CN1231754C - Quality assessment method and production method of rare earth magnet alloy ingot - Google Patents

Abstract

A rare earth magnet alloy ingot comprising the following composition: RE (RE is at least one metal element selected from lanthanoids, including Y (i.e., Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu)) is 27 to 34 mass%; b (boron) is 0.7 to 1.4 mass%; the balance being TM (TM represents a metal including a transition metal as an essential component, including Fe), the mass thereof being determined by maintaining an alloy ingot under a reduced-pressure atmosphere, subsequently placing the ingot in a hydrogen atmosphere, and then measuring the hydrogen absorption behavior of the ingot in the hydrogen atmosphere. The hydrogen absorption behavior is determined by measuring the change with time in the amount of hydrogen absorbed by the ingot from the time the ingot is placed in a hydrogen atmosphere.

Description

Quality assessment method and production method of rare earth magnet alloy ingot

technical field

The present invention relates to a method for determining the quality of an ingot of a rare earth magnet alloy (referred to as RE-TM-B magnet alloy) having the following composition: RE (RE is at least one metal element selected from the lanthanides, including Y (i.e. Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu)) are 27-34% by mass; B (boron) is 0.7-1.4% by mass; the rest is TM (TM means a transition metal-containing metal as an essential component, including Fe). The present invention also relates to a method of producing the alloy ingot, a rare earth magnet alloy ingot and a rare earth magnet.

Background technique

Recently, there has been a growing demand for RE-TM-B magnet alloys used in voice coil motors (VCMs) used in hard disk drives for personal computers, magnetic resonance imaging (MRI) devices for medical use, and motors. In keeping with the trend to increase the performance and reduce the size of these devices, it is desirable to further enhance the magnets themselves.

Sintered magnets using the RE-TM-B magnet alloy were produced according to the following procedure. Specifically, it is appropriate to use rare earth metals or matrix alloys such as REFe (RE-Fe binary alloy) as the RE source, solid boron or iron-boron alloy as the boron (B) source, and pure iron or atomic iron (Atomiron) as the TM source and other auxiliary elements. These sources are melted in alumina crucibles placed in a vacuum or inert atmosphere, and the resulting molten alloy is cast to produce alloy ingots. The resulting alloy ingot is pulverized under nitrogen or an inert atmosphere to form an alloy powder having a particle size of about several micrometers. A liquid or solid (powder form) lubricant is added to the alloy during or after comminution. The obtained alloy powder is shaped in a magnetic field and the compact is sintered in vacuum or in an inert atmosphere, thereby producing a sintered compact. The shape of the resulting sintered block is adjusted, and the surface of the sintered block is plated with nickel or aluminum to prevent corrosion or erosion, thereby obtaining a sintered magnet as a finished product.

Among the magnetic properties of sintered magnets, remanence, coercive force and perpendicularity properties are particularly important. In order to increase the remanence, the crystal orientation of each powder particle and the density of the sintered mass are preferably high. In order to increase the coercive force, it is necessary to reduce the particle size of the pulverized alloy. In order to improve squareness performance, the particle size distribution of the powder must be narrow. In other words, the magnetic properties of a sintered magnet mainly depend on the properties of the alloy powder used to produce the magnet.

Alloy powder is produced according to the following process. Specifically, the cast alloy ingot is coarsely crushed into fragments with a size of preferably about several centimeters (in this specification, the term "coarsely crushed" means that the alloy ingot is crushed into fragments with a size of 0.1-10 cm). Place the pieces in an airtight container and adjust the interior of the container to a vacuum. Subsequently, hydrogen gas is introduced into the vessel, thereby maintaining the fragments in a hydrogen atmosphere, inducing cracking to comminute the alloy fragments, based on the phenomenon that the alloy expands when it absorbs hydrogen. This operation is called hydrogen decrepitation.

Hydrogenation occurs more easily in the RE-rich phase than in the main phase (hereinafter referred to as the RE-rich phase), which is distributed in the main phase of the RE-TM-B magnet alloy. Hydrogen detonation using the above properties is a step in which cracks are generated by expansion accompanying hydrogenation, and the cracks propagate from the surface of the alloy ingot in a chain transfer manner, thereby pulverizing the ingot.

Subsequently, the alloy ingot that has undergone hydrogen explosion is further coarsely crushed using a pulverizer such as a Brawn mill to form a powder with a size of several hundreds of micrometers, and then finely pulverized using a pulverizer such as a jet mill to reduce the size to about several micrometers.

It can be considered that the necessary properties of the alloy powder preferably satisfy all of the following conditions:

1) The first condition is that individual particles of the powder do not contain multiple crystals. This condition is important for orienting the crystals in one direction during application of a magnetic field to the powder. If a particle has many crystals with different crystal orientations, during application of a magnetic field, the crystal orientations of the particle as a whole are aligned in a direction consistent with the sum of crystal axis vectors in the particle, and a high degree of crystal orientation cannot be obtained.

2) The second condition is that the RE-rich phase exists on the surface of each particle of the powder, and the powder does not contain particles formed only by the RE-rich phase. This condition is quite important because the RE-rich phase plays an important role as the liquid phase in the liquid phase sintering process. In other words, in order to produce a high-density sintered product of alloy powder by performing homogeneous liquid phase sintering, it is preferable that the liquid phase is uniformly distributed in the shaped compact. If the RE-rich phase is made to exist only on the surface of each particle of the powder, the liquid phase can be distributed almost uniformly. In the case where the RE-rich phase exists inside the particles, a part of the RE-rich phase that does not participate in the liquid-phase sintering process is generated, so that effective utilization of the RE-rich phase cannot be achieved. When some particles are formed of only the RE-rich phase, the distribution of the RE-rich phase becomes broad and the dispersion of the RE-rich phase becomes poor, so that a highly uniform distribution of the RE-rich phase cannot be achieved.

3) The third condition is that the particle size of the powder measured with a Fisher Sub-SieveSizer is about 3-4 microns and has a narrow particle size distribution. The properties of the sintered compact obtained by shaping the powder and sintering vary with the particle size of the powder. When the particle size distribution is wide, the fine particles contained in the powder increase the activity of the powder to disadvantageously increase the oxygen concentration of the produced magnet, while when the powder contains large-sized particles or the particle size is 5 micrometers or more, the The magnetic properties of the produced magnets, especially the coercive force, are reduced.

By performing hydrogen detonation prior to mechanical pulverization, microcracks can be pre-generated in alloy ingots along RE-rich phases present in grain boundaries and in grains. The particle size of the resulting powder is determined by the metallographic structure of the alloy. Therefore, a rare earth magnet alloy ingot having a suitable alloy metallographic structure was subjected to hydrogen explosion followed by pulverization, thereby obtaining alloy powder satisfying all the above-mentioned conditions 1), 2) and 3).

A preferred method for casting alloys suitable for producing alloy powders having a preferred particle size distribution is the strip casting method (hereinafter referred to as the SC method). In the SC method, molten alloy is poured onto copper rolls, thereby casting the alloy into ribbon. The cast alloy ribbon is introduced into a container in which it is collected, and its cooling rate is controlled. As disclosed in Japanese Unexamined Patent Application First Publication No. 09-170055, when cooling, the cooling rate of the alloy ribbon is preferably controlled to be 300° C./sec or more in the range of the melting temperature to 800° C. In the range of 800-600°C, it is controlled to be 10°C/sec or less.

On the contrary, when pulverizing an alloy ingot produced by the conventional hinged casting method, it is likely that only RE-rich phase powder particles are formed, so that proper particles cannot be obtained.

Even with the SC method, it is not preferable to deviate from the above conditions related to the cooling rate. The reason for this is as follows.

When the cooling rate in the range of 800-600 °C exceeds 10 °C/s, the distribution of RE-rich phase is finer. By performing hydrogen explosion on such SC alloy flakes, the expansion due to hydrogenation of the RE-rich phase is reduced. Therefore, the crack generation rate in the SC alloy sheet decreases. Therefore, the following problems arise.

a) The above SC alloy flakes require a longer time for hydrogen detonation compared with SC alloy flakes cast under optimal conditions. If the time is short, a portion where no cracks have occurred will remain in the alloy sheet. Therefore, the powders produced by pulverizing these alloy flakes tend to contain RE-rich phases not on the surface of the particles but inside the particles.

b) Even though the hydrogen detonation proceeds for sufficient time to facilitate crack generation, the cracks generated along the RE-rich phase are too fine, resulting in an excessively reduced particle size powder. Therefore, such alloy powders are easily oxidized, and the fluidity of the powders is highly prone to significantly lowering.

In contrast, when the cooling rate in the range of 800–600°C is 0.5°C/s or less, the RE-rich phase is more sparsely dispersed, and where RE-rich phases are found, dense phases tend to exist. Therefore, the following problems arise.

c) Although the hydrogen detonation of the RE-rich phase can be completed in a very short time, the cracks due to the hydrogen detonation are rather sparsely dispersed, resulting in powders with large particle sizes. Even if the particle size was successfully adjusted by mechanical pulverization, the uniformity of particle surface coverage with the RE-rich phase was reduced, and there was a higher probability that particles formed only from the RE-rich phase were mixed into the powder.

Therefore, according to the metallographic structure of the rare earth magnet alloy ingot, the particle size distribution of the alloy powder that has undergone hydrogen explosion changes, and the hydrogen absorption performance of the alloy also changes.

As mentioned above, hydrogen explosion prior to mechanical pulverization is an important issue in producing alloy powders from RE-TM-B magnet alloy ingots with a particle size distribution suitable for forming sintered magnets with excellent magnetic properties.

However, conventionally, no definite method has been proposed to determine the quality of rare earth magnet alloy ingots, thereby quantitatively evaluate the degree of hydrogen detonation of RE-TM-B magnet alloys, and correlate the evaluation results with the magnetic properties.

The relationship between metallographic structure and cooling behavior of alloys has been reported. For example, Japanese Unexamined Patent Application First Publication No. 08-269643 discloses the relationship between the metallographic structure of the alloy and the primary cooling rate and secondary cooling rate, and Japanese Unexamined Patent Application First Publication No. 09 -170055 discloses the relationship between the metallographic structure of alloys and their cooling behavior in the temperature range 800-600°C. However, these references do not mention how changes in hydrogen detonation behavior affect the properties of alloy powders, and they do not mention how changes in hydrogen detonation behavior affect the magnetic properties of magnets produced from said powders.

During hydrogen detonation of rare earth alloy ingots, the fragmentation behavior is controlled by the RE-rich phases present in the alloy, so the distribution of RE-rich phases is very important. However, it is difficult to predict the particle size distribution of the alloy powder and the magnetic properties of the sintered magnets produced in subsequent steps after the completion of hydrogen detonation with the traditional method of evaluating the distribution of RE-rich phases in rare earth magnet alloy ingots. Therefore, disadvantageously, the quality of a cast alloy ingot of a rare earth magnet alloy cannot be determined until a magnet is finally produced from the ingot.

In contrast, the present inventors have found that if cast rare earth alloy ingots can be produced that exhibit appropriate hydrogen absorption behavior, alloy powders with preferred particle size distribution can be produced by hydrogen explosion and sintered magnets with excellent magnetic properties can be produced.

Contents of the invention

It is therefore an object of the present invention to provide a method for determining the quality of rare earth magnet alloy ingots for selecting RE-TM-B magnet alloy ingots capable of providing alloy powders for producing sintered magnets with excellent magnetic properties. Another object of the present invention is to provide a method for producing a rare earth magnet alloy ingot including a method for determining the mass. Yet another object is to provide rare earth magnet alloy ingots for producing sintered magnets with excellent magnetic properties. In addition, another object is to provide a rare earth magnet manufactured from powder produced by pulverizing said alloy ingot.

Accordingly, a first aspect of the present invention is to provide a method of determining the quality of a rare earth magnet alloy ingot comprising the following composition: RE (RE is at least one metal element selected from the lanthanides, Including Y (ie Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu)) is 27-34% by mass; B (boron) is 0.7-1.4 % by mass; the rest is TM (TM means metals containing transition metals as basic components, including Fe), the method comprising the steps of: keeping the ingot in a reduced-pressure atmosphere, then placing it in a hydrogen atmosphere, when the ingot is kept in a hydrogen atmosphere In the middle, the hydrogen absorption behavior of the ingot was determined.

In addition, the hydrogen absorption behavior of the rare earth magnet alloy ingot can be determined by measuring the change with time in the amount of hydrogen absorbed by the ingot from the moment the alloy ingot is placed in a hydrogen atmosphere.

In addition, the rare earth magnet alloy ingot may be roughly crushed and then kept in a reduced-pressure atmosphere.

In addition, the rare earth alloy ingot may be maintained in a reduced-pressure atmosphere at a pressure of 8×10 ^-4 to 1×10 ^-2 Pa.

In addition, the rare earth alloy ingot can be placed in a hydrogen atmosphere at a temperature of 273-373K.

In addition, the rare earth alloy ingot can be placed in a hydrogen atmosphere at a pressure of 101-160 kPa.

In addition, the rare earth magnet ingot can be produced by a rapid cooling casting method.

In addition, the rapid cooling casting method may be a strip casting method.

In addition, the hydrogen absorption behavior of the rare earth magnet alloy ingot can be determined by measuring the time required from the moment when the rare earth magnet alloy ingot is placed in a hydrogen atmosphere to when the amount of absorbed hydrogen reaches 1% of the maximum amount of hydrogen that the rare earth magnet ingot can absorb .

In addition, the second aspect of the present invention is to provide a method for producing a rare earth magnet alloy ingot, which includes the step of: using the method for determining the quality of a rare earth magnet alloy ingot according to the first aspect of the present invention to determine the quality of a rare earth magnet alloy ingot, Rare earth magnet alloy ingots of unsatisfactory quality are removed in one step of magnet production.

In addition, the third aspect of the present invention is to provide a rare earth magnet alloy ingot containing the following composition: RE (RE is at least one metal element selected from the lanthanides, including Y (i.e. Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu)) are 27-34% by mass; B (boron) is 0.7-1.4% by mass; the rest are TM (TM means containing transition metal , a metal comprising Fe as a basic component), wherein, when the rare earth magnet alloy ingot is kept in a reduced-pressure atmosphere of 8×10 ^-4 -1×10 ^-2 Pa and the ingot is then placed under a pressure of 101-160 kPa and kept When in a hydrogen atmosphere of 283-313K, determine the hydrogen absorption behavior of a rare earth magnet alloy ingot, that is, from placing the ingot in a hydrogen atmosphere until the amount of hydrogen absorbed reaches 1% of the maximum amount of hydrogen that can be absorbed in the rare earth magnet ingot The time required for this alloy is 200-2,400 seconds, and the maximum hydrogen absorption rate of the alloy is 1.0×10 ^-4 -1.2×10 ^-3 mass %/second.

In addition, the rare earth magnet alloy ingot may be roughly crushed and then kept in a reduced-pressure atmosphere.

In addition, the rare earth magnet alloy ingot can be produced by a rapid cooling casting method.

In addition, the rapid cooling casting method may be a strip casting method.

In addition, a fourth aspect of the present invention is to provide a rare earth magnet produced from the rare earth magnet alloy ingot according to the third aspect of the present invention.

In addition, the fifth aspect of the present invention is to provide a rare earth magnet alloy ingot containing the following composition: RE (RE is at least one metal element selected from the lanthanides, including Y (i.e. Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu)) is 27-34 mass % (the total amount of Eu, Gd, Tb, Dy, Ho, Yb and Lu is limited to less than 1 % by mass); B (boron) is 0.7-1.4% by mass; the rest is TM (TM means metals containing transition metals as basic components, including Fe); wherein, when the rare earth magnet alloy ingot is kept at 8×10 ^-4 -1×10 ^-2 Pa in a reduced-pressure atmosphere, and then placed in a hydrogen atmosphere at a pressure of 101-160kPa and kept at 283-313K to determine the hydrogen absorption behavior of a rare earth magnet alloy ingot, that is, since the ingot is placed in The time required for the absorbed hydrogen to reach 1% of the maximum hydrogen that can be absorbed in the rare earth magnet ingot in the hydrogen atmosphere is 100-1,800 seconds, and the maximum hydrogen absorption rate of the alloy is 1.2×10 ^-4 -1.5× 10 ^-3 mass %/sec.

In addition, the rare earth magnet alloy ingot may be roughly crushed and then kept in a reduced-pressure atmosphere.

In addition, the rare earth magnet alloy ingot can be produced by a rapid cooling casting method.

In addition, the rapid cooling casting method may be a strip casting method.

In addition, a sixth aspect of the present invention provides a rare earth magnet produced from the rare earth magnet alloy ingot according to the fifth aspect of the present invention.

Brief description of the drawings

Fig. 1 is a schematic diagram showing the change of the amount of hydrogen gas absorbed in a rare earth alloy ingot with time.

Fig. 2 is a graph showing the time-dependent change in hydrogen absorption rate of a rare earth alloy ingot.

Fig. 3 is a comparison diagram showing the amount of hydrogen absorbed by different types of rare earth alloy ingots over time.

Fig. 4 is a comparative graph showing the rate of hydrogen absorption by different types of rare earth alloy ingots as a function of time.

FIG. 5A is a graph showing the relationship between T and _BHmax of Alloy A. FIG.

FIG. 5B shows the relationship between _rmax and _BHmax of Alloy A. FIG.

FIG. 6A is a graph showing the relationship between T and BHmax of Alloy B. _FIG .

FIG. 6B is a graph showing the relationship between _rmax and _BHmax of Alloy B. FIG.

Fig. 7A is a graph showing the relationship between T and _BHmax of Alloy C.

Fig. 7B is a graph showing the relationship between _rmax and _BHmax of Alloy C.

FIG. 8A is a graph showing the relationship between T and _BHmax of Alloy D. FIG.

Fig. 8B is a graph showing the relationship between _rmax and _BHmax of alloy D.

FIG. 9A is a graph showing the relationship between T and _BHmax of Alloy E. FIG.

FIG. 9B is a graph showing the relationship between _rmax and _BHmax of Alloy E. FIG.

FIG. 10A is a graph showing the relationship between T and _BHmax of Alloy F. FIG.

Fig. 10B is a graph showing the relationship between _rmax and _BHmax of alloy F.

best practice

The present inventors studied the hydrogen absorption behavior of RE-TM-B magnet alloy ingots, and determined the characteristics in hydrogen absorption behavior of rare earth magnet alloy ingots suitable for producing alloy powders capable of producing sintered magnets with excellent magnetic properties. Specifically, by determining the hydrogen absorption behavior under the following conditions, it can be determined whether the RE-rich phase is properly distributed in the rare earth magnet alloy ingot, and whether the alloy ingot can be properly cracked along the RE-rich phase by hydrogen detonation.

Specifically, a rare earth magnet ingot alloy having the following composition and preferably produced by a rapid cooling casting method is kept in an airtight container under a reduced pressure atmosphere of preferably 8×10 ⁻⁴ to 1×10 ⁻² Pa: RE (RE is at least one metal element selected from the lanthanides, including Y (ie, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) as 27- 34% by mass; B (boron) is 0.7-1.4% by mass; the rest is TM (TM means metals containing transition metals as basic elements, including Fe), and subsequently, the ingot is preferably kept at 273-373K and 101 In a hydrogen atmosphere at -160 Pa. By studying the hydrogen absorption behavior of the alloy ingot during its holding period, the quality of the rare earth magnet alloy ingot can be determined.

According to the method for measuring rare earth magnet alloy ingots described above, the properties of rare earth magnet alloy ingots capable of producing sintered magnets with excellent magnetic properties have been determined. Specifically, the hydrogen absorption behavior of a rare earth magnet alloy ingot capable of producing a sintered magnet with excellent magnetic properties is characterized as follows. ^That is, hydrogen gas ( ¹⁰¹ -160 kPa), the alloy ingot shows that the time required from the moment the ingot is placed in the hydrogen atmosphere to when the amount of hydrogen absorbed reaches 1% of the maximum amount of hydrogen absorbed in the alloy is 200 to 2,400 seconds, and the The maximum hydrogen absorption rate of the alloy is in the range of 1.0×10 ^-4 -1.2×10 ^-3 mass %/sec.

Concerning rare earth magnet alloy ingots having the following composition and preferably produced by rapid cooling casting: RE (RE is at least one metal element selected from the lanthanides, including Y (i.e., Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) is 27-34% by mass (the total amount of Eu, Gd, Tb, Dy, Ho, Yb and Lu is limited to less than 1% by mass); B (boron) is 0.7-1.4% by mass; the rest is TM (TM means metals containing transition metals as basic elements, including Fe), and the hydrogen absorption behavior of rare earth magnet alloy ingots capable of producing sintered magnets with excellent magnetic properties is characterized as follows That is, ^hydrogen gas ( ¹⁰¹ -160kPa), the alloy ingot shows that the time required from the moment the alloy ingot is placed in a hydrogen atmosphere to when the amount of hydrogen absorbed reaches 1% of the maximum amount of hydrogen absorbed in the alloy is 100-1,800 seconds, and the The maximum hydrogen absorption rate of the alloy is in the range of 1.2×10 ^-4 -1.5×10 ^-3 mass %/sec.

Therefore, in the method for producing rare earth magnet ingots of the present invention, by using the method for determining the quality of rare earth magnet alloy ingots according to the present invention, the quality of rare earth magnet alloys is predicted, and alloy ingots of unsatisfactory quality are removed from the magnet production step removed, thereby improving the production efficiency of the excellent rare earth magnet alloy ingot.

In a preferred mode of the above method for producing rare earth magnet alloy ingots, the RE-TM-B magnet alloy is cast by a rapid cooling casting method, thereby providing an alloy metallographic structure satisfying the above hydrogen absorption conditions.

Examples of applicable rapid cooling casting methods include gas atomization method, spray molding method, strip casting method, among which strip casting method (hereinafter referred to as SC method) is particularly preferable.

During rapid cooling casting, in the casting condition, the average cooling rate is controlled to be 300°C/sec or more in the range of molten alloy temperature (eg 1,400°C) to 1,000°C, and 0.5-10°C in the range of 800-600°C °C/sec. More preferably, the average cooling rate is controlled to be 500°C/sec or more within the temperature range of the molten alloy to 1,000°C, and 0.5-5.0°C/sec within the range of 800-600°C.

The average cooling rate during rapid cooling casting was measured according to the following procedure. For example, when using the SC method, the main phase of the alloy is cooled on rotating rolls. Therefore, an immersion thermocouple is used to measure the temperature of the molten alloy just before it falls on the roll, and a two-color radiation pyrometer is used to measure the temperature of the molten alloy in which the main phase is solidifying while moving on the roll. The difference between these two temperatures was subtracted by the corresponding time to calculate the average cooling rate in the range from the temperature of the molten alloy to 1,000°C (the temperature at which the main phase in the alloy completely solidifies). In the product collection zone, the product has an initial temperature in the range of 700-900°C, depending on the composition of the alloy, and is gradually cooled. Therefore, the temperature of the alloy remaining in the product collection zone was measured as a function of time to calculate an average cooling rate in the range of 800-600°C.

A preferred mode of implementing the casting method of the present invention to produce a rare earth magnet alloy is described below.

First, alloy raw materials are mixed so as to obtain the following composition: RE = 27-34 mass %; B = 0.7-1.4 mass %; TM = balance. The raw material mixture is heated in a vacuum chamber in a vacuum atmosphere or in an inert gas atmosphere to produce a molten alloy.

The rapid cooling casting method will be described below taking the SC method as an example.

The equipment used in the SC method consists of a tundish for bringing the molten alloy into contact with a copper roll; a rapid cooling roll for rapidly cooling the molten alloy; and a vessel for collecting the solidified alloy, these parts are mounted in a vacuum in the room.

The molten alloy is poured into a tundish, and the molten alloy is poured from the tundish onto rapidly cooled rolls, thereby casting the molten alloy. The cooling rate in the range of the temperature of the molten alloy (for example, 1,400°C) to 1,000°C corresponds to the cooling rate of the molten alloy moving on the rapid cooling roll. The cooling speed of the molten alloy moving on the fast cooling roll can be adjusted by changing the peripheral speed of the fast cooling roll. For example, the greater the thickness of the molten alloy controlled by reducing the peripheral speed of the rapid cooling roll, the slower the cooling rate. The alloy thus solidified is collected in a container, and the cooling rate of the alloy in the range of 800-600°C is controlled by a predetermined method; for example, maintaining the temperature inside the container or flowing an inert gas through the container. Generally, in the case of casting an alloy by a rapid cooling method such as the SC method, only the cooling rate in the range from the temperature of the molten alloy to the solidification temperature of the alloy is considered. In contrast, in the present invention, a rapidly cooled alloy exhibiting suitable hydrogen absorption behavior can be obtained by controlling the cooling rate in the range of 800-600°C.

A preferred alloy composition of the rare earth magnet alloy of the present invention will be described below.

Regarding rare earth elements, it is preferable not to contain Sm, Er, and Tm. These elements exhibit longitudinal anisotropy when forming RE ₂ TM ₁₄ B compounds, thereby reducing magnetic anisotropy.

It is difficult to control the amount of Al to 0.05% by mass or less because Al inevitably migrates from the crucible used in casting into the molten alloy. Although Al is effective in increasing the coercive force, the addition of an excessive amount of Al results in a decrease in the remanence. Therefore, its amount is preferably controlled to be 3% by mass or less.

Cu is preferably added, which has the effect of enhancing the coercive force. However, the addition of an excessive amount of Cu results in a decrease in the remanence. Therefore, its amount is preferably controlled to be 3% by mass or less.

The amount of oxygen is difficult to control to 0.02% by mass or less because oxygen inevitably migrates into the raw material or molten alloy during casting. Excess oxygen adversely affects magnetic properties. Therefore, its amount is preferably controlled to be 1% by mass or less.

The amount of carbon is difficult to control to 0.005% by mass or less because carbon inevitably migrates into the raw material or molten alloy during casting. An excessively high content of carbon adversely affects magnetic properties, and therefore, its amount is preferably controlled to 0.2% by mass or less.

A preferred method of hydrogen detonation used in the present invention to determine the behavior of absorbing hydrogen will be described below.

Preferably, the equipment used to perform the hydrogen detonation determining hydrogen absorption behavior can maintain temperature; is suitable for vacuum control by sliding vane rotary vacuum pumps or hydraulic diffusion pumps; and can withstand internal pressures of about 200 kPa. The alloy sample to be machined is broken up slightly, preferably to about 1-3 microns, in order to remove a certain amount of the undesired oxide film covering the surface of the sample, thereby creating an initial cut surface. In order to suppress changes in measurement temperature due to heat accompanying hydrogen absorption, the SC sheet was placed in a sample container so that the sheet was spread thinly without overlapping, or with a maximum of one or two overlapping sheets. The container is fixed in the device in an airtight manner. The internal pressure is reduced to about 8×10 ^-4 to 1×10 ^-2 Pa, and the sample is kept in a reduced-pressure atmosphere for a predetermined time (for example, about 3 hours). While the temperature inside the device is maintained at a predetermined temperature in the range of 273-373K, preferably 283-313K, hydrogen gas is introduced into the device up to 101-160 kPa, preferably 101-140 kPa. The time at which the sample began to be kept in the hydrogen atmosphere was defined as the initial time, and the subsequent change in pressure within the apparatus with time was measured.

Although the temperature varies with the environment during the measurement, the temperature is preferably in the range of 283-313K. When the temperature is 283K or lower, especially 273K or lower, the absorption of hydrogen gas produced by the alloy occurs slowly, and the absorption of hydrogen gas takes a significantly long time, resulting in a decrease in efficiency, while when the temperature is 313K or higher, especially At 373K or higher, the hydrogen absorption reaction of the alloy proceeds at an excessive rate, making mass detection difficult. In order to compare the hydrogen uptake behavior of the samples, the hydrogen detonation must be performed at the same temperature.

In the condition of a reduced-pressure atmosphere, a reduced pressure of 1× ^10-2 Pa or higher is insufficient to remove water and gas molecules adhering to the surface of the alloy ingot, thus hindering the total absorption of hydrogen, while even using a hydraulic diffusion pump to achieve A significantly long time is also required for decompression of 8×10 ^-4 Pa or less. Such a long time is not preferable from the viewpoint of measurement efficiency. Therefore, the reduced pressure atmosphere condition is preferably controlled to be 8×10 ^-4 -1×10 ^-2 Pa.

Under hydrogen atmosphere conditions, when the pressure is 160 kPa or higher, the hydrogen absorption reaction of the alloy ingot occurs at an excessive rate, making mass measurement difficult. When the pressure is 101kPa or lower, it takes a long time to perform the test because the hydrogen absorption reaction is slow, and the internal pressure of the device is lower than the external pressure, resulting in migration of air into the device due to defects in the device, for example, in In some cases a detonation gas is formed. This is also disadvantageous. Therefore, the hydrogen pressure is preferably controlled to be 101-160kPa.

Based on the above-mentioned change in pressure with time in the apparatus during hydrogen detonation, the change with time in the amount of hydrogen absorbed in the rare earth magnet alloy ingot (absorbed hydrogen behavior) was calculated. Graph the data obtained to obtain a curve. Figure 1 shows a schematic representation of this curve. From this curve, the maximum absorbable hydrogen amount corresponding to the absorbed hydrogen amount that no longer increases due to absorption saturation is obtained. The time "T" required from the start of hydrogen pressurization until the absorbed hydrogen amount reached 1% of the maximum absorbable hydrogen amount in the rare earth magnet alloy was calculated. In addition, the gradient is calculated relative to each tangent to the graph of Figure 1, and the gradient versus time is plotted on another graph, thereby providing a graph representing the hydrogen uptake rate of the alloy versus time. FIG. 2 is a schematic diagram showing the distribution. Since this type of curve usually has a peak, the maximum value " _rmax " of the hydrogen absorption rate can be calculated by reading the height of this peak. Using the two indices T and _rmax thus obtained, the condition of the rare earth alloy was evaluated, and this evaluation was used to determine whether magnetic properties suitable for the sintered magnet could be obtained.

In this specification, the amount of hydrogen gas absorbed in the rare earth magnet alloy ingot is represented by the ratio (percentage) of the mass of hydrogen gas absorbed in the rare earth magnet alloy ingot to the mass of the ingot. Therefore, the unit of the amount of absorbed hydrogen is mass %. In addition, the present inventors defined the experimental hydrogen absorbable amount as the absorbed hydrogen amount that has reached saturation and no longer changes, and at which time the absorbed hydrogen rate is reduced to about 5×10 ⁻⁶ mass %/sec or less.

Figures 3 and 4 show the results for some samples. Fig. 3 is a graph showing the change with time of the amount of hydrogen absorbed in the alloy, and Fig. 4 is a graph showing the change with time of the hydrogen absorbing rate of the alloy. In Figs. 3 and 4, each reference numeral (1), (2) and (3) represents a different alloy, indicating the cooling rate during rapid cooling casting in the range of 800-600°C. The order of cooling rate: (3)>(2)>(1). It is clear from these figures that the lower the cooling rate in the range of 800-600°C, the smaller "T" and the larger " _rmax ". All relevant alloys clearly show this trend and it is independent of alloy composition.

In addition, these alloys were pulverized to produce magnets and their magnetic properties were studied. Through research, differences in the magnetic properties of the alloys have been identified, and reduced magnetic properties have been identified for alloys with "T" and " _rmax " outside the appropriate ranges.

When comparing alloy properties, the composition of the alloy, especially the RE content, must be fixed. In addition, when the total amount of Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu is 1% by mass or more, the expansion behavior of the RE-rich phase due to hydride formation changes, resulting in a "T" Prolongation and reduction of " _rmax ". Therefore, it must be noted that the ranges of "T" and "rmax" suitable for obtaining excellent magnetic properties vary with the above-mentioned totals.

According to the present invention, the degree of hydrogen detonation of a rare earth magnet alloy ingot can be quantitatively evaluated, and the magnetic properties of a sintered magnet to be produced can be predicted based on the hydrogen absorption behavior during hydrogen detonation for determining the quality of a rare earth magnet alloy ingot. Specifically, the alloy ingot is kept in a reduced-pressure atmosphere; then the ingot is placed in a hydrogen atmosphere; the amount of hydrogen absorbed from the moment when the ingot is placed in the hydrogen atmosphere reaches the maximum possible hydrogen in the rare earth magnet ingot. The time "T" required for absorbing 1% of the amount, and the maximum hydrogen absorbing rate " _rmax " of the rare earth magnet alloy ingot. It can be considered that the prediction is based on the above criteria of time "T" and "rmax" varying with the distribution condition of the RE-rich phase in the rare earth magnet alloy ingot and can be used as an index for accurately predicting the distribution condition of the RE-rich phase.

Example

(Example 1)

Alloy raw materials were provided and mixed so as to obtain the following composition: Nd=30.0% by mass, B=0.98% by mass, Al=0.3% by mass, Cu=0.03% by mass, iron as the balance (hereinafter, the alloy of this composition is referred to as alloy A). The raw material mixture was placed in an alumina crucible and heated in a vacuum chamber, first in a vacuum atmosphere and then in an argon atmosphere, thereby producing a molten alloy. When casting, the molten alloy is poured into a tundish and then poured from the tundish onto a copper roll for rapid cooling. The peripheral speed of the roller was controlled to be 1.2 m/s. The average cooling rate during casting in the range of the temperature of the molten alloy (about 1,400°C) to 1,000°C was calculated according to the following procedure. Specifically, an immersion thermocouple was used to measure the temperature of the molten alloy in the tundish, and a two-color radiation pyrometer was used to measure the temperature of the alloy that had moved from the drop position to a position corresponding to a roll rotation of 60°. The difference between the two measured temperatures was divided by the time for the roll to rotate 60° to calculate the average cooling rate. Through this process, it was found that the average cooling rate in the range from the temperature of the molten alloy to 1,000°C was 800°C/sec. The alloy thus cast is collected in a vessel for containing the alloy. The average cooling rate in the range 800-600°C was obtained by measuring the change in temperature of the alloy remaining in the vessel over time and dividing the measured change in temperature by the time required to change from 800°C to 600°C. The average cooling rate thus obtained was 0.5°C/sec. The average thickness of the resulting cast alloy flakes was 0.23 mm.

Subsequently, the cast alloy thus obtained was subjected to hydrogen explosion. The internal volume of the equipment used for this treatment was 0.010 m ³ . Fragments (1-3 mm) of alloy flakes were introduced into the device and the device was sealed. The inside of the apparatus was adjusted to an atmosphere of 1 x 10 ^-3 Pa, and the chips were kept in this atmosphere for 3 hours. Then, the atmosphere was changed to a hydrogen atmosphere of 140 kPa while the internal temperature was kept at 303K. Measures the change in pressure inside the device. According to the obtained data, the data of the amount of hydrogen absorbed in the alloy at the corresponding time is used to draw a graph, so as to obtain the change of the amount of absorbed hydrogen with time. Calculate the time (hereinafter abbreviated as "T") and the maximum hydrogen absorption rate (hereinafter abbreviated as " _rmax ") required from the start of hydrogen pressurization until the absorbed hydrogen amount reaches 1% of the maximum absorbable hydrogen amount in the alloy. "). From this calculation, it was found that T and _rmax were 1,320 seconds and 4.6×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely the remanence flux density (hereinafter abbreviated as "Br"), coercive force (hereinafter abbreviated as "iHc") and magnetic energy product (hereinafter abbreviated as " _BHmax ") were 1.37T, 812kA/m and 375kJ/m ³ .

(Example 2)

In a similar manner to Example 1, a melt of Alloy A was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the rolls was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to be 800° C./s. The alloy thus cast was collected in a product container and argon was passed through the interior of the container to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,580 seconds and 3.3×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. It was found that the magnetic properties of the magnets, namely Br, iHc and " _BHmax " were 1.35T, 788kA/m and 355kJ/m ³ , respectively.

(Example 3)

In a similar manner to Example 1, a melt of Alloy A was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast is collected in a product container. By cooling in this container, the average cooling rate in the range of 800-600°C was controlled to 0.5°C/sec. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,090 seconds and 5.4×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.38T, 828kA/m and 376kJ/m ³ , respectively.

(Example 4)

In a similar manner to Example 1, a melt of Alloy A was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast was collected in a product container while argon was flowing through the inside of the container in order to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,320 seconds and 4.0×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.36T, 788kA/m and 360kJ/m ³ , respectively.

(comparative example 1)

In a similar manner to Example 1, a melt of Alloy A was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 800° C./s. The alloy thus cast was collected in a product container while helium was flowing through the inside of the container in order to cool the alloy very rapidly. The average cooling rate in the range of 800-600°C was controlled to 15°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 2,540 seconds and 7.6×10 ⁻⁵ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.32T, 716kA/m and 347kJ/m ³ , respectively.

(comparative example 2)

In a similar manner to Example 1, a melt of Alloy A was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.7 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 300° C./s. The alloy thus cast is collected in a product container while maintaining the container under reduced pressure to reduce the cooling rate. Through this process, the average cooling rate in the range of 800-600°C was controlled to 0.2°C/sec. The average thickness of the obtained cast alloy sheet was 0.40 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 170 seconds and 1.9×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.30T, 676kA/m and 337kJ/m ³ , respectively.

(comparative example 3)

In a similar manner to Example 1, a melt of Alloy A was prepared. The molten alloy was poured into a box-shaped mold (thickness: 20 mm) for casting (hinged casting method). The time required to cool the molten alloy from the initial temperature to 1,000°C was measured, and the average cooling rate was calculated to be 8°C/sec. The average cooling rate in the range of 800-600°C is controlled to 0.1°C/sec.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 60 seconds and 2.5×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.25T, 629kA/m and 311kJ/m ³ , respectively.

In relation to the alloy A described above in Examples 1-4 and Comparative Examples 1-3, FIG. 5A is a graph showing the relationship between T and _BHmax , and FIG. 5B is a graph showing the relationship between _rmax and _BHmax . Here, T represents the time required from the moment when the rare earth magnet alloy ingot is placed in the hydrogen atmosphere to when the absorbed hydrogen reaches 1% of the maximum absorbed hydrogen in the alloy ingot, and _rmax represents the maximum hydrogen absorbed rate of the alloy ingot. In FIGS. 5A and 5B , black dots represent the results obtained in Examples 1-4, and white squares represent the results obtained in Comparative Examples 1-3. Figures 5A and 5B show that magnets produced from alloy ingots with T in the range of 100-1,800 sec and r _max in the range of 1.2 x 10 ^-3 -1.5 x 10 ^-2 mass %/sec provide higher magnetic performance than The magnets produced by other alloy ingots are more excellent.

(Example 5)

Alloy raw materials were provided and mixed so as to obtain the following composition: Nd=33.4% by mass, B=1.1% by mass, Al=0.4% by mass, Cu=0.03% by mass, iron as the balance (hereinafter, the alloy of this composition is referred to as alloy B). The raw material mixture was placed in an alumina crucible and heated in a vacuum chamber, first in a vacuum atmosphere and then in an argon atmosphere, thereby producing a molten alloy. When casting, the molten alloy is poured into a tundish and then poured from the tundish onto a copper roll for rapid cooling. The peripheral speed of the roller was controlled to be 1.2 m/s. The average cooling rate was determined in a similar manner to Example 1. Through this process, it was found that the average cooling rate in the range from the temperature of the molten alloy to 1,000°C was 800°C/sec. The alloy thus cast is collected in a container for the alloy. The average cooling rate was found to be 0.5°C/sec. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The same equipment and conditions as in Example 1 were used. Calculations found that T and _rmax were 380 seconds and 6.7×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.27T, 836kA/m and 321kJ/m ³ , respectively.

(Example 6)

In a similar manner to that used in Example 5, a melt of Alloy B was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 800° C./s. The alloy thus cast was collected in a product container while argon was flowing through the inside of the container in order to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 570 seconds and 4.5×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. It was found that the magnetic properties of the magnets, namely Br, iHc and " _BHmax " were 1.25T, 804kA/m and 311kJ/m ³ , respectively.

(Example 7)

In a similar manner to that used in Example 5, a melt of Alloy B was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast was collected in a container. By cooling in the container, the average cooling rate in the range of 800-600°C was controlled to 0.5°C/sec. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 280 seconds and 8.3×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.29T, 867kA/m and 331kJ/m ³ , respectively.

(Embodiment 8)

In a similar manner to that used in Example 5, a melt of Alloy B was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast was collected in a product container while argon was flowing through the inside of the container in order to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 470 seconds and 5.6×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.26T, 796kA/m and 316kJ/m ³ , respectively.

(comparative example 4)

In a similar manner to that used in Example 5, a melt of Alloy B was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 800° C./s. The alloy thus cast is collected in a product container and helium is passed through the inside of the container to cool the alloy very rapidly. The average cooling rate in the range of 800-600°C was controlled to 15°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 960 seconds and 1.3×10 ⁻⁵ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.23T, 788kA/m and 301kJ/m ³ , respectively.

(comparative example 5)

In a similar manner to that used in Example 5, a melt of Alloy B was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.7 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 300° C./s. The alloy thus cast is collected in a product container while maintaining the container under reduced pressure to reduce the cooling rate. Through this process, the average cooling rate in the range of 800-600°C was controlled to 0.2°C/sec. The average thickness of the obtained cast alloy sheet was 0.40 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 90 seconds and 2.3×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.21T, 796kA/m and 286kJ/m ³ , respectively.

(comparative example 6)

In a similar manner to that used in Example 5, a melt of Alloy B was prepared. The molten alloy was poured into a box-shaped mold for casting (thickness: 20 mm). The time required to cool the molten alloy from the initial temperature to 1,000°C was measured, and the average cooling rate was calculated to be 8°C/sec. The average cooling rate in the range of 800-600°C is controlled to 0.1°C/sec.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 40 seconds and 3.1×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. It was found that the magnetic properties of the magnets, namely Br, iHc and " _BHmax " were 1.20T, 716kA/m and 286kJ/m ³ , respectively.

In relation to Alloy B described above in Examples 5-8 and Comparative Examples 4-6, Figure 6A is a graph showing the relationship between T and _BHmax , and Figure 6B is a graph showing the relationship between _rmax and _BHmax . Here, T represents the time required from the moment when the rare earth magnet alloy ingot is placed in the hydrogen atmosphere to when the absorbed hydrogen reaches 1% of the maximum absorbed hydrogen in the alloy ingot, and _rmax represents the maximum hydrogen absorbed rate of the alloy ingot. In FIGS. 6A and 6B , black dots indicate the results obtained in Examples 5-8, and white squares indicate the results obtained in Comparative Examples 4-6.

Figures 6A and 6B show that magnets produced from alloy ingots with T in the range of 100-1,800 seconds and r _max in the range of 1.2×10 ^-3 -1.5×10 ^-2 mass%/second provide magnetic performance ratios compared to The magnets produced by other alloy ingots are more excellent.

(Example 9)

Alloy raw materials were provided and mixed so as to obtain the following composition: Nd=29.2% by mass, B=0.97% by mass, Al=0.4% by mass, Cu=0.03% by mass, iron as the balance (hereinafter, the alloy of this composition is referred to as alloy C). The raw material mixture was placed in an alumina crucible and heated in a vacuum chamber, first in a vacuum atmosphere and then in an argon atmosphere, thereby producing a molten alloy. When casting, the molten alloy is poured into a tundish and then poured from the tundish onto copper rolls for rapid cooling. The peripheral speed of the roller was controlled to be 1.2 m/s. The average cooling rate was determined in a manner similar to that used in Example 1. Through this process, it was found that the average cooling rate in the range from the temperature of the molten alloy to 1,000°C was 800°C/sec. The alloy thus cast is collected in a container for the alloy. The average cooling rate was found to be 0.5°C/sec. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The same equipment and conditions as in Example 1 were used. Calculations found that T and _rmax were 1,410 seconds and 3.8×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.38T, 804kA/m and 379kJ/m ³ , respectively.

(Example 10)

In a similar manner to that used in Example 9, a melt of Alloy C was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 800° C./s. The alloy thus cast was collected in a product container while argon was flowing through the inside of the container in order to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,690 seconds and 2.2×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.35T, 764kA/m and 363kJ/m ³ , respectively.

(Example 11)

In a similar manner to that used in Example 9, a melt of Alloy C was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast was collected in a container. By cooling in the container, the average cooling rate in the range of 800-600°C was controlled to 0.5°C/sec. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,200 seconds and 4.7×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.39T, 820kA/m and 384kJ/m ³ , respectively.

(Example 12)

In a similar manner to that used in Example 9, a melt of Alloy C was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast was collected in a product container while argon was flowing through the inside of the container in order to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,550 seconds and 3.0×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.37T, 772kA/m and 373kJ/m ³ , respectively.

(comparative example 7)

In a similar manner to that used in Example 9, a melt of Alloy C was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 800° C./s. The alloy thus cast was collected in a product container while helium was flowing through the inside of the container in order to cool the alloy very rapidly. The average cooling rate in the range of 800-600°C was controlled to 15°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 3,040 seconds and 8.8×10 ⁻⁵ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.33T, 621kA/m and 352kJ/m ³ , respectively.

(comparative example 8)

In a similar manner to that used in Example 9, a melt of Alloy C was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.7 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 300° C./s. The alloy thus cast is collected in a product container and the container is kept under reduced pressure to reduce the cooling rate. Through this process, the average cooling rate in the range of 800-600°C was controlled to 0.2°C/sec. The average thickness of the obtained cast alloy sheet was 0.40 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 150 seconds and 1.6×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.30T, 637kA/m and 337kJ/m ³ , respectively.

(comparative example 9)

In a similar manner to that used in Example 9, a melt of Alloy C was prepared. The molten alloy was poured into a box-shaped mold for casting (thickness: 20 mm). The time required to cool the molten alloy from the initial temperature to 1,000°C was measured, and the average cooling rate was calculated to be 8°C/sec. The average cooling rate in the range of 800-600°C is controlled to 0.1°C/sec.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 90 seconds and 2.2×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. It was found that the magnetic properties of the magnets, namely Br, iHc and " _BHmax " were 1.24T, 573kA/m and 306kJ/m ³ , respectively.

In relation to Alloy C described in Examples 9-12 and Comparative Examples 7-9 above, FIG. 7A is a graph showing the relationship between T and _BHmax , and FIG. 7B is a graph showing the relationship between _rmax and _BHmax . Here, T represents the time required from the moment when the rare earth magnet alloy ingot is placed in the hydrogen atmosphere to when the absorbed hydrogen reaches 1% of the maximum absorbed hydrogen in the alloy ingot, and _rmax represents the maximum hydrogen absorbed rate of the alloy ingot. In FIGS. 7A and 7B , black dots indicate the results obtained in Examples 9-12, and white squares indicate the results obtained in Comparative Examples 7-9.

Figures 7A and 7B show that magnets produced from alloy ingots with T in the range of 100-1,800 sec and r _max in the range of 1.2 x 10 ^-3 -1.5 x 10 ^-2 mass %/sec provide higher magnetic performance than The magnets produced by other alloy ingots are more excellent.

(Example 13)

Alloy raw materials were supplied and mixed so that the following composition was obtained: Nd = 27.5% by mass, Dy = 2.5% by mass, B = 0.98% by mass, Al = 0.3% by mass, Cu = 0.03% by mass, iron as the balance (hereinafter, the The resulting alloy is referred to as alloy D). The raw material mixture was placed in an alumina crucible and heated in a vacuum chamber, first in a vacuum atmosphere and then in an argon atmosphere, thereby producing a molten alloy. When casting, the molten alloy is poured into a tundish and then poured from the tundish onto a copper roll for rapid cooling. The peripheral speed of the roller was controlled to be 1.2 m/s. The average cooling rate was determined in a similar manner to Example 1. Through this process, it was found that the average cooling rate in the range from the temperature of the molten alloy to 1,000°C was 800°C/sec. The alloy thus cast is collected in a container for the alloy. The average cooling rate was found to be 0.5°C/sec. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The same equipment and conditions as in Example 1 were used. Calculations found that T and _rmax were 1,610 seconds and 4.1×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.32T, 1,289kA/m and 328kJ/m ³ , respectively.

(Example 14)

In a similar manner to that used in Example 13, a melt of Alloy D was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 800° C./s. The alloy thus cast was collected in a product container while argon was flowing through the inside of the container in order to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,900 seconds and 2.8×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.30T, 1,265kA/m and 318kJ/m ³ , respectively.

(Example 15)

In a similar manner to that used in Example 13, a melt of Alloy D was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast was collected in a container. By cooling in the container, the average cooling rate in the range of 800-600°C was controlled to 0.5°C/sec. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,390 seconds and 4.9×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.33T, 1,305kA/m and 333kJ/m ³ , respectively.

(Example 16)

In a similar manner to that used in Example 13, a melt of Alloy D was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast was collected in a product container while argon was flowing through the inside of the container in order to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,630 seconds and 3.5×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.31T, 1,273kA/m and 323kJ/m ³ , respectively.

(comparative example 10)

In a similar manner to that used in Example 13, a melt of Alloy D was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 800° C./s. The alloy thus cast was collected in a product container while helium was flowing through the inside of the container in order to cool the alloy very rapidly. The average cooling rate in the range of 800-600°C was controlled to 15°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 3,030 seconds and 6.4×10 ⁻⁵ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.27T, 1,218kA/m and 304kJ/m ³ , respectively.

(comparative example 11)

In a similar manner to that used in Example 13, a melt of Alloy D was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.7 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 300° C./s. The alloy thus cast is collected in a product container and the container is kept under reduced pressure to reduce the cooling rate. Through this process, the average cooling rate in the range of 800-600°C was controlled to 0.2°C/sec. The average thickness of the obtained cast alloy sheet was 0.40 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 180 seconds and 1.4×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnets, namely Br, iHc and " _BHmax " were 1.25T, 1,202kA/m and 295kJ/m ³ , respectively.

(comparative example 12)

In a similar manner to that used in Example 13, a melt of Alloy D was prepared. The molten alloy was poured into a box-shaped mold for casting (thickness: 20 mm). The time required to cool the molten alloy from the initial temperature to 1,000°C was measured, and the average cooling rate was calculated to be 8°C/sec. The average cooling rate in the range of 800-600°C is controlled to 0.1°C/sec.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 80 seconds and 2.1×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.20T, 1,162kA/m and 273kJ/m ³ , respectively.

In relation to Alloy D described above in Examples 13-16 and Comparative Examples 10-12, FIG. 8A is a graph showing the relationship between T and _BHmax , and FIG. 8B is a graph showing the relationship between _rmax and _BHmax . picture. Here, T represents the time required from the moment when the rare earth magnet alloy ingot is placed in the hydrogen atmosphere to when the absorbed hydrogen reaches 1% of the maximum absorbed hydrogen in the alloy ingot, and _rmax represents the maximum hydrogen absorbed rate of the alloy ingot. In FIGS. 8A and 8B , black dots indicate the results obtained in Examples 13-16, and white squares indicate the results obtained in Comparative Examples 10-12.

Figures 8A and 8B show that magnets produced from alloy ingots with T in the range of 200-2,400 seconds and _rmax in the range of 1.0×10 ^-3 -1.2×10 ^-2 % mass/second provide higher magnetic performance than The magnets produced by other alloy ingots are more excellent.

(Example 17)

Alloy raw materials were supplied and mixed so as to obtain the following composition: Nd = 31.9 mass%, Dy = 1.5 mass%, B = 1.1 mass%, Al = 0.4 mass%, Cu = 0.03 mass%, iron as the balance (hereinafter, the The resulting alloy is called Alloy E). The raw material mixture was placed in an alumina crucible and heated in a vacuum chamber, first in a vacuum atmosphere and then in an argon atmosphere, thereby producing a molten alloy. When casting, the molten alloy is poured into a tundish and then poured from the tundish onto a copper roll for rapid cooling. The peripheral speed of the roller was controlled to be 1.2 m/s. The average cooling rate was determined in a manner similar to that used in Example 1. Through this process, it was found that the average cooling rate in the range from the temperature of the molten alloy to 1,000°C was 800°C/sec. The alloy thus cast is collected in a container for the alloy. The average cooling rate was found to be 0.5°C/sec. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The same equipment and conditions as in Example 1 were used. Calculations found that T and _rmax were 700 seconds and 6.2×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.25T, 1,074kA/m and 292kJ/m ³ , respectively.

(Example 18)

In a similar manner to that used in Example 17, a melt of Alloy E was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 800° C./s. The alloy thus cast was collected in a product container while argon was flowing through the inside of the container in order to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 880 seconds and 4.2×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnets, namely Br, iHc and " _BHmax " were 1.22T, 1,058kA/m and 279kJ/m ³ , respectively.

(Example 19)

In a similar manner to that used in Example 17, a melt of Alloy E was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast was collected in a container. By cooling in the container, the average cooling rate in the range of 800-600°C was controlled to 0.5°C/sec. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 590 seconds and 8.0×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.27T, 1,114kA/m and 302kJ/m ³ , respectively.

(Example 20)

In a similar manner to that used in Example 17, a melt of Alloy E was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast was collected in a product container and argon was passed through the inside of the container in order to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 810 seconds and 5.3×10 ⁻⁴ mass %/second, respectively.

$131-1

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.23T, 1,074kA/m and 283kJ/m ³ , respectively.

(comparative example 13)

In a similar manner to that used in Example 17, a melt of Alloy E was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 800° C./s. The alloy thus cast was collected in a product container while helium was flowing through the inside of the container in order to cool the alloy very rapidly. The average cooling rate in the range of 800-600°C was controlled to 15°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,430 seconds and 1.1×10 ⁻⁵ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.20T, 1,035kA/m and 270kJ/m ³ , respectively.

(comparative example 14)

In a similar manner to that used in Example 17, a melt of Alloy E was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.7 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 300° C./s. The alloy thus cast is collected in a product container and the container is kept under reduced pressure to reduce the cooling rate. Through this process, the average cooling rate in the range of 800-600°C was controlled to 0.2°C/sec. The average thickness of the obtained cast alloy sheet was 0.40 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 150 seconds and 2.0×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnets, namely Br, iHc and " _BHmax " were 1.18T, 1,042kA/m and 261kJ/m ³ , respectively.

(comparative example 15)

In a similar manner to that used in Example 17, a melt of Alloy E was prepared. The molten alloy was poured into a box-shaped mold for casting (thickness: 20 mm). The time required to cool the molten alloy from the initial temperature to 1,000°C was measured, and the average cooling rate was calculated to be 8°C/sec. The average cooling rate in the range of 800-600°C is controlled to 0.1°C/sec.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 50 seconds and 2.9×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. It was found that the magnetic properties of the magnets, namely Br, iHc and " _BHmax " were 1.16T, 955kA/m and 252kJ/m ³ , respectively.

In relation to Alloy E described above in Examples 17-20 and Comparative Examples 13-15, FIG. 9A is a graph showing the relationship between T and _BHmax , and FIG. 9B is a graph showing the relationship between _rmax and _BHmax . Here, T represents the time required from the moment when the rare earth magnet alloy ingot is placed in the hydrogen atmosphere to when the absorbed hydrogen reaches 1% of the maximum absorbed hydrogen in the alloy ingot, and _rmax represents the maximum hydrogen absorbed rate of the alloy ingot. In FIGS. 9A and 9B , black dots represent the results obtained in Examples 17-20, and white squares represent the results obtained in Comparative Examples 13-15.

$138-1

Figures 9A and 9B show that magnets produced from alloy ingots with T in the range of 200-2,400 sec and r _max in the range of 1.0 x 10 ^-3 -1.2 x 10 ^-2 mass %/sec provide higher magnetic performance than The magnets produced by other alloy ingots are more excellent.

(Example 21)

Alloy raw materials were supplied and mixed so that the following composition was obtained: Nd = 25.2% by mass, Dy = 4.0% by mass, B = 0.97% by mass, Al = 0.3% by mass, Cu = 0.03% by mass, iron as the balance (hereinafter, the The resulting alloy is called Alloy F). The raw material mixture was placed in an alumina crucible and heated in a vacuum chamber, first in a vacuum atmosphere and then in an argon atmosphere, thereby producing a molten alloy. When casting, the molten alloy is poured into a tundish and then poured from the tundish onto a copper roll for rapid cooling. The peripheral speed of the roller was controlled to be 1.2 m/s. The average cooling rate was determined in a manner similar to that used in Example 1. Through this process, it was found that the average cooling rate in the range from the temperature of the molten alloy to 1,000°C was 800°C/sec. The alloy thus cast is collected in a container for the alloy. The average cooling rate was found to be 0.5°C/sec. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The same equipment and conditions as in Example 1 were used. Calculations found that T and _rmax were 1,750 seconds and 3.2×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.30T, 1,560kA/m and 325kJ/m ³ , respectively.

(Example 22)

In a similar manner to that used in Example 21, a melt of Alloy F was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 800° C./s. The alloy thus cast was collected in a product container while argon was flowing through the inside of the container in order to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,990 seconds and 1.7×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.27T, 1,520kA/m and 305kJ/m ³ , respectively.

(Example 23)

In a similar manner to that used in Example 21, a melt of Alloy F was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast was collected in a container. By cooling in the container, the average cooling rate in the range of 800-600°C was controlled to 0.5°C/sec. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,550 seconds and 4.1×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.31T, 1,576kA/m and 325kJ/m ³ , respectively.

(Example 24)

In a similar manner to that used in Example 21, a melt of Alloy F was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.8 m/s, so that the average cooling speed in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 400° C./s. The alloy thus cast was collected in a product container while argon was flowing through the inside of the container in order to cool the alloy more rapidly. The average cooling rate in the range of 800-600°C was controlled to 1.2°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.35 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 1,780 seconds and 2.8×10 ⁻⁴ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.28T, 1,528kA/m and 310kJ/m ³ , respectively.

(comparative example 16)

In a similar manner to that used in Example 21, a melt of Alloy F was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 1.2 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 800° C./s. The alloy thus cast was collected in a product container while helium was flowing through the inside of the container in order to cool the alloy very rapidly. The average cooling rate in the range of 800-600°C was controlled to 15°C/sec by gas flow. The average thickness of the obtained cast alloy sheet was 0.23 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 3,360 seconds and 7.6×10 ⁻⁵ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.25T, 1,393kA/m and 294kJ/m ³ , respectively.

(comparative example 17)

In a similar manner to that used in Example 21, a melt of Alloy F was prepared and cast. For casting, the molten alloy is poured into a tundish and from the tundish onto rolls. The peripheral speed of the roll was controlled to be 0.7 m/s, so that the average cooling rate in the range of the temperature of the molten alloy to 1,000° C. was adjusted to 300° C./s. The alloy thus cast is collected in a product container and the container is kept under reduced pressure to reduce the cooling rate. Through this process, the average cooling rate in the range of 800-600°C was controlled to 0.2°C/sec. The average thickness of the obtained cast alloy sheet was 0.40 mm.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 180 seconds and 1.3×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnet, namely Br, iHc and " _BHmax " were 1.22T, 1,377kA/m and 280kJ/m ³ , respectively.

(comparative example 18)

In a similar manner to that used in Example 21, a melt of Alloy F was prepared. The molten alloy was poured into a box-shaped mold for casting (thickness: 20 mm). The time required to cool the molten alloy from the initial temperature to 1,000°C was measured, and the average cooling rate was calculated to be 8°C/sec. The average cooling rate in the range of 800-600°C is controlled to 0.1°C/sec.

Then, the cast alloy thus obtained was subjected to hydrogen explosion. The equipment and conditions for this treatment were the same as in Example 1. Calculations found that T and _rmax were 120 seconds and 1.8×10 ⁻³ mass %/second, respectively.

The alloy thus treated was further crushed into a powder having an average particle size of 3.2 microns as measured by a Fischer sieve sizer. The powder is shaped in a magnetic field, and the resulting compact is sintered to produce a sintered magnet. The study found that the magnetic properties of the magnets, namely Br, iHc and " _BHmax " were 1.16T, 1,337kA/m and 252kJ/m ³ , respectively.

In relation to alloy F described in Examples 21-24 and Comparative Examples 16-18 above, FIG. 10A is a graph showing the relationship between T and _BHmax , and FIG. 10B is a graph showing the relationship between _rmax and _BHmax . Here, T represents the time required from the moment when the rare earth magnet alloy ingot is placed in the hydrogen atmosphere to when the absorbed hydrogen reaches 1% of the maximum absorbed hydrogen in the alloy ingot, and _rmax represents the maximum hydrogen absorbed rate of the alloy ingot. In FIGS. 10A and 10B , black dots represent the results obtained in Examples 21-24, and white squares represent the results obtained in Comparative Examples 16-18.

Figures 10A and 10B show that magnets produced from alloy ingots with T in the range of 200-2,400 seconds and r _max in the range of 1.0×10 ^-3 -1.2×10 ^-2 mass%/second provide magnetic performance ratios compared to The magnets produced by other alloy ingots are more excellent.

Table 1 shows the compositions of the rare earth magnet alloys in the above-mentioned Examples 1-24 and Comparative Examples 1-18.

Table 1 Nd Dy B al Cu Fe Alloy A 30.0 - 0.98 0.3 0.03 68.69 Alloy B 33.4 - 1.10 0.4 0.03 65.07 Alloy C 29.2 - 0.97 0.3 0.03 69.5 Alloy D 27.5 2.5 0.98 0.3 0.03 68.69 Alloy E 31.9 1.5 1.10 0.4 0.03 65.07 Alloy F 25.2 4.0 0.97 0.3 0.03 69.5

Table 2-1 to Table 2-3 show the characteristics of alloys A, B and C studied in Examples 1-12 and Comparative Examples 1-9.

table 2-1 Alloy composition casting method Peripheral speed of roller m/s Cooling rate °C/s Average thickness mm T seconds _rMax mass%/sec BrT iHckA/m BH _max kJ/m ³ 1000-mp 800-600 Example 1 A SC 1.2 800 0.5 0.23 1320 4.60E-04 1.37 811.69 374.81 Example 2 A SC 1.2 800 1.2 0.23 1580 3.30E-04 1.35 787.82 354.92 Example 3 A SC 0.8 400 0.5 0.35 1090 5.40E-04 1.38 827.61 376.40 Example 4 A SC 0.8 400 1.2 0.35 1320 4.00E-04 1.36 787.82 359.69 Comparative example 1 A SC 1.2 800 15 0.23 2540 7.60E-05 1.32 716.20 346.96 Comparative example 2 A SC 0.7 300 0.2 0.40 170 1.90E-03 1.30 676.41 336.61 Comparative example 3 A BM - - - - 60 2.50E-03 1.25 628.66 311.15

Table 2-2 Alloy composition casting method Peripheral speed of roller m/s Cooling rate °C/s Average thickness mm T seconds _rMax mass%/sec BrT iHckA/m BH _max kJ/m ³ 1000-mp 800-600 Example 5 B SC 1.2 800 0.5 0.23 380 6.70E-04 1.27 835.56 320.70 Example 6 B SC 1.2 800 1.2 0.23 570 4.50E-04 1.25 803.73 311.15 Example 7 B SC 0.8 400 0.5 0.35 280 8.30E-04 1.29 867.39 331.04 Example 8 B SC 0.8 400 1.2 0.35 470 5.60E-04 1.26 795.77 315.92 Comparative example 4 B SC 1.2 800 15 0.23 960 1.30E-05 1.23 787.82 300.80 Comparative example 5 B SC 0.7 300 0.2 0.40 90 2.30E-03 1.21 795.77 291.25 Comparative example 6 B BM - - - - 40 3.10E-03 1.20 716.20 286.48

Table 2-3 Alloy composition casting method Peripheral speed of roller m/s Cooling rate °C/s Average thickness mm T seconds _rMax mass%/sec BrT iHckA/m BH _max kJ/m ³ 1000-mp 800-600 Example 9 C SC 1.2 800 0.5 0.23 1410 3.80E-04 1.38 803.73 378.79 Example 10 C SC 1.2 800 1.2 0.23 1690 2.20E-04 1.35 763.94 362.87 Example 11 C SC 0.8 400 0.5 0.35 1200 4.70E-04 1.39 819.65 384.36 Example 12 C SC 0.8 400 1.2 0.35 1550 3.00E-04 1.37 771.90 373.22 Comparative example 7 C SC 1.2 800 15 0.23 3040 8.80E-05 1.33 620.70 351.73 Comparative example 8 C SC 0.7 300 0.2 0.40 150 1.60E-03 1.30 636.62 336.61 Comparative example 9 C BM - - - - 90 2.20E-03 1.24 572.96 305.58

Table 3-1-3-3 shows the properties of alloys D, E and F investigated in Examples 13-24 and Comparative Examples 10-18.

Table 3-1 Alloy composition casting method Peripheral speed of roller m/s Cooling rate °C/s Average thickness mm T seconds _rMax mass%/sec BrT iHckA/m BH _max kJ/m ³ 1000-mp 800-600 Example 13 D. SC 1.2 800 0.5 0.23 1610 4.10E-04 1.32 1,289.16 327.86 Example 14 D. SC 1.2 800 1.2 0.23 1900 2.80E-04 1.30 1,265.28 318.31 Example 15 D. SC 0.8 400 0.5 0.35 1390 4.90E-04 1.33 1,305.07 332.63 Example 16 D. SC 0.8 400 1.2 0.35 1630 3.50E-04 1.31 1,273.24 323.08 Comparative example 10 D. SC 1.2 800 15 0.23 3030 6.40E-05 1.27 1,217.54 303.99 Comparative example 11 D. SC 0.7 300 0.2 0.40 180 1.40E-03 1.25 1,201.62 295.23 Comparative example 12 D. BM - - - - 80 2.10E-03 1.20 1,161.83 272.95

Table 3-2 Alloy composition casting method Peripheral speed of roller m/s Cooling rate °C/s Average thickness mm T seconds _rMax mass%/sec BrT iHckA/m BH _max kJ/m ³ 1000-mp 800-600 Example 17 E. SC 1.2 800 0.5 0.23 700 6.20E-04 1.25 1,074.30 292.05 Example 18 E. SC 1.2 800 1.2 0.23 880 4.20E-04 1.22 1,058.38 278.52 Example 19 E. SC 0.8 400 0.5 0.35 590 8.00E-04 1.27 1,114.08 301.60 Example 20 E. SC 0.8 400 1.2 0.35 810 5.30E-04 1.23 1,074.30 283.30 Comparative example 13 E. SC 1.2 800 15 0.23 1430 1.10E-05 1.20 1,034.51 269.77 Comparative example 14 E. SC 0.7 300 0.2 0.40 150 2.00E-03 1.18 1,042.46 261.01 Comparative example 15 E. BM - - - - 50 2.90E-03 1.16 954.93 252.26

Table 3-3 Alloy composition casting method Peripheral speed of roller m/s Cooling rate °C/s Average thickness mm T seconds _rMax mass%/sec BrT iHckA/m BH _max kJ/m ³ 1000-mp 800-600 Example 21 f SC 1.2 800 0.5 0.23 1750 3.20E-04 1.30 1,559.72 324.68 Example 22 f SC 1.2 800 1.2 0.23 1990 1.70E-04 1.27 1,519.93 304.78 Example 23 f SC 0.8 400 0.5 0.35 1550 4.10E-04 1.31 1,575.63 324.68 Example 24 f SC 0.8 400 1.2 0.35 1780 2.80E-04 1.28 1,527.89 309.56 Comparative example 16 f SC 1.2 800 15 0.23 3360 7.60E-05 1.25 1,392.61 294.44 Comparative example 17 f SC 0.7 300 0.2 0.40 180 1.30E-03 1.22 1,376.69 280.11 Comparative example 18 f BM - - - - 120 1.80E-03 1.16 1,336.90 252.26

Industrial Applicability

Compared with traditional methods of evaluating the metallographic structure of alloys based only on cross-sectional photographs, such as using microscopic photographs of rare earth magnet alloy ingots and image processing of the photographs to determine the spacing between R-rich phases, the present invention uses a new method, Including evaluating the metallographic structure of rare earth magnet alloy ingots based on hydrogen absorption properties, compared with traditional methods, the method of the present invention can be used to determine the quality of a large number of alloy ingots, and can evaluate not only a part of the alloy, but also the overall alloy. Therefore, by evaluating the rare earth magnet alloy ingot itself, the particle size distribution of the alloy powder and the magnetic properties of the sintered magnet produced from this powder after completion of the hydrogen burst can be accurately predicted, and the quality of the ingot can be determined.

The method of the present invention for determining rare earth magnet alloy ingots determines the conditions for the hydrogen absorption behavior of rare earth magnet alloy ingots that can be used to produce alloy powders suitable for making magnets with more superior properties, and is consistent with methods that include evaluating RE-rich phases based on cross-sectional photographs Compared with traditional methods of distribution, by evaluating the rare earth magnet alloy ingot itself, the quality and magnetic properties of rare earth magnet alloy powder can be predicted more accurately. Therefore, the quality of the rare earth magnet alloy ingot can be determined by evaluating the ingot itself. Traditionally, the quality of a rare earth magnet alloy ingot cannot be evaluated until the final sintered magnet has been produced. However, according to the present invention, the quality of the ingot can be determined by evaluating the ingot itself, thereby shortening the time required for the production step of the rare earth magnet alloy ingot, resulting in cost reduction.

In addition, rare earth magnets produced from qualified rare earth magnet alloys based on the method for determining rare earth magnet alloy ingots of the present invention exhibit excellent magnetic properties.

Claims (12)

1. A method for assessing the quality of a rare earth magnet alloy ingot, the method comprising the steps of: keeping the rare earth magnet alloy ingot under a reduced pressure atmosphere, then placing the rare earth magnet alloy ingot in a hydrogen atmosphere, and The hydrogen absorption behavior of the ingot is measured while the rare earth magnet alloy ingot is kept in a hydrogen atmosphere, wherein the rare earth magnet alloy is determined by measuring the change in the amount of hydrogen absorbed by the ingot over time since the moment when the ingot is put into the hydrogen atmosphere Hydrogen absorption behavior of ingots, wherein rare earth magnet alloy ingots contain the following composition: at least one element selected from Y and lanthanides La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb The metal elements RE of Lu and Lu are 27-34% by mass; boron is 0.7-1.4% by mass; and the remainder is transition metal-containing metal TM including Fe as an essential component. 2. The method for evaluating the quality of a rare earth magnet alloy ingot according to claim 1, wherein the rare earth magnet alloy ingot is roughly crushed and kept under a reduced pressure atmosphere. 3. The method for evaluating the quality of a rare earth magnet alloy ingot according to claim 1, wherein the rare earth magnet alloy ingot is kept under a reduced-pressure atmosphere at a pressure of 8×10 ⁻⁴ to 1×10 ⁻² Pa. 4. The method for evaluating the quality of a rare earth magnet alloy ingot according to claim 1, wherein the rare earth magnet alloy ingot is placed in a hydrogen atmosphere at a temperature of 273-373K. 5. The method for evaluating the quality of a rare earth magnet alloy ingot according to claim 1, wherein the rare earth magnet alloy ingot is placed in a hydrogen atmosphere at a pressure of 101-160 kPa. 6. The method for evaluating the quality of a rare earth magnet alloy ingot according to claim 1, wherein the rare earth magnet alloy ingot is produced by a rapid cooling casting method. 7. The method for evaluating the quality of a rare earth magnet alloy ingot according to claim 6, wherein the rapid cooling casting method is a strip casting method. 8. The method for assessing the quality of a rare earth magnet alloy ingot according to claim 1, wherein the maximum amount of hydrogen absorbable in the rare earth magnet ingot is reached by measuring the moment when the rare earth magnet alloy ingot is placed in a hydrogen atmosphere to the amount of absorbed hydrogen 1% of the time required to determine the hydrogen absorption behavior of the rare earth magnet alloy ingot. 9. The method for evaluating the quality of a rare earth magnet alloy ingot according to claim 1, wherein the rare earth magnet alloy ingot is kept under a reduced pressure atmosphere of 8×10 ⁻⁴ to 1×10 ⁻² Pa, and wherein the rare earth magnet alloy The magnet alloy ingot is placed in a hydrogen atmosphere with a temperature of 283-313K and a pressure of 101-160kPa, and also includes the process from when the ingot is placed in a hydrogen atmosphere to when the amount of hydrogen absorbed reaches the maximum hydrogen absorption amount of the rare earth magnet alloy ingot. 1% and the maximum hydrogen absorption rate of the rare earth magnet alloy ingot to measure the hydrogen absorption behavior of the ingot, wherein the time is 200-2,400 seconds and the maximum absorption rate is 1.0×10 ^-4 -1.2×10 ^-3 mass %/sec. 10. according to the method for assessing the quality of rare earth magnet alloy ingot of claim 1, wherein, the total amount of Eu, Gd, Tb, Dy, Ho, Yb and Lu in described rare earth magnet alloy ingot is limited to less than 1 mass%, will The rare earth magnet alloy ingot is kept under a reduced pressure atmosphere of 8×10 ^-4 -1×10 ^-2 Pa, and wherein the rare earth magnet alloy ingot is placed in a hydrogen gas at a temperature of 283-313K and a pressure of 101-160kPa The atmosphere also includes the time required for the ingot to be placed in a hydrogen atmosphere until the amount of absorbed hydrogen reaches 1% of the maximum absorbed hydrogen of the rare earth magnet alloy ingot and the maximum absorbed hydrogen of the rare earth magnet alloy ingot The hydrogen absorption behavior of the ingot is determined by measuring the hydrogen absorption rate, wherein the time is 100-1,800 seconds, and the maximum absorption rate is 1.2×10 ^-4 -1.5×10 ^-3 mass %/second. 11. A method for producing a rare earth magnet alloy ingot, comprising the steps of: using the method for assessing the quality of a rare earth magnet alloy ingot according to any one of claims 1-10 to assess the quality of a rare earth magnet alloy ingot, in the magnet production step Rare earth magnet alloy ingots of unsatisfactory quality were removed, and the rare earth magnet alloy ingots were pulverized into powder, molded and sintered. 12. The method for producing a rare earth magnet alloy ingot according to claim 11, further comprising the step of producing a rare earth magnet alloy ingot by a rapid cooling casting method, wherein the average cooling rate is controlled to be 300° C./second in the range from the temperature of the molten alloy to 1000° C. Or greater, in the range of 800-600 ° C to control 0.5-10 ° C / sec.

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