EP0156482B1 - Alliages Sm2 CO17 utilisables comme aimants permanents - Google Patents

Alliages Sm2 CO17 utilisables comme aimants permanents Download PDF

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EP0156482B1
EP0156482B1 EP19850300957 EP85300957A EP0156482B1 EP 0156482 B1 EP0156482 B1 EP 0156482B1 EP 19850300957 EP19850300957 EP 19850300957 EP 85300957 A EP85300957 A EP 85300957A EP 0156482 B1 EP0156482 B1 EP 0156482B1
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alloy
phase
temperature
solid
solid solution
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EP0156482A1 (fr
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Andrew G. Wysierkierski
Robert W. Fraser
Maurice A. Clegg
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Viridian Inc Canada
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Sherritt Gordon Mines Ltd
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Priority claimed from GB848403751A external-priority patent/GB8403751D0/en
Priority claimed from GB848403752A external-priority patent/GB8403752D0/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/07—Alloys based on nickel or cobalt based on cobalt
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5

Definitions

  • This invention relates to Sm 2 Co 17 alloys suitable for use as permanent magnets.
  • rare earth cobalt alloy magnets are now well known. Such magnets are specially suitable for use in electric motors, such as DC servomotors. It is also known that SM 2 CO 17 alloys have potential advantages for use as permanent magnets over SmCo 5 alloys (1) . For example, DC motors using Sm 2 Co 17 alloy magnets have lower weight and inertia and increased torque and acceleration compared to the use of SmCo s alloy magnets.
  • SM 2 CO 17 alloys which can form magnets having an energy product (BH) max in the range of 22 to 30 MGOe and an intrinsic coercivity 1 H c in the range of 5.8 to 6.3 kOe (6, 7) .
  • BH energy product
  • Sm 2 Co 17 alloys which can produce magnets with higher coercivity, but this advantage has been offset by loss in energy product.
  • one Sm 2 CO 17 alloy is now known which can produce magnets having an energy product (BH) max of 26 MGOe and an intrinsic coercivity 1 H c of 15.0 kOe (7) .
  • Another Sm 2 CO 17 alloy now known has an energy product (BH) max of 27 MGOe and an intrinsic coercivity i H c of 10.0 kOe, see United States Patent No. 4,375,996 mentioned above (5) .
  • GB-A-2,089,371 discloses Sm 2 CO 17 containing resin- or metal-bonded permanent magnets obtained by first heat treating a bulk ingot to obtain magnetic properties, crushing and grinding the ingot to particles not larger than 50 um, and compacting these particles with a binder in a magnetic field.
  • a very wide range of alloys is disclosed, namely alloys containing
  • R 2 C O17 type permanent magnet alloys where R is a rare earth metal e.g. samarium, are disclosed to which hafnium is added to provide alloys with high coercive force even when the Cu content is low and the Fe content is high.
  • BH max values for the maximum energy product, range from 26 to 29.5 MGOe, coercive force, bHc, from 7.4 to 7.5 kOe, and magnetic remanence, Br, from 10.5 to 11.0 KG.
  • R 2 CO 17 type alloys in which the atomic ratios of the rare earth metal R (which is preferably Sm, but may alternatively be one or more other rare earth metals, including mixtures, for example, in which the Sm is at least partially replaced by praseodymium Pr), Cu, Fe and Hf (or other selected transition metal) are represented by the formula
  • Sm 2 CO 17 alloys are harder to magnetize from an unmagnetized state than SmCo 5 alloys.
  • SmCo 5 alloys are harder to magnetize from an unmagnetized state than SmCo 5 alloys.
  • SmCo 5 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.
  • 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 Sm 2 Co 17 alloys with an energy product greater than 30 MGOe (6) .
  • Sm 2 Co 17 alloys have potential advantages over other rare earth/transition metal alloys such as SmCo 5 alloys
  • Sm 2 CO 17 alloys have not yet become practically useful because improved coercivity has only been obtainable at the expense of energy product and also because such alloys have not been capable of attaining their specified properties in a magnetizing field up to about 25 kOe.
  • Sm 2 Co 17 alloys are provided which are suitable for use in the manufacture of permanent magnets of high energy product and high coercivity, such alloys consisting of, on a weight basis and apart from impurities:
  • the amounts of oxygen and carbon are "incidental", that is to say no attempt is made deliberately to incorporate oxygen and carbon into the alloy, the amounts of oxygen and carbon appearing in the alloy as a matter of course, and which are therefore inevitable in such compositions unless elaborate precautions are taken to exclude them.
  • the inevitability of such incidental amounts of oxygen and carbon in the alloy composition is recognised, and the invention recognises that it is necessary 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.
  • the additional amount of Sm is 6.265 times the oxygen content
  • the additional amount of Zr is preferably 7.595 times the carbon content.
  • the remainder of the alloy content is cobalt.
  • the function of the first specified amount of samarium, hereinafter referred to as the "effective samarium” is to develop the desired cryatallographic structure consisting of cells of the 2-17 Sm-Co rhombohedral 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 H K , and that is dependent upon the "effective samarium" present. Sufficient samarium must be present for this purpose but too much samarium results in the breakdown of the 2-17 rhombohedral phase and loss of remanent induction B r .
  • the function of the "effective samarium" present is therefore to develop the 2-17 Sm-Co rhombohedral phase having high remanent induction B, and to develop a complete 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 H K , and too much samarium results in a breakdown of the 2-17 Sm-Co phase and loss of remanent induction B, and energy product (BH) 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 first amount of zirconium, hereinafter likewise referred to as "effective zirconium” is to facilitate the dissolution of all the desired constituents 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 homogeneity 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 facilitates the accommodation of the desired elements in single phase solid solution during the solution heat treatment at 1140-1170°C.
  • 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 regarded 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 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 present invention.
  • an SM2CO1, alloy in accordance with the invention By using an SM2CO1, 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 of at least 30 MGOe and has a satisfactory coercivity H, of 14 to 16 kOe.
  • a magnet in accordance with the present invention can also have a satisfactory remanent induction B r of at least about 11.5 kG, and a better loop squareness in the second quadrant, i.e. H K of approximately 9.0 kOe.
  • a preferred alloy in accordance with the invention contains:
  • 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.
  • 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 Sm 2 CO 17 base alloy at a convenient stage in the processing, for example prior to compacting and sintering the alloy powder.
  • the master alloy may be of a simple form such as ferrozirconium, which is a low melting point (about 935°C) 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.
  • 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 compensation of zirconium content for carbon present and the optimum zirconium level at about 1.5%.
  • 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 picked up by the alloy during its manufacture and which have an adverse effect on the magnetic properties of the alloy.
  • 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 Sm 2 Co 17 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 compensation of samarium content for oxygen present and the optimum effective samarium in the range 22.5­23.5%.
  • 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 1.5%.
  • 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 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.
  • 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 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.
  • An Sm 2 CO 17 alloy in accordance with the invention is preferably made in the following manner.
  • the alloy of the desired composition was produced by pulverizing melted and cast alloy into particles of 3-8 11m 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 of 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 60 kpsi.
  • the green compact was sintered in hydrogen at 1150°C for 30 min.
  • the atmosphere was then changed to argon and the compact was heated to 1205°C at a rate of 4-5°C/min, held at 1205°C for 10 min and then cooled to 1160°C at 2°C/min.
  • the sample was then solution treated at 1140-1160°C for 2 hours, quenched from 1140-800°C at 10°C/s and air cooled from 800°C to room temperature. It was then reheated to 845 ⁇ 5°C and held for 20 hours, cooled at about 2°C/min from 845°C to about 600°C and at about 1°C/min from about 600°C to 410°C, held at 410°C for 10 hours and cooled to room temperature.
  • praseodymium can be substituted in part for samarium in the alloy of the present invention without decreasing the aforementioned desirable properties.
  • 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.
  • group IVB or VB transition elements may be substituted full or in part for zirconium in the alloy of the present invention. Since the function of 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 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 combination with carbon, account must be taken of the molecular weight of the transition metal carbide and the correction 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.
  • the aging temperature is critically dependent upon the zirconium content.
  • the optimum aging temperature and time may be different from those referred to above where Zr is the sole group IVB or VB element.
  • 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.
  • the carbon content of the alloy was multiplied by the factor 14.862.
  • the alloy was processed as described earlier for the standard alloy with the exception that after quenching from the solution temperature to room temperature the alloy was reheated to an aging temperature of 845 ⁇ 5°C and held there for 24 hours.
  • the following table illustrates the replacement of zirconium by hafnium as an effective amount.
  • the invention thus also provides an Sm2Co» 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 constituents of said alloy into a uniform single phase solid solution, an amount of iron being as high as possible to maximize the remanent induction of said alloy whilst still maintaining the single phase 2-17 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 nucle
  • composition must be based on the requirement that all the alloying elements are first put into a uniform solid solution.
  • optimum effective samarium content remained constant at 23 ⁇ 0.5%.
  • 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.
  • the alloys described above can be produced by means of a process in which a sintering step is followed by a solution treatment step, with the alloy being cooled from a sintering temperature to a solid solution treatment temperature in a controlled manner such that all the alloying elements are put into uniform solid solution.
  • a magnet in accordance with the present invention can also have a satisfactory remanent induction B r of at least about 11.5 kG and a better loop squareness in the second quadrant, i.e. H K of approximately 9.0 kOe.
  • the sintering temperature may be at least about 1200°C at at least the end of the sintering step.
  • the sintering temperature should be such that the alloy consists at that temperature of a mixture of liquid and solid phases to promote rapid sintering.
  • the predominant solid phase consists of 2-17 Sm-Co grains, with these being surrounded by a liquid phase comprising a CuSm phase which also contains a small amount of a Zr-rich phase.
  • the sintering process may be carried out in an inert atmosphere such as argon, or in hydrogen or in a vacuum, or in a combination of these.
  • an inert atmosphere such as argon, or in hydrogen or in a vacuum, or in a combination of these.
  • argon an atmosphere of argon
  • it is not practical to sinter entirely in a vacuum as excessive loss of samarium would result and the preferred procedure would be to sinter initially at a lower temperature in a vacuum and then change to an argon atmosphere before raising the temperature to the desired higher level.
  • the alloy may be sintered initially in an atmosphere of hydrogen at a somewhat lower temperature, for example 1150°C for 30 min, to close the internal porosity, followed by heating to the range of 1200­1215°C in an atmosphere of argon and holding at that temperature for 10 min.
  • the sintered alloy body is cooled in a controlled manner from the sintering temperature to a solid solution treatment temperature to ensure homogeneous equilibrium dissolution of the CuSm and Zr-rich phases into solid solution in the stable 2-17 Sm-Co phase.
  • a relatively high iron content renders such dissolution more difficult to achieve since the high iron content reduces the temperature range within which the stable 2-17 Sm-Co solid phase exists as a single phase.
  • the controlled cooling from the sintering temperature to the solution treatment temperature in accordance with the invention enables this problem to be overcome.
  • the alloy body After slow cooling to the solid solution treatment temperature, which is marginally below the solid+liquid/solid phase transformation temperature for the alloy composition and which may for example be from about 1140 to about 1150°C, the alloy body is maintained at this temperature for a period of time (for example about 2 hours) to improve the dissolution of the alloying elements and to remove any structural faults by annealing. The alloy body is then quenched from the solid solution treatment temperature to a temperature below 800°C at a rate of about 10°C/s, and thereafter to room temperature.
  • a temperature below 800°C at a rate of about 10°C/s, and thereafter to room temperature.
  • optionally part of the samarium may be replaced by praseodymium. In this case the solid+liquid/solid phase transformation temperature will be lower and the solid solution treatment temperature must be lower, in the range 1120-1145°C.
  • the alloy body is then aged to develop the 1-5 Sm-Co phase network.
  • the aging temperature will be generally in the range of 800-860°C but must be precisely chosen depending on the composition, in particular on the zirconium content.
  • a preferred aging temperature in the present invention is 845 ⁇ 5°Cfor 20 hours.
  • the alloy body After the aging step, it is necessary to cool the alloy body in a controlled manner to effect the required magnetic hardening, that is to say achieve the required intrinsic coercivity and good loop squareness.
  • Such controlled cooling may be from the aging temperature to about 600°C at a rate preferably about 2°C/min and from about 600°C to the secondary aging temperature in the region of 400°C at about 1°C/min.
  • a preferred secondary aging treatment in the present invention is 410°C for 10 hours. The alloy body is then cooled to room temperature.
  • An alloy body in accordance with one embodiment of the invention was produced in preliminary form with the following composition by weight: 22.7% effective Sm, 22.0% Fe, 4.6% Cu, 1.5% effective Zr, and balance cobalt.
  • the alloy body was sintered for 30 min in hydrogen at 1150°C, and for 10 min in argon at 1205°C. The sintered alloy body was then cooled to 1150°C at a rate of 2°C/min.
  • the alloy body was then subjected to solid solution treatment at a temperature of 1140 to 1150°C for 2 hours. After the solid solution treatment, the alloy body was quenched to room temperature. A micrograph showed that a uniform single phase solid solution structure was achieved.
  • the alloy body was then aged by reheating to 815°C and maintained at that temperature for 20 hours, then the alloy body was cooled to 600°C at a rate of 2°C/min and from 600° to 410°C at a rate of 1°C/min, held at 410°C for 10 hours and then cooled to room temperature.
  • a micrograph was taken and showed a uniform structure of 2-17 Sm-Co grains.
  • Another alloy body having the same composition as the previous alloy body was prepared and subjected to the same treatment as the previous alloy body, except that cooling from the sintering temperature to the solid solution treatment temperature was effected at a rapid rate of 10°C/s.
  • the alloy was then reheated to 815°C and aged as described above. A micrograph was taken and showed large grains constituting the 2-17 Sm-Co phase, with a CuSm black phase and a Zr-rich white phase being seen in the grain boundary area.
  • the alloy bodies were then magnetized in a magnetizing field of 25 kOe and the resulting magnetic properties were measured, as shown in the following Table.
  • a preferred sintering process is to sinter for 30 min in hydrogen at 1150°C, change the furnace atmosphere to argon, increase the temperature at 4-5°C/min to 1205°C and maintain this temperature for 10 min. It was observed that during the first sintering treatment the density of the product increases by pore closure with entrapment of some hydrogen. In the second sintering treatment in argon the internal hydrogen is removed by diffusion and the remaining pores are closed to full density.
  • transformation temperature The major influence on this transformation temperature is that observed for iron, for example, for alloys containing 15% Fe the transformation temperature was determined to be 1180°C, for 17% Fe, 1170°C and for 22% Fe, 1150°C, i.e. there is approximately 4°C decrease in transformation temperature for 1 % Fe increase in the range studied to date.
  • the alloy is quenched to room temperature and reheated to the aging temperature in the range of 800-860°C for up to 20 hours.
  • the 2-17 Sm-Co solid solution transforms into a duplex structure consisting of a continuous network of 1-5 Sm-Co phase within the 2-17 Sm-Co matrix.
  • the aging temperature must be precisely determined with respect to the zirconium content.
  • the optimum aging temperature was found to be 815 ⁇ 5°C for an effective zirconium content of 2.0-2.5%. For lower zirconium contents the aging temperature must be raised.
  • the optimum aging temperature was found to be 845 ⁇ 5°C for an effective zirconium content of 1.4­2.0%. It was found that a minimum time of about 20 hours is required at the aging temperature to form the required 1-5 Sm-Co phase network to develop the desired coercivity. Shorter times, i.e. 10 and 15 hours, result in lower coercivities and longer times, i.e. 30 hours, do not produce any further improvements.
  • H K loop squareness
  • the specimen Following this primary aging treatment at about 800-860°C the specimen must be cooled to the secondary aging temperature in the range 400-425°C at a critical rate.
  • the preferred cooling rate is about 2°C/min from the aging temperature to about 600°C and about 1°C/min from about 600°C to the secondary aging temperature. Small variations to the above do not appear to have a deleterious effect, however cooling rapidly such as >2°C/min or very slowly such as ⁇ 0.5°C/min resulted in inferior magnetic properties. It is postulated that during this critical cooling step regions of 2-17 Sm-Co phase nucleate coherently within the 1-5 Sm-Co phase network, thereby causing lattice strain and creating the coer C i V ity( 161 .
  • the aging process to develop coercivity shows an optimum temperature in the range of 400 ⁇ 450°C (16) . It was found that in 2-17 Sm-Co magnets in accordance with the invention in which coercivity and loop squareness (H K ) are being developed by aging the 1-5 Sm-Co phase network containing copper, the same effect applies.
  • the optimum aging temperature was found to be 410-4.15°C. With an aging temperature of 400°C for 10 hours a lower loop squareness (H K ) was obtained as was also the case at 422°C, as shown below.
  • the present invention also provides a process for producing an Sm 2 Co 17 alloy permanent magnet, containing also iron, copper and zirconium or a similar group IVB or VB transition metal, the process comprising: providing said alloy in a preliminary form, sintering said alloy at an elevated temperature to achieve a high density which results in a high remanence, selecting a solution treatment temperature which is marginally below the liquid+solid/solid phase transformation temperature for the preferred composition of said alloy, cooling the alloy from the elevated sintering temperature to the solution treatment temperature in a controlled manner such that all the alloy constituents are put into a uniform solid solution, holding at the solid solution treatment temperature, quenching the alloy to room temperature, reheating the alloy to the aging temperature, which is critically dependent on the composition of said alloy, particularly the zirconium content, and holding for sufficient time for the 2-17 Sm-Co solid solution to transform into a structure consisting of a continuous network of the 1-5 Sm-Co phase within the 2-17 Sm-Co matrix, cooling said alloy to the secondary aging temperature at

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Claims (14)

1. Un alliage de Sm2Co" utilisable dans la fabrication des aimants permanents d'énergie élevée et de coercitivité élevée, ledit alliage contenant du samarium, du fer, du cuivre, du zirconium, du cobalt et des quantités accidentelles de carbone et d'oxygène, caractérisé en ce que ledit alliage consiste, sur une base pondérale et abstraction faite des impuretés, en:
(a) une quantité de samarium qui est égale à 22,5 à 23,5% de l'alliage plus un pourcentage additionnel qui est égal à 4 à 9 fois la quantité d'oxygène;
(b) de 20,0 à 25,0% de Fe;
(c) de 3,0 à 5,0% de Cu;
(d) une quantité de zirconium qui est égale à 1,4 à 2,0% de l'alliage plus un pourcentage additionnel qui est égal à 5 à 10 fois la quantité de carbone;
(e) au plus 0,6% d'oxygène;
(f) au plus 0,1% de carbone; et
(g) le restant étant du cobalt; ledit alliage ayant une structure cristallographique comprenant des cellules de phase rhomboédrique 2-17 Sm-Co entourées par un réseau continu de phase hexagonale 1-5 Sm-Co, une telle structure étant procurable par:
(i) frittage d'un alliage de la composition chimique requise à une température à laquelle l'alliage consiste en la forme d'un mélange de solide/liquides, la phase solide consistant essentiellement en grains solides de 2-17 Sm-Co, et la phase liquide entourante comprenant une phase de CuSm et une phase riche en Zr;
(ii) refroidissement de l'alliage fritté lentement à une température de traitement de solution solide de façon marginale inférieure à la température de transformation solide+liquide/solide de l'alliage, pour former une solution solide homogène de ladite phase de CuSm et de ladite phase riche en Zr dans la phase 2-17 Sm-Co;
(iii) maintien de l'alliage à ladite température de traitement de solution solide pour favoriser la formation de ladite solution solide;
(iv) trempe de l'alliage depuis ladite température de traitement de solution à la température ambiante;
(v) réchauffage de l'alliage à une première température de vieillissement à laquelle la solution solide se transforme en une structure comprenant un réseau de la phase de 1-5 Sm-Co à l'intérieur d'une matrice de 2-17 Sm-Co;
(vi) refroidissement de l'alliage lentement à une seconde température de vieillissement pour provoquer la nucléation cohérente des régions de la phase de 2-17 Sm-Co à l'intérieur du réseau de phase de 1-5 Sm-Co et pour y créer ainsi une déformation du réseau; et
(vii) nouveau refroidissement de l'alliage à la température ambiante.
2. Un alliage selon la revendication 1, caractérisé en ce que la composition de l'alliage est la suivante:
(a) 23,0% de Sm plus un pourcentage additionnel qui est égal à 4 à 9 fois la quantité d'oxygène;
(b) 22,0% de Fe;
(c) 4,6% de Cu;
(d) 1,7% de Zr plus un pourcentage additionnel qui est égal à 5 à 10 fois la quantité de carbone;
(e) au plus 0,6% d'oxygène;
(f) au plus 0,1% de carbone; et
(g) le restant étant du cobalt.
3. Un alliage selon la revendication 1 ou 2, selon lequel la quantité additionnelle de Sm est de 6,265 fois la teneur en oxygène de l'alliage.
4. Un alliage selon la revendication 1, 2 ou 3, selon lequel la quantité additionnelle de Zr est de 7,595 fois la teneur en carbone de l'alliage.
5. Un alliage de SM2CO17, qui est un alliage tel que défini dans la revendication 1 et obtenu de la même façon, mais modifié par le fait que, au lieu de ladite quantité de 22,5 à 23,5% de samarium plus ladite quantité additionnelle, une certaine quantité de samarium est remplacée par le praséodyme sur la base d'un atome par atome.
6. Un alliage selon la revendication 5 qui contient 20% de Sm et de 2,5% de Pr plus ladite quantité additionnelle de samarium égale à 4 à 9 fois la teneur en oxygène de l'alliage.
7. Un alliage selon la revendication 5 ou 6, selon lequel la quantité additionnelle de Sm est de 5,871 fois la teneur en oxygène.
8. Un alliage de Sm2C017 qui est un alliage tel que défini dans la revendication 1 et obtenu de la même façon, mais modifié par le fait qu'au moins une certaine quantité de zirconium est remplacée par du hafnium sur la base d'un atome par atome.
9. Un alliage selon la revendication 8, selon lequel le zirconium est complètement remplacé par le hafnium, la quantité de hafnium dans l'alliage étant égale à 2,7 à 4,0% plus une quantité additionnelle qui est dans l'intervalle de 10 à 20 fois la teneur en carbone de l'alliage.
10. Un alliage selon la revendication 9, selon lequel la quantité additionnelle de Hf est de 14,862 fois la teneur en carbone de l'alliage.
11. Utilisation d'un alliage selon l'une quelconque des revendications précédentes comme aimant permanent.
12. Un procédé de production d'un alliage de Sm2Co" selon l'une quelconque des revendications 1-4, caractérisé en ce que le procédé comprend:
(i) la formation d'un alliage préliminaire ayant la composition requise;
(ii) le frittage de l'alliage préliminaire à une température à laquelle l'alliage consiste en la forme d'un mélange de solide/liquides, la phase solide consistant essentiellement en grains solides de 2-17 Sm-Co, et la phase liquide entourante comprenant une phase de CuSm et une phase riche en Zr;
(iii) le refroidissement de l'alliage fritté lentement à une température de traitement de solution solide de façon marginale inférieure à la température de transformation de solide+liquide/solide de l'alliage, pour former une solution solide homogène de ladite phase de CuSm et de ladite phase riche en Zr dans la phase de 2-17 Sm-Co;
(iv) le maintien de l'alliage à ladite température de traitement de solution solide pour favoriser la formation de ladite solution solide;
(v) la trempe de l'alliage depuis ladite température de traitement de solution à la température ambiante;
(vi) le réchauffage de l'alliage à une première température de vieillissement à laquelle ladite solution solide se transforme en une structure comprenant un réseau de la phase de 1-5 Sm-Co à l'intérieur d'une matrice de 2-17 Sm-Co;
(vii) le refroidissement de l'alliage lentement à une seconde température de vieillissement pour provoquer la nucléation cohérente des régions de la phase de 2-17 Sm-Co à l'intérieur du réseau de la phase 1-5 Sm-Co et pour y créer une déformation du réseau; et
(viii) un nouveau refroidissement de l'alliage à la température ambiante.
13. Un procédé de production d'un alliage de Sm2C017 selon la revendication 5, ou 7, caractérisé en ce que le procédé comprend:
(i) la formation d'un alliage préliminaire ayant la composition requise;
(ii) le frittage de l'alliage préliminaire à une température à laquelle l'alliage consiste en la forme d'un mélange de solide/liquides, la phase solide consistant essentiellement en grains solides de 2-17 Sm-Co, et la phase liquide entourante comprenant une phase de CuSm et une phase riche en Zr;
(iii) le refroidissement de l'alliage fritté lentement à une température de traitement de solution solide de façon marginale inférieure à la température de transformation de solide+liquide/solide de l'alliage, pour former une solution solide homogène de ladite phase de CuSm et de ladite phase riche en Zr dans la phase de 2-17 Sm-Co;
(iv) le maintien de l'alliage à ladite température de traitement de solution solide pour favoriser la formation de ladite solution solide;
(v) la trempe de l'alliage depuis ladite température de traitement en solution à la température ambiante;
(vi) le réchauffage de l'alliage à une première température de vieillissement à laquelle ladite solution solide se transforme en une structure comprenant un réseau de la phase de 1-5 Sm-Co à l'intérieur d'une matrice de 2-17 Sm-Co;
(vii) le refroidissement de l'alliage lentement à une seconde température de vieillissement pour provoquer la nucléation cohérente des régions de la phase de 2-17 Sm-Co à l'intérieur du réseau de la phase de 1-5 Sm-Co et pour y créer une déformation du réseau; et
(viii) un nouveau refroidissement de l'alliage à la température ambiante.
14. Un procédé de production d'un alliage de Sm2Co17 selon la revendication 8, ou 10, caractérisé en ce que le procédé comprend:
(i) la formation d'un alliage préliminaire ayant la composition requise;
(ii) le frittage de l'alliage préliminaire à une température à laquelle l'alliage consiste en la forme d'un mélange de solide/liquides, la phase solide consistant essentiellement en grains solides de 2-17 Sm-Co, et la phase liquide entourante comprenant une phase de CuSm et une phase riche en Zr;
(iii) le refroidissement de l'alliage fritté lentement à une température de traitement de solution solide de façon marginale inférieure à la température de transformation de solide+liquide/solide de l'alliage, pour former une solution solide homogène de ladite phase de CuSm et de ladite phase riche en Zr dans la phase de 2-17 Sm-Co;
(iv) le maintien de l'alliage à ladite température de traitement de solution solide pour favoriser la formation de ladite solution solide;
(v) la trempe de l'alliage depuis ladite température de traitement en solution à la température ambiante;
(vi) le réchauffage de l'alliage à une première température de vieillissement à laquelle ladite solution solide se transforme en une structure comprenant un réseau de la phase de 1-5 Sm-Co à l'intérieur d'une matrice de 2-17 Sm-Co;
(vii) le refroidissement de l'alliage lentement à une seconde température de vieillissement pour provoquer la nucléation cohérente des régions de la phase de 2-17 Sm-Co à l'intérieur du réseau de la phase de 1-5 Sm-Co et pour y créer une déformation du réseau; et
(viii) un nouveau refroidissement de l'alliage à la température ambiante.
EP19850300957 1984-02-13 1985-02-13 Alliages Sm2 CO17 utilisables comme aimants permanents Expired EP0156482B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85300957T ATE43363T1 (de) 1984-02-13 1985-02-13 Sm2 co17-legierungen, die fuer dauermagnete anwendbar sind.

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB848403751A GB8403751D0 (en) 1984-02-13 1984-02-13 Producing sm2 co17 alloy
GB8403752 1984-02-13
GB8403751 1984-02-13
GB848403752A GB8403752D0 (en) 1984-02-13 1984-02-13 Sm2 co17 alloys

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EP0156482A1 EP0156482A1 (fr) 1985-10-02
EP0156482B1 true EP0156482B1 (fr) 1989-05-24

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DE4015683A1 (de) * 1990-05-16 1991-11-21 Schramberg Magnetfab Legierung fuer permanentmagnete sowie verfahren zum hestellen von permanentmagneten aus dieser legierung

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IT1245838B (it) * 1990-11-15 1994-10-24 Getters Spa Motore elettrico senza spazzole e rotore relativo.
CN1198292C (zh) * 1998-10-30 2005-04-20 株式会社三德 Sm(Co,Fe,Cu,Zr,C)组合物及其制造方法
US6939628B2 (en) * 2002-07-23 2005-09-06 Hewlett-Packard Development Company, L.P. Method and apparatus for increasing fuel cell efficiency, power output, or reduced-temperature operation
US20060054245A1 (en) * 2003-12-31 2006-03-16 Shiqiang Liu Nanocomposite permanent magnets
CN105122388B (zh) 2014-03-18 2018-01-23 株式会社东芝 永磁体、电动机及发电机
CN111210960B (zh) * 2020-01-20 2022-05-31 苏州航大新材料科技有限公司 一种高方形度高磁能积钐钴永磁材料及制备方法

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JPS52155124A (en) * 1976-06-18 1977-12-23 Hitachi Metals Ltd Permanent magnetic alloy
JPS54104408A (en) * 1978-02-03 1979-08-16 Namiki Precision Jewel Co Ltd Rare earthhcobalt base permanent magnet alloy
JPS5814865B2 (ja) * 1978-03-23 1983-03-22 セイコーエプソン株式会社 永久磁石材料
US4172717A (en) * 1978-04-04 1979-10-30 Hitachi Metals, Ltd. Permanent magnet alloy
US4289549A (en) * 1978-10-31 1981-09-15 Kabushiki Kaisha Suwa Seikosha Resin bonded permanent magnet composition
JPS57100705A (en) * 1980-12-16 1982-06-23 Seiko Epson Corp Permanent magnet

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4015683A1 (de) * 1990-05-16 1991-11-21 Schramberg Magnetfab Legierung fuer permanentmagnete sowie verfahren zum hestellen von permanentmagneten aus dieser legierung

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EP0156482A1 (fr) 1985-10-02

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