Anisotropic rare earth sintered magnet and method for producing the same

Abstract

The anisotropic rare-earth sintered magnet of the present invention is characterized in that it is an anisotropic rare-earth sintered magnet composed of a compound represented by the formula (R 1‑a Zr a ) x (Fe 1‑b Co b ) 100‑x‑y (M 1 1‑c M 2 c ) y R is one or more selected from rare-earth elements and must contain Sm, M 1 is one or more selected from V, Cr, Mn, Ni, Cu, Zn, Ga, Al, Si, M 2 is one or more selected from Ti, Nb, Mo, Hf, Ta, W, x, y, a, b, c are as follows: 7 ≤ x ≤ 15 atom%, 4 ≤ y ≤ 20 atom%, 0 ≤ a ≤ 0.2, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.9, and the main phase contains 80% or more by volume of a compound composed of ThMn 12 type crystals, the average crystal grain size of the main phase is 1 μ μm or more, and a R-rich phase and a R(Fe, Co)2 phase are contained in the grain boundary portion. The manufacturing method of the anisotropic rare-earth sintered magnet of the present invention is characterized in that an alloy containing a compound phase of ThMn 12 type crystals is pulverized, and powder compression molding is performed in a state where a magnetic field is applied to make a molded body, and then sintering is performed at a temperature of 800°C or higher and 1400°C or lower. According to the present invention, an anisotropic rare-earth sintered magnet showing good magnetic properties and a manufacturing method thereof can be provided in an anisotropic rare-earth sintered magnet in which a compound of ThMn 12 type crystals is the main phase.

Description

TECHNICAL FIELD

[0001] The present application relates to an anisotropic rare earth sintered magnet having a compound of ThMn 12 as a main phase, and a manufacturing method thereof. BACKGROUND

[0002] Rare earth magnets, particularly Nd-Fe-B sintered magnets, are expected to be increasingly demanded and produced in the future, against the background of the electrification of automobiles or the high performance / saving of power of industrial motors. On the other hand, there is a concern that the supply and demand balance of rare earth raw materials will be disrupted in the future, and therefore, in recent years, research on saving of rare earth for rare earth magnets has been attracting attention. Among them, a compound having a ThMn 12 crystal structure is less in rare earth content and also good in magnetic properties compared to R2Fe 14 B compounds, and therefore, is being actively researched as a next-generation magnet material.

[0003] For example, in Patent Literature 1, a permanent magnet composed of an alloy including a hard magnetic phase having a ThMn 12 type tetragonal crystal structure and a non-magnetic phase is reported. It is shown here that the phase having a lower melting point than the main phase and being non-magnetic is precipitated mainly by adding at least one element selected from Cu, Bi, Mg, Sn, Pb, and In to an intermetallic compound composed of rare earth elements-Fe.

[0004] In addition, in Patent Literature 2, a rare earth permanent magnet having a main phase and a grain boundary phase is reported, the main phase being an R-T compound (R is one or more rare earth elements necessarily containing La, and T is Fe, or Fe and Co, or an element partially substituted with M (one or more selected from Ti, V, Cr, Mo, W, Zr, Hf, Nb, Ta, Al, Si, Cu, Zn, Ga, and Ge)) having a ThMn 12 type crystal structure, and the grain boundary phase being a cubic crystal structure, having a La-rich phase σ of 20% or more in cross-sectional area ratio, in which the La composition ratio is 20 at% or more. By including a non-magnetic cubic crystal structure La-rich phase in the grain boundary portion, a magnetic separation effect between the main phases and an interface strain reduction effect of the grain boundary phase and the main phase can be obtained.

[0005] In Patent Literature 3, a rare earth magnet having a main phase having a ThMn 12 type crystal structure and a secondary phase is reported, the secondary phase including any one of a Sm5Fe 17 system phase, a SmCo5 system phase, a Sm2O3 system phase, and a Sm7Cu3 system phase, and the volume fraction of the secondary phase being 2.3 to 9.5%. Among these secondary phases, the Sm5Fe 17The SmCo5 phase is a magnetic phase that exhibits higher magnetic anisotropy than the main phase, and separates the grains of the main phase, thereby preventing the movement of the magnetic domain wall within the main phase, and thus improving the magnetization and coercive force of the magnet. On the other hand, the Sm2O3 phase and the Sm7Cu3 phase are non-magnetic phases, and separate the grains of the main phase, thereby preventing the propagation of the magnetization reversal of the main phase to the surroundings, and thus improving the magnetization and coercive force of the magnet. In addition, it is described that the Sm7Cu3 phase is a non-equilibrium phase.

[0006] In Patent Literature 4, an alloy for a rare earth magnet having a main phase and one or more auxiliary phases, the composition of the entire alloy satisfying R(Fe, Co) w-z Ti z Cu α (R is at least one kind of rare earth element, 8≤w≤13, 0.42≤z<0.70, 0.40≤α≤0.70). In addition, it is described that the auxiliary phase is mainly a crystal phase composed of Cu in 50 mol% or more of the entire auxiliary phase, and the crystal structure of the auxiliary phase is KHg2 type.

[0007] In Patent Literature 5, a rare earth permanent magnet is reported, which is R x Fe 100-x-y (V 1-a Si a ) y (R is one or two or more kinds of rare earth elements including Y, x = 5.5 to 18 atom%, y = 8 to 20 atom%, a = 0.05 to 0.7), and the main phase has a ThMn 12 type body-centered tetragonal crystal structure. It is described that the composition alloy is composed of a main phase and a rare earth-rich phase, and does not contain an RFe2 phase.

[0008] Prior Art Documents

[0009] Patent Literature

[0010] Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No. 2001-189206;

[0011] Patent Literature 2: International Publication No. WO 2017 / 164312;

[0012] Patent Literature 3: Japanese Patent Application Laid-Open (JP-A) No. 2017-112300;

[0013] Patent Literature 4: Japanese Patent Application Laid-Open (JP-A) No. 2019-044259;

[0014] Patent Literature 5: Japanese Patent Application Laid-Open (JP-A) No. Hei 06-231920. SUMMARY

[0015] PROBLEMS TO BE SOLVED BY THE INVENTION

[0016] As described above, in order to obtain good magnetic properties in a magnet in which a compound of ThMn 12 In order to obtain good magnetic properties in a magnet in which a compound of ThMn

[0017] In addition, in Patent Document 3, a magnetic phase of Sm5Fe 17 encloses the surface of a crystal grain of the main phase, and improves the coercive force by pinning a magnetic domain wall with the phase. However, Sm5Fe 17 The Sm5Fe 12 type compound, and thus it is difficult to realize a structure in which the surface of a crystal grain of the main phase is enclosed by these phases.

[0018] On the other hand, in Patent Document 5, an alloy composed of a ThMn 12 main phase and an R-rich phase is suggested. However, the range of the composition in which only two phases are formed in the R-Fe-V-Si quaternary system is extremely limited, and thus it is difficult to produce the structure with good reproducibility.

[0019] The present application has been achieved in view of the above-described problems, and an object thereof is to provide an anisotropic rare earth sintered magnet having good magnetic properties and in which a compound of a ThMn 12 type crystal is a main phase.

[0020] Means for solving the problems

[0021] The present inventors have intensively studied in order to achieve the above-described object, and as a result, it has been found that in an anisotropic rare earth sintered magnet in which a compound of a ThMn 12 type crystal is a main phase, a high coercive force is exhibited when an R-rich phase and an R(Fe, Co)2 phase exist at a grain boundary portion, and thus the present application has been completed.

[0022] Therefore, the present application provides the following anisotropic rare earth sintered magnet and a method for producing the same.

[0023] (1) An anisotropic rare earth sintered magnet, characterized by being composed of a compound of a ThMn 1-a Zr a ) x (Fe 1- b Co b ) 100-x-y (M1 1-c M 2 c ) y The term refers to anisotropic rare-earth sintered magnets, where R is selected from one or more rare-earth elements and must contain Sm and M. 1 M is selected from one or more elements chosen from V, Cr, Mn, Ni, Cu, Zn, Ga, Al, and Si. 2 For elements selected from Ti, Nb, Mo, Hf, Ta, and W, x, y, a, b, and c are as follows: 7 ≤ x ≤ 15 atomic percentage, 4 ≤ y ≤ 20 atomic percentage, 0 ≤ a ≤ 0.2, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.9, wherein the element containing more than 80% by volume of ThMn is... 12 The main phase is composed of a compound of the crystalline form, and the average crystal grain size of the main phase is 1. μ Above m, the grain boundary contains R-rich phase and R(Fe, Co)2 phase.

[0024] (2) (1) The anisotropic rare earth sintered magnet is characterized by: containing a total volume percentage of more than 1% of the above-mentioned R-rich phase and R(Fe, Co)2 phase.

[0025] (3) The anisotropic rare earth sintered magnet described in (1) or (2) is characterized in that: the R-rich phase contains more than 40 atomic% R.

[0026] (4) Anisotropic rare earth sintered magnets as described in any one of (1) to (3), characterized in that: the R(Fe, Co)2 phase exhibits ferromagnetism or subferromagnetism at temperatures above room temperature.

[0027] (5) Anisotropic rare earth sintered magnets as described in any one of (1) to (4), characterized in that: the Sm / R ratio inside the main phase grains is lower than the Sm / R ratio of the R-rich phase and the R(Fe, Co)2 phase.

[0028] (6) Anisotropic rare earth sintered magnets as described in any one of (1) to (5), characterized in that: the Sm / R ratio inside the main phase grain is lower than the Sm / R ratio of the outer shell of the main phase grain.

[0029] (7) (5) or (6) The anisotropic rare earth sintered magnet is characterized in that: Sm is not present inside the main phase grains.

[0030] (8) Anisotropic rare earth sintered magnets as described in any one of (1) to (7), characterized in that: they exhibit a coercive force of 5 kOe or more at room temperature, and the temperature coefficient β of the coercive force is -0.5% / K or more.

[0031] (9) The method for producing the anisotropic rare-earth sintered magnet according to any one of (1) to (8), characterized by: pulverizing an alloy containing a compound phase of a ThMn 12 crystal, and performing powder compression molding in a state where a magnetic field is applied to produce a molded body, and thereafter sintering at a temperature of 800°C or higher and 1400°C or lower.

[0032] (10) The method for producing the anisotropic rare-earth sintered magnet according to (9), characterized by: pulverizing and mixing an alloy containing a compound phase of a ThMn 12 crystal, and performing powder compression molding in a state where a magnetic field is applied to produce a molded body, at a higher R composition ratio and Sm / R ratio than the alloy.

[0033] (11) The method for producing the anisotropic rare-earth sintered magnet according to (9) or (10), characterized by: bringing a material containing Sm into contact with a sintered body in which a compound phase of a ThMn 12 crystal is a main phase, and performing heat treatment at a temperature of 600°C or higher and lower than the sintering temperature to diffuse Sm into the sintered body.

[0034] (12) The method for producing the anisotropic rare-earth sintered magnet according to (11), characterized in that the material containing Sm brought into contact with the sintered body is one or more selected from the group consisting of Sm metal, an alloy containing Sm, a compound containing Sm, and a vapor containing Sm, and the form thereof is one or more selected from the group consisting of a powder, a thin film, a thin ribbon, a foil, and a gas.

[0035] (13) The method for producing the anisotropic rare-earth sintered magnet according to any one of (9) to (12), characterized by: performing heat treatment on the sintered body at a temperature of 300°C to 900°C.

[0036] Effects of the Invention

[0037] According to the present invention, in an anisotropic rare-earth sintered magnet in which a compound of a ThMn 12 crystal is a main phase, an anisotropic rare-earth sintered magnet exhibiting excellent magnetic properties can be obtained. DETAILED DESCRIPTION

[0038] Hereinafter, an embodiment of the present invention will be described. The magnet of the present invention is an anisotropic rare-earth sintered magnet, the composition of which is represented by the following formula:

[0039] (R 1-a Zr a ) x (Fe 1-b Co b ) 100-x-y (M 1 1-cM 2 c ) y

[0040] ThMn 12 The compound of ThMn 12 The compound of ThMn μ m or more, and a R(Fe, Co)2 phase in the grain boundary portion. Hereinafter, first, each component will be described. Note that x, y, a, b, and c are as follows: 7 ≤ x ≤ 15 atom%, 4 ≤ y ≤ 20 atom%, 0 ≤ a ≤ 0.2, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.9, respectively.

[0041] Note that the R-rich phase is a phase in which the concentration of rare earth elements is higher than that of the main phase. In addition, the R(Fe, Co)2 phase is a compound phase having a MgCu2 structure, which is called a Laves phase. Thus, since the composition range is wide, it is easy to produce the anisotropic rare earth sintered magnet of the present application with good reproducibility.

[0042] R is one or more elements selected from rare earth elements, and Sm must be contained. Specifically, R must contain Sm, and one or more elements selected from Sc, Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu can be combined with Sm. R is an element necessary for forming a compound having a ThMn 12 The content of R is set to 7 atom% or more and 15 atom% or less. If it is 8 atom% or more and 12 atom% or less, it is more preferable. If it is less than 7 atom%, an α-Fe phase is precipitated, and sintering is difficult, on the other hand, if it exceeds 15 atom%, the volume ratio of the ThMn 12 type compound phase decreases, and good magnetic properties cannot be obtained. The ThMn 12 type compound shows particularly high anisotropic magnetic field H A Therefore, the anisotropic rare earth sintered magnet of the present application must contain Sm. In the case where there is no difference in Sm concentration in the inside and the shell portion of the main phase crystal grains, the Sm contained in R is preferably 5% or more of R in terms of atomic ratio, and if it is 10% or more, it is further preferable, and particularly preferably 20% or more. By making the Sm ratio in such a range, the increasing effect of H A is sufficient, and a high coercive force can be obtained.

[0043] On the other hand, compared with Y, La, Ce, Pr, Nd, etc., Sm is less produced and resources are limited, and therefore it is preferable to effectively use Sm as much as possible. For this reason, an organization form in which Sm is enriched in the shell portion of the main phase crystal grains can be formed to obtain a high coercive force with a small amount of Sm. In this case, in the case of an organization in which the Sm concentration is different between the inside and the shell portion of the main phase crystal grains, it is preferable that the Sm contained in R be 0.1 atomic% or more and 50 atomic% or less of R in terms of atomic ratio. It is further preferable that it be 0.2 atomic% or more and 40 atomic% or less, and particularly preferably 0.5 atomic% or more and 30 atomic% or less. It is more preferable if R is a combination of one or more elements selected from Y, La, Ce, Pr, Nd, and Sm.

[0044] Zr substitution ThMn 12 R of the compound of the type (ThMn 12 H of the compound of the type (ThMn A decreases, and it is difficult to obtain a high coercive force.

[0045] In order to stably exist the crystal structure of the type (ThMn 12 It is known that R, Fe, and a third element M are required as constituent elements. In the anisotropic rare earth sintered magnet of the present application, M 1 is one or more elements selected from V, Cr, Mn, Ni, Cu, Zn, Ga, Al, and Si, and functions as the third element. M 2 compared with M 1 is an element that shows a tendency to more easily form a compound with R than with Fe, or does not easily combine with either Fe or R. One of the features of the anisotropic rare earth sintered magnet of the present application is that, in the magnet organization, in addition to the ThMn 12 compound of the type (ThMn 1 by selecting M 1 as the third element, an organization in which the three phases stably coexist is easily obtained. If M 2 and M 1 are collectively denoted as M, M 1 is at least 10% or more of M in terms of atomic ratio. It is more preferable if it is 30% or more, and further preferable if it is 50% or more. If M 1 is less than 10%, the R-rich phase among the above three phases cannot be stably formed. In addition, as M 2 M, which is the total of M 12If the main phase of a type of compound exceeds 20 atomic percent, the amount of heterogeneous phase formation increases, and it cannot exhibit good magnetic properties.

[0046] M 2 It is one or more elements selected from Ti, Nb, Mo, Hf, Ta, and W. M 2 It also has the ability to make ThMn 12 The effect of stabilizing the crystal structure is good, but if it is excessive, then M... 2 Carbides of C phase or MgZn2 type compounds, i.e. (Fe, Co)2M 2 The phase precipitates within the main phase or at grain boundaries. This is especially true for (Fe, Co)₂M. 2 Sometimes, phases, such as the Fe₂Ti phase, can form a Fe-rich composition due to stoichiometric composition, exhibiting ferromagnetism, which adversely affects the magnetic properties of sintered magnets. Furthermore, when only M is selected... 2 As the third element, it does not contain M. 1 In such cases, R-rich phases are not easily and stably formed. Therefore, in the presence of M... 2 In the case of the composition, its content, in terms of atomic ratio, shall be at least 90% or less of M.

[0047] The anisotropic rare-earth sintered magnet of the present invention will have R, M 1 Along with Fe, it is an essential constituent element. Co can also replace some of the Fe. Substitution with Co improves the composition of the main phase, namely ThMn. 12 Curie temperature T of type compounds c Increase saturation magnetization M s The effect. The substitution rate of Co is set to below 50% based on atomic ratio. If the substitution rate exceeds 50%, then M... s Instead, it decreased. The ratio of Fe to Co was set as R, Zr, M. 1 and M 2 The remaining amount. However, in addition, it may contain a total of up to 3% by weight of unavoidable impurities from raw materials or introduced during the manufacturing process, specifically H, B, C, N, O, F, P, S, Mg, Cl, Ca, etc.

[0048] Next, the phases constituting the anisotropic rare earth sintered magnets of the present invention will be described.

[0049] The main phase in the anisotropic rare-earth sintered magnet of the present invention is composed of ThMn 12 R(Fe, Co, M) crystal structure 12The compound constitutes. It is preferable that the main phase does not contain elements such as C, N, and O, which are inevitably mixed by the process of producing a sintered magnet. However, in the composition analysis using an EPMA (electron probe microanalyzer), in the case where C, N, and O elements are detected due to the influence of measurement deviation, the adjustment method of observing a sample, or the detection signal of other elements, or the like, from the viewpoint of obtaining H A of the main phase, the upper limit thereof is preferably 1 atomic% or less, respectively. The average crystal grain diameter of the main phase is preferably 1 μ μm or more, and preferably 1 μ μm or more and 30 μ μm or less. Further preferably, it is in the range of 1.5 μ μm or more and 20 μ μm or less, and particularly preferably 2 μ μm or more and 10 μ μm or less. By setting the average crystal grain diameter to such a range, the decrease in residual magnetic flux density B r or the decrease in coercive force H cJ caused by the decrease in orientation degree of the crystal grains can be suppressed. From the viewpoint of obtaining good B r or H cJ , the volume fraction of the main phase with respect to the entire magnet is 80 vol% or more, preferably 80 vol% or more and less than 99 vol%, and further preferably 90 vol% or more and 95 vol% or less.

[0050] Note that the average crystal grain diameter of the main phase is a value measured by the following operation.

[0051] The cross section of the polished sintered magnet was mirror-finished, and then immersed in an etching solution (a mixed solution of nitric acid, hydrochloric acid, and glycerin, or the like) to selectively remove the grain boundary phase. The cross section was observed using a laser microscope at 10 or more arbitrary points. From the obtained observation images, the cross-sectional area of each particle was calculated by image analysis, and the average diameter when they are regarded as a circle was taken as the average crystal grain diameter.

[0052] In addition, the volume fraction of the main phase is a value measured by the following operation.

[0053] The microstructure observation and the composition analysis of each phase of the anisotropic rare-earth sintered magnet were performed using an EPMA, and the main phase, the R-rich phase, and the R(Fe, Co)2 phase were confirmed. Thereafter, the volume fraction of each phase was calculated as a value equivalent to the area ratio in the image of the reflection electron image.

[0054] To effectively utilize Sm, a microstructure with the following grain structure can be formed: Sm is enriched in the outer shell of the main phase grains, and the Sm concentration inside the main phase grains is lower than the Sm concentration in the outer shell. In this case, the thickness of the high-Sm outer shell is not particularly limited, but from the viewpoint of fully obtaining the effect of suppressing the nucleation of antimagnetic domains in the outer shell of the main phase grains, and from the viewpoint of suppressing the inability to fully obtain the Sm reduction effect due to the increase in the overall Sm content of the sintered body, a thickness of 1 nm to 2 nm is preferred. μ m, if it is 2nm~1 μ m is particularly preferred. This morphology is achieved by making the Sm / R ratio (the atomic ratio of Sm to R) in the R-rich phase or R(Fe, Co)2 phase higher than the Sm / R ratio inside the main phase grains. It is even more preferred if the structure does not contain Sm inside the main phase grains. In addition, it may contain a portion of main phase grains with a uniform distribution of Sm concentration.

[0055] R-rich phases and R(Fe, Co)2 phases form at the grain boundaries of the magnetic structure. These grain boundaries contain not only inter-particle grain boundary phases but also grain boundary triple points. Here, R-rich phases refer to phases containing 40 atomic% or more of R. The inventors discovered that when M is included... 1 When the elements are composed as described above, it is easy to obtain magnets containing three phases: the main phase, the R(Fe, Co)2 phase, and the R-rich phase. For example, in the absence of M... 1 In sintered magnets of the Sm-Fe-Ti ternary system, Sm(Fe, Ti) is present. 12 The compositional region is in equilibrium between the main phase and the three phases SmFe2 and Fe2Ti (excluding oxides, etc.), but Sm(Fe, Ti) is also present. 12 The main phase and the Sm-rich phase are difficult to reach equilibrium at temperatures below 400℃, therefore the Sm-rich phase cannot form as a stable phase. In contrast, when M is used as... 1 In the case of a Sm-Fe-V ternary system containing V as one of the elements, a Sm-rich phase with a high concentration of Sm is formed, which can yield Sm(Fe, V) present. 12 Magnets containing three phases: SmFe2 and Sm-rich phase. Additionally, magnets containing M... 1 M 2 In the Sm-Fe-V-Ti quaternary system of both, Sm(Fe, V, Ti) 12 The four phases, Fe2(V, Ti), SmFe2, and Sm-rich phase, can exist stably. In the anisotropic rare-earth sintered magnet of the present invention, based on the understanding that in order to form R-rich and R(Fe, Co)2 phases at grain boundaries, a specified amount of M is selected. 1 The composition of elements.

[0056] The R-rich phase and the R(Fe, Co)2phase have four effects. The first effect is an effect of promoting sintering. Both the R-rich phase and the R(Fe, Co)2phase melt to form a liquid phase at the sintering temperature, and thus liquid phase sintering proceeds, and sintering is completed quickly compared with solid phase sintering in the case where these phases are not contained. In addition, because the R-rich phase and the R(Fe, Co)2phase coexist, the liquid phase generation temperature shows a tendency to decrease compared with the case where only one phase is present, and liquid phase sintering proceeds more quickly.

[0057] The second effect is cleaning of the main phase grain surface. Because the anisotropic rare earth sintered magnet of the present application has a nucleation type coercive force mechanism, it is desirable that the main phase grain surface be smooth in order to make nucleation of the reverse domain less likely to occur. The R-rich phase and the R(Fe, Co)2phase function to smooth the grain surface of the ThMn 12 type compound during the sintering process or the aging process thereafter, and because of this cleaning effect, nucleation of the reverse domain, which is a factor of coercive force decrease, is suppressed. In particular, the R(Fe, Co)2phase has a higher wettability with respect to the ThMn 12 phase than other phases, such as RM3, RM2, R(Fe, Co)M, or R(Fe, Co)2M2, etc., and easily coats the surface of the main phase grain, and thus has a large cleaning effect.

[0058] The third effect is formation of a two-grain boundary phase between the two grains. In a magnet containing the R-rich phase in the structure, by performing an optimum sintering treatment or aging treatment, a two-grain boundary phase containing more R than the main phase is formed between the main phase grains of the ThMn 12 type compound adjacent to each other. Thereby, the magnetic interaction between the main phase grains is weakened, and the sintered magnet shows a high coercive force. However, only the ThMn 12 type compound main phase and the R-rich phase, the composition region of the equilibrium of these two phases is very limited, and thus it is difficult to stably produce such a magnet if the composition deviation is considered. By producing a magnet containing the ThMn 12 type compound main phase, the R-rich phase, and the R(Fe, Co)2phase, a structure in which the main phase grain surface is coated with the two-grain boundary phase can be stably formed. In addition, in a magnet in which the R-rich phase is not present, the two-grain boundary phase is not easily formed, or the two-grain boundary phase cannot easily coat the surface of the main phase grain, and thus a magnet showing a sufficient coercive force is not easily obtained.

[0059] The fourth effect is to increase the Sm concentration at grain boundaries. When a grain boundary diffusion method is used to create a microstructure with different Sm concentrations inside and outside the main phase grains, the R-rich phase and R(Fe, Co)2 phase present at the grain boundaries become liquid phases during diffusion treatment, allowing Sm deposited on the sintered body to diffuse and penetrate inwards. Therefore, the Sm / R ratio of at least one of the R-rich phases or R(Fe, Co)2 phases is higher than that inside the main phase grains. Furthermore, when a two-alloy method is used as the manufacturing method, by using ThMn... 12 For alloys dominated by compound phases and alloys with high R composition ratios and Sm / R ratios, the Sm / R ratio of at least one of the R-rich phases or R(Fe, Co)2 phases in the sintered body is higher than the Sm / R ratio inside the main phase grains. Through Sm enrichment in the R-rich phases or R(Fe, Co)2 phases, the Sm concentration in the outer shell of the main phase grains in contact with these grain boundary phases also increases. A The coercivity of the sintered magnet increases.

[0060] As described above, the R-rich phase is a phase containing at least 40 atomic% R. If R is less than 40 atomic%, the wettability with the main phase is insufficient, and the aforementioned effect is not easily obtained. It is further preferred to contain 50 atoms or more of R, and it is particularly preferred to contain 60 atoms or more. The R-rich phase can be a metallic R phase such as the Sm phase described above, or it can be an amorphous phase or an intermetallic compound with a high R composition and low melting point, such as R3(Fe, Co, M), R2(Fe, Co, M), R5(Fe, Co, M)3, or R(Fe, Co, M). Furthermore, it may contain a total of up to 60 atomic% Fe, Co, M elements, or impurity elements such as H, B, C, N, O, F, P, S, Mg, Cl, and Ca.

[0061] On the other hand, the R(Fe,Co)2 phase is a Laves compound of MgCu2-type crystals. However, when performing compositional analysis using EPMA or similar methods, considering measurement biases, it refers to a phase containing 20 atomic% or more but less than 40 atomic% R. Furthermore, some Fe and Co can be substituted with element M. However, the amount of M substitution is set within the range that maintains the MgCu2-type crystal structure.

[0062] In the anisotropic rare-earth sintered magnets of this invention, the R(Fe, Co)2 phase is a magnetic phase. The magnetic phase referred to here is one exhibiting ferromagnetism or ferrimagnetism and having a Curie temperature Ti. c It is a phase at room temperature (23°C) or above. RFe2 excluding CeFe2 T c All are above room temperature. If more than 10% of R is replaced by other elements, then the T of CeFe2... c Also above room temperature. On the other hand, RCo2, except for GdCo2, has a Tc are paramagnetic at room temperature or below, but in the anisotropic rare earth sintered magnet of the present application, since the atomic ratio of Fe substituted with Co is 0.5 or less, the R(Fe, Co)2phase becomes a magnetic phase in most cases. Generally, the soft magnetic phase contained in the structure tends to adversely affect the magnetic properties, but in the anisotropic rare earth sintered magnet of the present application, it is considered that the cleaning effect of the main phase grain surface or the effect of forming a grain boundary phase between two particles by the R(Fe, Co)2phase is greater, and even if it is a magnetic phase, it contributes to an increase in coercive force.

[0063] The total amount of the R-rich phase and the R(Fe, Co)2phase is preferably 1 vol% or more, more preferably 1 vol% or more and less than 20 vol%. Further, it is further preferably in the range of 1.5 vol% or more and less than 15 vol%, and more further preferably in the range of 2 vol% or more and less than 10 vol%. By being in such a range, the area in contact with the main phase grain is ensured, and the effect of easily obtaining H cJ increase is obtained. In addition, the decrease in B r is also suppressed, and the desired magnetic properties are easily obtained.

[0064] Further, in the anisotropic rare earth sintered magnet of the present application, R oxides, R carbides, R nitrides, M carbides, etc. formed from C, N, O inevitably mixed therein can be contained. From the viewpoint of suppressing the deterioration of the magnetic properties, the volume ratio thereof is preferably 10 vol% or less, further preferably 5 vol% or less, and particularly preferably 3 vol% or less.

[0065] The phases other than the above are preferably as little as possible, and for example, in the case where the R2(Fe, Co, M) 17 phase, the R3(Fe, Co, M) 29 phase exist in the magnet structure, from the viewpoint of suppressing the influence on the magnetic properties and the coercive force decrease caused thereby, the amount of formation thereof is preferably less than 1 vol% respectively. In addition, from the viewpoint of ensuring a sufficient main phase ratio, the (Fe, Co)2M phase or RM3, RM2, R(Fe, Co)M, R(Fe, Co)2M2, etc. in which R is less than 40 at% is also preferably less than 1 vol% respectively. The total amount of these phases is preferably 3 vol% or less. Furthermore, from the viewpoint of preventing a significant decrease in the magnetic properties, it is preferred that the α-(Fe, Co) phase is not contained in the anisotropic rare earth sintered magnet of the present application.

[0066] Next, the manufacturing method will be described. The anisotropic rare earth sintered magnet of the present application is manufactured by a powder metallurgy method. First, in order to produce a raw material alloy, metal raw materials, alloys, ferrous alloys, etc. of R, Fe, Co, M are used, and adjustments are made in consideration of raw material loss, etc. in the manufacturing process, so that the final sintered body becomes a prescribed composition. These raw materials are melted in a high frequency furnace or an electric arc furnace, etc. to produce an alloy. Cooling from the metal melt can be performed by casting, or thin strip continuous casting to produce a thin sheet. In the case of thin strip continuous casting, it is preferable to adjust the cooling speed to produce an alloy so that the average crystal grain size of the main phase, or the average grain boundary phase spacing is 1 μ m or more. If it is less than 1 μ m, the powder after fine pulverization forms a polycrystal, and the main phase crystal grains are not sufficiently oriented in the process of molding in a magnetic field, resulting in a decrease in B r In the case where α-Fe is precipitated in the alloy, after removing the α-Fe, heat treatment can be performed on the alloy to increase the amount of formation of ThMn 12 type compound phases. In addition, the alloy can use an alloy of a single composition, or adjustments can be made by preparing a plurality of alloys of different compositions and mixing the powders thereof in a subsequent process.

[0067] The above raw material alloy is coarsely pulverized by mechanical pulverization using a Braun grinder, etc. or hydrogenation pulverization, etc. to form a powder having an average particle size of 0.05 to 3 mm. Alternatively, the HDDR method (hydrogen disproportionation desorption recombination method) used for the manufacturing method of Nd-Fe-B based magnets can be applied. The coarse powder is further fine pulverized using a ball mill or a jet mill using high pressure nitrogen, etc. to produce a powder having an average particle size of 0.5 to 20 μ m, more preferably 1 to 10 μ m. Note that a lubricant, etc. can be added as needed before and after the fine pulverization process. Next, using a magnetic field pressurization device, the alloy powder is oriented while being molded in a state where a magnetic field is applied, to produce a green compact. In order to suppress oxidation of the alloy powder, it is preferable to perform the molding in a vacuum, a nitrogen gas environment, an inert gas environment such as Ar, etc.

[0068] The process of sintering the green compact is performed using a sintering furnace in a vacuum or an inert environment at a temperature of 800°C or higher and 1400°C or lower. If it is lower than 800°C, sintering does not sufficiently proceed, and thus a high sintering density cannot be obtained, and if it exceeds 1400°C, ThMn 12The main phase of the compound decomposes, and α-Fe precipitates. The sintering temperature is particularly preferably in the range of 900 to 1300°C. The sintering time is preferably 0.5 to 20 hours, more preferably 1 to 10 hours. The sintering can be in the mode of holding at a certain temperature after temperature elevation, or a two-stage sintering mode in which the temperature is elevated to a first sintering temperature and then held at a lower second sintering temperature for a prescribed time can be employed in order to seek the refinement of the crystal grains. In addition, multiple sintering can be performed, or a discharge plasma sintering method or the like can be applied. The cooling rate after sintering is not particularly limited, and cooling to at least 600°C or lower, preferably 200°C or lower, at a cooling rate of 1°C / minute or higher and 100°C / minute or lower, more preferably 5°C / minute or higher and 50°C / minute or lower, can be preferred. In order to increase the coercive force, aging heat treatment at 300 to 900°C for 0.5 to 50 hours can be further performed. By optimizing the conditions of sintering and aging depending on the composition or the powder particle diameter or the like, H cJ is increased. The sintered body is then cut / milled into a prescribed shape, and magnetized to form a sintered magnet.

[0069] On the other hand, as a method of manufacturing an anisotropic rare-earth sintered magnet in which the Sm / R ratio in the main phase grains present inside the main phase grains is lower than the Sm / R ratio of the R-rich phase and the R(Fe, Co)2 phase, for example, the following can be cited: a two-alloy method or a grain boundary diffusion method, etc.

[0070] In the case of employing the two-alloy method, two kinds of raw alloy having different compositions are prepared using metal raw materials, alloys, ferroalloys, etc. of R, Fe, Co, M. Note that three or more kinds of alloys can be used. At this time, it is preferable to use an alloy A in which the ThMn 12 An alloy A in which the ThMn

[0071] In the sintered magnet obtained by the two-alloy method, the main phase composed of the ThMn 12 compound is formed mainly from the components of the alloy A, and the R-rich phase, the R(Fe, Co)2 phase, or the shell portion of the main phase grains is formed mainly from the components of the alloy B. Therefore, the Sm / R atomic ratio of the R-rich phase or the R(Fe, Co)2 phase formed in the grain boundary portion is higher than the Sm / R atomic ratio inside the main phase grains. In addition, a part of the Sm of the grain boundary phase substitutes for the R atom in the surface layer portion of the main phase grains, and a core-shell structure in which the Sm concentration is different between the surface layer portion and the inside of the grains is formed to increase the coercive force.

[0072] On the other hand, in the grain boundary diffusion method, a sintered body is first produced by the single alloy method or the binary alloy method, as described above. At this time, R of the sintered body composition can include Sm or can not include Sm.

[0073] Next, the sintered body obtained is subjected to grain boundary diffusion of Sm. The sintered body is cut and ground as necessary, and then a diffusion material selected from among compounds including a metal, an alloy, an oxide, a fluoride, an oxyfluoride, a hydride, a carbide, and the like of Sm is disposed on the surface thereof in the form of a powder, a thin film, a thin strip, a foil, or the like. For example, a slurry can be prepared by mixing a powder of the above-described material with water or an organic solvent or the like, and the slurry can be applied to the sintered body and then dried. Alternatively, a thin film of the above-described material can be formed by evaporation, sputtering, CVD, or the like, and the thin film can be disposed on the surface of the sintered body. The amount of the diffusion material disposed is preferably 10 to 1000 μ g / mm 2 , and particularly preferably 20 to 500 μ g / mm 2 . If the amount is within this range, an increase in H cJ can be sufficiently obtained, and an increase in manufacturing cost due to an increase in the Sm content can be suppressed. In addition, the property of Sm that has a high vapor pressure can be used, and a Sm metal or a Sm alloy can be heat-treated in the same chamber as the sintered body, so as to be brought into contact with the sintered body in the form of Sm vapor.

[0074] The sintered body is heat-treated in a vacuum or an inert gas atmosphere, with Sm disposed on the surface thereof. The heat treatment temperature is preferably 600°C or higher and lower than the sintering temperature, and particularly preferably 700°C or higher and 1100°C or lower. The heat treatment time is preferably 0.5 to 50 hours, and particularly preferably 1 to 20 hours. The cooling rate after the heat treatment is not particularly limited, and is preferably 1 to 20°C / minute, and particularly 2 to 10°C / minute. In order to increase the coercive force, an aging heat treatment can further be performed at 300 to 900°C for 0.5 to 50 hours.

[0075] The Sm disposed on the sintered body penetrates into the sintered body while increasing the Sm concentration of the R-rich phase or the R(Fe, Co)2 phase by the heat treatment, and the Sm / R ratio of these grain boundary phases increases. By increasing the Sm concentration of the grain boundary phase, substitution of Sm for R atoms also occurs in the surface layer portion of the main phase crystal grains that are in contact with the grain boundary phase, and the Sm / R ratio of the surface layer portion of the main phase crystal grains is higher than the Sm / R ratio of the inside of the main phase crystal grains, and H cJ increases.

[0076] The anisotropic rare earth sintered magnet of the present application produced by this operation exhibits a residual magnetic flux density B r of 5 kG or more and a coercive force H cJ of at least 5 kOe or more at room temperature. The room temperature H cJFurther preferable if 8 kOe or more. In addition, the temperature coefficient β of the coercive force shows a characteristic of -0.5% / K or more. Here, β = ΔH cJ / ΔT x 100 / H cJ (20°C) (ΔH cJ = H cJ (20°C) - H cJ (140°C), ΔT = 20-140 (°C)). Compared with the Nd-Fe-B sintered magnet, the temperature change of the coercive force of the anisotropic rare earth sintered magnet of the present application is small, and is suitable for use at high temperature. Example

[0077] Hereinafter, examples and comparative examples are given to specifically explain the present application, but the present application is not limited to the following examples.

[0078] [Example 1]

[0079] Sm metal, electrolytic iron, Co metal, and V metal were used to adjust the composition, and after melting in an Ar gas environment using a high-frequency induction furnace, thin strip continuous casting was performed on a water-cooled Cu roll, thereby manufacturing alloy thin strips having a thickness of about 0.2 to 0.4 mm. The cross section of the alloy was polished, and after etching treatment, observation of the structure was performed using a laser microscope (manufactured by Olympus Corporation, LEXT OLS4000). The observed site was a position of about 0.15 mm from the surface of the thin strip contacting the cooling roll, and 20 sites were observed. For each image, 20 lines parallel to the surface contacting the roll were drawn at equal intervals, the intersections of these lines with the grain boundary phase removed by etching were counted, and the average grain boundary phase interval was calculated, and the result was 3.6 μ m. After hydrogen storage treatment of the alloy at normal temperature, dehydrogenation treatment was performed in a vacuum at 400°C to manufacture coarse powder, and pulverization was performed in a jet mill in a nitrogen stream, thereby manufacturing fine powder having an average particle diameter of 2.4 μ m. Next, the fine powder was filled into a mold of a molding device in an inert gas environment, and pressure molding was performed while orienting in a magnetic field of 15 kOe (= 1.19 MA / m) and applying a pressure of 0.6 Ton / cm 2 in a direction perpendicular to the magnetic field. After sintering the obtained pressure-molded body in an Ar gas environment at 1130°C for 3 hours, and temporarily taking out after cooling to room temperature at a cooling rate of 13°C / minute, heat treatment at 480°C for 1 hour was performed in an Ar gas environment as aging treatment, thereby obtaining a sintered body sample.

[0080] The results of analysis by high-frequency induction coupled plasma emission spectroscopy (manufactured by Hitachi High-Tech Science, Inc., SPS3520UV-DD) by high-frequency induction coupled plasma emission spectroscopy (ICP-OES) for the obtained sintered body sample were Sm 10.9 Fe bal. Co 5.4 V 14.2 The X-ray diffraction measurement of the powder obtained by crushing a part of the sample confirmed that the crystal structure of the main phase was ThMn 12 type. In addition, the observation of the microstructure and the composition analysis of each phase of the sintered body using an EPMA device (manufactured by JEOL Ltd., JXA-8500F) confirmed that there were 1 vol% or more of the R-rich phase and the R(Fe, Co)2phase in the grain boundary portion. The volume ratio of each phase was calculated as a ratio equivalent to the area ratio in the image of the backscattered electron image. The R2(Fe, Co, M) 17 phase, the R3(Fe, Co, M) 29 phase, or the α-Fe phase were not observed. Note that the total of the phase ratio was less than 100% because there were also phases such as oxides. From the analysis value of the R(Fe, Co)2phase, an alloy having the same composition was produced by arc melting, and after homogenization treatment at 830°C for 10 hours, when magnetization-temperature measurement was performed by VSM, the Curie temperature T c was 366°C.

[0081] In addition, the sintered body sample was etched, and the average crystal grain diameter of the main phase calculated from the observation result was 8.2 μ m. When the magnetic properties were measured again using a B-H tracer, the room temperature coercive force H cJ showed 10.3 kOe. In addition, the temperature coefficient β of H cJ was -0.44% / K. The results are shown in Tables 1 to 3.

[0082] [Comparative Example 1]

[0083] An alloy thin strip was produced using Sm metal, electrolytic iron, Co metal, and Ti metal to adjust the composition, melting in an Ar gas environment using a high-frequency induction furnace, and performing thin strip continuous casting on a water-cooled Cu roll. The average crystal grain diameter of the alloy in the short axis direction calculated from the image observed by a laser microscope was 4.7 μ m. The sample was crushed, formed in a magnetic field, and sintered at 1170°C for 3 hours in an Ar gas environment, and after cooling to room temperature at a cooling rate of 13°C / minute, heat treatment at 480°C for 1 hour was performed in an Ar gas environment to obtain the sintered body sample of Comparative Example 1. The composition value of the sintered body sample obtained by ICP analysis was Sm 10.7Fe bal. Co 5.2 Ti 8.0 . In addition, it was confirmed that the main phase of the sintered body sample was ThMn 12 type crystal by X-ray diffraction measurement. When the formed phase was investigated by EPMA, although R(Fe, Co)2phase existed, no R-rich phase was formed, and fine (Fe, Co)2Ti phase was precipitated. Moreover, the average crystal grain diameter of the main phase calculated in the same manner as in Example 1 was 8.8 μ m. The sintered body sample showed only a low coercive force of 0.1 kOe at room temperature. The results are shown in Tables 1 to 3.

[0084] [Example 2]

[0085] A cast alloy was produced by using Sm metal, electrolytic iron, ferrovanadium, Al metal, Si to adjust the composition, and melting in an Ar gas environment using a high-frequency induction furnace. In order to make the primary crystal α-Fe disappear, the alloy was subjected to heat treatment at 900°C for 50 hours. The obtained alloy was observed for the structure using a laser microscope, and it was confirmed from the observed image that the average crystal grain diameter of the main phase was 5 μ m or more. The alloy was subjected to hydrogen storage treatment and dehydrogenation treatment by heating in vacuum at 400°C to produce coarse powder, and then pulverized in a jet mill in a nitrogen stream to produce fine powder having an average particle diameter of 1.8 μ m. The fine powder was filled into a mold of a molding device in an inert gas environment, and molded in a magnetic field. The press powder molded body was sintered in an Ar gas environment at 1140°C for 3 hours, and then cooled to room temperature at a cooling rate of 13°C / minute to obtain a sintered body sample.

[0086] The composition of the sintered body analyzed by ICP method was Sm 9.6 Fe bal. V 14.4 Al 0.4 Si 0.2 . In addition, it was confirmed by X-ray diffraction that ThMn 12 type crystal was the main phase. R-rich phase and R(Fe, Co)2phase of 1% by volume or more existed in the grain boundary portion of the sintered body structure. The room temperature H cJ measured by B-H tracer was 8.3 kOe, and the temperature coefficient β of H cJ was -0.46% / K. Moreover, the average crystal grain diameter of the main phase calculated in the same manner as in Example 1 was 9.5 μ m. From the analysis value of R(Fe, Co)2phase, an alloy having the same composition was produced by arc melting, and when the magnetization-temperature measurement was performed by VSM after homogenization treatment at 850°C for 20 hours, the Curie temperature T c was 349°C. The results are shown in Tables 1 to 3.

[0087] [Examples 3 to 9]

[0088] The composition was adjusted in the same manner as in Example 2, and a cast alloy was produced by high frequency melting. In order to eliminate primary α-Fe, the alloy was subjected to heat treatment at 850 to 1100°C for 10 to 50 hours. The resulting alloy was observed for the structure by a laser microscope, and it was confirmed from the observed image that the average crystal grain size of the main phase was 1 μ m or more. The hydrogen storage treatment and the dehydrogenation treatment by heating at 400°C in vacuum were performed to produce coarse powder, and then pulverization was performed in a jet mill in a nitrogen stream to produce fine powder having an average particle size of 2 to 4 μ m. The fine powder was filled into a mold of a molding device in an inert gas atmosphere, and molding was performed in a magnetic field. After sintering of the press powder compact in an Ar gas atmosphere and cooling to room temperature, aging heat treatment was performed to obtain a sintered body sample. Table 1 shows the composition of each sample analyzed by ICP, the crystal structure of the main phase confirmed by X-ray diffraction, and the average crystal grain size of the main phase of the sintered body. Table 2 shows the sintering treatment conditions, the cooling rate after sintering, the aging treatment conditions, the temperature coefficient β of B r , H cJ , and H cJ measured at room temperature. In Examples 7 and 8, a two-stage sintering method was applied in which the temperature was raised to the first sintering temperature, immediately lowered to the second sintering temperature, and then held for a prescribed time. In addition, Table 3 shows the composition and phase ratio of each phase analyzed by EPMA. In the samples of Examples 3 to 8, R-rich phase and R(Fe, Co)2phase were formed in the grain boundary portion, and exhibited a coercive force of 5 kOe or more at room temperature, and a temperature coefficient β of -0.5% / K or more.

[0089] [Comparative Examples 2 to 6]

[0090] The sintered body samples of Comparative Examples 2 to 5 were produced in the same manner as in Example 2 except that the composition shown in Table 1 was adjusted. The results are shown in Tables 1, 2, and 4. In Comparative Example 2, the total of R was less than 7 at%, and sintering was not sufficient, and a large amount of α-Fe phase was formed in the sintered body. In Comparative Example 3, the total of R exceeded 15 at%, and the volume ratio of the main phase was less than 80%. In Comparative Example 4, the total of M elements exceeded 20 at%, and RFeSi phase of PbClF type crystal was formed without observing R-rich phase. In Comparative Example 5, although RCu2phase of KHg2 type crystal was present at the grain boundary triple point, the total of M elements exceeded 20 at%, and R-rich phase was not observed. In Comparative Example 6, the total of M was less than 4 at%, and ThMn 12 type crystal was not observed in the structure, and a main phase of Th2Zn 17 type crystal was formed.

[0091] [Comparative Example 7]

[0092] A raw alloy of a rapidly-cooled thin strip was produced by adjusting the composition using Sm metal, electrolytic iron, Ti metal, and V metal, and cooling a molten raw metal on a Cu roll rotating at a peripheral speed (linear speed) of 20 m / sec. The thickness of the thin strip was 10 to 50 μ m, and the obtained alloy was observed for the structure using a laser microscope. From the observed image, it was confirmed that the average crystal grain size was too fine to be measured, but was at least less than 1 μ m. After the alloy thin strip was pulverized using a ball mill, the powder of 300 μ m or less was selected using a sieve, and hot-pressing was performed at 750°C in an Ar atmosphere. The average crystal grain size of the main phase crystal grains was as fine as 0.2 to 0.3 μ m or so, and the composition of the main phase and the grain boundary phase could not be identified by EPMA. In addition, since the easy magnetization axes of the main phase were not aligned, only a low B r was obtained. The results are shown in Tables 1, 2, and 4.

[0093] [Example 10]

[0094] A rapidly-cooled thin strip alloy having a composition of 8 at% of Ce, 1.2 at% of Co, 12 at% of V, 2.6 at% of Si, 0.8 at% of Ti, and the balance of Fe was produced by adjusting the composition using Ce metal, electrolytic iron, Co metal, V metal, pure Si, and sponge Ti, melting in an Ar atmosphere using a high-frequency induction furnace, and performing thin strip continuous casting on a water-cooled Cu roll. The average crystal grain size of the alloy in the short axis direction, which was calculated from an image observed using a laser microscope, was 4.5 μ m. After the alloy was subjected to hydrogen storage treatment at ordinary temperature, dehydrogenation treatment was performed by heating at 400°C in a vacuum to produce a coarse powder (which was used as the Example 10A powder). On the other hand, an alloy ingot having a composition of 35 at% of Sm and the balance of Fe was produced using Sm metal and electrolytic iron as raw materials using a high-frequency induction furnace, and a coarse powder was produced by mechanical pulverization (as the Example 10B powder). After the Example 10A powder and the Example 10B powder were mixed at a weight ratio of 92:8, pulverization was performed in a jet mill in a nitrogen stream to produce a fine powder having an average particle diameter of 2.4 μ m.

[0095] Using the mixed powder, molding in a magnetic field was performed in the same manner as in Example 1, and after sintering at 980°C for 3 hours in an Ar atmosphere, cooling to room temperature at a cooling rate of 10°C / min, and heat treatment at 480°C for 1 hour in an Ar atmosphere, a sintered body of Example 10 was obtained. The composition value of the sintered body sample was Sm 2.8 Ce 7.5 Febal. Co 1.5 V 11.1 Si 2.4 Ti 0.8 Furthermore, X-ray diffraction analysis confirmed that the main phase of the sintered body is ThMn. 12 Type 1 crystal. The composition of the main phase, as confirmed by EPMA determination, is as follows: Ce in the central part of the grain. 7.8 Fe bal. Co 1.4 V 11.7 Si 2.3 Ti 0.9 Furthermore, it does not contain Sm, and the outer shell of the grain is Sm. 5.1 Ce 2.7 Fe bal. Co 1.5 V 11.6 Si 2.5 Ti 0.8 The Sm / R ratio inside the grains is lower than that on the surface. Furthermore, it was confirmed that the compositional analysis values ​​of the R-rich phase and the R(Fe,Co)2 phase are Sm... 27.7 Ce 52.4 Fe bal. Co 1.1 V 0.1 、Sm 12.6 Ce 20.4 Fe bal. Co 0. 6V 0.8 Si 0.1 The Sm / R ratio within the grains is lower than that of the R-rich phase and the R(Fe, Co)₂ phase. The average grain size of the main phase is 8.6 mm. μ The coercivity of the sintered body at room temperature is 10.3 kOe, and the temperature coefficient of coercivity β is -0.44% / K. The Curie temperature T of an alloy with the same composition prepared based on the analytical values ​​of the R(Fe,Co)2 phase is... c It is 118℃.

[0096] [Example 11]

[0097] The composition was adjusted using Nd, electrolytic iron, Co, V, Al, and W metals. After melting in an Ar atmosphere using a high-frequency induction furnace, thin strips with a thickness of approximately 0.2–0.4 mm were continuously cast on water-cooled Cu rolls. The average grain boundary phase spacing of this alloy was calculated to be 2.9. μ After hydrogen storage treatment of the alloy at room temperature, a dehydrogenation treatment was performed in a vacuum at 400°C to produce coarse powder, which was then pulverized in a jet mill under a nitrogen flow to produce particles with an average particle size of 1.9 μm. μm. Next, the micropowder was subjected to press molding while being oriented in a magnetic field, and after sintering in a vacuum at 1170°C for 3 hours, the sintered body was taken out after cooling to room temperature at a cooling rate of 12°C / min. The sintered body of Example 1 was obtained.

[0098] Next, a rapidly-cooled thin ribbon alloy having a composition of 75 at% of Sm, 15 at% of Al, and the balance of Co was produced by feeding Sm metal, Co metal, and Al metal into a quartz tube having a nozzle hole of 0.5 mm, and after high-frequency melting in an Ar atmosphere, the alloy was blown onto a Cu roll rotating at a peripheral speed of 25 m / sec. The rapidly-cooled thin ribbon was pulverized by a ball mill for 30 minutes, and a powder having a mass median particle diameter of 10.3 μ m was obtained. The powder was mixed / stirred with ethanol at a weight ratio of 1:3, and the sintered body was dipped in the resulting liquid and pulled up, after which the sintered body surface was powder coated by hot air drying. The sintered bodies of Example 11 were obtained by performing a diffusion heat treatment at 880°C for 10 hours in a vacuum, and an aging heat treatment at 500°C for 2 hours in an Ar atmosphere.

[0099] The results of ICP analysis of the sintered body sample of Example 11 were as follows: Sm 1.4 Nd 9.6 Fe bal. Co 9.7 V 13.0 Al 0.6 W 0.6 The X-ray diffraction measurement of the powder obtained by pulverizing a part of the sample confirmed that the crystal structure of the main phase was ThMn 12 type. In addition, the microstructure observation and the composition analysis of each phase of the sintered body by EPMA confirmed that there were 1 vol% or more of R-rich phase and R(Fe, Co)2phase at the grain boundary portion. No R2(Fe, Co, M) 17 phase, R3(Fe, Co, M) 29 phase, or α-Fe phase was observed. Note that since there were also phases such as oxides, the total of the phases was less than 100%.

[0100] The EPMA-based composition analysis values of the central portion and the outer shell portion of the main phase grain were confirmed to be Nd 7.7 Fe bal. Co 9.8 V 13.8 Al 0.6 W 0.6 , Sm 3.7 Nd 4.0 Fe bal. Co 9.9 V 13.7 Al 0.6 W0.4 The Sm / R ratio in the grain interior is lower than the Sm / R ratio in the shell portion. In addition, the composition analysis values of the R-rich phase and the R(Fe, Co)2phase are Sm 26.7 Nd 52.1 Fe bal. Co 17.4 V 0.4 Al0 .7 , Sm 12.3 Nd 22.3 Fe bal. Co 4.1 V 0.1 Al 0.3 In the interior of the main phase grain, Sm was not detected, and in contrast, the R-rich phase and the R(Fe, Co)2phase present in the grain boundary portion contained Sm, and the Sm / R ratio was increased.

[0101] From the analysis values of the R(Fe, Co)2phase, an alloy of the same composition was produced by arc melting, and after a homogenization treatment at 800°C for 20 hours, when magnetization-temperature measurement was performed by VSM, the Curie temperature T c was 275°C. In addition, after etching the sintered body of Example 18, observation was performed, and from the results obtained, the average crystal grain diameter of the main phase was 9.0 μ m. Furthermore, when the magnetic properties were measured using a B-H tracer, the room temperature coercive force H cJ showed 8.8 kOe. In addition, the temperature coefficient β of H cJ was -0.45% / K.

[0102] [Comparative Example 8]

[0103] The sintered body of Comparative Example 9 was produced in the same manner as the production method of the sintered body of Example 11, except that the sintered body was not powder coated and subjected to a diffusion heat treatment, but was subjected to an aging heat treatment at 500°C for 2 hours in an Ar gas environment.

[0104] The sintered body composition of Comparative Example 8 was Nd 9.5 Fe bal. Co 10.1 V 12.3 Al 0.4 W 0.5 The composition analysis values of the central portion of the main phase grain and the R(Fe, Co)2phase were Nd 7.9 Fe bal. Co 10.4 V 12.8 Al 0.4 W 0.5 , Nd 32.3 Fe bal. Co 4.5 V0.2 Al 0.1 No R-rich phase was detected. The room temperature coercivity H cJ was 0.1 kOe. The results are shown in Tables 5-7.

[0105] [Table 1]

[0106]

[0107] [Table 2]

[0108]

[0109] [Table 3]

[0110]

[0111] [Table 4]

[0112]

[0113] [Table 5]

[0114]

[0115] [Table 6]

[0116]

[0117] [Table 7]

[0118]

Claims

1. An anisotropic rare earth sintered magnet characterized by: which is composed of a compound represented by the formula (R 1-a Zr a ) x (Fe 1-b Co b ) 100-x-y (M 1 1-c M 2 c ) y an anisotropic rare earth sintered magnet represented by the formula (R 1 M is one or more elements selected from the group consisting of V, Cr, Mn, Ni, Cu, Zn, Ga, Al, and Si, M 2 is one or more elements selected from the group consisting of Ti, Nb, Mo, Hf, Ta, and W, and x, y, a, b, and c are respectively as follows: 7 ≤ x ≤ 15 atom%, 4 ≤ y ≤ 20 atom%, 0 ≤ a ≤ 0.2, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.9, wherein a main phase composed of a compound of a ThMn 12 type crystal containing 80% or more by volume, an average crystal grain size of the main phase is 1 μm or more, and a R-rich phase and an R(Fe, Co)2 phase are contained in the grain boundary portion. The Sm / R ratio in the grain interior of the main phase is lower than the Sm / R ratio of the R-rich phase and the R(Fe, Co)2 phase.

2. The anisotropic rare earth sintered magnet as claimed in claim 1, characterized by: The R-rich phase and the R(Fe, Co)2 phase are contained in a total amount of 1% by volume or more.

3. The anisotropic rare earth sintered magnet as claimed in claim 1 or 2, characterized by: The R-rich phase contains 40% by atom or more of R.

4. The anisotropic rare earth sintered magnet according to any one of claims 1 to 3, characterized by: The R(Fe, Co)2 phase is a phase that exhibits ferromagnetism or ferrimagnetism at a temperature of room temperature or higher.

5. The anisotropic rare earth sintered magnet according to any one of claims 1 to 4, characterized by: The Sm / R ratio in the grain interior of the main phase is lower than the Sm / R ratio of the shell portion of the grain of the main phase.

6. The anisotropic rare earth sintered magnet according to any one of claims 1 to 5, characterized by: The interior of the grain of the main phase does not contain Sm.

7. The anisotropic rare earth sintered magnet according to any one of claims 1 to 6, characterized by: The coercive force at room temperature is 5 kOe or more, and the temperature coefficient β of the coercive force is -0.5% / K or more.

8. The method of producing an anisotropic rare earth sintered magnet as claimed in any one of claims 1 to 7, characterized by: An alloy containing a compound phase of ThMn 12 The alloy powder was pulverized, and the powder was formed into a compact in a state where a magnetic field was applied, and then sintered at a temperature of 800°C or higher and 1400°C or lower.

9. The method of producing an anisotropic rare earth sintered magnet as claimed in claim 8, characterized by: An alloy containing a compound phase of ThMn 12 with a higher R composition ratio and Sm / R ratio than the alloy is pulverized, mixed, and subjected to powder compression molding in a state where a magnetic field is applied to produce a molded body.

10. The method of producing an anisotropic rare earth sintered magnet as claimed in claim 8 or 9, characterized by: The Sm-containing material is brought into contact with a sintered body in which a compound of a SmMn 12 The Sm-containing material is brought into contact with a sintered body in which a compound of a SmMn 12 The Sm-containing material is brought into contact with a sintered body in which a compound of a SmMn 12 The Sm-containing material is brought into contact with a sintered body in which a compound of a SmMn 12 The Sm-containing material is brought 11. The method of producing an anisotropic rare earth sintered magnet as claimed in claim 10, characterized by: The Sm-containing material in contact with the sintered body is one or more selected from the group consisting of Sm metal, a Sm-containing alloy, a Sm-containing compound, and a Sm-containing vapor, and the form thereof is one or more selected from the group consisting of a powder, a thin film, a thin ribbon, a foil, and a gas.

12. The method of producing an anisotropic rare earth sintered magnet according to any one of claims 8 to 11, characterized by: The sintered body is subjected to heat treatment at a temperature of 300 to 900°C.

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