Alloy for sintered magnets based on RTB rare earths, sintered magnets based on RTB rare earths and motor

Abstract

Alloy for sintered magnets based on RTB rare earth elements, wherein the alloy comprises: a rare earth element R, selected from Nd and Pr; a transition metal T essentially comprising Fe; a metallic element M, which is Ga or Ga and one or more metals selected from Al and Cu; B; and unavoidable impurities, wherein R constitutes 13 atomic % to 15 atomic %, B constitutes 4.5 atomic % to 6.2 atomic %, M constitutes 0.1 atomic % to 2.4 atomic %, Ga constitutes 0.07 atomic % to 1.95 atomic %, T constitutes the remainder and the following formula 1 is satisfied, 0.34 ≤ B / TRE ≤ 0.36 where B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements.

Description

[0001] The present invention relates to an alloy for sintered magnets based on RTB rare earths, sintered magnets based on RTB rare earths and a motor, and in particular to an alloy for sintered magnets based on RTB rare earths which has excellent magnetic properties and from which sintered magnets based on RTB rare earths can be produced, which are preferably used for motors. BACKGROUND OF THE INVENTION

[0002] To date, sintered RTB rare earth magnets (hereinafter sometimes referred to as "RTB-based magnets") have been used in motors, for example in voice coil motors in CD drives, and in motors for drives in hybrid vehicles or electric vehicles.

[0003] RTB-based magnets can be obtained by molding and sintering RTB-based alloy powder, which mainly contains Nd, Fe, and B. In general, in RTB-based alloys, R refers to Nd or an Nd-containing substance and other rare-earth elements, such as Pr, Dy, and Tb, which replace some of the Nd. T refers to Fe or an Fe-containing substance and other transition elements, such as Co and Ni, which replace some of the Fe. B refers to boron, and some of the boron may be replaced by C or N.

[0004] The structure of a typical RTB-based magnet essentially consists of a main phase made of R2T. 14 B and an R-rich phase, which is present in the grain boundary of the main phase and has a higher concentration of Nd than the main phase. The R-rich phase is also referred to as the grain boundary phase.

[0005] Furthermore, the composition of an RTB-based alloy is generally determined such that Nd, Fe and B are in a ratio that is as close as possible to R2T. 14 B is to increase the proportion of the main phase in the structure of the RTB-based magnet (see, for example, NPL 1).

[0006] Furthermore, there are cases where RTB-based alloys exhibit an R2T 17 -phase included. The R2T 17 The -phase is known to be a cause of the reduction in coercivity or rectangularity of an RTB-based magnet (see, for example, PTL 1). Therefore, when the R2T 17 -phase is present in an RTB-based alloy that contains R2T 17 -phase removed in a sintering stage in which an RTB-based magnet is produced.

[0007] Furthermore, since RTB-based magnets used in automotive engines are exposed to high temperatures in the engines, a large coercive force (Hcj) is required.

[0008] One method for improving the coercivity of RTB-based magnets involves replacing Nd (R) with Dy in an RTB-based alloy. However, Dy is rare and therefore produced only in small quantities, making its reliable supply difficult. Consequently, research is being conducted to improve the coercivity of an RTB-based magnet without increasing the amount of Dy in the RTB-based alloy.

[0009] To improve the coercivity (Hcj) of an RTB-based magnet, a method exists that involves adding metallic elements such as Al, Si, Ga, and Sn (see, for example, PTL 2). Furthermore, it is known that Al and Si are incorporated into RTB-based magnets as unavoidable impurities, as described in PTL 2. It is also known that if the amount of Si contained as an impurity in an RTB-based alloy exceeds 5%, the coercivity of the RTB-based magnet decreases (see, for example, PTL 3).

[0010] US 2011 / 0095855A1 discloses an alloy for sintered magnets based on RTB rare earth elements, wherein the alloy comprises: a rare earth element R; a transition metal T comprising substantially Fe; a metallic element M comprising Ga; B; and unavoidable impurities, wherein R constitutes 13 to 15 atomic percent, B constitutes 4.5 to 6.2 atomic percent, M constitutes 0.1 to 2.4 atomic percent, and T constitutes the remainder. Patent literature [PTL 1] Unexamined Japanese patent application, first publication no. JP 2007 - 119 882 A [PTL 2] Unexamined Japanese patent application, first publication no. JP 2009 - 231 391 A [PTL 3] Unexamined Japanese patent application, first publication no. JP H05-112 852 A Non-patented literature

[0011] [NPL 1] Permanent Magnet-Material Science and Application, by Masato Sagawa, first edition, second printing, published on November 30, 2008, pp. 256 to 261 SUMMARY OF THE INVENTION

[0012] In the prior art, however, there were cases where it was not possible to obtain an RTB-based magnet with a sufficiently high coercivity (Hcj), even when metallic elements such as Al, Si, Ga, and Sn were added to an RTB-based alloy. Therefore, it was necessary to increase the concentration of Dy, even when the metallic elements were added. Thus, there was a need to provide an RTB-based alloy from which RTB-based magnets with a high coercivity could be obtained without increasing the amount of Dy contained in the RTB-based alloy.

[0013] Taking into account the aforementioned circumstances, the invention was made, and an object of the invention is to provide an alloy for sintered magnets based on RTB rare earth elements, from which RTB-based magnets with a large coercivity can be obtained without increasing the amount of Dy contained in the RTB-based alloy, and a sintered magnet based on RTB rare earth elements for which the alloy material for sintered magnets based on RTB rare earth elements is used.

[0014] Another objective of the present invention is to provide a motor for which the sintered magnet is based on RTB rare earth elements.

[0015] The inventors of the present invention have carried out careful investigations to solve the aforementioned problem.

[0016] As a result, it was found that if a magnet is RTB-based, a main phase consisting mainly of R2Fe 14 Given that the RTB-based magnet contains B, and comprises a grain boundary containing more R than the main phase, and the grain boundary phase includes a grain boundary phase (R-rich phase) with a conventionally known high concentration of rare earth elements, and a grain boundary phase (transition metal-rich phase) with a lower concentration of rare earth elements and a higher concentration of transition metal elements than a prior art grain boundary phase, it is possible to obtain an RTB-based magnet with a high coercivity. Furthermore, it has been found that increasing the volume fraction of the transition metal-rich phase contained in the RTB-based magnet improves the coercivity.

[0017] Furthermore, the inventors investigated the compositions of an RTB-based alloy as described below to examine the effect of introducing Dy, which improves the coercive force in an RTB-based magnet containing the transition metal-rich phase.

[0018] That is, the transition metal-rich phase has a lower concentration of all rare earth element atoms and a higher concentration of iron atoms than other grain boundary phases. Therefore, investigations were carried out to increase the concentration of iron or to decrease the concentration of boron.

[0019] The results showed that the coercive force reached a maximum at a specific concentration of B. Furthermore, it was found that the optimal concentration of B varies depending on the concentration of Dy. (1) An alloy for sintered magnets based on RTB rare earth elements, comprising: a rare earth element R, selected from Nd and Pr; a transition metal T essentially comprising Fe; a metallic element M, which is Ga or Ga and one or more metals selected from Al and Cu; B; and unavoidable impurities, wherein R constitutes 13 atomic % to 15 atomic %, B constitutes 4.5 atomic % to 6.2 atomic %, M constitutes 0.1 atomic % to 2.4 atomic %, Ga constitutes 0.07 atomic % to 1.95 atomic %, T constitutes the remainder and the following formula 1 is satisfied, 0.34≤B / TRE≤0.36 where B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements. (2) The alloy for sintered magnets based on RTB rare earth elements according to (1) wherein M constitutes 0.7 atomic % to 1.4 atomic %. (3) The alloy for sintered magnets based on RTB rare earth elements according to (1) or (2), which also contains Si. (4) The alloy for sintered magnets based on RTB rare earth elements according to (1) or (2), where the area ratio of an area that is an R2T 17 -phase, which ranges from 0.1% to 50%. (5) A sintered RTB rare earth-based magnet comprising: a rare earth element R, selected from Nd and Pr; a transition metal T containing essentially Fe; a metallic element M, which is Ga or Ga and one or more metals selected from Al and Cu; B; and unavoidable impurities, where R accounts for 13 to 15 atomic percent, B for 4.5 to 6.2 atomic percent, M for 0.1 to 2.4 atomic percent, Ga for 0.07 to 1.95 atomic percent, and T is the remainder, the following formula 1 is satisfied. manufactured from a sintered body that includes a main phase consisting mainly of R2Fe 14B and a grain boundary comprising more R than the main phase, wherein the grain boundary phase comprises a phase having a concentration of all atoms of the rare earth elements of 70 atomic % or more, and a phase having a concentration of all atoms of the rare earth elements in the range of 25 atomic % to 35 atomic % 0.34≤B / TRE≤0.36 where B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements. (6) The sintered RTB rare earth-based magnet according to (5), which also includes Si. (7) The sintered RTB rare earth-based magnet according to (5) or (6), wherein the volume ratio of the phase with a concentration of all atoms of the rare earth elements in a range of 25 atomic % to 35 atomic % is in the range of 0.005 vol. % to 3 vol. %. (8) A motor incorporating the sintered magnet based on RTB rare earth according to (5) or (6).

[0020] In the present invention, to distinguish the grain boundary phase of the alloy for sintered magnets based on RTB rare earth from the grain boundary phase of the sintered magnet based on RTB rare earth, the grain boundary phase of the alloy for magnets is referred to as the alloy grain boundary phase.

[0021] Since the alloy material for sintered RTB rare earth-based magnets of the present invention has an amount of B satisfying the preceding formula 1 and contains 0.1 atomic % to 2.4 atomic % of the metallic element, it is possible to sufficiently ensure the volume fraction of the transition metal-rich phase in an RTB rare earth-based permanent magnet formed by forming and sintering the alloy material and to obtain the RTB rare earth-based permanent magnet of the present invention with a large coercive force, while reducing the amount of Dy.

[0022] Since the sintered RTB rare earth magnet of the present invention has a large coercive force, the sintered RTB rare earth magnet can also be preferably used for motors and the like.

[0023] Since the method for producing alloys according to the invention for sintered magnets based on RTB rare earth elements is a method in which the temperature holding stage, in which the cast alloy is held at a specific temperature for 10 seconds to 120 seconds while the temperature of the cast alloy is reduced from more than 800°C to less than 500°C, is carried out in the casting stage, it is possible to sufficiently ensure the volume fraction of the transition metal-rich phase in a permanent magnet based on RTB rare earth elements, formed by molding and sintering the obtained RTB-based alloy, and to obtain a permanent magnet based on RTB rare earth elements with a high coercivity while keeping the amount of Dy low. BRIEF DESCRIPTION OF THE DRAWINGS Fig.Figure 1 is a view showing the relationship between B / TRE (B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements) and Hcj (coercive force) of a sintered magnet produced using an alloy with Dy=0 atomic %). Fig. Figure 2 is a view showing the relationship between B / TRE (B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements) and Hcj (coercive force) of a sintered magnet produced using an alloy with Dy≈3.8 atomic %). Fig.Figure 3 is a view showing the relationship between B / TRE (B represents the concentration (atomic %) of the boron element, and TRE represents the concentration (atomic %) of all rare earth elements) and Hcj (coercive force) of a sintered magnet produced using an alloy with Dy≈8.3 atomic %). Fig. Figure 4 is a view showing the relationship between the concentration of Dy and B / TRE (B represents the concentration (atomic %) of the boron element, and TRE represents the concentration (atomic %) of all rare earth elements) at a point where the coercive force reaches a maximum. Fig. Figure 5 is a diagram of a ternary RTB phase. Fig. Figure 6 is a backscattered electron image of a cross-section of alloy F. Fig. 7 is a view 4 of an enlarged area in which an R2T 17 -phase is generated. Fig.Figure 8 is a microscopic photograph of an RTB-based magnet and a backscattered electron image of an RTB-based magnet of experimental example 9. Fig. Figure 9 is a microscopic photograph of an RTB-based magnet and a backscattered electron image of an RTB-based magnet from experimental example 6. Fig. 10(a) is a microscopic photograph of an RTB-based magnet and a backscattered electron image of an RTB-based magnet of experimental example 23. Fig. Figure 10(b) is a schematic view describing the microscopic photography of the in Fig. 10(a) illustrated RTB-based magnets. Fig. Figure 11 is a schematic front view illustrating an example of a device used to produce an alloy. Fig.Figure 12(a) is a graph illustrating the relationship between the distance between alloy grain boundary phases and the concentration of B. Fig. Figure 12(b) is a graph illustrating the relationship between the distance of alloy grain boundary phases and B / TRE, and Fig. 12(c) is a graph illustrating the relationship between the distance between alloy grain boundary phases and Fe / B. Fig. 13(a) is a microscopic photograph of a cross-section of a thin cast alloy piece, wherein Fe / B is 15.5, Fig. 13(b) is a microscopic photograph of a cross-section of a thin cast alloy piece, wherein Fe / B is 16.4. Fig. Figure 14 is a graph illustrating the distances between alloy grain boundary phases in experimental example 35 and the distances between alloy grain boundary phases in experimental example 36. Fig.Figure 15 illustrates graphs showing the relationship between the time elapsed for a manufactured casting alloy to reach 50°C, starting from 1200°C, and the temperature. Fig. Figure 15(a) illustrates the temperatures against the elapsed times in a range from 0 seconds to 1 second, Fig. Figure 15(b) illustrates the temperatures against the elapsed times in a range from 0 seconds to 250 seconds, and Fig. Figure 15(c) illustrates the temperatures against the elapsed times in a range from 0 seconds to 700 seconds. Fig. Figure 16(a) is a graph illustrating the coercive forces (Hcj) of magnets on an RTB basis from experimental examples 37 to 40. Fig. Figure 16(b) is a graph illustrating the RTB-based remanence (Br) of the magnets of experimental examples 37 to 40, and Fig.Figure 16(c) is a graph illustrating the relationship between the remanence (Br) and the coercive forces (Hcj) of the magnets on RTB basis of experimental examples 37 to 40. Fig. Figure 17(a) is a graph illustrating the second quadrants of the hysteresis curves of experimental examples 47 and 48, measured using a BH curve meter, and Fig. Figure 17(b) is a graph illustrating the second quadrants of the hysteresis curves of experimental examples 49 and 50, measured using a BH curve meter. The vertical axis shows the magnetization J, and the horizontal axis indicates the magnetic fields H. DESCRIPTION OF THE EXECUTION FORMS

[0024] The following describes various embodiments in detail, but only the first embodiment is according to the invention. [First embodiment]“Alloy for sintered magnets based on RTB rare earth”

[0025] An alloy for sintered RTB rare earth-based magnets according to the first embodiment (hereinafter referred to as "RTB-based alloy") is an alloy used to produce a sintered RTB rare earth-based magnet (hereinafter referred to as "RTB-based magnet") according to the present invention by producing a sintered body comprising a main phase consisting mainly of R2Fe 14 B contains, and a grain boundary phase containing more R than the main phase is formed and sintered, wherein the grain boundary phase has an R-rich phase and a transition metal-rich phase, which has a grain boundary phase with a lower concentration of rare earth elements and a higher concentration of transition metal elements than the R-rich phase.

[0026] In this embodiment, the r-rich phase is a phase in which the concentration of all atoms of the rare-earth element r is 70 atomic percent or more. The transition-metal-rich phase is a phase in which the concentration of all atoms of the rare-earth element r is in the range of 25 atomic percent to 35 atomic percent. The transition-metal-rich phase preferably contains 50 atomic percent to 70 atomic percent of a transition metal T containing substantially iron.

[0027] The RTB-based alloy of this embodiment is an RTB-based alloy which comprises: a rare earth element R, selected from Nd and Pr; a transition metal T essentially comprising Fe; a metallic element M, which is Ga or Ga and one or more metals selected from Al and Cu; B; and unavoidable impurities, wherein R constitutes 13 atomic % to 15 atomic %, B constitutes 4.5 atomic % to 6.2 atomic %, M constitutes 0.1 atomic % to 2.4 atomic %, Ga constitutes 0.07 atomic % to 1.95 atomic %, T constitutes the remainder and the following formula 1 is satisfied, 0.34≤B / TRE≤0.36 where B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements. If the amount of rhodium (R) in the RTB-based alloy is less than 13 atomic percent, the coercivity of the RTB-based magnet obtained using the alloy will be insufficient. Furthermore, if the amount of rhodium exceeds 15 atomic percent, the remanence of an RTB-based magnet obtained using the alloy will be low, and the magnet will be unsuitable for use as a magnet.

[0028] Furthermore, the boron (B) contained in the RTB-based alloy is boron, and some of the B may be replaced by carbon (C) or nitrogen (N). The amount of B is in the range of 4.5 atomic percent to 6.2 atomic percent and satisfies the formula 1 above. The amount of B is more preferably in the range of 4.8 atomic percent to 5.5 atomic percent. If the amount of B contained in the RTB-based alloy is less than 4.5 atomic percent, the coercivity of an RTB-based magnet obtained using the alloy will be insufficient. If the amount of B is beyond the range of the formula 1 above, the amount of the transition-metal-rich phase produced will be insufficient, and the coercivity will not be adequately improved.

[0029] The RTB-based alloy according to this embodiment comprises a main phase consisting mainly of R2Fe 14B contains, and an alloy grain boundary phase containing more R than the main phase. The alloy grain boundary size can be observed using a backscattered electron image from an electron microscope. It is possible that the alloy grain boundary phase contains essentially only R or RTM.

[0030] In the RTB-based alloy according to this embodiment, to achieve a spacing between the alloy grain boundary phases of 3 µm or less, the amount of B contained in the RTB-based alloy is specified in the range of 5.0 atomic percent to 6.0 atomic percent. When the amount of B is specified in the aforementioned range, the grain diameter of an alloy structure is reduced, thus improving grindability, and the grain boundary phase is uniformly distributed in an RTB-based magnet manufactured using the alloy, resulting in excellent coercivity. To obtain a fine alloy structure with superior grindability and a spacing between the alloy grain boundary phases of 3 µm or less, the amount of B is preferably specified in 5.5 atomic percent or less.However, if the amount of boron (B) in the RTB-based alloy is less than 5.0 atomic percent, the distance between adjacent alloy grain boundary phases in the RTB-based alloy increases abruptly, making it difficult to obtain a fine alloy structure with an inter-grain boundary spacing of 3 µm or less. Furthermore, with an increased amount of boron in the RTB-based alloy, the distance between adjacent alloy grain boundary phases in the RTB-based alloy increases abruptly, and the alloy grains become large. If the amount of boron becomes excessive, a boron-rich phase will also be trapped in a sintered magnet. Therefore, if the amount of boron exceeds 6.0 atomic percent, there is a risk that the coercivity of an RTB-based magnet manufactured using this alloy will be insufficient.

[0031] To reduce the grain diameter of the alloy structure, thereby improving the coercivity of an RTB-based magnet produced using the alloy, the ratio (Fe / B) of the amount of Fe to the amount of B contained in the RTB-based alloy is preferably in the range of 13 to 16. Furthermore, in the case where the Fe / B ratio is in the range of 13 to 16, the generation of the transition-metal-rich phase is effectively accelerated in a stage where RTB-based alloys are produced and / or in a stage where RTB-based magnets are manufactured.

[0032] If Fe / B exceeds 16, the distance between adjacent alloy grain boundary phases in the RTB-based alloy is abruptly increased, and it becomes difficult to obtain a fine alloy structure with a distance between the alloy grain boundary phases of 3 µm or less.

[0033] Furthermore, if the Fe / B ratio falls below 13, the distance between adjacent alloy grain boundary phases in the RTB-based alloy increases with a decrease in Fe / B, and the alloy grains become large. Therefore, if the Fe / B ratio is less than 13, there is a risk that the coercive force of an RTB-based magnet manufactured using this alloy could be insufficient.

[0034] To reduce the grain diameter of the alloy structure, thereby improving the coercivity of an RTB-based magnet manufactured using the alloy, B / TRE is preferably set to a range of 0.355 to 0.38. B / TRE is more preferably 0.36 or less, resulting in a fine alloy structure with improved millability and an inter-grain boundary spacing of 3 µm or less. If B / TRE is less than 0.355, the inter-grain boundary spacing in the RTB-based alloy increases abruptly, making it difficult to achieve a fine alloy structure with an inter-grain boundary spacing of 3 µm or less. Furthermore, increasing B / TRE increases the inter-grain boundary spacing in the RTB-based alloy, resulting in larger alloy grains.Therefore, if B / TRE exceeds 0.38, there is a risk that the coercive force of an RTB-based magnet manufactured using the alloy will be insufficient.

[0035] Furthermore, the titanium dioxide (T) contained in the RTB-based alloy is essentially an iron-containing transition metal. Various elements from groups 3 to 11 can be used as transition metals other than iron in the T of the RTB-based alloy. If the RTB-based alloy contains cobalt (Co) in addition to iron, the Curie temperature (Tc) can be improved, which is preferred.

[0036] Fig. Figure 1 is a view showing the relationship between B / TRE (B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements) and Hcj (coercive force) of a sintered magnet produced using an alloy with Dy=0 atomic %). Fig. 1. The coercive force reaches its maximum when B / TRE=0.35.

[0037] Fig. Figure 2 is a view showing the relationship between B / TRE (B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements) and Hcj (coercive force) of a sintered magnet produced using an alloy with Dy ≈ 3.8 atomic %). Fig. 2. The coercive force reaches its maximum when B / TRE=0.37.

[0038] Fig. Figure 3 is a view showing the relationship between B / TRE (B represents the concentration (atomic %) of the boron element, and TRE represents the concentration (atomic %) of all rare earth elements) and Hcj (coercive force) of a sintered magnet produced using an alloy with Dy ≈ 8.2 atomic %). Fig. 3. The coercive force reaches its maximum when B / TRE=0.39.

[0039] When the relationship between the concentration of Dy and B / TRE is plotted at a point where the coercivity reaches its maximum, this relationship is expressed as in Fig. 4 illustrates. From the straight line into Fig. 4. The following formula is derived B / TRE=0.0049Dy+0.35

[0040] From the Fig. 2 and Fig.It follows from equation 3 that the width of B / TRE in which the coercive force is reduced from its maximum to less than 90% of its maximum value lies outside a range of B / TRE in which the coercive force reaches its maximum ± 0.01. This means that in a range from the above formula 2 -0.01 to the above formula 2 +0.01, a coercive force equal to or greater than 90% of the maximum coercive force can be obtained. Assuming that the aforementioned range represents a suitable B / TRE ratio, the appropriate range of B / TRE is represented by the following equation 1. 0.0049Dy+0.34≤B / TRE≤0.0049Dy+0.36

[0041] An alloy that satisfies the above formula 1 has a higher concentration of Fe and a lower concentration of B than a prior art RTB-based alloy. Fig. Figure 5 is a diagram of the ternary RTB phase. Fig.In figure 5, the vertical axis indicates the concentration of B, and the horizontal axis indicates the concentration of Nd. Fig. Figure 5 illustrates that as the concentration of B and Nd decreases, the concentration of Fe increases. In general, an alloy with a composition (for example, a composition represented by a black Δ in Fig. 5) is cast in a colored area, thereby producing an RTB-based magnet consisting of the main phase and the r-rich phase. The compositions of the RTB-based alloys according to the invention, which satisfy the above formula 1, are in an area on the side of the lower r-concentration of the above-mentioned area, as by using O in Fig. 5 is illustrated.

[0042] When an RTB-based alloy that meets the above formula 1 is produced, an R2T is achieved. 17-phase effortlessly generated. The R2T 17 -phase is known to be a cause of impairment of the coercivity or rectangularity of an RTB-based magnet, and generally an RTB-based alloy is used under a condition in which the R2T 17 -phase is not generated, manufactured. However, in the present invention it is assumed that the R2T 17 -phase serves as the starting material for the transition metal-rich phase in a stage where RTB-based alloys are produced, and / or in a stage where RTB-based magnets are produced.

[0043] In the RTB-based alloy according to the invention, the area fraction of a region that contains the R2T 17 -phase, preferably in the range of 0.1% to 50%, and more preferably in the range of 0.1% to 25%. In the case that the area fraction of a region containing the R2T 17If the transition-metal-rich phase is included in the aforementioned area, the generation of the transition-metal-rich phase is effectively accelerated, and an RTB-based magnet that sufficiently encloses the transition-metal-rich phase and has a large coercivity can be obtained. If the area fraction of a region containing the R2T 17 If the -phase is 50% or higher, it is not possible to use the R2T 17 -phase to be fully consumed in a stage in which RTB-based magnets are manufactured, and there are cases where the coercivity or rectangularity of the RTB-based magnet is affected.

[0044] Furthermore, in the RTB-based alloy according to this embodiment, in the case that the area fraction of a region which the R2T 17 Including the -phase, which lies in a range of 0.1% to 50%, excellent grindability is achieved. Since the R2T 17 The -phase is more fragile than the R2T phase.14 B-phase, in the case where the alloy according to the invention is RTB-based, has a region that contains the R2T 17 -phase, which contains an area fraction in the range of 0.1% to 50%, the alloy can be easily ground, and thus it is possible to process the alloy into fine grains with a grain diameter of about 2 µm.

[0045] The area fraction of a region that contains the R2T 17 The area fraction, which includes the -phase, is obtained by microscopic observation of a cross-section of a thin cast alloy piece intended for processing into an RTB-based alloy. More precisely, the area fraction is obtained in the following order.

[0046] A thin piece of cast alloy is embedded in a resin, cut along its thickness, mirror-polished, and then gold or carbon is deposited to impart conductive properties, thus producing a viewing pattern. A backscattered electron image of the pattern is acquired using a scanning electron microscope at 300x or 350x magnification.

[0047] Fig. Figure 6 illustrates, as an example, a backscattered electron image of a cross-section of alloy F described in Table 1, taken at 350x magnification. The image shows a gray R2T 14 B-phase and white, line-like, R-rich phases were observed. Additionally, there are areas where point-like, R-rich phases are observed (areas surrounded by white lines). In the present application, the region described above is considered a region containing the R2T 17-phase contains, is referred to. The ratio of the area of ​​the region to an image of the cross-section is the area ratio of the region containing the R2T. 17 -phase contains, is designated.

[0048] Fig. Figure 7 is a highly magnified photograph of an area where the R2T 17 -phase is generated. Fig. 7, shown in strong contrasts, is found to be black dotted R2T 17 -phases (2-17 phases), white R-rich phases and grey main phases (2-14-1 phases) are generated in the area where the R2T 17 -phase is generated.

[0049] The metallic element M, which is included in the RTB-based alloy according to this embodiment, presumably accelerates the generation of the transition metal-rich phase in a stage in which the cooling rate of a thin cast alloy piece is temporarily slowed down after casting, which is carried out when the RTB-based alloy (the temperature conservation stage of a cast alloy described below) is produced, or during sintering and thermal treatment to produce the RTB-based magnet.

[0050] Since the RTB-based alloy according to this embodiment contains 0.1 atomic % to 2.4 atomic % of the metallic element M when the RTB-based alloy is sintered, an RTB-based magnet that includes the R-rich phase and the transition metal-rich phase can be obtained.

[0051] The metallic element M accelerates the formation of the transition metal-rich phase in the temperature conservation stage of the casting alloy or during sintering or thermal treatment of the RTB-based magnet, without adversely affecting other magnetic properties, thereby effectively improving the coercivity (Hcj).

[0052] If the amount of metallic element M is less than 0.1 atomic percent, there is a risk that the effect that accelerates the generation of the transition-metal-rich phase will not develop sufficiently, so that the transition-metal-rich phase is not formed in the RTB-based magnet and the coercivity (Hcj) of the RTB-based magnet cannot be sufficiently improved. Furthermore, if the amount of metallic element M exceeds 2.4 atomic percent, magnetic properties such as the remanence (Br) of the RTB-based magnet or the maximum energy product (BHmax) deteriorate. The amount of metallic element is more favorably in the range of 0.7 atomic percent to 1.4 atomic percent.

[0053] If the RTB-based alloy contains copper, the copper concentration is preferably in the range of 0.07 atomic percent to 1 atomic percent. If the copper concentration is less than 0.07 atomic percent, sintering the magnet will be difficult.

[0054] Furthermore, if the concentration of copper exceeds 1 atomic percent, the remanence (Br) of the RTB-based magnet will be impaired, which is not desirable.

[0055] The RTB-based alloy of this embodiment may also contain Si in addition to a rare-earth element R, a transition metal T containing substantially Fe, a metallic element M, and B. If the RTB-based alloy contains Si, the amount of Si is preferably in the range of 0.7 atomic percent to 1.5 atomic percent. If the RTB-based alloy contains Si in the aforementioned range, the coercivity is further improved. If the amount of Si is less than 0.7 atomic percent or more than 1.5 atomic percent, the effect of the Si inclusion is impaired.

[0056] If the total concentration of oxygen, nitrogen, and carbon contained in the RTB-based alloy is high, the rare earth element R is combined with these elements during the sintering stage of the RTB-based magnet as described below, leading to its consumption. Therefore, the rare earth element R contained in the RTB-based alloy reduces the amount of R used as the starting material for the transition-rich phase in the thermal treatment of the RTB-based magnet obtained by sintering the alloy. Consequently, there is a risk that the amount of transition-rich phase produced will be reduced, resulting in insufficient coercivity of the RTB-based magnet.Therefore, in this embodiment, the total concentration of oxygen, nitrogen, and carbon contained in the RTB-based alloy is preferably 0.5 wt.% or less. By setting the total concentration to the aforementioned concentration or less, the consumption of the rare earth element R is suppressed, and the coercive force (Hcj) can be effectively improved. "Process for producing the RTB-based alloy"

[0057] The RTB-based alloy according to the invention is obtained as follows. For example, a molten alloy with a predetermined composition, heated to approximately 1450°C, is cast, for example using a thin-strip (SC) process, resulting in a thin cast alloy piece. At this point, a treatment (the temperature maintenance stage) can be carried out in which the cooling rate of the thin cast alloy piece after casting is temporarily slowed to the range of 700°C to 900°C, thus accelerating the diffusion of the components in the alloy.

[0058] The resulting thin cast alloy piece is then crushed using a hydrogen decrepitation process or the like and ground using a mill, resulting in an RTB-based alloy.

[0059] In this embodiment, a method is used in which an RTB-based alloy is produced using a Fig. The production apparatus illustrated in section 11 is described as an example of a process for producing the alloy according to the invention on an RTB basis. (Apparatus for producing the alloy)

[0060] Fig. Figure 11 is a schematic front view illustrating an example of an apparatus used to produce the alloy.

[0061] The apparatus used to produce alloy 1, which is located in Fig. Figure 11 illustrates a casting apparatus 2, a crushing apparatus 21, a heating apparatus 3 arranged below the crushing apparatus 21, and a storage container 4 arranged below the heating apparatus 3.

[0062] The crushing apparatus 21 is an apparatus that crushes a lump of casting alloy cast using the casting apparatus 2, thereby obtaining thin pieces of casting alloy. How Fig. Figure 11 illustrates a hopper 7 which directs the thin cast alloy pieces to a platform 32, which can be opened, into the heating apparatus 3, arranged between the crushing apparatus 21 and the platform 32, which can be opened.

[0063] The heating apparatus 3 consists of a heater 31 and a container 5. The container 5 comprises the storage container 4 and the platform 32, which can be opened and is positioned above the storage container 4. The platform 32, which can be opened, consists of a plurality of platforms 33, which can be opened. The platforms 33, which can be opened, carry the thin cast alloy pieces supplied by the crushing apparatus 21 when the platforms are closed, and guide the thin cast alloy pieces to the storage container 4 when the platforms are open.

[0064] The production apparatus 1 also includes a conveyor belt 51 (movement apparatus) that moves the container 5 freely, so that the container 5 moves in a horizontal direction in Fig. 11 can be moved using conveyor belt 51.

[0065] Furthermore, the in Fig. Figure 11 shows a production apparatus 1 and a chamber 6. The chamber 6 comprises a casting chamber 6a and a heat retention and storage chamber 6b, which is arranged below the casting chamber 6a and is connected to the casting chamber 6a. The casting chamber 6a contains the casting apparatus 2, and the heat retention and storage chamber 6b contains the heating apparatus 3.

[0066] To produce the RTB-based alloy according to this embodiment, a molten alloy with a predetermined composition, heated to approximately 1450°C, is first prepared in a melting apparatus (not shown). The resulting molten alloy is then transferred to a cooling roller 22, consisting of a copper roller, for water cooling in the casting apparatus 2 using an intermediate container (not shown), and solidifies, thus yielding the casting alloy. The casting alloy is then released from the cooling roller 22 and comminuted between the comminution rollers in the comminution apparatus 21, resulting in thin pieces of the casting alloy.

[0067] The crushed thin casting alloy pieces pass through the hopper 7 and are accumulated in a "closed" state on the platforms 33, which can be opened, and on platform 32, which can be opened and is located below the hopper 7. The thin casting alloy pieces accumulated on the platforms 22, which can be opened, are heated using the heater 31.

[0068] In this embodiment, a temperature maintenance stage is performed in which the produced casting alloy, which is hotter than 800°C, is held at a specific temperature for 10 to 120 seconds until the temperature of the casting alloy is below 500°C. In this embodiment, the thin casting alloy pieces are heated using the heater 31. The thin casting alloy pieces, at a temperature range of 800°C to 500°C, are then conveyed to and accumulated on the accessible platforms 33. The temperature maintenance stage, in which the casting alloy is held at a specific temperature for 10 to 120 seconds, is then initiated.

[0069] After a predetermined period, the stages 33 that can be opened are switched to the "open" state, and the thin casting alloy pieces that have accumulated on the platforms 33 that can be opened are dropped into the storage container 4. Then the heat from the heater 31 can no longer reach the thin casting alloy pieces, and the thin casting alloy pieces begin to cool down again, and the temperature maintenance stage ends.

[0070] When the temperature conservation step is performed, it is assumed that among the elements contained in the casting alloy, the component switching between metallic element M and B is accelerated due to the rearrangement of the elements moving within the alloy. It is then assumed that a portion of B, contained in a region acting as the alloy grain boundary phase, migrates to the main phase, and a portion of metallic element M, contained in the region acting as the main phase, migrates to the alloy grain boundary phase. As a result, it is assumed that the intrinsic magnetic properties of the main phase cannot manifest, thus increasing the coercivity of a magnet obtained using the alloy on an RTB basis.

[0071] If the temperature of the casting alloy exceeds 800°C during the temperature maintenance phase, there is a risk of the alloy structure becoming coarse. Furthermore, if the time the casting alloy is held at a specific temperature exceeds 120 seconds, there are instances where productivity is adversely affected.

[0072] Furthermore, if the temperature of the casting alloy in the temperature conservation stage is lower than 500°C, or if the time during which the casting alloy is held at a certain temperature is shorter than 10 seconds, there are cases in which the effect of the temperature conservation stage, in which elements are rearranged, cannot be sufficiently achieved.

[0073] In this embodiment, the temperature maintenance stage is carried out by using a method in which the thin casting alloy pieces, which are in a temperature range of 800°C to 500°C and are piled on the platforms 33, which can be opened, are heated using the heater 31, wherein the method for carrying out the temperature maintenance stage is not restricted as long as the casting alloy can be kept at a certain temperature for 10 seconds to 120 seconds, hotter than 800°C, until the temperature of the casting alloy is below 500°C.

[0074] In the process for producing the RTB-based alloy according to this embodiment, a reduced-pressure atmosphere of an inert gas is preferably created in chamber 6, in which the RTB-based alloy is produced. Furthermore, in this embodiment, at least part of the casting stage is carried out in a helium-containing atmosphere. Helium dissipates heat from the casting alloy better than argon, and it is easily possible to increase the cooling rate of the casting alloy.

[0075] Examples of the process, in which at least part of the casting stage is carried out in a helium-containing atmosphere, include a process in which helium is introduced as an inert gas into the casting chamber 6a in chamber 6 at a predetermined flow rate. Since a helium-containing atmosphere is formed in the casting chamber 6a, it is possible in this case to effectively cool the surfaces of the casting alloy being cast using the casting apparatus 2 and then quench it using the cooling roller 22, with the surfaces not being in contact with the cooling roller 22.Therefore, the cooling rate of the casting alloy is increased, the grain diameter of the alloy structure is reduced, the comminutability becomes excellent, a fine alloy structure with a distance between the alloy grain boundary phases of µm or less is easily obtained, and the coercivity of an RTB-based magnet obtained using the alloy can be improved. Furthermore, if a helium-containing atmosphere is created in the casting chamber 6a, it is possible, due to the increased cooling rate of the casting alloy, to set the temperature of the thin casting alloy pieces accumulated on the accessible platforms 33 to 800°C or lower.

[0076] In the RTB-based alloy production process according to this embodiment, the thin cast alloy pieces, which have undergone a temperature maintenance stage, are preferably cooled in a helium-containing atmosphere. Since the cooling rate of the thin cast alloy pieces, which constitute the cast alloy subjected to a temperature maintenance stage, is increased, the alloy structure is further minimized, and a fine alloy structure exhibiting excellent comminution and a distance between the alloy grain boundary phases of 3 µm or less can be easily obtained.Examples of a method for cooling the thin cast alloy pieces that have been subjected to a temperature conservation stage in a helium-containing atmosphere include a method in which helium is directed at a fixed flow rate into the storage container 4, which contains the thin cast alloy pieces that have fallen from the platforms 33, which can be opened.

[0077] In this embodiment, a case was described in which the RTB-based alloy is produced using the SC process, but the RTB-based alloy used in the present invention is not limited to the alloy produced using the SC process. For example, the RTB-based alloy can be cast using a centrifugal casting process, a block casting process, or the like.

[0078] The hydrogen decrepitation process is carried out in a sequence in which, for example, hydrogen is absorbed into the thin casting alloy pieces at room temperature. The thin casting alloy pieces are then thermally treated in hydrogen at a temperature of approximately 300°C. The pressure is then reduced so that the hydrogen is desorbed, and finally, the thin casting alloy pieces are thermally treated again at a temperature of approximately 500°C, removing the hydrogen from the thin casting alloy pieces. During the hydrogen decrepitation process, as the volume of the thin casting alloy pieces that have absorbed hydrogen increases, a number of cracks are created in the alloy, and the alloy is fractured.

[0079] Furthermore, a jet mill process or similar method is used to grind the hydrogen-decrepitated thin casting alloy pieces. These pieces are placed in a jet mill shredder and finely ground to an average particle size in the range of 1 µm to 4.5 µm using high pressure, for example, 0.6 MPa nitrogen, thus producing a powder. The smaller the average particle size of the powder, the greater the improvement in the coercivity of the sintered magnet. However, if the particle size is not significantly reduced, the powder surfaces become slightly oxidized, conversely decreasing the coercivity. "Method for manufacturing sintered magnets based on RTB-based rare earth elements"

[0080] Next, a method for manufacturing an RTB-based magnet using the RTB-based alloy obtained in the manner described above is described according to the embodiment.

[0081] Examples of the method for producing an RTB-based magnet according to this embodiment include a method in which 0.02 wt% to 0.03 wt% zinc stearate is added to the RTB-based alloy powder according to the present embodiment as a lubricant, the powder is press-molded using a molding machine in a transverse magnetic field or the like, sintered in a vacuum and then thermally treated.

[0082] If the powder is sintered in a range of 800°C to 1200°C, and more preferably in a range of 900°C to 1200°C, and then thermally treated in a range of 400°C to 800°C, the transition metal-rich phase in the RTB-based magnet is easily generated, and an RTB-based magnet with a greater coercive force can be obtained.

[0083] In this embodiment, if the preceding formula 1 is satisfied, the R2T 17 -phase is generated in the RTB-based alloy. It is assumed that the R2T 17 -phase is used as a starting material for the transition metal-rich phase in the thermal treatment of an RTB-based magnet obtained by sintering the alloy.

[0084] The heat treatment after sintering can be performed once, twice, or more often. For example, if the heat treatment after sintering is performed only once, it is preferably carried out in a temperature range of 500°C to 530°C. If the heat treatment after sintering is performed twice, it is preferably carried out at two temperatures, one in a range of 530°C to 800°C and the other in a range of 400°C to 500°C.

[0085] If the thermal treatment is carried out at two temperatures, it is assumed that an RTB-based magnet with improved coercivity can be obtained, as the generation of the transition metal-rich phase is accelerated as described below.

[0086] If the thermal treatment is carried out at two temperatures, in the first thermal treatment, in a range of 530°C to 800°C, the r-rich phase is converted into a liquid phase and rotates around the main phase (2-14-1 phase). Then, in the second thermal treatment, in a range of 400°C to 500°C, a reaction takes place in the r-rich phase, the 2-17 phase (R2T). 17 -phase) and the metallic element M is accelerated, and the formation of the transition metal-rich phase is accelerated.

[0087] Since an alloy with an amount of B satisfying the above formula 1 and 0.1 atomic% to 2.4 atomic% of the metallic element M is used as the RTB-based alloy, in the method for producing the RTB-based magnet according to this embodiment, the RTB-based magnet according to the invention, which consists of a sintered body comprising a main phase 11h, which is mainly R2Fe 14B contains, and includes a grain boundary phase containing more R than the main phase, wherein the grain boundary phase contains an R-rich phase with a concentration of all atoms of the rare earth elements of 70 atomic % or more and a transition metal-rich phase with a concentration of all atoms of the rare earth elements in a range of 25 atomic % to 35 atomic %.

[0088] If the type or quantity of the metallic element used in the RTB-based alloy according to this embodiment determines the volume ratio of the area containing the R2T 17-phase included, and the composition of the RTB-based alloy is adjusted to the aforementioned ranges, and the conditions, for example the sintering temperature or the thermal treatment after sintering, are adjusted, it is possible to adjust the volume fraction of the transition metal-rich phase in the RTB-based magnet to a preferred range of 0.005 vol-% to 3 vol-%.

[0089] Furthermore, an RTB-based magnet that suppresses the amount of Dy and has a defined coercivity suitable for practical use can be obtained by adjusting the volume fraction of the transition metal-rich phase in the RTB-based magnet.

[0090] Furthermore, it is assumed that the effect which improves the coercive force (Hcj) obtained in the RTB-based magnet according to the invention results from the formation of the transition-metal-rich phase, which contains a high Fe concentration in the grain boundary phase. The volume fraction of the transition-metal-rich phase contained in the RTB-based magnet according to the invention is preferably 0.005 vol% to 3 vol%, and more preferably 0.1 vol% to 2 vol%.

[0091] If the volume fraction of the transition-metal-rich phase is within the aforementioned range, the effect of enclosing the transition-metal-rich phase within the grain boundary phase, thereby improving the coercivity, can be achieved more effectively. In contrast, if the volume fraction of the transition-metal-rich phase is less than 0.1 vol%, there is a risk that the effect of improving the coercivity (Hcj) will be insufficient. Furthermore, if the volume fraction of the transition-metal-rich phase exceeds 3 vol%, adverse effects on the magnetic properties occur, such as a reduction in remanence (Br) or maximum energy product ((BH)max), which is not desirable.

[0092] The concentration of Fe atoms in the transition-metal-rich phase is preferably 50 atomic percent. If the concentration of Fe atoms in the transition-metal-rich phase is within the aforementioned range, the effect of the transition-metal-rich phase inclusion can be enhanced. In contrast to the above, if the concentration of Fe atoms in the transition-metal-rich phase is below the aforementioned range, there is a risk that the effect of the transition-metal-rich phase inclusion in the grain boundary phase, which improves the coercivity (Hcj), will be insufficient. Furthermore, if the concentration of Fe atoms in the transition-metal-rich phase is beyond the aforementioned range, there is a risk that the R2T 17 -phase or Fe may be deposited, adversely affecting the magnetic properties.

[0093] In the present invention, the volume fraction of the transition-metal-rich phase in the RTB-based magnet is investigated using a method described below. First, the RTB-based magnet is embedded in a conductive resin, a surface parallel to the orientation direction is cut, and the surface is mirror-polished. Then, the mirror-polished surface is observed using a backscattered electron image at a magnification of approximately 1500, and the main phase, the r-rich phase, and the transition-metal-rich phase are determined using contrast. Subsequently, the area fraction of the transition-metal-rich phase per cross-section is calculated, and the volume fraction is also calculated, assuming that the transition-metal-rich phase is spherical.

[0094] Since the RTB-based magnet according to this embodiment is formed by forming and sintering an RTB-based alloy with an amount of B / TRE satisfying the above formula 1 and 0.1 atomic% to 2.4 atomic% of the metallic element M, the grain boundary phase comprising the R-rich phase and the transition-metal-rich phase, and the transition-metal-rich phase having a lower concentration of rare earth elements and a higher concentration of Fe atoms than the R-rich phase, the RTB-based magnet has a lower amount of Dy and has a large coercivity and magnetic properties that are so excellent that it is a preferred material for motors.

[0095] In this embodiment, it is also possible to produce an RTB-based magnet with a higher concentration of Dy on the surface of the sintered magnet than in the magnet itself, by applying Dy metal or a Dy compound to the surface of the sintered RTB-based magnet, thermally treating the magnet, and diffusing Dy into the sintered magnet, thereby further improving the coercivity.

[0096] The RTB-based magnet with a higher concentration of Dy on the surface of the sintered magnet than within the magnet itself is specifically manufactured as follows. For example, the sintered RTB-based magnet is immersed in a coating fluid obtained by mixing a solvent such as ethanol and dysprosium fluoride (DyF3) in a predetermined ratio, thereby depositing the coating fluid onto the RTB-based magnet. Subsequently, a diffusion stage is performed, in which a two-stage thermal treatment is carried out on the RTB-based magnet to which the coating fluid has been applied.More precisely, a first thermal treatment is performed in which the RTB-based magnet, to which the coating fluid has been applied, is heated to a temperature of 900°C for approximately one hour in an argon atmosphere, and the RTB-based magnet, having undergone this first thermal treatment, is then cooled to room temperature. A second thermal treatment is then carried out in which the RTB-based magnet is again heated to a temperature of 500°C for approximately one hour in an argon atmosphere, and then cooled to room temperature.

[0097] In addition to the method described above, a method in which a metal is volatilized and a film of the volatilized metal is bonded to the surface of the magnet, a method in which an organic metal is decomposed so that a film is bonded to the surface, and the like, can be used as a method in which Dy metal or a Dy compound is bonded to the surface of the RTB-based sintered magnet.

[0098] Instead of Dy metal or a Dy compound, a Tb metal or a Tb compound can be bonded to the surface of the RTB-based sintered magnet and heat-treated. In this case, for example, if a coating fluid containing a Tb fluoride is applied to the surface of the RTB-based sintered magnet and heat-treated, causing Tb to diffuse into the sintered magnet, it is possible to obtain an RTB-based magnet with a higher concentration of Tb on the surface of the sintered magnet than in the magnet itself, and the coercivity can be further improved.

[0099] Furthermore, it is possible to further improve the coercive force by depositing metallic Dy or metallic Tb on the surface of the RTB-based magnet and thermally treating it, and then diffusing the Dy or Tb into the sintered magnet. Any of the aforementioned techniques can be employed in RTB-based magnets according to this embodiment without any adverse effect.

[0100] The coercivity (Hcj) of the RTB-based magnet is preferably higher. When the RTB-based magnet is used as a magnet in a power steering motor of an automobile or the like, the coercivity is preferably 1592 kA / m (20 kOe) or more, and when the RTB-based magnet is used as a magnet in a motor of an electric vehicle, the coercivity is preferably 2387 kA / m (30 kOe) or more. If the coercivity (Hcj) of the magnet in an electric vehicle motor is less than 2387 kA / m (30 kOe), there are cases where the heat resistance for the motor becomes insufficient. Second embodiment (not according to the invention)

[0101] In the first embodiment, the RTB-based magnet was manufactured using the RTB-based alloy containing the metallic element; in contrast to the first embodiment, in the second embodiment, the RTB-based magnet is manufactured by using an RTB-rare earth-based sintered magnet alloy material comprising a powder form of an RTB-based alloy not containing a metallic element and an additional element (hereinafter referred to as the "RTB-based alloy material").

[0102] If the RTB-based alloy material is shaped and sintered in the same way as in the first embodiment according to this embodiment, the RTB-based magnet according to the first embodiment can be obtained.

[0103] The RTB-based alloy material according to this embodiment is an RTB-based alloy material comprising an RTB-based alloy containing a rare-earth element R, a substantially Fe-containing transition metal T, B, and unavoidable impurities, wherein R constitutes 13 to 15 atomic percent, B constitutes 4.5 to 6.2 atomic percent, T is the remainder, the Dy content in all rare-earth elements is in the range of 0 to 65 atomic percent, and the following formula 1 is satisfied; and comprising an additional metal from a metallic element M containing one or more metals selected from Al, Ga, and Cu, or an alloy containing the metallic element M, wherein the metallic element M is present in a range of 0.1 to 2.4 atomic percent. 0.0049Dy+0.34≤B / TRE≤0.0049Dy+0.36 In formula 1, Dy represents the concentration (atomic %) of a Dy element, B represents the concentration (atomic %) of the boron element, and TRE represents the concentration (atomic %) of all rare earth elements.

[0104] The RTB-based alloy material of this embodiment can be produced in the same way as the RTB-based alloy of the first embodiment, by using the same RTB-based alloy as in the first embodiment, except that the alloy does not contain the metallic element M. Therefore, the RTB-based alloy contained in the RTB-based alloy material of this embodiment will not be described.

[0105] As with the RTB-based alloy of the first embodiment, in the RTB-based alloy contained in the RTB-based alloy material of this embodiment, the area fraction of the region containing the R2T 17-phase includes, preferably 0.1% to 50%, and more preferably 0.1% to 25%. If the area fraction of the region containing the R2T 17 -Phase, in the aforementioned area, the generation of the transition-metal-rich phase is effectively accelerated, and the RTB-based magnet, which contains a sufficient amount of the transition-metal-rich phase and has a large coercive force, can be obtained. If the area fraction of the region containing the R2T 17 -phase, 50% or more, there are cases where it is not possible to use R2T 17 -phase in the stage where the RTB-based magnet is manufactured, to be completely consumed, and there are cases where the coercivity or rectangularity of the RTB-based magnet is reduced.

[0106] Furthermore, in the RTB-based alloy contained in the RTB-based alloy material of this embodiment, also in the case where the area fraction of the region containing the R2T 17 -phase, in a range of 0.1% to 50%, since excellent comminutability can be achieved, the alloy is easily comminuted, and it is possible to process the alloy into fine particles with a grain diameter of about 2 µm.

[0107] The area fraction of the region that the R2T 17 -phase in the RTB-based alloy contained in the RTB-based alloy material of this embodiment can be obtained in the same way as in the RTB-based alloy of the first embodiment.

[0108] The additional metal contained in the RTB-based alloy material of this embodiment consists of a metallic element M containing one or more metals selected from Al, Ga, and Cu, or an alloy containing the metallic element M. The metallic element M is presumed to accelerate the generation of the transition-metal-rich phase during sintering and thermal treatment for the fabrication of the RTB-based magnet.

[0109] The metallic element M is present in the RTB-based alloy material in a concentration of 0.1 atomic percent to 2.4 atomic percent. A concentration of the metallic element M in the range of 0.7 atomic percent to 1.4 atomic percent is more preferred. Since the RTB-based alloy material of this embodiment contains 0.1 atomic percent to 2.4 atomic percent of the metallic element M, the RTB-based magnet, which contains the r-rich phase and the transition-metal-rich phase, can be obtained by sintering the alloy material.

[0110] One or more metals selected from Al, Ga and Cu, contained in the metallic element M, accelerate the generation of the transition metal-rich phase during the sintering and thermal treatment of the RTB-based magnet without adversely affecting the other magnetic properties, thereby effectively improving the coercivity (Hcj).

[0111] If the amount of metallic element M is less than 0.1 atomic percent, there is a risk that the effect accelerating the generation of the transition-metal-rich phase will be insufficient. Consequently, the transition-metal-rich phase will not form in the RTB-based magnet, and it will not be possible to adequately improve the coercivity (Hcj) of the RTB-based magnet. Furthermore, if the amount of metallic element M exceeds 2.4 atomic percent, the magnetic properties, such as the remanence (Br) of the RTB-based magnet or the maximum energy product (Bhmax), will deteriorate.

[0112] If the RTB-based alloy material contains copper, the copper concentration is preferably between 0.07 atomic percent and 1 atomic percent. If the copper concentration is less than 0.07 atomic percent, sintering the magnet becomes difficult. If the Cu concentration exceeds 1 atomic percent, the remanence (Br) of the RTB-based magnet is impaired, which is not preferred.

[0113] The RTB-based alloy material of this embodiment may also contain Si in addition to the RTB-based alloy and the additional metal. If the RTB-based alloy material contains Si, the amount of Si is preferably in the range of 0.07 atomic percent to 1.5 atomic percent. If the amount of Si is within the aforementioned range, the coercivity is further improved. The effect of including Si is weaker if the amount of Si is both less than 0.7 atomic percent and more than 1.5 atomic percent. "Process for producing the alloy material on an RTB basis"

[0114] The RTB-based alloy contained in the RTB-based alloy material can be produced in the same way as the RTB-based alloy of the first embodiment. Furthermore, the RTB-based alloy material can be obtained by mixing the powder of the obtained RTB-based alloy with the powder of the additional metal. "Method for producing the sintered rare earth-based magnet"

[0115] The RTB-based magnet can be manufactured by using the RTB-based alloy material of this embodiment, which is obtained in the same way as described above when using the RTB-based alloy of the first embodiment.

[0116] The grain size of the RTB-based alloy powder is specified in a range of 4 µm to 5 µm at d50 to improve the coercivity of the RTB-based magnet; however, if the grain size is further reduced to decrease the size of the grains in the RTB-based magnet, it is possible to further improve the coercivity.

[0117] Even in this embodiment, as in the first embodiment, it is possible to further improve the coercive force by applying a fluoride of Dy or Tb to the surface of the RTB-based magnet, thermally treating the fluoride, and diffusing the Dy or Tb into the sintered magnet. Furthermore, it is also possible to further improve the coercive force by applying Dy-metal or Tb-metal to the surface of the RTB-based magnet, thermally treating the magnet, and diffusing the Dy or Tb into the sintered magnet.

[0118] In the method for producing the RTB-based magnet of this embodiment, since an alloy material in which the amount of B satisfies the preceding formula 1 and the metallic element M is present in a concentration of 0.1 atomic% to 2.4 atomic% is used as the RTB-based alloy material, the RTB-based magnet can be obtained which consists of a sintered body comprising a mainly R2Fe 14 includes a main phase containing B and a grain boundary phase containing more R than the main phase, wherein the grain boundary phase includes the R-rich phase with a concentration of all atoms of the rare earth elements of 70 atomic % or more and the transition metal-rich phase with a concentration of all atoms of the rare earth elements in a range of 25 atomic % to 35 atomic %.

[0119] If the type or amount of metallic element M used in the RTB-based alloy of this embodiment is the volume fraction of the area comprising the R2T 17 By including the transition-metal-rich phase, adjusting the composition of the RTB-based alloy to the aforementioned ranges, and adjusting conditions such as the sintering temperature or post-sintering heat treatment, it is also possible to adjust the volume fraction of the transition-metal-rich phase in the RTB-based magnet to a preferred range of 0.005 vol.% to 3 vol.%. Furthermore, by adjusting the volume fraction of the transition-metal-rich phase in the RTB-based magnet, an RTB-based magnet that suppresses the amount of Dy and exhibits a predetermined coercivity suitable for practical use can be obtained.

[0120] Since the RTB-based magnet of this embodiment is formed by forming and sintering an RTB-based alloy material with an amount of B / TRE satisfying the above formula 1 and with 0.2 atomic% to 5 atomic% of the metallic element M, the grain boundary phase comprises the R-rich and the transition-metal-rich phase, and the transition-metal-rich phase has a lower concentration of all rare-earth element atoms than the R-rich phase and a higher concentration of Fe atoms than the R-rich phase, the RTB-based magnet suppresses the amount of Dy and has a large coercivity and magnetic properties that are excellent enough to be preferred as a material for motors. Third embodiment (not according to the invention)

[0121] In the second embodiment, the RTB-based alloy material was described, comprising the RTB-based powder containing no metallic element and the additional metal. However, this embodiment describes an RTB-based alloy material comprising an RTB-based alloy containing a metallic element and the additional metal. That is, the metallic element can be added to the RTB-based alloy material in a stage where the RTB-based alloy is cast, in a stage prior to sintering the RTB-based alloy, or in both stages.

[0122] In the third embodiment, a portion of the metallic element contained in the RTB-based alloy material is added to the RTB-based alloy, and the powder of the RTB-based alloy and the remainder of the metallic element are mixed, thereby producing an RTB-based alloy material, and an RTB-based magnet is manufactured using the RTB-based alloy material.

[0123] If the RTB-based alloy material of this embodiment is shaped and sintered in the same way as in the first and second embodiments, the RTB-based magnets of the first and second embodiments can be obtained.

[0124] The RTB-based alloy material of this embodiment is an RTB-based alloy comprising an RTB-based alloy containing a rare-earth element R, a substantially Fe-containing transition metal T, a first metal containing one or more metals selected from Al, Ga, and Cu, B, and unavoidable impurities, wherein R constitutes 13 to 15 atomic percent, B constitutes 4.5 to 6.2 atomic percent, T is the remainder, the proportion of Dy in all rare-earth elements is in a range of 0 to 65 atomic percent, and the following formula 1 is satisfied; and an additional metal comprising a second metal containing one or more metals selected from Al, Ga, and Cu, or an alloy containing the second metal, wherein the first metal and the second metal are present in a combined range of 0.1 to 2.4 atomic percent. 0.0049Dy+0.34≤B / TRE≤0.0049Dy+0.36 where in formula 1 Dy represents the concentration (Aotm-%) of a Dy element, B represents the concentration (Atom-%) of the boron element, and TRE represents the concentration (Atom-%) of all rare earth elements.

[0125] Both the first and the second metal are one or more metals selected from Al, Ga and Cu, and the same composition as the metallic element M in the first and second embodiments is formed by using the sum of the first and the second metal.

[0126] Furthermore, the sum of the first and second metals in the RTB-based alloy material is the same as the sums of the metallic element M in the first embodiment and the second embodiment.

[0127] The RTB-based alloy material of this embodiment is the same as the RTB-based alloy material of the second embodiment, except that the RTB-based alloy contains the first metal and the RTB-based magnet is the same as in the first and second embodiments. Therefore, the RTB-based material and the RTB-based magnet of this embodiment will not be described.

[0128] Here, a method for generating the transition metal-rich phase contained in the RTB-based magnet according to the invention will be described in detail.

[0129] It is assumed that in the present invention the R2T 17-phase, which is contained in the RTB-based alloy in the middle of its manufacture and / or in the RTB-based magnet in the middle of its manufacture, is used as a starting material for the transition metal-rich phase for the RTB-based magnet in the thermal treatment, which is carried out once or several times in a stage in which the RTB-based alloy is manufactured and / or in a stage in which the RTB-based magnet is manufactured, so that the transition metal-rich phase is generated.

[0130] The conditions of the thermal treatment that produce the transition metal-rich phase depend on the type and amount of the metallic element M used, which is combined with the R2T. 17 -phase is used as a starting material for the transition metal-rich phase, the amount of R2T produced 17-phase contained in the RTB-based alloy and / or the sintered RTB-based magnets, the composition of the RTB-based magnet, the amount of transition metal-rich phase produced, and the like.

[0131] The thermal treatment which generates the transition metal-rich phase can, more precisely, be carried out once or several times on the RTB-based alloy in the middle of its production and / or on the RTB-based magnet in the middle of its production at a temperature in the range of 400°C to 800°C, and more preferably in the range of 450°C to 650°C, and the thermal treatment is preferably carried out in the stage in which the RTB-based alloy is produced and / or in the stage in which the RTB-based magnet is produced, for a total of 0.5 hours to 5 hours, and more preferably for 1 to 3 hours.

[0132] If the temperature of the thermal treatment that produces the transition metal-rich phase is lower than 400°C, there are cases in which the reaction under the rare earth element M, the R2T 17 -phase (R2T 17 The transition metal-rich phase is not sufficiently generated if the concentration of atoms in the transition metal-rich phase and the metallic element M is insufficient during thermal treatment. If the temperature of the thermal treatment that generates the transition metal-rich phase exceeds 800°C, there are cases where atoms are rearranged in such a way that the transition metal-rich phase is not sufficiently generated.

[0133] Furthermore, if the total duration of the thermal treatment that produces the transition metal-rich phase is less than 0.5 hours, there are cases in which the reaction proceeds under the rare earth element R, the 2-17 phase (R2T). 17The concentration of the transition metal-rich phase (-phase) and the metallic element M during the thermal treatment becomes insufficient, and the transition metal-rich phase is not adequately generated. If the total duration of the thermal treatment that generates the transition metal-rich phase exceeds 5 hours, the thermal treatment is lengthy, thus adversely affecting productivity, which is undesirable.

[0134] The thermal treatment that generates the transition-metal-rich phase is performed once or several times in the stage where the RTB-based alloy is produced and / or in the stage where the RTB-based magnet is manufactured. The thermal treatment may be solely for the generation of the transition-metal-rich phase, or it may be performed in conjunction with a further thermal treatment for another purpose, such as sintering. The number of thermal treatments required to generate the transition-metal-rich phase is not particularly limited; however, the thermal treatment is preferably performed several times to generate a sufficient quantity of the transition-metal-rich phase.

[0135] The thermal treatment that generates the transition metal-rich phase may consist of one or more of the following selected treatments: a treatment (temperature conservation stage) in which the cooling rate of the thin cast alloy pieces after casting, which is carried out when the alloy is produced on an RTB basis, is temporarily slowed down to accelerate the diffusion of the components into the alloy; a thermal treatment to generate the transition metal-rich phase in the sintered RTB-based magnets; a thermal treatment to diffuse Dy or Tb into the sintered RTB-based magnets; and the like.

[0136] The thermal treatment that generates the transition-metal-rich phase is preferably carried out at a temperature in the range of 400 to 800°C. However, the optimal temperature within this range varies depending on the structural state of the RTB-based alloy or the RTB-based magnet undergoing thermal treatment. For example, the optimal temperature before sintering and the optimal temperature after sintering differ. Therefore, the optimal temperature is expediently determined by the stage at which the thermal treatment is performed, from the casting of the RTB-based alloy to the completion of the RTB-based magnet.

[0137] Furthermore, the amount of transition-metal-rich phase produced by the thermal treatment increases with the duration of the thermal treatment. However, if the temperature of the RTB-based alloy or the RTB-based magnet reaches the decomposition temperature of the transition-metal-rich phase, or a higher temperature in the stages following the thermal treatment, some or all of the generated transition-metal-rich phase may decompose and decrease.

[0138] In the thermal treatment that produces the transition metal-rich phase, it is assumed that the reactions of the following formula 3 and / or formula 4 proceed.

[0139] More precisely, it is assumed that if the metallic element M, which is used as the starting material for the transition metal-rich phase in the thermal treatment, is present only in the RTB-based alloy or the RTB-based magnet, which is the material to be thermally treated, then the reaction of the following formula 3 will proceed in the thermal treatment, which produces the transition metal-rich phase, and so on. R(rare earth element) + R2T17(R2T17− phase) + M(metallic element) → R6T13M(transition metal-rich phase)

[0140] Examples of the case where the metallic element M is only contained in a material to be thermally treated include thermal treatment for sintering, which is carried out when the RTB-based magnet is manufactured using the RTB-based alloy material, which contains the RTB-based alloy without a metallic element and with additional metal, and the like.

[0141] Furthermore, if the metallic element M is contained in the alloy grain boundary phase or the grain boundary phase in a material to be thermally treated, it is assumed that the reaction of the following formula 4 proceeds in the thermal treatment, which produces the transition metal-rich phase. RM (rare earth element, which contains the metallic element) + R2T17 (R2T17 phase) → R6T13M (transition metal-rich phase)

[0142] Examples of the case where the metallic element M is contained in the alloy grain boundary phase or the grain boundary phase in a material to be thermally treated include thermal treatment for sintering, which is carried out when the RTB-based magnet using the RTB-based alloy with the metallic element is manufactured, and the like.

[0143] When both a material containing exclusively the metallic element M and a material containing the metallic element in the alloy grain boundary phase or the grain boundary phase are thermally treated, the reaction of Formula 3 above and the reaction of Formula 4 are assumed to proceed simultaneously in the thermal treatment that produces the transition-metal-rich phase. Examples of the above case include a thermal treatment for sintering carried out when manufacturing the RTB-based magnet comprising the RTB-based alloy material containing the metallic element and the additional metal, and the like.

[0144] The size of the R2T 17 The -phase in the RTB-based alloy is preferably lower. If the R2T 17 If the -phase is large, it is not possible to use the R2T 17-phase completely removed, even if the reaction of formula 3 or formula 4 is caused, and there are cases where the R2T 17 -phase remains in the RTB-based magnet, thus affecting the coercivity or rectangularity. More precisely, the magnitude of the R2T 17 -phase preferably 10 µm or less and more preferably 3 µm or less. The size of the R2T 17 -phase refers to the size of a single R2T 17 -phase, and it is not the size of an area in which the R2T 17 -phase is present.

[0145] In the present invention, it is assumed that when the thermal treatment which generates the transition metal-rich phase is carried out, the transition metal-rich phase is generated in the RTB-based magnet by the R2T 17-phase and the rare earth element R, which contains the metallic element M (or the metallic element M and the rare earth element R), as described in Formula 3 and / or Formula 4, are used as starting materials. [Examples]“Experimental Examples 1 to 17 and 41 to 46”

[0146] Nd metal (purity: 99 wt.% or more), Pr metal (purity: 99 wt.% or more), Dy metal (purity: 99 wt.% or more), iron-boron (Fe 80 wt.%, B 20 wt.%), iron ingots (purity: 99 wt.% or more), Al metal (purity: 99 wt.% or more), Ga metal (purity: 99 wt.% or more), and Cu metal (purity: 99 wt.% or more) were weighed out to obtain the alloy compositions of alloys A to L, N to Q, and T to Z in Table 1. Additionally, 2.3 atomic percent Co metal (purity: 99 wt.% or more) was weighed out, and the components were placed in an alumina furnace.

[0147] The amounts of Si in the alloy compositions listed in Table 1 refer to the amounts of Si that are not intentionally added to the alloy but are present in the alloy as impurities. Furthermore, alloy N is an alloy produced with the intention of not adding any metallic element M; alloy O is an alloy produced with the intention of adding only Al as the metallic element M; alloy P is an alloy produced with the intention of adding only Ga as the metallic element M; and alloy Q is an alloy produced with the intention of adding only Cu as the metallic element M. Additionally, the Al contained in alloys N, P, and Q is an element that was not intentionally added but originates from the aluminum oxide furnace.

[0148] Subsequently, the interior of a high-frequency vacuum induction furnace, into which the aluminum oxide furnace had been placed, was filled with argon, heated to 1450°C to melt the components, the molten alloy was poured into a water-cooled copper roller and cast using a thin strip casting (SC) process at a roller rotation rate of 1.0 m / sec, resulting in an average thickness of about 0.3 mm and thus producing thin cast alloy pieces.

[0149] The thin cast alloy pieces were then cleaved using a hydrogen decrepitation process described below. First, the thin cast alloy pieces were coarsely cleaved to a diameter of approximately 5 mm and placed in a hydrogen atmosphere to absorb the hydrogen. Next, a thermal treatment was performed in which the coarsely cleaved pieces were heated to 300°C in a hydrogen atmosphere. Following this, a further thermal treatment was carried out in which the pressure was reduced to desorb the hydrogen, and the thin cast alloy pieces were heated to 500°C to release and remove the hydrogen. Finally, the thin cast alloy pieces were cooled to room temperature.

[0150] Zinc stearate (0.025 wt%) was then added to the hydrogen-decrepitated thin casting alloy pieces as a lubricant, and the hydrogen-decrepitated thin casting alloy pieces were finely ground to a mean particle size (d50) of 4.5 µm using a Hosokawa Micron (TM) 100 AFG jet mill and high-pressure nitrogen (0.6 MPa), resulting in a powdered RTB-based alloy.

[0151] The area fractions of the R2T 17 -Phases in alloys A to L, N to Q and T to Z, obtained in the manner described above, were investigated using the method described below.

[0152] A thin cast alloy piece with a thickness in the range of ±10% of its mean thickness was embedded in a resin, a cross-section was cut in the thickness direction, the cross-section was mirror-polished, and then gold or carbon was deposited to impart electrical conductivity, thus producing a viewing pattern. A backscattered electron image of the pattern was acquired at 350x magnification using a scanning electron microscope (JSM-5310, manufactured by JEOL LTD. (TM)).

[0153] Fig. Figure 6 illustrates the backscatter electron pattern of alloy F as an example. Furthermore, the area fractions of the R2T are shown. 17 The phases in the measured alloys under alloys A to L, N to Q, and T to Z are described in Table 4. In Table 4, the symbol “-” indicates that the area fraction of the corresponding alloy was not measured.

[0154] The RTB-based powdered alloy obtained in the manner described above was then formed using a machine in a transverse magnetic field at a forming pressure of 0.8 t / cm². 2 The material was press-molded to produce a green compact. This green compact was then sintered in a vacuum at a temperature between 900 and 1200°C. Following this, the green compact was thermally treated and cooled at two different temperatures of 800°C and 500°C, producing the RTB-based magnets of experimental examples 1 to 17 and experimental examples 41 to 46.

[0155] Furthermore, the magnetic properties of the respective RTB-based magnets obtained in experimental examples 1 to 17 and 41 to 46 were measured using a BH curve analyzer (TPM 2-10, manufactured by Toei Industry Co., Ltd.). The results are shown in Table 4. “Experimental Examples 18 to 33”

[0156] The RTB-based powdered alloys (alloys A to H, J to L, and N to Q) obtained in experimental examples 1 to 17, and the powdered alloy R and Si powder with a mean grain size (d50) of 4.35 µm, were prepared. The powdered alloy and the Si powder were mixed to obtain the composition of a sintered magnet described in Table 2, thereby producing the RTB-based alloy materials of experimental examples 18 to 33. The grain size of the Si powders was measured using a laser diffraction detector.

[0157] Subsequently, RTB-based magnets were produced in the same sequence as in experimental examples 1 to 15, using the RTB-based alloy materials obtained in the manner described above.

[0158] Furthermore, the magnetic properties of the respective RTB-based magnets obtained in experimental examples 18 to 33 were measured in the same manner as in experimental examples 1 to 17 using a BH curve meter (TPM 2-10, manufactured by Toei Industry Co., Ltd.). The results are shown in Table 5. “Experimental Example 34”

[0159] Nd metal (purity: 99 wt.% or more), Pr metal (purity: 99 wt.% or more), Dy metal (purity: 99 wt.% or more), iron-boron (Fe 80 wt.% B 20 wt.%), iron ingots (purity: 99 wt.% or more), Si metal (purity: 99 wt.% or more), Al metal (purity: 99 wt.% or more), Ga metal (purity: 99 wt.% or more) and Cu metal (purity: 99 wt.% or more) were weighed to obtain the alloy compositions of alloy S described in Table 3. In addition, 2.3 atomic percent of co-metal (purity: 99 wt.% or more) was weighed out, the compositions were placed in an aluminum oxide furnace, a powdered RTB-based alloy was obtained in the same sequence as in experimental examples 1 to 17, and an RTB-based magnet was produced in the same sequence as in experimental examples 1 to 17 using the powdered RTB-based alloy.

[0160] Furthermore, the RTB-based magnetic properties of the respective magnets obtained in experimental example 34 were measured in the same manner as in experimental examples 1 to 17 using a BH curve analyzer (TPM 2-10, manufactured by Toei Industry Co., Ltd.). The results are shown in Table 6. Table 1 Table 2 alloy Experimental example Composition of the sintered magnet (atomic %) Rinsges. Nd Pr Dy B Fe Si Ga Al Cu A 18 14,5 12,32 2,16 0,00 5,25 76,6 0,77 0,07 0,34 0,10 B 19 15,0 12,85 2,16 0,00 5,27 76,0 0,78 0,07 0,34 0,10 C 20 13,9 11,75 2,13 0,00 5,25 77,2 0,76 0,07 0,35 0,10 D 21 14,8 12,63 2,16 0,00 5,12 76,3 0,78 0,07 0,37 0,10 E 22* 13,7 7,54 2,26 3,86 5,18 77,5 0,76 0,07 0,33 0,07 F 23* 14,0 7,91 2,29 3,84 5,26 76,9 0,78 0,07 0,35 0,07 G 24* 14,8 8,53 2,31 3,93 5,35 76,2 0,79 0,07 0,36 0,07 H 25* 13,9 7,87 2,26 3,80 4,86 77,6 0,78 0,07 0,36 0,07 J 26* 13,7 3,18 2,23 8,24 5,36 76,5 1,50 0,07 0,36 0,07 K 27* 14,3 3,71 2,23 8,32 5,41 75,9 1,50 0,07 0,34 0,07 L 28* 13,2 2,71 2,23 8,19 5,30 77,2 1,48 0,07 0,33 0,07 R 29* 14,0 7,90 2,25 3,84 5,24 73,2 4,71 0,00 0,33 0,10 N 30* 14,6 8,31 2,29 3,97 5,46 79,6 0,81 0,00 0,08 0,00 O 31* 14,6 8,31 2,28 3,95 5,45 79,5 0,80 0,00 0,39 0,00 P 32* 14,6 8,31 2,28 3,95 5,43 79,6 0,80 0,07 0,07 0,00 Q 33* 14,6 8,33 2,28 4,00 5,50 79,4 0,80 0,00 0,01 0,07 * Reference example Table 3 alloy Experimental example Composition of the sintered magnet (atomic %) Rinsges. Nd Pr Dy B Fe Si Ga Al Cu S 34* 14,1 7,94 2,25 3,92 5,19 77,1 0,74 0,00 0,34 0,12 * Reference example Table 4 alloy Experimental example Area percentage of the region containing the 2-17 phase (%) Sq (%) (BH)max(MGOe) Br (T) Hcj(kA / m) Volume fraction of the transition metal-rich phase (%) A 1 0,00 94,8 46,5 1,39 833 - B 2 0,00 94,8 44,1 1,35 1186 - C 3 0,10 95,0 48,2 1,42 828 1,49 D 4 0,00 94,3 45,5 1,39 796 - E 5* - 94,3 33,7 1,17 2698 - F 6* 4,30 94,4 32,9 1,16 2920 0,64 G 7* - 93,1 31,9 1,14 2944 0,59 H 8* 87,50 88,9 29,3 1,15 2451 - I 9* 0,10 93,5 32,0 1,15 2300 - J 10* 33,10 89,0 20,7 0,92 3756 - K 11* 28,10 81,7 20,7 0,92 3151 - L 12* 87,50 82,5 20,8 0,93 3414 1,67 T 13* - 93,6 32,6 1,16 2379 0,00 N 14* 92,8 32,7 1,15 2093 - O 15* 93,6 31,0 1,12 2475 - P 16* 93,0 32,6 1,15 2324 - Q 17* - 94,3 31,6 1,13 2276 - U 41 - 93,1 41,7 1,32 1456 - V 42 - 93,5 42,7 1,33 1432 - w 43 - 93,2 41,1 1,31 1090 - X 44 - 94,9 42,1 1,32 1560 - Y 45 - 90,5 43,9 1,35 1480 - Z 46 - 93,8 45,0 1,37 1472 - * Reference example Table 5 alloy Experimental example Sq (%) (BH)max(MGOe) Br (T) Hcj(kA / m) Volume fraction of the transition metal-rich phase (%) A 18 94.0 43.7 1,35 1058 - B 19 94.6 38.9 1,27 1369 - C 20 93.8 44.2 1,36 1042 2.63 D 21 93.2 38.2 1,28 1122 - E 22* 93.4 33.1 1,16 2976 - F 23* 91.3 30.7 1,12 3072 1.27 G 24* 92.3 30.1 1,11 3032 0.78 H 25* 87.3 26.9 1,11 2578 - J 26* 89.7 19.7 0,89 3844 - K 27* 77.1 18.8 0,88 3581 - L 28* 88.7 19.9 0,91 3493 1.47 R 29* 89.7 22.4 0,98 2674 - N 30* 94.3 30.7 1,12 2308 - O 31* 92.3 29.6 1,10 2666 - P 32* 90,9 30,8 1,12 2451 - Q 33* 94,3 30,3 1,10 3207 - * Reference example Table 6 alloy Experimental example Area fraction of the area containing the 2-17 phase Sq (%) (BH)max(MGOe) Br (T) Hcj(kA / m) Volume fraction of the transition metal-rich phase (%) S 34* - 92,9 31,4 1,13 2849 0,19 * Reference example

[0161] In Tables 4 to 6, "Hcj" represents the coercive force, "Br" represents the remanence, "Sq" represents the rectangularity, and "BHmax" represents the maximum energy product, where 1 MG = 100 T and 1Oe = 79.577 A / m. Furthermore, these magnetic properties are the mean values ​​of measured values ​​from five magnets based on RTB (Real-Time Beam Test).

[0162] In addition, the volume fractions of the transition metal-rich phases in the RTB-based magnets of experimental examples 3 to 28 and 34 were investigated using the method described below.

[0163] The RTB-based magnet was embedded in a conductive resin, a surface was cut parallel to the orientation direction and mirror-polished. The surface was observed using backscattered electron imaging at approximately 1500x magnification, and the main phase, the r-rich phase, and the transition-metal-rich phase were determined using contrast imaging.

[0164] For example, the Fig. 9 and Fig. 10(a) Backscattered electron images of the RTB-based magnets obtained in experimental examples 6 and 23. Fig. 9 and Fig. 10(a) show that white R-rich phases and slightly grey transition metal-rich phases are found in the grain boundaries of the grey R2T 14 B-phases are present.

[0165] The area fraction of the transition metal-rich phases per cross-section was calculated using the backscattered electron image, and the volume fractions of the respective experimental examples were also calculated under the assumption that the transition metal-rich phase is spherical.

[0166] The results are described in Tables 4 to 6. In Tables 4 to 6, the symbol “-” indicates that the area fraction of the respective alloy was not measured.

[0167] Furthermore, it was confirmed that the RTB-based magnets of experimental examples 18 to 34 were mainly made from R2Fe 14 The compositions of the main phase containing B, the R-rich phase and the transition metal-rich phase were investigated using electron probe microanalysis (FE-EPMA).

[0168] As described in Tables 1 and 4, in experimental examples 8 and 9, where B does not satisfy formula 1, the amounts of Dy are essentially the same, and the coercive forces (Hcj) are lower than those in experimental example 6, where B satisfies formula 1.

[0169] In experimental example 23, wherein the amount of Si added is in a range of 0.7 atomic % to 1.5 atomic %, the coercive force (Hcj) is greater than that in experimental example 29, wherein the amount of metal added exceeds the upper limit of the invention.

[0170] Furthermore, Fig.Figure 1 shows the relationship between B / TRE (where B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements) and the coercive force (Hcj) of experimental examples 1 to 4 and 18 to 21. While the RTB-based magnets of experimental examples 1 to 4 and 18 to 21 do not contain Dy, the addition of Si, which is the additional metal (experimental examples 18 to 21), increases the coercive force (Hcj), as illustrated in experimental examples 18 to 21.

[0171] At this point, the estimated optimal width of B / TRE is approximately ±0.1 with respect to the peak.

[0172] Furthermore, Fig.Figure 2 shows a graph illustrating the relationships between B / TRE (where B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements) and the coercive force (Hcj) of experimental examples 5 to 9 and 22 to 25. The RTB-based magnets of experimental examples 5 to 9 and 22 to 25 contain approximately 3.8 atomic % Dy. The coercive forces differ due to the varying amounts of B / TRE, and the coercive forces are at a maximum when B / TRE is 0.37. Furthermore, it was found that the addition of Si, which is the additional metal (experimental examples 22 to 25), increases the coercive force, as illustrated in experimental examples 22 to 25. At this point, the estimated optimal width of B / TRE is approximately ±0.1 with respect to the peak.

[0173] Furthermore, Fig.Figure 3 shows the relationship between B / TRE (where B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements) and the coercive force (Hcj) of experimental examples 10 to 12 and 26 to 28. The RTB-based magnets of experimental examples 10 to 12 and 26 to 28 contain approximately 8.3 atomic % Dy. The coercive forces differ due to the varying amounts of B / TRE, and the coercive forces are at a maximum when B / TRE is 0.39.

[0174] Furthermore, it was found that the amount of Si, which is the additional metal (experimental examples 24 to 26), increases the coercive force. At this point, the estimated optimal width of B / TRE is approximately ±0.1 with respect to the peak.

[0175] Experimental example 14 is an alloy prepared without the addition of Cu, Al, Ga, and Si, and has a significantly lower coercive force than experimental example 6, which has a very similar composition to experimental example 14. In experimental example 15, prepared by adding only Al to the components of experimental example 14, in experimental example 16, prepared by adding only Ga to the components of experimental example 14, and in experimental example 17, prepared by adding only Cu to the components of experimental example 14, the coercive forces are greater than in experimental example 14. This shows that any element selected from Al, Ga, and Cu is essential for increasing the coercive force.

[0176] Furthermore, in experimental examples 30 to 33, which were prepared by adding Si to alloys N to Q, the coercive forces are increased, indicating that the addition of two or more metals M is preferred. In particular, a significant improvement in the coercive force is observed in experimental example 33, which was prepared by adding Si powder to alloy Q. Moreover, in experimental example 33, the coercive force is 159 kA / m (2 kOe) or greater than that in experimental example 24 with a similar composition, indicating that the addition of Cu and Si is particularly preferred.

[0177] When comparing experimental examples 14 to 17, which have essentially the same concentrations of Dy, the coercive force in experimental example 14, in which the concentration of the metallic element M is 0.08 atomic %, is small, while the coercive forces in experimental examples 15 to 17, in which the concentrations of the metallic element M are 0.1 atomic % or more, are large.

[0178] When comparing experimental examples 41 to 46, which do not contain Dy, the coercive force in experimental example 43 (the concentration of the metallic element M is 2.43 atomic %) is lower than that in experimental example 41 (the concentration of the metallic element M is 0.75 atomic %) and experimental example 42 (the concentration of the metallic element M is 1.00 atomic %).

[0179] The above description shows that the amount of the metallic element M is preferably in the range of 0.1 atomic % to 2.4 atomic %.

[0180] Among experimental examples 1 to 4 and 41 to 46, which do not contain Dy, the coercive forces in experimental examples 41, 42, and 44 to 46 are large (the concentration of the metallic element M is in the range of 0.72 atomic percent to 1.34 atomic percent). The foregoing indicates that the amount of the metallic element M is preferably in the range of 0.7 atomic percent to 1.4 atomic percent.

[0181] Experimental Example 34, described in Tables 3 and 6, is an alloy produced by adding all metallic elements during the alloy casting stage. When Experimental Example 34 is compared with Experimental Example 5 in Tables 1 to 4, which have essentially the same amounts of Dy, it is found that Experimental Example 34 exhibits a greater coercive force than Experimental Example 5.

[0182] The results in Tables 1 to 6 show that both when the metallic elements are cast as an alloy and when the alloy and the additional metal are mixed, the effect of improving the coercive force of the magnet can be achieved.

[0183] The Fig. Figures 8 to 10(a) are microscope photographs of the RTB-based magnets. Fig.Figure 8 is a backscattered electron image of experimental example 9. Fig. Figure 9 is a backscattered electron image of experimental example 6, and Fig. Figure 10(a) is a backscattered electron image of experimental example 23. In addition, Fig. 10(b) a schematic view to describe the microscope photograph of the in Fig. 10(a) shown RTB-based magnets. In the backscattered electron images in the Fig. 8 to 10(a) and the one in Fig. In the schematic view shown in 10(b), grey sections are the R2T. 14 B-phase, the white sections are the R-rich phase, and the light grey sections are the transition metal-rich phase.

[0184] Tables 1 and 2 show that the RTB-based magnets of experimental examples 6, 9, and 23 have essentially the same amounts of Dy. B / TRE of experimental example 9 is outside the scope of the invention. Experimental example 23 is an alloy prepared by adding Si to experimental example 6. Fig. 8. The generated transition-metal-rich phase is hardly observed. It was found that in Fig. 9 only a small amount of the generated transition metal-rich phase is observed and in Fig. 10(a) a larger quantity of the transition metal-rich phase is produced. Fig. Equations 8 to 10(a) showed that if B / TRE is appropriately selected and the additional metal is appropriately added, it is possible to increase the production of the transition metal-rich phase.

[0185] In Fig.In step 8, several crushed particles are melted to form the main phase. Fig. 9. The crushed particles are not mixed and form the main phases individually. In Fig. 10(a) a form can be observed in which the main phases formed from the respective crushed particles are surrounded by grain boundary phases. “Experimental Example 35” (reference example)

[0186] Nd metal (purity: 99 wt.% or more), Pr metal (purity: 99 wt.% or more), Dy metal (purity: 99 wt.% or more), Al metal (purity: 99 wt.% or more), iron-boron (Fe 80 wt.% B 20 wt.%), iron ingots (purity: 99 wt.% or more), Ga metal (purity: 99 wt.% or more), Cu metal (purity: 99 wt.% or more) and Co metal (purity: 99 wt.% or more) were weighed to obtain the alloy compositions of alloy S described in Table 7 and were placed in an aluminum oxide furnace. Table 7 Nd Pr Dy Al Fe Ga Cu Co B 10,0 3,4 0,6 0,5 bal. 0,1 0,1 0,6 5,2

[0187] After that, thin cast alloy pieces were produced (casting stage) by pouring the in Fig. Figure 11 illustrates the production apparatus 1 used for an alloy. First, the interior of a high-frequency vacuum induction furnace (melting apparatus), into which the aluminum oxide furnace had been placed, was filled with argon and heated to 1450°C, resulting in a molten alloy. The molten alloy was then poured onto a water-cooled rotating copper roller at a rotation rate of 1.0 m / sec and solidified, producing a casting alloy. The casting alloy was then removed from the cooling roller 22 and placed between the crushing rollers in the crushing apparatus 21, where it was crushed to obtain thin casting alloy pieces with an average thickness of 0.3 mm. The casting stage was carried out in an argon atmosphere.

[0188] The crushed thin pieces of casting alloy were given through the hopper 7, piled onto the platforms 33, which could be opened and were in a “closed” state, heated using the heater 31, a temperature maintenance stage was carried out in which the 800°C hot casting alloy was kept at a certain temperature for 60 seconds, and the platforms 33, which could be opened, were moved to the “open” state, thus completing the temperature maintenance stage.

[0189] The thin cast alloy piece of experimental example 35, obtained in the manner described above, was embedded in a resin. A mirror-polished cross-section was observed using a backscattered electron image at 350x magnification. The main phase and the alloy grain boundary phase were determined using contrast, and the distances between adjacent alloy grain boundary phases were investigated as follows: Straight lines were drawn at 10 µm intervals parallel to the casting surface on the respective 350x magnified backscattered images of the thin cast alloy pieces of experimental example 35. The distances between the alloy grain boundary phases perpendicular to the straight lines were measured, and their mean value was calculated. Decreasing the distance between adjacent alloy grain boundary phases improved the comminutability.

[0190] Furthermore, a large number of thin cast alloy pieces, identical to the thin cast alloy pieces of experimental example 35 except that the concentrations of the boron and iron elements in the alloy compositions described in Table 7 were changed, were produced, and the distances between adjacent alloy grain boundary phases were determined in the same way as those of the thin cast alloy pieces of experimental example 35. The results are presented in the Fig. shown in 12(a) to 12(c), 13(a) and 13(b).

[0191] Fig. Figure 12(a) is a graph illustrating the relationship between the distance between the alloy grain boundary phases and the concentration of B in the thin cast alloy pieces. Fig.Figure 12(b) is a graph illustrating the relationship between the distance between the alloy grain boundary phases and B / TRE (B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements) in the thin cast alloy pieces, and Fig. Figure 12(c) is a graph illustrating the relationship between the distance between the alloy grain boundary phases and Fe / B (the ratio of the amount of Fe to the amount of B (B represents the concentration (atomic %) of the boron element and Fe represents the concentration (atomic %) of the iron element)) in the thin cast alloy pieces.

[0192] Fig. Equation 12(a) shows that when the amount of B is in the range of 5.0 atomic percent to 6.0 atomic percent, the distances between the alloy grain boundary phases are short and the grains become fine. Furthermore, it was found that when the amount of B falls below 5.0 atomic percent, the distances between the alloy grain boundary phases abruptly widen.

[0193] Fig. Figure 12(b) shows that when B / TRE is in the range of 0.355 to 0.38, the distances between the alloy grain boundary phases are short and the grains become fine. Furthermore, it was found that when B / TRE falls below 0.355, the distances between the alloy grain boundary phases abruptly increase.

[0194] Fig. 13(a) is a microscopic photograph of a cross-section of a thin cast alloy piece, wherein Fe / B is 15.5, and Fig. Figure 13(b) is a microscopic photograph of a cross-section of a thin cast alloy piece, in which Fe / B is 16.4. In the Fig. 13(a) and Fig. In the backscattered electron images illustrated in Figure 13(b), gray sections represent the main phase and white sections represent the alloy grain boundary phase. It was found that in the thin cast alloy piece of the Fig. 13(a) the alloy grain boundary phases form a fine, net-like structure. In contrast, in the Fig.13(b) illustrated needle-like alloy grain boundary phases and island-like main phases were observed in a thin cast alloy piece.

[0195] Fig. Figure 12 shows that when the Fe / B ratio exceeds 13, the distances between the alloy grain boundary phases become narrow, and the distance between the alloy grain boundary phases becomes particularly small when the Fe / B ratio is in the range of 15 to 16. Furthermore, the Fig. 12, Fig. 13(a) and Fig. 13(b) that when the Fe / B ratio is in the range of 13 to 16, the distances between the alloy grain boundary phases become short and the grains become finer compared to the case where the Fe / B ratio exceeds 16. Furthermore, it shows Fig. 12(c) that when Fe / B exceeds 16, the distances between the alloy grain boundary phases become abruptly larger. “Experimental Example 36” (reference example)

[0196] Thin cast alloy pieces were produced in the same manner (casting stage) as in experimental example 35, except that the components were weighed to obtain an alloy composition according to Table 7, the components were placed in an alumina furnace, and the atmosphere during the casting stage was set to the following atmosphere, wherein the in Fig. 11 Production apparatus 1 shown was used for an alloy.

[0197] The casting stage was carried out while helium was directed to an argon atmosphere, the casting alloy was cooled in a helium-containing atmosphere using the cooling roller 22, and after the temperature maintenance step, the thin casting alloy pieces, which were in the storage container 4, were cooled in the helium-containing atmosphere.

[0198] Using the thin cast alloy pieces of experimental example 36, obtained in the manner described above, the distances between adjacent alloy grain boundary phases were investigated in the same way as in experimental example 35. The results of the investigation of the distances between adjacent alloy grain boundaries of experimental examples 35 and 36 are presented in Fig. 14 shown. In Fig. 14, a black Δ indicates the results of experimental example 35, and • indicates the results of experimental example 36.

[0199] The in Fig.Graph 14 illustrates the results obtained by producing five thin cast alloy pieces of both experimental example 35 and experimental example 36, measuring the distances between the alloy grain boundary phases in the same way as described above, classifying the measured values ​​of the respective distances between the alloy grain boundary phases every 0.2 µm, and calculating the ratios of the number of measured values ​​occurring in the respective areas to the total number of measured values ​​of the distances between the alloy grain boundary phases ((number of measured values ​​occurring in each area / total number of measured values) x 100 (%)).

[0200] Fig.Figure 14 shows that in experimental example 36, where the thin casting alloy pieces were used for which the casting step was carried out in a helium-containing atmosphere, the distances between the alloy grain boundaries became small compared to experimental example 35, which used the thin casting alloy pieces with which the casting step was carried out in an argon atmosphere. The foregoing shows that when the casting step is carried out in a helium-containing atmosphere, the grain diameters in the alloy structure become small and excellent comminution can be achieved. “Experimental Example 37” (reference example)

[0201] Thin cast alloy pieces were produced in the same manner (casting stage) as in experimental example 35, except that the components were weighed to obtain the alloy composition of alloy F shown in Table 1, the components were placed in an aluminum oxide furnace, and the cooling temperature profile, while the temperature of the produced cast alloy reached 50°C from 1200°C, was monitored according to the parameters shown in the table. Fig. 15(a) to 15(c) and Table 8 illustrate condition (a) using the Fig. 11 production apparatus shown 1 for an alloy. Table 8 condition (a) condition (b) Temperature (°C) Time (seconds) Elapsed time (seconds) Cooling rate (°C / sec.) Temperature (°C) Time (seconds) Elapsed time (seconds) Cooling rate (°C / sec.) 1200 0 1200 0,0 900 0,3 0,3 1000 900 0,3 0,3 1000 700 0,5 0,8 400 800 0,25 0,6 400 600 50 50,8 2 800 0 60,6 0 50 550 600,8 1 600 100 160,6 2 50 550 710,6 1

[0202] The thin cast alloy pieces were then comminuted using the hydrogen decrepitation process in the same manner as in experimental example 1, yielding a powdered RTB-based alloy of experimental example 37. The mean particle size (d50) of the RTB-based powdered alloy was 4.5 µm.

[0203] The RTB-based powdered alloy of experimental example 37, obtained in the manner described above, was formed using a machine for forming in a transverse magnetic field at a forming pressure of 0.8 t / cm². 2The material was press-molded to obtain a green compact. This green compact was then sintered in a vacuum at a temperature between 900°C and 1200°C. Following this, the green compact underwent thermal treatment and cooling at two temperatures of 800°C and 500°C, resulting in the fabrication of a large number of RTB-based magnets of experimental example 37.

[0204] The magnetic properties of the multitude of RTB-based magnets obtained from experimental example 37 were each measured using a BH curve measuring device (TPM 2-10, manufactured by Toei Industry Co., Ltd.). The results are presented in the Fig. 16(a) to 16(c) are given. “Experimental Example 38” (reference example)

[0205] Thin cast alloy pieces were produced in the same way as in experimental example 37, except that the cooling temperature profile, while the temperature of the produced cast alloy reached 50°C from 1200°C, was followed as in the Fig. Condition (b) shown in 15(a) to 15(c) and Table 8 was established, and a powdered RTB-based alloy of experimental example 38 was obtained in the same way as in experimental example 37 using the thin cast alloy pieces.

[0206] The mean grain size (d50) of the RTB-based powdered alloy was 4.5 µm.

[0207] A plurality of RTB-based magnets of experimental example 38 were prepared in the same manner as in experimental example 37, using the RTB-based powder alloy of experimental example 38 obtained in the manner described above, and the magnetic properties of the plurality of obtained RTB-based magnets of experimental example 38 were each measured using a BH curve meter (TPM 2-10, manufactured by Toei Industry Co., Ltd.). The results are presented in the Fig. shown in 16(a) to 16(c). “Experimental Example 39” (reference example)

[0208] A powder of the RTB-based alloy obtained in experimental example 37 and a silicon powder with a mean grain size (d50) of 4.35 µm were prepared and mixed to obtain the composition of experimental example 23 as described in Table 2, thereby producing an RTB-based alloy material of experimental example 39. The grain size of the silicon powder was measured using a laser diffraction detector. “Experimental Example 40” (reference example)

[0209] A powder of the RTB-based alloy obtained in experimental example 38 and a silicon powder with a mean grain size (d50) of 4.35 µm were prepared and mixed to obtain the composition of experimental example 23 shown in Table 2, thereby producing an RTB-based alloy material of experimental example 40. The grain size of the silicon powder was measured using a laser diffraction detector.

[0210] Then, a plurality of RTB-based magnets of experimental example 39 and a plurality of RTB-based magnets of experimental example 40 were each measured in the same manner as in experimental example 37, using the RTB-based alloy materials of experimental examples 39 and 40 obtained as described above.

[0211] Furthermore, the magnetic properties of a large number of the obtained RTB-based magnets from experimental examples 39 and 40 were measured using a BH curve measuring device (TPM 2-10, manufactured by Toei Industry Co., Ltd.) in the same manner as in experimental example 37. The results are presented in the Fig. shown in 16(a) to 16(c).

[0212] Fig. Figure 16(a) is a graph illustrating the RTB-based coercive forces (Hcj) of the magnets from experimental examples 37 to 40. Fig. Figure 16(b) is a graph illustrating the RTB-based remanence (Br) of the magnets of experimental examples 37 to 40, and Fig. Figure 16(c) is a graph showing the relationship between the remanence (Br) and the coercive forces (Hcj) of the magnets on an RTB basis from experimental examples 37 to 40. Fig. The dashed line shown in 16(c) represents an equivalent line. Furthermore, in Fig.16 Δ indicates the results of experimental example 37, o indicates the results of experimental example 38, a black Δ indicates the results of experimental example 39 a and • indicates the results of experimental example 40. Fig.Figure 16a shows that the coercive forces (Hcj) in experimental examples 38 and 40, in which the temperature conservation step was carried out to maintain the 800°C hot cast alloy at a specific temperature for 60 seconds, are greater than in experimental examples 37 and 39, in which the temperature conservation step was not carried out. Furthermore, the coercive force (Hcj) in the RTB-based magnet of experimental example 40, which used the silicon-doped RTB-based alloy material, was greater than in the RTB-based magnet of experimental example 38, which used the RTB-based alloy material to which no silicon had been added.

[0213] Fig.16(b) shows that the remanence (Br) differences were small when comparing experimental examples 38 and 40, in which the temperature conservation step was carried out, and experimental examples 37 and 39, in which the temperature conservation step was not carried out, and when comparing the RTB-based magnets of experimental examples 39 and 40, in which the RTB-based alloy material containing Si was used, and the RTB-based magnets of experimental examples 37 and 38, in which the RTB-based alloy material to which no Si had been added was used.

[0214] Fig. 16(c) shows that experimental examples 38 and 40, in which the temperature conservation step was carried out, are located on the right side of the equivalent line and have a greater coercive force than the cases in which the temperature conservation step was not carried out. “Experimental Example 47”

[0215] The RTB-based powdered alloy produced to provide the composition of the sintered magnet of experimental example 47 described in Table 9 was formed using a machine for forming in a transverse magnetic field at a forming pressure of 0.8 t / cm². 2 The resulting green compact was press-molded. This green compact was then sintered in a vacuum at a temperature between 900 and 1200°C. The green compact was then thermally treated and cooled at two different temperatures of 800°C and 500°C, producing the RTB-based magnets of experimental example 47. Table 9 Experimental example Magnetic composition (atomic %) R total. Nd Pr Dy B Fe Si Ga Al Cu M 47 14,8 11,05 3,79 0,00 5,62 77,8 0,08 0,54 0,49 0,21 1,2 48* 14,9 11,05 3,79 0,10 5,62 77,8 0,08 0,54 0,49 0,21 1,2 49 14,1 13,96 0,14 0,00 5,77 80,2 0,00 0,23 0,20 0,09 0,5 50* 14,1 13,96 0,14 0,03 5,77 80,2 0,00 0,23 0,20 0,09 0,5 * Reference example “Experimental Example 48” (reference example)

[0216] A coating fluid containing dysprosium fluoride (DyF3) was applied to the surface of a thermally treated RTB-based magnet prepared in the same manner as in experimental example 47. The DyF3 coating fluid was a mixture obtained by mixing ethanol and dysprosium fluoride (DyF3) at a weight ratio of 1:1. The coating fluid was applied to the surface of the RTB-based magnet by immersing the sintered RTB-based magnet in a container for one minute while the coating fluid was ultrasonically dispersed within the container.

[0217] The first thermal treatment, in which the RTB-based magnet, to which the coating fluid had been applied, was heated at 900°C for one hour in an argon atmosphere into which argon was introduced at a flow rate of 100 ml / min, was then cooled to room temperature. The second thermal treatment, in which the RTB-based magnet was heated at 500°C for one hour in the same atmosphere as in the first thermal treatment, was then cooled to room temperature (diffusion stage), resulting in an RTB-based magnet of experimental example 48. “Experimental Example 49”

[0218] An RTB-based magnet of experimental example 49 was obtained in the same manner as in experimental example 47, except that a powdered RTB-based alloy prepared to provide the composition of the sintered magnet of experimental example 49 described in Table 9 was used. “Experimental Example 50” (reference example)

[0219] A diffusion step was carried out in which a Dy-containing coating fluid was applied to a surface of a thermally treated RTB-based magnet produced in the same manner as in experimental example 49, in the same manner as in experimental example 48, thereby obtaining an RTB-based magnet of experimental example 50.

[0220] Regarding the compositions of the RTB-based magnets of experimental examples 47 to 50 obtained in the manner described above, the rare-earth elements iron, copper, cobalt, aluminum, gallium, and boron were measured using X-ray fluorescence (XRF) analysis; carbon, nitrogen, and oxygen were measured using a gas analyzer; and other impurity elements present in small amounts were measured using induction-coupling plasma emission (ICP) spectrometry. The results are shown in Table 9. A comparison of experimental examples 47 and 48 in Table 9 shows that when the diffusion step, in which a thermal treatment is carried out by applying the Dy-containing coating fluid, is completed, the concentration of Dy in the RTB-based magnet is increased.Furthermore, when comparing experimental examples 49 and 50 in Table 9, the concentrations of Dy in the RTB-based magnets are increased when the diffusion step is performed.

[0221] Furthermore, the RTB-based magnets of experimental examples 47 and 48 were each encased in a conductive resin, a surface parallel to the orientation direction was cut out and mirror-polished. The surface was observed using backscattered electron imaging at approximately 1500x magnification, and the main phase, the r-rich phase, and the transition-metal-rich phase were determined using contrast imaging.

[0222] Furthermore, for the RTB-based magnets of experimental examples 47 and 48, the compositions of the main phase and the grain boundary phase (the R-rich phase and the transition metal-rich phase) were confirmed using an electron probe microanalyzer (FE-EPMA).

[0223] As a result, the RTB-based magnets of experimental examples 47 and 48 contained the main phase, the R-rich phase and the transition metal-rich phase.

[0224] Furthermore, the magnetic properties of the magnets in experimental examples 47 to 50 were measured on an RTB basis using a BH curve measuring device (TPM 2-10, manufactured by Toei Industry Co., Ltd.). The results are presented in the Fig. 17(a) and Fig. 17(b) and shown in Tables 10 and 11. [Table 10] Experimental Example 47 Experimental Example 48* Difference Br (T) 1,367 1,352 -0,015 Hcj (kA / m) 1390 1783 394 [Table 11] Experimental Example 49 Experimental example 50* Difference Br (T) 1,484 1,472 -0,013 Hcj (kA / m) 933 1117 185 * Reference example

[0225] In Tables 10 and 11, "Hcj" represents the coercive force, and "Br" represents the remanence. Furthermore, these magnetic properties are the mean of measured values ​​from five magnets each, based on RTB measurements.

[0226] Fig. Figure 17(a) is a graph illustrating the second quadrants of the hysteresis curves of experimental examples 47 and 48, and Fig. Figure 17B is a graph illustrating the second quadrants of the hysteresis curves from experimental examples 49 and 50. The vertical axis represents the magnetization J, and the horizontal axis represents the magnetic fields H. The values ​​in the Fig. 17(a) and Fig. The hysteresis curves shown in Figure 17(b) were measured using a BH curve measuring device (TPM 2-10, manufactured by Toei Industry Co., Ltd.). Fig. 17(a) and Fig.17(b) The points where the curves intersect the horizontal axes give the values ​​of the coercive force (Hcj), and the points where the curves intersect the vertical axes give the values ​​of the remanence “Br”.

[0227] Fig. Figure 17(a) and Table 10 show that the coercive force in experimental example 48, in which the diffusion step was carried out, was significantly increased compared to experimental example 47. Furthermore, when comparing experimental examples 47 and 48, the remanence is slightly altered.

[0228] Fig. Figure 17(b) and Table 11 show that the coercive force in experimental example 50, in which the diffusion step was carried out, was increased compared to experimental example 49, but the change is smaller than the difference between experimental examples 47 and 48 in Fig.17(a) and Table 10, and that the effect which increases the coercive force is small. In addition, when comparing experimental examples 50 and 49, the remanence is slightly changed. INDUSTRIAL APPLICABILITY

[0229] The invention can be applied to an alloy for sintered magnets based on RTB rare earth and an alloy material for sintered magnets based on RTB rare earth, which have excellent magnetic properties and from which sintered magnets based on RTB rare earth, which are a preferred material for motors, can be obtained. Reference symbol list 1 Production apparatus 2 Casting apparatus 3 Heating appliance 4 storage containers 5 containers 6th Chamber 6a Casting chamber 6b Heat retention and storage chamber 7 funnels 21. Crushing apparatus 31 stokers 32 groups of platforms that can be opened 33 platforms that can be opened

Claims

[1] Alloy for sintered magnets based on RTB rare earth elements, the alloy comprising: a rare earth element R, selected from Nd and Pr; a transition metal T essentially comprising Fe; a metallic element M, which is Ga or Ga and one or more metals selected from Al and Cu; B; and unavoidable impurities, wherein R constitutes 13 atomic % to 15 atomic %, B constitutes 4.5 atomic % to 6.2 atomic %, M constitutes 0.1 atomic % to 2.4 atomic %, Ga constitutes 0.07 atomic % to 1.95 atomic %, T constitutes the remainder and the following formula 1 is satisfied, 0.34≤B / TRE≤0.36 where B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements. [2] Alloy for sintered magnets based on RTB rare earth elements according to claim 1, wherein M comprises 0.7 atomic % to 1.4 atomic %. [3] Alloy for sintered magnets based on RTB rare earth according to claim 1 or 2, which also contains Si. [4] Alloy for sintered magnets based on RTB rare earth elements according to claim 1 or 2, wherein the area ratio of a region comprising an R2T 17 -phase, which ranges from 0.1% to 50%. [5] Sintered RTB rare earth-based magnet comprising: a rare earth element R, selected from Nd and Pr; a transition metal T containing essentially Fe; a metallic element M, which is Ga or Ga and one or more metals selected from Al and Cu; B; and unavoidable impurities, where R accounts for 13 to 15 atomic percent, B for 4.5 to 6.2 atomic percent, M for 0.1 to 2.4 atomic percent, Ga for 0.07 to 1.95 atomic percent, and T is the remainder, the following formula 1 is satisfied. manufactured from a sintered body that includes a main phase consisting mainly of R2Fe 14 B and a grain boundary comprising more R than the main phase, wherein the grain boundary phase comprises a phase having a concentration of all atoms of the rare earth elements of 70 atomic % or more, and a phase having a concentration of all atoms of the rare earth elements in the range of 25 atomic % to 35 atomic % 0.34≤TRE≤0.36 where B represents the concentration (atomic %) of the boron element and TRE represents the concentration (atomic %) of all rare earth elements. [6] Sintered RTB rare earth-based magnet according to claim 5, further comprising Si. [7] Sintered magnet based on RTB rare earth elements according to claim 5 or 6, wherein the volume ratio of the phase with a concentration of all atoms of the rare earth elements in a range of 25 atomic % to 35 atomic % is in the range of 0.005 vol% to 3 vol%. [8] Motor containing the sintered RTB rare earth-based magnet according to claim 5 or 6.

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