JP4766453B2 - Rare earth permanent magnet - Google Patents

Description

  The present invention relates to a rare earth permanent magnet containing a rare earth element R.

  In recent years, rare earth permanent magnets such as Nd—Fe—B sintered magnets have advantages such as excellent magnetic properties, Nd as a main component is abundant in resources, and is relatively inexpensive. The demand is increasing. In addition, the performance and functionality of electronic devices are remarkably increased, and Nd—Fe—B based sintered magnets used in such devices are required to have better characteristics than ever.

  Under such circumstances, research and development for enhancing magnetic properties such as coercive force and saturation magnetic flux density of Nd—Fe—B based sintered magnets are actively being promoted in various fields. For example, in Patent Document 1, by adding 0.02 at% to 0.5 at% Cu to an R—Fe—B permanent magnet, the magnetic properties and sintering temperature range of the R—Fe—B permanent magnet are reduced. There are reports of improvement. Further, for example, in Patent Document 2, the coercive force and the maximum energy product are obtained by adding Al, Cu, Si to the R—Fe—B rare earth magnet and adding at least one of Cr, Mn, and Ni. There are reports of improvement.

  By the way, the magnetic characteristics of the RTB-based rare earth permanent magnet obtained by sintering may depend on the sintering temperature. On the other hand, on an industrial production scale, it is difficult to make the heating temperature uniform throughout the sintering furnace. Therefore, the R-T-B rare earth permanent magnet is required to obtain desired magnetic characteristics even when the sintering temperature varies. Here, the temperature range where desired magnetic characteristics can be obtained is referred to as a sintering temperature range.

  Moreover, when manufacturing a R-T-B system rare earth permanent magnet, it is common to perform the aging treatment for the purpose of coercive force control after sintering. Although the coercive force of the RTB-based rare earth permanent magnet depends on the aging temperature, as described above, it is difficult to make the heating temperature in the furnace uniform during industrial production. . Therefore, the R-T-B rare earth permanent magnet is required to obtain a desired high coercive force in a wide aging temperature range. An aging temperature range in which desired magnetic characteristics can be obtained is referred to as an aging temperature range.

As a technique for improving the sintering temperature range, the present applicant has proposed an RTB-based rare earth permanent magnet containing 0.05 wt% to 0.2 wt% of Zr in Patent Document 3. According to the invention described in Patent Document 3, abnormal grain growth at the time of sintering can be suppressed by adding Zr, and therefore the reduction of the squareness ratio is suppressed even when a process such as oxygen content reduction is adopted. can do. The invention described in Patent Document 3 is also effective for improving the sintering temperature range.
JP-A-1-219143 Japanese Unexamined Patent Publication No. 1-2220803 International Publication No. 2004/029995 Pamphlet

  However, in order to obtain high magnetic properties required for high performance magnets, specifically, high coercive force (Hcj) and residual magnetic flux density (Br), the inventions described in Patent Document 1 and Patent Document 2 That is not enough. In order to further improve the coercive force and the residual magnetic flux density of the R-T-B rare earth permanent magnet, it is effective to reduce the oxygen content in the alloy. There is an inconvenience that abnormal grain growth tends to occur during the setting process, and the squareness ratio decreases. This is because the oxide in the alloy suppresses the growth of crystal grains.

  Further, Patent Document 3 is an improvement of the problem of reduction in the squareness ratio of Patent Document 1 and Patent Document 2, and is described in Patent Document 3 in view of further enhancement of performance of future applied products. The coercive force of magnets is not always satisfactory, and further improvement is strongly demanded. Furthermore, according to Patent Document 3, although it is possible to improve the sintering temperature range, considering the increase in productivity on an industrial production scale, not only the sintering temperature range but also the aging temperature range. It is desirable to expand.

  The present invention has been proposed in view of such a conventional situation, and is excellent in magnetic properties such as residual magnetic flux density and coercive force, and productivity is increased by expanding both the sintering temperature range and the aging temperature range. An object of the present invention is to provide a rare earth permanent magnet capable of improving the above.

  In order to solve the above-described problems, the rare earth permanent magnet according to the present invention has R: 25 wt% to 35 wt% (R is one or more selected from rare earth elements), Co: 0 to 4 wt%. (However, 0 is not included.), B: 0.5 wt% to 4.5 wt%, one or more selected from Cu and Al: 0.02 wt% to 0.6 wt%, Zr: 0.03 It has a composition comprising 0.25 wt%, Ga: 0.05 wt% to 0.25 wt%, O: 0.03 wt% to 0.2 wt%, Fe and inevitable impurities: the balance.

  As described above, by adding Zr to a composition containing a very low amount of oxygen and containing R, Co, B, Cu, and Al, the rare earth permanent magnet has magnetic properties such as residual magnetic flux density and coercive force. Good and wide sintering temperature range is realized. In the present invention, the coercivity can be further improved by adding an appropriate amount of Ga. Further, the addition of an appropriate amount of Ga increases the aging temperature range. Therefore, in the rare earth permanent magnet having the above composition, the residual magnetic flux density and the coercive force are compatible at a high level, and a particularly excellent coercive force can be obtained. In addition, the rare earth permanent magnets described above can be stably produced even on an industrial production scale because the aging temperature range can be expanded by adding Ga while securing a wide sintering temperature range by adding Zr. It becomes.

  The rare earth permanent magnet according to the present invention has a high coercive force and a residual magnetic flux density, and an excellent squareness ratio can be realized. Further, in the rare earth permanent magnet according to the present invention, since both the sintering temperature range and the aging temperature range are expanded, it is possible to use a large-scale sintering furnace or the like, and production without deteriorating the characteristics. It is possible to improve the performance.

Hereinafter, a rare earth permanent magnet to which the present invention is applied will be described in detail with reference to the drawings.
First, the chemical composition of the rare earth permanent magnet to which the present invention is applied will be described. Here, the chemical composition refers to the chemical composition in the rare earth permanent magnet after sintering.

In the rare earth permanent magnet of the present invention, the content of rare earth element R is 35 wt% or less. When the rare earth element R exceeds 35 wt%, the volume ratio of the R ₂ T ₁₄ B phase, which is the main phase, is reduced, and the residual magnetic flux density is significantly reduced. Further, the rare earth element R reacts with oxygen, the amount of oxygen contained increases, and accordingly, the R-rich phase effective for generating the coercive force decreases, leading to a significant decrease in the coercive force. On the other hand, when the content of the rare earth element R is less than 25 wt%, the R ₂ T ₁₄ B phase, which is the main phase of the rare earth permanent magnet, is not sufficiently generated, and α-Fe or the like having soft magnetism is precipitated. Is significantly reduced. For the above reasons, the rare earth element R content is set to 25 wt% to 35 wt%. The desirable rare earth element R content is 28 wt% to 32 wt%. Furthermore, it is most desirable that the content of the rare earth element R is 30 wt% or less. By setting the content of the rare earth element R to 30 wt% or less, the volume ratio of the R ₂ T ₁₄ B phase, which is the main phase, is increased, and the residual magnetic flux density is greatly improved.

  Here, the rare earth element R is one or more rare earth elements. Specifically, the rare earth element R is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu.

As the rare earth element R, it is preferable to select and use Nd and Dy. This is because Nd is abundant in resources and relatively inexpensive. Further, Dy has an advantage that the anisotropic magnetic field of the Dy ₂ T ₁₄ B phase is larger than the anisotropic magnetic field of the Nd ₂ T ₁₄ B phase, for example, and is effective in improving the coercive force. The Dy content is desirably 0.1 wt% to 8 wt%. It is desirable to determine the amount of Dy within the above range depending on which of the residual magnetic flux density and the coercive force is important. That is, when it is desired to obtain a high residual magnetic flux density, the Dy amount is preferably 0.1 wt% to 3.5 wt%, and when a high coercive force is desired, the Dy amount is desirably 3.5 wt% to 8 wt%. .

  The rare earth permanent magnet of the present invention can contain 0 to 4 wt% (excluding 0) of Co. Further, the desirable Co content is 0 to 2 wt% (however, 0 is not included). Co forms the same phase as Fe. However, when Co is contained in the rare earth permanent magnet of the present invention, it is effective in improving the Curie temperature and improving the corrosion resistance of the grain boundary phase.

  The rare earth permanent magnet of the present invention contains 0.5 wt% to 4.5 wt% of B. When the B content is less than 0.5 wt%, a high coercive force cannot be obtained. However, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit of the B content is 4.5 wt%. Desirable B content is 0.5 wt% to 1.5 wt%.

  The rare earth permanent magnet of the present invention contains 0.02 wt% to 0.6 wt% of one or two selected from Cu and Al. By containing one or two of Al and Cu within this range, it is possible to increase the coercive force, corrosion resistance, and temperature characteristics of the obtained rare earth permanent magnet. In the case of adding Al, a desirable amount of Al is 0.03 wt% to 0.25 wt%. Moreover, when adding Cu, the desirable amount of Cu is 0 to 0.15 wt% (however, 0 is not included).

  The rare earth permanent magnet of the present invention contains 0.03 wt% to 0.25 wt% Zr. Zr has the effect of suppressing abnormal grain growth during the sintering process. If the oxygen content is reduced for the purpose of improving the magnetic properties of rare earth permanent magnets, abnormal growth of crystal grains during the sintering process tends to be a problem. Zr can suppress the abnormal growth of crystal grains at this time and make the structure of the sintered body uniform and fine. Therefore, the addition of Zr becomes significant when the oxygen content in the rare earth permanent magnet is low. Further, an appropriate amount of Zr expands the sintering temperature range of the rare earth permanent magnet. When the amount of Zr is too small, the effect of suppressing abnormal growth of crystal grains in the sintering process becomes insufficient, and the squareness ratio of the rare earth permanent magnet tends to deteriorate. In addition, the improvement effect of the sintering temperature range tends to be insufficient. Therefore, the lower limit of the amount of Zr is set to 0.03 wt%. Conversely, when the amount of Zr is excessive, the residual magnetic flux density and coercive force of the rare earth permanent magnet tend to decrease. Therefore, the upper limit of the amount of Zr is set to 0.25 wt%.

  The rare earth permanent magnet of the present invention contains 0.03 wt% to 0.2 wt% of oxygen (O). If the amount of oxygen is large, the oxide phase, which is a nonmagnetic component, increases and the magnetic properties are degraded. Therefore, the upper limit of the oxygen amount is set to 0.2 wt%. However, if the oxygen amount in the rare earth permanent magnet is simply reduced, the oxide phase having the effect of suppressing crystal grain growth decreases, and grain growth easily occurs in the process of obtaining a sufficient density increase during sintering. Therefore, in the present invention, as described later, a predetermined amount of Zr and Ga having an effect of suppressing abnormal growth of crystal grains during the sintering process is contained. If the oxygen content is too small, oversintering tends to occur, and the squareness decreases, so the lower limit of the amount of oxygen is 0.03 wt%. A more desirable amount of oxygen is 0.03 wt% to 0.1 wt%.

  The rare earth permanent magnet of the present invention may contain C. The content of C is 0.03 wt% to 0.1 wt%. If the amount of C is less than 0.03 wt%, oversintering is likely to occur, and the squareness may be reduced. If the amount of C exceeds 0.1 wt%, both sinterability and squareness may be reduced.

  The rare earth permanent magnet of the present invention may contain N. The N content is 0.02 wt% to 0.05 wt%. If the amount of N is less than 0.02 wt%, oversintering is likely to occur, and the squareness may be reduced. If the amount of N exceeds 0.05 wt%, both sinterability and squareness may be reduced.

  The rare earth permanent magnet of the present invention contains 0.05 wt% to 0.25 wt% Ga in addition to the above composition. Addition of Ga serves to further increase the coercivity of the rare earth permanent magnet. Further, the addition of Ga can widen the aging temperature range. For this reason, even when a large furnace is used for the aging treatment, desired characteristics can be obtained, and the productivity of the rare earth permanent magnet can be improved.

  Further, Ga, like Zr, has a function of suppressing abnormal grain growth during the sintering process. For this reason, by using Ga and Zr together, abnormal grain growth in the firing process can be reliably suppressed, and the squareness ratio can be further improved. Also, with respect to the sintering temperature range, a higher improvement effect can be obtained as compared with the case where Zr is added alone. If the amount of Ga is too small, the effect of the present invention will not be sufficiently exerted, so the lower limit of the amount of Ga is 0.05 wt%. Conversely, when the amount of Ga becomes excessive, the residual magnetic flux density and coercive force of the rare earth permanent magnet tend to decrease. Therefore, the upper limit of the amount of Ga is set to 0.25 wt%. A more desirable Ga amount is 0.05 wt% to 0.15 wt%.

  The combined addition of appropriate amounts of Ga and Zr is very effective when the amount of rare earth element R contained in the alloy is reduced. By making the content of the rare earth element R 30 wt% or less, for example, the residual magnetic flux density (Br) can be greatly improved. However, since the liquid phase component during sintering is reduced, the sinterability is reduced. Grain growth becomes difficult. As a countermeasure, if the sintering temperature is raised in order to increase the density of the sintered body, there is a disadvantage that abnormal grain growth tends to occur. The combined addition of appropriate amounts of Ga and Zr is very effective in suppressing abnormal grain growth when the amount of rare earth element R is 30 wt% or less. By adding Ga and Zr in combination, the advantage of reducing the amount of rare earth element R (the effect of improving residual magnetic flux density) is ensured while suppressing abnormal grain growth caused by reducing the amount of rare earth element R. Can get to.

Therefore, the composition of the rare earth permanent magnet of the present invention is expressed as follows.
R: 25 wt% to 35 wt% (R is one or more selected from rare earth elements)
Co: 0 to 4 wt% (excluding 0)
B: 0.5 wt% to 4.5 wt%
One or more selected from Cu and Al: 0.02 wt% to 0.6 wt%
Zr: 0.03-0.25 wt%
Ga: 0.05 wt% to 0.25 wt%
O: 0.03 wt% to 0.2 wt%
Fe and inevitable impurities: balance

Next, the suitable manufacturing method of the rare earth permanent magnet of this invention is demonstrated.
In the present embodiment, a powder of a main phase alloy mainly composed of R ₂ T ₁₄ B (T is Fe, Co or Fe) phase, and a grain boundary mainly composed of R and T but not B A method for producing a rare earth permanent magnet according to the present invention using a phase alloy powder will be described.

  First, a main phase alloy and a grain boundary phase alloy are obtained by strip casting the raw metal in a vacuum or an inert gas, preferably in an Ar atmosphere. As the raw material metal, rare earth metals or rare earth alloys, pure iron, ferroboron, and alloys thereof can be used. The obtained raw material alloy is subjected to a solution treatment as necessary when there is solidification segregation. The conditions may be maintained in a region of 700 ° C. to 1500 ° C. for 1 hour or more in a vacuum or Ar atmosphere.

  The rare earth permanent magnet of the present invention contains Zr as an essential component, but Zr is preferably supplied from a main phase alloy. Specifically, the main phase alloy can contain Zr, Al and the like in addition to the rare earth element R and the transition metal elements T and B. The main phase alloy is, for example, Nd-Dy-B-Al. -Zr-Fe and Nd-Dy-B-Al-Zr-Ga-Fe alloys. In addition, the grain boundary phase-based alloy can be an alloy containing Ga, Cu, Co, or the like, not containing B but mainly containing R and T. The grain boundary phase alloy is, for example, a Dy—Cu—Co—Al—Fe alloy or a Dy—Cu—Co—Al—Ga—Fe alloy.

  After the main phase alloy and the grain boundary phase alloy are produced, each of these master alloys is ground separately or together. The pulverization process includes a coarse pulverization process and a fine pulverization process. First, each mother alloy is coarsely pulverized until the particle size becomes about several hundred μm. The coarse pulverization is desirably performed in an inert gas atmosphere using a stamp mill, a jaw crusher, a brown mill or the like. Moreover, each alloy can be coarsely pulverized by performing coarse pulverization after occluding hydrogen or releasing hydrogen after occluding hydrogen.

  After the coarse pulverization process, the process proceeds to the fine pulverization process. In the fine pulverization, a jet mill is mainly used, and a coarsely pulverized powder having a particle size of about several hundreds of μm is pulverized until the average particle size becomes 3 to 5 μm. The jet mill opens a high-pressure inert gas (for example, nitrogen gas) from a narrow nozzle to generate a high-speed gas flow, and the high-speed gas flow accelerates the coarsely pulverized powder. Or it is the method of generating and colliding with a container wall. As a result, a main phase alloy powder and a grain boundary phase alloy powder are obtained.

  When the main phase alloy and the grain boundary phase alloy are separately ground in the fine grinding step, the finely ground main phase alloy powder and the grain boundary phase alloy powder are mixed in a nitrogen atmosphere. The mixing ratio of the main phase alloy powder and the grain boundary phase alloy powder may be about 80:20 to 97: 3 by weight. Similarly, the mixing ratio when the main phase alloy and the grain boundary phase alloy are pulverized together may be about 80:20 to 97: 3 by weight. By adding about 0.01 wt% to 0.3 wt% of additives such as zinc stearate at the time of fine pulverization, fine powder having high orientation can be obtained at the time of molding.

Next, a mixed powder composed of a main phase alloy powder and a grain boundary phase alloy powder is filled in a mold held by an electromagnet and molded in a magnetic field with its crystal axis oriented by applying a magnetic field. The magnetic field molding, in a magnetic field of ^{12kOe~17kOe, 0.7t / cm 2 ~1.5t /} cm 2 may be carried out at a pressure of about.

  After molding in a magnetic field, the compact is sintered in a vacuum or an inert gas atmosphere. Although it is necessary to adjust sintering temperature by various conditions, such as a composition, a grinding | pulverization method, a particle size, and a particle size distribution difference, what is necessary is just to sinter at 1000 to 1100 degreeC for about 1 to 5 hours.

  After sintering, the obtained sintered body can be subjected to an aging treatment. The aging treatment is important for controlling the coercive force. When the aging treatment is performed in two stages, it is effective to hold for a predetermined time in the vicinity of 800 ° C. and 600 ° C. When the heat treatment in the vicinity of 800 ° C. is performed after sintering, the coercive force increases, which is particularly effective in the mixing method. In addition, since the coercive force is greatly increased by heat treatment at around 600 ° C., when the aging treatment is performed in one stage, the aging treatment at around 600 ° C. is preferably performed. As described above, the rare earth permanent magnet of the present invention can be obtained.

  In the rare earth permanent magnet of the present invention, the oxygen content is set to 0.03 wt% to 0.2 wt% for the purpose of obtaining high magnetic properties. It is adjusted by controlling the amount of oxygen contained. In particular, suppressing the atmosphere in each step from hydrogen pulverization to sintering to a low oxygen concentration of less than 100 ppm is effective in adjusting the oxygen content within the range of 0.03 wt% to 0.2 wt%. is there.

  Further, the amount of C contained in the rare earth permanent magnet is adjusted by the type and amount of the grinding aid used in the production process. Further, the amount of N contained in the rare earth permanent magnet is adjusted by the type and amount of the raw material alloy, the pulverizing conditions when the raw material alloy is pulverized in a nitrogen atmosphere, and the like.

  In the rare earth permanent magnet of the present invention obtained as described above, the content of rare earth elements R, Co, B, Cu, Al, O, Zr and Ga is made appropriate so that a high residual magnetic flux density and coercive force can be obtained. In addition, both the sintering temperature range and the aging temperature range are expanded. Further, in the rare earth permanent magnet of the present invention, abnormal grain growth during the firing process is reliably prevented.

  Hereinafter, specific examples to which the present invention is applied will be described based on experimental results. In addition, this invention is not limited to description of a following example.

Example 1
(1) Raw material alloys Eight types of alloys a1 to a4 and b1 to b4 shown in Table 1 were produced by strip casting.

(2) Hydrogen pulverization step After occluding hydrogen at room temperature, hydrogen pulverization treatment was performed in which dehydrogenation was performed in an Ar atmosphere at 600 ° C for 1 hour.
In this example, in order to make the sintered body oxygen amount 0.03 wt% to 0.2 wt%, each process from hydrogen treatment (recovery after pulverization treatment) to sintering (put into the sintering furnace) is performed. The atmosphere is suppressed to an oxygen concentration of less than 100 ppm. Hereinafter, this is referred to as a low oxygen process.

(3) Grinding step A grinding aid was mixed before fine grinding. In addition, although the coarse pulverization process may be performed after the hydrogen pulverization process, it is omitted in this embodiment. The grinding aid is not particularly limited, but in this example, zinc stearate was mixed in an amount of 0.05% to 0.1%. The mixing of the grinding aid may be performed for about 5 minutes to 30 minutes using, for example, a Nauter mixer.
Thereafter, fine pulverization is performed using an airflow pulverizer. In this experiment, fine pulverization was performed using a jet mill. Using an airflow pulverizer, fine pulverization was performed until the alloy powder had an average particle size of about 3 μm to 6 μm. In this experiment, pulverized powder having an average particle size of 4 μm was prepared.
Of course, both the mixing step and the fine pulverization step of the pulverization aid were performed by a low oxygen process.

(4) Blending step In order to perform the experiment efficiently, several types of finely pulverized powders may be mixed and mixed so as to have a desired composition. In this case, the mixing may be performed for about 5 to 30 minutes using, for example, a Nauter mixer.
Although the blending step is preferably performed by a low oxygen process, when the amount of oxygen in the sintered body is slightly increased, the amount of oxygen in the molding fine powder is adjusted in this step. For example, a fine powder having the same composition and average particle diameter is prepared and left in an oxygen-containing atmosphere of 100 ppm or more for several minutes to several hours, whereby a fine powder of several thousand ppm can be obtained. The amount of oxygen is adjusted by mixing these two types of fine powders in a low oxygen process.
In this example, a1, a2, b1, and b2 of the alloys having the compositions shown in Table 1 were blended so as to have the final composition shown in Table 2. The upper part of Table 2 is an example in which Ga is added from a grain boundary phase alloy, and the lower part is an example in which Ga is added from a main phase alloy. After blending, hydrogen pulverization treatment was performed, and then fine pulverization was performed with a jet mill so that the average particle size became 4 μm.

(5) Molding step The obtained fine powder is molded in a magnetic field. Specifically, a fine powder is filled in a mold held by an electromagnet, and molding is performed in a magnetic field in a state where the crystal axis is oriented by applying a magnetic field. The magnetic field molding, in a magnetic field of ^{12kOe~17kOe, 0.7t / cm 2 ~1.5t /} cm 2 may be carried out at a pressure of about. In this experiment, molding was performed in a magnetic field of 15 kOe at a pressure of 1.2 t / cm ² to obtain a molded body. This step was also performed by a low oxygen process.

(6) Sintering / aging process This compact was sintered in a vacuum at 1070 ° C to 1130 ° C for 4 hours and then rapidly cooled. Next, the obtained sintered body was subjected to a two-stage aging treatment. The two-stage aging treatment of the rare earth permanent magnets shown in Tables 3 and 4 was 1 hour at 850 ° C. and 2.5 hours at 570 ° C. (both in an Ar atmosphere).

  About the obtained rare earth permanent magnet, residual magnetic flux density (Br), coercive force (HcJ), and squareness ratio (Hk / HcJ) were measured with a BH tracer. The results are shown in Tables 3 and 4. The amount of gas of the sintered body, that is, the amount of oxygen, the amount of nitrogen, and the amount of carbon are also shown in Tables 3 and 4. In Tables 3 and 4, the carbon content is as low as 0.03 wt% to 0.1 wt%, and the nitrogen content is as low as 0.02 wt% to 0.05 wt%. Is suppressed to 0.1 wt% or less in all samples.

  Hk is the magnetic field strength when the magnetization in the second quadrant of the magnetic hysteresis loop (4πI-H curve) is 90% of the residual magnetic flux density Br. The squareness ratio Hk / HcJ is particularly related to the effect of an external magnetic field and demagnetization due to a temperature rise, and is a value that serves as an index of magnet characteristics during actual use. Further, when Hk / HcJ is low, the magnetic field strength required for magnetization increases. Furthermore, a permanent magnet having a low Hk / HcJ has a problem with the loop shape in the second quadrant of the magnetic hysteresis loop, and the design conditions of the system to which the magnet is applied become severe.

  Table 3 shows the results when Ga is added from the grain boundary phase alloy (the upper part of Table 2). No. with a Ga content of less than 0.05 wt%. 1-No. The permanent magnet No. 6 showed a low coercive force (HcJ). In the permanent magnets (No. 19 to No. 21) having a Ga content exceeding 0.25 wt%, a significant decrease in residual magnetic flux density (Br) was observed. If the sintering temperature range in which the squareness ratio (Hk / HcJ) of 90% or more is obtained is defined as the sintering temperature range, the sintering temperature range of 40 ° C. or more is realized in all the samples shown in Table 3. These samples and No. 7-No. In comparison with 18 permanent magnets, when Ga is added from a grain boundary phase alloy, each element of rare earth elements R, Co, B, Cu, Al, oxygen (O) and Zr is within an appropriate range, and Ga By setting the amount to 0.05 wt% to 0.25 wt%, it is possible to obtain a wide sintering temperature range while maintaining a high level of residual magnetic flux density (Br) and coercive force (HcJ) in a rare earth permanent magnet. Recognize.

  Table 4 shows the results when Ga is added from the main phase alloy (lower part of Table 2). Even when Ga was added from the main phase alloy, the same tendency as shown in Table 3 as a result of adding Ga from the grain boundary phase alloy was shown. For example, No. having a Ga content of less than 0.05 wt%. 22-No. 24 showed a low coercive force (HcJ). In the permanent magnets (No. 34 to No. 36) having a Ga content exceeding 0.25 wt%, a significant decrease in residual magnetic flux density (Br) was observed.

  Therefore, from the results of Example 1, by setting the Ga amount to 0.05 wt% to 0.25 wt%, the residual magnetic flux density (Br) and the coercive force (HcJ) are compatible at a high level in the rare earth permanent magnet, It can be seen that a wide sintering temperature range can be obtained. Moreover, it turns out that the said effect is acquired also in any when Ga is added from a grain boundary phase type alloy, and Ga is added from a main phase type alloy.

(Example 2)
When Ga was added from the main phase alloy (Table 4) and the sintering temperature was constant (1090 ° C.), the aging temperature in the two-stage aging treatment was set to the combination shown in Table 5. . Other than that, a rare earth permanent magnet was produced according to Example 1. Table 5 shows the results of the coercive force (HcJ) and the squareness ratio (Hk / HcJ) of the obtained rare earth permanent magnet.

  When the Ga content was 0, the coercive force (HcJ) showed a low value of 22 kOe or less at any aging temperature condition within the examination range. Further, when the aging temperature of the second stage was set to a relatively high temperature of 570 ° C. to 600 ° C., the squareness ratio (Hk / HcJ) was reduced to 95% or less.

  When Ga was added by 0.02 wt%, the coercive force (HcJ) was improved as compared with the case where the Ga content was 0, but the improvement was small. Further, when the aging temperature of the second stage was set to a relatively high temperature (600 ° C.), the squareness ratio (Hk / HcJ) was reduced to 95% or less as in the case where the Ga content was 0.

  When an aging temperature range in which a high coercive force (HcJ) exceeding 22 kOe can be obtained is defined as an aging temperature range, the aging temperature range when the Ga content is 0.05 wt% to 0.25 wt% is as described above ( The Ga content was expanded compared to 0 or 0.02 wt%.

  However, when the Ga addition amount is further increased to 0.28 wt%, a high value is obtained for the coercive force (HcJ), but when the second stage aging temperature is set low, the squareness ratio (Hk / HcJ) tended to decrease.

  Therefore, from the results of Example 2, by setting the Ga content in the composition to 0.05 wt% to 0.25 wt%, it is possible to achieve a high coercive force in the rare earth permanent magnet and to ensure a wide aging temperature range. Recognize.

(Example 3)
Of the alloys having the composition shown in Table 1, a3, a4, b3, and b4 were used so that the final composition shown in Table 6 was obtained. Subsequent steps were carried out in accordance with Example 1 to obtain an RTB-based rare earth permanent magnet. In either case, Ga is added from the main phase alloy. In addition, the permanent magnet of final composition A (No. 37-No. 39) mix | blends alloy a3 and alloy b3 by the weight ratio of 97: 3, and is permanent of final composition B (No. 40-No. 42). The magnet was composed of alloys a4 and b4 at a weight ratio of 80:20.

  Table 7 shows the results obtained by measuring the residual magnetic flux density (Br), the coercive force (HcJ), and the squareness ratio (Hk / HcJ) of the obtained rare earth permanent magnet with a BH tracer. Table 7 also shows the amount of gas of the sintered body, that is, the amount of oxygen, the amount of nitrogen, and the amount of carbon. Table 7 also shows the magnetic characteristics when the sintering temperatures were 1080 ° C. to 1120 ° C. and 1000 ° C. to 1040 ° C., respectively.

  From Table 7, while using Ga and Zr together, these content was made into No. 37-No. No. 42 shows a high squareness ratio exceeding 90% at any sintering temperature. Further, in Table 7, the carbon amount is as low as 0.03 wt% to 0.1 wt% and the nitrogen amount is as low as 0.02 wt% to 0.05 wt%. By adopting the low oxygen process, especially the oxygen amount is All samples are suppressed to 0.1 wt% or less.

Example 4
About the permanent magnet of the composition A (No. 37-No. 39) and the composition B (No. 40-No. 42) shown in Table 7, the sintering temperature was made constant (1100 ° C. and 1020 ° C., respectively). Under the conditions, the aging temperature in the two-stage aging treatment was set to the combinations shown in Table 8. Other than that, a rare earth permanent magnet was produced according to Example 1. Table 8 shows the results of the coercive force (HcJ) and the squareness ratio (Hk / HcJ) of the obtained rare earth permanent magnet.

As shown in Table 8, it was found that a high coercive force can be obtained without degrading the squareness ratio under any aging temperature condition.
Therefore, it can be seen from the results of Example 4 that by setting the Ga content in the composition to an appropriate amount, a high coercive force can be achieved in the rare earth permanent magnet and a wide aging temperature range can be secured.

Claims (3)

  R: 25 wt% to 35 wt% (R is one or more selected from rare earth elements), Co: 0 to 4 wt% (however, 0 is not included), B: 0.5 wt% to 4. wt. 5 wt%, one or more selected from Cu and Al: 0.02 wt% to 0.6 wt%, Zr: 0.03 to 0.25 wt%, Ga: 0.05 wt% to 0.25 wt%, O : 0.03 wt% to 0.2 wt%, Fe and unavoidable impurities: A rare earth permanent magnet having a composition comprising the balance.   The rare earth permanent magnet according to claim 1, wherein C is 0.03 wt% to 0.1 wt%. The rare earth permanent magnet according to claim 1, wherein N is 0.02 wt% to 0.05 wt%.