JP2009068111A - Material alloy for rare earth sintered magnet and alloy powder for rare earth sintered magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material alloy for a R<SB>2</SB>Fe<SB>14</SB>B rare earth magnet excellent in magnetic properties, and an alloy powder thereof. <P>SOLUTION: The material alloy for the rare earth sintered magnet is an alloy having a composition composed of 27.6-33.0 mass% of R including neodymium or including neodymium and at least one element chosen from the group consisting of rare earth metal elements including yttrium but not including neodymium, 0.94-1.30 mass% of boron and the balance M containing iron. The average distance between R-rich phases in the alloy is 3-12 μm; the value obtained by dividing the standard deviation of the R-rich phase distance with the average distance between the R-rich phases is ≤0.25, and the volume percentage of a R<SB>2</SB>Fe<SB>14</SB>B main phase is ≥88 vol.%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention, rare earth metals, about material alloy powder for iron and boron as an essential component R ₂ Fe ₁₄ B based rare-earth sintered material alloy及 beauty rare earth sintered magnet for a magnet.

As recent electronic devices are reduced in size and weight, there is a demand for higher magnetic properties of magnets used in these devices. In particular, R ₂ Fe ₁₄ B sintered magnets with high magnetic flux density are being actively developed. Generally, an R ₂ Fe ₁₄ B sintered magnet is obtained by magnetic field forming, sintering, and aging treatment of a magnet raw material alloy obtained by melting, casting, and grinding a raw material. During sintering, a phase containing a large amount of a rare earth metal having a relatively low melting point (hereinafter referred to as “R-rich phase”) melts to become a liquid phase, and an R ₂ Fe ₁₄ B phase (hereinafter referred to as “2-14-1 system main phase”). It works to fill the space between the crystal grains made of, improves the sinterability, and contributes to higher density of the sintered body. Further, after solidification, the non-magnetic R-rich phase covers particles composed of the 2-14-1 main phase of the ferromagnetic material and magnetically insulates the 2-14-1 main phase to increase the coercive force. Play a role.
As a raw material alloy suitable for an R ₂ Fe ₁₄ B-based sintered magnet, an alloy having a structure in which R-rich phases prepared by a rapid solidification method are finely dispersed is used. In this alloy, the R-rich phase is finely dispersed, so the grindability is good. As a result, after sintering, the particles composed of the 2-14-1 main phase are uniformly coated with the R-rich phase. The magnetic characteristics are improved (see, for example, Patent Document 1). In addition, the microscopic analysis of the slab crystal structure shows that the fine dendritic or columnar crystals present in the slab have an effect on the oxidation of the magnet powder accompanying the pulverization during pulverization and the decrease in the degree of orientation of the sintered magnet. In order to reduce the fine dendritic or columnar crystals, there is known a method for producing a magnet powder that controls the melt temperature, primary cooling rate, and secondary cooling rate in the rapid solidification method (see, for example, Patent Document 2). ). Furthermore, it is assumed that the residual magnetization increases by increasing the volume fraction of the 2-14-1 main phase and reducing the interval between the R-rich phases, and the primary cooling rate, secondary cooling rate or heat treatment in the rapid solidification method A method for producing a magnet powder for controlling temperature is known (see, for example, Patent Documents 3 to 5).
However, although the magnetic characteristics have been improved by these techniques, it is not yet sufficient.
Japanese Patent No. 2,639,609 Japanese Patent Laid-Open No. 8-269634 Japanese Patent No. 3267133 JP-A-10-36949 JP 2002-266006 A

An object of the present invention is to provide a raw material alloy for R ₂ Fe ₁₄ B-based rare earth sintered magnets having excellent magnetic properties, and an alloy powder thereof .

In order to solve the above problems, the present inventor has examined the relationship between the structure and magnetic properties of the raw material alloy for R ₂ Fe ₁₄ B magnets, and as a result, the R-rich phase in the raw alloy for R ₂ Fe ₁₄ B magnets. Control of the mean spacing of R2 and the standard deviation of R-rich phase spacing, the volume ratio of the 2-14-1 main phase, and the particle size distribution after finely pulverizing the R ₂ Fe ₁₄ B magnet raw material alloy As a result, it was found that the remanent magnetization and coercivity of the sintered magnet produced using these raw material alloys for R ₂ Fe ₁₄ B magnets were improved. Further, the present inventor has found that the above-mentioned raw material alloy for R ₂ Fe ₁₄ B-based magnets can be obtained by controlling the cooling rate, slab holding temperature, etc. in the strip casting method, and has completed the present invention.

That is, according to the present invention, R27.6-33.0% by mass consisting of neodymium, or at least one selected from the group consisting of neodymium and a rare earth metal element containing yttrium and not containing neodymium, boron, An alloy having a composition of 0.94 to 1.30% by mass and the balance M containing iron,
The R-rich phase has an average interval of 3 to 12 μm, the standard deviation of the R-rich phase interval divided by the average interval of the R-rich phase is 0.25 or less, and the R ₂ Fe ₁₄ B system A raw material alloy for a rare earth sintered magnet is provided in which the volume ratio of the main phase is 88% by volume or more.
According to the present invention, the alloy powder obtained by pulverizing the alloy for rare earth sintered magnet raw material to an average particle size of 3 to 7 μm,
A raw material alloy for rare earth sintered magnet, wherein the alloy powder has a particle size distribution of 1.90 or more and a particle size characteristic number of 4.0 to 10.0 when the Rosin-Ramller distribution is applied. A powder is provided .

The raw material alloy for rare earth sintered magnets of the present invention has an excellent R-rich phase interval, volume ratio, constituent phase ratio, and optimal 2-14-1 main phase shape, and therefore has excellent magnetic properties .

The present invention will be described in detail below.
The raw material alloy for rare earth sintered magnets of the present invention is composed of neodymium, or R composed of at least one selected from the group consisting of neodymium and rare earth metal elements containing yttrium and not containing neodymium, boron, and iron. It has the composition which made the remainder M to contain into a specific ratio.
R other than the neodymium is not particularly limited, and lanthanum, cerium, praseodymium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, ytterbium, or a mixture of two or more of these is preferable. The content ratio of R is 27.6 to 33.0% by mass. When R is less than 27.6% by mass, the liquid phase amount necessary for densification of the sintered body is insufficient, the density of the sintered body is lowered, and the magnetic properties are lowered. On the other hand, if it exceeds 33.0% by mass, the proportion of the R-rich phase inside the sintered body increases, and the corrosion resistance decreases. Moreover, since the volume ratio of the 2-14-1 main phase is inevitably reduced, the residual magnetic flux density Br decreases. Preferably, R contains at least one selected from the group consisting of gadolinium, terbium, dysprosium, holmium, erbium and ytterbium in addition to neodymium. These heavy rare earth elements mainly improve the coercive force among the magnet characteristics. Of these heavy rare earth elements, terbium exhibits the greatest effect but is expensive, and it is preferable to use dysprosium alone or in combination with gadolinium, terbium, and holmium in consideration of cost and effects.
The content of these heavy rare earth elements is usually 0.2 to 15% by mass, preferably 1 to 15% by mass, and more preferably 3 to 15% by mass. When the content ratio is more than 15% by mass, the cost becomes high, which is not preferable.
The boron content is 0.94 to 1.30% by mass. If boron is less than 0.94% by mass, the ratio of the 2-14-1 main phase decreases and the residual magnetic flux density Br decreases. If it exceeds 1.30% by mass, the ratio of the B-rich phase increases. In addition, both magnetic properties and corrosion resistance are reduced.

The balance M contains iron, and the content ratio of iron in the balance M is preferably 50% by mass or more, and more preferably 60% by mass or more. The balance M may contain at least one selected from the group consisting of transition metals other than iron, silicon and carbon, if necessary, and also contains inevitable impurities in industrial production such as oxygen and nitrogen. You can leave.
The transition metal other than iron is not particularly limited. For example, at least one selected from the group consisting of cobalt, aluminum, chromium, titanium, vanadium, manganese, magnesium, copper, tin, tungsten, niobium, and gallium is preferable. .

In the raw material alloy for rare earth sintered magnet of the present invention, the average interval of R-rich phase is 3 to 12 μm, preferably 4 to 6 μm, and the standard deviation of R-rich phase interval is divided by the average interval of R-rich phase. The value is 0.25 or less, preferably 0.2 or less. The smaller the value obtained by dividing the standard deviation of the R-rich phase interval by the average interval of the R-rich phase, the smaller the variation in the slab structure.
The average interval of the R-rich phase and the standard deviation of the R-rich phase interval can be determined by the following method.
First, a cross-sectional structure photograph in the thickness direction of the strip cast slab was taken with an optical microscope, a line segment corresponding to 400 μm was drawn in the cross-sectional width direction at the central position of the cross section in the thickness direction, and R-rich crossing the line segment. Count the number of phases and divide the length of the line drawn in the cross-sectional width direction by the number of R-rich phases. Values were obtained in the same manner for 20 or more slabs, and the average value thereof was taken as the average interval of the R-rich phase. Also, the standard deviation of the R-rich phase interval is calculated by drawing a line segment corresponding to 50 μm in the cross-sectional width direction at the center position of the cross-section in the thickness direction of the slab, counting the number of R-rich phases crossing the line segment, Divide the length of the line drawn in the width direction by the number of R-rich phases. Five points for one slab and an average interval for 20 slabs are obtained, and a standard deviation is calculated from the data.
When the average interval of the R-rich phase is 3 to 12 μm and the value obtained by dividing the standard deviation of the R-rich phase interval by the average interval is 0.25 or less, when pulverizing to an average particle size of 3 to 7 μm, Since the ratio of the single particle containing a phase increases, the R-rich phase which becomes a liquid phase at the time of sintering spreads effectively between 2-14-1 system main phase particles, and sinterability improves. Further, since the contact between the 2-14-1 main phase particles is divided, abnormal grain growth is suppressed and the coercive force is improved. When the average interval between R-rich phases is less than 3 μm, the proportion of crystal grains having different orientations in a single particle increases, the residual magnetic flux density decreases, and when the average interval between R-rich phases exceeds 12 μm, The proportion of single particles in which no R-rich phase is present increases, and both sinterability and coercive force decrease. In addition, even when the average interval of the R-rich phase is 3 to 12 μm, when the value obtained by dividing the standard deviation of the R-rich phase interval by the average interval of the R-rich phase is larger than 0.25, The particle size distribution becomes broad and the coercive force and the maximum energy product decrease.

In the raw material alloy for rare earth sintered magnet of the present invention, the volume ratio of the 2-14-1 main phase is 88% by volume or more, preferably 90% by volume or more. The volume ratio of the 2-14-1 main phase was an area ratio determined by image analysis of the EPMA Compo image of the cross-sectional structure in the thickness direction of the strip cast slab. When the volume ratio of the 2-14-1 main phase is less than 88% by volume, the volume ratio of the R-rich phase increases and the residual magnetization decreases.
The raw material alloy for rare earth sintered magnet of the present invention is obtained by dividing the volume ratio of the 2-14-1 main phase, the average interval of the R-rich phase, and the standard deviation divided by the average interval of the R-rich phase at the same time. It is necessary to meet the requirements specified above.

The raw material alloy powder for rare earth sintered magnet of the present invention is an alloy powder obtained by pulverizing the raw material alloy for rare earth sintered magnet of the present invention to an average particle size (D50) of 3 to 7 μm, and the particle size distribution of the powder In addition, when the Rosin-Rammler distribution is applied, the uniform number is 1.90 or more, preferably 2.00 or more, and the particle size characteristic number is 4.0 to 10.0. The equal number is obtained as follows.
First, the particle size distribution of the alloy powder is measured using a laser diffraction particle size distribution meter, and the particle size integrated value (R (x)) for each particle size (x) is obtained. Then, a value (ln (ln (1 / R (x)))) obtained by taking the logarithm twice for the logarithmic value (ln x) of each particle size and the inverse of the particle size integrated value is calculated. Plotting with ln x on the X axis and (ln (ln (1 / R (x)))) on the Y axis gives a straight line, and the slope of this straight line is an even number in the Rosin-Rammler distribution. The particle size characteristic number is the value of x when R (x) = 0.368. As described above, when the equal number of pulverized powders is 1.90 or more and the number of particle size characteristics is 4.0 to 10.0, the magnetic characteristics, particularly the coercive force, is improved.

To produce the rare earth sintered material alloy for a magnet of the present invention, For example, R adjusted to the composition of the material alloy for rare earth sintered magnet before mentioned of the present invention, a molten alloy having a composition consisting of boron and M, A raw material alloy for rare earth sintered magnet that is cooled and solidified on a roll or disk by strip casting, and further cooled while controlling the heat history of the alloy slab after the cooled and solidified alloy slab is peeled off from the roll or disk. In which the heat history in the cooling is controlled to a specific one .

The molten alloy can be performed, for example, by a method of melting a raw material by an induction melting method in an inert gas atmosphere.
In the manufacturing method, the molten alloy is continuously cooled and solidified by a strip casting method using a single roll, a twin roll or a disk. At that time, the average cooling rate until the molten alloy is supplied to the roll or disk and the cast alloy strip is peeled off from the roll or disk is 50 to 1200 ° C./second, preferably 100 to 1000 ° C./second, more preferably 130 to Cooling and solidification are performed by controlling at 800 ° C./second (referred to as primary cooling step). By this primary cooling step, the crystal grain size of the 2-14-1 main phase, the phase interval of the R-rich phase, and the volume ratio are determined. If the average cooling rate becomes too fast, the volume ratio of the R-rich phase increases and the residual magnetization decreases. On the other hand, if it is too slow, the 2-14-1 main phase is coarsened, the dispersibility of the R-rich phase is lowered, and the coercive force is lowered.

In the manufacturing method, after the primary cooling step, the alloy slab is peeled off from the roll or the disk, and then the alloy is cooled by controlling the average cooling rate to the specific temperature T + 30 ° C. to 30 ° C./second or more (secondary cooling). Process). When the average cooling rate in the secondary cooling step is less than 30 ° C./second, the growth of crystal grains becomes remarkable, the proportion of the structure in which the R-rich phase interval exceeds 12 μm increases, and the structure variation increases. Further, when finely pulverized in the subsequent process, the particle size distribution becomes broad, and both the residual magnetization and the coercive force are reduced. Although the upper limit of the average cooling rate in the secondary cooling process of an alloy slab is not specifically limited, It is preferable that it is below the average cooling rate in a primary cooling process. If the secondary cooling step is performed at a speed exceeding the average cooling rate in the primary cooling step, it is difficult to control the temperature, and the temperature and time control in the vicinity of the specific temperature T for maintaining the temperature of the alloy slab described below. In this case, it is not preferable because there may be a variation in part.
The secondary cooling step includes, for example, natural heat dissipation until the alloy slab peels off from the roll or disk and reaches the temperature holding container, or heat generated by contact with a component of the casting apparatus until the alloy slab is introduced into the temperature holding container. Performed by conduction or the like.

In the manufacturing method, after the secondary cooling step, the alloy slab is held for 5 to 600 seconds, preferably 20 to 400 seconds, in a specific temperature T ± 30 ° C. range, preferably in a specific temperature T ± 20 ° C. range. (Referred to as temperature holding step). This temperature maintaining step means that the time required from the time when the specific temperature T + 30 ° C. is reached to the time when the specific temperature T−30 ° C. is 5 to 600 seconds. The temperature of the alloy slab may be lowered, constant, or increased within the specific temperature T ± 30 ° C.
The specific temperature T defined in the manufacturing method means a temperature defined by the following method.
That is, first, the cooling rate in the primary cooling step is 400 to 470 ° C./second, the cooling rate from the roll to 600 ° C. is 40 to 50 ° C./second, and the cooling rate from 600 ° C. to room temperature is The alloy slabs obtained by controlling each at 15 ° C./min were heat-treated at 700 ° C., 800 ° C. and 900 ° C. for 30 minutes, respectively, and the average interval between the R-rich phases before and after the heat treatment was compared. Find the grain growth rate. Next, a relational expression between x and y is obtained by the least square method, where x is the reciprocal of the heat treatment temperature (absolute temperature) and y is the crystal grain growth rate. From the obtained relational expression, the temperature obtained from x when the crystal grain growth rate is 130% is defined as the specific temperature T.

  By the temperature holding step, it is possible to precisely control the shape of the 2-14-1 main phase, the phase interval of the R-rich phase, the variation in the phase interval of the R-rich phase, the volume ratio, the constituent phase ratio, and the like. . For example, by this temperature holding step, the fine dentry arms of the 2-14-1 main phase disappear, the phase orientation becomes constant, and when pulverized in a subsequent step, the orientation differs in a single pulverized powder. The number of 2-14-1 main phases is reduced, which leads to an improvement in residual magnetization. If the holding time is too short, there is no effect, and if it is too long, the 2-14-1 main phase crystal grains become coarse, segregation occurs in the R-rich phase, and the coercive force is reduced. The average grain growth rate of the crystal grains composed of the 2-14-1 main phase is 180% or less, preferably 160% or less.

The temperature holding step can be performed by an apparatus having a heating mechanism. For example, when the alloy for a rare earth magnet is recovered in a storage container made of a highly heat-insulating material, most of the alloy cast immediately after the start of casting is brought into thermal conduction by directly contacting the storage container. However, as casting progresses, the alloy slabs are stacked in the storage container, and heat conduction by contact between the slabs is performed, so that the heat history between the slabs becomes non-uniform. In particular, in the case of casting by a strip casting method in a lot of hundreds of kg in industry, it takes several minutes to several tens of minutes from the start to the end of casting, so the difference in heat history in the same lot may not be negligible. If the thermal history becomes non-uniform, the structure of the alloy slab will vary. In particular, the R-rich phase interval of the alloy varies, and the value obtained by dividing the standard deviation of the R-rich phase interval by the average interval of the R-rich phase is greater than 0.25, leading to a decrease in magnet properties. Therefore, it is preferable that the obtained alloy for rare earth magnets has a certain thermal history within a casting lot.
Therefore, in the temperature holding step, in order to make the heat history constant, for example, a method of holding the temperature while continuously moving the alloy slab using a rotary drum type, rotary kiln type temperature holding device or the like is adopted. It is preferable to do. In the rotary drum type, a method can be adopted in which the slabs are retained in the drum while mixing the slabs by rotating the drum. In the rotary kiln system, the slabs are continuously retained in a predetermined direction without retaining in the drum by the rotation of the drums. The method of proceeding automatically can be adopted. In particular, the rotary kiln method is preferable. By combining such a method with the above-described strip casting method, a substantially uniform alloy slab structure can be obtained within a casting lot.

In the manufacturing method, if necessary, after the temperature holding step, a step of cooling the alloy slab to 500 ° C. at an average cooling rate of 3 to 10 ° C./min (referred to as a slow cooling step) may be performed. By the slow cooling step, the proportion of, for example, the α-Nd phase in the R-rich phase increases, and the pulverizability in the subsequent step can be improved.
In the manufacturing method, if necessary, after the slow cooling step, the alloy slab is transferred to a cooling vessel such as water cooling or gas cooling and the alloy slab is cooled to 100 ° C. or less at an average cooling rate of 7 to 30 ° C./min. When the slow cooling step is not required, the alloy slab may be cooled to 100 ° C. or less at an average cooling rate of 7 to 30 ° C./min after the temperature holding step (these are referred to as a tertiary cooling step). .
By the tertiary cooling step, the phase spacing of the R-rich phase, the variation in the R-rich phase spacing, the volume ratio, the constituent phase ratio, and the 2-14-1 main phase, which are controlled with high accuracy through the above-described steps. It becomes easy to maintain the shape. In addition, the tertiary cooling step can quickly lower the alloy slab temperature to near room temperature, collect the slab in a state in which oxidation is unlikely to occur, and subject it to pulverization and the like, thereby further improving production efficiency.

To produce the rare earth alloy powder for a magnet of the present invention, after the production process, the obtained rare earth magnet alloy, for example, was coarsely pulverized by hydrogen absorption-desorption, known to be pulverized with a jet mill pulverization process Etc. can be obtained.

Hereinafter, although an example and a comparative example explain the present invention still in detail, the present invention is not limited to these.
Example 1-1
Neodymium metal, ferroboron, aluminum, cobalt and iron so that the alloy composition is 31.5 mass% neodymium, 1.04 mass% boron, 0.15 mass% aluminum, 0.9 mass% cobalt and the balance iron. It mix | blended and melt | dissolved in the high frequency melting furnace using the alumina crucible in argon gas atmosphere. Subsequently, the obtained molten alloy was supplied to a single roll by a strip casting method to produce a cast piece having a thickness of about 0.4 mm (primary cooling step). The specific temperature T of this alloy is about 630 ° C. It was about 780 degreeC when the temperature of the slab immediately after peeling from the said roll was measured with the infrared thermal image measuring device. The temperature of the molten alloy immediately before contacting the roll was about 1300 ° C., and the cooling time on the roll was controlled to about 1.2 seconds. Therefore, the average cooling rate in the primary cooling step was controlled to about 430 ° C./second.

After that, the slab peeled from the roll was guided to the temperature control device 10 of the rotary kiln system in FIG. 1 (secondary cooling step). The apparatus 10 includes rotatable pipes 11-1 and 11-2 including a heating part 12 provided with a slab inlet 11a and a heat wire 12a, and shares a central axis outside the pipe 11-2. A rotatable tubular cooling pipe 15 is provided. The tubular cooling pipe 15 has a cooling part 17 provided with a refrigerant passage 17a. The pipes 11-1 and 11-2 have fins 13 inside. As the tubes 11-1 and 11-2 rotate, the slab 18 advances in the direction of the arrow in the figure. The slab 18 introduced into the pipe 11-1 from the introduction port 11 a does not stay by adjusting the rotation speed of the heating unit 12, the pipe 11-1, and the installation angle of the fin 13, and the predetermined direction of the arrow shown in the figure. , Continuously given a thermal history, kept at temperature, and discharged from the tube 11-1 (temperature keeping step).
The time required for the slab to reach the inlet 11a after peeling from the roll was about 0.8 seconds. After reaching the inlet 11a, the time required for discharging from the pipe 11-1 was 120 seconds. The slab temperature immediately after the roll peeling was about 780 ° C., the slab temperature at the inlet 11a was about 645 ° C., and the slab temperature just before being discharged from the tube 11-1 was about 600 ° C. The time maintained at the specific temperature T ± 30 ° C. was 120 seconds assuming that the time cooled to 660 to 645 ° C. was almost negligible. The average cooling rate in the secondary cooling step was about 170 ° C./second.
The slab discharged from the pipe 11-1 is introduced into the pipe 11-2, and is introduced into the pipe 11-2 by adjusting the heating section 12, the rotation speed, and the installation angle of the fins 13 of the pipe 11-2. The cast slab 18 continuously moved in the direction of the arrow, was cooled while being given a constant heat history, and was discharged from the tube 11-2 (slow cooling step). The temperature immediately after being introduced into the tube 11-2 is substantially the same as the slab temperature 600 ° C immediately before being discharged from the tube 11-2, and the slab temperature just before being discharged from the tube 11-1 is approximately 500 ° C. Met. The time required for the slab to be discharged after being introduced into the tube 11-2 was 15 minutes. Therefore, the average cooling rate in the slow cooling step was about 6.7 ° C./min. The slab discharged from the tube 11-2 was introduced into the tubular cooling tube 15. The slab was continuously moved and cooled by rotating the tubular cooling pipe 15 (third cooling process). After 40 minutes, the slab was taken out from the tubular cooling pipe 15. The slab temperature at that time was about 60 ° C. Therefore, the average cooling rate in the tertiary cooling step could be controlled to 11 ° C./min.
Table 1 shows the composition other than the remaining iron, the primary cooling rate during casting, the secondary cooling rate, the time maintained at the specific temperature T ± 30 ° C., the slow cooling rate, and the tertiary cooling rate.

When the cross-sectional structure of the obtained slab was observed with an optical microscope, the R-rich phase was present in the form of streaks or partial grains along the 2-14-1 main phase crystal grain boundary, and its average The spacing was 4.7 μm. The standard deviation of the R-rich phase interval was 0.85, and the value obtained by dividing the standard deviation of the R-rich phase interval by the average interval of the R-rich phase was 0.18. As a result of image analysis of the Compo image of EPMA, the volume ratio of the 2-14-1 main phase was 92% by volume. Further, when the precipitated phase in the R-rich phase was analyzed from the XRD diffraction peak intensity ratio, the proportion of the α-Nd phase in the total R-rich phase was about 50% by volume.
Next, hydrogen was occluded and released from the alloy and coarsely pulverized, and then finely pulverized by a jet mill to obtain a powder having an average particle diameter of about 5 μm. As a result of applying the particle size distribution of this jet mill powder to the Rosin-Rammler distribution, the uniform number was 2.1 and the particle size characteristic number was 6.0. This powder was molded at a pressure of 2.5 ton / cm ^{2 in} a magnetic field of 15 kOe. The obtained molded body was sintered in vacuum at 1060 ° C. for 2 hours, and then the first heat treatment was performed at 900 ° C. for 1 hour and the second heat treatment was performed at 500 ° C. for 2 hours.
Table 2 shows the structure of the obtained slab and the magnetic properties (residual magnetic flux density, coercive force, maximum energy product) of the magnet.

Examples 1-2 to 1-4
2 using the rotary kiln type temperature control device 20 shown in FIG. 2 that does not have the tube 11-2 of the temperature control device 10 in FIG. I got a piece. At this time, the slow cooling step is not performed. Next, the structure of the obtained slab was analyzed in the same manner as in Example 1-1. Moreover, the slab was grind | pulverized like Example 1-1 and the obtained ground material was analyzed. Further, a sintered magnet was prepared in the same manner as in Example 1-1, and the magnet characteristics of the obtained sintered magnet were measured. The results are shown in Table 2.

Example 2-1
Example 1 except that the alloy composition was 23.5 mass% neodymium, 8.0 mass% dysprosium, 1.04 mass% boron, 0.15 mass% aluminum, 0.9 mass% cobalt and the balance iron. In the same manner as -1, a slab having a thickness of about 0.35 mm was produced by a strip casting method. The specific temperature T of this alloy is about 730 ° C. The temperature of the molten metal immediately before coming into contact with the roll was about 1350 ° C., and the temperature of the slab immediately after peeling from the roll was about 880 ° C. Thereafter, the slab peeled from the roll was guided to the temperature control device 10 used in Example 1-1. After reaching the inlet 11a, the time required for discharging from the pipe 11-1 was 120 seconds. The slab temperature at the inlet 11a was about 750 ° C., and the slab temperature just before being discharged from the pipe 11-1 was about 700 ° C. The temperature immediately after being introduced into the tube 11-2 is substantially the same as the slab temperature 700 ° C immediately before being discharged from the tube 11-1, and the slab temperature immediately before being discharged from the tube 11-2 is approximately 500 ° C. Met. Thereafter, the slab was taken out from the tubular cooling pipe 15. The slab temperature at that time was about 60 ° C. The time maintained at the specific temperature T ± 30 ° C. was 120 seconds, assuming that the time cooled to 760 to 750 ° C. was almost negligible.
Table 1 shows the composition other than the remaining iron, the primary cooling rate during casting, the secondary cooling rate, the time maintained at the specific temperature T ± 30 ° C., the slow cooling rate, and the tertiary cooling rate.
Next, the structure of the obtained slab was analyzed in the same manner as in Example 1-1. Moreover, the slab was grind | pulverized like Example 1-1 and the obtained ground material was analyzed. Further, a sintered magnet was prepared in the same manner as in Example 1-1, and the magnet characteristics of the obtained sintered magnet were measured. The results are shown in Table 2.

Examples 2-2 to 2-4
Using the temperature control device 20 used in Example 1-2, a slab was obtained in the same manner as in Example 2-1, except that the thermal history shown in Table 1 was used. The slow cooling process is not performed. Next, the structure of the obtained slab was analyzed in the same manner as in Example 1-1. Moreover, the slab was grind | pulverized like Example 1-1 and the obtained ground material was analyzed. Further, a sintered magnet was prepared in the same manner as in Example 1-1, and the magnet characteristics of the obtained sintered magnet were measured. The results are shown in Table 2.

Examples 3-1 to 3-4
Example 2 except that the alloy composition was 26.5% by weight neodymium, 5.0% by weight dysprosium, 1.04% by weight boron, 0.15% by weight aluminum, 0.9% by weight cobalt and the balance iron. Cast pieces were produced in the same manner as -1 to 2-4. The specific temperature T of this alloy is about 700 ° C. The structure of the obtained slab was analyzed in the same manner as in Example 1-1. Moreover, the slab was grind | pulverized like Example 1-1 and the obtained ground material was analyzed. Further, a sintered magnet was prepared in the same manner as in Example 1-1, and the magnet characteristics of the obtained sintered magnet were measured. The results are shown in Table 2.

Comparative Example 1-1
An alloy cast was obtained in the same manner as in Example 1-1 by strip casting using raw materials having the same composition as in Example 1-1. After the alloy slab was peeled from the roll, the alloy slab was collected in a steel container having no temperature holding function. The temperature of the slab at the time of container collection | recovery was about 645 degreeC. Next, after sealing the container, the container was taken out into the atmosphere and allowed to cool. The temperature of the slab was about 600 ° C. after about 80 minutes of collection into the container, and 90 ° C. when taken out after 1500 minutes.
Table 1 shows the primary cooling rate, the secondary cooling rate, and the time at which the specific temperature T ± 30 ° C. was maintained during casting. At this time, for comparison, the time during which the slab was exposed to the temperature range of the specific temperature T ± 30 ° C. was defined as the temperature holding time. Next, the structure of the obtained slab was analyzed in the same manner as in Example 1-1. Moreover, the slab was grind | pulverized like Example 1-1 and the obtained ground material was analyzed. Further, a sintered magnet was prepared in the same manner as in Example 1-1, and the magnet characteristics of the obtained sintered magnet were measured. The results are shown in Table 2.

Comparative Example 1-2
An alloy cast was obtained in the same manner as in Example 1-1 by strip casting using raw materials having the same composition as in Example 1-1. The alloy slab was peeled from the roll, and then recovered in a rotary drum type water cooling device. The temperature of the slab at the time of water cooling apparatus collection | recovery was about 645 degreeC. The temperature of the slab was about 600 ° C. in about 3 seconds after being collected in the water cooling device, and after about 40 minutes, the slab was taken out and was about 70 ° C.
Table 1 shows the primary cooling rate, the secondary cooling rate, and the time at which the specific temperature T ± 30 ° C. was maintained during casting. At this time, for comparison, the time during which the slab was exposed to the temperature range of the specific temperature T ± 30 ° C. was defined as the temperature holding time. Next, the structure of the obtained slab was analyzed in the same manner as in Example 1-1. Moreover, the slab was grind | pulverized like Example 1-1 and the obtained ground material was analyzed. Further, a sintered magnet was prepared in the same manner as in Example 1-1, and the magnet characteristics of the obtained sintered magnet were measured. The results are shown in Table 2.

Comparative Example 1-3
An alloy cast was obtained in the same manner as in Example 1-1 by strip casting using raw materials having the same composition as in Example 1-1. After the alloy slab was peeled from the roll, it was collected in a heat insulating box made of a material having high heat insulating properties and held for 1 hour. The temperature of the slab immediately after collection in the heat insulation box is about 780 ° C., about 660 ° C. in about 2 minutes after collection in the heat insulation box, about 600 ° C. in about 10 minutes, and the temperature of the slab after holding for 1 hour is about 550 ° C. Met. Thereafter, the slab was collected in a rotating drum type water cooling device without performing the slow cooling step. When the slab was taken out in 40 minutes after being collected in a water cooling device, it was 60 ° C.
Table 1 shows the primary cooling rate, the secondary cooling rate, and the time at which the specific temperature T ± 30 ° C. was maintained during casting. At this time, for comparison, the time during which the slab was exposed to the specific temperature T ± 30 ° C. was defined as the temperature holding time. Next, the structure of the obtained slab was analyzed in the same manner as in Example 1-1. Moreover, the slab was grind | pulverized like Example 1-1 and the obtained ground material was analyzed. Further, a sintered magnet was prepared in the same manner as in Example 1-1, and the magnet characteristics of the obtained sintered magnet were measured. The results are shown in Table 2.

Comparative Example 1-4
Raw materials were blended so as to have the same composition as in Example 1-1, and a slab was produced by strip casting. At this time, the amount of hot water and the number of roll rotations were adjusted so that the average cooling rate in the primary cooling step was increased. The thickness of the slab was about 0.2 mm. The temperature of the molten metal immediately before contacting the roll was 1300 ° C., and the temperature of the slab immediately after peeling from the roll was about 750 ° C. Thereafter, the slab peeled from the roll was guided to the temperature control device 10 used in Example 1-1. After reaching the inlet 11a, the time required for discharging from the pipe 11-1 was 120 seconds. The slab temperature at the inlet 11a was about 630 ° C., and the slab temperature just before being discharged from the pipe 11-1 was about 600 ° C. The temperature immediately after being introduced into the tube 11-2 is substantially the same as the slab temperature 600 ° C immediately before being discharged from the tube 11-1, and the slab temperature immediately before being discharged from the tube 11-2 is 500 ° C. there were. Thereafter, the slab was taken out from the tubular cooling pipe 15. The slab temperature at that time was about 60 ° C.
Table 1 shows the primary cooling rate, the secondary cooling rate, and the time at which the specific temperature T ± 30 ° C. was maintained during casting. Next, the structure of the obtained slab was analyzed in the same manner as in Example 1-1. Moreover, the slab was grind | pulverized like Example 1-1 and the obtained ground material was analyzed. Further, a sintered magnet was prepared in the same manner as in Example 1-1, and the magnet characteristics of the obtained sintered magnet were measured. The results are shown in Table 2.

Comparative Examples 2-1 to 2-4
Comparative Example 1 except that the alloy composition was 23.5 mass% neodymium, 8.0 mass% dysprosium, 1.04 mass% boron, 0.15 mass% aluminum, 0.9 mass% cobalt, and the balance iron Cast pieces were produced in the same manner as -1 to 1-4. For comparison, the time during which the slab was exposed to the same temperature range as the specific temperature T ± 30 ° C. was defined as the temperature holding time.
Table 1 shows the primary cooling rate, the secondary cooling rate, and the time at which the specific temperature T ± 30 ° C. was maintained during casting. Next, the structure of the obtained slab was analyzed in the same manner as in Example 1-1. Moreover, the slab was grind | pulverized like Example 1-1 and the obtained ground material was analyzed. Further, a sintered magnet was prepared in the same manner as in Example 1-1, and the magnet characteristics of the obtained sintered magnet were measured. The results are shown in Table 2.

Comparative Examples 3-1 to 3-4
Comparative Example 1 except that the alloy composition was 26.5 mass% neodymium, 5.0 mass% dysprosium, 1.04 mass% boron, 0.15 mass% aluminum, 0.9 mass% cobalt, and the balance iron Cast pieces were produced in the same manner as -1 to 1-4. For comparison, the time during which the slab was exposed to the same temperature range as the specific temperature T ± 30 ° C. was defined as the temperature holding time.
Table 1 shows the primary cooling rate, the secondary cooling rate, and the time at which the specific temperature T ± 30 ° C. was maintained during casting. Next, the structure of the obtained slab was analyzed in the same manner as in Example 1-1. Moreover, the slab was grind | pulverized like Example 1-1 and the obtained ground material was analyzed. Further, a sintered magnet was prepared in the same manner as in Example 1-1, and the magnet characteristics of the obtained sintered magnet were measured. The results are shown in Table 2.

In an Example, it is the schematic for demonstrating the temperature control apparatus of the rotary kiln system used for implementation of a temperature holding process, a slow cooling process, and a tertiary cooling process. In an Example, it is the schematic for demonstrating the temperature control apparatus of the other rotary kiln system used for implementation of a temperature holding process and a tertiary cooling process.

Explanation of symbols

10, 20: Temperature control device 12: Heating unit 13: Fin 15: Tubular cooling pipe 18: Cast slab

Claims (4)

R27.6-33.0% by mass consisting of neodymium or at least one selected from the group consisting of neodymium and a rare earth metal element containing yttrium and no neodymium, and boron 0.94-1.30. An alloy having a composition consisting of mass% and the balance M containing iron,
The R-rich phase has an average interval of 3 to 12 μm, the standard deviation of the R-rich phase interval divided by the average interval of the R-rich phase is 0.25 or less, and the R ₂ Fe ₁₄ B system A raw material alloy for a rare earth sintered magnet, wherein the volume ratio of the main phase is 88% by volume or more.   The raw material alloy for a rare earth sintered magnet according to claim 1, wherein the balance M contains at least one selected from the group consisting of transition metal elements other than iron, silicon and carbon. R is neodymium, gadolinium, terbium, dysprosium, holmium, erbium, and a rare earth sintered magnet material alloy according to claim 1 or 2, characterized in that it comprises at least one selected from the group consisting of ytterbium . An alloy powder obtained by grinding the alloy for a rare earth sintered magnet raw material according to any one of claims 1 to 3 to an average particle size of 3 to 7 µm,
A raw material alloy for rare earth sintered magnet, wherein the alloy powder has a particle size distribution of 1.90 or more and a particle size characteristic number of 4.0 to 10.0 when the Rosin-Ramller distribution is applied. Powder.

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