JP6750543B2 - R-T-B system sintered magnet - Google Patents

Description

The present disclosure relates to an RTB-based sintered magnet.

The R-T-B system sintered magnet (R is at least one of rare earth elements and always contains Nd. T is at least one of transition metal elements and always contains Fe. B is boron). Known as the most high-performance magnet among permanent magnets, it is used for various motors such as voice coil motors (VCM) for hard disk drives, motors for electric vehicles (EV, HV, PHV), motors for industrial equipment, and home appliances. It is used for etc.

R-T-B based sintered magnet is mainly grain boundary phase located in the grain boundary of the main phase and the main phase consisting of R _{2 T} 14 _B compound (hereinafter, simply referred to as "grain boundary") from the It is configured. The R ₂ T ₁₄ B compound is a ferromagnetic phase having high magnetization, and forms the basis of the characteristics of the RTB based sintered magnet.

The _RTB sintered magnet has a problem that irreversible thermal demagnetization occurs because the coercive force H _cJ (hereinafter sometimes simply referred to as “coercive force” or “H _cJ ”) decreases at high temperatures. Therefore, in a particularly R-T-B based sintered magnet used in an electric vehicle motor, having a high H _cJ even at high temperatures, that is, required to have a higher H _cJ at room temperature.

In the R-T-B based sintered _magnet, R _{2 T 14} B compound in light rare-earth element RL included in the R (mainly Nd and / or Pr) of some heavy rare-earth element RH (mainly Dy and / or Tb ) Is known to improve H _cJ . H _cJ improves with an increase in the substitution amount of the heavy rare earth element.

_However, while improving the _{H cJ} of R _{2 T 14} B when the light rare-earth element RL in the compound is replaced with the heavy rare-earth element RH R-T-B based sintered magnet, the remanence _{B r} (hereinafter, simply "B " _r "). Further, heavy rare earth elements, especially Dy, have problems such as unstable supply and large price fluctuations because of the small amount of resources and limited production areas. Therefore, in recent years, users have been _demanding to improve H _cJ without using heavy rare earth elements as much as possible.

In Patent Document 1, an RE-M alloy having a melting point of 800° C. or lower is brought into contact with a RE-T-B based sintered body, and heat-treated at a temperature 50 to 200° C. higher than the vapor pressure curve of the M element, It is disclosed to improve the coercive force without using a heavy rare earth element such as Dy. By this heat treatment, the RE element diffuses and permeates into the molded body from the melt of the RE-M alloy. Patent Document 1 shows that the M element is suppressed from being introduced into the magnet due to evaporation during the treatment, and only the RE element is efficiently introduced. Patent Document 1 discloses, as a specific example, heat treatment using Nd-20 at% Ga at 850° C. for 15 hours.

In Patent Document 2, a molded body that has been subjected to hot working for imparting anisotropy to a sintered body is brought into contact with a low melting point financial liquid containing a rare earth metal to heat-treat the molded body so that Dy, Tb, etc. It is disclosed that the coercive force is improved without adding a large amount of rare metals. As a specific example, it is disclosed that Nd-Zn is used in a low-melting-point financial liquid and brought into contact with a molded body, and heat treatment is performed at 580°C.

In Patent Document 3, a metal-evaporating material containing at least one of Dy and Tb is evaporated on the surface of a rare earth-based sintered magnet, and a film forming step of attaching the evaporated metal atoms, and a heat treatment are applied to the surface. It is disclosed that the coercive force is improved by performing a diffusion step of diffusing the attached metal atoms into the crystal grain boundary phase of the sintered magnet. As a specific example, it is disclosed that the metal evaporation material is heat-treated at 850° C. and 950° C. using Dy-Nd-Zn and Tb-Nd-Zn.

JP, 2014-086529, A International Publication No. 2012/036294 International Publication No. 2008/032667

The method described in Patent Document 1 is noteworthy in that it is possible to increase the coercive force of the RTB-based sintered magnet without using any heavy rare earth element. However, the coercive force is increased only in the vicinity of the magnet surface, and the coercive force inside the magnet is hardly improved. As described in Patent Document 1, the thickness of a grain boundary (particularly, a grain boundary existing between two main phases, hereinafter sometimes referred to as “two-grain grain boundary”) from the surface of the magnet toward the inside of the magnet. Is sharply thinned, and therefore, the coercive force greatly differs between the vicinity of the surface of the magnet having thick grain boundaries and the inside of the magnet. Then, if a portion having a high coercive force is removed by surface grinding or the like that is performed for adjusting a magnet size in a general magnet manufacturing process, there is a problem that a coercive force improving effect is greatly impaired.

Patent Document 2 is proposed by the same applicant as that of Patent Document 1, in which the target RTB-based sintered magnet is subjected to hot working for imparting anisotropy to the sintered body. Although it is different from Patent Document 1 in that it is a molded body obtained, both are common in that a low melting point financial liquid (RE(Nd)-M alloy in Patent Document 1) mainly using Nd as a rare earth metal is brought into contact with each other. doing. Therefore, even in the method described in Patent Document 2, it is considered that the high coercive force is increased only in the vicinity of the surface of the magnet as in Patent Document 1, and the coercive force inside the magnet is hardly improved.

According to the method described in Patent Document 3, the diffusion step can be performed in a short time, the yield of Dy and Tb can be increased, and R- having a high coercive force with high productivity and low cost. although T-B based sintered magnet is obtained, it does not satisfy the requirements of improving H _cJ without lowering the no B _r using only possible heavy rare earth element.

In the embodiment of the present disclosure, not only the vicinity of the magnet surface but also the coercive force inside the magnet is improved, and the effect of improving the coercive force is not significantly impaired by surface grinding for adjusting the magnet size. And an RTB-based sintered magnet having a high coercive force.

The R1-T1-X1 series sintered magnet of the present disclosure is
R1: 27 mass% or more and 35 mass% or less (R1 is at least one kind of rare earth element, 50 mass% or more of R1 as a whole is Nd, and always contains Pr),
X1: 0.85 mass% or more and 0.93 mass% or less (X1 is B or B and C),
Zn: 0.3 mass% or more and 2.0 mass% or less,
T1: 61.5 mass% or more (T1 is Fe or Fe and M, M is Ga, Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Ge, Zr, Nb, Mo, Ag One or more selected from, and 80 mass% or more of the total T1 is Fe),
Containing
The molar ratio of T1 to X1 ([T1]/[X1]) is 13.0 or more,
The Pr concentration and the Zn concentration in a region of the magnet surface having a thickness of 200 μm measured from the plane orthogonal to the orientation direction along the orientation direction are higher than the Pr concentration and the Zn concentration in the magnet central part, respectively.
R2-T2-A compound (R2 is at least one of rare earth elements, and 50 mol% or more of the entire R2 is Pr. T2 is at least one of Fe, Co, Ni, Mn, Ti, and Cr. 50% or more of the total T2 is Fe. A is at least one of Zn, Cu, Ga, Al, Ge, and Si, and 50% or more of the total A is Zn.

In one embodiment, the Pr concentration in the region is higher than the Pr concentration in the central portion of the magnet by 3.0 mass% or more.

In one embodiment, the Zn concentration in the region is 1.0 mass% or more higher than the Zn concentration in the central portion of the magnet.

In one embodiment, the molar ratio of T1 to X1 ([T1]/[X1]) is 14.0 or more.

In certain embodiments, the R2-T2-A _compounds have a La _{6 Co} 11 Ga ₃ type crystal structure.

In one embodiment, the R2-T2-A compound is present at least in the grain boundary in the center of the magnet.

In one embodiment, the thickness of the grain boundary in the central portion of the magnet is 100 nm or more.

In certain embodiments, the R2-T2-A compound _is formed from R _{6 T} 13 Zn phase.

According to the R1-T1-X1 system sintered magnet (R-T-B system sintered magnet) of the present disclosure, not only the vicinity of the magnet surface but also the coercive force inside the magnet is improved, and the surface for adjusting the magnet dimension is improved. The effect of improving the coercive force is not significantly impaired even by grinding, and a heavy rare earth element is unnecessary, and a high coercive force can be exhibited.

It is a schematic diagram which shows the main phase and grain boundary phase of a R1-T1-X1 type|system|group sintered magnet. It is the schematic diagram which further expanded the inside of the broken-line rectangular area of FIG. 1A. It is explanatory drawing which shows typically the arrangement|positioning form of R3-T3-X2 type|system|group sintered compact and R4-Zn type alloy in a heat processing process. No. It is the photograph which observed the magnet surface part of 3-2 with the scanning electron microscope. No. It is the photograph which observed the magnet center part of 3-2 with the scanning electron microscope. No. It is the photograph which observed the magnet surface part of 3-8 with the scanning electron microscope. No. It is the photograph which observed the magnet central part of 3-8 with the scanning electron microscope. It is a photograph which shows the field which performs energy dispersive X-ray spectroscopy analysis. No. It is a photograph which shows the position which performs energy dispersive X-ray-spectroscopic analysis in 2-6. No. It is a photograph which shows the position which performs the energy dispersive X-ray-spectroscopic analysis in 2-11. No. It is a photograph which shows the position which performs the energy dispersive X-ray-spectral analysis in 2-12. It is explanatory drawing which shows a magnet surface part and a magnet center part when a magnet is a roof tile shape.

The R1-T1-X1 based sintered magnet according to the present disclosure contains the following elements in a non-limiting and exemplary embodiment.

R1: 27 mass% or more and 35 mass% or less (R1 is at least one kind of rare earth element, 50 mass% or more of R1 as a whole is Nd, and always contains Pr),
X1: 0.85 mass% or more and 0.93 mass% or less (X1 is B or B and C),
Zn: 0.3 mass% or more and 2.0 mass% or less,
T1: 61.5 mass% or more (T1 is Fe or Fe and M, M is Ga, Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Ge, Zr, Nb, Mo, Ag Fe is contained in 80% by mass or more of the entire T1).

Further, in this embodiment, the molar ratio of T1 to X1 ([T1]/[X1]) (hereinafter sometimes referred to as “mol ratio of [T1]/[X1]”) is 13.0 or more, The molar ratio of [T1]/[X1] may be 14.0 or more.

The R1-T1-X1 system sintered magnet in the present embodiment contains an R2-T2-A compound. R2 in the R2-T2-A compound is at least one of rare earth elements, and 50 mol% or more of the entire R2 is Pr. T2 is at least one of Fe, Co, Ni, Mn, Ti, and Cr, and 50 mol% or more of the entire T2 is Fe. A is at least one of Zn, Cu, Ga, Al, Ge, and Si, and 50 mol% or more of the entire A is Zn. R2-T2-A compounds typically _have a La _{6 Co} 11 Ga ₃ type crystal structure, typically a _R 6 _Fe 13 Zn compounds. The composition of the R2-T2-A compound is such that R2 is 5 mol% or more and 50 mol% or less (preferably 20 mol% or more and 40 mol% or less), and T2 is 30 mol% or more and 94 mol% or less (preferably 50 mol% or more and 70 mol% or less). And A is 1 mol% or more and 20 mol% or less (preferably 2 mol% or more and 20 mol% or less).

The Pr concentration in a region having a thickness of 200 μm measured along the orientation direction from the surface of the magnet surface orthogonal to the orientation direction (magnetization direction) (hereinafter, may be simply referred to as “magnet surface portion”) is It is higher than the Pr concentration in the central part. Further, the Zn concentration in the magnet surface portion is higher than the Zn concentration in the magnet central portion. The “Pr concentration” and the “Zn concentration” are values obtained by measuring arbitrary positions on the magnet surface portion within a range of, for example, 50 nm×50 nm and averaging the concentrations in the main phase particles and the grain boundary phase, respectively.

When the magnet has a roof tile shape as shown in FIG. 11 and the orientation direction is the thickness direction of the magnet (the direction of arrow 101), the surface of the magnet surface orthogonal to the orientation direction is the first curved surface. At least one of the (upper surface) 104 and the second curved surface (back surface) 105. Therefore, a region having a thickness of 200 μm measured along the orientation direction from the first curved surface 104 and the second curved surface 105 becomes the magnet surface portion.

When the magnet has a roof tile shape and the orientation direction is the direction in which the magnet extends (the direction of arrow 102), the first end surface 106 and the second end surface 107 are surfaces of the magnet surface orthogonal to the orientation direction. Become.

When the magnet has a cylindrical shape, the description of the tile-shaped magnet is applied when the direction of arrow 102 in FIG. 11 is aligned with the direction of the central axis and the direction of arrow 101 is the radial direction.

Further, in the present disclosure, when the magnet has a roof tile shape and the orientation direction is the width direction of the magnet (direction of arrow 103), the surface of the magnet surface that is orthogonal to the orientation direction is substantially orthogonal to the orientation direction. These are the first side surface 108 and the second side surface 109. Therefore, in this case, a region having a thickness of 200 μm measured along the orientation direction from the first side surface 108 and the second side surface 109 becomes the magnet surface portion.

The magnet central portion is a portion located at the center of the magnet, and is typically the center of gravity when the magnet has a polyhedral shape or a cylindrical shape. When the magnet has a roof tile shape as shown in FIG. 11, the central portion of the magnet has a thickness direction (direction of arrow 101), a length direction (direction of arrow 102), and a width direction (direction of arrow 103) of the magnet. The portion 100 is located at the center of all of. When the magnet has a cylindrical shape, the center portion of the magnet is located at the center of both the thickness direction and the length direction of the magnet.

As described below, in the embodiment of the present disclosure, when manufacturing a R1-T1-X1 system sintered magnet, R4 and Zn containing Pr as a main component are sintered from an R4-Zn system alloy and having a specific composition. It diffuses from the surface of the body to the inside. The magnet thus obtained contains the R2-T2-A compound, and 50 mol% or more of the entire R2 is Pr. On the other hand, when R not containing Pr as a main component (R containing Nd as a main component (for example, R1)) and Zn are diffused inward from the surface of the sintered body, the R2 does not contain Pr in an amount of 50 mol% or more. (For example, it contains 50 mol% or more of Nd). The above-mentioned "magnet surface portion" is a portion that comes into contact with the R4-Zn alloy and receives supply of Pr and Zn from the R4-Zn alloy during the manufacturing process. Due to such diffusion, a concentration gradient of Pr and Zn is generated inside the magnet, and this concentration gradient remains inside the finally obtained magnet. The “magnet surface portion” in which the concentration of Pr and Zn is higher than that in the central portion of the magnet does not need to be located on the entire surface of the magnet.

In one embodiment, the R2-T2-A compound is present at least in the grain boundary in the central part of the magnet, and the thickness of the grain boundary in the central part of the magnet is 100 nm or more.

The R2-T2-A compound can be identified, for example, by observing an arbitrary magnet cross section with a scanning electron microscope and further measuring the observed region by energy dispersive X-ray spectroscopy (EDS). Further, the thickness of the grain boundary can be obtained by measurement from a micrograph of the cross section. According to the examples described below, grain boundaries having a thickness of 100 nm or more are present throughout the magnet.

The Pr concentration is preferably 3.0 mass% or more higher in the magnet surface portion than in the magnet central portion, and the Zn concentration is 1.0 mass% or more higher in the magnet surface portion than in the magnet central portion. preferable. In the present disclosure, "the Pr concentration is higher than the central portion of the magnet by 3.0 mass% or more in the magnet surface portion" means that the orientation direction (magnetization direction) of the magnet surface is perpendicular to the orientation direction. It means that the Pr concentration in the region of 200 μm in thickness (“magnet surface portion”) measured along is higher than the Pr concentration in the central portion of the magnet by 3.0 or more in percentage points (mass %). For example, when the Pr concentration in the central portion of the magnet is 5.0 mass%, it means that the Pr concentration in the magnet surface portion is 8.0 mass% or more. The same applies to the Zn concentration. The concentrations of Pr and Zn can be measured, for example, by observing the magnet central portion and the magnet surface portion with a scanning electron microscope in a cross section that passes through the magnet central portion and is parallel to the orientation direction, and further observes the magnet central portion and the magnet surface. The parts are measured by performing energy dispersive X-ray spectroscopy (EDS). The concentration gradients of Pr and Zn show that these elements are in a state of being diffused from the magnet surface to the inside of the magnet.

With the above configuration, the R1-T1-X1 system sintered magnet according to the present disclosure is improved not only in the vicinity of the magnet surface but also in the coercive force inside the magnet. This is because the two-grain grain boundary is thick. Further, the effect of improving the coercive force is not significantly impaired by the surface grinding for adjusting the magnet size. Then, a high coercive force can be realized without using a heavy rare earth element.

The present inventors, as a method for producing the above-mentioned R1-T1-X1 based sintered magnet, is a common main phase of a stoichiometric composition of R1-T1-X1 based sintered magnet _R 2 _{T 14} B R is mainly composed of Pr in an alloy sintered body (R3-T3-X2 alloy sintered body) having a composition in which T is rich and B (when C is contained, the sum of B and C) is poor. A method of contacting and heat treating an R4-Zn-based alloy containing 15 mol or more and 40 mol or less of Zn was found. By this method, when the liquid phase generated from the R4-Zn-based alloy is diffused and introduced from the surface of the sintered body to the inside through the grain boundary in the sintered body, if Pr is present in R4, the grain boundary is present. It has been found that diffusion is promoted and Pr and Zn can be diffused deep inside the magnet. It was also found that by diffusing Zn into the alloy sintered body having the above-described specific composition, thick two-grain grain boundaries containing Zn can be easily formed even inside the alloy sintered body. When such a structure is formed, magnetic coupling between the main phase crystal grains is significantly weakened, so that an R1-T1-X1 system sintered magnet having a very high coercive force can be obtained without using a heavy rare earth element. To be

Further, based on these findings, as will be described later, as a result of considering especially the distribution ratio of C to the grain boundary in [X1], the molar ratio of T3 to X2 in the alloy sintered body ([T3]/[ X2]) (hereinafter sometimes referred to as “[T3]/[X2] mol ratio”) is in the range of 13.0 or more and less than 14.0, the molar ratio of [T3]/[X2] is It has been found that it exhibits a coercive force close to that of an R1-T1-X1 system sintered magnet produced using an alloy sintered body of 14.0 or more.

In the methods described in Patent Documents 1 and 2, the composition of the base material (the molded body in Patent Document 1 and the molded body in Patent Document 2) that undergo diffusion is R ₂ T, which is the stoichiometric composition of the main phase. ₁₄ B has a composition in which T is poorer and B is richer than B, and C is not considered at all. Further, the effect of using an alloy containing both Pr and Zn as a diffusion source and diffusing an alloy containing both Pr and Zn for the specific composition of the present disclosure (a thick two-grain grain boundary is a sintered body). Can be easily formed to the inside).

First, before describing the embodiment of the R1-T1-X1 system sintered magnet in detail, the basic structure of the R1-T1-X1 system sintered magnet will be described.

The R1-T1-X1 system sintered magnet has a structure in which powder particles of a raw material alloy are combined by sintering, and a main phase mainly composed of an R ₂ T ₁₄ B compound and a grain boundary portion of this main phase are formed. It is composed of a grain boundary phase and a grain boundary phase.

FIG. 1A is a schematic diagram showing a main phase and a grain boundary phase of the R1-T1-X1 system sintered magnet, and FIG. 1B is a schematic diagram further enlarging a broken line rectangular region of FIG. 1A. In FIG. 1A, as an example, an arrow having a length of 5 μm is shown as a reference length indicating a size for reference. As shown in FIGS. 1A and 1B, the R1-T1-X1 system sintered magnet has a main phase 12 mainly composed of an R ₂ T ₁₄ B compound and a grain boundary phase 14 located at a grain boundary portion of the main phase 12. It consists of and. Further, as shown in FIG. 1B, the grain boundary phase 14 includes a two-grain grain boundary phase 14 a in which two R ₂ T ₁₄ B compound particles (grains) are adjacent to each other and three R ₂ T ₁₄ B compound grains in adjacent to each other. Grain boundary triple point 14b.

The R ₂ T ₁₄ B compound that is the main phase 12 is a ferromagnetic material having high saturation magnetization and an anisotropic magnetic field. Therefore, the R1-T1-X1 based sintered magnet, it is possible to improve the _{B r} by increasing the existence ratio of _R 2 _{T 14} B compound is the main phase 12. In order to increase the abundance ratio of the R ₂ T ₁₄ B compound, the R content, the T content, and the B content in the raw material alloy are set to the stoichiometric ratio of the R ₂ T ₁₄ B compound (R content:T content:B content= 2:14:1). When the amount of B or the amount of R for forming the R ₂ T ₁₄ B compound is less than the stoichiometric ratio, generally, the grain boundary phase 14 has a small anisotropic magnetic field such as the Fe phase or the R ₂ T ₁₇ phase. Ferromagnetic material is generated, and H _cJ drops sharply.

In the following, non-limiting exemplary embodiments of the present disclosure are described.

(1) Step of preparing an R3-T3-X2 alloy sintered body In the step of preparing an R3-T3-X2 alloy sintered body (hereinafter, simply referred to as "sintered body"), the sintered body The composition of R3 is at least one of rare earth elements and always contains Nd, 27 mass% or more and 35 mass% or less, T3 is Fe or Fe and M, and M is Ga, Al, Si, Ti, V , Cr, Mn, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, Ag, X2 is B, and a part of B can be replaced with C. The molar ratio of T3]/[X2] is 13.0 or more, preferably 13.6 or more, and more preferably 14.0 or more.

R3 is at least one of rare earth elements and always contains Nd. Examples of rare earth elements other than Nd include Pr. Further, a small amount of a heavy rare earth element such as Dy, Tb, Gd or Ho which is generally used for improving the coercive force of the R1-T1-X system sintered magnet may be contained. However, according to the embodiment of the present disclosure, a sufficiently high coercive force can be obtained without using a large amount of the heavy rare earth element. Therefore, the content of the heavy rare earth element may be 1 mass% or less of the entire R3-T3-X2 alloy sintered body (the heavy rare earth element in the R3-T3-X2 alloy sintered body is 1 mass% or less). It is more preferably 0.5 mass% or less, and further preferably not contained (substantially 0 mass%).

R3 is 27 mass% or more and 35 mass% or less of the entire R3-T3-X2 alloy sintered body. If R3 is less than 27 mass%, a liquid phase is not sufficiently generated in the sintering process, and it becomes difficult to sufficiently densify the sintered body. On the other hand, even if R3 exceeds 35 mass %, the effect of the present disclosure can be obtained, but the alloy powder during the manufacturing process of the sintered body becomes very active, which may cause significant oxidation or ignition of the alloy powder. Therefore, it is preferably 35 mass% or less. R3 is more preferably 28 mass% or more and 33 mass% or less, and further preferably 28.5 mass% or more and 32 mass% or less.

T3 is Fe or Fe and M, and M is one or more selected from Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo and Ag. is there. That is, T3 may be Fe only (including unavoidable impurities) or Fe and M (including unavoidable impurities). When T3 is composed of Fe and M, the amount of Fe with respect to the entire T3 is preferably 80 mol% or more. When T3 consists of Fe and M, M is selected from Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo and Ag. It may be one or more.

X2 is B, and a part of B can be replaced with C (carbon). That is, X2 is B or B and C. When a part of B is replaced with C, not only those that are positively added during the manufacturing process of the sintered body but also solid or liquid lubricants used in the manufacturing process of the sintered body and wet forming Those that remain in the sintered body due to the dispersion medium used in some cases are also included. Although C derived from a lubricant or a dispersion medium is unavoidable, it can be controlled within a certain range (adjustment of addition amount and decarburization treatment). The amount of B and the amount of C to be positively added may be set so as to satisfy the relationship with. To positively add C during the manufacturing process of the sintered body, for example, C is added as a raw material when manufacturing the raw material alloy (a raw material alloy containing C is manufactured), or a manufacturing process It is possible to add a specific amount of a C source (carbon source) such as carbon black to the alloy powder therein (coarse pulverized powder before pulverization by a jet mill or the like described later or fine pulverized powder after pulverization). Note that B is preferably 80 mol% or more, and more preferably 90 mol% or more with respect to the entire X2. Further, X2 is preferably 0.8 mass% or more and 1.0 mass% or less of the entire R3-T3-X2 alloy sintered body. X2 can also be obtained the effect of the present disclosure is less than 0.8 mass% but not preferred because it causes a significant decrease in _{B r.} On the other hand, when X2 exceeds 1.0 mass %, the molar ratio of [T3]/[X2] described later cannot be set to 13.0 or more, and the effect of the present disclosure cannot be obtained, which is not preferable. X2 is more preferably 0.83 mass% or more and 0.98 mass% or less, and further preferably 0.85 mass% or more and 0.95 mass% or less.

The T3 and X2 are preferably set so that the molar ratio of [T3]/[X2] is 14.0 or more. That is, this condition is that the molar ratio of [T]/[B] of R ₂ T ₁₄ B, which is the stoichiometric composition of the main phase of a general R1-T1-X1 system sintered magnet (=14.0). Or T is rich and B is poor. The inventors have found that the content of T is richer than that of R ₂ T ₁₄ B, which is the stoichiometric composition of the main phase, and that B is poor (or the molar ratio of [T] and [B] is equal to the stoichiometric composition). the alloy sintered body composition, by diffusing the R4-Zn-based alloy, R-T-Zn phase to diffuse deep to Pr and Zn are internal magnet (e.g. _R 6 _T 13 Zn phase) generated It was found that it is possible to thicken the two-particle grain boundary between the magnet surface and the inside of the magnet. As a result of further research, it was found that the ratio of T was higher than the molar ratio of [T]/[B] of R ₂ T ₁₄ B, which is the stoichiometric composition of the main phase of a general R1-T1-X1 system sintered magnet. Is poor and B is rich, the coercive force obtained when using an alloy sintered body of 14.0 or more is exceeded if the molar ratio of [T3]/[X2] is 13.0 or more. However, it was found that a coercive force close to that can be obtained. This is because assuming that the molar ratio of [T3]/[X2] is 14.0 or more, it is assumed that B and C forming X2 are all used for forming the main phase. Not all X2 (particularly C) is used for forming the main phase, and it is also present in the grain boundary phase. Therefore, in reality, a high coercive force can be obtained even if the [X2] is set to be slightly higher (T is poor and B is rich), that is, even if the molar ratio of [T3]/[X2] is 13.0 or more. I found that. It is difficult to accurately determine the distribution ratio of X2 to the main phase and the grain boundary phase, but when the molar ratio of [T3]/[X2] is 13.0 or more, it is used for forming the main phase. It is considered that [T3]/[X2′] is 14.0 or more, where the mol concentration of X2 is [X2′] (at this time, [X2′]≦[X2] is satisfied). As described above, C is inevitably contained in the sintered body during the manufacturing process even if it is not positively added. Therefore, considering the amount of C contained in the sintered body, [T3]/ The molar ratio of [X2] needs to be 13.0 or more. If the molar ratio of [T3]/[X2] is less than 13.0, there is a possibility that the above [T3]/[X2′] may not be set to 14.0 or more, and finally obtained R1- In the T1-X1 system sintered magnet, the R1-T1-X1 system sintered magnet having a high coercive force without being able to thicken the two-particle grain boundary between the magnet surface part and the inside of the magnet is used. It may be difficult to obtain. As described above, a high coercive force is obtained when the molar ratio of [T3]/[X2] is 13.0 or more. However, in order to obtain a higher coercive force and a stable high coercive force in the mass production process. In order to obtain the above, the molar ratio of [T3]/[X2] is preferably 13.6 or more, more preferably 13.8 or more, and further preferably 14.0 or more. If the molar ratio of [T3]/[X2] exceeds 15.0, the amount of B forming X2 may be too small and the coercive force may be significantly reduced. The ratio is preferably 15.0 or less.

The R3-T3-X2 system alloy sintered body can be prepared by using a general method for producing a R1-T1-X1 system sintered magnet represented by an Nd-Fe-B system sintered magnet. As an example, a raw material alloy produced by a strip casting method or the like is crushed to a size of 3 μm or more and 10 μm or less by using a jet mill or the like, then molded in a magnetic field, and sintered at a temperature of 900° C. or more and 1100° C. or less. It can be prepared by In addition, in the obtained sintered body, the coercive force may be very low. If the crushed particle size of the raw material alloy (volume center value obtained by measurement by airflow dispersion type laser diffraction method=D50) is less than 3 μm, it is very difficult to produce a crushed powder, and the production efficiency is significantly reduced, which is preferable. Absent. On the other hand, if the crushed particle size exceeds 10 μm, the crystal grain size of the main phase of the finally obtained R1-T1-X1 system sintered magnet becomes too large, and a high coercive force is obtained even if a thick two-grain grain boundary is formed. It is not preferable because it is difficult to obtain.

The R3-T3-X2 alloy sintered body may be prepared from one kind of raw material alloy (single raw material alloy) as long as the above conditions are satisfied, or two or more kinds of raw material alloys are used. You may produce by the method of mixing them (blending method). Further, the R3-T3-X2 system sintered body may contain inevitable impurities such as O (oxygen) and N (nitrogen) which are present in the raw material alloy or introduced in the manufacturing process.

Moreover, when preparing a R3-T3-X2 type alloy sintered compact, you may further heat-process after sintering at the temperature of 400 degreeC or more and less than a sintering temperature. In some cases, the heat treatment may be able to further improve the magnetic characteristics of the final R1-T1-X1 system sintered magnet. In particular, when T3 of the R3-T3-X2 alloy sintered body contains 0.1 mass% or more of at least one of Si, Ga, Al, Zn, and Ag as an M element, a high temperature of 700°C or higher and 1000°C or lower. It is preferable to perform heat treatment. Such high temperature heat treatment is particularly effective when the sintered body contains Ga.

(2) Step of preparing an R4-Zn alloy In the step of preparing an R4-Zn alloy, the composition of the R4-Zn alloy is such that R4 is at least one of rare earth elements and Pr is 50 mol of the entire R4. % Or more, R4 is 60 mol% or more and 85 mol% or less, Zn is 15 mol% or more and 40 mol% or less, and 50 mol% or less of the entire Zn can be replaced with Cu. R4 is preferably 70 mol% or more and 85 mol% or less, and more preferably 70 mol% or more and 85 mol% or less. This is because a higher coercive force can be obtained.

R4 is at least one of rare earth elements and always contains Pr in an amount of 50 mol% or more based on the entire R4. In the present disclosure, “containing Pr in an amount of 50 mol% or more of the entire R4” means that the content (mol%) of R4 in the R4-Zn alloy is 100%, and 50% or more of the content is Pr. means. Therefore, for example, if R4 in the R4-Zn alloy is 60 mol%, Pr is contained in the R4-Zn alloy in an amount of 30 mol% or more. When Pr is less than 50 mol% of the whole R4, in the finally obtained R1-T1-X1 system sintered magnet, the two-particle grain boundary inside the magnet cannot be made thick and the heavy rare earth element is not used. An R1-T1-X1 system sintered magnet having a high coercive force cannot be obtained. Preferably, R4 in the R4-Zn alloy consists of Pr only. This is because a higher coercive force can be obtained. R4 may contain a small amount of heavy rare earth elements such as Dy, Tb, Gd, and Ho which are generally used for improving the coercive force of the R1-T1-X1 system sintered magnet. However, according to the present disclosure, a sufficiently high coercive force can be obtained without using a large amount of the heavy rare earth element. Therefore, the content of the heavy rare earth element is preferably 10 mol% or less of the entire R4-Zn alloy (the heavy rare earth element in the R4-Zn alloy is 10 mol% or less), and more preferably 5 mol% or less. It is more preferable not to contain (substantially 0 mol%). Even when the heavy rare earth element is contained in R4 of the R4-Zn alloy, 50 mol% or more of R4 is preferably Pr, and R4 excluding the heavy rare earth element is only Pr (including unavoidable impurities). Is more preferable. Further, Zn is 15 mol% or more and 40 mol% or less, and 50 mol% or less of the entire Zn can be replaced with Cu. It should be noted that in the present disclosure, “50 mol% or less of the entire Zn can be replaced with Cu” means that when the content (mol%) of Zn in the R4-Zn-based alloy is 100%, 50% or less thereof is included. Means that can be replaced by Cu. For example, if Zn in the R4-Zn-based alloy is 30 mol%, Cu can be replaced with Zn up to 15 mol% or less in the R4-Zn-based alloy.

The R4-Zn alloy may contain a small amount of Al, Si, Ti, V, Cr, Mn, Co, Ni, Ga, Ge, Zr, Nb, Mo, Ag and the like. Further, Fe may be contained in a small amount, or the effect of the present disclosure can be obtained even if Fe is contained in an amount of 20 mass% or less. However, if the Fe content exceeds 20 mass %, the coercive force may decrease. Further, it may contain unavoidable impurities such as O (oxygen), N (nitrogen), and C (carbon).

The R4-Zn alloy is a raw material alloy manufacturing method adopted in a general R1-T1-X1 sintered magnet manufacturing method, for example, a die casting method, a strip casting method, or a single-roll ultra-quenching method ( It can be prepared by using a melt spinning method) or an atomizing method. Further, the R4-Zn-based alloy may be one obtained by crushing the alloy obtained above by a known crushing means such as a pin mill.

(3) Step of Heat Treatment At least a part of the surface of the R3-T3-X2 alloy sintered body prepared as described above is brought into contact with at least a part of the R4-Zn alloy prepared as described above, and a vacuum or an inert gas is provided. Heat treatment is performed in an atmosphere at a temperature of 450° C. or higher and 800° C. or lower. As a result, a liquid phase is generated from the R4-Zn-based alloy, and the liquid phase is diffused and introduced from the surface of the sintered body into the inside through the grain boundaries in the sintered body, and R3 ₂ T3 ₁₄ which is the main phase. A thick two-grain grain boundary containing Zn between X2 phase crystal grains can be easily formed inside the sintered body, and magnetic coupling between main phase crystal grains is significantly weakened. As a result, an R1-T1-X1 system sintered magnet having a very high coercive force can be obtained without using a heavy rare earth element. The heat treatment temperature is preferably 480° C. or higher and 560° C. or lower. It can have a higher coercive force.

Generally, when surface grinding for magnet size adjustment is performed, a region of about 200 μm is removed from the surface of the sintered body, so that thick two-grain grain boundaries are formed in the R3-T3-X2 alloy sintered body. The effect of the present disclosure can be obtained as long as it exists up to a region of about 250 μm from the surface. However, in such a case (when the region where the thick two-grain grain boundaries are formed is about 250 μm from the surface of the sintered body), H _cJ near the center of the R3-T3-X2 alloy sintered body after heat treatment Is not sufficiently improved, the squareness of the demagnetization curve may be deteriorated. Therefore, _HcJ near the center of the R3-T3-X2 alloy sintered body is heat-treated at a temperature of 450° C. or higher and 600° C. or lower without contacting the R4-Zn alloy (general R1-T1-X1 alloy). when subjected to heat treatment) for improving the coercive force of the sintered _magnet, it is preferable _{that H cJ} ≧ _1200kA / m is _obtained, it is more preferable _{that H cJ} ≧ _1360kA / m is obtained. Such By using the sintered body, it is possible to obtain a squareness excellent demagnetization curve with a high H _cJ overall magnet have a smaller amount of introduced R4-Zn alloy, a result, a high B _r High H _cJ can be easily achieved at the same time.

When _HcJ near the center of the R3-T3-X2 alloy sintered body is heat-treated at a temperature of 450°C or higher and 600°C or lower without contacting the R4-Zn alloy, _HcJ ≥1200 kA/m The obtained R3-T3-X2 alloy sintered body can be easily obtained when T3 contains Ga. The content of Ga relative to the entire R3-T3-X2 alloy sintered body is preferably 0.05 mass% or more and 1 mass% or less, more preferably 0.1 mass% or more and 0.8 mass% or less, and 0.2 mass% or more and 0.6 mass% or less. % Or less is more preferable.

In the heat treatment step, only the R4-Zn alloy may be contacted with at least a part of the surface of the R3-T3-X2 alloy sintered body. A method of dispersing it in a solvent or the like and applying it to the surface of the R3-T3-X2 system alloy sintered body, or a method of spraying R4-Zn system alloy powder on the surface of the R3-T3-X2 system alloy sintered body, etc. May be adopted. Further, as shown in Examples described later, it is preferable that the R4-Zn alloy is arranged so as to contact at least the surface perpendicular to the orientation direction of the R3-T3-X2 alloy sintered body. Even if the R4-Zn alloy is brought into contact only with the orientation direction of the R3-T3-X2 alloy sintered body, or the R4-Zn alloy is brought into contact with the entire surface of the R3-T3-X2 alloy sintered body, can have the features disclosed, it is possible to obtain a high B _r and high H _cJ.

By spraying and/or applying the R4-Zn-based alloy powder to at least a part of the surface of the R3-T3-X2-based alloy sintered body, at least one of the surfaces of the R3-T3-X2-based alloy sintered body can be more easily produced. At least a part of the R4-Zn alloy can be brought into contact with the part.

The introduction amount of the liquid phase generated from the R4-Zn alloy to the R3-T3-X2 alloy sintered body can be controlled by the holding temperature and the holding time. When the R4-Zn alloy is sprayed and/or applied on the surface of the sintered body, it is preferable to control the spraying amount or the coating amount. The amount of the R4-Zn alloy sprayed or applied is preferably 0.2 parts by mass or more and 5.0 parts by mass or less, and 0.2 parts by mass with respect to 100 parts by mass of the R3-T3-X2 alloy sintered body. More preferably, the amount is not less than 3.0 parts and not more than 3.0 parts by mass. With such a condition, both of the high B _r and high H _cJ can be easily realized. When the R4-Zn alloy is sprayed or applied only on a part of the surface of the R3-T3-X2 alloy sintered body, it is preferable to spray or apply it on the surface perpendicular to the orientation direction.

The heat treatment is performed by holding at a temperature of 450° C. or higher and 800° C. or lower in a vacuum or an inert gas atmosphere and then cooling. By performing the heat treatment at a temperature of 450° C. or higher and 800° C. or lower, at least a part of the R4-Zn alloy is melted, and the generated liquid phase passes from the surface of the sintered body to the inside through the grain boundaries in the sintered body. It can be diffused and introduced to form thick two-grain boundaries. If the heat treatment temperature is lower than 450° C., no liquid phase is generated and thick grain boundaries cannot be obtained. Further, even if the temperature exceeds 800° C., it becomes difficult to form thick two-grain grain boundaries. The reason why it becomes difficult to form thick two-grain grain boundaries when heat treatment is performed at a temperature higher than 800° C. is not clear so far, but the main phase due to the liquid phase introduced into the sintered body And the formation of an R ₆ T ₁₃ Zn phase (R is at least one of rare earth elements and always contains Pr and/or Nd, and T is at least one of transition metal elements and always contains Fe). It seems that the reaction rate such as has something to do with it. The heat treatment time is set to an appropriate value depending on the composition and size of the R3-T3-X2 alloy sintered body, the composition of the R4-Zn alloy, the heat treatment temperature, etc., but is preferably 5 minutes or more and 10 hours or less, and 10 minutes. It is more preferably 8 hours or less and 30 minutes or more and 8 hours or less.

The R1-T1-X1 series sintered magnet obtained by the heat treatment step can be subjected to known mechanical processing such as cutting and cutting, or can be subjected to known surface treatment such as plating for imparting corrosion resistance. ..

There are still unclear points about the mechanism by which a thick two-grain boundary is formed between the crystal grains of the main phase and a very high coercive force is obtained. The mechanism considered by the present inventors based on the knowledge obtained to date will be described below. It should be noted that the following description of the mechanism is not intended to limit the scope of the present disclosure.

As described above, when the composition of the R3-T3-X2 alloy sintered body is richer in T3 than in the stoichiometric composition (R3 ₂ T3 ₁₄ X2) and X2 is made poor, a two-grain grain boundary thick by heat treatment is obtained. Can be easily obtained. In the above composition range, Pr in R4 promotes grain boundary diffusion, so that the liquid phase generated from the R2-Zn alloy is diffused and introduced to the two-grain grain boundaries inside the sintered body. Is introduced into the two-grain boundary, the main phase in the vicinity of the two-grain boundary in the sintered body is dissolved, and these easily form the R ₆ T ₁₃ Zn phase by heat treatment at 450° C. or higher and 800° C. or lower. Is stabilized. It is considered that this makes it possible to maintain a thick two-particle grain boundary even after cooling, which leads to the development of a very high coercive force. In addition, as described above, generally, X2 is not used for forming the main phase. Therefore, if [T3]/[X2] is 13.0 or more, formation of a thick two-grain grain boundary phase can be maintained. Can be realized and a high coercive force is exhibited.

On the other hand, in the composition of the R3-T3-X2 alloy sintered body, T3 is poor and X2 is richer than the stoichiometric composition (R3 ₂ T3 ₁₄ X2), and particularly [T3]/[X2] is 13.0. If it is less than 2, it becomes difficult to obtain a thick two-particle grain boundary. It is considered that this is because the once dissolved main phase (R3 ₂ T3 ₁₄ X2 phase) is likely to be reprecipitated as the main phase again, which prevents the grain boundaries from becoming thick.

In the above R ₆ T ₁₃ Zn phase (R ₆ T ₁₃ Zn compound), R is at least one of rare earth elements and always contains Pr and/or Nd, and T is at least one of transition metal elements. And always contains Fe. R ₆ T ₁₃ Zn compound is typically a _Pr 6 _Fe 13 Zn compounds. Further, the R ₆ T ₁₃ Zn compound has a La ₆ Co ₁₁ Ga ₃ type crystal structure. The R ₆ T ₁₃ Zn compound may be an R ₆ T _13-δ Zn _1+δ compound depending on its state. In the case where Cu, Al, Ga and Si are contained in R1-T1-X1 based sintered _{magnet, R 6 T 13-δ (} Zn 1-a-b-c-d Cu a Al b Si c Ga _d ) _1+δ in some cases.

The present disclosure will be described in more detail by way of examples, but the present disclosure is not limited thereto.

Experimental example 1
[Preparation of R3-T3-X2 alloy sintered body]
About No. 1 in Table 1. Each element was weighed so as to have the composition of the sintered body shown in 1-A to 1-J, and an alloy was produced by a strip casting method. After pulverizing each of the obtained alloys with hydrogen, a dehydrogenation treatment of heating in vacuum to 550° C. and then cooling was performed to obtain coarsely pulverized powder. Next, after adding zinc stearate as a lubricant to the obtained coarsely pulverized powder in an amount of 0.04 mass% with respect to 100 mass% of the coarsely pulverized powder and mixing them, nitrogen was obtained by using an air flow type pulverizer (jet mill device). Dry pulverization was performed in an air stream to obtain finely pulverized powder (alloy powder) having a pulverized particle diameter D ₅₀ of 4 μm. The crushed particle size D ₅₀ is the volume center value (volume-based median diameter) obtained by the laser diffraction method using the air flow dispersion method. In order to adjust the amount of C in the sintered body, No. 1-C and No. Carbon black was added to 1-E.

Zinc stearate as a lubricant was added to the finely pulverized powder in an amount of 0.05 mass% based on 100 mass% of the finely pulverized powder, and the mixture was molded in a magnetic field to obtain a compact. A so-called orthogonal magnetic field molding device (lateral magnetic field molding device) in which the magnetic field applying direction and the pressurizing direction are orthogonal to each other was used as the molding device.

The obtained molded body is sintered in a vacuum at a temperature of 1000° C. or higher and 1040° C. or lower (a temperature at which densification due to sintering is sufficiently caused is selected for each sample) for 4 hours, followed by rapid cooling to burn an R3-T3-X2 alloy. I got a unity. The density of the obtained sintered body was 7.5 Mg/m ³ or more. Table 1 shows the components of the obtained sintered body and the result of gas analysis (C (carbon amount)). In addition, each component in Table 1 was measured using the high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES). Moreover, C (carbon content) was measured using a gas analyzer by the combustion-infrared absorption method. In addition, as a result of measuring the oxygen content of the sintered body by a gas melting-infrared absorption method, it was confirmed that the oxygen content was all around 0.4 mass %. “[T3]/[X2]” in Table 1 indicates the analytical value (mass%) of each element (including unavoidable impurities, Al, Si, and Mn in the present experimental example) constituting T3 of the element. What was obtained by dividing by the atomic weight and summing those values (a), and what was obtained by dividing the analytical values (mass%) of B and C by the atomic weight of each element, and summing those values It is a ratio (a/b) with (b). The same applies to all the tables below. It should be noted that the total of the compositions in Table 1 does not reach 100 mass %. This is because, as described above, each component has a different analysis method, and further, components other than the components listed in Table 1 (for example, O (oxygen) and N (nitrogen)) are present. The same applies to the other tables.

[Preparation of R4-Zn alloy]
Using Pr metal and Zn metal (both of which have a purity of 99% or more), the alloys of No. 1-a was compounded so as to have the composition shown in FIG. 1-a, these raw materials were melted, and a ribbon- or flake-shaped alloy was obtained by a single-roll ultra-quenching method (melt spinning method). The obtained alloy was crushed in an argon atmosphere using a mortar and then passed through a sieve having a mesh size of 425 μm to prepare an R4-Zn alloy. Table 2 shows the composition of the obtained R4-Zn alloy.

[Heat treatment]
No. 1 in Table 1 The R3-T3-X2 alloy sintered bodies of 1-A to 1-J were cut and cut into a rectangular parallelepiped of 11.0 mm×5.0 mm×4.4 mm (orientation direction). Next, as shown in FIG. 2, a surface perpendicular to the orientation direction of the R3-T3-X2 alloy sintered body 1 (arrow direction in the figure) is R4 in the processing container 3 made of niobium foil. No. 2 shown in Table 2 so as to come into contact with the Zn-based alloy 2. The R4-Zn alloy of No. 1-a was changed to No. The R1-T3-X2 alloy sintered bodies of 1-A to 1-J were arranged above and below, respectively. In this example, “a region of the magnet surface having a thickness of 200 μm measured from the plane orthogonal to the orientation direction along the orientation direction” refers to the surface of the R3-T3-X2 alloy sintered body 1. , A region of 200 μm in thickness on the surface in contact with the R4-Zn alloy 2. Hereinafter, this area is simply referred to as "magnet surface portion".

After that, heat treatment was performed at a heat treatment temperature and time shown in Table 3 in reduced pressure argon controlled to 200 Pa using a tubular flow furnace, and then cooled. In order to remove the concentrated portion of the R4-Zn alloy existing in the vicinity of the surface of each sample after the heat treatment, the entire surface of each sample was cut using a surface grinder, and 4.0 mm x 4.0 mm x 4. A 0 mm cubic sample (R1-T1-X1 series sintered magnet) was obtained.

[sample test]
The coercive force (H _cJ ) of the obtained sample was measured with a BH tracer. The measurement results are shown in Table 3. In addition, "the example of the present invention" described in the remarks column of Table 3 means that the example satisfies the requirements defined in the present disclosure. The same applies to "examples of the present invention" in the following table. As shown in Table 3, the present invention examples (No. 1-1, 1-2, 1-6, in which the molar ratio [T1]/[X1] in the R1-T1-X1 system sintered magnet was 13.0 or more. In both 1-7 and 1-10), high H _cJ was obtained. Particularly at 14.0 or higher, extremely high H _cJ exceeding 1600 kA/m was obtained. On the other hand, in the comparative examples (No. 1-3 to 1-5, 1-8 and 1-9) in which the molar ratio of [T1]/[X1] is less than 13.0, high H _cJ was not obtained.

Among the samples shown in Table 3, No. 1 having a [T1]/[X1] mol ratio of 13.0 or more. No. 1-1 (invention example) and [T1]/[X1] having a mol ratio of less than 13.0. The cross section (cross section parallel to the orientation direction) of 1-4 (Comparative Example) was observed with a scanning electron microscope (SEM: JCM-6000 manufactured by JEOL Ltd.). As a result, No. In 1-1 (Example of the present invention), from the magnet surface portion (specifically, a position where the depth measured along the orientation direction from the surface of the magnet surface orthogonal to the orientation direction (magnetization direction) was 100 μm) 100 nm over the central portion of the magnet (where the depth measured along the orientation direction from the surface orthogonal to the orientation direction (magnetization direction) on the magnet surface is 2.0 mm, that is, the portion located in the center of the magnet) The thick two-grain grain boundaries described above were formed. On the other hand, No. In 1-4 (Comparative Example), the formation of thick two-grain grain boundaries was limited to only the magnet surface portion. Furthermore, No. which is an example of the present invention. As a result of performing energy dispersive X-ray spectroscopy (EDS) on the cross section of 1-1 with a SEM (JSM-7001F manufactured by JEOL Ltd.) attached device (JED-2300 SD10 manufactured by JEOL Ltd.), Zn was detected from the grain boundary at the center of the magnet. Was detected, and part of the content was interpreted as the R ₆ T ₁₃ Zn phase from the content.

Experimental example 2
About No. 4 in Table 4. A plurality of R3-T3-X2 alloy sintered bodies were produced in the same manner as in Experimental Example 1 except that each element was weighed so as to have the composition of the sintered body shown in 2-A. Table 4 shows the components of the obtained sintered body and the results of gas analysis (C (carbon content)).

If the alloy is No. An R4-Zn-based alloy was produced in the same manner as in Experimental Example 1 except that the compositions were changed so as to have the compositions shown in 2-a to 2-1. Table 5 shows the composition of the obtained R4-Zn alloy.

After processing a plurality of R3-T3-X2 alloy sintered bodies in the same manner as in Experimental Example 1, No. 2-a to 2-l R4-Zn alloys and No. The sample was placed so as to be in contact with the R3-T3-X2 alloy sintered body of 2-A, and heat treated and processed in the same manner as in Experimental Example 1 to obtain a sample (R1-T1-X1 sintered magnet). The obtained sample was measured by the same method as in Experimental Example 1 to obtain the coercive force (H _cJ ). The results are shown in Table 6. As shown in Table 6, 50 mol% or more of the entire R4 in the R4-Zn alloy is Pr, and R4 is in the range of 60 mol% to 85 mol% (Examples 2-3 to 2-7 and 2). -9, 2-10), high H _cJ was obtained. On the other hand, in the R4-Zn alloy, the content of R4 exceeds 85 mol%. Nos. 2-1 and 2-2, in which the contents of R4 are less than 60 mol%. 2-8, No. in which Pr is less than 50 mol% of the entire R4. No high H _cJ was obtained in any of 2-11 and 2-12.

Experimental example 3
About No. 7 in Table 7. An R3-T3-X2 alloy sintered body was produced in the same manner as in Experimental Example 1 except that each element was weighed so as to have the composition of the sintered body shown in 3-A. Table 7 shows the components of the obtained sintered body and the results of gas analysis (C (carbon amount)).

The alloys of Nos. An R4-Zn-based alloy was produced in the same manner as in Experimental Example 1 except that the components were mixed so as to have the compositions shown in 3-a to 3-d. Table 8 shows the composition of the obtained R4-Zn alloy.

After processing the R3-T3-X2 alloy sintered body in the same manner as in Experimental Example 1, No. No. 3-a to 3-d R4-Zn alloys and No. Heat treatment and processing were performed in the same manner as in Experimental Example 1 except that the R3-T3-X2 alloy sintered body of 3-A was placed in contact with the sintered body, and the heat treatment temperature shown in Table 9 was used. X1 system sintered magnet) was obtained. The obtained sample was measured by the same method as in Experimental Example 1 to obtain the coercive force (H _cJ ). The results are shown in Table 9. As shown in Table 9, a high H _cJ was obtained when the heat treatment temperature was 450° C. or higher and 800° C. or lower (the present invention example in Table 9). Particularly, higher H _cJ was obtained when the heat treatment temperature was 480°C to 560°C.

No. shown in Table 9 The cross sections (cross sections parallel to the orientation direction) of 3-2 (invention example) and 3-8 (comparative example) were observed with a scanning electron microscope (SEM: JCM-6000 manufactured by JEOL Ltd.). The results are shown in FIGS. FIG. 3-2 is a photograph of observing a magnet surface portion (a location of 100 μm from the magnet surface) of No. 3-2, and FIG. It is the photograph which observed the magnet center part (the place where the depth is 2.0 mm from the magnet surface) of 3-2. Further, FIG. 3 is a photograph of the magnet surface portion 3-8 (100 μm from the magnet surface) observed, and FIG. It is the photograph which observed the center part (2.0 mm from the magnet surface) of the magnet of 3-8. As shown in FIGS. In No. 3-2 (Example of the present invention), thick two-grain grain boundaries of 100 nm or more were formed in both the magnet surface portion shown in FIG. 3 and the magnet central portion shown in FIG. In 3-8 (Comparative Example), a thick two-particle grain boundary of 100 nm or more was not obtained in the central portion of the magnet shown in FIG.

Experimental example 4
No. shown in Table 6 Sections of 2-3, 2-5, 2-6, 2-9, 2-10 (all are examples of the present invention) and Nos. 2-11, 2-12 (all are comparative examples) (sections parallel to the alignment direction) Was observed with a scanning electron microscope (SEM: JSM-7001F manufactured by JEOL Ltd.), and the magnet surface portion (a location 100 μm from the magnet surface, that is, a range from the magnet surface to a depth 200 μm) and the magnet central portion (2 Energy dispersive X-ray spectroscopy (EDS) was carried out at a location of 0.0 mm or more, that is, a portion located in the center of the magnet, using an accessory (JED-2300 SD10) to determine the composition. The area in which EDS is performed has a size of 50 nm×50 nm as shown in FIG. The results obtained are shown in Table 10. As shown in Table 10, No. In any of 2-3, 2-5, 2-6, 2-9, 2-10, and 2-11, the concentration of Pr is higher in the magnet surface portion than in the magnet central portion (3.0 mass% or more). The concentration of Zn is higher (1.0 mass% or more) in the magnet surface portion than in the magnet central portion. In addition, No. Regarding the Pr concentration of 2-12, there was no difference between the central part of the magnet and the surface part of the magnet (all were 0 mass%). This is No. 12 is because R4 in the R4-Zn alloy is Nd and does not contain Pr. In addition, No. It can be seen that in Nos. 2-11 and 2-12, Zn did not diffuse to the central portion of the magnet (Zn in the central portion of the magnet was 0 mass%).

Furthermore, No. 2-6 (Example of the present invention), No. 2-11 (comparative example) and No. The cross section (cross section parallel to the orientation direction) in 2-12 (Comparative Example) was observed with a scanning electron microscope (SEM: JSM-7001F manufactured by JEOL Ltd.), and No. No. 2-6 magnet center (at a position of 2.0 mm or more from the magnet surface), and No. 2-6. 2-11 and No. In the magnet surface part 2-12 (100 μm from the magnet surface), energy dispersive X-ray spectroscopy (EDS) was carried out using an accessory (JED-2300 SD10) to determine the composition of the local region. 8 to 10 show the location of the local region where the EDS was performed (No. 2-6 is FIG. 8, No. 2-11 is FIG. 9, No. 2-12 is FIG. 10). In addition, Table 11 to Table 13 show the respective analysis results. Moreover, when the crystal structure was identified for the area indicated by number 5 in FIG. 8-10, a field emission transmission electron microscope: _La 6 Co from the diffraction pattern with (FE-TEM Hitachi High Technologies Ltd. HF-2100) It was shown to have an ₁₁ Ga ₃ type crystal structure, and it was confirmed from the composition ratio that it was a (Nd, Pr) ₆ Fe ₁₃ Zn phase. Further, as shown in Tables 11 to 13, the (Nd, Pr) ₆ Fe ₁₃ Zn phase (R ₆ Fe ₁₃ Zn phase in Table 11) in the present invention example (Table 11) is R (Nd and Pr). with respect to the total of more than 50 mol% that is located R2-T2-a compound with Pr, _R 6 _Fe 13 Zn phase in Comparative example (tables 12 and 13) is less than the overall R 50 mol There are at Pr R2-T2 Not the -A compound.

The RTB-based sintered magnet obtained according to the present disclosure is applied to various motors such as a voice coil motor (VCM) of a hard disk drive, an electric vehicle (EV, HV, PHV, etc.) motor, a motor for industrial equipment, and the like. It can be suitably used for home electric appliances and the like.

1 R3-T3-X2 type alloy sintered body 2 R2-Zn type alloy 3 Processing container

Claims (8)

R1: 27 mass% or more and 35 mass% or less (R1 is at least one kind of rare earth element, 50 mass% or more of R1 as a whole is Nd, and always contains Pr),
X1: 0.85 mass% or more and 0.93 mass% or less (X1 is B or B and C),
Zn: 0.3 mass% or more and 2.0 mass% or less,
T1: 61.5 mass% or more (T1 is Fe or Fe and M, M is Ga, Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Ge, Zr, Nb, Mo, Ag One or more selected from, and 80 mass% or more of the total T1 is Fe),
Containing
The molar ratio of T1 to X1 ([T1]/[X1]) is 13.0 or more,
The Pr concentration and the Zn concentration in a region of the magnet surface having a thickness of 200 μm measured from the plane orthogonal to the orientation direction along the orientation direction are higher than the Pr concentration and the Zn concentration in the magnet central part, respectively.
R2-T2-A compound (R2 is at least one of rare earth elements, and 50 mol% or more of the entire R2 is Pr. T2 is at least one of Fe, Co, Ni, Mn, Ti, and Cr. And 50% by mole or more of T2 is Fe. A is at least one of Zn, Cu, Ga, Al, Ge and Si, and 50% by mole or more of A is Zn). R1-T1-X1 system sintered magnet. The R1-T1-X1 system sintered magnet according to claim 1, wherein the Pr concentration in the region is higher than the Pr concentration in the central portion of the magnet by 3.0 mass% or more. The R1-T1-X1 system sintered magnet according to claim 1 or 2 whose Zn concentration in said field is 1.0 mass% or more higher than Zn concentration in said magnet central part. The R1-T1-X1 system sintered magnet according to any one of claims 1 to 3, wherein a molar ratio of T1 to X1 ([T1]/[X1]) is 14.0 or more. Wherein R2-T2-A _compounds have a La _{6 Co} 11 Ga ₃ type crystal structure, R1-T1-X1 based sintered magnet according to any one of claims 1 to 4. The R1-T1-X1 system sintered magnet according to any one of claims 1 to 5, wherein the R2-T2-A compound is present in at least a grain boundary in a central portion of the magnet. The thickness of the said grain boundary of the said magnet center part is 100 nm or more, The R1-T1-X1 type|system|group sintered magnet of Claim 6 . Wherein R2-T2-A compound _is formed from R _{6 T} 13 Zn phase, R1-T1-X1 based sintered magnet according to any one of claims 1 to 7.