JP2019169560A - Manufacturing method of r-t-b-based sintered magnet - Google Patents

Abstract

To manufacture an R-T-B-based sintered magnet having a high Hand a high H, while reducing a content amount of RH.SOLUTION: A manufacturing method of an R-T-B-based sintered magnet having a prescribed composition, includes: a step of preparing an alloy powder; a formation step of obtaining a compact; a first sinter step of obtaining a first sinter body by heating the compact at a first sinter temperature within 1010°C to 1030°C for a first sinter time within 12-hour to 36-hour; a second sinter step of obtaining a second sinter body by heating the first sinter body at a second sinter temperature lower than the first sinter temperature that 10°C and within 990°C to 1020°C and in a second sinter time longer than the first sinter time by 5-hour and within a range of 17-hour to 41-hour; and a heat treatment step of heating the second sinter body at a heat treatment temperature within 400°C to 800°C.SELECTED DRAWING: None

Description

  The present disclosure relates to a method for manufacturing 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 (EV, HV, PHV, etc.), motors for industrial equipment, and home appliances.

The RTB-based sintered magnet is mainly composed of a main phase composed of an R ₂ T ₁₄ B compound and a grain boundary phase located at the grain boundary portion of the main phase. The R ₂ T ₁₄ B compound as the main phase is a ferromagnetic material having high magnetization and forms the basis of the characteristics of the R—T—B system sintered magnet.

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

Conventionally, in order to improve _HcJ , a large amount of heavy rare earth elements RH such as Dy and Tb has been added to the RTB-based sintered magnet. However, when a large amount of the heavy rare earth element RH is added, _HcJ is improved, but there is a problem that the residual magnetic flux density B _r (hereinafter sometimes simply referred to as “B _r ”) is lowered. Therefore, in recent years, while suppressing a decrease in B _r by causing thickening of the RH in the outer shell surface from the main phase crystal grains by diffusing RH inside the R-T-B based sintered magnet, high H _A method for obtaining _cJ has been proposed.

However, Dy has problems such as unstable supply and price fluctuations because it originally has a small amount of resources and its production area is limited. Therefore, (as small as possible amount) without using much as possible RH such as Dy, while suppressing a decrease in B _r, it is required to obtain a high H _cJ.

In Patent Document 1, R ₂ F ₁₇ M is obtained by lowering the amount of B than a normal R-T-B alloy and containing one or more metal elements M selected from Al, Ga, and Cu. A coercive force is generated while suppressing the content of Dy by ensuring a sufficient volume fraction of the transition metal rich phase (R ₆ T ₁₃ M) generated by generating a phase and using the R ₂ Fe ₁₇ phase as a raw material. It is described that an R-T-B rare earth sintered magnet having a high C can be obtained.

In addition, as described above, the use of the _RTB -based sintered magnet is most often a motor. In particular, the improvement of _HcJ is very effective to ensure high-temperature stability in applications such as electric vehicle motors. However, along with these characteristics, the squareness ratio H _k / H _cJ (hereinafter sometimes simply referred to as H _k / H _cJ ) must also be high. If H _k / H _cJ is low, it causes a problem that demagnetization tends to occur. Therefore, an _RTB -based sintered magnet having high H _cJ and high H _k / H _cJ is required. In the field of R-T-B based sintered magnet, typically, H _k is a parameter to be measured to determine the H k _/ H _cJ is, J (intensity of magnetization) -H (field intensity ) In the second quadrant of the curve, the H-axis reading at a position where J is 0.9 × J _r (J _r is the residual magnetization, J _r = B _r ) is used. A value _obtained by dividing H _k by H _cJ of the demagnetization curve (H _k / H _cJ = H _k (KA / m) / H _cJ (KA / m) × 100 (%)) is defined as the square ratio.

International Publication No. 2013/008756

In the R-T-B type rare earth magnet described in Patent Document 1, although a high H _cJ can be obtained while reducing the Dy content, a general R-T-B type sintered magnet (R ₂ T There was a problem that H _k / H _cJ was lower than that of ₁₄ B type compound having a B amount higher than the stoichiometric ratio.

The present invention aims to provide a method for while reducing the content of RH, to produce a R-T-B based sintered magnet having a high H _cJ and high H _{k /} H _cJ.

Aspect 1 of the present invention
R: 29.5 to 35.0 mass% (R is at least one of rare earth elements, including at least one of Nd and Pr),
B: 0.80 to 0.91% by mass,
Ga: 0.2-1.0 mass%, and T: 61.5-69.5 mass% (T is Fe and Co, 90-100 mass% of T is Fe),
It is a manufacturing method of the RTB system sintered magnet which satisfies the following formula (1),

[T] /55.85> 14 [B] /10.8 (1)
([T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%)

Preparing an alloy powder;
A molding step of molding the alloy powder to obtain a molded body;
The molded body is heated at a first sintering temperature within a range of 1010 ° C. to 1030 ° C. for a first sintering time within a range of 12 hours to 36 hours to obtain a first sintered body. 1 sintering process;
The first sintered body is in a range of 990 ° C. to 1020 ° C. and a second sintering temperature that is 10 ° C. or more lower than the first sintering temperature, and is in a range of 17 hours to 41 hours, and A second sintering step of obtaining a second sintered body by heating for a second sintering time longer than the first sintering time by 5 hours or more;
A heat treatment step of heating the second sintered body at a heat treatment temperature within a range of 400 ° C. to 800 ° C .;
The manufacturing method of the R-T-B type | system | group sintered magnet containing this.

  Aspect 2 of the present invention is the aspect 1 in which, in the second sintering step, the second sintering temperature is in a range of 990 ° C. to 1010 ° C., and is 20 ° C. or lower than the first sintering temperature. It is a manufacturing method of the RTB system sintered magnet as described in above.

According to the production method of the present invention, it is possible to produce an _RTB -based sintered magnet having high H _cJ and high H _k / H _cJ while reducing the content of RH.

  Embodiment shown below illustrates the manufacturing method of the RTB type sintered magnet for materializing the technical idea of this invention, Comprising: This invention is not limited below.

As a result of intensive investigations, the present inventors have found that the present invention is suitable for the production of an RTB-based sintered magnet having a specific composition range as defined below, particularly an extremely narrow specific range of B content. By performing the sintering process in two stages (first sintering process and second sintering process), and appropriately controlling the sintering conditions (temperature and time) of the first sintering process and the second sintering process, It has been found that the magnetic properties of the finally obtained RTB-based sintered magnet can be improved.
The manufacturing method according to the embodiment of the present invention will be described in detail below.

<RTB-based sintered magnet>
First, an RTB-based sintered magnet obtained by the manufacturing method according to the present invention will be described.

(Composition of RTB-based sintered magnet)
The composition of the RTB-based sintered magnet according to this embodiment is
R: 29.5 to 35.0 mass% (R is at least one of rare earth elements, including at least one of Nd and Pr),
B: 0.80 to 0.91% by mass,
Ga: 0.2-1.0 mass%, and T: 61.5-69.5 mass% (T is Fe and Co, 90-100 mass% of T is Fe), Formula (1) is satisfied.

[T] /55.85> 14 [B] /10.8 (1)
([T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%)

With the above composition, the amount of B is smaller than that of a general RTB-based sintered magnet, and Ga and the like are contained. Therefore, an RT-Ga phase is generated at the two-grain grain boundary, High H _cJ can be obtained. Here, the R—T—Ga phase is typically an Nd ₆ Fe ₁₃ Ga compound. The R ₆ T ₁₃ Ga compound has a La ₆ Co ₁₁ Ga ₃ type crystal structure. Moreover, the R ₆ T ₁₃ Ga compound may be an R ₆ T _13-δ Ga _{1 + δ} compound (δ is typically 2 or less) depending on the state. For example, Cu in R-T-B based sintered magnet, if the Al is contained relatively _large, may have been the _{R 6 T 13-δ (Ga} 1-x-y Cu x Al y) 1 + δ is there.
Below, each composition is explained in full detail.

(R: 29.5-35.0 mass%)
R is at least one of rare earth elements and includes at least one of Nd and Pr. Content of R is 29.5-35.0 mass%. R is may become difficult to densification during sintering is less than 29.5% by mass, there is a possibility that the main phase proportion exceeds 35.0% by weight can not be obtained a high B _r drops . The content of R is preferably 29.5 to 33.0% by mass. If R is in such a range, higher _Br can be obtained.

(B: 0.80 to 0.91 mass%)
The content of B in the sintered magnet is 0.80 to 0.91% by mass. If B is less than 0.80% by mass, the R ₂ T ₁₇ phase may be produced and high H _cJ may not be obtained. If it exceeds 0.91% by mass, the amount of R—T—Ga phase produced is small. _Therefore, there is a possibility that high _HcJ cannot be obtained. The content of B is preferably 0.88 to 0.90% by mass, and a higher _HcJ improvement effect is obtained.

Furthermore, the content of B satisfies the following formula (1).

[T] /55.85> 14 [B] /10.8 (1)

Here, [T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%.

By satisfying the formula (1), the content of B becomes smaller than that of a general RTB-based sintered magnet. A general R-T-B type sintered magnet has [T] /55.85 (so that an R ₂ T ₁₇ phase, which is a soft magnetic phase, is not generated in addition to an R ₂ T ₁₄ B phase, which is a main phase. The atomic weight of Fe is less than 14 [B] /10.8 (the atomic weight of B) ([T] is the content of T expressed in mass%). The R-T-B system sintered magnet of the embodiment of the present invention differs from a general R-T-B system sintered magnet in that [T] /55.85 is greater than 14 [B] /10.8. It is defined by equation (1) so as to increase. In addition, since the main component of T in the RTB-based sintered magnet of the embodiment of the present invention is Fe, the atomic weight of Fe was used.

(Ga: 0.2-1.0 mass%)
The Ga content is 0.2 to 1.0 mass%. If Ga is less than 0.2% by mass, the amount of R—T—Ga phase produced is so small that R ₂ T ₁₇ phase cannot be lost and high H _cJ may not be obtained. It will be present unnecessary Ga exceeds 1.0 mass%, B _r decreases the main phase ratio may be lowered.

(T: 61.5-69.5 mass% (T is Fe and Co, 90-100 mass% of T is Fe))
T is at least one of transition metal elements and necessarily contains Fe.
Content of T in a sintered magnet is 61.5-69.5 mass%. When the total amount of T is 100% by mass, 10% by mass or less can be replaced with Co. That is, 90% by mass or more of the total amount of T is Fe. Further, the total amount of T (100% by mass) may be Fe. Although the corrosion resistance can be improved by containing Co, if the substitution amount of Co exceeds 10% by mass of Fe, high _Br may not be obtained. The T content is 61.5% by mass or more and satisfies the above-described formula (1). If the content of T exceeds or 69.5 wt% less than 61.5 wt%, significantly _{B r} may be lowered. Preferably, T is the balance.

Furthermore, even if T is the balance, the RTB-based sintered magnet of the present invention is Cr as an inevitable impurity usually contained in didymium alloy (Nd-Pr), electrolytic iron, ferroboron, and the like. Mn, Si, La, Ce, Sm, Ca, Mg and the like can be contained. Furthermore, O (oxygen), N (nitrogen), C (carbon), etc. can be illustrated as an inevitable impurity in a manufacturing process. In addition, the RTB-based sintered magnet of the present invention may contain one or more other elements (elements intentionally added other than unavoidable impurities). For example, as such an element, a small amount (each about 0.1% by mass) of Ag, Zn, In, Sn, Ti, Ge, Y, H, F, P, S, V, Ni, Mo, Hf, Ta , W, Nb, Zr and the like may be contained. Moreover, you may intentionally add the element mentioned as an inevitable impurity mentioned above. Such elements may be included in a total of about 1.0% by mass, for example. If it is this grade, it is fully possible to obtain the _RTB system sintered magnet which has high _HcJ .

  The sintered magnet of the present invention may further contain any other element. Other elements that can be selectively contained as described above are exemplified below.

(Cu: more than 0% by mass, 0.50% by mass or less)
By including an appropriate amount of Cu, _HcJ can be further improved.
Cu may be contained at 0.50 mass% or less. The Cu content is preferably 0.05 to 0.50 mass%. When Cu is contained at 0.05% by mass to 0.50% by mass, _HcJ can be further improved. The content of Cu is more preferably 0.05% by mass or more.

(Al: more than 0% by mass, 0.50% by mass or less)
By including an appropriate amount of Al, _HcJ can be further improved.
Al may be contained at 0.50 mass% or less. The content of Al is preferably 0.05 to 0.50% by mass. When Al is contained at 0.50% by mass or less, _HcJ can be further improved. In general, Al can be contained in an amount of 0.05% by mass or more as an inevitable impurity in the production process. However, even if the total amount of the inevitable impurity and the amount intentionally added is 0.5% by mass or less, Good. The Al content is more preferably 0.05% by mass or more.

(Magnetic characteristics of RTB-based sintered magnet)
The sintered magnet according to the present invention exhibits high H _cj and high H _k / H _cJ . In _{particular, H cj} is 1400kA / m or more, and it preferably _H k _{/ H cJ} is 85 greater, _{also, H cj} is 1500 kA / m greater, and still more preferably _H k _{/ H cJ} of 85 greater. Further, it is preferred _{H k} is 1200 kA / m or more, and more preferably 1230kA / m or more.

<Method for producing RTB-based sintered magnet>
Next, the manufacturing method of the RTB system sintered magnet which concerns on this invention is demonstrated.
The manufacturing method of the RTB-based sintered magnet includes a step of preparing an alloy powder, a forming step, a first sintering step, a second sintering step, and a heat treatment step.
Hereinafter, each step will be described.

(1) Step of preparing alloy powder A metal or alloy of each element is prepared so as to have the above composition, and a flaky alloy is produced by using a strip casting method or the like.
The obtained flaky alloy is hydrogen crushed so that the size of the coarsely pulverized powder is 1.0 mm or less, for example. Next, the coarsely pulverized powder is finely pulverized by a jet mill or the like, for example, a finely pulverized powder (alloy powder) having a particle diameter D50 (value obtained by a laser diffraction method by airflow dispersion method (median diameter)) of 3 to 7 μm ) A known lubricant may be used as an auxiliary agent for the coarsely pulverized powder before jet mill pulverization and the alloy powder during and after jet mill pulverization.

(2) Forming step Using the obtained alloy powder, forming in a magnetic field is performed to obtain a formed body. In the magnetic field molding, a dry alloy method in which a dry alloy powder is inserted into a mold cavity and molded while applying a magnetic field, a slurry in which the alloy powder is dispersed is injected into the mold cavity, Any known forming method in a magnetic field may be used, including a wet forming method of forming while discharging the slurry dispersion medium.

(3) Sintering process The sintered compact (sintered magnet) is obtained by sintering the molded object obtained at the formation process. In the present invention, a sintered magnet is manufactured by performing two-stage sintering (a first sintering process and a second sintering process). In both the first and second sintering steps, sintering is performed at a sintering temperature lower than a general sintering temperature and a sintering time longer than a general sintering time.

(3-1) First Sintering Step In the first sintering step, the molded body is a first sintering temperature within a range of 1010 ° C. to 1030 ° C. and a first sintering temperature within a range of 12 hours to 36 hours. Heat with sintering time. Thereby, a 1st sintered compact is obtained.
General sintering conditions are a sintering temperature of 1040 to 1060 ° C. and a sintering time of about 4 to 6 hours. That is, the first sintering temperature of the first sintering step of the present invention is about 10-50 ° C. lower than the general sintering temperature, and the first sintering time is lower than the general sintering time. About 2 to 8 times longer.

(3-2) Second Sintering Step In the second sintering step, the first sintered body is in a range of 990 ° C. to 1020 ° C., and is a second lower than the first sintering temperature by 10 ° C. or more. Sinter at the sintering temperature. The sintering time (second sintering time) is in the range of 17 hours to 41 hours and is heated for 5 hours or longer than the first sintering time. Thereby, the 2nd sintered compact (sintered magnet) is obtained.
In the sintering conditions of the second sintering step of the present invention, the second sintering temperature is further lower than the first sintering temperature, which is lower than the general sintering temperature, and the second sintering time is Even longer than the first sintering time, which is longer than the sintering time. Preferably, in the second sintering step, the second sintering temperature is in a range of 990 ° C. to 1010 ° C. and is 20 ° C. or lower than the first sintering temperature. An _RTB -based sintered magnet having a higher H _cJ and a higher H _k / H _cJ can be produced while reducing the content of RH.

You may perform a 1st sintering process and a 2nd sintering process continuously. That is, after the first sintering step, the second sintering step may be performed as it is by cooling from the first sintering temperature to the second sintering temperature. Alternatively, the second sintering step may be performed by once cooling to room temperature after the completion of the first sintering step and then raising the temperature to the second sintering temperature.
In both the first sintering step and the second sintering step, the sintering is preferably performed in a vacuum atmosphere or an atmospheric gas in order to prevent oxidation due to the atmosphere during sintering. The atmosphere gas is preferably an inert gas such as helium or argon.

(4) Heat treatment process The obtained 2nd sintered compact (sintered magnet) is heat-treated for the purpose of improving magnetic characteristics. The heat treatment temperature is in the range of 400 ° C to 800 ° C. Known conditions can be used for the heat treatment time. For example, heat treatment can be performed for 60 minutes to 300 minutes. For example, heat treatment (one-step heat treatment) only at a relatively low temperature (400 ° C. or more and 600 ° C. or less) may be performed, or after heat treatment at a relatively high temperature (700 ° C. or more and 800 ° C. or less), the heat treatment is relatively low. Heat treatment (two-stage heat treatment) may be performed at a temperature (400 ° C. to 600 ° C.). Preferable conditions are as follows: heat treatment at 730 ° C. to 1020 ° C. for 5 minutes to 500 minutes, cooling (after cooling to room temperature or after cooling to 440 ° C. to 550 ° C.), and further at 440 ° C. to 550 ° C. Heat treatment for about 500 minutes to 500 minutes. The heat treatment atmosphere is preferably a vacuum atmosphere or an inert gas (such as helium or argon).

  For the purpose of obtaining a final product shape, the obtained sintered magnet may be subjected to machining such as grinding. In that case, the heat treatment may be performed before or after machining. Furthermore, you may surface-treat to the obtained sintered magnet. The surface treatment may be a known surface treatment, and for example, a surface treatment such as Al deposition, electric Ni plating, or resin coating can be performed.

The sintered magnets thus obtained had both improved H _cj and H _k / H _cJ .

The R-T-B system sintered magnet is approximately No. 1 in Table 1. Each element was weighed so as to have the composition shown in M1 to M4 and cast by a strip casting method to obtain a flaky alloy. The obtained flaky alloy was hydrogen embrittled in a hydrogen-pressurized atmosphere, and then subjected to a dehydrogenation treatment in which it was heated and cooled in vacuum to 550 ° C. to obtain coarsely pulverized powder. Next, after adding and mixing 0.04% by mass of zinc stearate as a lubricant with respect to 100% by mass of the coarsely pulverized powder, the resulting coarsely pulverized powder was mixed with an airflow pulverizer (jet mill device). was dry milled in a nitrogen _{atmosphere, D 50} was obtained alloy powder of 4.3 [mu] m. The component analysis results of the obtained alloy powder are shown in Table 1. Shown in M1-M4. Each component in Table 1 (other than O, N, and C) was measured using high frequency inductively coupled plasma optical emission spectrometry (ICP-OES). The O (oxygen) content is a gas melting-infrared absorption method, the N (nitrogen) content is a gas melting-thermal conduction method, and the C (carbon) content is a gas analysis device by a combustion-infrared absorption method. Measured using.

  A liquid lubricant was added to and mixed with the alloy powder in an amount of 0.3% by mass with respect to 100% by mass of finely pulverized powder, and then molded in a magnetic field to obtain a molded body. The forming apparatus used was a so-called right-angle magnetic field forming apparatus (transverse magnetic field forming apparatus) in which the magnetic field application direction and the pressing method direction were orthogonal.

  The obtained compact was subjected to the first sintering step, the second sintering step and the heat treatment step under the conditions shown in Table 2 to obtain an RTB-based sintered magnet. For example, sample no. 1 is No. The molded body obtained by molding the alloy powder of M1 was heated at a temperature of 1020 ° C. for 24 hours and then cooled to room temperature to obtain a first sintered body, and then the first sintered body was heated to a temperature of 1000 ° C. After heating for 36 hours and cooling to room temperature, a second sintered body was obtained, and then the second sintered body was heated at 800 ° C. for 2 hours, then cooled to 490 ° C., and further heated at 490 ° C. for 3 hours. It is a thing. Sample No. 2-24 are described similarly. Sample No. 5-12 do not perform the second sintering step.

The obtained R-T-B sintered magnet was machined to prepare a sample having a length of 7 mm, a width of 7 mm, and a thickness of 7 mm, and the magnetic properties were measured with a BH tracer. The results are shown in Table 3. Incidentally, _{H k} is J value of (the magnetization magnitude) -H in the second quadrant of the (magnetic field strength) curve, J is 0.9 × _{J r (J r} residual _{magnetization,} J r = _{B r)} Is the value of H at the position.

In this specification, the quality determination of H _cJ and H _k / H _cJ is determined by whether or not H _cJ > 1300 kA / m and H _k / H _cJ > 85 are satisfied. In the invention, H _cJ and H _k / H _cJ are both high, that is, those satisfying the conditions of “H _cJ > 1300 kA / m and H _k / H _cJ > 85” are referred to as “examples of the present invention”, and H _cJ , Since one or both of H _k / H _cJ is low, a _sample that does not satisfy the conditions “H _cJ > 1300 kA / m and H _k / H _cJ > 85” is referred to as “comparative example”.
As shown in Table 3, all of the inventive examples (sample Nos. 1 to 3) satisfy H _cJ > 1300 kA / m and H _k / H _cJ > 85, and have high H _cJ and high H _k / H _cJ. have. In contrast, sample no. No. 4, the conditions of the first sintering step, the second sintering step, and the heat treatment step satisfy the provisions of the present invention, but the composition is outside the scope of the present invention, so that high H _k / H _cJ is Although H _cJ is greatly reduced, the conditions of “H _cJ > 1300 kA / m and H _k / H _cJ > 85” are not satisfied, and high H _cJ and high H _k / H _{cJ are obtained.} Could not get together.
Sample No. 1 in which the first sintering temperature and the first sintering time in the first sintering step are outside the scope of the present invention and the second sintering step is not performed. 5-12, sample No. 1 in which the first temperature in the first sintering step is outside the scope of the present invention. 13-16, No. 2 in which the second sintering temperature in the second sintering step is outside the scope of the present invention. 17-20 and the heating temperature of the 1st sintering process and the 2nd sintering process is the same. 21 to 24 did not satisfy the conditions of “H _cJ > 1300 kA / m and H _k / H _cJ > 85”, and could not obtain both high H _cJ and high H _k / H _cJ .

Claims (2)

R: 29.5 to 35.0 mass% (R is at least one of rare earth elements, including at least one of Nd and Pr),
B: 0.80 to 0.91% by mass,
Ga: 0.2-1.0 mass%, and T: 61.5-69.5 mass% (T is Fe and Co, 90-100 mass% of T is Fe),
It is a manufacturing method of the RTB system sintered magnet which satisfies the following formula (1),

[T] /55.85> 14 [B] /10.8 (1)
([T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%)

Preparing an alloy powder;
A molding step of molding the alloy powder to obtain a molded body;
The molded body is heated at a first sintering temperature within a range of 1010 ° C. to 1030 ° C. for a first sintering time within a range of 12 hours to 36 hours to obtain a first sintered body. 1 sintering process;
The first sintered body is in a range of 990 ° C. to 1020 ° C. and a second sintering temperature that is 10 ° C. or more lower than the first sintering temperature, and is in a range of 17 hours to 41 hours, and A second sintering step of obtaining a second sintered body by heating for a second sintering time longer than the first sintering time by 5 hours or more;
A heat treatment step of heating the second sintered body at a heat treatment temperature within a range of 400 ° C to 800 ° C.   2. The RT according to claim 1, wherein in the second sintering step, the second sintering temperature is in a range of 990 ° C. to 1010 ° C. and is lower than the first sintering temperature by 20 ° C. or more. -Manufacturing method of B type sintered magnet.