EP1460650B1 - Seltenerdelement-permanentmagnet auf r-t-b-basis - Google Patents

Seltenerdelement-permanentmagnet auf r-t-b-basis Download PDF

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EP1460650B1
EP1460650B1 EP03748612A EP03748612A EP1460650B1 EP 1460650 B1 EP1460650 B1 EP 1460650B1 EP 03748612 A EP03748612 A EP 03748612A EP 03748612 A EP03748612 A EP 03748612A EP 1460650 B1 EP1460650 B1 EP 1460650B1
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rare earth
phase
alloys
weight
permanent magnet
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French (fr)
Japanese (ja)
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EP1460650A1 (de
EP1460650A4 (de
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Chikara Ishizaka
Gouichi Nishizawa
Tetsuya Hidaka
Akira Fukuno
Nobuya Uchida
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TDK Corp
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TDK Corp
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/005Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C33/00Making ferrous alloys
    • C22C33/02Making ferrous alloys by powder metallurgy
    • C22C33/0207Using a mixture of prealloyed powders or a master alloy
    • C22C33/0228Using a mixture of prealloyed powders or a master alloy comprising other non-metallic compounds or more than 5% of graphite
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C33/00Making ferrous alloys
    • C22C33/02Making ferrous alloys by powder metallurgy
    • C22C33/0257Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • C22C33/0278Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/06Ferrous alloys, e.g. steel alloys containing aluminium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/14Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032Magnets 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
    • H01F1/04Magnets 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
    • H01F1/047Alloys characterised by their composition
    • H01F1/053Alloys characterised by their composition containing rare earth metals
    • H01F1/055Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/0555Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together
    • H01F1/0557Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together sintered
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032Magnets 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
    • H01F1/04Magnets 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
    • H01F1/047Alloys characterised by their composition
    • H01F1/053Alloys characterised by their composition containing rare earth metals
    • H01F1/055Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571Alloys 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
    • H01F1/0575Alloys 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
    • H01F1/0577Alloys 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
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10Processes characterised by the sequence of their steps
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C2202/00Physical properties
    • C22C2202/02Magnetic

Definitions

  • the present invention relates to an R-T-B system rare earth permanent magnet containing, as main components, R (wherein R represents one or more rare earth elements, providing that the rare earth elements include Y), T (wherein T represents at least one transition metal element essentially containing Fe, or Fe and Co), and B (boron).
  • R represents one or more rare earth elements, providing that the rare earth elements include Y
  • T represents at least one transition metal element essentially containing Fe, or Fe and Co
  • B boron
  • rare earth permanent magnets an R-T-B system rare earth permanent magnet has been increasingly demanded year by year for the reasons that its magnetic properties are excellent and that its main component Nd is abundant as a source and relatively inexpensive.
  • Japanese Patent Laid-Open No. 1-219143 discloses that the addition of 0.02 to 0.5 at % of Cu improves magnetic properties of the R-T-B system rare earth permanent magnet as well as heat treatment conditions.
  • the method described in Japanese Patent Laid-Open No. 1-219143 is insufficient to obtain high magnetic properties required of a high performance magnet, such as a high coercive force (HcJ) and a high residual magnetic flux density (Br).
  • the magnetic properties of an R-T-B system rare earth permanent magnet obtained by sintering depend on the sintering temperature. On the other hand, it is difficult to equalize the heating temperature throughout all parts of a sintering furnace in the scale of industrial manufacturing. Thus, the R-T-B system rare earth permanent magnet is required to obtain desired magnetic properties even when the sintering temperature is changed.
  • a temperature range in which desired magnetic properties can be obtained is referred to as a suitable sintering temperature range herein.
  • Japanese Patent Laid-Open No. 2000-234151 discloses the addition of Zr and/or Cr to obtain a high coercive force and a high residual magnetic flux density.
  • Japanese Patent Laid-Open No. 2002-75717 discloses a method of uniformly dispersing a fine ZrB compound, NbB compound or HfB compound (hereinafter referred to as an M-B compound) into an R-T-B system rare earth permanent magnet containing Zr, Nb or Hf as well as Co, Al and Cu, followed by precipitation, so as to inhibit the grain growth in a sintering process and to improve magnetic properties and the suitable sintering temperature range.
  • the suitable sintering temperature range is extended by the dispersion and precipitation of the M-B compound.
  • the suitable sintering temperature range is narrow, such as approximately 20°C. Accordingly, to obtain high magnetic properties using a mass-production furnace or the like, it is desired to further extend the suitable sintering temperature range.
  • it is effective to increase the additive amount of Zr. However, as the additive amount of Zr increases, the residual magnetic flux density decreases, and thus, high magnetic properties of interest cannot be obtained
  • Pollard R J et al (IEEE Trans. On Magnetics, US, vol.24, no.2, p.1626/8 ) relates to the effect of Zr additions on the micro structural and magnetic properties of NdFeB based magnets.
  • Benesicar et al (Journal of magnetism and magnetic materials, Elsevier Sc.Publ., NL, vol. 104-107, part 2, p. 1175/8 ) discusses the influence of ZrO 2 addition on the microstructure and the magnetic properties of NdDyFeB magnets.
  • the present inventor has found that when a product that is rich in Zr exists in an R 2 T 14 B phase constituting the main phase of an R-T-B system rare earth permanent magnet, the permanent magnet enables to inhibit the grain growth, while keeping a decrease in magnetic properties to a minimum, and to improve the suitable sintering temperature range.
  • the present invention provides an R-T-B system rare earth permanent magnet, which is a sintered body consisting of 28% to 33% by weight of R, 0.5% to 1.5% by weight of B, 0.03% to 0.3% by weight of Al, 0.03% to 0.3% by weight of Cu, 0.05% to 0.2% by weight or Zr, 0.1% to 4% by weight of Co, and the balance being Fe and unavoidable impurities; said sintered body comprising a main phase consisting of an R 2 T 14 B phase, wherein R represents one or more rare earth elements providing that the rare earth elements include Y, and T represents one or more transition metal elements containing Fe, or Fe and Co, and a grain boundary phase containing a higher amount of R than the above main phase, wherein a product that is rich in Zr exists in the above R 2 T 14 B phase and has a length of several hundreds nm and a width between several nm and 15 nm.
  • R represents one or more rare earth elements providing that the rare earth elements include Y
  • T represents one
  • the product that is rich in Zr has a platy or acicular form.
  • the amount of oxygen contained in the above sintered body is preferably 2, 000 ppm or less. This is because effects obtained by the presence of the Zr rich product in the R 2 T 14 B phase, such as the inhibition of the grain growth or the extension of the suitable sintering temperature range become significant, when the amount of oxygen contained in the sintered body is as low as 2,000 ppm or less.
  • the sintered body preferably has a composition consisting of 28% to 33% by weight of R, 0.5% to 1.5% by weight of B, 0.03% to 0.3% by weight of Al, 0.03% to 0.3% by weight of Cu, 0.05% to 0.2% by weight of Zr, 0.1% to 4% by weight of Co, and the balance substantially being Fe.
  • Zr is contained in the sintered body, more preferably within the range between 0. 1% and 0.15% by weight.
  • the R-T-B system rare earth permanent magnet of the present invention comprises a sintered body consisting essentially of 28% to 33% by weight of R, 0.5% to 1.5% by weight of B, 0.03% to 0.3% by weight of Al, 0.08% to 0.3% by weight of Cu, 0.05% to 0.2% by weight or Zr, 0.1% to 4% by weight of Co, and the balance being Fe and unavoidable impurities, said sintered body comprising a main phase consisting of a R 2 T 14 B phase (wherein R represents one or more rare earth elements (providing that the rare earth elements include Y), and T represents one or more transition metal elements containing Fe, or Fe and Co), and a grain boundary phase containing a higher amount of R than the main phase.
  • the present invention is characterized in that a product that is rich in Zr, and which has a length of several hundreds nm and a width between several nm and 15 nm, exists in the R 2 T 14 B phase.
  • the R-T-B system rare earth permanent magnet containing this product enables to inhibit the grain growth, while keeping a decrease in magnetic properties to a minimum, and to extend the suitable sintering temperature range.
  • This product needs to exist in the R 2 T 14 B phase, but it is not required to exist in all the R 2 T 14 B phases. This product may exist also in the grain boundary phase. However, when the Zr rich product exists only in the grain boundary phase, the effects of the present invention cannot be obtained.
  • Ti has conventionally been known as an additive element that forms the product in the R 2 T 14 B phase (e.g., J. Appl. Phys. 69 (1991) 6055 ).
  • the present inventors have found that the formation of the product in the R 2 T 14 B phase by addition of Zr or Ti is effective for the extension of a suitable sintering temperature range.
  • Zr although Zr is added in an amount necessary to obtain such an effect as the extension of a suitable sintering temperature range, it causes almost no decrease in magnetic properties, and more specifically, almost no decrease in the residual magnetic flux density (Br).
  • the present inventors have confirmed that in order to allow the product that is rich in Zr to exist in the R 2 T 14 B phase, there are several requirements on the manufacturing method.
  • the procedure of the manufacturing method of the permanent magnet of the present invention will be described later.
  • the requirements to allow the Zr rich product to exist in the R 2 T 14 B phase will be explained below.
  • an R-T-B system rare earth permanent magnet There are two methods for manufacturing an R-T-B system rare earth permanent magnet: a method of using as a starting alloy a single alloy having a desired composition (hereinafter referred to as a single method), and amethodof using as starting alloys a plurality of alloys having different compositions (hereinafter referred to as a mixing method).
  • a mixing method alloys containing an R 2 T 14 B phase as a main constituent (low R alloys) and alloys containing a higher amount of R than the low R alloys (high R alloys) are typically used, as starting alloys.
  • the present inventors added Zr to either the low R alloys or the high R alloys, so as to obtain an R-T-B system rare earth permanent magnet.
  • the present inventors confirmed that when Zr is added to the low R alloys in order to produce a permanent magnet, the product that is rich in Zr exists in the R 2 T 14 B phase.
  • the present inventors also confirmed that when Zr is added to the high R alloys, the Zr rich product does not exist in the R 2 T 14 B phase.
  • the peripheral velocity of a chill roll needs to be controlled.
  • the peripheral velocity of a chill roll is low, it results in the deposition of ⁇ -Fe, and the Zr rich product is generated in the R 2 T 14 B phase of the low R alloys.
  • the peripheral velocity of a chill roll is within the range between 1.0 and 1.8 m/s, low R alloys in which the Zr rich product do not exist in the R 2 T 14 B phase can be obtained.
  • a permanent magnet with high magnetic properties can be obtained.
  • the obtained low R alloys are subjected to a heat treatment and then used as mother alloys. This is because the Zr rich product is generated in the R 2 T 14 B phase of the low R alloys as a result of undergoing a heat treatment in a temperature area (approximately 700°C or higher) where the microstructure of the low R alloys may be modified.
  • the term chemical composition is used herein to mean a chemical composition obtained after sintering.
  • the rare earth permanent magnet of the present invention contains 28% to 33% by weight of R.
  • R is used herein to mean one or more rare earth elements selected from a group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu and Y. If the amount of R is less than 28% by weight, an R 2 T 14 B 1 phase as a main phase of the rare earth permanent magnet is not sufficiently generated. Accordingly, ⁇ -Fe or the like having soft magnetism is deposited and the coercive force significantly decreases. On the other hand, if the amount of R exceeds 35% by weight, the volume ratio of the R 2 T 14 B phase as a main phase decreases, and the residual magnetic flux density decreases.
  • the amount of R exceeds 33% by weight, R reacts with oxygen, and the content of oxygen thereby increases.
  • an R rich phase effective for the generation of coercive force decreases, resulting in a reduction in the coercive force. Therefore, the amount of R is set between 28% and 33% by weight.
  • the amount of R is preferably between 29% and 32% by weight.
  • Nd is abundant as a source and relatively inexpensive, it is preferable to use Nd as a main component of R. Moreover, since the containment of Dy increases an anisotropic magnetic field, it is effective to contain Dy to improve the coercive force. Accordingly, it is desired to select Nd and Dy for R and to set the total amount of Nd and Dy between 28% and 33% by weight. In addition, in the above range, the amount of Dy is preferably between 0.1% and 8% by weight. It is desired that the amount of Dy is arbitrarily determined within the above range, depending on which is more important, a residual magnetic flux density or a coercive force.
  • the amount of Dy is preferably set between 0.1% and 3.5% by weight.
  • the amount of Dy is preferably set between 3.5% and 8% by weight.
  • the rare earth permanent magnet of the present invention contains 0.5% to 1.5 % by weight of boron (B). If the amount of B is less than 0.5% by weight, a high coercive force cannot be obtained. However, if the amount of B exceeds 1.5% by weight, the residual magnetic flux density is likely to decrease. Accordingly, the upper limit is set at 1.5% by weight.
  • the amount of B is preferably between 0.8% and 1.2% by weight.
  • the R-T-B system rare earth permanent magnet of the present invention may contain Al and Cu within the range between 0.03% and 0.3% by weight.
  • the containment of Al and Cu within the above range can impart a high coercive force, a strong corrosion resistance, and an improved temperature stability of magnetic properties to the obtained permanent magnet.
  • the additive amount of Al is preferably between 0.05% and 0.25% by weight.
  • the additive amount of Cu is preferably between 0.03% and 0.15%, and more preferably between 0.03% and 0.08% by weight.
  • the R-T-B system rare earth permanent magnet of the present invention contains Zr within the range between 0.05% and 0.2% by weight.
  • Zr exerts the effect of inhibiting the abnormal grain growth in a sintering process and thereby makes the microstructure of the sintered body uniform and fine. Accordingly, when the amount of oxygen is low, Zr fully exerts its effect.
  • the amount of Zr is preferably between 0.1% and 0.15% by weight.
  • the R-T-B system rare earth permanent magnet of the present invention contains 2,000 ppm or less oxygen. If it contains a large amount of oxygen, an oxide phase that is a non-magnetic component increases, thereby decreasing magnetic properties.
  • the amount of oxygen contained in a sintered body is set at 2,000 ppm or less, preferably 1,500 ppm or less, and more preferably 1,000 ppm or less.
  • the amount of oxygen is simply decreased, an oxide phase having a grain growth inhibiting effect decreases, so that the grain growth easily occures in a process of obtaining full density increase during sintering.
  • the R-T-B system rare earth permanent magnet to contains a certain amount of Zr, which exerts the effect of inhibiting the abnormal grain growth in a sintering process.
  • the R-T-B system rare earth permanent magnet of the present invention contains Co in an amount of 0.1% and 4% by weight, preferably between 0.1% and 2.0% by weight, and more preferably between 0.3% and 1.0% by weight. Co forms a phase similar to that of Fe. Co has an effect to improve Curie temperature and the corrosion resistance of a grain boundary phase.
  • Embodiments of the present invention show a method for manufacturing a rare earth permanent magnet using alloys (low R alloys) containing an R 2 T 14 B phase as a main phase and other alloys (high R alloys) containing a higher amount of R than the low R alloys.
  • Raw material is first subjected to strip casting in a vacuum or an inert gas atmosphere, or preferably an Ar atmosphere, so that low R alloys and high R alloys are obtained.
  • a vacuum or an inert gas atmosphere or preferably an Ar atmosphere
  • the peripheral velocity of a chill roll is set within the range between 1.0 and 1.8 m/s.
  • the preferred peripheral velocity of a chill roll is between 1.2 and 1.5 m/s.
  • the feature of the present embodiment is that Zr is added to low R alloys.
  • the reason is that the Zr rich product can be allowed to exist in the R 2 T 14 B phase of the R-T-B system rare earth permanent magnet by adding Zr to low R alloys containing no Zr rich products in an R 2 T 14 B phase thereof.
  • the low R alloys can contain Cu and Al, in addition to rare earth elements, Fe, Co and B.
  • the high R alloys can also contain Cu and Al, in addition to rare earth element, Fe, Co and B.
  • each of the master alloys is crushed to a particle size of approximately several hundreds of ⁇ m.
  • the crushing is preferably carried out in an inert gas atmosphere, using a stamp mill, a jaw crusher, a brown mill, etc. In order to improve rough crushability, it is effective to carry out crushing after the absorption of hydrogen. Otherwise, it is also possible to release hydrogen after absorbing it and then carry out crushing.
  • the routine proceeds to a pulverizing process.
  • a jet mill is mainly used, and crushed powders with a particle size of approximately several hundreds of ⁇ m are pulverized to a mean particle size between 3 and 5 ⁇ m.
  • the jet mill is a method comprising releasing a high-pressure inert gas (e.g., nitrogen gas) from a narrow nozzle so as to generate a high-speed gas flow, accelerating the crushed powders with the high-speed gas flow, and making crushed powders hit against each other, the target, or the wall of the container, so as to pulverize the powders.
  • a high-pressure inert gas e.g., nitrogen gas
  • the pulverized low R alloy powders are mixed with the pulverized high R alloy powders in a nitrogen atmosphere.
  • the mixing ratio of the low R alloy powders and the high R alloy powders may be approximately between 80 : 20 and 97 : 3 at a weight ratio.
  • the mixing ratio may be approximately between 80 : 20 and 97 : 3 at a weight ratio.
  • mixed powders comprising of the low R alloy powders and the high R alloy powders are filled in a tooling equipped with electromagnets, and they are compacted in a magnet field, in a state where their crystallographic axis is oriented by applying a magnetic field.
  • This compacting may be carried out by applying a pressure of approximately 0.7 to 1.5 t/cm 2 in a magnetic field of 12.0 to 17.0 kOe.
  • the compacted body is sintered in a vacuum or an inert gas atmosphere.
  • the sintering temperature needs to be adjusted depending on various conditions such as a composition, a crushing method, the difference between particle size and particle size distribution, but the sintering may be carried out at 1, 000°C to 1,100°C for about 1 to 5 hours.
  • the Zr rich product is generated in the R 2 T 14 B phase in this sintering process.
  • the mechanism of generating after sintering the Zr rich product that did not exist in the low R alloy stage is unknown, but there is a possibility that Zr dissolved in the R 2 T 14 B phase in the low R alloy stage might be deposited therein during the sintering process.
  • the obtained sintered body may be subjected to an aging treatment.
  • the aging treatment is important for the control of a coercive force.
  • the aging treatment is carried out in two steps, it is effective to retain the sintered body for a certain time at around 800°C and around 600°C.
  • the coercive force increases. Accordingly, it is particularly effective in the mixing method.
  • the coercive force significantly increases. Accordingly, when the aging treatment is carried out in a single step, it is appropriate to carry out it at around 600°C.
  • An R-T-B system rare earth permanent magnet was manufactured by the following manufacturing process.
  • Mother alloys (strips) having compositions and thicknesses shown in FIG. 1 were prepared by the strip casting method.
  • the roll peripheral velocity of low R alloys was set to 1.5 m/s, and that of high R alloys was set to 0. 6m/s.
  • the roll peripheral velocity of the low R alloys in Comparative Example 3 shown in FIG. 1 was set to 0.6 m/s.
  • the thickness of alloys was a mean value obtained by measuring the thicknesses of 50 strips. It was confirmed that a Zr rich product (hereinafter referred to as an intraphase product) was not observed in the R 2 T 14 B phase of the low R alloys of Example 1 as shown in FIG. 1, but that the intraphase product existed in the R 2 T 14 B phase of the low R alloys of Comparative Example 3 as shown in the same figure.
  • an intraphase product hereinafter referred to as an intraphase product
  • a hydrogen crushing treatment was carried out, in which after hydrogen was absorbed at room temperature, dehydrogenation was carried out thereon at 600°C for 1 hour in an Ar atmosphere.
  • the atmosphere was controlled at an oxygen concentration less than 100 ppm throughout processes, from a hydrogen treatment (recovery after a crushing process) to sintering (input into a sintering furnace).
  • two-step crushing is carried out, which includes crushing process and pulverizing process.
  • the crushing process was omitted in the present Examples.
  • Example 1 and Comparative Examples 1 to 3 Before carrying out the pulverizing process, 0.05% by weight of zinc stearate was added. Thereafter, using a Nauta Mixer, the low R alloys were mixed with the high R alloys for 30 minutes in the combination of each of Example 1 and Comparative Examples 1 to 3 as shown in FIG. 1. In all of Example 1 and Comparative Examples 1 to 3, the mixing ratio between the low R alloys and the high R alloys was 90 : 10.
  • the mixture was subjected to the pulverizing with a jet mill to a mean particle size of 4.8 to 5.1 ⁇ m.
  • the obtained fine powders were compacted in a magnetic field of 15.0 kOe by applying a pressure of 1.2 t/cm 2 , so as to obtain a compacted body.
  • the obtained compacted body was sintered at 1, 070°C for 4 hours in a vacuum atmosphere, followed by quenching. Thereafter, the obtained sintered body was subjected to a two-step aging treatment consisting of treatments of 800°C ⁇ 1 hour and 550°C ⁇ 2.5 hours (both in an Ar atmosphere).
  • FIGS. 2 to 5 The magnetic properties of the obtained permanent magnets were measured with a B-H tracer. The results are shown in FIGS. 2 to 5.
  • Br represents a residual magnetic flux density
  • HcJ represents a coercive force
  • Hk/HcJ means a squareness.
  • the squareness (Hk/HcJ) is an index of magnetic performance, and it represents an angular degree in the second quadrant of a magnetic hysteresis loop.
  • Hk means an external magnetic field strength obtained when the magnetic flux density becomes 90% of the residual magnetic flux density in the second quadrant of a magnetic hysteresis loop.
  • the product is not contained in the R 2 T 14 B phase, but it exists independently from the R 2 T 14 B phase. Accordingly, it is considered that in the R-T-B system rare earth permanent magnet of Comparative Example 3, the Zr rich product exists only in the grain boundary phase even after the sintering process.
  • FIG. 6 is a TEM photograph of a sample containing 0.10% by weight of Zr.
  • FIG. 7 is a set of EDS (Energy Dispersive X-ray Fluorescence Spectrometer) profiles of a product existing in the sample and the R 2 T 14 B phase of the sample.
  • FIG. 8 is a high resolution TEM photograph of the sample.
  • FIG. 6 an intraphase product with a large axis ratio can be observed in the R 2 T 14 B phase.
  • This product has a platy or acicular form.
  • FIG. 6 is a photograph obtained by observing the cross section of the sample, and it is therefore difficult to determine from such observation whether the form is platy or acicular.
  • the intraphase product has a length of several hundreds nm and a width between several nm and 15 nm.
  • the detailed chemical composition of this intraphase product is uncertain, but from FIG. 7A, it can be confirmed that the intraphase product is at least rich in Zr.
  • indefinite or round shape intraphase products can also be observed, as shown in FIGS. 9 and 10.
  • intraphase products were observed in 6 crystal grains thereof.
  • no intraphase products were observed in any of 20 crystal grains (R 2 T 14 B phase).
  • the lower image of FIG. 11A shows the Zr mapping results of a sample containing 0.10% by weight of Zr of Example 1 by EPMA (Electron Probe Micro Analyzer).
  • the upper image of FIG. 11A shows a composition image in the same scope as the Zr mapping results shown in the lower image of FIG. 11A.
  • the lower image of FIG. 11B shows the Zr mapping results of a sample containing 0.10% by weight of Zr of Comparative Example 2 by EPMA.
  • the upper image of FIG. 11B shows a composition image in the same scope as the Zr mapping results shown in the lower image of FIG. 11B.
  • FIG. 11A As with the results obtained by the observation by TEM, it is found from FIG. 11A that an R 2 T 14 B phase that is rich in Zr is present in the permanent magnet of Example 1, and that Zr exists also in a grain boundary phase thereof. In contrast, it is found from FIG. 11B that such a Zr rich R 2 T 14 B phase is not observed in the permanent magnet of Comparative Example 2, and that Zr exists only in a grain boundary phase thereof.
  • R-T-B system rare earth permanent magnets were obtained in the same manner as in Embodiment Example 1 with the exception that samples each containing 0.10% by weight of additive element M (Zr or Ti) of the composition of the sintered body were sintered for 4 hours within the temperature range between 1,010°C and 1,090°C.
  • the magnetic properties of the obtained permanent magnets were measured in the same manner as in Embodiment Example 1. The results are shown in FIG. 12.
  • changes in the magnetic properties by changes in the sintering temperature are shown in FIGS. 13 to 15.
  • the magnetic properties at each sintering temperature plotted as a squareness (Hk/HcJ) to a residual magnetic flux density (Br) are shown in FIG. 16.
  • Example 2 of the present invention a residual magnetic flux density (Br) of 13.9 kG or greater, a coercive force (HcJ) of 13.0 kOe or greater, and a squareness (Hk/HcJ) of 95% or more can be obtained in the sintering temperature range between 1,030°C and 1,090°C. If Ti is added as an additive element M, the residual magnetic flux density (Br) decreases (Comparative Example 4). Moreover, when no intraphase products exist, the squareness (Hk/HcJ) is poor, and the suitable sintering temperature range is narrow (Comparative Example 5).
  • the low R alloys were mixed with the high R alloys for 30 minutes in the combinations as shown in FIG. 17. Thereafter, the mixture was subjected to the pulverizing with a jet mill to a mean particle size of 4.1 ⁇ m.
  • the obtained fine powders were compacted in a magnetic field under the same conditions as in Embodiment Example 1, followed by sintering at 1,010°C to 1,090°C for 4 hours. Thereafter, the obtained sintered body was subjected to a two-step aging treatment consisting of treatments of 800°C ⁇ 1 hour and 550°C ⁇ 2.5 hours.
  • the composition, the amount of oxygen, and the amount of nitrogen of each of the obtained sintered bodies are shown in FIG. 17.
  • magnetic properties thereof are shown in FIG. 18.
  • sample A has a residual magnetic flux density (Br) of 14.0 kG or greater, a coercive force (HcJ) of 13.0 kOe or greater, and a squareness (Hk/HcJ) of 95% or more in the sintering temperature range between 1,030°C and 1,070°C.
  • Br residual magnetic flux density
  • HcJ coercive force
  • Hk/HcJ squareness
  • Samples B and C both of which contain a lower amount of Nd than sample A, have a residual magnetic flux density (Br) of 14.0 kG or greater, a coercive force (HcJ) of 13.5 kOe or greater, and a squareness (Hk/HcJ) of 95% or more in the sintering temperature range between 1,030°C and 1,090°C.
  • Br residual magnetic flux density
  • HcJ coercive force
  • Hk/HcJ squareness
  • the low R alloys were mixed with the high R alloys for 30 minutes in the combinations as shown in FIG. 19. Thereafter, the mixture was subjected to the pulverizing with a jet mill to a mean particle size of 4.0 ⁇ m.
  • the obtained fine powders were compacted in a magnetic field under the same conditions as in Embodiment Example 1. Thereafter, in the case of sample E, the compacted body was sintered at 1,070°C for 4 hours, and in the case of sample F, it was sintered at 1,020°C for 4 hours.
  • the obtained sintered bodies of both samples E and F were subjected to a two-step aging treatment consisting of treatments of 800°C ⁇ 1 hour and 550°C ⁇ 2.5 hours.
  • the composition, the amount of oxygen, and the amount of nitrogen of each of the obtained sintered bodies are shown in FIG. 19.
  • magnetic properties thereof are shown in FIG. 20.
  • the magnetic properties of samples A to D prepared in Embodiment Example 3 are also shown in FIG. 20.
  • a Zr rich product is allowed to exist in an R 2 T 14 B phase that constitutes the main phase of an R-T-B system rare earth permanent magnet, so that the grain growth can be inhibited, while keeping a decrease in magnetic properties to a minimum.
  • a suitable sintering temperature range of 40°C or more can be kept, even using a large sintering furnace that is usually likely to cause unevenness in heating temperature, an R-T-B system rare earth permanent magnet consistently having high magnetic properties can be easily obtained.

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Claims (4)

  1. Seltenerden-Permanentmagnet vom R-T-B-System, umfassend einen Sinterkörper, der aus 28 bis 33 Gew.% R, 0,5 bis 1,5 Gew.% B, 0,03 bis 0,3 Gew.% Al, 0,03 bis 0,3 Gew.% Cu, 0,05 bis 0,2 Gew.% Zr, 0,1 bis 4 Gew.% Co und als Rest im Wesentlichen Fe und unvermeidbaren Verunreinigungen besteht, wobei der Sinterkörper folgendes umfasst:
    eine Hauptphase bestehend aus einer R2T14B-Phase, wobei R für ein oder mehrere Seltenerdelement(e) steht, mit der Bedingung, dass die Seltenerdelemente Y beinhalten, und T für ein oder mehrere Übergangsmetall-Elemente steht, die Fe oder Fe und Co beinhalten; und
    eine Korngrenzenphase, die eine größere Menge an R enthält als die Hauptphase,
    wobei in der genannten R2T14B-Phase ein Zr-reiches Produkt existiert, das eine Länge von einigen hundert nm und eine Breite zwischen einigen nm und 15 nm hat.
  2. Seltenerden-Permanentmagnet vom R-T-B-System gemäß Anspruch 1, wobei das genannte Produkt eine flache oder nadelförmige Form hat.
  3. Seltenerden-Permanentmagnet vom R-T-B-System gemäß Anspruch 1, wobei die Menge an Sauerstoff, die im genannten Sinterkörper enthalten ist, 2000 ppm oder weniger ist.
  4. Seltenerden-Permanentmagnet vom R-T-B-System gemäß Anspruch 3, wobei im genannten Sinterkörper 0,1 bis 0,15 Gew.% Zr enthalten ist.
EP03748612A 2002-09-30 2003-09-30 Seltenerdelement-permanentmagnet auf r-t-b-basis Expired - Lifetime EP1460650B1 (de)

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WO2005105343A1 (ja) * 2004-04-30 2005-11-10 Neomax Co., Ltd. 希土類磁石用原料合金および粉末ならびに焼結磁石の製造方法
JP4618437B2 (ja) * 2006-03-30 2011-01-26 Tdk株式会社 希土類永久磁石の製造方法およびその原料合金
CN101471165B (zh) * 2007-12-26 2012-09-19 北京中科三环高技术股份有限公司 钕铁硼烧结稀土永磁合金及其制备方法
CN101819841A (zh) * 2010-05-17 2010-09-01 上海交通大学 钕铁硼磁性材料及其制备方法
DE112013003109T5 (de) * 2012-06-22 2015-02-26 Tdk Corp. Gesinterter Magnet
JP6314380B2 (ja) * 2013-07-23 2018-04-25 Tdk株式会社 希土類磁石、電動機、及び電動機を備える装置
CN106782971A (zh) * 2016-12-05 2017-05-31 湖南航天磁电有限责任公司 一种钕铁硼材料及其制备方法
JP6849806B2 (ja) * 2016-12-29 2021-03-31 北京中科三環高技術股▲ふん▼有限公司Beijing Zhong Ke San Huan Hi−Tech Co.,Ltd. 微粒子希土類合金鋳片、その製造方法、および回転冷却ロール装置
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DE60311960T2 (de) 2007-10-31
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EP1460650A1 (de) 2004-09-22
DE60317460T2 (de) 2008-09-18
DE60311960D1 (de) 2007-04-05
JPWO2004029999A1 (ja) 2006-01-26
CN1572006A (zh) 2005-01-26
EP1460651A4 (de) 2005-03-23
WO2004030000A1 (ja) 2004-04-08
JPWO2004030000A1 (ja) 2006-01-26
CN100334662C (zh) 2007-08-29
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EP1460650A4 (de) 2005-03-30
EP1460651A1 (de) 2004-09-22

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