JP2015122395A - Method for manufacturing r-t-b-based sintered magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an R-T-B-based sintered magnet which has high Hand high H/Hwhile suppressing the reduction in Band even under a high-temperature condition, has a superior H.SOLUTION: A method for manufacturing an R-T-B-based sintered magnet comprises the steps of: preparing main alloy powder including R, B, Ga, the balance T, and inevitable impurities; preparing secondary alloy powder including Pr and Ti; preparing mixed alloy powder by mixing the main alloy powder and the secondary alloy powder so that the content of Ti in the mixed alloy powder is equal to or less than 0.3 mass% to 100 mass% of the mixed alloy powder after the mixing; preparing a mold by molding the mixed alloy powder; preparing an R-T-B-based sintered magnet material by sintering the mold; preparing an RH distribution source; performing a process for RH supply and diffusion by supplying Dy or Tb of RH distribution source to the R-T-B-based sintered magnet material, and diffusing it therein; and performing a thermal treatment on the R-T-B-based sintered magnet after the step of performing the process for RH supply and diffusion.

Description

  The present invention relates to a method for producing an RTB-based sintered magnet.

  R-T-B sintered magnets (R is at least one of rare earth elements and always contains Nd, T is at least one kind of transition metal elements and always contains Fe), and has the highest performance among permanent magnets It is known as a magnet, and is used in various motors such as voice coil motors (VCM) for hard disk drives, motors for electric vehicles, motors for hybrid vehicles, and home appliances.

The R-T-B based sintered magnet is mainly located in a main phase (hereinafter referred to as “R ₂ T ₁₄ B phase”) composed of a compound having an R ₂ T ₁₄ B type crystal structure and a grain boundary portion of this main phase. It consists of a grain boundary phase. The main phase R ₂ T ₁₄ B phase is a ferromagnetic phase and mainly contributes to the magnetizing action of the R-T-B system sintered magnet.

The _RTB -based sintered magnet has irreversible thermal demagnetization because the coercive force H _cJ (hereinafter simply referred to as “H _cJ ”) decreases at high temperatures. Therefore, especially when used for a motor for an electric vehicle or a motor for a hybrid vehicle, it is required to have a high _HcJ even at a high temperature.

In the R-T-B based sintered magnet, a part of the light rare earth element RL (mainly Nd and / or Pr) contained in R in the main phase R ₂ T ₁₄ B phase is converted to heavy rare earth element RH (mainly Dy And / or Tb) is known to improve the coercive force H _cJ (hereinafter, simply referred to as “H _cJ ”), and the H _cJ increases as the substitution amount of the heavy rare earth element RH increases.

However, when the light rare earth element RL in the R ₂ T ₁₄ B phase is replaced with the heavy rare earth element RH, H _cJ is improved, while the residual magnetic flux density B _r (hereinafter simply referred to as “B _r ”) is reduced. In addition, heavy rare earth elements, particularly Dy, have a problem that their supply is not stable and the price fluctuates because the production area is limited. Therefore, to improve the H _cJ are sought without reducing the B _r without using as much as possible the heavy rare-earth element RH.

In Patent Document 1, the amount of B is made lower than that of a normal R-T-B alloy, and at least one metal element M selected from Al, Ga, and Cu is contained, thereby providing an R ₂ T ₁₇ phase. By generating a sufficient volume fraction of the transition metal rich phase (R ₆ T ₁₃ M) generated using the R ₂ T ₁₇ phase as a raw material, R having a high coercive force while suppressing the content of Dy It is described that a -T-B rare earth sintered magnet can be obtained.

Further, as a means for improving the _{HcJ of} an R-T-B system sintered magnet, a metal, an alloy, a compound, or the like containing a heavy rare earth element RH is supplied to the sintered magnet by a specific means, and the heavy rare earth element RH is subjected to heat treatment. It was diffused inside the magnet, by replacing the light rare-earth elements RL of R 2 _T 14 _B Aisotokara unit at earth element RH, a method of improving the H _cJ while suppressing a decrease in B _r is proposed ing.

  For example, in Patent Document 2, a bulk body containing an R—Fe—B rare earth sintered magnet body and a heavy rare earth element RH (at least one selected from the group consisting of Dy, Ho, and Tb) is disposed in a processing chamber. Then, by heating them to 700 ° C. or more and 1000 ° C. or less, the heavy rare earth element RH is supplied to the surface of the R—Fe—B rare earth sintered magnet body from the bulk body while the heavy rare earth element RH is supplied to R—Fe—B. Discloses a method of diffusing into a rare earth sintered magnet body.

  Patent Document 3 discloses that a plurality of R-T-B sintered magnet bodies and a plurality of RH diffusion sources containing heavy rare earth elements RH are relatively movable and can be brought close to or in contact with each other. And heating the RTB-based sintered magnet body and the RH diffusion source while continuously or intermittently moving them in the processing chamber, thereby converting the heavy rare earth element RH from the RH diffusion source to RT. -Discloses a method of diffusing the B-based sintered magnet body while supplying it to the surface.

International Publication No. 2013/008756 International Publication No. 2007/102391 International Publication No. 2011/007758

According to Patent Document 1, although an _RTB -based sintered magnet having a higher H _cJ than that of the prior _art can be obtained, the high H is required even at high temperatures required for use in motors for electric vehicles and motors for hybrid vehicles. _{In order} to satisfy _cJ , the use of Dy is indispensable. Therefore, in order to reduce the amount of Dy used, a method of supplying heavy rare earth elements to an RTB-based sintered magnet as disclosed in Patent Documents 2 and 3 and diffusing it inside must be applied. I don't get it.

However, when the method disclosed in Patent Documents 2 and 3 is applied to the R-T-B rare earth sintered magnet of Patent Document 1, the squareness ratio H _k / H _cJ (hereinafter simply referred to as “H _k / H _cJ ” _). H _k is the position at which J becomes a constant value relative to the value of J _r [residual magnetization] in the second quadrant of the J [magnetization magnitude] -H [magnetic field strength] curve. in H value .R-T-B based sintered magnet of 0.9 J _r is often used as a value a certain percentage.) is lowered significantly.

Provided by the present invention has a high _{H cJ} and high _H k _{/ H cJ} while suppressing a decrease in _{B r,} and method for producing the R-T-B-based sintered magnet having excellent _{H cJ} even at high temperatures With the goal.

The manufacturing method of the RTB system sintered magnet of the present invention according to claim 1 comprises:
R30.0 to 31.7% by mass (R is at least one of rare earth elements and must contain Nd),
B0.90-0.96 mass%,
Ga 0.15-0.4 mass%,
Preparing a main alloy powder containing the balance T (T is at least one of transition metal elements and necessarily contains Fe) and inevitable impurities;
Preparing a sub-alloy powder containing Pr and Ti;
Mixing the main alloy powder and the sub-alloy powder so that Ti contained in 100% by mass of the mixed alloy powder after mixing is 0.3% by mass or less, and preparing a mixed alloy powder;
Forming a mixed alloy powder and preparing a formed body; and
Sintering the compact and preparing an R-T-B sintered magnet material;
Providing an RH diffusion source comprising a metal, alloy or compound containing Dy or Tb;
Supplying RH diffusion source Dy or Tb to the R-T-B system sintered magnet material, and performing an RH supply diffusion treatment;
A step of heat-treating the RTB-based sintered magnet after the RH supply diffusion treatment step;
It is characterized by including.

  The method for producing an RTB-based sintered magnet according to a second aspect of the present invention is characterized in that, in the first aspect, the secondary alloy powder contains Pr 53 to 66 mass% and Ti 5 to 21 mass%. To do.

  According to a third aspect of the present invention, there is provided a method for producing an RTB-based sintered magnet according to the first or second aspect of the present invention, wherein the secondary alloy powder contains Fe and Al.

According to the present invention, while suppressing the decrease in _{B r} has a high _{H cJ} and high _H k _{/ H cJ,} and provides R-T-B based sintered magnet having excellent _{H cJ} even at high temperatures can do.

  In addition, according to the present invention, since the content of relatively expensive Ga can be reduced, it is possible to provide an RTB-based sintered magnet at a low cost.

6 is a graph showing the relationship between the Ti amount of the _RTB -based sintered magnet material of Example 1 and _HcJ . It is a graph showing the relationship between the Ti content and the B _r of the R-T-B based sintered magnet material of Example 1. It is a graph which shows the relationship between Ti amount of the _{RTB type |} system _| group sintered magnet raw material of Example 1, and Hk / _HcJ . 4 is a graph showing the relationship between the Ti amount of the _RTB -based sintered magnet of Example 1 and _HcJ . It is a graph showing the relationship between the Ti content and the B _r of the R-T-B based sintered magnet of Example 1. 4 is a graph showing the relationship between the amount of Ti of the _RTB -based sintered magnet of Example 1 and Hk / H _cJ . 4 is a photograph showing a result of FE-SEM structure observation of the RTB-based sintered magnet of Example 1. FIG. 4 is a photograph showing a result of FE-SEM structure observation of the RTB-based sintered magnet of Example 1. FIG. 4 is a photograph showing a result of FE-SEM structure observation of the RTB-based sintered magnet of Example 1. FIG. 4 is a photograph showing a result of FE-SEM structure observation of the RTB-based sintered magnet of Example 1. FIG. 4 is a photograph showing the concentration distribution of Pr by EPMA of the RTB-based sintered magnet of Example 1. FIG. 4 is a photograph showing a result of FE-SEM structure observation of the RTB-based sintered magnet of Example 1. FIG. It is a graph which shows the relationship between Ti amount of the _{RTB type |} system _| group sintered magnet raw material of Example 2, and _HcJ . 6 is a graph showing the relationship between the amount of Ti of an RTB-based sintered magnet material of Example 2 and _Br . It is a graph which shows the relationship between Ti amount of the _{RTB type |} system _| group sintered magnet raw material of Example 2, and Hk / _HcJ . It is a graph which shows the relationship between Ti amount of the _RTB system sintered magnet of Example 2, and _HcJ . It is a graph showing the relationship between the Ti content and the B _r of the R-T-B based sintered magnet of Example 2. It is a graph which shows the relationship between Ti amount of the _{RTB type |} system _| group sintered magnet of Example 2, and Hk / _HcJ .

  In the following description, RH of the RH diffusion source is supplied to the surface of the R-T-B system sintered magnet material as in Patent Documents 2 and 3, and RH is supplied to the R-T-B system sintered magnet material. The diffusion inside is referred to as “RH supply diffusion processing”. In addition, the diffusion of RH into the RTB-based sintered magnet material without performing the supply of RH after the RH supply diffusion process is referred to as “RH diffusion process”. Furthermore, the heat treatment performed for the purpose of improving the magnet characteristics of the RTB-based sintered magnet after the RH supply diffusion treatment or after the RH diffusion treatment is simply referred to as “heat treatment”.

  In the following description, the RTB system sintered magnet before the RH supply diffusion process is referred to as “RTB system sintered magnet material”, and the RTB system after the RH supply diffusion process. The sintered magnet is referred to as an “RTB-based sintered magnet”. In addition, a grain boundary that exists between two main phases in a grain boundary existing in an R-T-B system sintered magnet is called a “two-grain grain boundary” and exists between three or more main phases. Grain boundaries that occur are called “grain boundary triple points”.

The main feature of the manufacturing method of the RTB-based sintered magnet of the present invention is that the conventional RTB-based sintered magnet (R, B, Ga and A main alloy powder having substantially the same components and composition as that of the magnet of Patent Document 1 including Fe and the like is mixed, and sub-alloy powder containing Pr and Ti is mixed, molded, and sintered. The purpose is to subject the TB sintered magnet material to RH supply diffusion treatment and heat treatment. This has a high _{H cJ} and high _H k _{/ H cJ} while suppressing a decrease in _{B r,} and the R-T-B-based sintered magnet having excellent _{H cJ} even at high temperatures is obtained. Although there are still unclear points about the mechanism that can obtain such an effect, the mechanism that the present inventors consider based on the knowledge obtained up to now will be described below. It should be noted that the following description of the mechanism is not intended to limit the technical scope of the present invention.

R-T-B based sintered magnet can be improved B _r by increasing the existence ratio of R _{2 T} 14 _B phase as the main phase. R ₂ T ₁₄ R amount in order to increase the existence ratio of B-phase, T amounts, although the B amount should brought close to the stoichiometric ratio of _R 2 _{T 14} B _phase, to form an R _{2 T 14} B phase When the amount of B is less than the stoichiometric ratio, a soft magnetic R ₂ T ₁₇ phase precipitates at the grain boundary, and H _cJ decreases rapidly. However, it is considered that when Ga is contained in the magnet composition, an R—T—Ga phase is generated instead of the R ₂ T ₁₇ phase, and a decrease in H _cJ can be prevented. Patent Document 1 is an invention based on this technical idea. By reducing the amount of B, an R ₂ T ₁₇ phase is positively generated, and the transition metal rich phase (R ₆ T ₁₃₎ is produced using the R ₂ T ₁₇ phase as a raw material. M = R-T-Ga phase). However, as a result of the study by the present inventors, the R—T—Ga phase also has a slight magnetism, and the R—T—B-based sintered magnet has a grain boundary, particularly R at the grain boundary that bears H _cJ. It is considered that the presence of a large amount of -T-Ga phase hinders the improvement of _HcJ .

Further, as described above, when the RH supply diffusion treatment as disclosed in Patent Documents 2 and 3 is applied to the R-T-B rare earth sintered magnet of Patent Document 1, H _k / H _cJ is significantly reduced. . This is considered to be due to the low amount of B contained in the two-grain grain boundary and the grain boundary triple point. That is, when RH is diffused into the sintered magnet material by the RH supply diffusion treatment, B plays some role. If the amount of B in the RTB-based sintered magnet material is low, the RH supply diffusion treatment is performed. It is thought that sometimes harmful phases (for example, R ₂ T ₁₇ phase) are generated, and as a result, H _k / H _cJ may be significantly reduced.

The RTB-based sintered magnet material obtained by the manufacturing method of the present invention includes a conventional RTB-based sintered magnet material (including R, B, Ga, Fe, etc., compared to the magnet of Patent Document 1). A secondary alloy powder containing Pr and Ti is mixed with a main alloy powder having substantially the same components and composition as the B content is high), and molded and sintered. The B amount of the main alloy powder is patented. It is relatively high compared to Document 1 (0.90 to 0.96% by mass). Therefore, the production amount of the R ₂ T ₁₇ phase is reduced, and accordingly, the production amount of the R—T—Ga phase is also reduced. As a result, since the content of relatively expensive Ga can be reduced, it becomes possible to provide an RTB-based sintered magnet at a low cost.

Further, in the RTB-based sintered magnet material, Ti contained in the suballoy powder is combined with B to produce TiB ₂ mainly at the grain boundary triple point. Since TiB ₂ is non-magnetic, it is _unlikely to hinder _HcJ improvement like the RT-Ga phase. As a result, even in the R-T-B system permanent magnet material (before the RH supply diffusion treatment), _HcJ as high as the R-T-B system rare earth sintered magnet of Patent Document 1 can be expressed.

Moreover, when the structure | tissue after heat processing of the R-T-B type | system | group sintered magnet raw material is observed, the thickness of a two-particle grain boundary is thick compared with the conventional R-T-B type | system | group sintered magnet material (distance between main phases). Is getting longer). This is considered to be due to the presence of TiB ₂ generated at the triple point of the grain boundary and a small amount of R—T—Ga phase generated mainly at the two grain boundary. The increase in the thickness of the two grain boundaries is also thought to contribute to the high expression of _HcJ .

In addition, in the RTB-based sintered magnet material, Pr contained in the secondary alloy powder is concentrated in the main phase outer shell. This improves _HcJ . Further, the Pr contained in the secondary alloy powder increases the amount of Pr contained in the two-grain grain boundary and the grain boundary triple point and increases the thickness of the two-grain grain boundary. Thus, it is considered that the fact that Pr is contained in the secondary alloy powder also contributes to the high expression of _HcJ .

Furthermore, since TiB ₂ is generated in the RTB-based sintered magnet material obtained by the manufacturing method of the present invention, two particles are formed in the same manner as the RTB-based rare earth sintered magnet of Patent Document 1. The amount of B contained in the grain boundary and the grain boundary triple point is considered to be low, but when RH diffuses into the sintered magnet material by the RH supply diffusion treatment, the B stored in TiB ₂ is somehow It is considered that the production of harmful phases (for example, R ₂ T ₁₇ phase) is suppressed. As a result, it is possible to suppress a decrease in _H k _{/ H cJ} by RH supply diffusion process in the R-T-B based sintered magnet obtained, higher while suppressing the decrease in _{B r H cJ} and high _H k / has a H _cJ, and excellent _{H cJ} at high temperatures be obtained.

  The manufacturing method of the RTB system sintered magnet of this invention is demonstrated below.

[Process for preparing main alloy powder]
In the step of preparing the main alloy powder, the components and composition of the main alloy powder are as follows.
R30.0 to 31.7% by mass (R is at least one of rare earth elements and must contain Nd),
B0.90-0.96 mass%,
Ga 0.15-0.4 mass%,
The remainder T (T is at least one of transition metal elements and must contain Fe) and unavoidable impurities.
In the component composition, the content of each element has a high H _cJ and high H _{k /} H _cJ while suppressing lowering of the lower limit less than or exceeds the upper limit B _r of the range, and excellent in high temperature An _RTB -based sintered magnet having _HcJ cannot be obtained.

  In addition to the above components, the main alloy powder includes known additive elements for the purpose of improving magnet characteristics, such as Co, Al, Cu, V, Cr, Mn, Nb, Ta, Mo, W, Ca, Sn, Zr, and Hf. You may contain at least 1 sort (s) of these. The main alloy powder may contain inevitable impurities such as La, Ce, Cr, Mn, and Si contained in raw materials such as didymium alloy (Nd—Pr), electrolytic iron, and ferroboron.

  In the step of preparing the main alloy powder, the raw materials of each element are weighed so as to have the above components and compositions, and are made into powder by a known production method. For example, an alloy is produced by a strip casting method, and the obtained alloy is made into a coarsely pulverized powder by a hydrogen pulverization method. Alternatively, the coarsely pulverized powder is finely pulverized by a jet mill pulverization method to obtain a finely pulverized powder. The main alloy powder may be either a coarsely pulverized powder or a finely pulverized powder.

[Step of preparing secondary alloy powder]
The secondary alloy powder contains Pr and Ti. Preferably, it contains Pr 53 to 66% by mass and Ti 5 to 21% by mass. More preferably, the balance contains Fe and Al. Have Pr and Ti content is lower than or higher _{H cJ} and high _H k _{/ H cJ} while suppressing lowering of exceeds the upper limit _{B r} of the range, and has excellent _{H cJ} even at high temperatures An RTB-based sintered magnet cannot be obtained. By containing Fe and Al, the secondary alloy can be easily melted and pulverized. The secondary alloy powder is not limited to a single alloy powder (for example, PrTiAlFe alloy), but, for example, a mixed powder of a plurality of alloys (for example, a mixed powder of a PrTiFe alloy and a PrTiAlFe alloy) or a single or a plurality of alloys. Alternatively, a powder obtained by mixing a metal powder or a compound powder (for example, a mixed powder of a PrTiAlFe alloy and a Ti compound powder) may be used.

  In the step of preparing the suballoy powder, the raw materials of each element are weighed so as to have the above components and compositions, and are made into powder by a known production method. For example, a ribbon-like alloy is produced by a rapid quenching method, and the obtained ribbon-like alloy is pulverized by a known pulverizing means to form a powder.

[Process for preparing mixed alloy powder]
The main alloy powder and the sub-alloy powder prepared as described above are mixed so that Ti contained in 100% by mass of the mixed alloy powder after mixing is 0.3% by mass or less to obtain a mixed alloy powder. When Ti is contained in the mixed alloy powder 100 mass% after mixing it exceeds 0.3 wt% has a high _{H cJ} and high _H k _{/ H cJ} while suppressing a decrease in _{B r,} excellent even at high temperatures In addition, it becomes impossible to obtain an _RTB -based sintered magnet having _HcJ . Mixing is performed by a known mixing means. Mixing may be either dry or wet. When the main alloy powder is coarsely pulverized powder, it is mixed with the secondary alloy powder to form a mixed alloy powder, and the mixed alloy powder is finely pulverized and then molded. When the main alloy powder is a finely pulverized powder, it is mixed with the sub-alloy powder to form a mixed alloy powder and then molded.

[Process for preparing molded body]
The mixed alloy powder is formed into a formed body. Molding is performed by known molding means.

[Step of preparing an RTB-based sintered magnet material]
The molded body is sintered to obtain an RTB-based sintered magnet material (sintered body). Sintering is performed by a known sintering means.

[Step of preparing RH diffusion source]
For the step of preparing an RH diffusion source made of a metal, an alloy or a compound containing Dy or Tb, the steps disclosed in the well-known RH supply diffusion process such as Patent Documents 2 and 3 can be applied.

[Step of performing RH supply diffusion treatment]
The process of supplying and diffusing Dy or Tb of the RH diffusion source to the R-T-B system sintered magnet material is disclosed in known RH supply diffusion processes such as Patent Documents 2 and 3 above. A process can be applied. The RH supply diffusion treatment may be a method of diffusing the heavy rare earth element RH from the RH diffusion source to the surface of the R-T-B system sintered magnet material as in Patent Documents 2 and 3. , RH-containing metals, alloys, compounds, etc. are pre-existed on the surface of the RTB-based sintered magnet material by film formation or application, and then diffused into the RTB-based sintered magnet material by heat treatment It is also possible to make it.

For the purpose of further diffusing Dy or Tb supplied to the inside of the RTB-based sintered magnet by the RH supply diffusion process, an RH diffusion process described below may be performed. In the RH diffusion process, after the RH supply diffusion process is performed, heating is performed without supplying Dy or Tb from the RH diffusion source. For example, when the RH diffusion process is performed after the RH supply diffusion process, the atmospheric pressure is set such that Dy or Tb is not supplied from the RH supply source, preferably 700 ° C. or more and 1000 ° C. or less, more preferably 800 ° C. or more and 950. Carry out at ℃ or below. Alternatively, after performing the RH supply diffusion treatment, when only the RTB-based sintered magnet is recovered, a vacuum or an inert gas atmosphere below the atmospheric pressure with respect to the RTB-based sintered magnet Among them, it is preferably performed at 700 ° C. or higher and 1000 ° C. or lower, more preferably 800 ° C. or higher and 950 ° C. or lower. The treatment time is, for example, about 10 minutes to 24 hours, more preferably about 1 hour to 6 hours. Due to the RH diffusion treatment, Dy or Tb is diffused in the RTB-based sintered magnet, and Dy or Tb supplied in the vicinity of the surface layer is further diffused deeply, so that _HcJ can be increased as a whole magnet.

[Process for heat treatment]
In the step of heat-treating the R-T-B system sintered magnet after the RH supply diffusion treatment step (the RH diffusion step may be carried out after the RH supply diffusion treatment step), the heat treatment temperature, time, atmosphere, etc. are known. Conditions can be applied. For example, heat treatment is performed at 480 to 540 ° C. for about 1 to 10 hours in vacuum or Ar gas. By this heat treatment, the thickness of the two-grain grain boundary is increased, and an _RTB -based sintered magnet having high _HcJ can be obtained.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1
The raw materials of each element were weighed so as to have the alloy components and compositions shown in A to D of Table 1, and an alloy was produced by a strip casting method. Each of the obtained alloys was made into a coarsely pulverized powder by a hydrogen pulverization method and then finely pulverized by a jet mill pulverization method to obtain a particle diameter D50 (volume center value obtained by a laser diffraction method by an airflow dispersion method, the same applies hereinafter). 4.2 μm main alloy powders A to D were prepared.

  The raw materials of each element were weighed so as to have the alloy components and compositions shown in Table 2, a, b and c, and a ribbon-like alloy was produced by a super rapid cooling method. The obtained ribbon-like alloys were pulverized in a mortar and then sieved to prepare sub-alloy powders a, b, and c of 38 μm under.

  The prepared main alloy powders A to C and suballoy powders a to c were mixed so as to have the components and compositions shown in Table 3. 1 to 11 mixed alloy powders were prepared. In addition, the symbols A to D in the main alloy powder of Table 3 indicate the alloys used, and the parentheses indicate the mixing ratio (% by mass). Similarly, symbols a to c in the secondary alloy powder indicate the alloy used, and the parentheses indicate the mixing ratio (mass%).

Sample No. After forming two of the mixed alloy powders 1 to 11 at a pressure of 49 MPa (0.5 ton / cm ² ) with a perpendicular magnetic field molding device (transverse magnetic field molding device), the resulting molded body was made into each component and composition. Depending on the case, the sample was sintered at 1000 to 1040 ° C. for 4 hours. Two R-T-B system sintered magnet materials (hereinafter referred to as “R-T-B system sintered magnet materials of sample No. **”) based on the mixed alloy powders 1 to 11 were prepared.

Sample No. In order to measure the magnet characteristics of 1 to 11 R-T-B system sintered magnet material, one of each two was subjected to heat treatment at a temperature of 880 ° C. for 3 hours in a vacuum atmosphere, and after cooling, Heat treatment was performed in a vacuum atmosphere at 480 to 540 ° C. for 2 hours depending on the components and composition of the R-T-B system sintered magnet material. The obtained sample No. Magnet characteristics of 1 to 11 RTB-based sintered magnet materials were measured with a BH tracer. The measurement results are shown in FIGS. Figure 1 is the horizontal axis the amount of Ti, the vertical axis indicates the measurement result of H _cJ, 2 weight abscissa Ti, the vertical axis indicates the measurement results of B _r, 3 horizontal axis Ti amount, vertical An axis _| shaft shows the measurement result of Hk / H _cJ . Note that in Hk _{/ H cJ,} the _{H k} is J second quadrant (magnetization magnitude) -H (field strength) curve, J is 0.9 J _{r (J r} residual magnetization) becomes a value The value of the position H (the same applies hereinafter). In FIG. 1 to FIG. 1 to 3 and rhombus plots are sample Nos. 4 to 7 and the round plot is Sample No. 8-10, the square plot is sample No. 11 is shown.

As shown in FIG. 1, the RTB-based sintered magnet material (example of the present invention) obtained by mixing, forming, sintering, and heat-treating the suballoy powder containing Pr and Ti with the main alloy powder is the suballoy powder. It can be seen that _HcJ is greatly improved as compared with the case where no is added (comparative example). This is because, as described above, Ti contained in the _suballoy powder is combined with B and nonmagnetic TiB ₂ is formed mainly at the grain boundary triple point, which hinders the improvement of _HcJ as in the R-T-Ga phase. In addition, TiB ₂ produced at the grain boundary triple point, a small amount of R—T—Ga phase produced mainly at the two-grain grain boundary, and Pr contained in the secondary alloy powder. This is presumably because the amount of Pr contained in the two-grain grain boundary and the grain boundary triple point increases due to the thickness of the two-grain grain boundary.

Further, as shown in FIG. 2, R-T-B based sintered magnet material according to the present invention is not so large reduction in B _r for enhancing the effect of H _cJ although B _r drops. That, _{H cJ} is improved while suppressing a decrease in _{B r.} Further, as shown in FIG. 3, H _k / H _cj has a high value exceeding 0.95 in any sample.

Sample No. 11 is a reproduction example of Patent Document 1, and the amount of B is lower than other samples (0.88% by mass). Sample No. 11, an R ₂ T ₁₇ phase is generated due to a low B amount during alloy melting or sintering by the strip casting method, and the transition metal rich phase (R ₆ T) is produced using the R ₂ T ₁₇ phase as a raw material. ₁₃ M = R-T-Ga phase) is considered to be produced in large quantities. As shown in FIG. The _HcJ of 11 is lower than that of the present invention. This is _presumably because a large amount of the RT-Ga phase hinders the improvement of _HcJ .

  Next, plate-like Dy metal as the RH diffusion source, and sample No. 1 to 11 of R-T-B system sintered magnet materials are prepared, and for each R-T-B system sintered magnet material, an RH diffusion source and a holding member are formed on the Mo plate. 11 types of laminates were prepared by laminating in the order of R-T-B system sintered magnet material, holding member, and RH diffusion source. The holding member was a plain weave wire mesh made of Mo. The 11 types of laminates were charged into a heat treatment furnace and subjected to RH supply diffusion treatment at a temperature of 880 ° C. for 5.5 hours in a vacuum atmosphere at a pressure of 0.1 Pa. Thereafter, the inside of the furnace was cooled, and sample No. 1 to 11 R-T-B-based sintered magnets obtained by subjecting R-T-B-based sintered magnet materials to RH supply diffusion treatment (hereinafter referred to as "Sample No. ** R-T-B based sintered magnets"). "). Sample No. after RH supply diffusion treatment 1 to 11 R-T-B system sintered magnets were subjected to RH diffusion treatment at a temperature of 880 ° C. for 5 hours in a vacuum atmosphere, and after cooling, depending on the components and composition of the R-T-B system sintered magnets Then, heat treatment was performed in a vacuum atmosphere at 480 to 540 ° C. for 2 hours.

The obtained sample No. 1 to 11 each of the R-T-B system sintered magnets are ground on both sides by 0.1 mm, and further from the center of each R-T-B system sintered magnet, the thickness is 3.0 mm × width 7 mm × length. A 7 mm test piece was cut out. The magnet properties of the specimen were measured with a pulse BH tracer. The measurement results are shown in FIGS. Figure 4 is the horizontal axis the amount of Ti, the vertical axis indicates the measurement result of H _cJ, 5 the horizontal axis the amount of Ti, the vertical axis represents the measured results of the B _r, 6 horizontal axis Ti amount, vertical An axis _| shaft shows the measurement result of Hk / H _cJ . In FIG. 4 to FIG. 1 to 3 and rhombus plots are sample Nos. 4 to 7 and the round plot is Sample No. 8-10, the square plot is sample No. 11 is shown.

As shown in FIG. 4, R—T—B-based sintered magnet material obtained by mixing, forming, sintering, and heat-treating sub-alloy powder containing Pr and Ti to main alloy powder is subjected to RH supply diffusion treatment. It can be seen that the _TB sintered magnet (example of the present invention) has a high _HcJ as compared with the one not mixed with the secondary alloy powder (comparative example). Further, as shown in FIGS. 5 and 6, are also suppressed decrease in _{B r} and Hk _{/ H cJ} after RH supply diffusion process, it is found to have a high _{B r} and a high Hk _{/ H cJ} . As described above, when RH diffuses into the sintered magnet material by the RH supply diffusion process, B stored in TiB ₂ plays a role and generates a harmful phase (for example, R ₂ T ₁₇ phase). This is thought to be due to suppression.

On the other hand, Hk / H _cJ is lowered in the _case where the _suballoy powder is not added (comparative example), and in particular, Sample No. _{No. 11} has a significantly reduced Hk / H _cJ as compared to before RH supply diffusion. This is considered to be due to the low amount of B contained in the two-grain grain boundaries and the grain boundary triple points, because a harmful phase (for example, R ₂ T ₁₇ phase) was generated during the RH supply diffusion treatment. It is believed that there is.

Moreover, as shown in FIGS. 4-6, in the RTB type | system | group sintered magnet by this invention, the direction with smaller Ga content (Ga0.2 mass%, the round plot in FIGS. 4-6) is. High magnet characteristics are obtained. That is, since the content of relatively expensive Ga can be reduced, it is possible to provide an RTB-based sintered magnet at a low cost. As described above, this is because the amount of B in the main alloy powder is relatively high (0.93% by mass), so that the amount of R ₂ T ₁₇ phase generated is reduced, and accordingly, the improvement of H _cJ is hindered. The amount of Ga phase generated is also reduced. As a result, it is considered that high magnet characteristics can be obtained even when the Ga content is low.

  Sample No. About the 8-11 RTB system sintered magnet, the magnet characteristic in 140 degreeC was measured with the BH tracer. Table 4 shows the measurement results.

As shown in Table 4, the RTB-based sintered magnets (sample Nos. 9 and 10) according to the present invention are those to which no secondary alloy powder is added (sample No. 8), as well as reproduction examples of the patent document 1 (samples). It can be seen that it has excellent _HcJ even at high temperatures compared to No. 11).

Sample No. Observation of the structures of the 1 to 4 and 6 to 11 RTB-based sintered magnets was performed using a reflected electron image (BSE image) using an FE-SEM (field emission scanning electron microscope). The results are shown in FIGS. FIG. 1 to 3 (characteristic components, composition: B0.90 mass%, Ga 0.4 mass%, Ti0, 0.14, 0.20 mass%), FIG. 4, 6, 7 (characteristic components, composition is B0.93% by mass, Ga0.4% by mass, Ti0, 0.11, 0.22% by mass), FIG. 8-10 (characteristic component, composition is B0.93% by mass, Ga0.2% by mass, Ti0, 0.13, 0.22% by mass), FIG. 11 (characteristic component, composition is B 0.88 mass%, Ga 0.4 mass%, Ti 0 mass%). The crystal indicated by the arrow in each figure is TiB ₂ . The crystal indicated by the arrow was subjected to composition analysis by EDS (energy dispersive X-ray spectroscopy). As a result, only Ti and B coexisted, and thus it was estimated to be TiB ₂ .

As is apparent from FIGS. 7 to 9, RH is supplied to an R-T-B system sintered magnet material obtained by mixing, molding, sintering and heat-treating a sub-alloy powder containing Pr and Ti to the main alloy powder according to the present invention. In the RTB sintered magnet (sample No. _2, 3, 6, 7, 9, 10) subjected to the diffusion treatment, TiB ₂ is generated at the triple point of the grain boundary, and the secondary alloy powder is mixed. It can be seen that the thickness of the two-particle grain boundary is thicker than those not (sample Nos. 1, 4, 8).

Sample No. 1 which is a reproduction example of Patent Document 1 shown in FIG. In FIG. 11, the thickness of the two-particle grain boundary is thick, but as shown in FIG. 4, excellent _HcJ is not obtained as in the present invention. This is considered that there are many RT-Ga phases in the two-grain grain boundary, which hinders the improvement of _HcJ . Further, as shown in FIGS. 3 and 6, H _k / H _cJ is significantly reduced as compared to before RH supply diffusion. This is because the amount of B is small (0.88% by mass), and the amount of B contained in the two-grain grain boundaries and the grain boundary triple points is low, and therefore a harmful phase (for example, R ₂ T ₁₇ phase) during the RH supply diffusion treatment. Is considered to have been generated.

  Sample No. About the RTB type | system | group sintered magnet of 6, Pr density | concentration distribution was investigated using the EPMA apparatus. The result is shown in FIG. In FIG. 11, the dark and light portion (white portion) of the black and white image has a high Pr concentration, the dark portion (black portion) has a low Pr concentration, and the dark portion between the two portions (gray portion) has Pr. Indicates that the concentration is between them. In FIG. 11, the main phase is in the form of black particles, and the gray portion or white portion between the main phases is the grain boundary (two-particle grain boundary and grain boundary triple point). As is apparent from FIG. 11, it can be seen that the Pr concentration at the two-grain grain boundary and the grain boundary triple point is high. In addition, it can be seen that each main phase is black in the center and dark gray in the outer shell, and Pr is concentrated in the outer shell.

FIG. 6 (using a secondary alloy powder containing Pr 59.0% by mass and Ti 12.0% by mass), and using TiH ₂ as the secondary alloy powder, the amount of Ti in the composition and composition of the mixed alloy powder is 0.1% by mass ( Sample No. of Example 1 was mixed except that the mixture was mixed so that it was 0.3% by mass (Comparative Example B). 6 is a result of structural observation of an R-T-B sintered magnet obtained by the same method as in FIG. The photograph on the left side of FIG. 6 (invention example), the middle photo is Comparative Example i, and the right photo is Comparative Example B. Sample No. No. 6 (invention example) and Comparative Example A have substantially the same amount of Ti to be mixed as a sub-alloy powder, and the presence or absence of Pr amount is different. Comparative Example A and Comparative Example B do not contain Pr in the sub-alloy powder. Ti amount is different.

As can be seen from FIG. In the case of No. 6 and Comparative Example B, the two-grain grain boundary is clearer and the grain boundary thickness is thicker. That is, sample no. In No. 6, since the Ti amount is almost the same as in Comparative Example A, and the presence or absence of Pr is different, the grain boundary becomes thick due to the presence of Pr. On the other hand, Comparative Example B differs from Comparative Example A only in the amount of Ti, so that the grain boundary becomes thicker due to the increase in Ti amount, that is, the increase in TiB ₂ . That is, in the present invention, the two effects are mainly due to the synergistic effect due to TiB ₂ generated at the grain boundary triple point and the presence of Pr (the amount of Pr contained in the two-grain grain boundary and the grain boundary triple point increases). It is considered that the grain boundary thickness is thick, which is considered to contribute to the high expression of _HcJ .

As described above, according to the present invention, while suppressing the decrease in _{B r} has a high _{H cJ} and high _H k _{/ H cJ,} and the R-T-B-based sintered with excellent _{H cJ} even at high temperatures A magnetized magnet can be provided.

Example 2
In this example, the main alloy powder does not contain Pr. Raw materials of each element were weighed so as to have the alloy components and compositions shown in E and F of Table 5, and an alloy was produced by a strip casting method. Each of the obtained alloys was made into a coarsely pulverized powder by a hydrogen pulverization method, and then finely pulverized by a jet mill pulverization method to prepare main alloy powders E and F having a particle diameter D50 of 4.2 μm. In addition, suballoy powders b and c were prepared in the same manner as in Table 2 of Example 1.

  The prepared main alloy powders E and F and suballoy powders b and c were mixed so as to have the components and compositions shown in Table 6. 12-19 mixed alloy powders were prepared. In addition, the symbols E and F in the main alloy powder of Table 6 indicate the alloys used, and the parentheses indicate the mixing ratio (% by mass). Similarly, symbols b and c in the secondary alloy powder indicate the alloy used, and the parentheses indicate the mixing ratio (% by mass).

Sample No. After forming two of the mixed alloy powders of 12 to 19 at a pressure of 49 MPa (0.5 ton / cm ² ) with a perpendicular magnetic field molding device (transverse magnetic field molding device), the resulting molded body was made into each component and composition. Depending on the case, the sample was sintered at 1000 to 1040 ° C. for 4 hours. Two RTB-based sintered magnet materials (hereinafter referred to as “RTB-based sintered magnet materials of sample No. **”) based on 12 to 19 mixed alloy powders were prepared.

Sample No. In order to measure the magnet characteristics of 12 to 19 RTB-based sintered magnet materials, one of each of the two was subjected to a heat treatment at a temperature of 880 ° C. for 3 hours in a vacuum atmosphere, and after cooling, Heat treatment was performed in a vacuum atmosphere at 480 to 540 ° C. for 2 hours depending on the components and composition of the R-T-B system sintered magnet material. The obtained sample No. The magnet characteristics of 12-19 RTB-based sintered magnet materials were measured with a BH tracer. The measurement results are shown in FIGS. Figure 13 is the horizontal axis the amount of Ti, the vertical axis indicates the measurement result of H _cJ, 14 weight abscissa Ti, the vertical axis indicates the measurement results of B _r, 15 horizontal axis Ti amount, vertical An axis _| shaft shows the measurement result of Hk / H _cJ . In FIG. 13 to FIG. 12-15, the round plot is sample No. 16-19 are shown.

As shown in FIG. 13, the RTB-based sintered magnet material (example of the present invention) obtained by mixing, molding, sintering, and heat-treating a sub-alloy powder containing Pr and Ti to a main alloy powder not containing Pr It can be seen that _HcJ is improved as compared with the case where no _suballoy powder is added (comparative example).

Further, as shown in FIG. 14, R-T-B based sintered magnet material according to the present invention is not so large reduction in B _r for enhancing the effect of H _cJ although B _r drops. That, _{H cJ} is improved while suppressing a decrease in _{B r.} Further, as shown in FIG. 15, H _k / H _cj has a high value exceeding 0.97 in any sample.

  Next, plate-like Dy metal as the RH diffusion source, and sample No. 1 to 2 of 19 to 19 R-T-B system sintered magnet materials are prepared, and for each R-T-B system sintered magnet material, an RH diffusion source and a holding member are formed on the Mo plate. Eight types of laminates were prepared by laminating in order of the R-T-B sintered magnet material, the holding member, and the RH diffusion source. The holding member was a plain weave wire mesh made of Mo. The eight types of laminates were charged into a heat treatment furnace and subjected to RH supply diffusion treatment at a temperature of 880 ° C. for 5.5 hours in a vacuum atmosphere at a pressure of 0.1 Pa. Thereafter, the inside of the furnace was cooled, and sample No. 12-19 R-T-B system sintered magnet materials subjected to RH supply diffusion treatment (hereinafter referred to as “Sample No. ** R-T-B system sintered magnet) "). Sample No. after RH supply diffusion treatment 12-19 R-T-B system sintered magnets were subjected to RH diffusion treatment at a temperature of 880 ° C. for 5 hours in a vacuum atmosphere, and after cooling, depending on the components and composition of the R-T-B system sintered magnets Then, heat treatment was performed in a vacuum atmosphere at 480 to 540 ° C. for 2 hours.

The obtained sample No. Both surfaces of 12 to 19 R-T-B system sintered magnets are ground by 0.1 mm each, and further, a thickness of 3.0 mm × width 7 mm × length from the center of each R-T-B system sintered magnet A 7 mm test piece was cut out. The magnet properties of the specimen were measured with a pulse BH tracer. The measurement results are shown in FIGS. Figure 16 is the horizontal axis the amount of Ti, the vertical axis indicates the measurement result of H _cJ, 17 horizontal axis Ti amount, and the vertical axis represents the measured results of the B _r, 18 horizontal axis Ti amount, vertical An axis _| shaft shows the measurement result of Hk / H _cJ . In FIG. 16 to FIG. 12-15, the round plot is sample No. 16-19 are shown.

As shown in FIG. 16, the RH supply diffusion treatment is applied to the RTB-based sintered magnet material obtained by mixing, molding, sintering, and heat-treating the sub-alloy powder containing Pr and Ti to the main alloy powder not containing Pr. It can be seen that the _{applied RTB} -based sintered magnet (example of the present invention) has a high _HcJ as compared with the one not mixed with the secondary alloy powder (comparative example). Further, as shown in FIGS. 17 and 18, are also suppressed decrease in _{B r} and Hk _{/ H cJ} after RH supply diffusion process, it is found to have a high _{B r} and a high Hk _{/ H cJ} .

Moreover, as shown in FIGS. 16-18, in the RTB type | system | group sintered magnet by this invention, the direction with smaller Ga content (Ga0.2 mass%, the round plot in FIGS. 16-18) is. High magnet characteristics (particularly B _r ) are obtained. That is, since the content of relatively expensive Ga can be reduced, it is possible to provide an RTB-based sintered magnet at a low cost.

  Sample No. About the 16-19 R-T-B system sintered magnet, the magnet characteristic in 140 degreeC was measured with the BH tracer. Table 7 shows the measurement results.

As shown in Table 7, the RTB-based sintered magnets according to the present invention (Sample Nos. 17 to 19) were superior even at high temperatures compared to those without the addition of the secondary alloy powder (Sample No. 16). It can be seen that it has H _cJ .

As described above, in the case of not containing Pr in the main alloy powder, as in the case of containing the Pr in the main alloy powder of Example 1, while suppressing the decrease in B _r high H _cJ and high H _{k /} H _{cJ And} an _RTB -based sintered magnet having excellent _HcJ even at high temperatures.

  The RTB-based sintered magnet obtained by the present invention is suitably used for various motors such as voice coil motors (VCM) for hard disk drives, motors for electric vehicles, motors for hybrid vehicles, and home appliances. be able to.

Claims (3)

R30.0 to 31.7% by mass (R is at least one of rare earth elements and must contain Nd),
B0.90-0.96 mass%,
Ga 0.15-0.4 mass%,
Preparing a main alloy powder containing the balance T (T is at least one of transition metal elements and necessarily contains Fe) and inevitable impurities;
Preparing a sub-alloy powder containing Pr and Ti;
Mixing the main alloy powder and the sub-alloy powder so that Ti contained in 100% by mass of the mixed alloy powder after mixing is 0.3% by mass or less, and preparing a mixed alloy powder;
Forming a mixed alloy powder and preparing a formed body; and
Sintering the compact and preparing an R-T-B sintered magnet material;
Providing an RH diffusion source comprising a metal, alloy or compound containing Dy or Tb;
Supplying RH diffusion source Dy or Tb to the R-T-B system sintered magnet material, and performing an RH supply diffusion treatment;
A step of heat-treating the RTB-based sintered magnet after the RH supply diffusion treatment step;
The manufacturing method of the RTB type | system | group sintered magnet characterized by including.   The method for producing an RTB-based sintered magnet according to claim 1, wherein the suballoy powder contains Pr 53 to 66 mass% and Ti 5 to 21 mass%.   The method for producing an RTB-based sintered magnet according to claim 1 or 2, wherein the sub-alloy powder contains Fe and Al.