阅读说明：本技术 R－t－b系烧结磁体 (R-T-B sintered magnet ) 是由 石井伦太郎 国吉太 于 2020-03-12 设计创作，主要内容包括：本发明提供一种尽量不使用重稀土元素RH、在高温(例如100℃)下也具有高矫顽力H<Sub>cJ</Sub>的R－T－B系烧结磁体。该R－T－B系烧结磁体含有：R：28.5质量％以上33.0质量％以下(R为稀土元素中的至少1种,含有Nd和Pr中的至少1种)；B：0.85质量％以上0.91质量％以下；Ga：0.35质量％以上0.75质量％以下；Cu：0.05质量％以上0.50质量％以下；Mn：0.03质量％以上0.15质量％以下；T：61.5质量％以上70.0质量％以下(T为Fe或Fe和Co,T的90质量％以上为Fe),满足式(1)：14[B]/10.8＜[T]/55.85,([B]为以质量％表示的B含量,[T]为以质量％表示的T含量)。(The invention provides a high coercive force H at high temperature (for example, 100 ℃) without using heavy rare earth element RH as much as possible cJ The R-T-B sintered magnet of (1). The R-T-B sintered magnet comprises: r: 28.5 to 33.0 mass% (R is at least 1 of rare earth elements and contains at least 1 of Nd and Pr); b: 0.85 mass% or more and 0.91 mass% or less; ga: 0.35 to 0.75 mass%; cu: 0.05 to 0.50 mass%; mn: 0.03 to 0.15 mass% inclusiveThe following steps of (1); t: 61.5 to 70.0 mass% (T is Fe or Fe and Co, and 90 mass% or more of T is Fe) and satisfies formula (1): 14[ B ]]/10.8＜[T]/55.85，([B]Is the B content in mass% [ T ]]Is the T content in mass%).)

1. An R-T-B sintered magnet, comprising:

r: 28.5 to 33.0 mass%, wherein R is at least 1 of rare earth elements and contains at least 1 of Nd and Pr;

b: 0.85 mass% or more and 0.91 mass% or less;

ga: 0.35 to 0.75 mass%;

cu: 0.05 to 0.50 mass%;

mn: 0.03 to 0.15 mass%;

t: 61.5 to 70.0 mass%, wherein T is Fe or Fe and Co, and at least 90 mass% of T is Fe,

the R-T-B sintered magnet satisfies the following formula (1):

14[B]/10.8＜[T]/55.85 (1)，

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

2. The R-T-B based sintered magnet according to claim 1, wherein:

apart from unavoidable impurities, does not contain heavy rare earths, H being at 100 DEG C_cJNot less than 880kA/m and B at 22.5 DEG C_r≥1.32T。

3. The R-T-B based sintered magnet according to claim 1, wherein:

containing Tb at 1.0 mass% or less and H at 100 deg.C_cJ≥880+168[Tb]kA/m and B at 22.5 DEG C_r≥1.32－0.024[Tb]T, wherein [ Tb ]]Is the content of Tb in mass%.

Technical Field

The present invention relates to an R-T-B sintered magnet.

Background

R-T-B sintered magnet (R is rare earth)At least 1 of the soil elements contains at least 1 of Nd and Pr; t is Fe or Fe and Co, and 90% by mass or more of T is Fe) is composed of a metal having R₂T₁₄The main phase of the compound having the B-type crystal structure and a grain boundary phase located in a grain boundary portion of the main phase are known as magnets having the highest performance among permanent magnets.

Therefore, the present invention is used in various applications such as various motors including a Voice Coil Motor (VCM) of a hard disk drive, a motor for electric vehicles (EV, HV, and PHV), a motor for industrial equipment, and home electric appliances.

With such an expansion in use, for example, when used in an electric motor for an electric vehicle, the electric motor is sometimes exposed to a high temperature of, for example, about 100 ℃.

However, the R-T-B sintered magnet has a coercive force H at a high temperature_cJ(hereinafter sometimes abbreviated as "H_cJ") decreases, the problem of irreversible thermal demagnetization occurs. For example, when R-T-B sintered magnets are used in motors for electric vehicles, H may be caused by use at high temperatures_cJThe motor is lowered and stable operation of the motor cannot be realized. Therefore, it is required to have high H also at high temperature_cJThe R-T-B sintered magnet of (1).

To increase H_cJConventionally, a sintered R-T-B magnet has been produced by adding a heavy rare earth element RH (mainly Dy) to the magnet, but the magnet has a residual magnetic flux density B_r(hereinafter sometimes abbreviated as "B_r") reduced. Further, there is a problem that supply is unstable and price fluctuates greatly due to reasons such as limited production area of Dy. Therefore, it is required to increase the H content of R-T-B sintered magnets without using as much as possible a heavy rare earth element RH such as Dy_cJThe technique of (1).

As such a technique, for example, patent document 1 discloses a technique of producing R by reducing the content of B as compared with a general R-T-B sintered magnet and containing 1 or more metal elements M selected from Al, Ga and Cu₂T₁₇Phase, sufficiently secured with the R₂T₁₇The phase is a transition metal-rich phase (R-T-Ga phase), the content of Dy can be suppressed, and an R-T-B sintered magnet having a high coercive force can be obtained.

Disclosure of Invention

Technical problem to be solved by the invention

However, the R-T-B sintered magnet described in patent document 1 has an increased H content_cJBut is insufficient to meet the recent requirements.

To this end, the invention provides a composition which, as far as possible, does not use heavy rare earth elements RH and which has a high coercivity H even at high temperatures (for example 100 ℃ C.)_cJThe R-T-B sintered magnet of (1).

Technical solution for solving technical problem

In an exemplary embodiment, the R-T-B sintered magnet of the present invention includes:

r: 28.5 to 33.0 mass% (R is at least 1 of rare earth elements and contains at least 1 of Nd and Pr);

b: 0.85 mass% or more and 0.91 mass% or less;

ga: 0.35 to 0.75 mass%;

cu: 0.05 to 0.50 mass%;

mn: 0.03 to 0.15 mass%;

t: 61.5 to 70.0 mass% (T is Fe or Fe and Co, 90 mass% or more of T is Fe),

the R-T-B sintered magnet satisfies the following formula (1):

14[B]/10.8＜[T]/55.85 (1)，

([ B ] is the content of B in mass%, and [ T ] is the content of T in mass%).

In one embodiment, the R-T-B sintered magnet does not contain heavy rare earth elements (except inevitable impurities), and is H at 100 ℃_cJNot less than 880kA/m and B at 22.5 DEG C_r≥1.32T。

In one embodiment, the R-T-B sintered magnet contains 1.0 mass% or less of Tb and H at 100 ℃_cJ≥880+168[Tb]kA/m and B at 22.5 DEG C_r≥1.32－0.024[Tb]T，([Tb]As the content of Tb in mass%).

ADVANTAGEOUS EFFECTS OF INVENTION

According to the embodiment of the present invention, it is possible to provide a high coercive force H at a high temperature (for example, 100 ℃) without using the heavy rare earth element RH as much as possible_cJThe R-T-B sintered magnet of (1).

Drawings

FIG. 1 shows Mn content and H at 100 ℃ for Nos. 1 to 10 of Experimental example 1_cJAn explanatory diagram of the relationship of (1).

Detailed Description

As a result of intensive studies, the inventors of the present invention have found that the R-T-B sintered magnet of the present invention having specific R, B, Ga and Cu contents, particularly, a B content in a very narrow specific range can have a high H content even at high temperatures by further containing Mn in a specific range_cJ. This is considered to be because the temperature coefficient can be improved by further containing Mn in the R-T-B-based sintered magnet in which the amount of B is within the specific composition range of the present invention.

[ R-T-B sintered magnet ]

The R-T-B sintered magnet of the present invention comprises:

r: 28.5 to 33.0 mass% (R is at least 1 of rare earth elements and contains at least 1 of Nd and Pr);

b: 0.85 mass% or more and 0.91 mass% or less;

ga: 0.35 to 0.75 mass%;

cu: 0.05 to 0.50 mass%;

mn: 0.03 to 0.15 mass%;

t: 61.5 to 70.0 mass% (T is Fe or Fe and Co, 90 mass% or more of T is Fe),

the R-T-B sintered magnet satisfies the following formula (1):

14[B]/10.8＜[T]/55.85 (1)

([ B ] is the content of B in mass%, and [ T ] is the content of T in mass%).

Hereinafter, each composition is described in detail.

(R: 28.5 to 33.0 mass%)

R is at least 1 of rare earth elements and contains at least 1 of Nd and Pr. The content of R is 28.5 to 33.0 mass%. When the content of R is less than 28.5 mass%, densification at sintering may become difficult, and when it exceeds 33.0 mass%, the main phase ratio decreases, and B_rPossibly reduced. The content of R is preferably 29.5 to 32.5 mass%. When R is in this range, a higher B content can be obtained_r。

(B: 0.85-0.91 mass%)

The content of B is 0.85-0.91 mass%. By including B in the R-T-B sintered magnet within the range of the present invention and further including Mn in a specific range described later, the temperature coefficient is improved and high H can be obtained even at high temperatures_cJ. Therefore, when the content of B is less than 0.85 mass% or exceeds 0.91 mass%, high H cannot be obtained at high temperature_cJ. Wherein a part of B may be substituted with C.

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

14[B]/10.8＜[T]/55.85(1)。

by satisfying the formula (1), the content of B is less than that of a general R-T-B system sintered magnet. In a general R-T-B sintered magnet, R is used as a main phase₂T₁₄R as a soft magnetic phase is not generated except for the B phase₂T₁₇Phase, [ T ]]/55.85 (atomic weight of Fe) less than 14[ B]Composition ([ T ] of 10.8 (atomic weight of B))]Is the content of T in mass%). The R-T-B sintered magnet of the present invention is different from a general R-T-B sintered magnet in that [ T ] is defined by the formula (1)]55.85 is greater than 14[ B ]]/10.8. In the R-T-B sintered magnet of the present invention, the main component of T is Fe, so that the atomic weight of Fe is used.

(Ga 0.35-0.75 mass%)

The content of Ga is 0.35-0.75 mass%. When the content of Ga is less than 0.35% by mass, the temperature coefficient cannot be improved, and high H cannot be obtained at high temperatures_cJ. In addition, the amount of R-T-Ga phase produced is reduced, and R cannot be made₂T₁₇Phase disappearance may result in failure to obtain high H at room temperature_cJ. When the content of Ga exceeds 0.75 mass%, the main phase ratio decreases due to the presence of unnecessary Ga, and B_rPossibly reduced.

(Cu: 0.05-0.50 mass%)

The Cu content is 0.05-0.50 mass%. If the Cu content is less than 0.05 mass%, high H may not be obtained at room temperature or high temperature_cJIf the content exceeds 0.50% by mass, the sinterability may be deteriorated, and high H may not be obtained at room temperature or high temperature_cJ。

(Mn: 0.03-0.15 mass%)

The Mn content is 0.03 to 0.15 mass%. By limiting the content of B to the above range and further containing 0.03 to 0.15 mass% of Mn, the temperature coefficient is improved, and high H can be obtained at high temperature_cJ. When the Mn content is less than 0.03 mass%, the temperature coefficient cannot be improved, and high H cannot be obtained at high temperatures_cJ. When the content exceeds 0.15% by mass, B_rPossibly reduced. (T: 61.5 to 70.0 mass%)

T is Fe or Fe and Co, and at least 90 mass% of T is Fe. Although the corrosion resistance can be improved by containing Co, if the Co substitution amount exceeds 10 mass% of T, a high B content may not be obtained_r. The content of T is 61.5-70.0 mass%, and satisfies the above formula (1). When the content of T is less than 61.5 mass%, B_rA substantial reduction is possible. Preferably T is the remainder.

The R-T-B sintered magnet of the present invention may further contain Cr, Mn, Si, La, Ce, Sm, Ca, Mg, and the like, which are generally contained as inevitable impurities in didymium (Nd-Pr), electrolytic iron, iron-boron alloys, and the like. Further, as inevitable impurities in the production process, O (oxygen) and N (nitrogen) may be exemplified) And C (carbon), Al, etc. The R-T-B sintered magnet of the present invention may contain 1 or more kinds of other elements (elements intentionally added in addition to unavoidable impurities). For example, such elements may contain small amounts (about 0.1 mass% each) of Ag, Zn, In, Sn, Ti, Ge, Y, H, F, P, S, V, Ni, Mo, Hf, Ta, W, Nb, Zr, and the like. Further, elements listed as the above-mentioned inevitable elements may be intentionally added. Such elements may be contained in an amount of about 1.0 mass% in total. If it is in this range, there is a sufficient possibility of obtaining a high H at a high temperature_cJThe R-T-B sintered magnet of (1).

The R-T-B sintered magnet having the composition according to the embodiment of the present invention can be produced, for example, by a production method including the steps of: a step of producing a quenched alloy; a molding step of molding the alloy powder to obtain a molded body; a sintering step of sintering the molded body to obtain a sintered body; and a heat treatment step of performing heat treatment on the sintered body. [ method for producing R-T-B sintered magnet ]

Next, each step will be explained.

(Process for producing alloy powder)

In order to obtain the above-mentioned specific composition of the R-T-B sintered magnet, metals or alloys (melting raw materials) of the respective elements are prepared, and a sheet-like raw material alloy is produced by a belt casting method or the like. Then, the flake-like raw material alloy is coarsely pulverized by hydrogen pulverization or the like, and coarsely pulverized powder having an average particle size of 1.0mm or less is prepared. Next, the coarsely pulverized powder is finely pulverized by a jet mill or the like in an inert gas to obtain, for example, a particle diameter D₅₀Is a finely pulverized powder (raw alloy powder) of 3 to 5 μm. A known lubricant may be added as an auxiliary agent to the coarse pulverized powder before the jet mill pulverization, the alloy powder during the jet mill pulverization, and the alloy powder after the jet mill pulverization.

(Molding Process)

The obtained raw material powder was molded in a magnetic field to obtain a molded article. As the molding in the magnetic field, any known molding in the magnetic field can be used, including a dry molding method in which the molding is performed while applying the magnetic field after the dried alloy powder is inserted into the cavity of the mold, and a wet molding method in which the molding is performed while discharging the dispersion medium of the slurry after the slurry is injected into the cavity of the mold.

(sintering Process)

The molded body is sintered to obtain a sintered body (sintered magnet). The sintering of the shaped bodies can be carried out by known methods. In order to prevent oxidation due to the atmosphere during sintering, it is preferable to perform sintering in a vacuum atmosphere or in an inert gas. As the inert gas, helium, argon or the like is preferably used.

(Heat treatment Process)

The sintered magnet thus obtained is preferably subjected to a heat treatment for the purpose of improving the magnetic properties. The heat treatment temperature, heat treatment time, and the like can utilize known conditions. For example, the heat treatment may be performed at a relatively low temperature (400 ℃ to 600 ℃) only (first heat treatment), or the heat treatment may be performed at a relatively high temperature (700 ℃ to 700 ℃ sintering temperature (e.g., 1050 ℃ to below)) and then the heat treatment may be performed at a relatively low temperature (400 ℃ to 600 ℃) thereafter (second heat treatment). Preferable conditions include heat treatment at 730 ℃ to 1020 ℃ for about 5 minutes to 500 minutes, heat treatment after cooling (after cooling to room temperature or after cooling to 440 ℃ to 550 ℃) and heat treatment at 440 ℃ to 550 ℃ for about 5 minutes to 500 minutes. The heat treatment atmosphere is preferably performed in a vacuum atmosphere or an inert gas (helium, argon, or the like).

The obtained sintered magnet may be subjected to mechanical processing such as grinding for the purpose of forming a final product shape or the like. In this case, the heat treatment may be performed before or after the machining. Further, the obtained sintered magnet may be subjected to surface treatment. The surface treatment may be a known surface treatment, or may be surface treatment such as Al deposition, Ni plating, or resin coating.