magnet", Sixth International Workshop on Rare Earth-Cobalt Permanent Magnets, Baden, Vienna, A~stria, 1982.
t~
11. Fidler, J. and Skalicky, P., I'Domain Wall Pinning in REPM", Proceedings of the Sixth Interna~ional Workshop on Rare Earth Cobalt Permanent Magnets, Vienna, Austria, September 1982.
12. Kronmuller, l~., "llucleation and Propagation of Reversed Domains in RE-Co-Magnets", Proceedings of the Sixth International Workshop on Rare Earth Cobalt Permanent Magnets, Vienna, Austria, September 1982~
13. Rabenberg, L., Mishra, R.K. and Thomas, C., "Development of the Cellular Microstructure in SmCo7.4 Type Magnets", Proceedings of the Sixth International Workshop on Rare Earth Cobalt Permanent Magnets, Vienna, Austria, September 1982.
14. Ray, A.E., "Metallurgical Behaviour of Sm (Co,Fe,Cu,Zr)z Alloys", J. Appl. Phys. 55 (6), 15 March 1984.
g. Yoneyama, T., Fukuno, A. and Ojima, T., "Sm2(Co,Cu,Fe,Zr)l7 Magnets Having High iHC and (BH)maX", Third International Conference on Ferrites~ Kyoto, Japan, 1980.
10. Hadji~anayis, G.C., Hazelton, R.C., Wollins, S.H., Wysiekierski, A. and Lawless, K.R., "The Effect of Heat Treatment on the Microstructure and Magnetic Properties of a Sm(Co,Fe,Cu,Zr)7.2 Magnet", Sixth International Workshop on Rare Earth-Cobalt Permanent Magnets, Baden, Vienna, A~stria, 1982.
t~
11. Fidler, J. and Skalicky, P., I'Domain Wall Pinning in REPM", Proceedings of the Sixth Interna~ional Workshop on Rare Earth Cobalt Permanent Magnets, Vienna, Austria, September 1982.
12. Kronmuller, l~., "llucleation and Propagation of Reversed Domains in RE-Co-Magnets", Proceedings of the Sixth International Workshop on Rare Earth Cobalt Permanent Magnets, Vienna, Austria, September 1982~
13. Rabenberg, L., Mishra, R.K. and Thomas, C., "Development of the Cellular Microstructure in SmCo7.4 Type Magnets", Proceedings of the Sixth International Workshop on Rare Earth Cobalt Permanent Magnets, Vienna, Austria, September 1982.
14. Ray, A.E., "Metallurgical Behaviour of Sm (Co,Fe,Cu,Zr)z Alloys", J. Appl. Phys. 55 (6), 15 March 1984.
Claims (13)
1. An Sm2 Co17 alloy consisting essentially of by weight 22.5 to 23.5% Sm as an effective amount, 20.0 to 25.0% Fe, 3.0 to 5.0% Cu. 1.4 to 2.0% Zr as an effective amount, minor amounts of oxygen and carbon, an additional amount of Sm in the range of from about 4 to about 9 times the oxygen content of the alloy, an additional amount of Zr in the range of from about 5 to about 10 times the carbon content of the alloy, the balance being cobalt, and said alloy having a crystallographic structure comprising cells of 2-17 Sm-Co rhombohedral phase surrounded by a continuous network of the 1-5 Sm-Co hexagonal phase, said alloy being magnetizable in a magnetizing field of about 25 kOe to produce a magnet having an energy product of at least 30 MGOe, and said alloy having been prepared by sintering a powder compact thereof in a sintering step at a temperature which is at least about 1200°C at at least the end of said sintering step to achieve a high density, cooling the sintered alloy to a solution heat treatment temperature marginally below the solid+liquid/solid phase transformation temperature in a controlled manner to put the alloy constituents into a substantially uniform 2-17 Sm-Co solid solution, holding the alloy at the solid solution heat treatment temperature, quenching the alloy to room temperature, reheating the alloy to a first aging temperature to transform the 2-17 Sm-Co solid solution into a structure comprising a network of the 1-5 Sm-Co phase within a 2-17 Sm-Co matrix, cooling the alloy to a second aging temperature in a controlled manner to cause regions of 2-17 Sm-Co phase to nucleate coherently within the 1-5 Sm-Co phase network, and cooling the alloy to room temperature.
2. An alloy according to claim 1 wherein the additional amount of Sm is about 6.265 times the oxygen content of the alloy.
3. An alloy according to claim 1 or claim 2 where-in the oxygen content of the alloy is not greater than about 0.6% by weight.
4. An alloy according to claim 1 wherein the addi-tional amount of Zr is about 7.595 times the carbon con-tent of the alloy.
5. An alloy according to claim 1 or claim 2 where-in the carbon content of the alloy is not greater than about 0.1% by weight.
6. An alloy according to claim 1 containing by weight 23.0% Sm as an effective amount, 22.0% Fe, 4.6%
Cu, 1.5% Zr as an effective amount, minor amounts of oxygen and carbon, said additional amount of Sm, said additional amount of Zr, and the balance being cobalt.
Cu, 1.5% Zr as an effective amount, minor amounts of oxygen and carbon, said additional amount of Sm, said additional amount of Zr, and the balance being cobalt.
7. An alloy according to claim 6 wherein the addi-tional amount of Sm is about 6.265 times the oxygen content of the alloy.
8. An alloy according to claim 6 or claim 7 where-in the oxygen content of the alloy is not greater than about 0.6% by weight.
9. An alloy according to claim 6 wherein the additional amount of Zr is about 7.595 times the carbon content of the alloy.
10. An alloy according to claim 6 or claim 9 wherein the carbon content of the alloy is not greater than about 0.1% by weight.
11. An alloy according to claim 1 wherein samarium is replaced partially by praseodymium.
12. An alloy according to claim 1 wherein zir-conium is replaced at least in part by another group lVB or VB transition element.
13. An alloy according to claim 12 wherein the 1.4-2.0% Zr as an effective amount is replaced by 2.7-4.0% Hf as an effective amount and the additional amount of zirconium is replaced by an additional amount of hafnium in the range of from about 10 to about 20 times the carbon content of the alloy.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8403752 | 1984-02-13 | ||
| GB848403752A GB8403752D0 (en) | 1984-02-13 | 1984-02-13 | Sm2 co17 alloys |
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| CA1252310A true CA1252310A (en) | 1989-04-11 |
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| CA000474046A Expired CA1252310A (en) | 1984-02-13 | 1985-02-11 | Sm.sub.2co in17 xx alloys suitable for use as permanent magnets |
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| JP (1) | JPS60211032A (en) |
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| JPS63236301A (en) * | 1987-03-25 | 1988-10-03 | Mitsubishi Metal Corp | Sintered r2co17 magnet having excellent characteristic |
| JPH02128404A (en) * | 1988-11-08 | 1990-05-16 | Fuji Elelctrochem Co Ltd | Manufacture of rare-earth permanent magnet |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5495918A (en) * | 1978-01-13 | 1979-07-28 | Tdk Corp | Permanent magnet material |
| JPS5620140A (en) * | 1979-07-24 | 1981-02-25 | Seiko Epson Corp | Permanent magnet material |
| JPS57131338A (en) * | 1981-02-09 | 1982-08-14 | Hitachi Metals Ltd | Permanent magnet alloy with low irreversible demagnetizability |
| JPS5822348A (en) * | 1981-08-01 | 1983-02-09 | Namiki Precision Jewel Co Ltd | Permanent magnet alloy |
| JPS59126733A (en) * | 1983-01-11 | 1984-07-21 | Seiko Instr & Electronics Ltd | Manufacture of rare earth element-cobalt magnet |
-
1984
- 1984-02-13 GB GB848403752A patent/GB8403752D0/en active Pending
-
1985
- 1985-02-11 CA CA000474046A patent/CA1252310A/en not_active Expired
- 1985-02-13 JP JP60026118A patent/JPS60211032A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60211032A (en) | 1985-10-23 |
| JPH0247534B2 (en) | 1990-10-22 |
| GB8403752D0 (en) | 1984-03-14 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |