EP1214720B1 - METHOD FOR PRODUCING PERMANENT MAGNETS ON THE BASIS OF BORON-LOW Nd-Fe-B ALLOY - Google Patents

METHOD FOR PRODUCING PERMANENT MAGNETS ON THE BASIS OF BORON-LOW Nd-Fe-B ALLOY Download PDF

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EP1214720B1
EP1214720B1 EP00962502A EP00962502A EP1214720B1 EP 1214720 B1 EP1214720 B1 EP 1214720B1 EP 00962502 A EP00962502 A EP 00962502A EP 00962502 A EP00962502 A EP 00962502A EP 1214720 B1 EP1214720 B1 EP 1214720B1
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EP1214720A1 (en
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Matthias Katter
Wilhelm Fernengel
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Vacuumschmelze GmbH and Co KG
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Vacuumschmelze GmbH and Co KG
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—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
    • 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

Definitions

  • the invention relates to processes for the production of permanent magnets from a low-boron Nd-Fe-B alloy.
  • Such alloys and methods of making permanent magnets from this alloy for example, from the EP-A-0 680 054, EP-A-0 753 867, JP 10 289813A, JP 10 181010A and EP 0 124 655.
  • Procedure is first an alloy based on Neodymium, iron and boron melted. The alloy becomes one Discharge melted block, which then crushed into powder becomes. The powder becomes blanks in the magnetic field pressed, which are finally sintered.
  • the coercive force H cJ at 150 ° C is crucial for the quality of the permanent magnet.
  • At high background load even values above 13 kOe at 150 ° C are required.
  • such magnets should also have the highest possible remanence B r .
  • the remanence B r of Nd-Fe-B permanent magnets which have a coercive force H cJ in the range of 4.5 kOe at 150 ° C., should be at least 1.29 T, but more preferably more than 1.35 T, at room temperature ,
  • the reversible temperature coefficient of remanence TK (B r ) in the temperature range of 20 ° C to 150 ° C should be better than -0.11% / K.
  • such permanent magnets should have the best possible corrosion resistance in order to make expensive and expensive coatings superfluous.
  • the invention has for its object to produce an alloy for permanent magnets on the basis of at least one rare earth, at least one transition metal and boron, which has a higher coercive force H cJ than conventional alloys with the same remanence B r and a low temperature coefficient of remanence and corrosion resistant.
  • Nd-Fe-B alloys consist essentially of three phases: the hard magnetic ⁇ -phase with the composition Nd 2 Fe 14 B, the non-magnetic ⁇ -phase with the composition Nd 1,1 Fe 4 B 4 and the non-magnetic gusset phase consists almost entirely of Nd.
  • the Nd-rich gusset phase magnetically separates the grains of the ⁇ phase, resulting in a high coercive force H cJ .
  • the concentrations of B are too low, there is a risk that the soft magnetic Nd 2 Fe 17 phase may be formed instead of the non-magnetic ⁇ phase, thereby considerably reducing the coercive force H cJ .
  • the Nd 2 Fe 17 phase which is detrimental to the coercive force H cJ is not formed in the alloys produced according to the invention when falling below a critical B content in place of the non-magnetic ⁇ phase, but rather initially as a series of non-magnetic Ga-containing phases.
  • these Ga-containing phases contribute to the magnetic decoupling of the grains of the ⁇ phase, which improves the coercive field strength H cJ and also the temperature dependence of the alloy.
  • Figure 1 is a phase diagram showing the composition of a Nd-Fe-B alloy depending on the effective content of boron and rare earths.
  • the structure suitable for use as a permanent magnet occurs, above all, within a phase triangle 1.
  • the alloy consists of ⁇ -phase hard magnetic grains of composition Nd 2 Fe 14 B, as well as non-magnetic ⁇ -phase grains of composition Nd 1 , 1 Fe 4 B 4 and the nonmagnetic gusset phase, which are almost exclusively consists of Nd.
  • the Nd-rich gusset phase magnetically separates the grains of the ⁇ phase, which is necessary to achieve a high coercive force H cJ .
  • [O], [C] and [N] are the weight fractions of O, C and N. In the formulas mentioned, all data are concentration data in% by weight.
  • the effective content of rare earth and boron influences the structure of the structure.
  • the microstructure exists almost exclusively in the form of the ⁇ phase.
  • the alloy is in the ⁇ -phase, while at the point SE it consists essentially of the Nd-rich gusset phase.
  • the proportion of the ⁇ -phase can in principle be arbitrarily small.
  • the boron content is too low, there is a risk that the soft magnetic Nd 2 Fe 17 phase forms instead of the non-magnetic ⁇ phase, which considerably reduces the coercive force H cJ .
  • composition of the Nd-Fe-B permanent magnets is conventionally always chosen to be within the phase triangle 1, in particular above the anode 2.
  • the Werce for the respective points in the phase diagram of Figure 1 are listed in Table 1.
  • the coercive field strength H cJ of the Nd-Fe-B permanent magnets used should be at least 4.5 kOe, more preferably at least 5 kOe, at low counterfield loading. At higher opposing field load even higher values above 13 kOe at 150 ° C are required.
  • Nd-Fe-B permanent magnets should also have the highest possible remanence B r .
  • the reversible temperature coefficient of remanence TK (B r ) in the temperature range of 20 ° C to 150 ° C should be better than -0.11% / K.
  • Nd-Fe-B permanent magnets should be as good as possible Corrosion resistance have to be elaborate and expensive To make coatings unnecessary.
  • phase region 3 in which, in addition to the hard magnetic phase ⁇ and in addition to the non-magnetic Nd-rich phase, further Ga-containing phases are present.
  • a node 4 separates the phase region 3 from another phase region 5 in which the Nd 2 Fe 17 phase predominates.
  • the temperature coefficient of remanence TK (B r ) of Nd-Fe-B permanent magnets can be improved.
  • the temperature coefficient of remanence TK (B r ) is improved by adding 3 wt% Co from -0.12% / K to about -0.105% / K.
  • alloying only Co results in the formation of a soft magnetic SECo 2 Laves phase, which considerably reduces the coercive force H cJ .
  • the formation of this harmful Laves phase can be prevented by simultaneous alloying of Cu.
  • the addition of 0.05 to 0.2 wt.% Cu the addition of Cu-containing Nd-Fe-B permanent magnets can be cooled slowly after a heat treatment performed in the manufacturing process without significantly reducing the coercive force H cJ .
  • Nd-Fe-B permanent magnets to corrosion by water vapor is by additional Zulegieren of Co, Cu and Ga compared to conventional Nd-Fe-B permanent magnets improved by about three orders of magnitude. It will a particularly reactive Nd-rich gusset phase largely replaced by chemically nobler Co, Cu and Ga containing phases.
  • Nd-Fe-B permanent magnets having a mass loss of ⁇ 1 mg / cm 2 referred to the surface of the Nd-Fe-B permanent magnet in the so-called HAST test after ten days.
  • HAST test the Nd-Fe-B permanent magnets are exposed to a pressure of 2.7 bar at a temperature of 130 ° C. and a relative atmospheric humidity of 95%.
  • Alloys A1 to A4 are conventional alloys with the compositions given in Table 2.
  • the alloys B1 to B3 are alloys according to the invention. With reference to Figure 2 it is clear that with increasing content of Dy, although the coercive field strength increases, but the remanence decreases.
  • FIG. 2 shows that the alloys to which Co, Cu and Ga have been alloyed have a higher coercive force H cJ with the same remanence B r compared to conventional alloys.
  • H cJ coercive force
  • Nd-Fe-B alloys containing Dy in the range 3 % By weight have now been systematically investigated. The results These studies are listed in Tables 3 and 4. In the context of these investigations it has been found that the magnetic properties of the Nd-Fe-B permanent magnets much of the temperature control during the heat treatments performed during the manufacturing process depend.
  • Nd-Fe-B alloys are usually produced by that first the alloy with the desired compositions melted down and poured into a melt block.
  • the melted block is then comminuted to powder and optionally to correct the final composition with others Powders mixed.
  • the finished powder is then in a magnetic field aligned and parallel or perpendicular to the magnetic field direction or also by isostatic pressure to green bodies pressed.
  • the green compacts are then, as shown in FIG 3 and 4, subjected to a sintering process 6. at the example of the temperature control shown in Figure 3 After the sintering process 6, a heat treatment 7 is performed.
  • the cooling from the tempering temperature can be slow, as in FIG. 3, or quickly, as in FIG. 4.
  • FIG. 5 shows the dependence of the coercive force H cJ on the effective boron content and the cooling rate ⁇ T / ⁇ t. From Figure 5 shows that a high coercive force H cJ is achieved at a high boron content only in a narrow temperature window between 440 and 500 ° C. By contrast, with low effective boron content, high coercivities H cJ can be achieved in a larger temperature window . Thus, the coercive field strength H cJ increases with decreasing boron content by almost 3 kOe. By a rapid cooling below 750 ° C in the sintering process and by rapid cooling of the tempering temperature, the coercive force H cJ can be increased again by about 1 kOe.
  • Nd-Fe-B permanent magnets it is quite possible to cool Nd-Fe-B permanent magnets slowly after the heat treatment at cooling rates in the range of 1 to 2 K / min without substantial deterioration of the magnetic properties, if only the Nd-Fe-B alloy is boron-poor , A low-boron Nd-Fe-B alloy is to be understood as meaning an alloy whose effective boron content is below the Konode 2.
  • Tables 3 and 4 list compositions and magnetic properties of isostatically pressed Nd-Fe-B permanent magnets with different effective rare earth and boron content. The bold indications refer to the low-boron alloys according to the invention.
  • All Nd-Fe-B permanent magnets are produced by the conventional powder metallurgy process and sintered at about 1060 ° C to a density> 7.6 g / cm 3 .
  • the Nd-Fe-B permanent magnets listed in Table 3 were slowly cooled from sintering temperature to about room temperature at about 1 to 2 K / min. Thereafter, they were tempered at a temperature of 440 ° C to 560 ° C for one to two hours and again slowly cooled at about 1 to 2 K / min to room temperature.
  • the magnets listed in Table 4 were initially quenched from sintering temperature slowly to about 750 ° C at about 2 K / min and rapidly quenched to room temperature after about 1 hour holding at about 30 to 50 K / min. These Nd-Fe-B permanent magnets were after a subsequent annealing at 470 to 530 ° C again rapidly cooled at about 30 to 50 K / min to room temperature.
  • the values for the remanence B r for the alloys from Table 3 are plotted as a function of the effective content of boron and rare earths.
  • Two level lines illustrate the trend of increasing remanence B r with decreasing RDE content and increasing boron content.
  • an effective rare-earth content of ⁇ 30% by weight and an effective boron content of> 0.93% by weight a remanence B r of more than 1.35 T is obtained for isostatically pressed Nd-Fe-B permanent magnets reached.
  • the remanence B r passes just below the boundary line 2 to the phase triangle 1 by a maximum.
  • FIG. 7 shows the dependence of the coercive force at 150 ° C. for the slowly cooled Nd-Fe-B permanent magnets from Table 3. From Figure 7 it can be seen that increases with decreasing effective boron content, the coercive force H cJ at 150 ° C. The same applies to the coercive force at 20 ° C.
  • FIG. 8 shows the dependence of the temperature coefficient of H cJ on slowly cooled Nd-Fe-B permanent magnets as a function of the effective content of rare earths and boron.
  • Nd-Fe-B permanent magnets which were rapidly cooled from about 750 ° C and from annealing temperature. According to FIGS. 9 and 10, however, somewhat better values are achieved both for the temperature dependence and for the absolute values in comparison with the slowly cooled Nd-Fe-B permanent magnets. This extends the range in which the required properties, namely a remanence B r > 1.35 T at room temperature and a coercive force H cJ > 5 kOe at 150 ° C, are achieved.
  • Pr can be used in addition to Nd, without the magnetic properties of the permanent magnets are affected.

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  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
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Description

Die Erfindung betrifft Verfahren zur Herstellung von Dauermagneten aus einer borarmen Nd-Fe-B-Legierung.The invention relates to processes for the production of permanent magnets from a low-boron Nd-Fe-B alloy.

Derartige Legierungen und Verfahren zur Herstellung von Dauermagneten aus dieser Legierung sind beispielsweise aus der EP-A-0 680 054, EP-A-0 753 867, JP 10 289813A, JP 10 181010A und EP 0 124 655 bekannt. In dem aus der EP 0 124 655 bekannten Verfahren wird zunächst eine Legierung auf der Basis von Neodym, Eisen und Bor erschmolzen. Die Legierung wird zu einem Schmelzblock abgegossen, der anschließend zu Pulver zerkleinert wird. Aus dem Pulver werden im Magnetfeld Rohlinge gepreßt, die schließlich gesintert werden.Such alloys and methods of making permanent magnets from this alloy, for example, from the EP-A-0 680 054, EP-A-0 753 867, JP 10 289813A, JP 10 181010A and EP 0 124 655. In the known from EP 0 124 655 Procedure is first an alloy based on Neodymium, iron and boron melted. The alloy becomes one Discharge melted block, which then crushed into powder becomes. The powder becomes blanks in the magnetic field pressed, which are finally sintered.

Für viele Anwendungen von Nd-Fe-B-Dauermagneten, insbesondere in Motoren und Antrieben aller Art, ist die Koerzitivfeldstärke HcJ bei 150°C entscheidend für die Qualität des Dauermagneten. Bei geringer Gegenfeldbelastung muß die Koerzitivfeldstärke HcJ bei 150°C mindestens 4,5 kOe (1 kOe = 79,5775 kA/m), besser mehr als 5 kOe betragen. Bei hoher Gegenfeldbelastung sind sogar Werte oberhalb von 13 kOe bei 150°C gefordert. Neben der hohen Koerzitivfeldstärke HcJ sollen solche Magnete auch eine möglichst hohe Remanenz Br aufweisen. Beispielsweise soll die Remanenz Br von Nd-Fe-B-Dauermagneten, die bei 150°C eine Koerzitivfeldstärke HcJ im Bereich von 4,5 kOe aufweisen, bei Raumtemperatur mindestens 1,29 T, besser jedoch mehr als 1,35 T betragen.For many applications of Nd-Fe-B permanent magnets, especially in motors and drives of all kinds, the coercive force H cJ at 150 ° C is crucial for the quality of the permanent magnet. At low opposing field loading , the coercive force H cJ at 150 ° C must be at least 4.5 kOe (1 kOe = 79.5775 kA / m), better more than 5 kOe. At high background load even values above 13 kOe at 150 ° C are required. In addition to the high coercive force H cJ such magnets should also have the highest possible remanence B r . For example, the remanence B r of Nd-Fe-B permanent magnets, which have a coercive force H cJ in the range of 4.5 kOe at 150 ° C., should be at least 1.29 T, but more preferably more than 1.35 T, at room temperature ,

Für Motoranwendungen ist außerdem gefordert, daß der reversible Temperaturkoeffizient der Remanenz TK (Br) im Temperaturbereich von 20°C bis 150°C besser als -0,11 %/K sein soll. Zusätzlich sollen derartige Dauermagnete eine möglichst gute Korrosionsbeständigkeit aufweisen, um aufwendige und teuere Beschichtungen überflüssig zu machen. So wird zum Beispiel gefordert, daß der Masseverlust von unbeschichteten Magneten im sogenannten HAST-Test nach zehn Tagen kleiner als 1 mg/cm2 sein soll. Im HAST-Test werden die Dauermagnete bei einer Temperatur von 130°C und einer relativen Luftfeuchtigkeit von 95% einem Druck von 2,7 bar (1 bar = 105 Pa) ausgesetzt.For motor applications is also required that the reversible temperature coefficient of remanence TK (B r ) in the temperature range of 20 ° C to 150 ° C should be better than -0.11% / K. In addition, such permanent magnets should have the best possible corrosion resistance in order to make expensive and expensive coatings superfluous. For example, it is required that the mass loss of uncoated magnets in the so-called HAST test should be less than 1 mg / cm 2 after ten days. In the HAST test, the permanent magnets are exposed to a pressure of 2.7 bar (1 bar = 10 5 Pa) at a temperature of 130 ° C and a relative humidity of 95%.

Diese Anforderungen werden von herkömmlichen Nd-Fe-B-Dauermagneten nicht erfüllt.These requirements are met by conventional Nd-Fe-B permanent magnets not fulfilled.

Ausgehend von diesem Stand der Technik liegt der Erfindung die Aufgabe zugrunde, eine Legierung für Dauermagnete auf der Basis wenigstens einer Seltenen Erde, wenigstens eines Übergangsmetalls und Bor herzustellen, die bei gleicher Remanenz Br eine höhere Koerzitivfeldstärke HcJ als herkömmliche Legierungen aufweist sowie über einen niedrigen Temperaturkoefizient der Remanenz verfügt und korrosionsbeständig ist.Starting from this prior art, the invention has for its object to produce an alloy for permanent magnets on the basis of at least one rare earth, at least one transition metal and boron, which has a higher coercive force H cJ than conventional alloys with the same remanence B r and a low temperature coefficient of remanence and corrosion resistant.

Diese Aufgabe wird erfindungsgemäß durch ein Verfahren gemäß Anspruch 1 gelöst. Ausgestaltungen und Weiterbildungen des Erfindungsgedankens sind Gegenstand von Unteransprüchen.This object is achieved by a method according to Claim 1 solved. Embodiments and developments of Concept of the invention are the subject of subclaims.

Herkömmliche Nd-Fe-B-Legierungen bestehen im wesentlichen aus drei Phasen: der hartmagnetischen ϕ-Phase mit der Zusammensetzung Nd2Fe14B, der unmagnetischen η-Phase mit der Zusammensetzung Nd1,1Fe4B4 und der unmagnetischen Zwickelphase die nahezu ausschließlich aus Nd besteht. Die Nd-reiche Zwickelphase trennt die Körner der ϕ-Phase magnetisch voneinander, was eine hohe Koerzitivfeldstärke HcJ zur Folge hat. Bei zu geringen Konzentrationen an B besteht jedoch die Gefahr, daß sich an Stelle der unmagnetischen η-Phase die weichmagnetische Nd2Fe17-Phase bildet, wodurch sich die Koerzitivfeldstärke HcJ erheblich reduziert. Anders als bei herkömmlichen Nd-Fe-B-Legierungen entsteht bei den erfindungsgemäß hergestellten Legierungen beim Unterschreiten eines kritischen B-Gehalts an Stelle der unmagnetischen η-Phase nicht die für die Koerzitivfeldstärke HcJ schädliche Nd2Fe17-Phase, sondern zunächst eine Reihe von unmagnetischen Ga-haltigen Phasen. Diese Ga-haltigen Phasen tragen im Gegensatz zur ferromagnetischen Nd2Fe17-Phase zur magnetischen Entkopplung der Körner der ϕ-Phase bei, wodurch sich die Koerzitivfeldstärke HcJ und auch die Temperaturabhängigkeit der Legierung verbessert.Conventional Nd-Fe-B alloys consist essentially of three phases: the hard magnetic φ-phase with the composition Nd 2 Fe 14 B, the non-magnetic η-phase with the composition Nd 1,1 Fe 4 B 4 and the non-magnetic gusset phase consists almost entirely of Nd. The Nd-rich gusset phase magnetically separates the grains of the φ phase, resulting in a high coercive force H cJ . However, if the concentrations of B are too low, there is a risk that the soft magnetic Nd 2 Fe 17 phase may be formed instead of the non-magnetic η phase, thereby considerably reducing the coercive force H cJ . In contrast to conventional Nd-Fe-B alloys, the Nd 2 Fe 17 phase which is detrimental to the coercive force H cJ is not formed in the alloys produced according to the invention when falling below a critical B content in place of the non-magnetic η phase, but rather initially as a series of non-magnetic Ga-containing phases. In contrast to the ferromagnetic Nd 2 Fe 17 phase, these Ga-containing phases contribute to the magnetic decoupling of the grains of the φ phase, which improves the coercive field strength H cJ and also the temperature dependence of the alloy.

Bei geschickter Temperaturführung können besonders hohe Werte für die Koerzitivfeldstärke HcJ erzielt werden. Hervorzuheben ist dabei, daß insbesondere bei schneller Abkühlung besonders gute Werte für die Koerzitivfeldstärke HcJ erreicht werden. Eine schnelle Abkühlung ist jedoch gleichbedeutend mit einer effektiven Nutzung der Öfen. Dagegen können bei langsamer Kühlung auch große Dauermagnetteile hergestellt werden, ohne daß sich in den Dauermagnetteilen Abkühlrisse bilden und sich die Koerzitivfeldstärke HcJ wesentlich verringert.With skillful temperature control particularly high values for the coercive force H cJ can be achieved. It should be emphasized that particularly good values for the coercive field strength H cJ are achieved, especially with rapid cooling. However, rapid cooling is synonymous with effective use of the ovens. On the other hand, with slow cooling, large permanent magnet parts can be produced without forming cooling cracks in the permanent magnet parts and substantially reducing the coercive force H cJ .

Nachfolgend wird die Erfindung näher anhand der beigefügten Zeichnung erläutert. Es zeigen:

Figur 1
einen Ausschnitt aus einem Phasendiagramm für Nd-Fe-B-Dauermagnete;
Figur 2
eine Darstellung des Zusammenhangs zwischen Remanenz Br und Koerzitivfeldstärke HcJ für verschiedene Nd-Fe-B-Dauermagnete;
Figur 3
ein Diagramm mit der Temperaturführung beim Sintern und Anlassen;
Figur 4
ein weiteres Diagramm mit einer weiteren möglichen Temperaturführung beim Sintern und Anlassen;
Figur 5
eine Darstellung, aus der die Abhängigkeit der Koerzitivfeldstärke HcJ von der Art der Temperaturführung beim Sintern und Anlassen ersichtlich ist;
Figur 6
ein Diagramm, aus dem die Abhängigkeit der Remanenz Br vom effektiven Gehalt an Bor und Seltenen Erden hervorgeht;
Figur 7
eine Darstellung, die die Abhängigkeit der Koerzitivfeldstärke HcJ bei 150°C vom effektiven Gehalt an Bor und Seltenen Erden bei langsamem Abkühlen zeigt;
Figur 8
eine Darstellung, die die Abhängigkeit des Temperaturkoeffizienten der Koerzitivfeldstärke TK(HcJ) vom effektiven Gehalt an Bor und Seltenen Erden bei langsamem Abkühlen darstellt;
Figur 9
eine Darstellung, die die Abhängigkeit der Koerzitivfeldstärke HcJ bei 150°C vom effektiven Gehalt an Bor und Seltenen Erden beim schnellen Abkühlen zeigt; und
Figur 10
eine Darstellung, die die Abhängigkeit des Temperaturkoeffizienten TK(HcJ) der Koerzitivfeldstärke HcJ vom effektiven Gehalt an Bor und Seltenen Erden bei schneller Kühlung darstellt.
The invention will be explained in more detail with reference to the accompanying drawings. Show it:
FIG. 1
a section of a phase diagram for Nd-Fe-B permanent magnets;
FIG. 2
a representation of the relationship between remanence B r and coercive force H cJ for various Nd-Fe-B permanent magnets;
FIG. 3
a diagram with the temperature control during sintering and tempering;
FIG. 4
another diagram with another possible temperature control during sintering and tempering;
FIG. 5
a representation showing the dependence of the coercive force H cJ on the type of temperature control during sintering and tempering;
FIG. 6
a diagram showing the dependence of the remanence B r on the effective content of boron and rare earths;
FIG. 7
a representation showing the dependence of the coercive force H cJ at 150 ° C on the effective content of boron and rare earth with slow cooling;
FIG. 8
a representation showing the dependence of the coercive force coefficient TK (H cJ ) on the effective content of boron and rare earth on slow cooling;
FIG. 9
a plot showing the dependence of the coercive force H cJ at 150 ° C on the effective content of boron and rare earth during rapid cooling; and
FIG. 10
a representation showing the dependence of the temperature coefficient TK (H cJ ) of coercive force H cJ on the effective content of boron and rare earth with rapid cooling.

Figur 1 ist ein Phasendiagramm, das die Zusammensetzung einer Nd-Fe-B-Legierung in Abhängigkeit vom effektiven Gehalt an Bor und Seltenen Erden zeigt. Das für die Anwendung als Dauermagnet geeignete Gefüge tritt vor allem innerhalb eines Phasendreiecks 1 auf. Innerhalb dieses Phasendreiecks 1 besteht die Legierung aus hartmagnetischen Körnern der ϕ-Phase mit der Zusammensetzung Nd2Fe14B, sowie aus Körnern der unmagnetischen η-Phase mit der Zusammensetzung Nd1, 1Fe4B4 und der unmagnetischen Zwickelphase, die nahezu ausschließlich aus Nd besteht. Die Nd-reiche Zwickelphase trennt die Körner der ϕ-Phase magnetisch voreinander, was notwendig ist, um eine hohe Koerzitivfeldstärke HcJ zu erzielen.Figure 1 is a phase diagram showing the composition of a Nd-Fe-B alloy depending on the effective content of boron and rare earths. The structure suitable for use as a permanent magnet occurs, above all, within a phase triangle 1. Within this phase triangle 1, the alloy consists of φ-phase hard magnetic grains of composition Nd 2 Fe 14 B, as well as non-magnetic η-phase grains of composition Nd 1 , 1 Fe 4 B 4 and the nonmagnetic gusset phase, which are almost exclusively consists of Nd. The Nd-rich gusset phase magnetically separates the grains of the φ phase, which is necessary to achieve a high coercive force H cJ .

Um beurteilen zu können, ob eine bestimmte Zusammensetzung der Legierung innerhalb oder außerhalb des Phasendreiecks 1 liegt, ist es zunächst notwendig, den Gehalt an Seltenen Erden und Bor bezüglich der Verunreinigungen zu korrigieren, da ein Teil des Nd in der Form von Nd-Oxiden, Nd-Nickelkarbiden und Nd-Nitriden gebunden ist. Der effektive Gehalt an Seltenen Erden [SE]eff und der effektive Gehalt an Bor [B]eff ergibt sich aus folgenden Formeln: [SE]eff = ([SE] - [ΔSE])f, [B]eff = [B]f, wobei [SE] und [B] jeweils die Gewichtsanteile an Seltenen Erden und Bor sind. [ΔSE] ist der Anteil an Seltenen Erden, der in den Verbindungen Nd2O3, Nd2CO und NdN gebunden ist. f ist ein Normierungsfaktor: [Δ SE] = 5,993 [O] + 16,05[C] + 10,30[N] f = 100 / ([100 - [Δ SE] - [O] - [C] - [N]). In order to be able to judge whether a particular composition of the alloy lies within or outside the phase triangle 1, it is first necessary to correct the rare earth and boron content with respect to the impurities, since part of the Nd in the form of Nd oxides, Nd nickel carbides and Nd nitrides is bound. The effective content of rare earths [SE] eff and the effective content of boron [B] eff are given by the following formulas: [SE] eff = ([SE] - [ΔSE]) f, [B] eff = [B] f, where [SE] and [B] are the weights of rare earths and boron, respectively. [ΔSE] is the proportion of rare earths bound in the compounds Nd 2 O 3 , Nd 2 CO and NdN. f is a normalization factor: [ΔSE] = 5.993 [O] + 16.05 [C] + 10.30 [N] f = 100 / ([100 - [ΔSE] - [O] - [C] - [N]).

[O], [C] und [N] sind dabei die Gewichtsanteile von O, C und N. In den genannten Formeln sind alle Angaben Konzentrationsangaben in Gew.%.[O], [C] and [N] are the weight fractions of O, C and N. In the formulas mentioned, all data are concentration data in% by weight.

Der effektive Gehalt an Seltenen Erden und Bor beeinflußt den Aufbau des Gefüges. Im Punkt η des Phasendreiecks 1 liegt das Gefüge nahezu ausschließlich in Form der η-Phase vor. Im Punkt ϕ des Phasendreicks 1 ist die Legierung in der ϕ-Phase, während sie im Punkt SE im wesentlichen aus der Nd-reichen Zwickelphase besteht. Der Anteil an der η-Phase kann im Prinzip beliebig klein sein. Bei einem zu geringen Bor-Gehalt besteht jedoch die Gefahr, daß sich an Stelle der unmagnetischen η-Phase die weichmagnetische Nd2Fe17-Phase bildet, wodurch sich die Koerzitivfeldstärke HcJ erheblich reduziert. Die Zusammensetzung der Nd-Fe-B-Dauermagnete wird demzufolge herkömmlicherweise immer so gewählt, daß sie innerhalb des Phasendreiecks 1, insbesondere oberhalb der Konode 2 liegt. Die Werce für die jeweiligen Punkte im Phasendiagramm aus Figur 1 sind in Tabelle 1 eingetragen. SE in Gew.% B-Gehalt in Gew.% Fe-Gehalt in Gew.% ϕ 26,68 1,000 Rest η 37,3 10,2 Rest Nd-reich 98 0 Rest Nd2Fe17 23,3 0 Rest The effective content of rare earth and boron influences the structure of the structure. At the point η of the phase triangle 1, the microstructure exists almost exclusively in the form of the η phase. At the point φ of the phase jog 1, the alloy is in the φ-phase, while at the point SE it consists essentially of the Nd-rich gusset phase. The proportion of the η-phase can in principle be arbitrarily small. However, if the boron content is too low, there is a risk that the soft magnetic Nd 2 Fe 17 phase forms instead of the non-magnetic η phase, which considerably reduces the coercive force H cJ . Accordingly, the composition of the Nd-Fe-B permanent magnets is conventionally always chosen to be within the phase triangle 1, in particular above the anode 2. The Werce for the respective points in the phase diagram of Figure 1 are listed in Table 1. SE in% by weight B content in% by weight Fe content in% by weight φ 26.68 1,000 rest η 37.3 10.2 rest Nd-rich 98 0 rest Nd2Fe17 23.3 0 rest

Für viele Anwendungen von Nd-Fe-B-Dauermagneten, insbesondere in Motoren und Antrieben aller Art, ist nun aber die Koerzitivfeldstärke HcJ bei 150°C wesentlich. Die Koerzitivfeldstärke HcJ der verwendeten Nd-Fe-B-Dauermagnete soll bei geringer Gegenfeldbelastung wenigstens 4,5 kOe, besser wenigstens 5 kOe betragen. Bei höherer Gegenfeldbelastung sind noch höhere Werte oberhalb von 13 kOe bei 150°C gefordert. Neben einer hohen Koerzitivfeldstärke HcJ bei einer Temperatur von 150°C sollen derartige Nd-Fe-B-Dauermagnete auch eine möglichst hohe Remanenz Br haben.For many applications of Nd-Fe-B permanent magnets, especially in motors and drives of all kinds, but now the coercive force H cJ at 150 ° C is essential. The coercive field strength H cJ of the Nd-Fe-B permanent magnets used should be at least 4.5 kOe, more preferably at least 5 kOe, at low counterfield loading. At higher opposing field load even higher values above 13 kOe at 150 ° C are required. In addition to a high coercive force H cJ at a temperature of 150 ° C such Nd-Fe-B permanent magnets should also have the highest possible remanence B r .

Insbesondere für die Anwendung in Motoren wird verlangt, daß der reversible Temperaturkoeffizient der Remanenz TK (Br) im Temperaturbereich von 20°C bis 150°C besser als -0,11 %/K sein soll.In particular, for use in motors, it is required that the reversible temperature coefficient of remanence TK (B r ) in the temperature range of 20 ° C to 150 ° C should be better than -0.11% / K.

Zusätzlich sollen die Nd-Fe-B-Dauermagnete eine möglichst gute Korrosionsbeständigkeit haben, um aufwendige und teuere Beschichtungen überflüssig zu machen. In addition, the Nd-Fe-B permanent magnets should be as good as possible Corrosion resistance have to be elaborate and expensive To make coatings unnecessary.

Es wurde herausgefunden, daß sich durch den Zusatz von Gallium zur Legierung unterhalb der Konode 2 ein Phasengebiet 3 ausbildet, in dem neben der hartmagnetischen ϕ-Phase und neben der unmagnetischen Nd-reichen Phase weitere Ga-haltige Phasen vorliegen. Eine Konode 4 trennt das Phasengebiet 3 von einem weiteren Phasengebiet 5, in dem die Nd2Fe17-Phase überwiegt. Überraschenderweise ist es nun möglich, mit den Legierungen im Phasengebiet 3 die an Nd-Fe-B-Dauermagnete beim Einsatz in Motoren gestellten Anforderungen zu erfüllen. Diese Verbesserung läßt sich durch folgendes metallurgisches Modell erklären: bei herkömmlichen Nd-Fe-B-Dauermagneten entsteht die weichmagnetische, für die Koerzitivfeldstärke HcJ schädliche Nd2Fe17-Phase, wenn der durch die Grenzlinie 2 veranschaulichte kritische Bor-Gehalt unterschritten wird. Beim Zusatz von Gallium, Kobalt und Kupfer zur Nd-Fe-B-Legierung entsteht beim Unterschreiten der Grenzlinie 2 anstelle der unmagnetischen η-Phase nicht die Nd2Fe17-Phase, sondern zunächst eine Reihe von unmagnetischen Ga-haltigen Phasen. Diese Ga-haltigen Phasen tragen im Gegensatz zum Nd2Fe17-Phase zur magnetischen Entkopplung der Körner aus der ϕ-Phase bei. Dadurch verbessert sich die Koerzitivfeldstärke HcJ und auch deren Temperaturkoeffizient. Eine weitere Reduktion des Bor-Gehalts führt schließlich dann doch zur Bildung der Nd2Fe17-Phase im Phasengebiet 5 und damit zum Zusammenbruch der Koerzitivfeldstärke HcJ.It has been found that the addition of gallium to the alloy below the anode 2 forms a phase region 3 in which, in addition to the hard magnetic phase φ and in addition to the non-magnetic Nd-rich phase, further Ga-containing phases are present. A node 4 separates the phase region 3 from another phase region 5 in which the Nd 2 Fe 17 phase predominates. Surprisingly, it is now possible with the alloys in phase region 3 to meet the requirements imposed on Nd-Fe-B permanent magnets when used in motors. This improvement can be explained by the following metallurgical model: in conventional Nd-Fe-B permanent magnets, the soft-magnetic Nd 2 Fe 17 phase, which is detrimental to the coercive force H cJ , is created when the critical boron content represented by the boundary line 2 is undershot. When gallium, cobalt and copper are added to the Nd-Fe-B alloy, falling below the boundary line 2 instead of the non-magnetic η phase does not produce the Nd 2 Fe 17 phase, but rather a series of non-magnetic Ga-containing phases. These Ga-containing phases, in contrast to the Nd 2 Fe 17 phase, contribute to the magnetic decoupling of the grains from the φ phase. This improves the coercive force H cJ and also its temperature coefficient. Finally, a further reduction of the boron content leads to the formation of the Nd 2 Fe 17 phase in the phase region 5 and thus to the collapse of the coercive field strength H cJ .

Neben Gallium können auch Co und Cu der Legierung mit vorteilhafter Wirkung hinzugesetzt werden.In addition to gallium and Co and Cu of the alloy with advantageous Effect be added.

Durch Zulegieren von Co läßt sich beispielsweise der Temperaturkoeffizient der Remanenz TK (Br) von Nd-Fe-B-Dauermagneten verbessern. Insbesondere wird der Temperaturkoeffizient der Remanenz TK (Br) durch Zulegieren von 3 Gew.% Co von -0,12%/K auf etwa -0,105 %/K verbessert. Wenn jedoch nur Co zulegiert wird, führt dies zur Bildung einer weichmagnetischen SECo2-Laves-Phase, wodurch die Koerzitivfeldstärke HcJ beträchtlich reduziert wird. Die Bildung dieser schädlichen Laves-Phase läßt sich durch gleichzeitiges Zulegieren von Cu verhindern. Als günstig erwiesen hat sich der Zusatz von 0,05 bis 0,2 Gew.% Cu. Außerdem können Cu-haltige Nd-Fe-B-Dauermagnete nach einer im Herstellungsprozeß durchgeführten Wärmebehandlung langsam gekühlt werden, ohne daß die Koerzitivfeldstärke HcJ wesentlich reduziert wird.By alloying Co, for example, the temperature coefficient of remanence TK (B r ) of Nd-Fe-B permanent magnets can be improved. In particular, the temperature coefficient of remanence TK (B r ) is improved by adding 3 wt% Co from -0.12% / K to about -0.105% / K. However, alloying only Co results in the formation of a soft magnetic SECo 2 Laves phase, which considerably reduces the coercive force H cJ . The formation of this harmful Laves phase can be prevented by simultaneous alloying of Cu. Proven to be beneficial, the addition of 0.05 to 0.2 wt.% Cu. In addition, Cu-containing Nd-Fe-B permanent magnets can be cooled slowly after a heat treatment performed in the manufacturing process without significantly reducing the coercive force H cJ .

Die Beständigkeit der Nd-Fe-B-Dauermagnete gegen die Korrosion durch Wasserdampf wird durch zusätzliches Zulegieren von Co, Cu und Ga im Vergleich zu herkömmlichen Nd-Fe-B-Dauermagnete um etwa drei Größenordnungen verbessert. Dabei wird eine besonders reaktive Nd-reiche Zwickelphase weitgehend durch chemisch edlere Co-, Cu- und Ga-haltige Phasen ersetzt.The resistance of Nd-Fe-B permanent magnets to corrosion by water vapor is by additional Zulegieren of Co, Cu and Ga compared to conventional Nd-Fe-B permanent magnets improved by about three orders of magnitude. It will a particularly reactive Nd-rich gusset phase largely replaced by chemically nobler Co, Cu and Ga containing phases.

Durch diese Maßnahmen ergeben sich Nd-Fe-B-Dauermagnete, die im sogenannten HAST-Test nach zehn Tagen einen auf die Oberfläche des Nd-Fe-B-Dauermagneten bezogenen Masseverlust von < 1 mg/cm2 aufweisen. Im sogenannten HAST-Test werden die Nd-Fe-B-Dauermagnete bei einer Temperatur von 130°C und einer relativen Luftfeuchtigkeit von 95 % einem Druck von 2,7 bar ausgesetzt.These measures result in Nd-Fe-B permanent magnets having a mass loss of <1 mg / cm 2 referred to the surface of the Nd-Fe-B permanent magnet in the so-called HAST test after ten days. In the so-called HAST test, the Nd-Fe-B permanent magnets are exposed to a pressure of 2.7 bar at a temperature of 130 ° C. and a relative atmospheric humidity of 95%.

Außerdem ist es möglich, die Koerzitivfeldstärke HcJ zu erhöhen, indem ein Teil des Nd durch Dy, Tb oder Ho ersetzt wird, ohne daß das Verhältnis von Gehalt an Seltenen Erden zum Gehalt an Fe und B wesentlich verändert wird. Da sich das magnetische Moment von Dy, Tb und Ho im Gegensatz zu Nd antiparallel zum magnetischen Moment von Fe ausrichtet, führt dies zwangsläufig zu einer Reduktion der erreichbaren Remanenz Br. Dies bedeutet, daß die Zunahme der Koerzitivfeldstärke HcJ mit einer Abnahme der Remanenz Br verbunden ist.In addition, it is possible to increase the coercive force H cJ by replacing a part of the Nd with Dy, Tb or Ho without substantially changing the ratio of the rare earth content to the Fe and B content. Since the magnetic moment of Dy, Tb and Ho, in contrast to Nd, is oriented antiparallel to the magnetic moment of Fe, this inevitably leads to a reduction of the achievable remanence B r . This means that the increase in coercive force H cJ is associated with a decrease in remanence B r .

Dieser Zusammenhang ist in Figur 2 und der zugehörigen Tabelle 2 dargestellt. Legierung SE, effektiv B, effektiv Dy Co Cu Ga HcJ (20°C, kOe) HcJ (150°C. kOe) Br(20°C,T) A 1 29,2 0,98 3 - - - 17 3,5 1,33 A 2 29,5 0,98 4,6 - - - 21 5 1,28 A 3 29,6 0,98 6,5 - - - 26 8 1,22 A 4 29,7 0,98 8,6 - - - 31 11 1,16 B 1 29,3 0,94 3 3 0.15 0,23 18 5,3 1,35 B 2 29,5 0,94 5,5 3 0,15 0,23 23 8 1,28 B 3 30 0,93 9,5 3 0,15 0,23 31 13 1,18 This relationship is shown in Figure 2 and the accompanying Table 2. alloy SE, effective B, effective Dy Co Cu ga H cJ (20 ° C, kOe) H cJ (150 ° C, kOe) B r (20 ° C, T) A 1 29.2 0.98 3 - - - 17 3.5 1.33 A 2 29.5 0.98 4.6 - - - 21 5 1.28 A 3 29.6 0.98 6.5 - - - 26 8th 1.22 A 4 29.7 0.98 8.6 - - - 31 11 1.16 B 1 29.3 0.94 3 3 00:15 0.23 18 5.3 1.35 B 2 29.5 0.94 5.5 3 0.15 0.23 23 8th 1.28 B 3 30 0.93 9.5 3 0.15 0.23 31 13 1.18

Die Legierungen A1 bis A4 stellen herkömmliche Legierungen mit den in der Tabelle 2 angegebenen Zusammensetzungen dar. Bei den Legierungen B1 bis B3 handelt es sich um Legierungen gemäß der Erfindung. Anhand von Figur 2 wird deutlich, daß mit zunehmendem Gehalt an Dy zwar die Koerzitivfeldstärke zunimmt, aber die Remanenz abnimmt.Alloys A1 to A4 are conventional alloys with the compositions given in Table 2. The alloys B1 to B3 are alloys according to the invention. With reference to Figure 2 it is clear that with increasing content of Dy, although the coercive field strength increases, but the remanence decreases.

Außerdem läßt Figur 2 erkennen, daß die Legierungen, denen Co, Cu und Ga zulegiert worden ist, bei gleicher Remanenz Br im Vergleich zu herkömmlichen Legierungen eine höhere Koerzitivfeldstärke HcJ aufweisen. Letzeres gilt nicht nur für Raumtemperatur, sondern insbesondere auch bei 150°C.In addition, FIG. 2 shows that the alloys to which Co, Cu and Ga have been alloyed have a higher coercive force H cJ with the same remanence B r compared to conventional alloys. The latter applies not only to room temperature, but in particular also at 150 ° C.

Nd-Fe-B-Legierungen mit einem Gehalt von Dy im Bereich 3 Gew.% sind nun systematisch untersucht worden. Die Ergebnisse dieser Untersuchungen sind in den Tabellen 3 und 4 aufgeführt. Im Rahmen dieser Untersuchungen hat sich herausgestellt, daß die magnetischen Eigenschaften der Nd-Fe-B-Dauermagnete wesentlich von der Temperaturführung während der im Rahmen des Herstellprozesses durchgeführten Wärmebehandlungen abhängen.Nd-Fe-B alloys containing Dy in the range 3 % By weight have now been systematically investigated. The results These studies are listed in Tables 3 and 4. In the context of these investigations it has been found that the magnetic properties of the Nd-Fe-B permanent magnets much of the temperature control during the heat treatments performed during the manufacturing process depend.

Nd-Fe-B-Legierungen werden üblicherweise dadurch hergestellt, daß zunächst die Legierung mit den gewünschten Zusammensetzungen erschmolzen und zu einem Schmelzblock abgegossen wird. Nd-Fe-B alloys are usually produced by that first the alloy with the desired compositions melted down and poured into a melt block.

Der Schmelzblock wird dann zu Pulver zerkleinert und gegebenenfalls zur Korrektur der Endzusammensetzung mit anderen Pulvern gemischt. Das fertige Pulver wird dann in einem Magnetfeld ausgerichtet und parallel oder senkrecht zur Magnetfeldrichtung oder auch durch isostatischen Druck zu Grünlingen verpreßt. Die Grünlinge werden anschließend, wie in Figur 3 und 4 dargestellt, einem Sintervorgang 6 unterzogen. Bei dem in Figur 3 dargestellten Beispiel der Temperaturführung wird nach dem Sintervorgang 6 eine Wärmebehandlung 7 durchgeführt. Die Abkühlung von der Anlaßtemperatur kann langsam, wie in Figur 3, oder schnell, wie in Figur 4, erfolgen.The melted block is then comminuted to powder and optionally to correct the final composition with others Powders mixed. The finished powder is then in a magnetic field aligned and parallel or perpendicular to the magnetic field direction or also by isostatic pressure to green bodies pressed. The green compacts are then, as shown in FIG 3 and 4, subjected to a sintering process 6. at the example of the temperature control shown in Figure 3 After the sintering process 6, a heat treatment 7 is performed. The cooling from the tempering temperature can be slow, as in FIG. 3, or quickly, as in FIG. 4.

In Figur 5 ist die Abhängigkeit der Koerzitivfeldstärke HcJ in Abhängigkeit vom effektiven Bor-Gehalt und der Abkühlgeschwindigkeit ΔT/Δt dargestellt. Aus Figur 5 geht hervor, daß eine hohe Koerzitivfeldstärke HcJ bei einem hohen Bor-Gehalt nur in einem engen Temperaturfenster zwischen 440 und 500°C erreicht wird. Bei niedrigem effektivem Bor-Gehalt dagegen können hohe Koerzitivfeldstärken HcJ in einem größeren Temperaturfenster erzielt werden. So nimmt die Koerzitivfeldstärke HcJ mit abnehmendem Bor-Gehalt um nahezu 3 kOe zu. Durch eine schnelle Abkühlung unterhalb von 750°C im Rahmen des Sintervorgangs und durch schnelles Abkühlen von der Anlaßtemperatur läßt sich die Koerzitivfeldstärke HcJ noch einmal um etwa 1 kOe erhöhen.FIG. 5 shows the dependence of the coercive force H cJ on the effective boron content and the cooling rate ΔT / Δt. From Figure 5 shows that a high coercive force H cJ is achieved at a high boron content only in a narrow temperature window between 440 and 500 ° C. By contrast, with low effective boron content, high coercivities H cJ can be achieved in a larger temperature window . Thus, the coercive field strength H cJ increases with decreasing boron content by almost 3 kOe. By a rapid cooling below 750 ° C in the sintering process and by rapid cooling of the tempering temperature, the coercive force H cJ can be increased again by about 1 kOe.

Von besonderem Interesse sind die hohen Koerzitivfeldstärken HcJ, die sich trotz langsamer Kühlung bei einem niedrigen effektiven Gehalt an Bor von 0,92 Gew.% ergeben. Dies ist insbesondere dann von Vorteil, wenn Nd-Fe-B-Dauermagnete mit großen Querschnittsflächen hergestellt werden sollen. Denn für derartige Teile sind während der Sinterung und der Wärmebehandlung nur geringe Abkühlgeschwindigkeiten ΔT/Δt < 10 K/min zuläßig, um Abkühlrisse zu vermeiden. Diese geringen Abkühlgeschwindigkeiten dürfen jedoch nur zu einer geringfügigen Verschlechterung der magnetischen Eigenschaften führen. Gemäß Figur 5 ist es durchaus möglich, Nd-Fe-B-Dauermagnete nach der Wärmebehandlung langsam mit Abkühlgeschwindigkeiten im Bereich von 1 bis 2 K/min ohne wesentliche Beeinträchtigung der magnetischen Eigenschaften abzukühlen, sofern nur die Nd-Fe-B-Legierung borarm ist. Unter einer borarmen Nd-Fe-B-Legierung ist dabei eine Legierung zu verstehen, deren effektiver Bor-Gehalt unterhalb der Konode 2 liegt.Of particular interest are the high coercive forces H cJ , which, despite slow cooling, result in a low effective boron content of 0.92% by weight. This is particularly advantageous when Nd-Fe-B permanent magnets are to be produced with large cross-sectional areas. Because only small cooling rates .DELTA.T / .DELTA.t <10 K / min are permissible for such parts during sintering and heat treatment in order to avoid cooling cracks. However, these low cooling rates may only lead to a slight deterioration of the magnetic properties. According to Figure 5, it is quite possible to cool Nd-Fe-B permanent magnets slowly after the heat treatment at cooling rates in the range of 1 to 2 K / min without substantial deterioration of the magnetic properties, if only the Nd-Fe-B alloy is boron-poor , A low-boron Nd-Fe-B alloy is to be understood as meaning an alloy whose effective boron content is below the Konode 2.

In den Tabellen 3 und 4 sind Zusammensetzungen und magnetischen Eigenschaften von isostatisch gepreßten Nd-Fe-B-Dauermagneten mit unterschiedlichem effektivem Gehalt an Seltenen Erden und Bor aufgelistet. Die fett gedruckten Angaben beziehen sich auf die borarmen Legierungen gemäß der Erfindung. Alle Nd-Fe-B-Dauermagnete sind nach dem gängigen pulvermetallurgischen Verfahren hergestellt und bei etwa 1060°C auf eine Dichte > 7,6 g/cm3 gesintert worden. Die in Tabelle 3 aufgeführten Nd-Fe-B-Dauermagnete sind von Sintertemperatur langsam mit etwa 1 bis 2 K/min auf Raumtemperatur abgekühlt worden. Danach sind diese bei einer Temperatur von 440°C bis 560°C für ein bis zwei Stunden getempert worden und wieder langsam mit etwa 1 bis 2 K/min auf Raumtemperatur abgekühlt worden. Die in Tabelle 4 aufgelisteten Magnete sind von Sintertemperatur zunächst langsam mit etwa 2 K/min auf etwa 750°C und nach einer Haltezeit von etwa 1 Stunde mit etwa 30 bis 50 K/min schnell auf Raumtemperatur abgeschreckt worden. Diese Nd-Fe-B-Dauermagnete wurden nach einer anschließenden Temperung bei 470 bis 530°C wiederum schnell mit etwa 30 bis 50 K/min auf Raumtemperatur abgekühlt.Tables 3 and 4 list compositions and magnetic properties of isostatically pressed Nd-Fe-B permanent magnets with different effective rare earth and boron content. The bold indications refer to the low-boron alloys according to the invention. All Nd-Fe-B permanent magnets are produced by the conventional powder metallurgy process and sintered at about 1060 ° C to a density> 7.6 g / cm 3 . The Nd-Fe-B permanent magnets listed in Table 3 were slowly cooled from sintering temperature to about room temperature at about 1 to 2 K / min. Thereafter, they were tempered at a temperature of 440 ° C to 560 ° C for one to two hours and again slowly cooled at about 1 to 2 K / min to room temperature. The magnets listed in Table 4 were initially quenched from sintering temperature slowly to about 750 ° C at about 2 K / min and rapidly quenched to room temperature after about 1 hour holding at about 30 to 50 K / min. These Nd-Fe-B permanent magnets were after a subsequent annealing at 470 to 530 ° C again rapidly cooled at about 30 to 50 K / min to room temperature.

In Figur 6 sind die Werte für die Remanenz Br für die Legierungen aus Tabelle 3 in Abhängigkeit vom effektiven Gehalt an Bor und Seltenen Erden eingetragen. Zwei Niveaulinien verdeutlichen die Tendenz der zunehmenden Remanenz Br bei abnehmendem effektivem Seltenen-Erden-Gehalt und zunehmendem effektivem Bor-Gehalt. Bei einem effektiven Seltenen-Erden-Gehalt von < 30 Gew.% und einem effektiven Bor-Gehalt von >0,93 Gew.% wird für isostatisch gepreßte Nd-Fe-B-Dauermagnete eine Remanenz Br von mehr als 1,35 T erreicht. Bezüglich des Bor-Gehalts geht die Remanenz Br knapp unterhalb der Grenzlinie 2 zum Phasendreieck 1 durch ein Maximum.In FIG. 6, the values for the remanence B r for the alloys from Table 3 are plotted as a function of the effective content of boron and rare earths. Two level lines illustrate the trend of increasing remanence B r with decreasing RDE content and increasing boron content. With an effective rare-earth content of <30% by weight and an effective boron content of> 0.93% by weight, a remanence B r of more than 1.35 T is obtained for isostatically pressed Nd-Fe-B permanent magnets reached. Regarding the boron content, the remanence B r passes just below the boundary line 2 to the phase triangle 1 by a maximum.

In Figur 7 ist die Abhängigkeit der Koerzitivfeldstärke bei 150°C für die langsam gekühlten Nd-Fe-B-Dauermagnete aus Tabelle 3 dargestellt. Aus Figur 7 kann man entnehmen, daß sich mit abnehmendem effektivem Bor-Gehalt die Koerzitivfeldstärke HcJ bei 150°C erhöht. Gleiches gilt auch für die Koerzitivfeldstärke bei 20°C.FIG. 7 shows the dependence of the coercive force at 150 ° C. for the slowly cooled Nd-Fe-B permanent magnets from Table 3. From Figure 7 it can be seen that increases with decreasing effective boron content, the coercive force H cJ at 150 ° C. The same applies to the coercive force at 20 ° C.

Figur 8 zeigt schließlich die Abhängigkeit des Temperaturkoeffizienten von HcJ für langsam gekühlte Nd-Fe-B-Dauermagnete in Abhängigkeit vom effektiven Gehalt an Seltenen Erden und Bor. Auch hier ergeben sich mit abnehmendem effektivem Bor-Gehalt zunehmend bessere Werte für die Temperaturkoeffizienten. Zusammen mit der ansteigenden Koerzitivfeldstärke HcJ führt dies für langsam gekühlte Magnete zu einer Erhöhung der Koerzitivfeldstärke HcJ bei 150°C von unter 4,5 kOe auf Werte bis zu über 5,5 kOe. Diese besonders hohen Werte für die Koerzitivfeldstärke HcJ ergeben sich insbesondere für einen Seltenen-Erden-Gehalt [SE]eff von mehr als 28,9 Gew.%, wobei für den effektiven Bor-Gehalt die Beziehung gilt: 1,814 - 0,0303[SE]eff ≤ [B]eff ≤ 1,396 - 0,01491[SE]eff Finally, FIG. 8 shows the dependence of the temperature coefficient of H cJ on slowly cooled Nd-Fe-B permanent magnets as a function of the effective content of rare earths and boron. Here too, with decreasing effective boron content, increasingly better values for the temperature coefficients are obtained. Together with the increasing coercive force H cJ , this leads to an increase of the coercive force H cJ at 150 ° C from below 4.5 kOe to values up to more than 5.5 kOe for slowly cooled magnets. These particularly high values for the coercive field strength H cJ result in particular for a rare earth content [SE] eff of more than 28.9% by weight, the relationship for the effective boron content being: 1,814 - 0,0303 [SE] eff ≤ [B] eff ≤ 1.396 - 0.01491 [SE] eff

Das gleiche Bild zeigt sich für Nd-Fe-B-Dauermagnete, die von etwa 750°C und von Anlaßtemperatur schnell abgekühlt wurden. Gemäß Figur 9 und 10 werden allerdings sowohl für die Temperaturabhängigkeit als auch für die Absolutwerte im Vergleich zu den langsam gekühlt Nd-Fe-B-Dauermagnete etwas bessere Werte erreicht. Dadurch erweitert sich der Bereich, in dem die geforderten Eigenschaften, nämlich eine Remanenz Br > 1,35 T bei Raumtemperatur und eine Koerzitivfeldstärke HcJ > 5 kOe bei 150°C, erreicht werden.The same picture is shown for Nd-Fe-B permanent magnets, which were rapidly cooled from about 750 ° C and from annealing temperature. According to FIGS. 9 and 10, however, somewhat better values are achieved both for the temperature dependence and for the absolute values in comparison with the slowly cooled Nd-Fe-B permanent magnets. This extends the range in which the required properties, namely a remanence B r > 1.35 T at room temperature and a coercive force H cJ > 5 kOe at 150 ° C, are achieved.

Besonders hohe Werte für die Koerzitivfeldstärke bei 150°C ergeben sich für einen effektiven Gehalt an Seltenen Erden oberhalb von 28,5 Gew.%, insbesondere 28,7 Gew.%, wobei für den effektiven Bor-Gehalt die Beziehung gilt: 1,814 -0,0303 [SE]eff ≤ [B]eff ≤ 1,478 - 0,01801 [SE]eff Particularly high values for the coercive field strength at 150 ° C. result for an effective content of rare earths above 28.5% by weight, in particular 28.7% by weight, the relationship being valid for the effective boron content: 1.814 -0.0303 [SE] eff ≤ [B] eff ≤ 1.478 - 0.01801 [SE] eff

Abschließend sei angemerkt, daß neben Nd auch Pr verwendet werden kann, ohne daß die magnetischen Eigenschaften der Dauermagnete beeinträchtigt werden. Zusammensetzung in Gew.% Anlaß-temp. Br (20°C) (BH)max HcJ (20°C) HcJ (150°C) TK(HcJ) (20-150°C) SE, effektiv B, effektiv Dy Co Cu Ga (°C) (T) (MGOe) (kOe) (kOe) (%/K) 28,1 0,99 2,8 3,1 0,15 0,22 470 1,386 46,6 16,16 4 -0,579 28,1 0,99 2,8 3,1 0,15 0,22 500 1,372 45,7 15,06 -0,570 28,1 0,99 2,8 3,1 0,15 0,22 530 1,382 46,4 15,57 28,9 0,98 2,8 3 0,13 0,2 470 1,383 46,4 16,88 4,08 -0,583 28,9 0,98 2,8 3 0,13 0,2 500 1,378 46,1 17,24 4,39 -0,573 28,9 0,98 2,8 3 0,13 0,2 530 1,391 47,0 16,4 3,84 -0,589 29,6 0,97 2,8 2,9 0,1 0,18 470 1,376 46,0 16,27 4,02 -0,579 29,6 0,97 2,8 2,9 0,1 0,18 500 1,36 44,9 16,63 4,11 -0,579 29,6 0,97 2,8 2,9 0,1 0,18 530 1,374 45,8 9,96 28,7 0,94 2,9 3,1 0,17 0,22 500 1,374 45,8 15,69 4,42 -0,553 28,65 0,95 2,9 3,1 0,16 0,22 500 1,356 44,6 16,43 4,51 -0,558 28,6 0,96 3 3,2 0,16 0,22 500 1,375 45,9 16,89 4,59 -0,560 28,55 0,97 3 3,2 0,15 0,22 500 1,375 45,9 17,58 4,42 -0,576 28,5 0,98 3 3,2 0,15 0,21 500 1,382 46,4 17,15 4,42 -0,571 29,8 0,92 3,1 3,0 0,16 0,22 500 1,341 43,6 18,08 5,36 -0,541 29,8 0,93 3,1 3,0 0,15 0,22 500 1,352 44,4 18,24 5,26 -0,547 29,8 0,95 3,1 3,0 0,15 0,22 500 1,355 44,6 18,11 5,04 -0,555 29,8 0,96 3,1 3,0 0,14 0,22 500 1,363 45,1 17,34 4,49 -0,570 29,8 0,98 3,1 3,0 0,14 0,22 500 1,348 44,1 17,42 4,41 -0,574 29,9 0,94 3,3 3,1 0,14 0,21 440 1,369 45,5 15,95 3,79 -0,586 29,9 0,94 3,3 3,1 0,14 0,21 470 1,342 43,7 17,71 4,67 -0,566 29,9 0,94 3,3 3,1 0,14 0,21 500 1,353 44,4 17,79 4,6 -0,570 29,9 0,94 3,3 3,1 0,14 0,21 530 1,352 44,4 10,62 29,9 0,94 3,3 3,1 0,14 0,21 560 1,311 41,7 9,55 29,2 0,93 2,9 3 0,19 0,25 470 1,364 45,2 16,56 4,67 -0,552 29,2 0,93 2,9 3 0,19 0,25 500 1,351 44,3 17 4,95 -0,545 29,2 0,93 2,9 3 0,19 0,25 530 1,366 45,3 16,38 5 -0,534 29,5 0,93 2,9 3 0,17 0,23 470 1,347 44,0 17,57 5,12 -0,545 29,5 0,93 2,9 3 0,17 0,23 500 1,331 43,0 18,21 5,39 -0,542 29,5 0,93 2,9 3 0,17 0,23 530 1,344 43,8 17,97 5,42 -0,537 29,9 0,92 2,9 3 0,16 0,22 470 1,341 43,6 18,62 5,42 -0,545 29,9 0,92 2,9 3 0,16 0,22 500 1,331 43,0 19,08 5,71 -0,539 29,9 0,92 2,9 3 0,16 0,22 530 1,307 41,5 18,56 5,61 -0,537 Zusammensetzung in Gew.% Anlaß-temp. Br (20°C) (BH)max HcJ (20°C) HcJ (150°C) TH(WcJ) (20-150°C) SE, effektiv B, effektiv Dy Co Cu Ga (°C) (T) (MGOe) (kOe) (kOe) (%/K) 28,7 0,94 2.9 3,1 0,17 0,22 500 1,37 45,6 17,16 4,99 -0,546 28,65 0,95 2,9 3,1 0,16 0,22 500 1,341 43,6 18,02 5,15 -0,549 28,6 0,96 3 3,2 0,16 0,22 500 1,374 45,8 17,43 4,9 -0,553 28,55 0,97 3 3,2 0,15 0.22 500 1,372 45,7 16,33 4.61 -0.552 28,5 0.98 3 3,2 0,15 0,21 500 1,362 45,0 16,69 4,79 -0.551 29,8 0,92 3,1 3 0,16 0,22 500 1,343 43,8 18,3 5,59 -0,534 29,8 0,93 3,1 3 0,15 0,22 500 1,351 44.3 18,46 -5,5 -0,539 29,8 0,95 3,1 3 0,15 0,22 500 1,35 44,2 18,17 5,18 -0,550 29,8 0,96 3,1 3 0,14 0.22 500 1,354 44,5 16,87 4,71 -0,554 29,8 0,98 3,1 3 0,14 0,22 500 1,344 43.8 16,91 4,78 -0,552 28,8 0,95 3 2,8 0,14 0,26 500 1,359 44,8 18,65 5,66 -0,536 28,8 0,95 3 2,8 0,14 0,26 530 1,361 45,0 18,22 5,67 -0,530 29,2 0,93 2,9 3 0,19 0,25 470 1,354 44,5 18,61 5,65 -0,536 29,2 0,93 2,9 3 0,19 0,25 500 1,343 43,8 18,87 5,67 -0,538 29,2 0,93 2,9 3,0 0,19 0,25 530 1,355 44,6 18,73 5,82 -0,530 29,5 0,93 2,9 3,0 0,17 0,23 470 1,342 43,7 19,71 5,83 -0,542 29,5 0,93 2,9 3,0 0,17 0,23 500 1,323 42,5 19,56 5,92 -0,536 29,5 0,93 2,9 3,0 0,17 0,23 530 1,329 42,9 19,9 6,09 -0,534 29,9 0,92 2,9 3 0,16 0,22 470 1,337 43,4 20,3 6,09 -0,538 29,9 0,92 2,9 3 0,16 0,22 500 1,343 43,8 19,8 5,9 -0,539 29,9 0,92 2,9 3 0,16 0,22 530 1,335 43,3 20 6,09 -0,535 Finally, it should be noted that Pr can be used in addition to Nd, without the magnetic properties of the permanent magnets are affected. Composition in% by weight Tempering temp. B r (20 ° C) (BH) max H cJ (20 ° C) H cJ (150 ° C) TK (H cJ ) (20-150 ° C) SE, effective B, effective Dy Co Cu ga (° C) (T) (MGOe) (KOe) (KOe) (% / K) 28.1 0.99 2.8 3.1 0.15 0.22 470 1,386 46.6 16.16 4 -0.579 28.1 0.99 2.8 3.1 0.15 0.22 500 1,372 45.7 15.06 -0.570 28.1 0.99 2.8 3.1 0.15 0.22 530 1,382 46.4 15.57 28.9 0.98 2.8 3 0.13 0.2 470 1,383 46.4 16,88 4.08 -0.583 28.9 0.98 2.8 3 0.13 0.2 500 1,378 46.1 17.24 4.39 -0.573 28.9 0.98 2.8 3 0.13 0.2 530 1,391 47.0 16.4 3.84 -0.589 29.6 0.97 2.8 2.9 0.1 0.18 470 1,376 46.0 16.27 4.02 -0.579 29.6 0.97 2.8 2.9 0.1 0.18 500 1.36 44.9 16,63 4.11 -0.579 29.6 0.97 2.8 2.9 0.1 0.18 530 1,374 45.8 9.96 28.7 0.94 2.9 3.1 0.17 0.22 500 1,374 45.8 15.69 4.42 -0.553 28.65 0.95 2.9 3.1 0.16 0.22 500 1,356 44.6 16.43 4.51 -0.558 28.6 0.96 3 3.2 0.16 0.22 500 1.375 45.9 16.89 4.59 -0.560 28.55 0.97 3 3.2 0.15 0.22 500 1.375 45.9 17.58 4.42 -0.576 28.5 0.98 3 3.2 0.15 0.21 500 1,382 46.4 17.15 4.42 -0.571 29.8 0.92 3.1 3.0 0.16 0.22 500 1,341 43.6 18.08 5.36 -0.541 29.8 0.93 3.1 3.0 0.15 0.22 500 1,352 44.4 18.24 5.26 -0.547 29.8 0.95 3.1 3.0 0.15 0.22 500 1.355 44.6 18.11 5.04 -0.555 29.8 0.96 3.1 3.0 0.14 0.22 500 1,363 45.1 17.34 4.49 -0.570 29.8 0.98 3.1 3.0 0.14 0.22 500 1.348 44.1 17.42 4.41 -0.574 29.9 0.94 3.3 3.1 0.14 0.21 440 1,369 45.5 15,95 3.79 -0.586 29.9 0.94 3.3 3.1 0.14 0.21 470 1,342 43.7 17.71 4.67 -0.566 29.9 0.94 3.3 3.1 0.14 0.21 500 1,353 44.4 17.79 4.6 -0.570 29.9 0.94 3.3 3.1 0.14 0.21 530 1,352 44.4 10.62 29.9 0.94 3.3 3.1 0.14 0.21 560 1,311 41.7 9.55 29.2 0.93 2.9 3 0.19 0.25 470 1,364 45.2 16.56 4.67 -0.552 29.2 0.93 2.9 3 0.19 0.25 500 1,351 44.3 17 4.95 -0.545 29.2 0.93 2.9 3 0.19 0.25 530 1,366 45.3 16.38 5 -0.534 29.5 0.93 2.9 3 0.17 0.23 470 1,347 44.0 17.57 5.12 -0.545 29.5 0.93 2.9 3 0.17 0.23 500 1,331 43.0 18.21 5.39 -0.542 29.5 0.93 2.9 3 0.17 0.23 530 1,344 43.8 17.97 5.42 -0.537 29.9 0.92 2.9 3 0.16 0.22 470 1,341 43.6 18.62 5.42 -0.545 29.9 0.92 2.9 3 0.16 0.22 500 1,331 43.0 19.08 5.71 -0.539 29.9 0.92 2.9 3 0.16 0.22 530 1,307 41.5 18.56 5.61 -0.537 Composition in% by weight Tempering temp. B r (20 ° C) (BH) max H cJ (20 ° C) H cJ (150 ° C) TH (W cJ ) (20-150 ° C) SE, effective B, effective Dy Co Cu ga (° C) (T) (MGOe) (KOe) (KOe) (% / K) 28.7 0.94 2.9 3.1 0.17 0.22 500 1.37 45.6 17.16 4.99 -0.546 28.65 0.95 2.9 3.1 0.16 0.22 500 1,341 43.6 18,02 5.15 -0.549 28.6 0.96 3 3.2 0.16 0.22 500 1,374 45.8 17.43 4.9 -0.553 28.55 0.97 3 3.2 0.15 00:22 500 1,372 45.7 16.33 4.61 -0,552 28.5 0.98 3 3.2 0.15 0.21 500 1,362 45.0 16.69 4.79 -0,551 29.8 0.92 3.1 3 0.16 0.22 500 1,343 43.8 18.3 5.59 -0.534 29.8 0.93 3.1 3 0.15 0.22 500 1,351 44.3 18.46 -5.5 -0.539 29.8 0.95 3.1 3 0.15 0.22 500 1.35 44.2 18.17 5.18 -0.550 29.8 0.96 3.1 3 0.14 00:22 500 1,354 44.5 16.87 4.71 -0.554 29.8 0.98 3.1 3 0.14 0.22 500 1,344 43.8 16.91 4.78 -0.552 28.8 0.95 3 2.8 0.14 0.26 500 1,359 44.8 18.65 5.66 -0.536 28.8 0.95 3 2.8 0.14 0.26 530 1,361 45.0 18.22 5.67 -0.530 29.2 0.93 2.9 3 0.19 0.25 470 1,354 44.5 18.61 5.65 -0.536 29.2 0.93 2.9 3 0.19 0.25 500 1,343 43.8 18.87 5.67 -0.538 29.2 0.93 2.9 3.0 0.19 0.25 530 1.355 44.6 18.73 5.82 -0.530 29.5 0.93 2.9 3.0 0.17 0.23 470 1,342 43.7 19.71 5.83 -0.542 29.5 0.93 2.9 3.0 0.17 0.23 500 1.323 42.5 19.56 5.92 -0.536 29.5 0.93 2.9 3.0 0.17 0.23 530 1,329 42.9 19.9 6.09 -0.534 29.9 0.92 2.9 3 0.16 0.22 470 1,337 43.4 20.3 6.09 -0.538 29.9 0.92 2.9 3 0.16 0.22 500 1,343 43.8 19.8 5.9 -0.539 29.9 0.92 2.9 3 0.16 0.22 530 1,335 43.3 20 6.09 -0.535

Claims (14)

  1. Method for production of a permanent magnet from an alloy composed of at least one rare earth including yttrium, composed of iron, composed of the elements B, Co, Cu, Ga and Al, and having impurities resulting from the production process, with the effective rare earth content [SE]eff, the effective boron content [B]eff, the common content of Dy, Tb and Ho [Dy + Tb + Ho], the cobalt content [Co], the copper content [Cu] and the gallium content [Ga] as well as the aluminium content [Al] being governed by the following relationships:
    26.9% by weight ≤ [SE]eff ≤ 33% by weight
    2.185 - 0.0442 [SE]eff ≤ [B]eff ≤ 1.363 = 0.0136 [SE]eff
    [Dy + Tb + Ho] ≤ 17% by weight
    0.5% by weight ≤ [Co] ≤ 5% by weight
    0.05% by weight ≤ [Cu] ≤ 0.3% by weight
    0.05% by weight ≤ [Ga] ≤ 0.35% by weight
    0.02% by weight ≤ [Al] ≤ 0.3% by weight
    having the following method steps:
    orientation in the magnetic field and pressing of powder which has been produced by comminution of at least one fused body, to form a blank;
    sintering of the blank at temperatures between 1020°C and 1140°C;
    cooling of the blank down to temperatures below 300°C, it being cooled down at a mean cooling rate of ΔT1/Δt1 < 5 K/min above 800°C; and
    tempering and cooling of the blank, with the tempering temperature TA being governed, as a function of a mean cooling rate ΔT2/Δt2, by the following relationships:
    for ΔT2/Δt2 < 5 K/min: 450°C ≤ TA ≤ 550°C for [B]eff < 2.993 - 0.069 [SE]eff 460°C ≤ TA ≤ 510°C for [B]eff > 2.993 - 0.069 [SE]eff
    for 5 K/min ≤ ΔT2/Δt2 ≤ 100 K/min: 450°C < TA ≤ 550°C.
  2. Method according to Claim 1,
    characterized in that, after the sintering process, the blank is held at a holding temperature between 700 and 800°C for a time between half an hour and 2 hours.
  3. Method according to Claim 2,
    characterized in that, after the sintering process, the blank is cooled down from the holding temperature at a mean cooling rate of ΔT3/Δt3 > 5 K/min.
  4. Method according to Claim 3,
    characterized in that the cooling rates ΔT2/Δt2 and ΔT3/Δt3 are between 30 and 50 K/min.
  5. Method according to Claim 1 or 2,
    characterized in that, after the sintering process, the blank is cooled down from the holding temperature at a mean cooling rate of ΔT3/Δt3 < 5 K/min.
  6. Method according to Claim 5,
    characterized in that the cooling rates ΔT1/Δt1 to ΔT3/Δt3 are between 1 and 2 K/min.
  7. Method according to one of the preceding claims,
    characterized in that the effective boron content [B]eff is governed by the following relationship: 1.814 - 0.0303 [SE]eff ≤ [B]eff ≤ 1.363 - 0.0136 [SE]eff.
  8. Method according to one of the preceding claims,
    characterized in that the rare earth content [SE]eff is above 28.9% by weight, with the effective boron content being governed by the following relationship: 1.814 - 0.0303 [SE]eff ≤ [B]eff ≤ 1.396 - 0.01491 [SE]eff.
  9. Method according to one of the preceding claims,
    characterized in that the rare earth content [SE]eff is above 28.5% by weight, with the effective boron content being governed by the following relationship: 1.814 - 0.0303 [SE]eff ≤ [B]eff ≤ 1.478 - 0.01801 [SE]eff.
  10. Method according to Claim 9,
    characterized in that the rare earth content [SE]eff is above 28.7% by weight.
  11. Method according to one of the preceding claims,
    characterized in that the alloy has a Co content of between 2.5 and 3.5% by weight.
  12. Method according to one of the preceding claims,
    characterized in that the Cu content is between 0.1 and 0.2% by weight.
  13. Method according to one of the preceding claims,
    characterized in that the Ga content is between 0.20 and 0.30% by weight.
  14. Method according to one of the preceding claims,
    characterized in that the rare earths are selected from the group of elements Nd, Pr, Dy, Tb.
EP00962502A 1999-09-24 2000-09-18 METHOD FOR PRODUCING PERMANENT MAGNETS ON THE BASIS OF BORON-LOW Nd-Fe-B ALLOY Expired - Lifetime EP1214720B1 (en)

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DE19945942A DE19945942C2 (en) 1999-09-24 1999-09-24 Process for the production of permanent magnets from a low-boron Nd-Fe-B alloy
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PCT/EP2000/009128 WO2001024203A1 (en) 1999-09-24 2000-09-18 BORON-LOW Nd-Fe-B ALLOY AND METHOD FOR PRODUCING PERMANENT MAGNETS ON THE BASIS OF SAID ALLOY

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WO2001024203A1 (en) 2001-04-05
JP2003510467A (en) 2003-03-18
DE19945942A1 (en) 2001-04-12
DE50009741D1 (en) 2005-04-14
DE19945942C2 (en) 2003-07-17
EP1214720A1 (en) 2002-06-19

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