JP2009295638A - Method for manufacturing r-t-b magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an R-T-B magnet capable of suppressing fluctuation in a composition of a molded body in baking, improving magnetic characteristics of the obtained R-T-B magnet and preventing a variation in the magnetic characteristics accompanied by the fluctuation in the composition of the R-T-B magnet. <P>SOLUTION: This method for manufacturing an R-T-B magnet comprises: a molding step of forming a molded body of a magnetic material, a temperature rise step of heating the molded body to raising the temperature of the molded body up to a baking temperature T<SB>s</SB>°C, and a temperature maintaining step of maintaining the temperature of the molded body at T<SB>s</SB>°C. In the temperature rise step or the temperature maintaining step, the atmosphere is switched from a vacuum atmosphere to an inert gas atmosphere, and switching from the vacuum atmosphere to the inert gas atmosphere is executed before a time point t<SB>1</SB>and after a time point t<SB>2</SB>, where t<SB>1</SB>is a time point when the temperature of the molded body reaches T<SB>s</SB>°C, and t<SB>2</SB>is a time point when the temperature of the molded body reaches T<SB>s</SB>°C and 50 minutes have not elapsed while maintaining the temperature at T<SB>s</SB>°C after t1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an R-T-B magnet.

  A rare earth magnet having a composition of R-T-B (R is a rare earth element, T is a metal element such as Fe, Co, etc.) is a magnet having excellent magnetic properties. It is. In general, the residual magnetic flux density (Br) and the coercive force (Hcj) are used as indices indicating the magnetic characteristics of the magnet. The larger these products (maximum energy product), the better the magnetic characteristics of the magnet. Means that.

As a method for producing an R-T-B magnet, for example, in the following Patent Document 1, a composition formula R _X (Fe _1-a Co _a ) _Y B _Z T _b (R is selected from rare earth elements including Y) 1 type or 2 types or more, T is 1 type or 2 types or more selected from transition metals other than Al, Si or Fe, Co, X, Y, Z and a, b are 11 <= X <= 16, 70 <= Y ≦ 85, 4 ≦ Z ≦ 9, 0 ≦ a ≦ 0.2, 0 ≦ b ≦ 4) in a rare earth magnet manufacturing method, in a vacuum or in an inert gas atmosphere below atmospheric pressure, Sintering is carried out at 1,150 ° C. until the density of the sintered body reaches 90 to 98% of the true density, and subsequently 0.1 to 0.1 at 900 to 1,150 ° C. in an inert gas atmosphere of 1 to 20 atm. A production method characterized by sintering for 5 hours is shown. Patent Document 1 below describes that according to this manufacturing method, a high-performance magnet having an increased density, residual magnetization, and coercive force can be obtained.
JP 2000-233201 A

  However, in the manufacturing method shown in Patent Document 1, the composition of the molded body (sintered body precursor) during sintering is likely to fluctuate, and is assumed from the desired composition of the magnet (sintered body after aging treatment). In many cases, the magnetic properties of the magnet actually obtained are lower than the magnetic properties. In addition, with recent downsizing and thinning of electronic devices, magnets mounted on electronic devices are also required to be downsized and thinned. However, the smaller the magnets are, the more thin the magnets are being sintered. The composition of the molded body tends to fluctuate, and there is a possibility that the magnetic properties of the obtained magnet will be lowered.

  Therefore, the present invention has been made in view of such circumstances, and can suppress fluctuations in the composition of the molded body during firing, and can improve the magnetic properties of the resulting RTB-based magnet. An object of the present invention is to provide a method for producing an R-T-B system magnet that can prevent variations in magnetic properties due to variations in the composition of the R-T-B system magnet.

In order to achieve the above object, the RTB-based magnet manufacturing method of the present invention includes a molding step of forming a molded body from a magnetic material, and heating the molded body to set the temperature of the molded body to a firing temperature T _s ° C. And a temperature holding step for keeping the temperature of the molded body at T _s ° C. In the temperature raising step or the temperature holding step, the atmosphere is switched from a vacuum atmosphere to an inert gas atmosphere. and, switching to the inert gas atmosphere from the vacuum atmosphere, and performing the following t ₁ after t ₂ previously.
t _1: the temperature of the molded body T _s ° C. prior to reaching the point t _2: t ₁ later, the temperature of the molded body was allowed to reach T _s ° C., prior to lapse 50 minutes hold a further T _s ° C. Time

In the production method of the R-T-B magnet of the present invention, in the Atsushi Nobori step or the temperature holding step, switching from the vacuum atmosphere firing atmosphere of the shaped body to t ₁ after t ₂ previously to an inert gas atmosphere As a result, fluctuations in the composition of the molded body can be suppressed. In particular, in the present invention, it is possible to suppress the rare earth element evaporation from the molded body and the reaction between the molded body and the impurity gas, which tend to occur under conventional firing conditions. As a result, the obtained R-T-B magnet has a small decrease in magnetic properties, particularly coercive force (Hcj), due to composition fluctuations during firing, and the results are compared with a magnet obtained by a conventional manufacturing method. It has a high magnetic characteristic. Further, according to the present invention, it is possible to prevent variations in magnetic characteristics due to variations in the composition of the R-T-B magnet. Furthermore, according to the present invention, it can also be expected to suppress a decrease in the density (sintered density) of the molded body (sintered body) after firing.

In firing the compact, if the firing atmosphere is switched from a vacuum atmosphere to an inert gas atmosphere at a time prior to t ₁ (when the solvent or additive is not sufficiently removed from the compact), the sintering density increases. Since it is difficult, the residual magnetic flux density Br of the obtained RTB-based magnet tends to decrease, or the time required for increasing the sintered density tends to increase. Further, when the firing atmosphere at a later point in time than t ₂ to switch from the vacuum atmosphere to an inert gas atmosphere, easily occur reaction with evaporation or moldings and impurity gas of a rare earth element from the molded body, and the grain in the molded body Since it is difficult to control the growth, the coercive force Hcj of the obtained RTB-based magnet tends to decrease. Therefore, in the present invention, by switching from the vacuum atmosphere sintering atmosphere to t ₁ after t ₂ previously to an inert gas atmosphere, it is possible to suppress these tendencies.

The present invention, t ₁ is preferably a time when the temperature was allowed to reach a molded body (T s _-40) ℃.

  Thereby, it becomes easy to suppress the fluctuation | variation of a composition of a molded object, and it becomes easy to suppress especially the evaporation of the rare earth element from the molded object which was easy to occur on the conventional baking conditions.

The present invention, in the Atsushi Nobori step, after holding a predetermined time the temperature of the molded body (T s _-40) ℃, it is preferable to bring the temperature of the molded body T _s ° C.. Thereby, before reaching T _s ° C., the molded body is held for a certain period of time at a temperature close to T _s , and as a result, it is possible to more reliably suppress a decrease in sintered density and obtain R The magnetic characteristics of the -T-B magnet can be further improved.

  In the said invention, it is preferable that the atmospheric pressure of an inert gas atmosphere shall be 50 Pa-80 kPa. If the pressure in the inert gas atmosphere is too small, it tends to be difficult to suppress the evaporation of rare earth elements from the molded body and the reaction between the molded body and the impurity gas, and if the pressure in the inert gas atmosphere is too large, It is difficult for the inert gas that has entered the fine voids to escape from the molded body, and the sintered density tends not to increase. Therefore, in the present invention, these tendencies can be suppressed by setting the pressure of the inert gas atmosphere within the above-mentioned preferable range.

  According to the present invention, fluctuations in the composition of the compact during firing can be suppressed, the magnetic properties of the resulting R-T-B magnet can be improved, and fluctuations in the composition of the R-T-B magnet can be achieved. Thus, it is possible to provide a method for manufacturing an R-T-B magnet that can prevent variations in magnetic properties associated with.

  Hereinafter, a preferred embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

(Method for manufacturing R-T-B magnet)
The manufacturing method of the RTB-based magnet of this embodiment includes a magnetic powder manufacturing step (step 1) for manufacturing a magnetic powder made of an alloy (magnetic material) that is a raw material of the RTB-based magnet, and magnetic powder. Forming step (step 2) for forming a green body from the above, a temperature raising step and a temperature holding step (step 3) for firing the green body to obtain a sintered body, and an aging treatment step for applying an aging treatment to the sintered body ( Step 4).

<Step 1: Magnetic powder production process>
In the magnetic powder production process, an alloy (magnetic material) is prepared so that an R-T-B magnet having a desired composition can be obtained. In this step, for example, a simple substance, an alloy, a compound, or the like containing an element such as a metal corresponding to the composition of the R-T-B magnet is dissolved in an inert gas atmosphere such as vacuum or Ar, and then used. An alloy having a desired composition is produced by performing an alloy production process such as a casting method or a strip casting method.

  The type of the R-T-B magnet is not particularly limited. For example, the rare earth element R mainly includes Nd, but has a composition in which a rare earth element and a transition element other than the rare earth element are combined. Is preferred. Specifically, the rare earth element includes at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. , B as an essential element, and an R—Fe—B magnet in which the balance is Fe is exemplified. Such R-T-B magnets can be made of Co, Ni, Mn, Al, Nb, Zr, Ti, W, Mo, V, Ga, Zn, Bi, Ta, Cu, Sn, Ag as required. And elements such as Si may be further contained.

  Next, the obtained alloy is coarsely pulverized to form a magnetic coarse powder having a particle size of about several hundred μm, and the magnetic coarse powder is further finely pulverized to obtain a magnetic powder having a particle size of about several μm. Form.

  As a method of coarsely pulverizing an alloy, for example, a method using a coarse pulverizer such as a jaw crusher, a brown mill, a stamp mill, or the like, or after self-occlusion of hydrogen in an alloy, self-based on the difference in hydrogen storage amount between different phases. Examples thereof include a method (hydrogen storage pulverization method) that causes disintegrative pulverization. As a method for finely pulverizing the magnetic coarse powder, for example, the magnetic coarse powder is pulverized using a fine pulverizer such as a jet mill, a ball mill, a vibration mill, or a wet attritor while appropriately adjusting conditions such as the pulverization time. A method is mentioned. An additive such as stearic acid may be added as a grinding aid.

<Step 2: Molding process>
Next, in the molding step, a molded body is formed from the magnetic powder. When dry molding of magnetic powder is performed, after the magnetic powder is filled in the mold, compression molding is performed while applying a magnetic field to the magnetic powder in the mold, thereby forming a mold having a predetermined magnetic field orientation degree. Form the body. An additive such as stearic acid may be added to the magnetic powder as a molding aid. Alternatively, stearic acid or the like may be applied or sprayed on the mold surface.

  When performing wet molding of magnetic powder, after filling a slurry containing magnetic powder and a solvent such as oil in the mold, by performing compression molding while applying a magnetic field to the slurry in the mold, A molded body having a predetermined magnetic field orientation is formed.

  The shape of the molded body obtained by molding is not particularly limited, and can be changed according to the desired shape of the R-T-B magnet, such as a columnar shape, a flat plate shape, or a ring shape.

  The pressing direction during molding may be the same as the magnetic field application direction, or may be perpendicular to the magnetic field application direction, but more excellent magnetic properties can be obtained by applying pressure perpendicular to the magnetic field application direction. There is a tendency. Moreover, the magnetic field intensity at the time of shaping | molding can be 400-1600 kA / m, and pressurization can be 30-300 MPa. By forming in a magnetic field under such conditions, it tends to be easy to obtain an R-T-B magnet having good magnetic properties.

  When wet molding is performed, in the solvent removal treatment step after the molding step, the molded body is heated, for example, in a vacuum to remove the solvent and additives remaining in the molded body. In the solvent removal treatment step, usually, the sintered compact does not proceed, but the sintering may partially proceed.

<Step 3: Temperature raising step and temperature holding step>
FIG. 1 is a diagram illustrating an example of a temperature profile of heating performed in the temperature raising step and the temperature holding step. In FIG. 1, the horizontal axis indicates the elapsed time (minutes) from the start of firing, and the vertical axis indicates the temperature (° C.) at each elapsed time. As shown in FIG. 1, in the temperature raising step, the molded body after the desolvation treatment step is heated so that the temperature of the molded body reaches the firing temperature T _s ° C. Hold at _s ° C for a predetermined time. After the temperature holding step, the molded body is rapidly cooled to sinter the molded body to obtain a sintered body. In FIG. 1, although the time at which the temperature was allowed to reach the green body by heating the molded body (T s _-40) ℃ is set to t _1, t ₁ is reached the temperature of the molded body T _s ° C. If it is the time before making it, it will not specifically limit.

  In addition, although the temperature at the time of starting temperature rising was described (illustrated) as an example when temperature rising started from 0 ° C., the temperature is often higher than 0 ° C. (for example, near room temperature) in many cases. In addition, the temperature of the molded body at the time of firing (temperature raising step and temperature holding step) can be changed, for example, by adjusting the ambient temperature of the molded body. "Can be regarded as the temperature of the molded body itself at that time.

Incidentally, preferred _{T s,} the composition of the magnetic powder, grinding method, differences such as particle size and particle size distribution may vary depending on various conditions, it may be about 1000 to 1200 ° C.. The time for maintaining the temperature of the compact at T _s is preferably adjusted according to various conditions such as the composition of the magnetic powder contained in the compact, the pulverization method, the difference in particle size and particle size distribution, etc., but 1 to 5 hours. It should be about.

In the temperature raising step and the temperature holding step, the molded body is heated in a vacuum atmosphere and then heated in an inert gas atmosphere. And in this embodiment, such a change of a firing atmosphere is implemented at the time shown below. That is, the time just before to reach the temperature of the molded body by heating the molded body to T _s ° C. and t _1, t ₁ and later, the molded body was further heated to reach the temperature of the molded body T _s ° C., Furthermore, when the time before holding the temperature of the molded body at T _s ° C. for 50 minutes and letting it be t ₂ , switching from the vacuum atmosphere to the inert gas atmosphere is performed after t _{1 and} before t ₂ .

By switching the firing atmosphere of the compact from a vacuum atmosphere to an inert gas atmosphere at t ₁ to t ₂ , fluctuations in the composition of the compact and reaction between the compact and the impurity gas can be suppressed. In particular, in the embodiment, evaporation of rare earth elements (for example, Nd) from the molded body can be suppressed. As a result, it is possible to improve the magnetic properties, particularly the coercive force (Hcj), of the obtained RTB-based magnet. Moreover, by switching the firing atmosphere of the compact from a vacuum atmosphere to an inert gas atmosphere at t ₁ to t ₂ , it can be expected to suppress a decrease in the sintered density, and further, the composition of the R-T-B system magnet Variations in magnetic characteristics due to fluctuations can be prevented.

Note that if the firing atmosphere is switched from a vacuum atmosphere to an inert gas atmosphere at a time prior to t ₁ , the sintered density is difficult to increase, so that the residual magnetic flux density Br of the resulting RTB-based magnet decreases. Or the time required for increasing the sintered density tends to increase. Further, when the firing atmosphere at a later point in time than t ₂ to switch from the vacuum atmosphere to an inert gas atmosphere, easily occur reaction with evaporation or moldings and impurity gas of a rare earth element such as Nd from the molded body, also formed body Since it is difficult to control the grain growth inside, the Hcj of the resulting RTB-based magnet tends to decrease. Therefore, these tendencies can be suppressed by switching the firing atmosphere from a vacuum atmosphere to an inert gas atmosphere at the time t _{1 to} t ₂ .

t ₁ is preferably the time when the temperature of the molded body is reached to (T _s −40) ° C. by heating the molded body. Further, t ₁ is more preferably set to the time when the temperature of the molded body is reached to (T _s -20) ° C. by heating the molded body. That is, in firing the molded body, it is preferable that the time when the molded body is heated to reach (T _c −20) ° C. higher than (T _s −40) ° C. is defined as t ₁ . Thereby, not only can the magnetic properties of the obtained R-T-B system magnet be further improved, but also a decrease in the sintered density can be more reliably suppressed.

In the temperature raising step, it is preferable that the temperature of the molded body is maintained at (T _s -40) ° C. for a certain time, and then the molded body is further heated to reach the firing temperature T _s C. Thereby, before reaching T _s ° C., the molded body is held at a temperature close to T _s for a certain period of time, and as a result, the composition fluctuation of the molded body is delayed for a certain period of time. That is, it becomes possible to switch the firing atmosphere from a vacuum atmosphere to an inert gas atmosphere at a relatively late point. As a result, it is possible to more reliably suppress a decrease in sintered density.

This holding is effective even when the temperature of the molded body at t ₁ is (T _s −40) ° C. or (T _s −20) ° C. For example, when the temperature of the molded body at t ₁ is (T _s −40) ° C., the firing atmosphere may be switched during the holding. On the other hand, when the temperature of the molded body at t ₁ is (T _s −20) ° C., after holding at (T _s −40) ° C. in a vacuum atmosphere, the molded body is further heated ( T _s -20) The firing atmosphere is switched after reaching the temperature.

When the temperature of the molded body is held at (T _s -40) ° C, the holding time is preferably 15 to 45 minutes, and more preferably 30 minutes. If the time for maintaining the temperature of the compact at (T _s -40) ° C. is too short, the effect of switching the atmosphere at t ₂ tends to be small, and the temperature of the compact is maintained at (T _s -40) ° C. When the time to do is too long, a molded object will oversinter and there exists a tendency for the magnetic characteristic of the magnet obtained to fall. Therefore, by setting the time for maintaining the temperature of the molded body at (T _s -40) ° C. within the above preferable range, these tendencies can be suppressed and the above effects can be obtained satisfactorily.

  In an inert gas atmosphere, the pressure is preferably 50 Pa to 80 kPa. If the pressure of the inert gas atmosphere is too small, it tends to be difficult to suppress the evaporation of rare earth elements (for example, Nd) from the molded body. If the pressure of the inert gas atmosphere is too large, fine voids in the molded body are formed. The inactive gas that has entered tends to be difficult to escape from the molded body, and the sintered density tends not to increase. Therefore, these tendencies can be suppressed by setting the pressure of the inert gas atmosphere within the above-mentioned preferable range.

In the present embodiment, the temperature raising step and the temperature holding step can be performed by, for example, setting the molded body in a state where it is placed on a flat plate-like firing jig and heating the molded body. At this time, the molded body is preferably installed on the firing jig such that the side surface having the largest area among the side surfaces of the molded body faces the firing jig. Thereby, at the time of firing, the largest side surface of the molded body is sealed by the firing jig, so that it is possible to further prevent evaporation of rare earth elements such as Nd from the molded body, as well as the molded body and impurities. Reaction with gas can be prevented. Further, since the same effect is obtained, the area S (cm ² ) exposed to the firing atmosphere (vacuum or inert gas atmosphere) on the surface of the molded body (the firing jig on the surface of the molded body) The ratio S / W of the surface area not in contact) and the weight W (g) of the molded body is preferably 0.8 or less. In addition, S / W becomes large, so that the dimension of a molded object becomes small.

<Step 4: Aging process>
In order to improve the magnetic properties of the sintered body obtained after the temperature raising step and the temperature holding step, for example, it is preferable to perform an aging treatment by heating at a temperature lower than that during firing. The aging treatment is performed, for example, by two-step heating at 700 to 900 ° C. for 1 to 3 hours, further heating at 500 to 700 ° C. for 1 to 3 hours, or one-step heating at about 600 ° C. for 1 to 3 hours.

  The sintered body (R-T-B magnet) after the aging treatment may be subjected to a treatment for smoothing the surface or may be cut into a desired size. Moreover, you may further form the protective layer for anti-rusting on the surface of the obtained RTB type magnet. In this manner, an R-T-B magnet that can be put to practical use can be obtained.

According to the manufacturing method of the embodiment as described above, an RTB-based magnet is obtained. In the above manufacturing method, the density of the sintered body obtained after sintering is 7.58 g / cm ³ or more. It is preferable that it is 7.60 g / cm ³ or more. When the sintered body has such a density, the obtained magnet also has a high density and can have excellent magnetic properties. Hcj is preferably 2175 kA / m or more. And according to the manufacturing method of the said embodiment, evaporation etc. of Nd etc. can be suppressed and the fluctuation | variation of the composition of a molded object can be suppressed.

  As mentioned above, although preferred embodiment of the manufacturing method of the RTB type magnet which concerns on this invention was described, this invention is not necessarily limited to embodiment mentioned above.

  For example, in the above-described embodiment, the aging treatment is performed on the sintered body after firing. However, when sufficient magnetic properties are obtained in the sintered body after firing, the aging treatment is not necessarily performed. May be. Moreover, the manufacturing method of the RTB system magnet of this invention may further include processes other than the process mentioned above as needed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

(Example 1)
As a raw material (magnetic material) for the Nd—Fe—B magnet, a raw material alloy containing 12.0 atomic% Nd, 6.1 atomic% B, and Fe as the balance was prepared. The alloy was coarsely pulverized in a hydrogen storage furnace, and then finely pulverized using a jet mill until the average particle size of the raw material alloy became 4 μm to obtain a magnetic powder. The raw alloy was roughly pulverized and finely pulverized in a low oxygen atmosphere. Next, the obtained magnetic powder was compression-molded under an orientation magnetic field using a molding apparatus to obtain a molded body.

Next, the compact was placed in a firing furnace, and the compact was fired under the following firing conditions (temperature and atmosphere) to obtain a sintered body of Example 1. First, the firing temperature T _s of the molded body was set to 1090 ° C., it was heated and cooling of the shaped body according to the following temperature profile, such as. That is, first, the molded body was heated so that the temperature of the molded body reached (T _s -40) ° C. Then, the compact was further heated so that the temperature of the compact reached the firing temperature (Ts), held at this temperature for 4 hours, and then the compact was cooled.

The atmosphere in the firing furnace during firing was as follows. First, firing was started in a vacuum (a vacuum state of 5 Pa or less) in the firing furnace. Then, when the molded body reaches (T _s -40) ° C., Ar gas is introduced into the firing furnace, and the pressure of Ar gas in the firing furnace is set to 80 kPa. Maintained. That is, in Example 1, when the compact reached (T _s −40) ° C., the firing atmosphere of the compact was switched from a vacuum atmosphere to an Ar atmosphere.

Next, the density (unit: g / cm ³ ) of the obtained sintered body was measured using the Archimedes method. Moreover, the magnetic characteristic (Hcj) of the sintered compact was measured using the BH tracer. Also, the content (unit: atomic%) of Nd in the sintered body is measured using fluorescent X-ray analysis, and the content of Nd in the sintered body and the content of Nd in the magnetic powder (the raw material alloy) (Hereinafter referred to as “Nd difference”). Table 1 shows the measurement results.

(Example 2)
In Example 2, when the temperature of the molded body reached (T _s -30) ° C., the firing atmosphere of the molded body was changed from the vacuum atmosphere to the Ar atmosphere in the same manner as in Example 1. A sintered body was obtained.

  And the density, Hcj, and Nd difference of the sintered compact of Example 2 were measured by the same method as Example 1. Table 1 shows the measurement results.

(Example 3)
In Example 3, when the temperature of the molded body was reached to (T _s -20) ° C, the firing atmosphere of the molded body was changed from the vacuum atmosphere to the Ar atmosphere in the same manner as in Example 1. A sintered body was obtained.

  And the density, Hcj, and Nd difference of the sintered compact of Example 3 were measured by the same method as Example 1. Table 1 shows the measurement results.

(Example 4)
In Example 4, the sintered body was obtained in the same manner as in Example 1 except that the firing atmosphere of the molded body was switched from the vacuum atmosphere to the Ar atmosphere when the temperature of the molded body reached T _s ° C. Obtained.

  And the density, Hcj, and Nd difference of the sintered compact of Example 4 were measured by the same method as Example 1. Table 1 shows the measurement results.

(Example 5)
In Example 5, after the temperature of the molded body was reached to T _s ° C. and maintained at this temperature for 30 minutes, the firing atmosphere of the molded body was changed from a vacuum atmosphere to an Ar atmosphere. In the same manner as in Example 1, a sintered body was obtained.

  And the density, Hcj, and Nd difference of the sintered compact of Example 5 were measured by the same method as Example 1. The results are shown in Table 1.

(Comparative Example 1)
In Comparative Example 1, the temperature of the molded body was made to reach T _s ° C, and when the temperature was maintained at this temperature for 50 minutes, the firing atmosphere of the molded body was changed from the vacuum atmosphere to the Ar atmosphere. In the same manner as in Example 1, a sintered body was obtained.

  Then, the density, Hcj, and Nd difference of the sintered body of Comparative Example 1 were measured by the same method as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
A sintered body of Comparative Example 2 was obtained in the same manner as in Example 1 except that firing was always performed in a vacuum atmosphere, that is, the firing atmosphere was not switched from a vacuum atmosphere to an Ar atmosphere.

  And the density, Hcj, and Nd difference of the sintered compact of the comparative example 2 were measured by the same method as Example 1. Table 1 shows the measurement results.

As shown in Table 1, in Examples 1 to 5, it was confirmed that the Nd difference was small compared to Comparative Examples 1 and 2. That is, in Examples 1-5, compared with Comparative Examples 1 and 2, it was confirmed that the variation in the composition of the molded body during firing was suppressed and the variation in magnetic properties was small. In Examples 1 to 5, it was confirmed that Hcj was higher than those in Comparative Examples 1 and 2. Furthermore, in any of Examples 1 to 5, it was confirmed that the density of the sintered body was maintained at 7.58 g / cm ³ or more, and the decrease in density was sufficiently suppressed.

It is a figure which shows an example of the temperature profile of the heating of the molded object performed at the temperature rising process with which the manufacturing method of the RTB type magnet which concerns on embodiment is equipped, and a temperature holding process.

Explanation of symbols

T _s ... Firing temperature, t ₁ ... Temperature raising step, before the temperature of the molded body reaches T _s C., t ₂ ... Temperature of the molded body is maintained at the firing temperature T _s C. And before 50 minutes.

Claims (4)

A molding step of forming a molded body from a magnetic material;
A temperature raising step of heating the shaped body to reach the firing temperature T _s ° C.
And a temperature holding step for holding the temperature of the molded body at T _s ° C.
In the Atsushi Nobori step or the temperature holding step, switching the atmosphere to an inert gas atmosphere from the vacuum atmosphere, and the switching of the the inert gas atmosphere from the vacuum atmosphere is performed in the following t ₁ after t ₂ previously, A method for producing an R-T-B magnet.
t ₁ : Time before the temperature of the molded body reaches T _s ° C. t ₂ : After the time t ₁ , the temperature of the molded body reaches T _s ° C., and is further maintained at T _s C. for 50 minutes. Time before Wherein t ₁ is the is the time at which to reach the (T s _-40) ℃ temperature of the molded body, method for manufacturing the R-T-B magnet according to claim 1. 3. The RT according to claim 1, wherein, in the temperature raising step, the temperature of the molded body is maintained at (T _s −40) ° C. for a predetermined time, and then the temperature of the molded body is reached to T _s C. -Manufacturing method of B type magnet. The manufacturing method of the RTB system magnet as described in any one of Claims 1-3 which makes the atmospheric pressure of the said inert gas atmosphere 50 Pa-80 kPa.