JPWO2019181249A1 - Manufacturing method of RTB-based sintered magnet - Google Patents

Abstract

A method for producing an RT-B-based sintered magnet having a predetermined composition and satisfying the formula (1), using a raw material Co having a maximum thickness of 2 mm or less, the RT- A step of producing an alloy satisfying the composition of the B-based sintered magnet, a step of producing an alloy powder from the alloy, a molding step of molding the alloy powder to obtain a molded body, and a step of sintering the molded body. A method for producing an RTB-based sintered magnet, which comprises a sintering step of obtaining a sintered body and a heat treatment step of applying a heat treatment to the sintered body. 14 [B] /10.8 <[T] /55.85 (1) ([B] is the content of B indicated by mass%, and [T] is T (T is Fe and Co) indicated by mass%. ) Content)

Description

The present disclosure relates to a method for manufacturing an RTB-based sintered magnet.

R-TB-based sintered magnets (R is at least one of rare earth elements and always contains Nd, T is at least one of transition metal elements and always contains Fe) are the highest among permanent magnets. Known as a high-performance magnet, it 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.

R-T-B based sintered magnet is mainly composed of a main phase consisting of R _{2 T} 14 _B compound, and the grain boundary phase located in the grain boundary of the main phase. The main phase, the R ₂ T ₁₄ B compound, is a ferromagnetic material with high magnetization and forms the basis of the characteristics of R-TB based sintered magnets.

In the _RTB -based sintered magnet, the coercive force H _cJ (hereinafter, may be simply referred to as "H _cJ ") decreases at a high temperature, so that irreversible thermal demagnetization occurs. Therefore, especially when used in a motor for an electric vehicle, it is required to have a high _HcJ even at a high temperature.

Conventionally, in order to improve _HcJ , a large amount of heavy rare earth element RH such as Dy and Tb has been added to the RTB-based sintered magnet. However, the addition of heavy rare-earth element RH in a large _{amount, H cJ} is improved, the residual magnetic flux density B _{r (hereinafter,} 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 of obtaining _cJ has been proposed.

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

Patent Document 1, as well as lower B weight than usual of the _{R-T-B-alloy, Al, Ga, R 2 Fe} 17 phase by the inclusion of one or more metal elements M selected from among Cu By ensuring a sufficient volume ratio of the transition metal rich phase (R ₆ T ₁₃ M) generated from the R ₂ Fe ₁₇ phase as a raw material, the content of Dy is suppressed and the coercive force of the magnetic force is maintained. It is described that a high RTB-based rare earth sintered magnet can be obtained.

In addition, as described above, _RTB -based sintered magnets are most often used in motors, and improving _HcJ is very effective in ensuring high-temperature stability, especially in motors for electric vehicles. However, along with these characteristics, the square ratio H _k / H _cJ (hereinafter, may be 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 is likely to occur. Therefore, an _RTB -based sintered magnet having a high H _cJ and a 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 is used at the position where J is 0.9 × J _r (J _r is the residual magnetization, J _r = _Br ). The value _obtained by dividing this H _k by the 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. 2013/0087756

In the RTB-based rare earth sintered magnet described in Patent Document 1, although a high _HcJ can be obtained while reducing the Dy content, a general _RTB -based sintered magnet (R) There is a problem that it is difficult to improve H _k / H _cJ as compared with (the amount of B is larger than the ratio of the chemical amount of the ₂ T ₁₄ B type compound). Specifically, in a general _RTB -based sintered magnet, H _k is a value of about 90% of H _cJ (that is, H _k / H _cJ is about 90%). In contrast, in the R-T-B rare earth magnet disclosed in Patent Document 1, since a high H _cJ are obtained, higher value of H _k than typical R-T-B based sintered magnet However, there was a problem that it was difficult to _increase H _k / H _cJ to 90% or more.

Therefore, an embodiment of the present invention provides a method for producing an _RTB -based sintered magnet having a high H _cJ and a high H _k while reducing the content of RH such as Dy and Tb. With the goal.

Aspect 1 of the present invention is
R: 28.5 to 33.0% by mass (R is at least one rare earth element and contains at least one of Nd and Pr),
B: 0.85 to 0.91% by mass,
Ga: 0.2 to 0.7% by mass,
Co: 0.1 to 0.9% by mass,
Cu: 0.05 to 0.50% by mass,
Al: 0.05 to 0.50% by mass, and Fe: 61.5% by mass or more,
A method for manufacturing an RTB-based sintered magnet that satisfies the following formula (1).

14 [B] /10.8 <[T] /55.85 (1)
([B] is the content of B represented by mass%, and [T] is the content of T (T is Fe and Co) represented by mass%).

A step of producing an alloy satisfying the composition of the RTB-based sintered magnet and a step of producing an alloy powder from the alloy using the raw material Co having a maximum thickness of 2 mm or less.
A molding process of molding the alloy powder to obtain a molded product,
A sintering step of sintering the molded body to obtain a sintered body,
A heat treatment step of heat-treating the sintered body and
It is a method for manufacturing an RTB-based sintered magnet including.

Aspect 2 of the present invention is the method for producing an RTB-based sintered magnet according to Aspect 1, wherein the maximum thickness of the raw material Co is 100 μm to 1 mm.

Aspect 3 of the present invention is the _{RTB according} to aspect 1 or 2, wherein the obtained _RTB -based sintered magnet satisfies H _cJ ≥ 1500 kA / m and H _k ≥ 1400 kA / m. This is a method for manufacturing a system sintered magnet.

Aspect 4 of the present invention is described in any one of Aspects 1 to 3, wherein Dy and Tb in R are 0% by mass or more and 0.5% by mass or less of the whole RTB-based sintered magnet. This is a method for manufacturing an RTB-based sintered magnet.

According to the manufacturing method according to the embodiment of the present invention, it is possible to manufacture an _RTB -based sintered magnet having a high H _cJ and a high H _k while reducing the RH content.

1 (a) is a schematic perspective view of a plate-shaped raw material Co, and FIG. 1 (b) is a projection drawing of the raw material Co from the direction of arrow 1A of FIG. 1 (a). Is a modification of FIG. 1 (b). FIG. 2A is a schematic perspective view of a plate-shaped raw material Co having a wedge shape on one side, and FIG. 2B is a projection drawing of the raw material Co from the direction of arrow 2A in FIG. 2A. is there. FIG. 3A is a schematic perspective view of a thin plate-shaped raw material Co bent in a wavy shape, and FIG. 3B is a schematic view of the raw material Co obtained by extending the raw material Co of FIG. 3A into a flat plate shape. It is a perspective view, and FIG. 3C is a projection drawing of the raw material Co from the direction of arrow 3A in FIG. 3B. FIG. 4A is a schematic enlarged perspective view of the granular raw material Co, and FIG. 4B is a projection drawing of the raw material Co from the direction of arrow 4A in FIG. 4A. 5 (a) is a schematic perspective view of the rod-shaped raw material Co, and FIG. 5 (b) is a projection drawing of the raw material Co from the direction of arrow 5A in FIG. 5 (a). 6 (a) is a schematic perspective view of the rod-shaped raw material Co, FIG. 6 (b) is a schematic sectional view taken along the line YY'of FIG. 6 (a), and FIG. 6 (c) is a schematic sectional view. It is a projection drawing of the raw material Co from the direction of arrow 6A of FIG. 6A. Figure 7 is a graph maximum thickness was plotted magnetic properties of the sintered magnet (H k _{-B r)} produced by using the raw material of Co 10 mm. Figure 8 is a graph maximum thickness was plotted magnetic properties of the sintered magnet (H k _{-B r)} produced by using the raw material of Co 2 mm. 9, the increase in H _k of the sintered magnet of changing the maximum thickness of the material Co from 10mm to 2 mm, is a graph plotting against B amount. FIG. 10 shows the sample No. For sintered magnet having a composition of 14, the maximum thickness of the material Co used is a graph plotting the H _k of the sintered magnet produced by using it. FIG. 11 shows the sample No. For sintered magnet having a 16 composition, the maximum thickness of the material Co used is a graph plotting the H _k of the sintered magnet produced by using it. FIG. 12 shows the sample No. For sintered magnet having a composition of 17, the maximum thickness of the material Co used is a graph plotting the H _k of the sintered magnet produced by using it. FIG. 13 shows the sample No. For sintered magnet having a composition of 18, the maximum thickness of the material Co used is a graph plotting the H _k of the sintered magnet produced by using it. FIG. 14 shows the sample No. For sintered magnet having a composition of 22, the maximum thickness of the material Co used is a graph plotting the H _k of the sintered magnet produced by using it.

The embodiments shown below exemplify a method for manufacturing an RTB-based sintered magnet for embodying the technical idea of the present invention, and the present invention is not limited to the following.

As a result of diligent studies, the present inventors have determined the form of the raw material Co in the production of RTB-based sintered magnets having a specific composition range as defined below, particularly a very narrow specific range of B content. It has been found that the magnetic properties of the finally obtained RTB-based sintered magnet can be improved by controlling the magnet.

As the raw material Co, those having a Co content of 50% by mass or more can be used. As a generally available raw material Co, a thin plate-shaped or block-shaped Co material is known. As the thin plate-shaped raw material Co, there is electrolytic Co produced by electrolysis, and the maximum thickness thereof is about 3 mm. As the block-shaped raw material Co, those having a thickness of 10 mm or more are available.
Since the raw material Co used as a raw material for a sintered magnet is completely melted during alloy production, it is considered unnecessary to thin or powder the commercially available raw material Co. It wasn't broken. However, the present inventors dare to maximize the production of RT-B-based sintered magnets having a specific composition range, particularly a very narrow specific range of B content, even if the raw material Co is dissolved. by processing a thickness up to 2 mm, in which found that the value of H _k of the sintered magnet of the final product can be greatly improved.
The manufacturing method according to the embodiment of the present invention will be described in detail below.

<RTB-based sintered magnet>
First, the RTB-based sintered magnet obtained by the manufacturing method according to the embodiment of 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: 28.5 to 33.0% by mass (R is at least one rare earth element and contains at least one of Nd and Pr),
B: 0.85 to 0.91% by mass,
Ga: 0.2 to 0.7% by mass,
Co: 0.1 to 0.9% by mass,
Cu: 0.05 to 0.50% by mass,
Al: 0.05 to 0.50% by mass, and Fe: 61.5% by mass or more,
The following equation (1) is satisfied.

14 [B] /10.8 <[T] /55.85 (1)
([B] is the content of B indicated by mass%, and [T] is the content of T indicated by mass%)

With the above composition, the amount of B is smaller than that of a general RT-B-based sintered magnet, and Ga and the like are contained, so that an RT-Ga phase is generated at the two-particle boundary. High H _cJ can be obtained. Here, the RT-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 type ₃ crystal structure. Further, 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, when the R-TB-based sintered magnet contains a relatively large amount of Cu and Al, it may be R ₆ T _13-δ (Ga _1-xy Cu _x Al _y ) _{1 + δ.} is there.
Each composition will be described in detail below.

(R: 28.5 to 33.0% by mass)
R is at least one of the rare earth elements and contains at least one of Nd and Pr. The content of R is 28.5 to 33.0% by mass. R is may become difficult to densification during sintering is less than 28.5% by mass may main phase proportion exceeds 33.0% by weight can not be obtained a high B _r drops .. The content of R is preferably 29.5 to 32.5% by mass. If R is in such a range, a higher _Br can be obtained.

R may contain RH such as Dy and Tb. However, in the embodiment of the present invention, the content of B, Ga, Co, etc. is controlled to reduce the content of RH, and the _RTB -based sintering has high H _cJ and high H _k. You can get a magnet. That is, according to the embodiment of the present invention, the content of RH, more specifically, the content of Dy and Tb (total content) may be suppressed to an extremely low level. Specifically, Dy and Tb in R may be 0% by mass or more and 0.5% by mass or less of the entire RTB-based sintered magnet. Here, "Dy and Tb in R" means that the content of Dy and Tb (0 to 0.5% by mass) is a part of the content of R (28.5 to 33.0% by mass). Means. Further, "0% by mass or more and 0.5% by mass or less of the entire RTB-based sintered magnet" means Dy and Tb when the entire RTB-based sintered magnet is 100% by mass. It means that the total content of is 0% by mass or more and 0.5% by mass or less.

In addition, Dy and Tb may contain only one or both. That is, when the total content of Dy and Tb is limited to 0 to 0.5% by mass, when Dy is contained but Tb is not contained (Tb content is 0% by mass), the Dy content is increased. It may be 0 to 0.5% by mass or less. Similarly, when Tb is contained but Dy is not contained (Dy content is 0% by mass), the Tb content may be 0 to 0.5% by mass or less. When both Dy and Tb are contained, the total content of the Dy content and the Tb content is 0 to 0.5% by mass or less.
Preferably, the total content of Dy and Tb is 0 to 0.3% by mass, and most preferably both Dy and Tb are not contained (the total content of Dy and Tb is 0% by mass).

(B: 0.85 to 0.91% by mass)
The content of B is 0.85 to 0.91% by mass. B is may not be obtained in a and _R 2 _{T 17} phase is produced by a high _{H cJ} than 0.85 wt%, little amount of generated more than 0.91 wt%, the R-T-Ga phase There is a risk that too high _HcJ cannot be obtained. The content of B is preferably 0.87 to 0.91% by mass, and a higher H _cJ improving effect can be obtained.

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

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

Here, [B] is the content of B represented by mass%, and [T] is the content of T represented by mass%. Note that T stands for Fe and Co. Therefore, [T] can be rewritten as follows.

[T] = [Fe] + [Co]

Here, [Fe] and [Co] are the contents of Fe and Co expressed in mass%, respectively.

By satisfying the formula (1), the content of B becomes smaller than that of a general RTB-based sintered magnet. Typical R-T-B based sintered magnet, the main phase _R 2 _{T 14} in addition to B phase as _R 2 _{T 17} phase is not generated corresponding to the soft magnetic phase, [T] /55.85 ( The atomic weight of Fe) is less than 14 [B] / 10.8 (atomic weight of B) ([T] is the content of T in mass%). The RTB-based sintered magnet of the embodiment of the present invention is different from a general RTB-based sintered magnet, and [T] /55.85 is higher than 14 [B] /10.8. It is specified by the formula (1) so that the number increases. 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 to 0.7% by mass)
The content of Ga is 0.2 to 0.7% by mass. If Ga is less than 0.2% by mass, the amount of R-T-Ga phase produced is too small, and the R ₂ T ₁₇ phase cannot be eliminated, and a high H _cJ may not be obtained. It will be present unnecessary Ga exceeds 0.7 weight%, there is a possibility that B _r decreases to decrease the main phase proportion.

(Co: 0.1 to 0.9% by mass)
The content of Co is 0.1 to 0.9% by mass. In the RTB-based sintered magnet of the embodiment of the present invention, the formation of R ₆ T ₁₃ B ₁ formed when the compact is sintered by adding Co can be suppressed, and the height is high. B _r, high _{H cJ,} a high _{H k} is obtained. However, if Co is less than 0.1% by mass, the formation of R ₆ T ₁₃ B ₁ cannot be suppressed and H _k may not be improved, and the Co content exceeds 0.9% by mass. When the molded body during sintering will be generated by the _R 2 _{T 17 phase, H cJ} and _{H k} may be reduced.

(Cu: 0.05 to 0.50% by mass)
The content of Cu is 0.05 to 0.50% by mass. If Cu is less than 0.05% by mass, high _HcJ may not be obtained, and if it exceeds 0.50% by mass, sinterability may deteriorate and high _HcJ may not be obtained.

(Al: 0.05 to 0.50% by mass)
The Al content is 0.05 to 0.50% by mass. H _cJ can be improved by containing Al. Al is usually contained in an amount of 0.05% by mass or more as an unavoidable impurity in the manufacturing process, but even if it is contained in an amount of 0.50% by mass or less in total of the amount contained as an unavoidable impurity and the amount intentionally added. Good.

(Fe: 61.5% by mass or more)
The content of Fe in the sintered magnet is 61.5% by mass or more, and is an amount satisfying the above-mentioned formula (1). When the content of Fe is less than 61.5% by mass may greatly _{B r} drops. Preferably, Fe is the balance.

Further, even when Fe is the balance, the RTB-based sintered magnet according to the embodiment of the present invention is used as an unavoidable impurity usually contained in didymium alloy (Nd-Pr), electrolytic iron, ferroboron and the like. It can contain Cr, Mn, Si, La, Ce, Sm, Ca, Mg and the like. Further, O (oxygen), N (nitrogen), C (carbon) and the like can be exemplified as unavoidable impurities in the manufacturing process. Further, the RTB-based sintered magnet according to the embodiment of the present invention may contain one or more other elements (elements intentionally added other than unavoidable impurities). For example, as such elements, a small amount (about 0.1% by mass of each) 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. Further, the elements listed as the above-mentioned unavoidable impurities may be intentionally added. Such elements may be contained, for example, about 1.0% by mass in total. With this degree, it is sufficiently possible to obtain an _RTB -based sintered magnet having a high H _cJ .

(Magnetic characteristics of RTB-based sintered magnets)
The _RTB -based sintered magnet according to the present embodiment _exhibits high H _cJ and high H _k . In particular, H _cJ is preferably ₁₅₀₀ kA / m or more, H _k is preferably ₁₄₀₀ kA / m or more, H cJ is more preferably ₁₅₂₀ kA / m or more, H _k is 1420 kA / m or more, and H _cJ is 1530 kA / m. m or more, more preferably _{H k} is 1425KA / m or _{more, H cJ} is 1550KA / m or more, and particularly preferably _{H k} is 1440KA / m or more. The above magnetic properties can also be achieved in an RTB-based sintered magnet in which the total content of Dy and Tb that can be contained in R (rare earth element) is 0.5% by mass or less.

<Manufacturing method of RTB-based sintered magnet>
Next, a method for manufacturing the RTB-based sintered magnet according to the present invention will be described.
The method for producing an RTB-based sintered magnet includes a step of producing an alloy, a step of producing an alloy powder, a molding step, a sintering step, and a heat treatment step.
Hereinafter, each step will be described.

(1) Step of Producing an Alloy A metal or alloy (dissolved raw material) of each element is prepared so as to have the composition of the RTB-based sintered magnet according to the embodiment of the present invention, and an alloy is produced. At this time, the raw material Co to be used is limited to a predetermined size, specifically, the maximum thickness is 2 mm or less. In general, it has been considered that H _cJ can be improved with a sintered magnet having a small amount of B as defined in the present application, but it is difficult to improve H _k . However, the present inventors have found that by using the alloy produced on that the maximum thickness of the material Co to 2mm or less, it has been found that the alloy pulverization, thereby improving the H _k of the sintered magnet obtained by sintering. In particular, it is preferable to control the maximum thickness of the raw material Co to 100 μm to 1 mm, and H _k can be remarkably improved.

Detailed mechanism capable of improving the H _k is unknown, by the maximum thickness of the material Co is limited to 2mm or less, dissolved starting materials Co uniformly and quickly when melting an alloy, its possible It is presumed that the H _k value of the finally obtained sintered magnet is improved, and thus the H _k / H _cJ (square ratio) is improved.

Here, the "maximum thickness" of the raw material Co is the thickest portion of the thickness of the raw material Co in the case of the raw material Co having a clear "thickness" such as a plate shape. ..
The maximum thickness of the raw material Co, which is not plate-shaped (that is, has a shape in which it is not clear which dimension is the thickness), is defined as follows.
In the projection drawing of the raw material Co projected so as to minimize the area, two parallel lines tangent to the projection drawing are drawn so as to sandwich the projection drawing. The angle of the parallel lines is variously changed, and the distance when the distance between the parallel lines is minimized becomes the maximum thickness of the raw material Co.

(Maximum thickness of Co plate 10)
The "maximum thickness" of the raw material Co in various forms will be described with reference to FIGS. 1 to 6. In the embodiment of the present invention, not only a plate-shaped material but also a particle-shaped, rod-shaped, linear or the like raw material Co can be used.
FIG. 1A is a schematic perspective view of a plate-shaped raw material Co (Co plate) 10. In the Co plate 10, the area of the projection drawing is minimized when projected from the direction of arrow 1A. FIG. 11 (b) shows a projection drawing 11 of the Co plate 10 projected from the direction of arrow 1A. In FIG. 1 (b), two parallel lines L _11a tangent to the projection drawing 11 are drawn so as to sandwich the projection drawing 11. Further, from another angle, two parallel lines L _11b tangent to the projection drawing 11 were drawn so as to sandwich the projection drawing 11. The distance T _1a between the first parallel lines L _11a and L _11a is shorter than the distance W _1a between the second parallel lines L _11b and L _11b . Therefore, the maximum thickness of the Co plate 10 is T _1a .

FIG. 1 (c) shows a modification of the projection drawing 11 of the Co plate 10 shown in FIG. 1 (b) when the surface is curved. As shown in FIG. 1 (c), in the projection drawing 12 of the Co plate having a curved surface, the outer line of the projection drawing 12 is curved. Two parallel lines L _12a tangent to the projection drawing 12 were drawn so as to sandwich the projection drawing 12. Further, from another angle, two parallel lines L _12b tangent to the projection drawing 12 were drawn so as to sandwich the projection drawing 12. The distance T _1b between the first parallel line L _12a and the parallel line L _12a is shorter than the distance W _1b between the second parallel lines L _12b and L _12b . Therefore, the maximum thickness of the Co plate 10 is T _1b .

(Maximum thickness of Co plate 20 having a wedge-shaped portion)
FIG. 2A is a schematic perspective view of a plate-shaped raw material Co (Co plate) 20 having a wedge-shaped shape (a blade shape whose thickness decreases toward the outside) on one side 25. In the Co plate 20, the area of the projection drawing is minimized when projected from the direction of arrow 2A. FIG. 21 (b) shows a projection drawing 21 of the Co plate 20 projected from the direction of arrow 2A. In FIG. 2B, two parallel lines L _2a tangent to the projection drawing 21 are drawn so as to sandwich the projection drawing 21. Further, from another angle, two parallel lines L _2b tangent to the projection drawing 21 were drawn so as to sandwich the projection drawing 21. Further, from another angle, two parallel lines L _2c tangent to the projection drawing 21 were drawn so as to sandwich the projection drawing 21. The distance T _2a between the first parallel lines L _2a and L _2a is the distance W ₂ between the second parallel lines L _2b and L _2b and the distance between the third parallel lines L _2c and L _2c. Shorter than Y ₂ . Therefore, the maximum thickness of the Co plate 20 is T _2a .

The "thickness" in the projection drawing 21 shown in FIG. 2B includes not only the thickness T _2a but also the thickness of the wedge-shaped portion (for example, the thicknesses T _2b and T _2c ). However, the "maximum thickness" in the embodiment of the present invention is T _2a , which is the thickest of those thicknesses. This is because the meltability of the raw material Co is considered to be important, and even if it is partially thin, the thick portion has the greatest effect.

(Maximum thickness of Co corrugated sheet 30)
FIG. 3A is a schematic perspective view of a thin plate-shaped raw material Co (Co corrugated plate) 30 bent in a wavy shape. In the case of such a curved raw material Co, first, it is stretched and flattened. In the case of the Co corrugated plate 30, one end 30a is pulled in the direction Xa and the other end 30b is pulled in the direction Xb to extend into a flat plate shape as shown in FIG. 3 (b) (this is referred to as "Co extension plate 35"). Call). The maximum thickness obtained by the Co extension plate 35 is the maximum thickness of the Co corrugated plate 30.

In the Co extension plate 35 shown in FIG. 3B, the area of the projection drawing is minimized when projected from the direction of arrow 3A. A projection drawing 31 of the Co extension plate 35 projected from the direction of arrow 3A is shown in FIG. 3 (c). In FIG. 3C, two parallel lines _L3a tangent to the projection drawing 31 are drawn so as to sandwich the projection drawing 31. Further, from another angle, two parallel lines L _3b tangent to the projection drawing 31 were drawn so as to sandwich the projection drawing 31. The distance T ₃ between the first parallel lines L _3a and L _3a is shorter than the distance W ₃ between the second parallel lines L _3b and L _3b . Therefore, the maximum thickness of the Co extension plate 35 and extension before Co-wave plate 30 are both _{T 3.}

As described above, the maximum thickness of the Co corrugated plate 30 is determined in the state of the Co extension plate 35 for the following reasons. When the maximum thickness is determined in the state of the Co corrugated sheet 30, the distance between the curved peak (upper end) and the valley (lower end) becomes the "maximum thickness". However, in the embodiment of the present invention, the maximum thickness is used as an index of the meltability of the raw material Co. If the curved sheet is made of thin sheet, it should show the same meltability as the uncurved sheet. Therefore, in the embodiment of the present invention, the maximum thickness of the Co corrugated plate 30 is determined in the state of the Co extension plate 35.

(Maximum thickness of Co particle 40)
FIG. 4A is a schematic perspective view of the granular raw material Co (Co particles). In the Co particle 40, the area of the projection drawing is minimized when projected from the direction of arrow 4A. FIG. 4 (b) shows a projection drawing 41 of the Co particle 40 projected from the direction of arrow 4A. In FIG. 4B, two parallel lines _L4a tangent to the projection drawing 41 are drawn so as to sandwich the projection drawing 41. Further, from another angle, two parallel lines _L4b tangent to the projection drawing 41 were drawn so as to sandwich the projection drawing 41. Further, from another angle, two parallel lines L _4c tangent to the projection drawing 41 were drawn so as to sandwich the projection drawing 41. The distance T _4a between the first parallel lines L _4a and L _4a is the distance W ₄ between the second parallel lines L _4b and L _4b and the distance between the third parallel lines L _4c and L _4c. shorter than the Y _4. Therefore, the maximum thickness of the Co plate 20 is T _4a .

The "thickness" in the projection drawing 41 shown in FIG. 4 (b) includes not only the thickness T _4a but also the thickness of the constricted portion of the Co particles 40 (for example, the thicknesses T _4b and T _4c ). It can be. However, the "maximum thickness" in the embodiment of the present invention is T _4a , which is the thickest of those thicknesses.

(Maximum thickness of Co bar 50)
FIG. 5A is a schematic perspective view of a rod-shaped raw material Co (Co rod). In the Co bar 50, the area of the projection drawing is minimized when projected from the direction of arrow 5A. FIG. 5 (b) shows a projection drawing 51 of the Co bar 50 projected from the direction of arrow 5A. In FIG. 5B, two parallel lines L _5a tangent to the projection drawing 51 are drawn so as to sandwich the projection drawing 51. Further, from another angle, two parallel lines L _5b tangent to the projection drawing 51 were drawn so as to sandwich the projection drawing 51. The distance T _5a between the first parallel lines L _5a and L _5a is shorter than the distance T _5b between the second parallel lines L _5b and L _5b . Therefore, the maximum thickness of the Co bar 50 is T _5a .
The maximum thickness of such a bar corresponds to the minor diameter in the cross-sectional view of the bar.

(Maximum thickness of Co bar 60 with constriction)
FIG. 6A is a schematic perspective view of a rod-shaped raw material Co (constricted Co bar) whose diameter is partially reduced (that is, partially constricted). As shown in FIG. 6 (b), the cross section of the constricted portion 65 of the Co bar 60 (Y-Y 'line), minor _{T 6b} of the constricted portion 65, the minor axis _{T 6a} having no constricted portion 66 It becomes smaller.
However, the constricted portion is not reflected in the projection drawing 61 (FIG. 6C) of the Co bar 60 projected from the direction of the arrow 6A where the area of the projection drawing is minimized. Thus, in FIG. 6 (c), the parallel lines _{L 6a} in contact with the projection drawing 61, subtract two so as to sandwich the projection view 61, the parallel lines _{L 6a,} the distance _{T 6a} between the _{L 6a,} as shown in FIG. 6 This is consistent with the "minor diameter T _6a of the non-constricted portion 66" shown in (b). Then, the parallel lines _{L 6a,} the distance _{T 6a} between the _{L 6a} becomes the maximum thickness of the Co bar 60.

An alloy is produced by melting the raw material Co having a maximum thickness of 2 mm or less and the raw materials of other components defined in this way. The alloy can be flaked, for example, by a strip casting method or the like.

(2) Step of Producing Alloy Powder In this step, the alloy obtained in the above step (1) is crushed to prepare an alloy powder.
For example, the obtained alloy (for example, a flake-shaped raw material alloy) is hydrogen-pulverized, and the size of the coarsely pulverized powder is, for example, 1.0 mm or less. Next, by finely pulverizing the coarsely pulverized powder with a jet mill or the like, for example, the finely pulverized powder (alloy) having a particle size D ₅₀ (value obtained by laser diffraction method by the air flow dispersion method (median diameter)) of 3 to 7 μm Powder) is obtained. A known lubricant may be used as an auxiliary agent for the coarse pulverized powder before jet mill pulverization and the alloy powder during jet mill pulverization and after jet mill pulverization.

(3) Molding process Molding is performed in a magnetic field using the obtained alloy powder to obtain a molded product. Molding in a magnetic field is a dry molding method in which a dry alloy powder is inserted into a cavity of a mold and molded while applying a magnetic field, and a slurry in which the alloy powder is dispersed is injected into the cavity of the mold. Any known in-magnetic field molding method may be used, including a wet molding method of molding while discharging the dispersion medium of the slurry.

(4) Sintering Step A sintered body (sintered magnet) is obtained by sintering the molded product obtained in the molding process. A known method can be used for sintering the molded product. In addition, in order to prevent oxidation due to the atmosphere at the time of sintering, it is preferable to perform sintering in a vacuum atmosphere or an atmospheric gas. As the atmospheric gas, it is preferable to use an inert gas such as helium or argon.

(5) Heat Treatment Step It is preferable to heat-treat the obtained sintered magnet for the purpose of improving the magnetic characteristics. Known conditions can be used for the heat treatment temperature, heat treatment time, and the like. For example, heat treatment (one-step heat treatment) may be performed only at a relatively low temperature (400 ° C. or higher and 600 ° C. or lower), or heat treatment may be performed at a relatively high temperature (700 ° C. or higher and sintering temperature or lower (for example, 1050 ° C. or lower)). After that, heat treatment (two-stage heat treatment) may be performed at a relatively low temperature (400 ° C. or higher and 600 ° C. or lower). Preferred conditions are heat treatment at 730 ° C. or higher and 1020 ° C. or lower for about 5 to 500 minutes, after cooling (after cooling to room temperature or cooling to 440 ° C. or higher and 550 ° C. or lower), and further at 440 ° C. or higher and 550 ° C. or lower. Heat treatment may be performed for about 1 to 500 minutes. The heat treatment atmosphere is preferably a vacuum atmosphere or an inert gas (helium, argon, etc.).

The obtained sintered magnet may be machined by grinding or the like for the purpose of forming the final product shape. In that case, the heat treatment may be performed before or after machining. Further, the obtained sintered magnet may be surface-treated. The surface treatment may be a known surface treatment, and for example, surface treatment such as Al vapor deposition, electric Ni plating, or resin paint can be performed.

The sintered magnet thus obtained had a high H _cJ and a high H _k , and had a high square ratio.

The composition of the RTB-based sintered magnet is approximately No. 1 in Table 1. The raw materials of each element were blended so as to have each composition shown in 1 to 23. At this time, the raw material Co is Co metal, and the maximum thickness is 10 mm (cube), 4 mm (cube), 2 mm (plate shape), 1 mm (rod shape), 425 μm (particle shape), 100 μm (powder shape), 5 μm ( Fine powder) was used. The raw material Co of each dimension was prepared by cutting from a block-shaped Co material. The raw material Co having a maximum thickness of 10 mm (cube) and 2 mm (plate shape) is the sample No. in Table 1. Used to produce all alloys with compositions 1-23, other raw materials Co (4 mm (cube), 1 mm (rod), 425 μm (particulate), 100 μm (powder), 5 μm (fine powder) )) Is the sample No. It was used only in the production of alloys having compositions of 14, 16-18, 22.

The blended raw materials were melted and cast by a strip casting method to obtain a flake-shaped alloy having a thickness of 0.2 to 0.4 mm. The obtained flake-shaped alloy was hydrogen embrittled in a hydrogen-pressurized atmosphere, and then dehydrogenated by heating and cooling in a vacuum up to 550 ° C. to obtain coarsely pulverized powder. Next, 0.04% by mass of zinc stearate was added and mixed as a lubricant with respect to 100% by mass of the coarsely crushed powder to the obtained coarsely pulverized powder, and then an air flow type crusher (jet mill device) was used. It was dry-pulverized in a nitrogen stream to obtain a finely pulverized powder (alloy powder) having a particle size D ₅₀ (median diameter) of 4 μm. The oxygen concentration in the nitrogen gas during pulverization was controlled to 50 ppm or less. The particle size D ₅₀ is a value obtained by a laser diffraction method based on an air flow dispersion method.

The obtained alloy powder was mixed with a dispersion medium to prepare a slurry. Normal dodecane was used as the dispersion medium, and methyl caprylate was mixed as a lubricant. The concentration of the slurry was 70% by mass of the alloy powder and 30% by mass of the dispersion medium, and the lubricant was 0.16% by mass with respect to 100% by mass of the alloy powder. The slurry was molded in a magnetic field to obtain a molded product. The magnetic field at the time of molding was a static magnetic field of 0.8 MA / m, and the pressing force was 5 MPa. As the molding apparatus, a so-called right-angle magnetic field forming apparatus (transverse magnetic field forming apparatus) in which the magnetic field application direction and the pressurizing direction are orthogonal to each other was used.

The obtained molded product was sintered in vacuum at 1000 ° C. or higher and 1050 ° C. or lower (selecting a temperature at which sufficient densification by sintering occurs for each sample) for 4 hours, and then rapidly cooled to obtain a sintered body. The density of the obtained sintered body was 7.5 Mg / m ³ or more. The obtained sintered body was held in vacuum at 800 ° C. for 2 hours and then cooled to room temperature, then kept in vacuum at 430 ° C. for 2 hours and then subjected to a heat treatment to be cooled to room temperature. Sintered magnets (No. 1 to 23) were obtained. Table 1 shows the components of the obtained RTB-based sintered magnet. Each component (other than O, N and C) in Table 1 was measured using high frequency inductively coupled plasma emission spectroscopy (ICP-OES). The O (oxygen) content is the gas melting-infrared absorption method, the N (nitrogen) content is the gas melting-heat conduction method, and the C (carbon) content is the combustion-infrared absorption method. Used and measured.

Table 2 shows the B amount, T amount (total of Co amount and Fe amount), the value of the left side (14 [B] / 10.8) of the formula (1), and the value of the right side ([T] / 55.85). The value is shown. Table 2 also shows the satisfiability of equation (1). Here, "○" means that the equation (1) is satisfied, and "x" means that the equation (1) is not satisfied.

The heat-treated RTB-based sintered magnets (Sample Nos. 1 to 23) are machined to prepare samples with a length of 7 mm, a width of 7 mm, and a thickness of 7 mm, and are prepared at room temperature (20) by a BH tracer. ℃ ± at 10 ° C.) the magnetic properties of each sample _{(B r, H cJ, H} k, were measured _H k _/ H _cJ). The measurement results are shown in Table 3. In H _k / H _cJ (square ratio), H _k is 0.9 × J _r (J _r ) in the second quadrant of the I (magnetization magnitude) −H (magnetic field strength) curve. It is the value of H at the position where the residual magnetization, _Jr = _Br ).
Sample No. using raw material Co having various maximum thicknesses. The measurement results of the magnetic properties of 14, 16 to 18 and 22 are shown in Tables 4 to 6.

Sample No. 1 to 12 do not satisfy the regulation of the composition of the sintered magnet according to the embodiment of the present invention. Sample No. For 1, 2, 4 to 5, 7 to 10, the amount of B does not satisfy the provisions of the present invention. Sample No. In Nos. 6 and 11, the amount of Ga does not satisfy the provisions according to the embodiment of the present invention. Sample No. In No. 12, the amount of Co does not satisfy the provision according to the embodiment of the present invention. In addition, sample No. Nos. 1, 3, 5, 8 and 10 do not satisfy the provisions of the formula (1). As can be seen from Table 3, most of these samples tend to have relatively low H _cJ values at any of the maximum thicknesses of the raw material Co, 10 mm and 2 mm.

Sample No. 13 to 23 satisfy all the provisions of the composition of the sintered magnet according to the embodiment of the present invention. Therefore, the sample No. In 13 to ₂₃ , the values of H _cJ are relatively high _regardless of the maximum thickness of the raw material Co of 10 mm and 2 mm (Table 3).

In each sample, the relationship between H _k and the maximum thickness of the raw material Co will be considered. Figure 7 is a graph maximum thickness was plotted magnetic properties of the sintered magnet (H k _{-B r)} produced by using the raw material of Co 10 mm. Figure 8 is a graph maximum thickness was plotted magnetic properties of the sintered magnet (H k _{-B r)} produced by using the raw material of Co 2 mm. In FIGS. 7 and 8, the symbol “x” indicates the sample No. Data from 1 to 12 are plotted, and the symbol "●" indicates the sample No. It is a plot of the data of 13 to 23.

As can be seen from FIG. 7, when the maximum thickness of the raw material Co is 10 mm, the sample No. 12, none of the samples 13 to 23, _{H k} of the obtained sintered magnet had become less than 1400kA / m.
On the other hand, as shown in FIG. 8, when the maximum thickness of the raw material Co is 2 mm, the sample No. In 1 to 12, the H _k of the obtained sintered magnet remained less than 1400 kA / m, but in samples 13 to 23, the H _k of the obtained sintered magnet was 1400 kA / m or more. ..

In each sample, the amount of increase _{H k} when changing the maximum thickness of the material Co from 10mm to 2 mm _{(i.e., H k (2mm) -H k} (10mm)) shown in Table 3. “H _k (10 mm)” and “H _k (2 mm)” in Table 3 and the like mean the values of H _k of the sintered magnet manufactured by using the raw material Co having a maximum thickness of 10 mm and 2 mm, respectively. Further, in FIG. 9, the amount of increase in H _k was plotted against the amount B.

As is clear from FIG. 9, in the case of a sintered magnet (Sample Nos. 13 to 23) having a B amount of 0.85 to 0.91 mass%, H is set by setting the maximum thickness of the raw material Co to 2 mm or less. The value of _k increased by 80 kA / m or more to 1400 kA / m or more.
On the other hand, in the case of a sintered magnet (Sample Nos. 1 to 12) in which the amount of B is less than 0.85% by mass or more than 0.91% by mass, even if the maximum thickness of the raw material Co is limited to 2 mm or less, H The amount of increase in _k was less than 10 kA / m, and there was almost no increase.

As described above, the sample No. that satisfies the regulation of the composition of the sintered magnet according to the embodiment of the present invention. In Nos. 13 to 23, by limiting the maximum thickness of the raw material Co used in production to 2 mm or less, it is possible to have excellent magnetic characteristics such as H _cJ of 1500 kA / m or more and H _k of 1400 kA / m or more. Do you get it. In particular, the effect of limiting the maximum thickness of the raw material Co was remarkable when the amount of B was 0.85 to 0.91% by mass.

Furthermore, the sample No. Taking a sintered magnet having a composition of 14, 16 to 18 and 22 as an example, the influence on H _k when the raw material Co having various maximum thicknesses was used was investigated. Table 4 shows the sample numbers produced using the raw material Co having a maximum thickness of 10 mm and 4 mm. The measurement results of the magnetic properties of the sintered magnets of 14, 16 to 18 and 22 are shown. Table 5 shows the sample numbers produced using the raw material Co having a maximum thickness of 2 mm and 1 mm. The measurement result of the magnetic property of 16 sintered magnets is shown. Table 6 shows the sample numbers prepared using the raw materials Co having a maximum thickness of 425 μm, 100 μm, and 5 μm. The measurement results of the magnetic properties of the sintered magnets of 14, 16 to 18 and 22 are shown. Further, in FIGS. 10 to 14, the sample No. For each 14,16～18,22, the maximum thickness of the material Co, was plotted _{H k} of the sintered magnet produced by using the raw material Co.

As shown in FIG. 10, the sample No. Regarding No. 14, in the sintered magnet manufactured by using the raw material Co having a maximum thickness of 2 mm or less, H _k was 1420 kA / m or more. Furthermore, the maximum thickness when using raw materials of Co 100μm~2mm, _{H k} of the sintered magnet obtained became 1425kA / m or more.

As shown in FIG. 11, the sample No. Regarding No. 16, in the sintered magnet manufactured by using the raw material Co having a maximum thickness of 2 mm or less, H _k was 1440 kA / m or more. Furthermore, the maximum thickness when using raw materials of Co 100μm~1mm, _{H k} of the sintered magnet obtained became 1460kA / m or more.

As shown in FIG. 12, the sample No. Regarding No. 17, in the sintered magnet manufactured by using the raw material Co having a maximum thickness of 2 mm or less, H _k was 1460 kA / m or more. Furthermore, the maximum thickness when using raw materials of Co 100μm~1mm, _{H k} of the sintered magnet obtained became 1480kA / m or more.

As shown in FIG. 13, the sample No. Regarding No. 18, in the sintered magnet manufactured by using the raw material Co having a maximum thickness of 2 mm or less, H _k was 1465 kA / m or more. Furthermore, the maximum thickness when using raw materials of Co 100μm~1mm, _{H k} of the sintered magnet obtained became 1485kA / m or more.

As shown in FIG. 14, the sample No. Regarding 22, in the sintered magnet manufactured by using the raw material Co having a maximum thickness of 2 mm or less, H _k was 1400 kA / m or more. Furthermore, the maximum thickness when using raw materials of Co 100μm~1mm, _{H k} of the sintered magnet obtained became 1420kA / m or more.

From the results of FIG. 10 to 14, by the maximum thickness of the material Co is to 2mm or less, it is possible to improve the _{H k,} by further maximum thickness of the material Co is to 100Myuemu～1mm, the _{H k} It turned out that it could be improved further.

This application is filed in Japanese Patent Application No. 2018-056846 with a filing date of March 23, 2018 and Japanese Patent Application No. 2018-182366 with a filing date of September 27, 2018. Accompanied by a priority claim with the issue as the basic application. Japanese Patent Application No. 2018-056846 and Japanese Patent Application No. 2018-182636 are incorporated herein by reference.

10, 20, 30, 40, 50, 60 Raw material Co
T _1a , T _1b , T _2a , T ₃ , T _4a , T _5a , T _6a Maximum thickness of raw material Co

Claims (4)

R: 28.5 to 33.0% by mass (R is at least one rare earth element and contains at least one of Nd and Pr),
B: 0.85 to 0.91% by mass,
Ga: 0.2 to 0.7% by mass,
Co: 0.1 to 0.9% by mass,
Cu: 0.05 to 0.50% by mass,
Al: 0.05 to 0.50% by mass,
Fe: 61.5% by mass or more,
A method for manufacturing an RTB-based sintered magnet that satisfies the following formula (1).

14 [B] /10.8 <[T] /55.85 (1)
([B] is the content of B represented by mass%, and [T] is the content of T (T is Fe and Co) represented by mass%).

A step of producing an alloy satisfying the composition of the RTB-based sintered magnet using the raw material Co having a maximum thickness of 2 mm or less, and
The process of producing alloy powder from the alloy and
A molding process of molding the alloy powder to obtain a molded product,
A sintering step of sintering the molded body to obtain a sintered body,
A heat treatment step of heat-treating the sintered body and
A method for producing an RTB-based sintered magnet, which comprises. The method for producing an RTB-based sintered magnet according to claim 1, wherein the maximum thickness of the raw material Co is 100 μm to 1 mm. The _{production of the RTB} -based sintered magnet according to claim 1 or 2, wherein the obtained _RTB -based sintered magnet satisfies H _cJ ≧ 1500 kA / m and H _k ≧ 1400 kA / m. Method. The R-TB according to any one of claims 1 to 3, wherein Dy and Tb in R are 0% by mass or more and 0.5% by mass or less of the entire R-TB-based sintered magnet. A method for manufacturing a system sintered magnet.

Images