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EP0632471B1 - Procédé de preparation d' un aimant permanent contenant du métal de terre rare, du bore et du fer - Google Patents

Procédé de preparation d' un aimant permanent contenant du métal de terre rare, du bore et du fer Download PDF

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Publication number
EP0632471B1
EP0632471B1 EP94108868A EP94108868A EP0632471B1 EP 0632471 B1 EP0632471 B1 EP 0632471B1 EP 94108868 A EP94108868 A EP 94108868A EP 94108868 A EP94108868 A EP 94108868A EP 0632471 B1 EP0632471 B1 EP 0632471B1
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Prior art keywords
alloy
permanent magnet
ingot
alloy ingot
sec
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EP94108868A
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German (de)
English (en)
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EP0632471A2 (fr
EP0632471A3 (fr
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Kazuhiko Yamamoto
Yuichi Miyake
Chikara Okada
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Santoku Corp
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Santoku Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/0433—Nickel- or cobalt-based alloys
    • C22C1/0441—Alloys based on intermetallic compounds of the type rare earth - Co, Ni
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered

Definitions

  • This invention relates to a process of preparing a permanent magnet with excellent magnetic properties containing a rare earth metal, boron and iron.
  • Permanent magnet alloy ingots are generally produced by a metal mold casting method consisting in casting molten alloy in a metal mold. If the molten alloy is to be solidified by the metal mold casting method, it is heat conduction through the casting mold that determines the rate of heat removal during the initial stage of the heat removal process for the molten alloy. However, as solidification proceeds, heat conduction between the casting mold and the solidified phase or in the solidifying phase determines the rate of heat conduction. Even though the cooling capacity of the metal mold is improved, the inner portions of the ingot and those portions of the ingot in the vicinity of the casting mold are subjected to different cooling conditions. Such phenomenon is the more pronounced, the thicker the ingot thickness.
  • the ingot is usually pulverized during the pulverization step in the magnet production process to a grain size of several microns.
  • the ingot produced by the above-mentioned metal mold casting process contains a phase rich in ⁇ -Fe and a coarse-grained rare earth metal rich phase, which are difficult to pulverize, there results non-uniform crystal grain distribution of the ingot powders produced on pulverization, with the result that orientation of magnetic domains and sinterability are lowered and hence the magnetic properties of the ultimate permanent magnet are deteriorated.
  • prismatic crystals having a short axis length of 0.1 to 50 ⁇ m and a long axis length of 0.1 to 100 ⁇ m are known to exist in the structure of the ingot produced by the above-mentioned metal mold casting method, the content of these crystals is minor and unable to influence the magnetic properties favorably.
  • an ingot having a more uniform composition may be produced with the above method than that produced by the metal mold casting method, since the components of the starting material consist in the combination of rare earth metal, cobalt and occasionally iron, copper and zirconium, the magnetic properties cannot be improved sufficiently by the strip casting method.
  • the conventional method of producing the alloy for the magnet by controlling only the cooling rate using the single roll or the twin roll, it is difficult to produce the prismatic crystal grain having the long axis length exceeding 100 ⁇ m. If the long axis length of the prismatic crystal grains is short, such that the mean diameter of the prismatic crystal grain is between 3 and 50 ⁇ m, the ultimate anisotropic permanent magnet becomes inferior in magnetic properties.
  • EP-A-0 556 751 which is a prior art document under Article 54(3) EPC to claim 1, describes an alloy ingot for permanent magnet consisting essentially of rare earth metal and iron, said alloy ingot containing 90 vol% or more of crystals having a crystal grain size along a short axis of 0.1 to 100 ⁇ m and that along a long axis of 0.1 to 100 ⁇ m and a method for producing an alloy ingot comprising melting a rare earth metal-iron alloy to obtain a molten alloy and solidifying the molten alloy uniformly at a cooling rate of 10 to 1,000°C/sec. at a subcooling degree of 10 to 500°C.
  • a process of preparing a permanent magnet comprising pulverizing, molding and sintering a starting material containing an alloy ingot.
  • the alloy ingot contains not less than 90% by volume of prismatic crystals each having a prismatic crystal grain size of 0.1 to 50 ⁇ m along a short axis thereof and a prismatic crystal grain size of larger than 100 ⁇ m and not larger than 300 ⁇ m along a long axis thereof, and is obtained by uniformly solidifying by a single roll method a molten alloy containing 25 to 31% by weight of a rare earth metal, 0.5 to 1.5% by weight of boron and iron under cooling conditions of a cooling rate of higher than 500°C/sec. and not higher than 10,000°C/sec. and a supercooling degree of 50 to 500°C, the cooling rate of 10 to 1,000°C/sec. being excluded.
  • the sole figure is a schematic view showing the production of an alloy ingot for a permanent magnet by a strip casting method using a single roll according to an embodiment of the present invention.
  • the permanent magnet is obtained by pulverizing, molding and sintering a starting material containing an alloy ingot synthesized by a specified production process, and exhibits superior anisotropy, while exhibiting a high degree of anisotropy and superior residual magnetic flux density and coercive force as compared to a magnet produced from a starting material of a prismatic crystal-containing alloy ingot produced under controlling the cooling rate.
  • the molten alloy for producing the alloy ingot, employed in the present invention contains 25 to 31 wt% of a rare earth metal, 0.5 to 1.5 wt% of boron, and iron, as essential ingredients.
  • the rare earth metals preferably include lanthanum, cerium, praseodymium, neodymium, yttrium, dysprosium, mischmetal, and mixtures thereof. If the content of the rare earth metal is less than 25 wt%, an iron-rich phase, such as ⁇ -iron phase, is precipitated in the produced alloy ingot, thereby adversely affecting the subsequent crushing process. If the content of the rare earth metal exceeds 31 wt%, the residual magnetic flux density is lowered.
  • the iron content is 67.5 to 74.5 wt%. However, if the molten alloy contains the additional components other than the essential components, the iron content is preferably at least 37.5 wt% or more. That is, the amount of the additional components is not more than 30 wt% and preferably not more than 10 wt% and more preferably not more than 6 wt%.
  • additional components include cobalt, aluminum, chromium, manganese, magnesium, silicon, copper, carbon, tin, tungsten, vanadium, zirconium, titanium, molybdenum, niobium, gallium and mixtures thereof. Of these, cobalt is most preferred. Inevitable impurities or trace components, such as oxygen, may also be contained besides these additional components.
  • the molten alloy may be prepared by, for example, vacuum melting, high frequency melting or the like, under an inert atmosphere, preferably using a crucible or the like.
  • the alloy ingot is produced under controlling the supercooling degree of the molten alloy to 50 to 500°C.
  • the lower limit of the supercooling degree is preferably controlled to 100°C for increasing the ratio of the length along the long axis to that along the short axis of the produced prismatic crystal and for improving the degree of anisotropy and dispersibility of the rare earth metal rich phase to thereby improve magnetic properties of the permanent magnet as an ultimate product.
  • the upper limit is controlled to 500°C for obtaining the length along the short axis of the produced prismatic crystals of not less than 0.1 ⁇ m and for improving the magnetic properties of the ultimate permanent magnet.
  • the molten alloy having such specified supercooling degree is uniformly solidified by the single roll method under cooling conditions exceeding 500°C/sec. and not higher than 10,000°C/sec. and preferably in a range of from 1,000 to 5,000°C/sec. for producing the desired alloy ingot.
  • the supercooling degree herein means a value defined by (melting point of the alloy) - (actual temperature of the molten alloy not higher than its melting point). More specifically, the supercooling means a phenomenon in which solidification is actually not produced even when the molten alloy is cooled down to the melting point of the alloy and, when the temperature is further lowered to a nucleation temperature, a fine-grained solid phase, that is a crystal, is formed in the molten alloy to initiate the solidification.
  • the supercooling degree means the difference between the melting point of the alloy and the actual temperature of the molten alloy lower than its melting point, as defined previously.
  • an alloy ingot which is hitherto not known and which has the content of not less than 90 vol% of a crystal having a crystal grain size within a range as specified subsequently may be produced by controlling the difference, that is the supercooling degree, of the molten alloy, to a range of from 50 to 500°C, and setting the cooling rate so as to exceed 500°C/sec. and so as not to exceed 10,000°C/sec.
  • the supercooling degree of the molten alloy may be controlled to the above-mentioned specified temperature by controlling the temperature of the molten alloy prepared using the aforementioned crucible and by suitably controlling the time and the feed rate of the molten alloy until the molten alloy reaches the single roll for solidification.
  • the molten alloy controlled to the above-mentioned specified supercooling degree may be solidified by the single roll method at the aforementioned specified cooling rate by controlling the number of revolutions and the surface temperature of the roll, the temperature of the atmosphere or the feed amount of the molten alloy to the roll for controlling the thickness of the produced alloy ingot.
  • the reason why the single roll method is adopted is that, with the twin roll method or the rotary disc method, the crystal growth direction or the cooling rate is difficult to control and a target crystal structure cannot be obtained, while the device itself is inferior in durability, and that with the single roll method the conditions of controlling the supercooling degree to the above-mentioned value and of continuously solidifying the molten alloy with the aforementioned specified cooling rate may be set more easily.
  • the alloy ingot preferably has a thickness ranging between 0.05 to 5 mm for more facilitated control of the cooling rate to the above-mentioned value.
  • the thickness of the alloy ingot in excess of 5 mm is not desirable because it becomes difficult to produce the alloy ingot having a desired crystal structure which will be explained subsequently.
  • the alloy ingot produced by the above-mentioned method contains not less than 90 vol% and preferably not less than 98 vol% of prismatic crystals each having a length along the short axis of 0.1 to 50 ⁇ m, preferably 1 to 20 ⁇ m, and a length along the long axis of exceeding 100 ⁇ m, preferably exceeding 150 ⁇ m and preferably not more than 300 ⁇ m and more preferably not more than 250 ⁇ m. It is particularly preferred that the alloy ingot be completely free from ⁇ -Fe and/or ⁇ -Fe usually contained as peritectic nuclei in the crystal grain of the main phase.
  • the alloy ingot contains ⁇ -Fe and/or ⁇ -Fe, it is desirable that such ⁇ -Fe and/or ⁇ -Fe have a grain size less than 10 ⁇ m and be present in a finely dispersed state.
  • Such crystal structure may be confirmed by a photograph taken with an electronic microscope. If the lengths along the long and short axes are outside of the above ranges, the ultimate permanent magnet is deteriorated in magnetic properties. Above all, if the length along the long axis is 100 ⁇ m or less, the prismatic crystal is lowered in the aspect ratio and the prismatic crystal becomes similar to the granular crystal while the degree of anisotropy is lowered such that high magnetic properties cannot be produced.
  • the content of the crystals having the above-mentioned crystal grain size is less than 90 vol%, superior magnetic properties cannot be afforded to the produced alloy ingot.
  • the ⁇ -Fe and/or ⁇ -Fe has a grain size not less than 10 ⁇ m, and is not dispersed finely, grain size distribution becomes nonuniform at the time of pulverization of the production process for the permanent magnet, while excellent anisotropy also cannot be produced.
  • the content of the alloy ingot is 70 to 99.9 vol% for further improving magnetic properties of the permanent magnet as an ultimate product.
  • an additional metal ingot may also be contained in the starting material in addition to the aforementioned alloy ingot.
  • Such additional metal ingot may preferably contain an additional rare earth metal, such as lanthanum, cerium, praseodymium, neodymium, yttrium, dysprosium, mischmetal or mixtures thereof, in an amount of 31 to 100 wt% based upon the amount of the additional metal ingot.
  • the additional metal ingot may contain not more than 69 wt% of, for example, iron, cobalt, nickel or mixtures thereof in addition to the rare earth metals.
  • Such additional metal ingot may be prepared by a method similar to the above-mentioned method for preparing the alloy ingot as the main component, while it may also be prepared by known metal casting methods, such as the twin roll method or rotary disc method. If the starting material contains the above-mentioned additional metal ingot, the resulting permanent magnet may be improved in magnetic properties than if the above-mentioned main component alloy ingot by itself is employed. The additional metal ingot contained in an amount exceeding 30 vol% based upon the amount of the starting material is not desirable in that the magnetic properties are thereby deteriorated.
  • the permanent magnet is prepared by pulverizing, molding and sintering the starting material containing the above-mentioned alloy ingot in a usual manner.
  • the above-mentioned pulverization may be performed by mechanically crushing the starting material by any known mechanical crushing means.
  • the starting material is crushed to 250 to 24 meshes and subsequently pulverized to a size of 10 ⁇ m or less and preferably to 2 to 3 ⁇ m.
  • Separate batches of the starting materials may also be pulverized and mixed so as to be supplied to the next proceeding molding step. If the starting material contains the additional metal ingot, the additional metal ingot and the main component metal ingot are preferably crushed separately and mixed and the resulting mixture is then pulverized to the above-mentioned particle size.
  • the alloy ingot has the specified polycrystal structure and is free from peritectic nuclei or is finely dispersed, it is possible to produce alloy powders having substantially homogeneous particle size easily in a shorter time, and to suppress the amount of oxygen otherwise mixed into the alloy powders during crushing. Such pulverization leads to improved magnetic properties of the ultimate permanent magnet.
  • the aforementioned molding may be carried out by usual compression molding in a magnetic field.
  • the strength of the magnetic field is preferably 1,200 KAm -1 or higher and more preferably 1,500 KAm -1 or higher, while the molding pressure is preferably 100 to 200 MPa.
  • sintering is performed under conditions of the temperature of 1,000 to 1,200°C for 0.5 to 5 hours in an inert gas atmosphere or in vacuum. Since the above-mentioned alloy powders are pulverized substantially homogeneously, the sintering may proceed smoothly, while the sintered product has a uniform crystal grain size.
  • the sintered mass may be heat-treated in any known method after sintering for further improving the magnetic properties. Such heat treatment may be conducted preferably under conditions of the temperature of 400 to 600°C and for 0.5 to 5 hours.
  • the permanent magnet is prepared by employing, as an essential component of the starting material, an alloy ingot of a novel crystal structure prepared by a specified production method, above all, the single roll method, under controlling the supercooling degree and the cooling rate of the molten alloy. Since the pulverizing step during production may be carried out easily, and the sintering proceeds satisfactorily, the permanent magnet is superior in magnetic properties, such as residual magnetic flux density or coercive force, and exhibits particularly excellent anisotropy. By employing the additional metal ingot bedsides the aforementioned main component alloy ingot, the permanent magnet itself may be given further improved magnetic properties. Thus the permanent magnet according to the present invention may be expected to be utilized in many fields in which a demand is raised for magnetic properties more excellent than those of the conventional permanent magnet.
  • a mixture of metals having the composition of 30.8 wt% of neodymium, 1.0 wt% of boron and 68.2 wt% of iron was melted by a high frequency melting method in an argon atmosphere using an alumina crucible.
  • the resulting molten mass maintained at a temperature of 1,350°C was processed in accordance with the following method, using an apparatus shown in Fig.1, in order to produce an alloy ingot for a permanent magnet.
  • the composition of the starting material is shown in Table 1.
  • Fig.1 is a schematic view showing an alloy ingot for a permanent magnet being prepared by a strip casting method employing a single roll.
  • a molten mass 2 melted by the high frequency melting method is contained in a crucible 1, and maintained at 1350°C.
  • the molten mass 2 was continuously poured on to a tundish 3 while the supercooling degree was adjusted to 200°C.
  • the molten mass 2 was supplied to a roll 4 rotated at a peripheral speed of approximately 3 m/sec.
  • the molten mass was allowed to solidify on the roll 4 so that the cooling rate of 1000°C/sec was maintained.
  • the molten mass 2 was allowed to descend continuously in the rotating direction of the roll 4 in order to produce an alloy ingot 5 having a thickness of 0.2 to 0.5 mm.
  • the supercooling degree and the cooling rate during the production of the alloy ingot and the grain size of the crystal structure of the alloy ingot as measured with the electron microscope are shown in Table 2, and the structural characteristics of the crystal structure as observed by the electron microscope are shown in Table 3. It is seen from the values of the mean diameter and the standard deviation of the crystal structure shown in Table 2 that the produced alloy ingot contains 90 vol% or more of the prismatic crystal grains having the prismatic crystal grain size of 0.1 to 50 ⁇ m along the short axis and more than 100 ⁇ m and not more than 300 ⁇ m along the long axis.
  • the produced alloy ingot for a permanent magnet was crushed to a size of 250 to 24 meshes and further pulverized in alcohol to approximately 3 ⁇ m.
  • the produced fine powders were molded in a magnetic field under conditions of 150 MPa and 2,400 KAm -1 and sintered for two hours at 1,040°C in order to produce a permanent magnet 10 ⁇ 10 ⁇ 15 mm in size.
  • the magnetic properties of the produced permanent magnet are shown in Table 4.
  • Samples of the permanent magnet were prepared in the same way as in Example 1 except employing the composition of the starting material shown in Table 1 and the supercooling degree and the cooling rate as shown in Table 2.
  • the crystal grain size of the alloy ingot, the structural characteristics of the crystal structure and the magnetic properties of the produced permanent magnet samples are shown in Tables 2, 3 and 4, respectively. It is seen from the values of the mean diameter and the standard deviation of the crystal structure shown in Table 2 that the produced alloy ingot contains 90 vol% or more of the prismatic crystal grains having the prismatic crystal grain size of 0.1 to 50 ⁇ m along the short axis and more than 100 ⁇ m and not more than 300 ⁇ m along the long axis.
  • a metal mixture having the same composition as that of Example 1 was melted by a high frequency melting method and cast by the metal mold casting method to produce an alloy ingot for a permanent magnet having a thickness of 25 mm.
  • the resulting alloy ingot was analyzed in the same way as in Example 1, and further processed to produce a permanent magnet.
  • the composition of the alloy ingot is shown in Table 1, while the supercooling degree, the cooling rate and the crystal grain size of the alloy ingot are shown in Table 2.
  • the structural characteristics of the crystal structure and the magnetic characteristics of the produced permanent magnet sample are shown in Tables 3 and 4, respectively.
  • a permanent magnet sample was prepared in the same way as in Example 1, except using the starting material composition shown in Table 1, employing the molten temperature of 1,200°C and the peripheral speed of the roll of 0.01 m/sec. and setting the supercooling degree and the cooling rate shown in Table 2.
  • the crystal grain size of the alloy ingot, the structural characteristics of the crystalline structure and the magnetic properties of the produced permanent magnet sample are shown in Tables 2, 3 and 4, respectively.
  • a permanent magnet sample was prepared in the same way as in Example 1, except using the starting material composition shown in Table 1, employing the molten temperature of 1,600°C and the peripheral speed of the roll of 50 m/sec. and setting the supercooling degree and the cooling rate shown in Table 2.
  • the crystal grain size of the alloy ingot, the structural characteristics of the crystalline structure and the magnetic properties of the produced permanent magnet sample are shown in Tables 2, 3 and 4, respectively.
  • An alloy ingot for a permanent magnet was prepared in the same way as in Comparative Example 1, except using the composition of the starting material shown in Table 1, and further processed to produce a permanent magnet.
  • the composition of the alloy ingot is shown in Table 1, while the supercooling degree, the cooling rate and the crystal grain size of the alloy ingot are shown in Table 2.
  • the structural characteristics of the crystalline structure and the magnetic characteristics of the produced permanent magnet sample are shown in Tables 3 and 4, respectively.
  • a metal mixture having a composition of 28.0 wt% of neodymium, 0.95 wt% of boron and 71.05 wt% of iron was melted in an argon atmosphere by a high frequency melting method, using an alumina crucible.
  • the produced molten mass was processed with the single roll method as in Example 1, under the supercooling degree and the cooling rate as shown in Table 5, in order to producer an alloy ingot for a main phase for the permanent magnet.
  • a metal mixture having a composition of 40.0 wt% of neodymium, 1.5 wt% of boron and 58.5 wt% of iron was melted in an argon atmosphere by a high frequency melting method, using an alumina crucible.
  • the produced molten mass was processed with the single roll method as in Example 1 under the supercooling degree and the cooling rate shown in Table 6, in order to producer a sintering assist alloy ingot for permanent magnet.
  • the composition of the main phase alloy ingot for permanent magnet and the composition of the sintering assist alloy ingot for permanent magnet are shown in upper and lower lines in each column for each Example shown in Table 5.
  • the main phase alloy ingot for permanent magnet and the sintering assist alloy ingot for permanent magnet thus produced were separately crushed to a size of 250 to 24 meshes in size and weighed out to give 83 wt% of the main phase alloy ingot for permanent magnet and 17 wt% of the sintering assist alloy ingot, which were mixed together and further pulverized in alcohol to a size in the order of 3 ⁇ m.
  • the produced fine powders were pressed in a magnetic field under conditions of 150 MPa and 2400 KAm -1 and sintered at 1040°C for two hours to produce a 10 ⁇ 10 ⁇ 15 mm size permanent magnet.
  • the supercooling degree and the cooling rate employed during preparation of the alloy ingots and the crystal grain size of the produced alloy ingots are shown in Table 6, while the structural characteristics of the alloy ingots and the mixing ratio of the main phase alloy ingot for permanent magnet and the sintering assist alloy ingot for permanent magnet are shown in Table 7 and the magnetic characteristics of the permanent magnet are shown in Table 8. It is seen from the values of the mean diameter and the standard deviation of the crystal structure shown in Table 6 that the produced alloy ingot contains 90 vol% or more of the prismatic crystal grains having the prismatic crystal grain size of 0.1 to 50 ⁇ m along the short axis and more than 100 ⁇ m and not more than 300 ⁇ m along the long axis.
  • a permanent magnet sample was prepared in the same way as in Example 4 except employing the compositions of the main phase alloy ingot for permanent magnet and the composition of the sintering assist alloy ingot for permanent magnet shown in Table 5 and employing the supercooling degree and cooling rate shown in Table 6 and the mixing ratio of the main phase alloy ingot for permanent magnet and the sintering assist alloy ingot for permanent magnet shown in Table 7.
  • the supercooling degree and the cooling rate employed during preparation of the alloy ingots and the crystal grain size of the produced alloy ingots are shown in Table 6, while the structural characteristics of the alloy ingots and the mixing ratio of the main phase alloy ingot for permanent magnet and the sintering assist alloy ingot for permanent magnet are shown in Table 7 and the magnetic characteristics of the permanent magnet are shown in Table 8.
  • the produced alloy ingot contains 90 vol% or more of the prismatic crystal grains having the prismatic crystal grain size of 0.1 to 50 ⁇ m along the short axis and more than 100 ⁇ m and not more than 300 ⁇ m along the long axis.
  • Permanent magnet alloy samples were prepared in the same way as in Example 4, except using the compositions of the main phase alloy ingots for permanent magnet and the sintering assist alloy ingots for permanent magnet shown in Table 5, and the supercooling degree and the cooling rate shown in Table 6. Besides, for preparing the permanent magnet alloy samples, each main phase alloy ingot for permanent magnet and each sintering assist alloy ingot for permanent magnet were crushed to produce crushed products, which were then pulverized separately and mixed together at a mixing ratio for the main phase alloy ingot for permanent magnet and the sintering assist alloy ingot for permanent magnet shown in Table 7 and molded in a magnetic field.
  • the supercooling degree and the cooling rate employed during preparation of the alloy ingots and the crystal grain size of the produced alloy ingots are shown in Table 6, while the structural characteristics of the alloy ingots and the mixing ratios of the main phase alloy ingots for permanent magnet and the sintering assist alloy ingots for permanent magnet are shown in Table 7 and the magnetic characteristics of the permanent magnets are shown in Table 8. It is seen from the values of the mean diameter and the standard deviation of the crystal structure shown in Table 6 that the produced alloy ingots contain 90 vol% or more of the prismatic crystal grains having the prismatic crystal grain size of 0.1 to 50 ⁇ m along the short axis and more than 100 ⁇ m and not more than 300 ⁇ m along the long axis.

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Claims (7)

  1. Procédé de préparation d'un aimant permanent comprenant la pulvérisation, le moulage et le frittage d'une matière première contenant un lingot d'alliage, obtenu par la solidification, réalisée uniformément, par une méthode à un seul rouleau, d'un alliage fondu comprenant 25 à 31 % en masse d'un métal de terre rare, 0,5 à 1,5 % en masse de bore et du fer, dans des conditions de refroidissement consistant en une vitesse de refroidissement supérieure à 500°C/seconde et ne dépassant pas 10 000°C/seconde et en un degré de surfusion situé entre 50 et 500°C, les vitesses de refroidissement de 10 à 1 000°C/seconde étant exclues.
  2. Procédé de préparation d'un aimant permanent comprenant la pulvérisation, le moulage et le frittage d'une matière première contenant un lingot d'alliage et un lingot métallique supplémentaire, dans lequel ladite matière première est constituée essentiellement par 70 à 99,9 % en volume d'un lingot d'alliage et par 0,1 à 30 % en volume d'un lingot métallique supplémentaire, et dans lequel ledit lingot d'alliage est obtenu par la solidification, réalisée uniformément, par une méthode à un seul rouleau, d'un alliage fondu comprenant 25 à 31 % en masse d'un métal de terre rare, 0,5 à 1,5 % en masse de bore et du fer, dans des conditions de refroidissement consistant en une vitesse de refroidissement supérieure à 500°C/seconde et ne dépassant pas 10 000°C/seconde et en un degré de surfusion situé entre 50 et 500°C, ledit lingot métallique supplémentaire comprenant 31 à 100% en masse, par rapport audit lingot métallique supplémentaire, d'un métal de terre rare supplémentaire, les vitesses de refroidissement de 10 à 1 000°C/seconde étant exclues.
  3. Procédé selon la revendication 1 ou 2, dans lequel ledit alliage fondu contient 67,5 à 74,5 % en masse de fer.
  4. Procédé selon la revendication 1 ou 2, dans lequel ledit alliage fondu contient 30 % en masse ou moins d'un composant supplémentaire choisi parmi le cobalt, l'aluminium, le chrome, le manganèse, le magnésium, le silicium, le cuivre, le carbone, l'étain, le tungstène, le vanadium, le zirconium, le titane, le molybdène, le niobium, le gallium et leurs mélanges, et 37,5 % en masse ou plus de fer.
  5. Procédé selon la revendication 1, dans lequel ladite matière première contient 70 à 99,9 % en volume dudit lingot d'alliage.
  6. Procédé selon la revendication 2, dans lequel ledit métal de terre rare supplémentaire est choisi parmi le lanthane, le cérium, le praséodyme, le néodyme, l'yttrium, le dysprosium, le mischmétal et leurs mélanges.
  7. Procédé selon la revendication 2, dans lequel ledit lingot métallique supplémentaire contient au plus 69 % en masse d'un métal supplémentaire choisi parmi le fer, le cobalt, le nickel et leurs mélanges.
EP94108868A 1993-06-14 1994-06-09 Procédé de preparation d' un aimant permanent contenant du métal de terre rare, du bore et du fer Expired - Lifetime EP0632471B1 (fr)

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JP142156/93 1993-06-14
JP14215693 1993-06-14

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EP0632471A2 EP0632471A2 (fr) 1995-01-04
EP0632471A3 EP0632471A3 (fr) 1995-02-15
EP0632471B1 true EP0632471B1 (fr) 1997-09-24

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KR (1) KR0151244B1 (fr)
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Publication number Priority date Publication date Assignee Title
DE69819953T2 (de) * 1997-03-25 2004-11-11 Alps Electric Co., Ltd. Auf Fe basierte hartmagnetische Legierung mit einer supergekühlter Spanne
EP0898287B1 (fr) 1997-08-22 2003-05-21 Alps Electric Co., Ltd. Alliage magnétiquement dur à région liquide surfondue,produit fritté de ceci et applications
JP3365625B2 (ja) * 1999-09-16 2003-01-14 住友特殊金属株式会社 ナノコンポジット磁石粉末および磁石の製造方法
WO2001091139A1 (fr) 2000-05-24 2001-11-29 Sumitomo Special Metals Co., Ltd. Aimant permanent a plusieurs phases ferromagnetiques et procede de production
CN1228158C (zh) 2000-10-06 2005-11-23 株式会社三德 使用薄带铸造法的纳米复合型永磁体用原料合金制造方法
US7217328B2 (en) 2000-11-13 2007-05-15 Neomax Co., Ltd. Compound for rare-earth bonded magnet and bonded magnet using the compound
US6790296B2 (en) 2000-11-13 2004-09-14 Neomax Co., Ltd. Nanocomposite magnet and method for producing same
JP4023138B2 (ja) 2001-02-07 2007-12-19 日立金属株式会社 鉄基希土類合金粉末および鉄基希土類合金粉末を含むコンパウンドならびにそれを用いた永久磁石
HU227736B1 (en) 2001-05-15 2012-02-28 Hitachi Metals Ltd Iron-based rare earth alloy nanocomposite magnet and method for producing the same
WO2003012802A1 (fr) 2001-07-31 2003-02-13 Sumitomo Special Metals Co., Ltd. Procede de production d'aimant nanocomposite a l'aide d'un procede d'atomisation
US7261781B2 (en) 2001-11-22 2007-08-28 Neomax Co., Ltd. Nanocomposite magnet
JP3602120B2 (ja) 2002-08-08 2004-12-15 株式会社Ｎｅｏｍａｘ ナノコンポジット磁石用急冷合金の製造方法
DE10328618B4 (de) * 2003-06-20 2008-04-24 Leibniz-Institut Für Festkörper- Und Werkstoffforschung Dresden E.V. Verfahren und Vorrichtung zur schmelzmetallurgischen Herstellung von Magnetlegierungen auf Nd-Fe-B-Basis
CN108133797B (zh) * 2017-12-18 2019-08-23 北京工业大学 一种抑制CeFe2相的混合稀土铁硼磁体的制备方法

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JPS63115304A (ja) * 1986-11-01 1988-05-19 Tdk Corp 高性能希土類鋳造磁石
JPH02118054A (ja) * 1988-10-26 1990-05-02 Seiko Epson Corp 永久磁石材料
JPH04147605A (ja) * 1990-10-11 1992-05-21 Hitachi Metals Ltd 希土類―鉄―硼素系永久磁石の製造方法
ATE167239T1 (de) * 1992-02-15 1998-06-15 Santoku Metal Ind Legierungsblock für einen dauermagnet, anisotropes pulver für einen dauermagnet, verfahren zur herstellung eines solchen und dauermagneten

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KR0151244B1 (ko) 1998-10-15
DE69405817D1 (de) 1997-10-30
KR950001790A (ko) 1995-01-03
EP0632471A2 (fr) 1995-01-04
EP0632471A3 (fr) 1995-02-15
ATE158669T1 (de) 1997-10-15
DE69405817T2 (de) 1998-01-15

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