R-fe-b sintered magnet

Abstract

For an R-Fe-B sintered magnet, in order to have both high residual magnetic flux density and high coercive force, which are characteristics of a paradox, an R-Fe-B sintered magnet is provided, characterized by having a composition containing R (R is one or more elements selected from rare earth elements, with Nd being essential), B, Zr, C, and the balance being Fe, O, other arbitrary elements, and unavoidable impurities, and when the atomic percentages of the above B, C, Zr, and O are respectively set as [B], [C], [Zr], and [O], the following relation (1) is satisfied: 0.86×([B]+[C]-2×[Zr])-4.9< [O]<0.86×([B]+[C]-2×[Zr])-4.6…(1).

Description

[0001] This invention is a divisional application of the invention application with application number 202080079656.0 (international application number PCT / JP2020 / 041339), application date November 5, 2020, and invention title "R-Fe-B sintered magnet". Technical Field

[0002] This invention relates to R-Fe-B rare earth sintered magnets that improve residual magnetic flux density while suppressing the decrease in coercivity. Background Technology

[0003] R-Fe-B sintered magnets (hereinafter sometimes referred to as Nd magnets) are essential functional materials for energy saving and high functionality, and their application range and production volume are expanding year by year. For example, they are used in drive motors in hybrid and electric vehicles, electric power steering motors, air conditioning compressor motors, and voice coil motors (VCMs) in hard disk drives. In these various applications, the high remanent magnetic flux density (hereinafter referred to as Br) of R-Fe-B sintered magnets is a major advantage, but further improvements in Br are required, for example, to further miniaturize motors.

[0004] As a method for increasing the Br content in R-Fe-B sintered magnets, it is previously known to increase the R2Fe content in the sintered magnet. 14 Methods to reduce the content of R by decreasing the proportion of B phase, and to reduce the solid solution in R2Fe 14 The method of adding elements to reduce the amount of Br in the B phase.

[0005] However, it is known that reducing the amount of R and other added elements can affect the coercivity (hereinafter referred to as H) related to the heat resistance of sintered magnets. cJ The amount of H is reduced. Especially with a decrease in the amount of R, there is a risk of reduced sinterability and abnormal grain growth in the sintering process of R-Fe-B sintered magnets, which undergo densification accompanied by the formation of a liquid phase. Therefore, to obtain R-Fe-B sintered magnets with higher properties, it is necessary to suppress the decrease in H caused by reducing the amount of R and other added elements. cJ To reduce H and simultaneously achieve high Br. In order to suppress or increase H cJ The reduction of Br is generally attributed to the addition of heavy rare earth elements such as Dy and Tb. Due to their addition, Br is reduced, and they are also scarce and expensive. Therefore, methods related to the reduction of the use of heavy rare earth elements such as Dy and Tb have been proposed to date.

[0006] For example, International Publication No. 2013 / 191276 (Patent Document 1) discloses a sintered magnet as follows: by reducing the content of B compared to the stoichiometric composition, adding 0.1 to 1.0% by mass of Ga, and adjusting the values ​​of [B] / ([Nd]+[Pr]) and ([Ga]+[C]) / [B] in a manner that satisfies a specific relationship for the content ratios of B, Nd, Pr, C, and Ga, high H can be obtained even with a composition that reduces the amount of heavy rare earth elements such as Dy and Tb. cJ .

[0007] Furthermore, International Publication No. 2004 / 081954 (Patent Document 2) proposes a method to suppress R by setting the content of B to approximately the stoichiometric composition. 1.1 The formation of the Fe4B4 phase yields a sintered magnet with high Br content. Furthermore, it is described that by using Ga containing 0.01–0.08% by mass, and with B below the stoichiometric composition, the formation of H-induced magnets can be suppressed. cJ Reduced R2Fe 17 The precipitation of the phase allows for the combination of high Br and high H content. cJ .

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: International Publication No. 2013 / 191276

[0011] Patent Document 2: International Publication No. 2004 / 081954 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] However, in the magnet described in the aforementioned patent document 1, by adding more than 0.1% by mass of Ga, the amount of heavy rare earth elements such as Dy and Tb is relatively reduced, thereby achieving R2Fe 14 The increase in saturation magnetization of the B phase, on the other hand, through the addition of Ga, R2Fe 14 The saturation magnetization of the B phase is reduced, so a sufficient increase in Br may not be achieved.

[0014] Furthermore, while the technology described in Patent Document 2 does indeed achieve good magnetic properties in R-Fe-B sintered magnets with an oxygen concentration of approximately 0.4% by mass, the description of the relationship between oxygen concentration and magnetic properties in the sintered magnet is insufficient. If the oxygen concentration is below 0.4% by mass, especially below 0.2% by mass, the characteristic behavior changes significantly, and it may not be possible to achieve high Br and high H content. cJ It has both.

[0015] The present invention was made in view of the above-mentioned problems, and its object is to provide an R-Fe-B based sintered magnet that, by adjusting and optimizing the content ratio of constituent elements in the R-Fe-B based sintered magnet, exhibits high Br and stable H content. cJ .

[0016] Methods for solving problems

[0017] To achieve the above objectives, the inventors conducted an in-depth study on the composition of R-Fe-B sintered magnets containing B, C, O, and X (one or more of Ti, Zr, Hf, Nb, V, and Ta), including C and O, which are generally considered impurities. The results showed that by adjusting the content of B, C, O, and X within a specified range, high Br and stable H within that range can be obtained. cJ This invention has been completed.

[0018] Therefore, the present invention provides the following R-Fe-B based sintered magnet.

[0019] [1] R-Fe-B sintered magnets are characterized by having the following composition: containing 12.5 to 14.5 atomic% of R (R is one or more elements selected from rare earth elements, with Nd being essential), 5.0 to 6.5 atomic% of B, 0.02 to 0.5 atomic% of X (X is one or more elements selected from Ti, Zr, Hf, Nb, V, Ta), 0.1 to 1.6 atomic% of C, and the balance being Fe, O, other arbitrary elements and unavoidable impurities, and when the atomic percentages of B, C, X and O are set as [B], [C], [X] and [O] respectively, the following relationship (1) is satisfied.

[0020] 0.86×([B]+[C]-2×[X])-4.9<[O]<0.86×([B]+[C]-2×[X])-4.6…(1).

[0021] [2][1] R-Fe-B sintered magnets, wherein the content of O is 0.1 to 0.8 atoms.

[0022] [3][1] or [2] R-Fe-B sintered magnets, wherein, as any of the elements, they contain 0.1 to 3.5 atomic% Co, 0.05 to 0.5 atomic% Cu, and more than 0 atomic% and less than 1.0 atomic% Al.

[0023] The R-Fe-B sintered magnet of any one of [4][1] to [3], wherein, as X, it contains Zr.

[0024] The R-Fe-B sintered magnet of any one of [5][1] to [4], wherein, as any one of the elements, it contains more than 0 and less than 0.1 atomic% Ga.

[0025] Invention Effects

[0026] According to the R-Fe-B sintered magnet of the present invention, by adjusting and optimizing the content ratio of B, C, O, X (Ti, Zr, Hf, Nb, V, Ta, one or more of these elements) in the constituent elements of the magnet composition, it is possible to possess both the high Br and high H content that were previously known as bivariate characteristics. cJ . Attached Figure Description

[0027] Figure 1 This is a coordinate graph showing the relationship between [B]+[C]-2×[X] and [O] in the magnets of Examples 1-5 and Comparative Examples 1-6. Detailed Implementation

[0028] As described above, the R-Fe-B sintered magnet of the present invention has the following composition: containing 12.5 to 14.5 atomic% of R (R is one or more elements selected from rare earth elements, with Nd being essential), 5.0 to 6.5 atomic% of B, 0.02 to 0.5 atomic% of X (X is one or more elements selected from Ti, Zr, Hf, Nb, V, Ta), 0.1 to 1.6 atomic% of C, with the balance being Fe, O, other arbitrary elements, and unavoidable impurities.

[0029] As described above, the element R constituting the sintered magnet of the present invention is one or more elements selected from rare earth elements, with Nd being an essential element. Among the rare earth elements other than Nd, Pr, La, Ce, Gd, Dy, Tb, and Ho are preferred, with Pr, Dy, and Tb being particularly preferred, and Pr being especially preferred. The proportion of Nd, an essential component in R, is preferably 60 atomic% or more, and particularly preferably 70 atomic% or more.

[0030] As described above, the content of R is 12.5–14.5 atomic%, preferably 12.8–14.0 atomic%. If the content of R is less than 12.5 atomic%, α-Fe crystallizes and precipitates in the raw material alloy, and even homogenization is difficult to eliminate this α-Fe. The H of the R-Fe-B sintered magnet... cJ The squareness is significantly reduced. Furthermore, even when the raw material alloy is produced using a strip casting method where α-Fe crystallization is difficult, α-Fe crystallization still occurs. Therefore, the H... cJThe squareness is significantly reduced. Furthermore, the amount of liquid phase, mainly composed of R, which promotes densification during sintering, decreases, thus reducing sinterability and resulting in insufficient densification of R-Fe-B sintered magnets. On the other hand, while there are no problems in manufacturing when the R content exceeds 14.5 atomic%, the R2Fe content in the sintered magnet... 14 As the proportion of phase B decreases, the proportion of phase Br also decreases.

[0031] As described above, the sintered magnet of the present invention contains 5.0 to 6.5 atomic% boron (B). A more preferred content is 5.1 to 6.1 atomic%, and even more preferred is 5.2 to 5.9 atomic%. In the present invention, the content of B is consistent with the content of C and X described later, and becomes the determining factor for obtaining stable H. cJ The main reason for the required oxygen concentration range is that if the B content is less than 5.0 atomic%, then the formed R2Fe... 14 The proportion of B phase decreases, Br decreases significantly, and R2Fe is formed. 17 Phase, therefore H cJ The content of B decreases. On the other hand, if the content of B exceeds 6.5 atomic%, a B-rich phase is formed, and the R2Fe in the magnet... 14 The ratio of B phase decreases, resulting in a decrease in Br.

[0032] As described above, the element X constituting the sintered magnet of the present invention is one or more elements selected from Ti, Zr, Hf, Nb, V, and Ta. By containing these elements, abnormal grain growth during sintering can be suppressed through the formed XB phase. It should be noted that, although not particularly limited, Zr is preferably included as at least one of the aforementioned elements X.

[0033] As described above, the content of X is 0.02 to 0.5 atomic%, preferably 0.05 to 0.3 atomic%, and more preferably 0.07 to 0.2 atomic%. If the content of X is less than 0.02 atomic%, the effect of suppressing abnormal grain growth during sintering cannot be obtained. On the other hand, when the content of X exceeds 0.5 atomic%, R2Fe is formed by forming the XB phase. 14 Phase B, therefore the amount of B decreases, possibly due to R2Fe. 14 The decrease in the B ratio leads to a decrease in Br, which in turn forms R2Fe. 17 This led to a significant increase in H. cJ reduce.

[0034] Furthermore, the carbon (C) content in the sintered magnet of the present invention is, as described above, 0.1 to 1.6 atomic%, preferably 0.2 to 1.0 atomic%. The C comes from raw materials and lubricants added during molding in a magnetic field to improve powder orientation, making it difficult to obtain R-Fe-B based sintered magnets with a C content of less than 0.1 atomic%. On the other hand, when the C content exceeds 1.6 atomic%, a large amount of RC phase exists in the sintered magnet, therefore H... cJ Significantly reduced.

[0035] The sintered magnet of the present invention contains the specified amounts of R, B, and C as described above, and as a balance, contains Fe, O, other arbitrary elements, and consequently unavoidable impurities. In this case, in the present invention, when the atomic percentages of B, C, X, and O are respectively set as [B], [C], [X], and [O], the content of O is within the range that satisfies the following relationship (1).

[0036] 0.86×([B]+[C]-2×[X])-4.9<[O]<0.86×([B]+[C]-2×[X])-4.6…(1)

[0037] That is, in the composition of the sintered magnet of the present invention, the content of O varies depending on the content of [B], [C], and [X] mentioned above. Considering that it is sometimes difficult to make the oxygen content less than 0.1 atomic% in the production of Nd magnets, the content of O is preferably in the range of 0.1 to 0.8 atomic%, more preferably in the range of 0.2 to 0.7 atomic%, and is in order to satisfy the content of the above-mentioned relationship (1). In the present invention, the content of O is an important factor. If the content of O is less than or equal to the left side of the above-mentioned relationship (1) [0.86 × ([B] + [C] - 2 × [X]) - 4.9] atomic%, then H cJ Decrease. Furthermore, when the O content is above [0.86 × ([B] + [C] - 2 × [X]) - 4.6] atoms on the right side of the above relationship (1), H... cJ It also decreased.

[0038] In addition, as described above, the sintered magnet of the present invention can contain any element other than R, B, X, C, Fe, and O, such as Co, Cu, Al, Ga, and N as the aforementioned arbitrary elements.

[0039] From the viewpoint of improving Curie temperature and corrosion resistance through the presence of Co, the Co content is preferably 0.1 atomic% or more, more preferably 0.5 atomic% or more. Furthermore, from the perspective of stably obtaining high H... cj From this perspective, the content of Co is preferably 3.5 atomic% or less, and more preferably 2.0 atomic% or less.

[0040] From the viewpoint of obtaining the optimal temperature range through appropriate low-temperature treatment after sintering to ensure good mass production, the Cu content is preferably 0.05 atomic% or more, more preferably 0.1 atomic% or more. Furthermore, from the perspective of obtaining good sinterability and high magnetic properties (Br, H... cJ From the perspective of [the relevant data], it is preferred to be 0.5 atomic% or less, and more preferably 0.3 atomic% or less.

[0041] From obtaining sufficient H cJ From the viewpoint of obtaining high Br, the content of Al is preferably more than 0 atomic%, more preferably 0.05 atomic% or more. Furthermore, from the viewpoint of obtaining high Br, it is preferably 1.0 atomic% or less, more preferably 0.5 atomic% or less. Furthermore, from the same viewpoint, the content of Ga is preferably more than 0 atomic% and less than 0.1 atomic%, more preferably 0.05 to 0.1 atomic%. Additionally, from the viewpoint of obtaining good H... cJ From this perspective, the content of N is preferably below 0.7 atomic%.

[0042] In addition, for the sintered magnet of the present invention, besides these elements, as unavoidable impurities, it is permissible to contain elements such as H, F, Mg, P, S, Cl, Ca, Mn, Ni, etc., with a total unavoidable impurity content of 0.1% by mass or less, relative to the total of the magnet constituent elements and the unavoidable impurities. However, the lower the content of these unavoidable impurities, the better.

[0043] As described above, the composition of the sintered magnet of the present invention is adjusted such that the content of O satisfies the above-mentioned relationship (1). That is, when the atomic percentages of B, C, X and O are set to [B], [C], [X] and [O] respectively, the following relationship (1) is satisfied.

[0044] 0.86×([B]+[C]-2×[X])-4.9<[O]<0.86×([B]+[C]-2×[X])-4.6…(1)

[0045] By satisfying this relationship, it is possible to have both high Br and stable H. cJ The reasoning may not be clear, but it can be inferred as follows: Given R₂Fe 14 A portion of the B in compound B can be replaced by C, but C typically forms a ROC phase as an impurity phase at the grain boundary triple point, contributing almost nothing to the formation of the main phase. On the other hand, when attempting to obtain high Br by reducing the R content, as in this invention, it is necessary to reduce the O content as an impurity in order to promote liquid-phase sintering. It is believed that under such low oxygen content conditions, the amount of ROC phase formation is reduced, while a portion of C can readily form R2Fe. 14C. Furthermore, X in the sintered magnet mainly forms XB2 compounds, which inhibit abnormal grain growth during the sintering process, and also reduces R2Fe caused by B and C. 14 The effect of the amount of B phase formation. That is, it actually contributes to the formation of R2Fe. 14 The amount of B and C atoms in the formation of the B phase can be represented by ([B] + [C] - 2 × [X]). Thus, the inventors believe that R2Fe... 14 The formation of the B phase is related to the content of B, C, X, and O atoms. By optimizing the relationship between ([B] + [C] - 2 × [X]) and [O], high Br and high H were achieved. cJ It possesses both properties. To explain, the content of O atoms, for example as in the examples described later, can be adjusted during the pulverization process of crushing the raw material alloy to obtain alloy micro-powder.

[0046] Next, the method for manufacturing the R-Fe-B sintered magnet of the present invention will be described.

[0047] The manufacturing process of the R-Fe-B sintered magnet of the present invention is basically the same as that of conventional powder metallurgy, without any particular limitations. It generally includes a melting process of melting raw materials to obtain a raw material alloy, a pulverizing process of pulverizing the raw material alloy with a specified composition to prepare alloy micro powder, a molding process of pressing the alloy micro powder into a molded body under the application of a magnetic field, and a heat treatment process of heat treating the molded body to obtain a sintered body.

[0048] First, in the aforementioned melting process, the metal or alloy of each element is weighed in a manner that constitutes the composition specified in the present invention. For example, the raw material is melted by high-frequency melting and then cooled to produce a raw material alloy. The casting of the raw material alloy generally employs melting casting methods such as pouring into flat molds, book molds, or continuous casting with strips. Furthermore, R2Fe, which is the main phase of the R-Fe-B alloy, is separately prepared. 14 The so-called two-alloy method, in which alloys with similar B compound compositions and R-rich alloys that act as liquid phase additives at sintering temperatures are weighed and mixed after coarse grinding, can also be applied to this invention. However, the composition of the alloy, which is close to that of the main phase, depends on the cooling rate during casting and the alloy composition. The α-Fe phase is prone to crystallization; therefore, in order to homogenize the microstructure and eliminate the α-Fe phase, it is preferable to perform a homogenization treatment at 700–1200°C for more than 1 hour in a vacuum or Ar atmosphere, as needed. It should be noted that when producing alloys with close compositions to the main phase using strip casting, homogenization can be omitted. For R-rich alloys that act as liquid phase additives, in addition to the casting method described above, the so-called liquid quenching method can also be used.

[0049] The aforementioned pulverization process can be a multi-stage process including coarse pulverization and fine pulverization. In the coarse pulverization stage, for example, a jaw crusher, Brown mill, pin mill, or hydrogen pulverizer is used. In the case of alloys produced by strip casting, hydrogen pulverization is typically applied to obtain coarse powder, for example, pulverized to 0.05–3 mm, particularly 0.05–1.5 mm. In the aforementioned fine pulverization stage, the coarse powder obtained in the coarse pulverization stage is finely pulverized to, for example, 0.2–30 μm, particularly 0.5–20 μm, using methods such as jet milling. It should be noted that in one or both of the coarse pulverization and fine pulverization stages of the raw material alloy, additives such as lubricants can be added as needed to adjust the carbon content to a specified range. Furthermore, the coarse pulverization and fine pulverization stages of the raw material alloy are preferably carried out in a gaseous atmosphere such as nitrogen or ar, and the oxygen content can be adjusted to a specified range by controlling the oxygen concentration in the gaseous atmosphere.

[0050] In the above forming process, a magnetic field of 400–1600 kA / m is applied to orient the alloy powder along its easily magnetized axis while simultaneously forming it using a compression molding machine. Preferably, the density of the formed body is 2.8–4.2 g / cm³. 3 From the viewpoint of ensuring the strength of the molded body while achieving good processability, the density of the molded body is preferably 2.8 g / cm³. 3 That's all. On the other hand, from the viewpoint of obtaining a suitable Br by simultaneously ensuring adequate strength of the molded body and good particle orientation under pressure, the density of the molded body is preferably 4.2 g / cm³. 3 The following applies. Furthermore, to suppress the oxidation of the alloy powder, it is preferable to perform the molding process under a gaseous atmosphere such as nitrogen or Ar.

[0051] In the above heat treatment process, the molded body obtained in the molding process is sintered in a high vacuum or a non-oxidizing atmosphere such as Ar. Generally, the sintering is preferably carried out by holding the body at a temperature range of 950°C to 1200°C for 0.5 to 5 hours. The cooling at the end of the sintering can be carried out by any of the following methods: gas quenching (cooling rate: 20°C / min or more), controlled cooling (cooling rate: 1 to 20°C / min), or furnace cooling. The resulting R-Fe-B sintered magnets have the same magnetic properties.

[0052] There are no particular limitations on the heat treatment used for sintering, in order to improve H cJHeat treatment can be performed at a temperature lower than the aforementioned sintering temperature. This post-sintering heat treatment can be a two-stage process involving high-temperature and low-temperature heat treatment, or it can be a low-temperature heat treatment alone. In the high-temperature heat treatment, the sintered body is preferably treated at a temperature of 600–950°C, and in the low-temperature heat treatment, it is preferably treated at a temperature of 400–600°C. Cooling can be performed using any of the following methods: gas quenching (cooling rate: 20°C / min or higher), controlled cooling (cooling rate: 1–20°C / min), or furnace cooling. Regardless of the cooling method, R-Fe-B sintered magnets with the same magnetic properties can be obtained.

[0053] In addition, the obtained R-Fe-B sintered magnets can be ground into a specified shape, and a coating or plating containing a substance selected from R can be applied to the magnet surface. 1 oxides, R 2 Fluorides, R 3 Fluoride oxides, R 4 hydroxide, R 5 carbonates, R 6 One or more of the basic carbonates (R) 1 ~R 6 A slurry of powders selected from one or more rare earth elements (which may be the same or different) is prepared, and then heat-treated while the powders are present on the surface of a sintered magnet. This treatment is a so-called grain boundary diffusion method. The grain boundary diffusion heat treatment temperature is preferably a temperature lower than the sintering temperature but above 350°C. There is no particular limitation on the time, but from the viewpoint of obtaining good microstructure and magnetic properties of the sintered magnet, it is preferably 5 minutes to 80 hours, more preferably 10 minutes to 50 hours. Through this grain boundary diffusion treatment, the R contained in the powder can be... 1 ~R 6 H is achieved by diffusion within the magnet. cJ The increase is explained below. For ease of explanation, the rare earth element introduced through this grain boundary diffusion is denoted as R as described above. 1 ~R 6 However, after diffusion at the grain boundaries, all of them are included in the aforementioned R component in the magnet of this invention.

[0054] Example

[0055] The following examples and comparative examples illustrate the present invention in more detail, but the present invention is not limited to the following examples.

[0056] [Example 1, Comparative Example 1]

[0057] The alloy strip was melted in an Ar atmosphere in a high-frequency induction furnace with the following composition: Nd: 30.0 wt%, Co: 1.0 wt%, B: 0.9 wt%, Al: 0.2 wt%, Cu: 0.2 wt%, Zr: 0.1 wt%, Ga: 0.1 wt%, Fe: balance. The molten alloy was then continuously cast using a strip casting method where the molten alloy was cooled on a water-cooled copper roller. Next, the alloy strip was coarsely pulverized using hydrogenation to obtain coarse powder. Then, 0.1 wt% of stearic acid as a lubricant was added to the coarse powder and mixed. Next, the mixture of coarse powder and lubricant was micronized using a jet mill in a nitrogen stream to achieve an average particle size of approximately 3.5 μm. At this time, the oxygen content was adjusted by setting the oxygen concentration in the jet mill system to 0 ppm (Example 1) and 50 ppm (Comparative Example 1). Next, the micro-powder was filled into a mold containing an electromagnet in a nitrogen atmosphere, oriented in a magnetic field of 15 kOe (1.19 MA / m), and simultaneously pressed into shape in a direction perpendicular to the magnetic field. The resulting molded body was then sintered in a vacuum at 1050°C for 3 hours, cooled to below 200°C, subjected to a high-temperature heat treatment at 900°C for 2 hours, and a low-temperature heat treatment at 500°C for 3 hours to obtain a sintered body. The composition of each sintered body was as follows: Nd: 13.5 atomic%, Co: 1.1 atomic%, B: 5.5 atomic%, Al: 0.5 atomic%, Cu: 0.2 atomic%, Zr: 0.07 atomic%, Ga: 0.1 atomic%, C: 0.4 atomic%, O: (see Table 1), Fe: balance. Note that ICP analysis was used for metallic elements, combustion infrared absorption was used for C, and inert gas melting infrared absorption was used for O.

[0058] The central portion of each sintered body was cut into a rectangular parallelepiped shape with dimensions of 18mm × 15mm × 12mm to obtain sintered magnets. The magnetic properties (Br, H) of each sintered magnet were measured using a BH tracer. cJ Table 1 shows the atomic percentages ([B], [Zr], [C], [O]) and magnetic properties (Br, H) of B, Zr, C, and O for Example 1 and Comparative Example 1, respectively. cJ The value of [O] is given. It should be noted that the "effective range of [O] in Example 1 and Comparative Example 1" in the table refers to the range of [O] values ​​for [B], [C], [Zr], and [O] that satisfy the following relationship (1').

[0059] 0.86×([B]+[C]-2×[Zr])-4.9<[O]<0.86×([B]+[C]-2×[Zr])-4.6…(1')

[0060] [Table 1]

[0061]

[0062] As shown in Table 1, the sintered magnet of Example 1, which satisfies the conditions of the present invention [the above relation (1')], compared with Comparative Example 1, has higher performance in H. cJ It has significantly superior characteristics.

[0063] [Examples 2-5, Comparative Examples 2-6]

[0064] Except for adjusting the amount of metal used as raw material in a prescribed manner, the process was the same as in Example 1: alloy strip preparation, hydrogenation pulverization, and mixing of lubricant in coarse powder. Next, the mixtures of coarse powder and lubricant were pulverized using a jet mill in a nitrogen stream to produce micro-powder with an average particle size of approximately 3.5 μm. At this time, the O content was adjusted by appropriately adjusting the oxygen concentration within the jet mill system. Then, the micro-powder was shaped and heat-treated using the same method as in Example 1 to obtain a sintered body. The composition of the obtained sintered body was analyzed in the same manner as in Example 1, and the results were: Nd: 13.5 atomic%, Co: 1.1 atomic%, B: refer to Table 2, Al: 0.5 atomic%, Cu: 0.2 atomic%, Zr: 0.07 atomic%, Ga: 0.1 atomic%, C: 0.4 atomic%, O: refer to Table 2, Fe: balance.

[0065] The central portion of each sintered body obtained in Examples 2-5 and Comparative Examples 2-6 was cut into a rectangular parallelepiped shape with dimensions of 18mm × 15mm × 12mm to obtain sintered magnets. The magnetic properties (Br, H) of each sintered magnet were measured using a BH tracer. cJ Table 2 shows the atomic percentages ([B], [Zr], [C], [O]) and magnetic properties (Br, H) of B, Zr, C, and O for each magnet. cJ The value of [O]. To clarify, the "valid range of [O]" in the table refers to the range of [O] values ​​for [B], [C], [Zr], and [O] in each magnet that satisfy the above relationship (1').

[0066] [Table 2]

[0067]

[0068] As shown in Table 2, the sintered magnets of Examples 2-5, which satisfy the conditions of the present invention [the above relation (1')], have a higher H than those of Comparative Examples 2-6. cJ .

[0069] Furthermore, based on the results in Tables 1 and 2, the relationship between ([B] + [C] - 2 × [Zr]) and [O] is shown for Examples 1-5 and Comparative Examples 1-6. Figure 1The coordinate graph. From Tables 1 and 2. Figure 1 It can be seen that the content of O satisfies the following relationship (1').

[0070] 0.86×([B]+[C]-2×[Zr])-4.9<[O]<0.86×([B]+[C]-2×[Zr])-4.6…(1')

[0071] Within this range, high Br and high H above 1000 kA / m were obtained. cJ That is, H cJ A properly sintered magnet satisfies the relationship described in equation (1'). On the other hand, when the O atom content exceeds [0.86 × ([B] + [C] - 2 × [Zr]) - 4.6], it is relatively high compared to R2Fe. 14 The basic composition shown in B contributes to R2Fe 14 The insufficient presence of B and C in the formation of the B phase suggests that the formation of R2Fe is due to this. 17 Phase, H cJ A significant decrease. On the other hand, when the O atom content is less than [0.86 × ([B] + [C] - 2 × [Zr]) - 4.9], relative to R2Fe 14 B represents the basic components, which contribute to R2Fe 14 The presence of excess B and C in the formation of the B phase suggests the formation of a heterogeneous phase composed of R, Fe, and B, with H... cJ The content of O atoms can be adjusted during the pulverization process of obtaining alloy micro powder by pulverizing the raw material alloy, as described in Examples 1-5 above.

[0072] [Examples 6-9]

[0073] The amount of metal used as raw material was adjusted to be Nd: 30.0 wt%, Co: 1.0 wt%, B: 0.9 wt%, Al: 0.2 wt%, Cu: 0.2 wt%, Zr: 0.1 wt%, Ga: 0-0.3 wt%, and Fe: balance. Otherwise, the same procedure as in Example 1 was followed to produce an alloy ribbon. Next, the alloy ribbon was coarsely pulverized using hydrogenation to obtain coarse powder. Then, 0.1 wt% of stearic acid as a lubricant was added to the coarse powder and mixed. Next, the mixture of coarse powder and lubricant was micronized using a jet mill in a nitrogen stream to achieve an average particle size of approximately 3.5 μm. At this time, the oxygen concentration in the jet mill system was set to 0 ppm. Next, the micronized powder was shaped and heat-treated using the same method as in Example 1 to obtain the sintered bodies of Examples 6-9. The composition of the obtained sintered body was analyzed in the same manner as in Example 1, and the results were as follows: Nd: 13.5 atomic%, Co: 1.1 atomic%, B: 5.5 atomic%, Al: 0.5 atomic%, Cu: 0.2 atomic%, Zr: 0.07 atomic%, Ga: refer to Table 3, C: 0.4 atomic%, O: refer to Table 3, Fe: balance.

[0074] The central portion of each sintered body obtained in Examples 6-9 was cut into a rectangular parallelepiped shape with dimensions of 18mm × 15mm × 12mm to obtain sintered magnets. The magnetic properties (Br, H) of each sintered magnet were measured using a BH tracer. cJ Table 3 shows the atomic percentages ([Ga], [B], [Zr], [C], [O]) and magnetic properties (Br, H) of Ga, B, Zr, C, and O for each magnet. cJ The values ​​of [O] are also recorded for the sintered magnets of Example 1. It should be noted that the "effective [O] range" in the table refers to the range of [O] values ​​for [B], [C], [Zr], and [O] in each magnet that satisfy the above relationship (1').

[0075] [Table 3]

[0076]

[0077] As shown in Table 3, the sintered magnets of Examples 1 and 6-9 that satisfy the conditions of the present invention [the above relation (1')] all have good Br and H content. cJ However, Example 7, which does not contain Ga, is compared to Examples 1 and 6 in terms of H. cJ Slightly worse, and in addition, the Ga content in Examples 8 and 9, which exceeded 0.1 atomic%, was also slightly worse than that in Examples 1 and 6.

Claims

1. An R-Fe-B based sintered magnet, characterized in that, It has the following composition: containing 12.5–14.5 atomic% R, 5.0–6.5 atomic% B, 0.02–0.5 atomic% Zr, and 0.1–1.6 atomic% C, with the balance being Fe, O, other arbitrary elements, and unavoidable impurities, wherein R is one or more elements selected from rare earth elements, with Nd being essential. Furthermore, when the atomic percentages of B, C, Zr, and O are set as [B], [C], [Zr], and [O] respectively, the following relationship (1) is satisfied. 0.86×([B]+[C]-2×[Zr])-4.9<[O]<0.86×([B]+[C]-2×[Zr])-4.6…(1).

2. The R-Fe-B sintered magnet according to claim 1, wherein, The content of O is 0.1 to 0.8 atoms.

3. The R-Fe-B sintered magnet according to claim 1 or 2, wherein, As any of the elements, it contains 0.1 to 3.5 atomic% Co, 0.05 to 0.5 atomic% Cu, and more than 0 atomic% but less than 1.0 atomic% Al.

4. The R-Fe-B sintered magnet according to claim 1 or 2, wherein, The R mentioned is only Nd.

5. The R-Fe-B sintered magnet according to claim 1 or 2, wherein, As any of the elements, it contains more than 0 and less than 0.1 atomic% Ga.

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