JP5408521B2 - Manufacturing method of sintered magnet - Google Patents

Description

The present invention relates to a sintered magnet you containing ferrite having a M-type magnetoplumbite structure as a main phase.

Ferrite is a general term for compounds formed by divalent metal oxides and trivalent iron oxides. Ferrite magnets are used in various applications such as various rotating machines, generators, and speakers. As a material of the ferrite magnet, Sr ferrite (SrFe ₁₂ O ₁₉ ) and Ba ferrite (BaFe ₁₂ O ₁₉ ) having a hexagonal magnetoplumbite structure are widely used. These ferrites are produced at a relatively low cost by powder metallurgy using iron oxide and carbonate such as strontium (Sr) or barium (Ba) as raw materials.

Recently, by replacing part of the Sr in the above Sr ferrite rare earth element such as La, by substituting a part of Fe with Co, it is proposed to improve the coercive force H _cJ and remanence B _r (Patent Document 1, Patent Document 2).

  Sr ferrite (hereinafter referred to as “SrLaCo ferrite”) in which a part of Sr is replaced with a rare earth element such as La and a part of Fe is replaced with Co or the like according to Patent Documents 1 and 2 has excellent magnet characteristics. Therefore, they are being widely used in various applications in place of conventional Sr ferrite and Ba ferrite.

  On the other hand, as in the case of the above Sr ferrite, it has been proposed to substitute a part of Ca with a rare earth element such as La and a part of Fe with Co or the like in the Ca ferrite (Patent Document 3). ).

It is known that Ca ferrite has a stable structure of CaO—Fe ₂ O ₃ or CaO-2Fe ₂ O ₃ and forms hexagonal ferrite by adding La. However, the obtained magnet characteristics are similar to those of the conventional Ba ferrite and are not sufficiently high. Therefore, Patent Document 3 _discloses a Ca ferrite containing La and Co simultaneously (hereinafter referred to as “CaLaCo ferrite” in order to improve the residual magnetic flux density B _r , the coercive force H _cJ , and the temperature characteristics of the coercive force H _cJ. ").

In the CaLaCo ferrite Patent Document 3 discloses, by replacing part of Ca with rare earth elements such as La, and by substituting a part of Fe Co, etc., for the anisotropic magnetic field _{H A} can, Sr It has been reported that a value of 20 kOe or more, which is 10% or more higher than the anisotropic magnetic field _{HA of} ferrite, can be obtained.

However, the CaLaCo ferrite according to Patent Document 3 has characteristics that exceed the SrLaCo ferrite in the anisotropic magnetic field _HA , and B _r and H _cJ have characteristics comparable to the SrLaCo ferrite, but the squareness ratio is very poor, It cannot satisfy both high coercive force and high squareness ratio, and has not yet been applied to various uses such as motors.

Applicant, CaLaCo ferrite was noticed that an anisotropic magnetic field _{H A} in excess of SrLaCo ferrite. And as a result of earnest research on high performance of CaLaCo ferrite, in CaLaCo ferrite, the optimal region for the amount of molar ratio x of R (such as La), the amount of molar ratio y of M (such as Co), and the value of n In addition, by including R and M so that x and y have a specific ratio, an oxide magnetic material having a high B _r , a high H _cJ and a high squareness ratio can be obtained. It was found that it was obtained and proposed previously (Patent Document 4).
JP-A-10-149910 JP-A-11-154604 JP 2000-223307 A JP 2006-104050 A

  Although the CaLaCo ferrite according to Patent Document 4 has high magnet properties, the demand for higher performance from users has become increasingly severe, and further improvements in magnet properties are required.

The present invention differs from the conventional CaLaCo ferrite satisfying both high B _r and high H _cJ, and an object thereof is to provide a high-performance sintered magnet new.

  The above object is achieved by any of the following configurations.

(1) represented by the composition formula (1-x) CaO. (X / 2) R ₂ O _3. (Ny / 2) Fe ₂ O ₃ .yMO, where R is selected from La, Nd, and Pr At least one element selected from the group consisting of La, M is at least one element selected from Co, Zn, Ni, and Mn and must contain Co, and x, y, and n representing the molar ratio are Each,
0.45 ≦ x ≦ 0.7,
0.35 <y ≦ 0.55,
4.9 ≦ n ≦ 5.8
And an oxide magnetic material having a composition satisfying a relational expression of 1.2 ≦ x / y ≦ 1.65 and having a main phase of ferrite having a hexagonal M-type magnetoplumbite structure. , remanence _{B r} (unit: mT) at 2 3 ° C. and intrinsic coercive force _{H cJ} (unit: kA / m) and is, satisfies the relationship _{B r ≧ 450, B r +} H cJ / 4 ≧ 559 baked A method for producing a magnet , comprising:
Mixing and mixing raw material powders to obtain mixed raw material powders,
Calcining the mixed raw material powder to obtain a calcined body,
Pulverizing the calcined body to obtain fine particles,
Press molding the fine particles to obtain a molded body,
It comprises a sintering step of sintering the molded body to obtain a sintered magnet,
The manufacturing method of the sintered magnet whose said pulverization process is 1 time and whose sintering temperature in the said sintering process is 1150 degreeC-1250 degreeC .

(2) calcining step before beauty / or temporary method for producing a sintered magnet heating step after the addition of _H 3 BO ₃ 0.3 wt% or less (1).

According to the present invention, it is possible to provide a sintered magnet as compared with the conventional CaLaCo ferrite satisfying both high B _r and high H _cJ.

In the sintered magnet according to the present invention, the residual magnetic flux density B _r (unit: mT) and the intrinsic coercive force H _cJ (unit: kA / m) have a relationship of B _r ≧ 450 and B _r + H _cJ / 4 ≧ 559. It has extremely excellent magnet properties that satisfy the requirements, and is therefore optimal for various applications such as various rotating machines, generators, and speakers.

The oxide magnetic material according to the present invention is represented by the following formula.
Composition formula (1-x) CaO. (X / 2) R ₂ O _3. (N−y / 2) Fe ₂ O ₃ .yMO

The present inventor has intensively studied on further enhancement of the performance of the CaLaCo ferrite according to Patent Document 4. As a result, the CaLaCo ferrite represented by the composition formula _{(1-x) CaO · (} x / 2) R 2 O 3 · (n-y / 2) Fe 2 O 3 · yMO, and further the residual magnetic flux density _{B r} It has been found that there is an optimum composition range that can improve the intrinsic coercive force _HcJ .

That is, the oxide magnetic material is contained by setting x of the oxide magnetic material to 0.45 to 0.7 and y exceeding 0.35, which is larger than the range of Patent Document 4, to 0.55 or less. Magnet characteristics satisfying both high B _r and high H _cJ are obtained in the sintered magnet, and in a preferred embodiment of the present invention, the residual magnetic flux density B _{r at} 23 ° C. exceeds the maximum characteristics described in Patent Document 4. A sintered magnet having extremely excellent magnet characteristics in which (unit: mT) and intrinsic coercive force H _cJ (unit: kA / m) satisfy the relationship of B _r ≧ 450 and B _r + H _cJ / 4 ≧ 559. It was found that it can be obtained.

The present invention relates to an improvement of CaLaCo ferrite, and Ca is an essential element . S Ru Ca is used only as r and instead of Ba.

  R is at least one element selected from La, Nd, and Pr, and must contain La. Even rare earth elements other than those described above can be allowed to be mixed as inevitable impurities.

  M is at least one element selected from Co, Zn, Ni, and Mn, and must contain Co. Even elements other than the above can be allowed to be mixed as inevitable impurities.

In the present invention, as described above, a part of Co can be substituted with Zn, Ni, and Mn. In particular, by replacing part of Co with Ni and Mn, the manufacturing cost can be reduced without deteriorating the magnet characteristics. Moreover, when replacing a part of Co in _{Zn, H cJ} is slightly lowered, thereby improving the _{B r.} The substitution amount of Zn, Ni, and Mn is 50% or less of Co in molar ratio.

x represents the content of R, and 0.45 ≦ x ≦ 0.7 is preferable. x is because more than 0.45 and less than 0.7 when _{B r} and squareness ratio decreases.

y represents the content of M, and 0.35 <y ≦ 0.55 is preferable. As described above, in Patent Document 4 previously proposed by the present applicant, it was considered that the preferable range of y is optimally 0.2 to 0.35. However the content exceeds 0.35 y, when optimizing the x / y is the ratio of x and y as described later, the B _r with little lowering, can be further improved intrinsic coercive force H _cJ I found. y is not possible to obtain a high _{B r} and _{H cJ} is 0.35 or less is not preferable because _{the H cJ} is reduced when it exceeds 0.55.

_CaO, n value defines the ratio of the R 2 _{O 3} and _Fe 2 _O 3, MO is preferably 4.9 ≦ n ≦ 5.8. Further, x / y, which is the ratio of x and y, is preferably 1.2 ≦ x / y ≦ 1.65 as shown in Examples described later. The range of x / y is different from that of Patent Document 4 previously proposed by the present applicant, like the range of y. When the n value and x / y are in the above ranges, and x and y are in the above preferable ranges, the residual magnetic flux density B _r (unit: mT) and the intrinsic coercive force H _cJ (unit: kA / m) at 23 ° C. ), A sintered magnet having extremely excellent magnetic characteristics satisfying the relationship of B _r ≧ 450 and B _r + H _cJ / 4 ≧ 559 can be obtained.

In the present invention, the target value of the magnet characteristics is such that the residual magnetic flux density B _r (unit: mT) and the intrinsic coercive force H _cJ (unit: kA / m) at 23 ° C. are B _r ≧ 450, B _r + H. _cJ / 4 to that to satisfy the relationship of ≧ 559 as an indicator capable of satisfying both high _{B r} and high _{H cJ,} B r 450 mT with a lower limit on, when _{H cJ} is 437.7kA / m of _{B r} is 450 mT (5.5 kOe) or more, _{B r} is due to the fact _{that H cJ} when 460mT was targeted to 397.9kA / m (5.0kOe) higher than levels. Of course, the above-mentioned magnet characteristics are not achieved in Patent Document 4 described above.

  Next, the manufacturing method of the oxide magnetic material of this invention is demonstrated.

First, raw material powders such as CaCO ₃ , Fe ₂ O ₃ , La ₂ O ₃ , and Co ₃ O ₄ are prepared. Based on the above-described composition formula, the prepared powder is blended so that x, y, and n are each in a preferable range. In addition to the oxide and carbonate, the raw material powder may be hydroxide, nitrate, chloride or the like, or may be in a solution state, regardless of the valence. In the production of a sintered _magnet, the raw material powder other than CaCO _{3, Fe} 2 _O 3 and _La 2 _{O 3} may be previously added from the time of the raw material mixture, is added after calcination to be described later Also good. For example, CaCO ₃ , Fe ₂ O ₃ , La ₂ O ₃ may be blended, mixed, and calcined, then Co ₃ O _{4 and the} like may be added and pulverized, and then molded and sintered. Moreover, in order to promote the reactivity at the time of calcination, about 1 mass% of compounds containing B ₂ O ₃ , H ₃ BO _3, etc. may be added as necessary.

In particular the addition of _H 3 BO _{3 is} effective in improving the _{H cJ} and _{B r.} The amount of H ₃ BO ₃ added is preferably 0.3% by mass or less. The most preferable value of the addition amount is around 0.2% by mass. When the amount of H ₃ BO ₃ to less than 0.1 wt%, not obtained the effect of improving the _{B r,} it is not preferable to lower the _{B r} when more than 0.3 mass%. Since H ₃ BO ₃ also has effects such as control of crystal grains during sintering, it is also effective to add it after calcination (before fine pulverization or before sintering). It can also be added both later.

  The raw material powder may be blended either wet or dry. When the raw material powder is stirred together with a medium such as a steel ball, it can be mixed more uniformly. In the case of wet, water is used as a solvent. For the purpose of dispersing the raw material powder, a known dispersant such as ammonium polycarboxylate or calcium gluconate may be used. The mixed raw material slurry is dehydrated to become a mixed raw material powder.

  The mixed raw material powder is heated using an electric furnace, a gas furnace or the like, and a magnetoplumbite type ferrite compound is formed by a solid phase reaction. This process is called “calcination” and the resulting compound is called “calcination”.

  The calcination step is preferably performed in an atmosphere having an oxygen concentration of 5% or more. This is because the solid phase reaction hardly proceeds when the oxygen concentration is less than 5%. A more preferable oxygen concentration is 20% or more.

  In the calcination step, a ferrite phase is formed by a solid phase reaction with an increase in temperature and is completed at about 1100 ° C., but below this temperature, unreacted hematite (iron oxide) remains and the magnet characteristics are low. When the temperature exceeds 1100 ° C., the effect of the present invention occurs. On the other hand, when the calcining temperature exceeds 1450 ° C., crystal grains grow too much, and there is a risk that inconveniences such as a long time for the pulverization process may occur. Therefore, the calcination temperature is preferably 1100 ° C to 1450 ° C. More preferably, it is 1200 to 1350 degreeC. The calcining time is preferably 0.5 to 5 hours.

When H ₃ BO ₃ is added before calcination, the above reaction is promoted, so that calcination can be performed at 1100 ° C. to 1300 ° C.

The calcined body obtained by the calcining step has a main phase of hexagonal M-type magnetoplumbite type ferrite represented by the following chemical formula, and becomes the oxide magnetic material of the present invention. Compositional formula (1-x) CaO. (X / 2) R ₂ O _3. (N−y / 2) Fe ₂ O ₃ .yMO0.45 ≦ x ≦ 0.7, 0.35 <y ≦ 0.55 4.9 ≦ n ≦ 5.8.

  By pulverizing and / or crushing such a calcined body, a magnetic powder can be obtained, which can be applied to a bond magnet or a magnetic recording medium. In addition, manufacture of said calcined body can also employ | adopt well-known manufacturing techniques, such as a spray pyrolysis method and a coprecipitation method.

  When the magnetic powder is applied to a bonded magnet, the magnetic powder is mixed with flexible rubber, hard light plastic, or the like and then molded. The molding process may be performed by a method such as injection molding, extrusion molding, or roll molding. Moreover, when applying magnetic powder to a bond magnet, in order to relieve | moderate the crystal distortion of magnetic powder, it is preferable to heat-process in the temperature range of 700 to 1100 degreeC for about 0.1 to 3 hours. A more preferable temperature range is 900 ° C to 1000 ° C.

  In addition, when applying magnetic powder to a magnetic recording medium, after applying the above heat treatment to the magnetic powder, it is possible to prepare a coating type magnetic recording medium by kneading with various known binders and applying to a substrate. it can. Moreover, the thin film magnetic layer used for a magnetic recording medium can also be formed by sputtering method etc. using the oxide magnetic material of this invention and the sintered magnet using the same as a target.

  Next, the manufacturing method of the sintered magnet using the said oxide magnetic material is demonstrated.

  The calcined body is finely pulverized by a vibration mill, a ball mill and / or an attritor into fine particles. The average particle size of the fine particles is preferably about 0.4 to 0.8 μm (air permeation method). The fine pulverization step may be either dry pulverization or wet pulverization, but is preferably performed in combination.

  In the wet pulverization, an aqueous solvent such as water or various non-aqueous solvents (for example, organic solvents such as acetone, ethanol, xylene) can be used. By the wet pulverization, a slurry in which the solvent and the calcined body are mixed is generated. It is preferable to add 0.2% by mass to 2.0% by mass of a well-known various dispersant and surfactant in a solid content ratio to the slurry. After the wet pulverization, the slurry is preferably concentrated and kneaded.

In the fine pulverization step, additives such as CaCO ₃ , SiO ₂ , SrCO ₃ , Cr ₂ O ₃ and Al ₂ O ₃ can be added to the calcined body in order to improve the magnet characteristics. When these additives are added, CaCO ₃ in terms of CaO is 1.8 mass% or less, SiO ₂ 1.0 mass% or less, SrCO ₃ 0.5 mass% or less, Cr ₂ O ₃ 5.0 mass% or less. Al ₂ O ₃ is preferably 5.0% by mass or less.

In particular, the addition of CaCO ₃ , SiO ₂ , and SrCO ₃ is preferable, and when used in combination with the aforementioned H ₃ BO ₃ addition, high B _r and high H _cJ can be obtained. Since SiO ₂ also has effects such as control of crystal grains during calcination, it is effective to add it before calcination, and it can also be added both before calcination and before pulverization.

  Next, it press-molds in a magnetic field or without a magnetic field, removing the solvent in a slurry. By press molding in a magnetic field, the crystal orientations of the powder particles can be aligned (oriented). Magnet properties can be dramatically improved by press forming in a magnetic field. Furthermore, in order to improve the orientation, 0.01 to 1.0% by mass of a dispersant and a lubricant can be added.

  The molded body obtained by press molding is subjected to a degreasing process as necessary and then a sintering process. The sintering process is performed using an electric furnace, a gas furnace, or the like.

  The sintering process is preferably performed in an atmosphere having an oxygen concentration of 10% or more. If the oxygen concentration is less than 10%, abnormal grain growth or heterogeneous phase generation is caused, and magnet characteristics are deteriorated. A more preferable oxygen concentration is 20% or more, and most preferable is an oxygen concentration of 100%.

  The sintering temperature is preferably 1150 ° C to 1250 ° C. The sintering time is preferably 0.5 to 2 hours. The average crystal grain size of the sintered magnet obtained by the sintering process is about 0.5 to 2 μm.

  After the sintering process, a ferrite sintered magnet product is finally completed through known manufacturing processes such as a processing process, a cleaning process, and an inspection process.

Example 1
In the composition formula (1-x) CaO. (X / 2) La ₂ O _3. (Ny−2) Fe ₂ O ₃ .yCoO, 0.46 ≦ x ≦ 0.7, y = 0.4, 1.15 ≦ x / y ≦ 1.75, n = 5.2, CaCO ₃ powder, La (OH) ₃ powder, Fe ₂ O ₃ powder, Co ₃ O ₄ powder were blended, 0.1% by mass of H ₃ BO ₃ powder was added in an outer frame amount with respect to 100% by mass of the powder after blending. The obtained raw material powder was mixed in a wet ball mill for 4 hours, dried and sized. Subsequently, it was calcined at 1200 ° C. for 3 hours in the atmosphere, and the obtained calcined body was roughly pulverized with a hammer mill to obtain a coarsely pulverized powder.

With respect to the coarsely pulverized powder, 0.3% by mass of CaCO ₃ powder in terms of CaO and 0.4% by mass of SiO ₂ powder are added, and a wet ball mill using water as a solvent has an average particle size of 0 by the air permeation method. Finely pulverized to .55 μm. Subsequently, it shape | molded in the magnetic field, removing the solvent in the obtained finely pulverized slurry. Molding was performed at a magnetic field strength of about 1.3 T at a pressure of about 50 MPa so that the pressurizing direction and the magnetic field direction were parallel. The obtained molded body was fired at 1200 ° C. for 1 hour in the air to obtain a sintered magnet. The remanence B _r of resultant sintered magnets were measured. The measurement results are shown in FIG. In FIG. 1, the vertical axis represents B _r (mT), and the horizontal axis represents the relative ratio x / y between x and y (La and Co).

As apparent from FIG. 1, 1.2 ≦ x / y ≦ 1.65 or higher _{B r} 450 mT in the range of is obtained. x / y is a tendency _{that B r} decreases exceeds 1.2 less than or 1.65. This is presumed to be caused by the generation of a different phase due to deviation from the proper composition. Moreover, it has confirmed that the same tendency is seen also by 0.35 <y <= 0.55. Therefore, the value of x / y is preferably in the range of 1.2 ≦ x / y ≦ 1.65.

Example 2
In the composition formula (1-x) CaO. (X / 2) La ₂ O _3. (Ny / 2) Fe ₂ O ₃ .yCoO, x = 0.51, y = 0.36, 4.8 ≦ Example 1 except that n ≦ 5.6 (Example 2-1), x = 0.66, y = 0.50, 5.0 ≦ n ≦ 6.0 (Example 2-2) Thus, a sintered magnet was produced. The remanence B _r of resultant sintered magnets were measured. The measurement result of Example 2-1 is shown in FIG. 2, and the measurement result of Example 2-2 is shown in FIG. 2 and 3, the vertical axis represents B _r (mT), and the horizontal axis represents the value of n.

As apparent from FIG. 2, y = if 0.36 4.9 ≦ n ≦ 5.4 and a high _{B r} is obtained than 450mT in, and as is apparent from FIG. 3, y = for 0.50 5.2 ≦ n ≦ 5.8 in 450mT higher than _{B r} is obtained. From these results, the value of n in 0.35 <y ≦ 0.55 is preferably 4.9 ≦ n ≦ 5.8. When n exceeds 4.9 less than or 5.8, _{B r} is a tendency to decrease. This is presumed to be caused by the generation of a different phase due to deviation from the proper composition.

Example 3
In the composition formula _{(1-x) CaO · (} x / 2) La 2 O 3 · (n-y / 2) Fe 2 O 3 · yCoO, x = 0.60, y = 0.40, n = 5. A sintered magnet was prepared in the same manner as in Example 1 except that 0 to 0.4% by mass of H ₃ BO ₃ powder was added. The remanence B _r of resultant sintered magnets were measured. The measurement results are shown in FIG.

As apparent from FIG. _4, H ₃ BO 3 added amount of powder is higher than 450mT in a range of 0.3 mass% or less _{B r} is obtained. Amount of H ₃ BO ₃ powder tends to decrease _{B r} exceeds 0.3 mass%. This is presumed to be caused by an increase in the amount of non-magnetic heterogeneous phase generated. Therefore, the amount of H ₃ BO ₃ powder added is desirably 0.3% by mass or less.

Example 4
In the composition formula _{(1-x) CaO · (} x / 2) La 2 O 3 · (n-y / 2) Fe 2 O 3 · yCoO, y = 0.36,0.40,0.50,0. 60, 0.40 ≦ x ≦ 0.75, 4.8 ≦ n ≦ 6.0, and 0 to 0.4% by mass of H ₃ BO ₃ powder was added. A magnetized magnet was produced. Table 1 shows compositions in which good magnet properties were obtained for each y value from the magnet properties of the obtained sintered magnet. Moreover, the magnet characteristic in each composition of Table 1 is shown in FIG. In FIG. 5, the vertical axis represents B _r (mT), and the horizontal axis represents H _cJ (kA / m). Note that Sample Comparative Example 4-1 (y = 0.30) corresponds to Example 2 (n = 5.2) of Patent Document 4.

As apparent from Table 1 and FIG. 5, by optimizing the composition within the range of 0.35 <y <0.60, B _r ≧ 450 and B _r + H _cJ / 4 ≧ 559 are satisfied. Therefore, extremely high magnet characteristics are obtained. When y is 0.35 or less or exceeds 0.55, even if the composition is optimized, the high magnetic characteristics as in the present embodiment cannot be obtained due to the generation of a different phase due to deviation from the appropriate composition. Therefore, the value of y is preferably in the range of 0.35 <y ≦ 0.55.

The sintered magnet containing the oxide magnetic material according to the present invention has a residual magnetic flux density B _r (unit: mT) and an intrinsic coercive force H _cJ (unit: kA / m), and B _r ≧ 450, B _r + H _cJ Because it has extremely excellent magnet characteristics that satisfy the relationship of / 4 ≧ 559, it is optimal for various applications such as various rotating machines, generators, speakers, and the like.

It is a graph showing the relationship between the ratio x / y of the substitution amount y of the residual magnetic flux density B _r and La substitution amount x of Co sintered magnets. Is a graph showing the relationship between the residual magnetic flux density B _r and the molar ratio n of the sintered magnet. Is a graph showing the relationship between the residual magnetic flux density B _r and the molar ratio n of the sintered magnet. It is a graph showing the relationship between the residual magnetic flux density B _r and H ₃ BO ₃ added amount of powder of the sintered magnet. Is a graph showing the relationship between the residual magnetic flux density B _r and the intrinsic coercive force H _cJ of the sintered magnet.

Claims (2)

It is represented by a composition formula (1-x) CaO. (X / 2) R ₂ O _3. (Ny−2) Fe ₂ O ₃ .yMO, where R is at least selected from La, Nd, and Pr. It is a kind of element and necessarily contains La, and M is at least one kind of element selected from Co, Zn, Ni, and Mn and always contains Co, and x, y, and n representing the molar ratio are respectively
0.45 ≦ x ≦ 0.7,
0.35 <y ≦ 0.55,
4.9 ≦ n ≦ 5.8
And an oxide magnetic material having a composition satisfying a relational expression of 1.2 ≦ x / y ≦ 1.65 and having a main phase of ferrite having a hexagonal M-type magnetoplumbite structure. , remanence _{B r} (unit: mT) at 2 3 ° C. and intrinsic coercive force _{H cJ} (unit: kA / m) and is, satisfies the relationship _{B r ≧ 450, B r +} H cJ / 4 ≧ 559 baked A method for producing a magnet , comprising:
Mixing and mixing raw material powders to obtain mixed raw material powders,
Calcining the mixed raw material powder to obtain a calcined body,
Pulverizing the calcined body to obtain fine particles,
Press molding the fine particles to obtain a molded body,
It comprises a sintering step of sintering the molded body to obtain a sintered magnet,
The manufacturing method of the sintered magnet whose said pulverization process is 1 time and whose sintering temperature in the said sintering process is 1150 degreeC-1250 degreeC . Calcining step before and / or method of manufacturing a sintered magnet according to claim 1, tentatively after heating step the _H 3 BO ₃ is added 0.3 wt% or less.