Patent Application
20190326053
The present invention relates to a sintered R-T-B based magnet and a method for producing the same.
Sintered R-T-B based magnets (where R is at least one rare-earth element which always includes Nd; T is at least one transition metal element which always includes Fe; and B is boron) are known as permanent magnets with the highest performance, and are used in voice coil motors (VCM) of hard disk drives, various types of motors such as motors for electric vehicles (EV, HV, PHV, etc.) and motors for industrial equipment, home appliance products, and the like.
A sintered R-T-B based magnet is composed of a main phase which mainly consists of an R2T14B compound and a grain boundary phase (which hereinafter may be simply referred to as the “grain boundaries”) that is at the grain boundaries of the main phase. The R2T14B compound is a ferromagnetic phase having high magnetization, and provides a basis for the properties of a sintered R-T-B based magnet.
There exists a problem in that coercivity HcJ (which hereinafter may be simply referred to as “coercivity” or as “HcJ”) of sintered R-T-B based magnets decreases at high temperatures, thus causing an irreversible thermal demagnetization. For this reason, sintered R-T-B based magnets for use in motors for electric vehicles, in particular, are required to have high HcJ at high temperatures, i.e., to have higher HcJ at room temperature.
[Patent Document 1] International Publication No. 2007/102391
[Patent Document 2] International Publication No. 2013/008756
[Patent Document 3] International Publication No. 2016/133071
It is known that HcJ is improved if Nd, as a light rare-earth element RL in an R2T14B-based compound phase, is replaced with a heavy rare-earth element RH (mainly Dy, Tb). However, in a sintered R-T-B based magnet, replacing the light rare-earth element RL (Nd, Pr) with a heavy rare-earth element RH may improve HcJ, but decrease its remanence Br (which hereinafter may be simply referred to as “remanence” or “Br”) because of decreasing the saturation magnetization of the R2T14B-based compound phase.
Patent Document 1 describes, while supplying a heavy rare-earth element RH such as Dy onto the surface of a sintered magnet of an R-T-B based alloy, allowing the heavy rare-earth element RH to diffuse into the interior of the sintered magnet. According to the method described in Patent Document 1, Dy is diffused from the surface of the sintered R-T-B based magnet into the interior, thus allowing Dy to thicken only in the outer crust of a main phase crystal grain that is effective for HcJ improvement, whereby high HcJ can be obtained with a suppressed decrease in Br.
However, heavy rare-earth elements, in particular Dy and the like, are a scarce resource, and they yield only in limited regions. For this and other reasons, they have problems of instable supply, significantly fluctuating prices, and so on. Therefore, it has been desired in the recent years to improve HcJ without using a heavy rare-earth element RH.
Patent Document 2 discloses a sintered R-T-B based rare-earth magnet in which coercivity is enhanced while the Dy content is reduced. The composition of this sintered magnet is limited to a specific range characterized by relatively small B amounts as compared to any R-T-B type alloys which have been commonly used, and contains one or more metallic elements M selected from among Al, Ga and Cu. As a result, an R2T17 phase is formed at the grain boundaries, and, from this R2T17 phase, a transition metal-rich phase (R6T13M) is formed at the grain boundaries with an increased volumetric proportion, whereby HcJ is improved.
Patent Document 3 describes allowing an R—Ga—Cu alloy of a specific composition to be in contact with the surface of an R-T-B based sintered compact whose B amount is lower than usual (i.e., lower than is defined by the stoichiometric ratio of the R2T14B compound) and performing a heat treatment, thus to control the composition and thickness of a grain boundary phase in the sintered R-T-B based magnet and improve HcJ.
According to the method described in Patent Document 2 or Patent Document 3, it is possible to obtain high HcJ without using a heavy rare-earth element RH such as Dy; however, there is a problem of lowered Br.
Various embodiments of the present disclosure provide sintered R-T-B based magnets which have high Br and high HcJ while reducing the content of the heavy rare-earth element RH, and methods for producing the same.
In an illustrative embodiment, a sintered R-T-B based magnet according to the present disclosure is a sintered R-T-B based magnet comprising:
R: not less than 28 mass % and not more than 36 mass % (where R is at least one rare-earth element which always includes at least one of Nd and Pr),
B: not less than 0.73 mass % and not more than 0.96 mass %,
Ga: not less than 0.1 mass % and not more than 1.0 mass %,
Cu: not less than 0.1 mass % and not more than 1.0 mass %, and
T: not less than 60 mass % (where T is at least one selected from the group consisting of Fe, Co, Al, Mn and Si and always includes Fe, such that the Fe content accounts for 80 mass % or more in the entire T), wherein,
a molar ratio of T to B ([T]/[B]) is greater than 14.0;
an R amount in a magnet surface portion at a cross section perpendicular to an alignment direction is greater than an R amount in a magnet central portion;
a Ga amount in the magnet surface portion at the cross section perpendicular to the alignment direction is greater than a Ga amount in the magnet central portion; and
a molar ratio of T to B ([T]/[B]) in the magnet surface portion at the cross section perpendicular to the alignment direction is higher than a molar ratio of T to B ([T]/[B]) in the magnet central portion.
In a preferred embodiment, a Cu amount in the magnet surface portion at the cross section perpendicular to the alignment direction is greater than a Cu amount in the magnet central portion.
In a preferred embodiment, the molar ratio of T to B ([T]/[B]) of the sintered R-T-B based magnet is greater than 14.0 but not greater than 16.4.
In another illustrative embodiment, a method for producing a sintered R-T-B based magnet according to the present disclosure comprises: a step of providing an R1-T1-B based sintered compact; a step of providing an R2-Cu—Ga—Fe based alloy; a step of, while keeping at least a portion of the R2-Cu—Ga—Fe based alloy in contact with at least a portion of a surface of the R1-T1-B based sintered compact, performing a first heat treatment at a temperature of not lower than 700° C. and not higher than 1100° C. in a vacuum or an inert gas ambient; and a step of subjecting the R1-T1-B based sintered compact having undergone the first heat treatment to a second heat treatment at a temperature of not lower than 450° C. and not higher than 600° C. in a vacuum or an inert gas ambient. In the R1-T1-B based sintered compact, R1 is at least one rare-earth element which always includes at least one of Nd and Pr, the R1 content accounting for not less than 27 mass % and not more than 35 mass % of the entire R1-T1-B based sintered compact, T1 is at least one selected from the group consisting of Fe, Co, Al, Mn and Si, where T1 always includes Fe, the Fe content in the entire T1 accounting for 80 mass % or more, and a molar ratio [T1]/[B] is greater than 14.0 but not greater than 15.0. In the R2-Cu—Ga—Fe based alloy, R2 is at least one rare-earth element which always includes at least one of Nd and Pr, the R2 content accounting for not less than 35 mass % and not more than 85 mass % of the entire R2-Cu—Ga—Fe based alloy, the Cu content accounts for not less than 2.5 mass % and not more than 40 mass % of the entire R2-Cu—Ga—Fe based alloy, the Ga content accounts for not less than 2.5 mass % and not more than 40 mass % of the entire R2-Cu—Ga—Fe based alloy, and the Fe content accounts for not less than 10 mass % and not more than 45 mass % of the entire R2-Cu—Ga—Fe based alloy.
In one embodiment, the molar ratio [T1]/[B] is not smaller than 14.3 and not greater than 15.0.
In one embodiment, the Fe content in the R2-Cu—Ga—Fe based alloy accounts for not less than 15 mass % and not more than 40 mass % of the entire R2-Cu—Ga—Fe based alloy.
In one embodiment, 50 mass % or more of the R2 in the R2-Cu—Ga—Fe based alloy is Pr.
In one embodiment, 70 mass % or more of the R2 in the R2-Cu—Ga—Fe based alloy is Pr.
In one embodiment, a total content of R2, Cu, Ga and Fe in the R2-Cu—Ga—Fe based alloy accounts for 80 mass % or more.
In one embodiment, the temperature of the first heat treatment is not lower than 800° C. and not higher than 1000° C.
In one embodiment, the temperature of the second heat treatment is not lower than 480° C. and not higher than 560° C.
In one embodiment, the step of providing the R1-T1-B based sintered compact comprises pulverizing a raw material alloy so as to result in a particle size D50 of not less than 3 μm and not more than 10 μm, and thereafter performing sintering while aligning the R1-T1-B based sintered compact in a magnetic field.
In another illustrative embodiment, a method for producing a sintered R-T-B based magnet according to the present disclosure comprises: a step of providing an R1-T1-Cu—B based sintered compact; a step of providing an R2-Ga—Fe based alloy; a step of, while keeping at least a portion of the R2-Ga—Fe based alloy in contact with at least a portion of a surface of the R1-T1-Cu—B based sintered compact, performing a first heat treatment at a temperature of not lower than 700° C. and not higher than 1100° C. in a vacuum or an inert gas ambient; and a step of subjecting the R1-T1-Cu—B based sintered compact having undergone the first heat treatment to a second heat treatment at a temperature of not lower than 450° C. and not higher than 600° C. in a vacuum or an inert gas ambient. In the R1-T1-Cu—B based sintered compact, R1 is at least one rare-earth element which always includes at least one of Nd and Pr, the R1 content accounting for not less than 27 mass % and not more than 35 mass % of the entire R1-T1-Cu—B based sintered compact, T1 is at least one selected from the group consisting of Fe, Co, Al, Mn and Si, where T1 always includes Fe, the Fe content in the entire T1 accounting for 80 mass % or more, a molar ratio [T1]/[B] is greater than 14.0 but not greater than 15.0, and the Cu content accounts for not less than 0.1 mass % and not more than 1.5 mass % of the entire R1-T1-Cu—B based sintered compact. In the R2-Ga—Fe based alloy, R2 is at least one rare-earth element which always includes at least one of Nd and Pr, the R2 content accounting for not less than 35 mass % and not more than 85 mass % of the entire R2-Ga—Fe based alloy, the Ga content accounts for not less than 2.5 mass % and not more than 40 mass % of the entire R2-Ga—Fe based alloy, and the Fe content accounts for not less than 10 mass % and not more than 45 mass % of the entire R2-Ga—Fe based alloy.
In one embodiment, the molar ratio [T1]/[B] is not smaller than 14.3 and not greater than 15.0.
In one embodiment, the Fe content in the R2-Ga—Fe based alloy accounts for not less than 15 mass % and not more than 40 mass % of the entire R2-Ga—Fe based alloy.
In one embodiment, 50 mass % or more of the R2 in the R2-Ga—Fe based alloy is Pr.
In one embodiment, 70 mass % or more of the R2 in the R2-Ga—Fe based alloy is Pr.
In one embodiment, a total content of R2, Ga and Fe in the R2-Ga—Fe based alloy accounts for 80 mass % or more.
In one embodiment, the temperature of the first heat treatment is not lower than 800° C. and not higher than 1000° C.
In one embodiment, the temperature of the second heat treatment is not lower than 480° C. and not higher than 560° C.
In one embodiment, the step of providing the R1-T1-Cu—B based sintered compact comprises pulverizing a raw material alloy so as to result in a particle size D50 of not less than 3 μm and not more than 10 μm, and thereafter performing sintering while aligning the R1-T1-B based sintered compact in a magnetic field.
According to an embodiment of the present disclosure, while reducing the content of a heavy rare-earth element RH, a sintered R-T-B based magnet having high Br and high HcJ is provided.
A sintered R-T-B based magnet according to the present disclosure is produced by performing a heat treatment while an alloy containing R, Ga and Fe as its component elements is kept in contact with at least a portion of the surface of an R-T-B based sintered compact, and has a specific composition whose B amount is lower than usual (i.e., lower than is defined by the stoichiometric ratio of the R2T14B compound). Without containing any Dy and Tb, which are heavy rare-earth elements, a sintered R-T-B based magnet according to the present disclosure has Br and HcJ which are as high as or higher than those in the case where Dy is contained (i.e., Dy being added to the raw material alloy), and is further able to exhibit high Br and high HcJ similar to those of the Br and HcJ of a sintered R-T-B based magnet that is produced by a method which diffuses Dy from the surface into the interior so that Dy is thickened in the outer crust of the main phase crystal grain.
<Mechanism>
As mentioned earlier, the method which is described in Patent Document 3 involves allowing an R—Ga—Cu alloy of a specific composition to be in contact with the surface of an R-T-B based sintered compact whose B amount is lower than usual (i.e., lower than is defined by the stoichiometric ratio of the R2T14B compound) and performing a heat treatment, thus to control the composition and thickness of a grain boundary phase in the sintered R-T-B based magnet and improve HcJ. With this method, saturation magnetization of the main phase is hardly deteriorated because no heavy rare-earth element is used. However, since a grain boundary phase is formed which is thicker than usual, the proportion of the main phase is inevitably reduced, and lowering of Br is unavoidable.
Through their studies, the inventors have found that, by using an R—Ga—Fe alloy containing Fe as an alloy to be kept in contact with the surface of the R-T-B based sintered compact, instead of the R—Ga—Cu alloy described in Patent Document 3, and by ensuring that the B amount in the finally-obtained sintered R-T-B based magnet is smaller than is defined by the stoichiometric ratio of the R2T14B compound, not only higher Br is obtained than is attained by the sintered R-T-B based magnet of Patent Document 3, but also that high Br and high HcJ similar to those of the sintered R-T-B based magnet described in Patent Document 1 are obtained without using a heavy rare-earth element. This is presumably because, in the sintered R-T-B based magnet which is obtained by the method described in Patent Document 3, not only the grain boundary phase near the magnet surface but also the grain boundary phase near the magnet center increases in thickness, so that the proportion of the main phase decreases and Br lowers; on the other hand, in a sintered R-T-B based magnet according to the present disclosure, due to the presence of Fe contained in the R—Ga—Fe alloy, the grain boundary phase near the magnet surface becomes larger in thickness as in the magnet according to Patent Document 3, and conversely the grain boundary phase near the magnet center becomes smaller in thickness than in the magnet according to Patent Document 3 (given that the magnet according to the present disclosure and the magnet according to Patent Document 3 (i.e., the sintered R-T-B based magnet after diffusion) are identical in composition). This is believed to suppress a decrease in the main phase proportion near the magnet center. Furthermore, through a detailed study it has also been found that, in a sintered R-T-B based magnet according to the present disclosure, a molar ratio of T to B ([T]/[B]) in a magnet surface portion at a cross section perpendicular to the alignment direction (which hereinafter may be referred to as a “molar ratio [T]/[B]”) is higher than a molar ratio [T]/[B] in the magnet central portion (i.e., the molar ratio [T]/[B] is lower in the magnet central portion than in the magnet surface portion (i.e., the magnet central portion is relatively high in B)). In a sintered R-T-B based magnet having such a distributed composition, a decrease in the main phase proportion near the magnet center can be minimized, whereby a decrease in Br can be suppressed.
<Explanation of T/B Ratio>
An R—Ga—Fe alloy is used in producing a sintered R-T-B based magnet according to the present disclosure. The R, Ga and Fe elements which are contained in the R—Ga—Fe alloy are introduced from the sintered compact surface into the interior, mainly through grain boundaries of the R-T-B based sintered compact. When the R, Ga and Fe elements are introduced from the sintered compact surface into the interior, an R amount in the magnet surface portion will be greater than an R amount in the magnet central portion, along the alignment direction. As the R amount in the magnet surface portion increases, amounts (proportions) of the other elements (e.g., B and Fe) will become increasingly smaller than in the magnet central portion. For example, in a sintered R-T-B based magnet in which Fe is not diffused from the magnet surface into the interior, as exemplified by a sintered R-T-B based magnet which is obtained by the method described in Patent Document 3, amounts of change in Fe and B between the magnet surface portion and the magnet central portion that are caused by R diffusion are similar, in a cross section perpendicular to the alignment direction. Specifically, since the amount of R introduced differs between the magnet surface portion and the magnet central portion, the abundance of R increases in the magnet surface portion, whereby the abundances of Fe and B become relative small. On the other hand, the abundance of R does not increase much in the magnet central portion, and therefore the abundances of Fe and B do not become much smaller. Thus, between the magnet surface portion and the magnet central portion, the relative abundances of Fe and B may be greater or smaller depending on the amount of R introduced, but the ratio between Fe and B does not change (because neither Fe no B is introduced from the sintered compact surface). Therefore, in a sintered R-T-B based magnet in which Fe is not diffused from the surface into the interior, the molar ratio [T]/[B] in a cross section perpendicular to the alignment direction is substantially equal between the magnet surface portion and the magnet central portion. Note that T is at least one selected from the group consisting of Fe, Co, Al, Mn and Si and always includes Fe, such that the Fe content accounts for 80 mass % or more in the entire T. In other words, Fe is the main component of T.
On the other hand, in a sintered R-T-B based magnet according to the present disclosure, not only R and Ga but also Fe is introduced from the sintered compact surface into the interior. Thus it has been found that, along the alignment direction, the amount of Fe introduced differs between the magnet surface portion and the magnet central portion (i.e., a larger amount of Fe is introduced in the magnet surface portion), and that the change in the relative abundance of Fe that is caused in the magnet surface portion by diffusion is smaller than the change in the relative abundance of B (which is not introduced from the sintered compact surface).
With such a characteristic distributed composition, it is possible to obtain high Br and high HcJ similar to those of the Br and HcJ of a sintered R-T-B based magnet in which Dy is thickened in the outer crust of a main phase crystal grain.
Hereinafter, embodiments concerning the structure and methods for producing of a sintered R-T-B based magnet according to the present disclosure will be described in more detail.
<Structure of Sintered R-T-B Based Magnet>
First, the fundamental structure of a sintered R-T-B based magnet according to the present disclosure will be described.
The sintered R-T-B based magnet has a structure such that powder particles of a raw material alloy have bound together through sintering, and is composed of a main phase which mainly consists of an R2T14B compound and a grain boundary phase which is at the grain boundaries of the main phase.
The main phase 12, i.e., the R2T14B compound, is a ferromagnetic phase having high saturation magnetization and an anisotropy field. Therefore, in a sintered R-T-B based magnet, it is possible to improve Br by increasing the abundance ratio of the R2T14B compound which is the main phase 12. In order to increase the abundance ratio of the R2T14B compound, the R amount, the T amount, and the B amount in the raw material alloy may be brought closer to the stoichiometric ratio of the R2T14B compound (i.e., the R amount: the T amount: the B amount=2:14:1). When the B amount or the R amount belonging in the R2T14B compound falls lower than the stoichiometric ratio, generally speaking, small pieces of magnetic substance such as an Fe phase or an R2T17 phase occurs in the grain boundary phase 14, whereby HcJ is drastically decreased. However, it has been found that a sintered R-T-B based magnet according to the present disclosure can attain high Br and high HcJ because of having a composition and texture as described below.
In a non-limiting and illustrative embodiment, a sintered R-T-B based magnet according to the present disclosure has the following composition.
R: not less than 28 mass % and not more than 36 mass % (where R is at least one rare-earth element which always includes at least one of Nd and Pr),
B: not less than 0.73 mass % and not more than 0.96 mass %,
Ga: not less than 0.1 mass % and not more than 1.0 mass %,
Cu: not less than 0.1 mass % and not more than 1.0 mass %,
T: not less than 60 mass % (where T is at least one selected from the group consisting of Fe, Co, Al, Mn and Si and always includes Fe, such that the Fe content accounts for 80 mass % or more in the entire T).
Herein, the molar ratio [T]/[B] is greater than 14.0. Preferably, the molar ratio [T]/[B] is greater than 14.0 but not greater than 16.4. This will allow higher Br and higher HcJ to be obtained. Moreover, an R amount in a magnet surface portion at a cross section perpendicular to the alignment direction is greater than an R amount in the magnet central portion, and a Ga amount in a magnet surface portion at a cross section perpendicular to the alignment direction is greater than a Ga amount in the magnet central portion. Furthermore, a molar ratio [T]/[B] in a magnet surface portion at a cross section perpendicular to the alignment direction is higher than a molar ratio [T]/[B] in the magnet central portion.
As used in the present disclosure, a molar ratio of T to B ([T]/[B]) is a ratio (a/b) between: a total (a) of the respective value of a result of dividing an analysis value (mass %) of each element (Fe, Co, Al, Mn and Si) composing T with the atomic weight of that element; and (b) a result of dividing an analysis value (mass %) of B with the atomic weight of B.
That a “molar ratio [T]/[B] is greater than 14.0” means that B is contained by a ratio which is lower than is defined by the stoichiometric ratio of the R2T14B compound. Stated otherwise, in the sintered R-T-B based magnet, there is a relatively small B amount for the T amount that is consumed in the main phase (R2T14B compound) formation.
That “an R amount in a magnet surface portion at a cross section perpendicular to the alignment direction is greater than an R amount in the magnet central portion” means that R has been diffused from the magnet surface into the magnet interior.
That “a Ga amount in a magnet surface portion at a cross section perpendicular to the alignment direction is greater than a Ga amount in the magnet central portion” means that Ga has been diffused from the magnet surface into the magnet interior.
Furthermore, as aforementioned, that “a molar ratio [T]/[B] in a magnet surface portion at a cross section perpendicular to the alignment direction is higher than a molar ratio [T]/[B] in the magnet central portion” means that Fe has been diffused from the magnet surface into the magnet interior.
Moreover, as will be indicated in a below-described first embodiment, in the case where R, Cu, Ga and Fe are introduced from the sintered compact surface into the interior by using an R2-Cu—Ga—Fe based alloy, a Cu amount in the magnet surface portion is greater than a Cu amount in the magnet central portion, similarly to R and Ga in a cross section perpendicular to the alignment direction.
In the present disclosure, it is confirmed in the following manner as to whether or not “an R amount in a magnet surface portion at a cross section perpendicular to the alignment direction is greater than an R amount in the magnet central portion”. Based on
On the other hand, a magnet central portion sample 40 is cut out so that its expanse as projected onto the x-y plane coincides with the expanse of the magnet surface portion sample 30 as projected onto the x-y plane. Specifically, it is cut out from a position immediately under the magnet surface portion sample 30 along the z direction (alignment direction). Typically, the magnet central portion sample 40 is to be cut out so as to be similar in dimensions and shape to the magnet surface portion sample 30.
A Ga amount in the magnet surface portion and a Ga amount in the magnet central portion, a molar ratio [T]/[B] in the magnet surface portion and a molar ratio [T]/[B] in the magnet central portion, and a Cu amount in the magnet surface portion and a Cu amount in the magnet central portion are also similarly determined, in a cross section perpendicular to the alignment direction.
Note that the composition (R, B, Ga, Cu, T, and the molar ratio [T]/[B] being greater than 14.0) of a sintered R-T-B based magnet according to the present disclosure is to be measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) under an apparatus name: ICPV-1017 (manufactured by Shimadzu Corporation). Moreover, in a cross section perpendicular to the alignment direction, the R amount, the Ga amount, the Cu amount, and the molar ratio [T]/[B] in the magnet surface portion and in the magnet central portion according to the present disclosure are to be measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) under an apparatus name: ICPE-9000 (manufactured by Shimadzu Corporation).
In the present disclosure, rare-earth elements are collectively referred to as “R”. When referring to any specific element or element group among the rare-earth elements R, it may be distinguished from other rare-earth elements by the use of a label such as “R1” or “R2”. For example, a rare-earth element contained in an R-T-B based sintered compact may be referred to as “R1” and a rare-earth element contained in an R—Ga—Fe alloy may be referred to as “R2” for distinction. However, an element or element group indicated as “R1” may overlap or coincide with an element or element group indicated as “R2”.
Similarly, an element or element group indicated as “T” may be distinguished by the use of a label such as “T1” or “T2”. For example, a T (which is at least one selected from the group consisting of Fe, Co, Al, Mn and Si and always includes Fe) that is contained in an R-T-B based sintered compact before diffusion may be referred to as “T1”, whereas a T (which is at least one selected from the group consisting of Fe, Co, Al, Mn and Si and always includes Fe) that is contained in a sintered R-T-B based magnet after diffusion may be referred to as “T2”.
Note that, in addition to the aforementioned elements, a sintered R-T-B based magnet according to the present disclosure may contain Ag, In, Sn, Zr, Nb, Ti, Ni, Hf, Ta, W, Ge, Mo, V, Y, La, Ce, Sm, Ca, Mg, Cr, H, F, P, S, Cl, O, N, C, or the like.
<First Embodiment of a Method for Producing a Sintered R-T-B Based Magnet>
In a first embodiment, a method for producing a sintered R-T-B based magnet according to the present disclosure includes step S10 of providing an R1-T1-B based sintered compact and step S20 of providing an R2-Cu—Ga—Fe based alloy, as shown in
In the present disclosure, any sintered R-T-B based magnet prior to a second heat treatment or during a second heat treatment will be referred to as an R1-T1-B based sintered compact, and any R1-T1-B based sintered compact after the second heat treatment will be simply referred to as a sintered R-T-B based magnet.
In the R1-T1-B based sintered compact, the following (1) to (3) are satisfied.
As used in the present disclosure, a [T1]/[B] is a ratio (a/b) between: a total (a) of the respective value of a result of dividing an analysis value (mass %) of each element (at least one selected from the group consisting of Fe, Co, Al, Mn and Si) composing T1 with the atomic weight of that element; and (b) a result of dividing an analysis value (mass %) of B with the atomic weight of B.
That a molar ratio [T1]/[B] is greater than 14.0 means that B is contained by a ratio which is lower than is defined by the stoichiometric ratio of the R2T14B compound. Stated otherwise, in the R1-T1-B based sintered compact, there is a relatively small B amount for the T1 amount that is consumed in the main phase (R2T14B compound) formation.
In the R2-Cu—Ga—Fe based alloy, the following (4) to (7) are satisfied.
A method for producing a sintered R-T-B based magnet according to the present disclosure involves performing: step S30 of, while keeping an R2-Cu—Ga—Fe based alloy in contact with at least a portion of the surface of an R1-T1-B based sintered compact having a relatively small B amount, in terms of the stoichiometric ratio, for the T amount that is consumed in the main phase (R2T14B compound) formation, performing a first heat treatment at a temperature of not lower than 700° C. and not higher than 1100° C. in a vacuum or an inert gas ambient, as shown in
Any other step, e.g., a cooling step, may be performed between step S30 of performing the first heat treatment and step S40 of performing the second heat treatment.
In a method for producing a sintered R-T-B based magnet according to the present disclosure, an R2-Cu—Ga—Fe based alloy of a specific composition according to the present disclosure is used to introduce R2, Cu, Ga and Fe from the magnet surface into the interior, whereby high Br and high HcJ can be realized.
(Step of Providing R1-T1-B Based Sintered Compact)
First, regarding the step of providing an R1-T1-B based sintered compact (which may hereinafter be simply referred to as a “sintered compact”), the composition of the sintered compact will be discussed.
R1 is at least one rare-earth element which always includes at least one of Nd and Pr. In order to improve HcJ of the R1-T1-B based sintered compact, a heavy rare-earth element(s) such as Dy, Tb, Gd and Ho, which are of common use, may be contained in small amounts. However, with the production method according to the present disclosure, sufficiently high HcJ can be obtained without using large amounts of heavy rare-earth elements. Therefore, the content of the heavy rare-earth element(s) is preferably 1 mass % or less, and more preferably 0.5 mass % or less, of the R1-T1-B based sintered compact; still more preferably, no heavy rare-earth elements are contained (i.e., substantially 0 mass %).
The R1 content accounts for not less than 27 mass % and not more than 35 mass % of the entire R1-T1-B based sintered compact. If the R1 content is less than 27 mass %, a liquid phase will not sufficiently occur in the sintering process, and it will be difficult for the R1-T1-B based sintered compact to become adequately dense in texture. On the other hand, if the R1 content exceeds 35 mass %, effects of the present disclosure will be obtained, but the alloy powder during the production steps of the R1-T1-B based sintered compact will be very active. Since this may consequently cause considerable oxidization, ignition, etc., of the alloy powder, 35 mass % or less is preferable. More preferably, the R1 content is not less than 27.5 mass % and not more than 33 mass %. Still more preferably, it is not less than 28 mass % and not more than 32 mass %.
T1 is at least one selected from the group consisting of Fe, Co, Al, Mn and Si, where T1 always includes Fe. In other words, T1 may be Fe alone, or consist of at least one of Co, Al, Mn and Si, and Fe. However, the Fe content accounts for 80 mass % or more in the entire T1. If the Fe content is less than 80 mass %, Br and HcJ may lower. Herein, “the Fe content accounts for 80 mass % or more in the entire T1” means that, in the case where e.g. the T1 content accounts for 70 mass % in the R1-T1-B based sintered compact, 56 mass % or more of the R1-T1-B based sintered compact is Fe. Preferably, the Fe content accounts for 90 mass % or more in the entire T1, as this will provide higher Br and higher HcJ. In the case where Co, Al, Mn and Si are contained, their preferable contents are: Co accounts for 5.0 mass % or less; Al accounts for 1.5 mass % or less; and Mn and Si each account for 0.2 mass % or less, in the entire R1-T1-B based sintered compact.
The molar ratio [T1]/[B] is greater than 14.0 but not greater than 16.0.
As used in the present disclosure, a [T1]/[B] is a ratio (a/b) between: a total (a) of the respective value of a result of dividing an analysis value (mass %) of each element (Fe; or at least one of Co, Al, Mn and Si and Fe) composing T1 with the atomic weight of that element; and (b) a result of dividing an analysis value (mass %) of B with the atomic weight of B.
The condition that the molar ratio [T1]/[B] is greater than 14.0 means that there is a relatively small B amount for the T1 amount that is consumed in the main phase (R2T14B compound) formation. If the molar ratio [T1]/[B] is 14.0 or smaller, high HcJ may not be obtained. On the other hand, if the molar ratio [T1]/[B] exceeds 16.0, Br may lower. Preferably, the molar ratio [T1]/[B] is not smaller than 14.3 and not greater than 15.0, as this will provide even higher Br and higher HcJ. Moreover, the B content preferably accounts for not less than 0.8 mass % but less than 1.0 mass % of the entire R1-T1-B based sintered compact.
In addition to the aforementioned elements, the R1-T1-B based sintered compact may contain Ga, Cu, Ag, Zn, In, Sn, Zr, Nb, Ti, Ni, Hf, Ta, W, Ge, Mo, V, Y, La, Ce, Sm, Ca, Mg, Cr, H, F, P, S, Cl, O, N, C, and the like. The preferable contents are: Ni, Ga, Cu, Ag, Zn, In, Sn, Zr, Nb and Ti each account for 0.5 mass % or less; Hf, Ta, W, Ge, Mo, V, Y, La, Ce, Sm, Ca, Mg and Cr each account for 0.2 mass % or less; H, F, P, S and Cl account for 500 ppm or less; 0 accounts for 6000 ppm or less; N accounts for 1000 ppm or less; and C accounts for 1500 ppm or less. A total content of these elements preferably accounts for 5 mass % or less of the entire R1-T1-B based sintered compact. If a total content of these elements exceeds 5 mass % of the entire R1-T1-B based sintered compact, high Br and high HcJ may not be obtained.
Next, the step of providing an R1-T1-B based sintered compact will be described. The step of providing an R1-T1-B based sintered compact can be achieved by using a generic production method, e.g., a sintered R-T-B based magnet. Preferably, after the raw material alloy is pulverized to a particle size D50 (a central value of volume as obtained through measurement by an airflow-dispersion laser diffraction method=D50) of not less than 3 μm and not more than 10 μm, the R1-T1-B based sintered compact is sintered while being aligned in a magnetic field. As one example, a raw material alloy which is produced by a strip casting method or the like may be pulverized to a particle size D50 of not less than 3 μm and not more than 10 μm by using a jet mill machine or the like, thereafter pressed in a magnetic field, and then sintered at a temperature of not lower than 900° C. and not higher than 1100° C. If the particle size D50 of the raw material alloy is less than 3 μm, it becomes very difficult to produce pulverized powder, thus resulting in a greatly reduced production efficiency, which is not preferable. On the other hand, if the particle size D50 exceeds 10 μm, the R1-T1-B based sintered compact as finally obtained will have too large a crystal grain size to achieve high HcJ, which is not preferable. The particle size D50 is preferably not less than 3 μm and not more than 5 μm.
So long as the aforementioned conditions are satisfied, the R1-T1-B based sintered compact may be produced from one kind of raw material alloy (a single raw-material alloy), or through a method of using two or more kinds of raw material alloys and mixing them (two-alloy method). Moreover, the resultant R1-T1-B based sintered compact may be subjected to known machining such as severing or cutting as necessary before undergoing the first heat treatment and the second heat treatment described below.
(Step of Providing R2-Cu—Ga—Fe Based Alloy)
First, regarding the step of providing an R2-Cu—Ga—Fe based alloy, the composition of the R2-Cu—Ga—Fe based alloy will be discussed. Since R, Ga, Cu and Fe are all contained in specific ranges as described below, the R2, Cu, Ga and Fe in the R2-Cu—Ga—Fe based alloy can be introduced into the R1-T1-B based sintered compact in the below-described step of performing the first heat treatment.
R2 is at least one rare-earth element which always includes at least one of Nd and Pr. Preferably, 50 mass % or more of R2 is Pr, as this will provide higher HcJ. Herein, that “50 mass % or more of R2 is Pr” means that, in the case where e.g. the R2 content in the R2-Cu—Ga—Fe alloy is 50 mass %, 25 mass % or more of the R2-Cu—Ga—Fe alloy is Pr. Still more preferably, 70 mass % or more of R2 is Pr, and most preferably, R2 is Pr alone (while it may contain inevitable impurities). As a result of this, even higher HcJ can be obtained. As the R2, a heavy rare-earth element(s) such as Dy, Tb, Gd and Ho may be contained in small amounts. However, with the production method according to the present disclosure, sufficiently high HcJ can be obtained without using large amounts of heavy rare-earth elements. Therefore, the content of the heavy rare-earth element(s) is preferably 10 mass % or less (i.e., the heavy rare-earth element(s) in the R2-Cu—Ga—Fe based alloy accounts for 10 mass % or less), and more preferably 5 mass % or less, of the entire R2-Cu—Ga—Fe based alloy; still more preferably, no heavy rare-earth elements are contained (i.e., substantially 0 mass %). In the case where the R2 in the R2-Cu—Ga—Fe based alloy contains a heavy rare-earth element(s), too, preferably 50% or more of R2 is Pr, and it is more preferable that the R2 excluding the heavy rare-earth element(s) is Pr alone (while it may contain inevitable impurities).
The R2 content accounts for not less than 35 mass % and not more than 85 mass % of the entire R2-Cu—Ga—Fe based alloy. If the R2 content is less than 35 mass %, diffusion may possibly not sufficiently progress in the below-described first heat treatment. On the other hand, if the R2 content exceeds 85 mass %, effects of the present disclosure will be obtained, but the alloy powder during the production steps of the R2-Cu—Ga—Fe based alloy will be very active. Since this may consequently cause considerable oxidization, ignition, etc., of the alloy powder, the R2 content is preferably 85 mass % or less of the entire R2-Cu—Ga—Fe based alloy. More preferably, the R2 content is not less than 50 mass % and not more than 85 mass %, and still more preferably it is not less than 60 mass % and not more than 85 mass %, as this will provide higher HcJ.
Cu accounts for not less than 2.5 mass % and not more than 40 mass % of the entire R2-Cu—Ga—Fe based alloy. If Cu is less than 2.5 mass %, the Cu, Ga and Fe in the R2-Cu—Ga—Fe based alloy will be less likely to be introduced into the interior of the R1-T1-B based sintered compact in the below-described step of performing the first heat treatment, and high HcJ may not be obtained. On the other hand, if Cu is 40 mass % or more, the abundance ratio of Ga at the grain boundaries will lower, and the generated amount of R-T-Ga phase may be too little to obtain high HcJ. More preferably, Cu accounts for not less than 4 mass % and not more than 30 mass %, and still more preferably not less than 4 mass % and not more than 20 mass %, as this will provide higher Br and higher HcJ.
Ga accounts for not less than 2.5 mass % and not more than 40 mass % of the entire R2-Cu—Ga—Fe based alloy. If Ga is less than 2.5 mass %, the Fe in the R2-Cu—Ga—Fe based alloy will be less likely to be introduced into the interior of the R1-T1-B based sintered compact in the below-described step of performing the first heat treatment, and high Br will not be obtained. Furthermore, the generated amount of R-T-Ga phase will be too little to obtain high HcJ. On the other hand, if Ga is 40 mass % or more, Br may greatly lower. More preferably, Ga accounts for not less than 4 mass % and not more than 30 mass %, and still more preferably not less than 4 mass % and not more than 20 mass %, as this will provide higher Br and higher HcJ.
Fe accounts for not less than 10 mass % and not more than 45 mass % of the entire R2-Cu—Ga—Fe based alloy. Fe must be contained in an amount of 5.8 mass % or more, and preferably 10 mass % or more, of the entire R2-Cu—Ga—Fe alloy. If Fe is 5.8 mass % or less, the amount of Fe introduced will be too little to allow a molar ratio [T]/[B] in the magnet surface portion to be higher than a molar ratio [T]/[B] in the magnet central portion, so that Br of the finally-obtained sintered R-T-B based magnet cannot be sufficiently enhanced. On the other hand, if Fe is 45 mass % or more, the R amount may be so little that diffusion may not sufficiently progress in the below-described first heat treatment and thus high Br and high HcJ may not be obtained. Preferably, Fe accounts for not less than 10 mass % and not more than 45 mass %, and more preferably not less than 15 mass % and not more than 40 mass %, as this will provide higher Br and higher HcJ.
In addition to the aforementioned elements, the R2-Cu—Ga—Fe based alloy may contain Co, Al, Ag, Zn, Si, In, Sn, Zr, Nb, Ti, Ni, Hf, Ta, W, Ge, Mo, V, Y, La, Ce, Sm, Ca, Mg, Mn, Cr, H, F, P, S, Cl, O, N, C, and the like.
For improved anticorrosiveness, Co is preferably contained in an amount of not less than 0.5 mass % and not more than 10 mass %. Preferable contents of the other elements are: Al accounts for 1.0 mass % or less; Ag, Zn, Si, In, Sn, Zr, Nb and Ti each account for 0.5 mass % or less; Ni, Hf, Ta, W, Ge, Mo, V, Y, La, Ce, Sm, Ca, Mg, Mn, Si and Cr each account for 0.2 mass % or less; H, F, P, S and Cl account for 500 ppm or less; 0 accounts for 0.2 mass % or less; N accounts for 1000 ppm or less; and C accounts for 1500 ppm or less. However, if a total content of these elements exceeds 20 mass %, the R2, Cu, Ga and Fe contents in the R2-Cu—Ga—Fe based alloy may be too little to obtain high Br and high HcJ. Therefore, a total content of R2, Cu, Ga and Fe in the R2-Cu—Ga—Fe based alloy preferably accounts for 80 mass % or more, and still more preferably 90 mass % or more.
Next, the step of providing an R2-Cu—Ga—Fe based alloy will be described. R2-Cu—Ga—Fe based alloy can be provided by a method of producing a raw material alloy that is adopted in generic production methods for Nd-Fe-B based sintered magnets or the like, e.g., a mold casting method, a strip casting method, a single roll rapid quenching method (a melt spinning method), an atomizing method, or the like. Moreover, the R2-Cu—Ga—Fe based alloy may be what is obtained by pulverizing an alloy obtained as above with a known pulverization means such as a pin mill. Moreover, for improved pulverizability of the alloy as obtained above, before the pulverization, a heat treatment may be performed at 700° C. or below in a hydrogen ambient in order to allow hydrogen to be contained.
(Step of Performing First Heat Treatment)
While at least a portion of the R2-Cu—Ga—Fe based alloy is allowed to be in contact with at least a portion of the surface of the R1-T1-B based sintered compact that has been provided as above, a heat treatment is performed at a temperature of not lower than 700° C. and not higher than 1100° C. in a vacuum or an inert gas ambient. In the present disclosure, this heat treatment is referred to as the first heat treatment. This will allow a liquid phase containing Cu, Ga and Fe to occur from the R2-Cu—Ga—Fe based alloy, and this liquid phase will be introduced from the sintered compact surface into the interior through diffusion, via grain boundaries in the R1-T1-B based sintered compact. If the first heat treatment temperature is below 700° C., the amount of liquid phase containing Cu, Ga and Fe may be too little to obtain high Br and high HcJ. On the other hand, if it is above 1100° C., abnormal grain growth of the main phase may occur to lower HcJ. The first heat treatment temperature is preferably not lower than 800° C. and not higher than 1000° C., as this will provide higher Br and higher HcJ. The heat treatment time may be set to an appropriate value depending on the compositions, dimensions, heat treatment temperatures, etc., of the R1-T1-B based sintered compact and the R2-Cu—Ga—Fe based alloy, but it is preferably not less than 5 minutes and not more than 20 hours, more preferably not less than 10 minutes and not more than 15 hours, and still more preferably not less than 30 minutes and not more than 10 hours. Moreover, the R2-Cu—Ga—Fe based alloy is preferably provided in an amount of not less than 2 mass % and not more than 30 mass % with respect to the weight of the R1-T1-B based sintered compact. If the R2-Cu—Ga—Fe based alloy is less than 2 mass % with respect to the weight of the R1-T1-B based sintered compact, HcJ may lower. On the other hand, if it exceeds 30 mass %, Br may lower.
The first heat treatment can be performed by placing an R2-Cu—Ga—Fe based alloy in any arbitrary shape on the surface of the R1-T1-B based sintered compact, and using a known heat treatment apparatus. For example, the surface of the R1-T1-B based sintered compact may be covered by a powder layer of the R2-Cu—Ga—Fe based alloy, and the first heat treatment may be performed. For example, after a slurry obtained by dispersing the R2-Cu—Ga—Fe based alloy in a dispersion medium is applied on the surface of the R1-T1-B based sintered compact, the dispersion medium may be evaporated, thus allowing the R2-Cu—Ga—Fe based alloy and the R1-T1-B based sintered compact to be in contact. As will be indicated in below-described Experimental Examples, the R2-Cu—Ga—Fe based alloy is preferably placed so as to be in contact with at least a surface of the R1-T1-B based sintered compact that is perpendicular to the alignment direction. Regardless of whether the R2-Cu—Ga—Fe alloy is in contact in the alignment direction of the R1-T1-B based sintered compact alone or the R2-Cu—Ga—Fe based alloy is in contact with the entire surface of the R1-T1-B based sintered compact, characteristic features of the present disclosure can be provided, and high Br and high HcJ can be attained. Examples of the dispersion medium may be alcohols (ethanol, etc.), NMP (N-methylpyrrolidone), aldehydes, and ketones. Moreover, the R1-T1-B based sintered compact having undergone the first heat treatment may be subjected to known machining such as severing or cutting.
(Step of Performing Second Heat Treatment)
The R1-T1-B based sintered compact having undergone the first heat treatment is subjected to a heat treatment at a temperature which is not lower than 450° C. and not higher than 600° C. in a vacuum or an inert gas ambient. In the present disclosure, this heat treatment is referred to as the second heat treatment. By performing the second heat treatment, high Br and high HcJ can be obtained. If the temperature of the second heat treatment is below 450° C. or above 600° C., the generated amount of R-T-Ga phase (which typically is an R6T13Z phase (where Z is at least one of Cu and Ga)) may be too little to obtain high Br and high HcJ. The second heat treatment temperature is preferably not lower than 480° C. and not higher than 560° C. This will provide higher HcJ. The heat treatment time may be set to an appropriate value depending on the composition, dimensions, heat treatment temperature, etc., of the R1-T1-B based sintered compact, but it is preferably not less than 5 minutes and not more than 20 hours, more preferably, not less than 10 minutes and not more than 15 hours, and still more preferably not less than 30 minutes and not more than 10 hours.
In the aforementioned R6T13Z phase (R6T13Z compound), R is at least one rare-earth element which always includes at least one of Pr and Nd, and T is at least one transition metal element which always includes Fe. A representative R6T13Z compound is an Nd6Fe13Ga compound. Moreover, the R6T13Z compound has an La6Co11Ga3 type crystal structure. Depending on its state, the R6T13Z compound may have taken the form of an R6T13−δZ1+δ compound. If Cu, Al and Si are contained relatively profusely in the sintered R-T-B based magnet, it may have taken the form of R6T13−δ (Ga1-a-b-cCuaAlbSic)1+δ.
A sintered R-T-B based magnet which is obtained through the step of performing the second heat treatment may be subjected to known surface treatments, e.g., known machining such as severing or cutting, or plating to confer anticorrosiveness.
<Second Embodiment of a Method for Producing a Sintered R-T-B Based Magnet>
In the first embodiment, in order to introduce R, Ga and Fe elements from the sintered compact surface into the interior, the first heat treatment is performed while an R1-T1-B based sintered compact having a low B amount and an R2-Cu—Ga—Fe based alloy are kept in contact. However, the method of producing a sintered R-T-B based magnet according to the present disclosure is not limited to that of the first embodiment.
First, instead of an R2-Cu—Ga—Fe based alloy, an R2-Ga—Fe based alloy that contains no Cu may be used. In the case of using an R2-Ga—Fe based alloy, however, the R1-T1-B based sintered compact before diffusion needs to contain Cu. An R1-T1-B based sintered compact that contains Cu before diffusion may be referred to as an “R1-T1-Cu—B based sintered compact”.
As shown in
Except for containing Cu, the R1-T1-Cu—B based sintered compact in step S10a of
Preferably, Fe being contained in the R2-Ga—Fe based alloy accounts for not less than 10 mass % and not more than 45 mass % of the entire R2-Ga—Fe based alloy. More preferably, Fe accounts for not less than 15 mass % and not more than 40 mass %, as this will provide higher Br and higher HcJ. Note that the R2-Ga—Fe based alloy is preferably prescribed so that a total of R2, Ga and Fe accounts for 100 mass %.
The present disclosure will be described in more detail by way of Examples; however, the present disclosure is not limited thereto.
Respective elements were weighed so that the R1-T1-B based sintered compact would approximately result in a composition indicated in Table 1, and through casting by a strip casting method, a raw material alloy in flake form having a thickness of 0.2 to 0.4 mm was obtained. After the resultant raw material alloy in flake form was hydrogen-pulverized, it was subjected to a dehydrogenation treatment of heating to 550° C. in a vacuum and then cooling, whereby a coarse-pulverized powder was obtained. Next, to the resultant coarse-pulverized powder, zinc stearate was added as a lubricant in an amount of 0.04 mass % relative to 100 mass % of coarse-pulverized powder; after mixing, an airflow crusher (jet mill machine) was used to effect dry milling in a nitrogen jet, whereby a fine-pulverized powder (alloy powder) with a particle size D50 of 4 μm was obtained. Note that the particle size D50 is a central value of volume (volume median particle diameter) as obtained by a laser diffraction method by airflow dispersion technique.
To the fine-pulverized powder, zinc stearate was added as a lubricant in an amount of 0.05 mass % relative to 100 mass % of fine-pulverized powder; after mixing, the fine-pulverized powder was pressed in a magnetic field, whereby a compact was obtained. As a pressing apparatus, a so-called orthogonal magnetic field pressing apparatus (transverse magnetic field pressing apparatus) was used, in which the direction of magnetic field application ran orthogonal to the pressurizing direction.
In a vacuum, the resultant compact was sintered for 4 hours at not lower than 1000° C. and not higher than 1050° C. (for each sample, a temperature was selected at which a sufficiently dense texture would result through sintering) and thereafter rapidly cooled, whereby an R1-T1-B based sintered compact was obtained. The resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of the resultant sintered compact is shown in Table 1. The respective components in Table 1 were measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPV-1017 (manufactured by Shimadzu Corporation)). The oxygen amount in the sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %. Note that the composition, the oxygen amount, and the carbon amount in Table 1 do not total to 100 mass %. This is because the method of analysis differs for each component. The same also applies to any other tables.
[Step of Providing R2-Cu—Ga—Fe Based Alloy]
Respective elements were weighed so that the R2-Cu—Ga—Fe based alloy would approximately result in the compositions indicated in Table 2, and these raw materials were melted; thus, by a single roll rapid quenching method (melt spinning method), alloys in ribbon or flake form were obtained. Using a mortar, the resultant alloy was pulverized in an argon ambient, and thereafter was passed through a sieve with an opening of 425 μm, thereby providing an R2-Cu—Ga—Fe based alloy. The composition of the resultant R2-Cu—Ga—Fe based alloy is shown in Table 2. As Comparative Example, an R2-Cu—Ga based alloy (1-a) not containing Fe was also provided. The compositions of the resultant R2-Cu—Ga based alloys are shown in Table 2. The respective components in Table 2 were measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPE-9000 (manufactured by Shimadzu Corporation)).
[Step of Performing First Heat Treatment]
The R1-T1-B based sintered compact of Table 1 was severed and cut into a 4.4 mm×10.0 mm×11.0 mm rectangular solid (where a 10.0 mm×11.0 mm face defined a cross section perpendicular to the alignment direction). Next, as shown in
[Step of Performing Second Heat Treatment]
In argon which was controlled to a reduced pressure of 200 Pa, by using a tubular flow furnace, the R1-T1-B based sintered compact having undergone the first heat treatment was subjected to the second heat treatment based on the temperature and time indicated for the second heat treatment in Table 3, followed by cooling. In order to remove any thickened portion in the R2-Cu—Ga—Fe based alloy or the R2-Cu—Ga based alloy existing in the surface vicinity of each sample after the heat treatment, a surface grinder was used to cut on the entire surface of each sample, whereby samples respectively in the form of a 4.0 mm×4.0 mm×4.0 mm cube (sintered R-T-B based magnet) were obtained. Note that the heating temperature for the R2-Cu—Ga—Fe alloy or R2-Cu—Ga based alloy and the R1-T1-B based sintered compact in the step of performing the first heat treatment and the heating temperature for the R1-T1-B based sintered compact in the step of performing the second heat treatment were each measured by attaching a thermocouple.
[Sample Evaluations]
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 3. In
In the following, magnetic characteristics were evaluated by a similar method. As shown in Table 3 and in
Moreover, results of analyzing the components of each entire sample in a 4.0 mm×4.0 mm×4.0 mm cube form by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPV-1017 (manufactured by Shimadzu Corporation)) are shown in Table 4. Furthermore, results of cutting out samples in a 1.0 mm×1.0 mm×1.0 mm cube form, from a magnet surface portion at a cross section perpendicular to the alignment direction and from the magnet central portion of the sample in a 4.0 mm×4.0 mm×4.0 mm cube form, and analyzing their components by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPE-9000 (manufactured by Shimadzu Corporation)) are shown in Table 4. The positions of cutting were the positions shown in
Sintered compacts were produced by the same method as in Experimental Example 1, except for weighing respective elements so that the sintered compacts would approximately result in the compositions in Table 5. Each resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of each resultant sintered compact is shown in Table 5. The respective components in Table 5 were measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPV-1017 (manufactured by Shimadzu Corporation)). The oxygen amount in each sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %.
R2-Cu—Ga—Fe based alloys were provided by the same method as in Experimental Example 1, except for weighing respective elements so that the R2-Cu—Ga—Fe based alloys would approximately result in the compositions indicated in Table 6. The compositions of the R2-Cu—Ga—Fe based alloys, as measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPE-9000 (manufactured by Shimadzu Corporation)), are shown in Table 6.
[Step of Performing First Heat Treatment]
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperatures and time indicated for the first heat treatment in Table 7, the first heat treatment was performed by the same method as in Experimental Example 1.
[Step of Performing Second Heat Treatment]
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperatures and times indicated for the second heat treatment in Table 7, the second heat treatment was performed by the same method as in Experimental Example 1. Each sample after the heat treatment was processed by the same method as in Experimental Example 1, thereby providing a sintered R-T-B based magnet.
[Sample Evaluations]
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 7. In
Moreover, results of analyzing the components of each entire sample in a 4.0 mm×4.0 mm×4.0 mm cube form by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPV-1017 (manufactured by Shimadzu Corporation)) are shown in Table 8. Furthermore, using a method similar to that of Example 1, results of cutting out samples in a 1.0 mm×1.0 mm×1.0 mm cube form, from a magnet surface portion at a cross section perpendicular to the alignment direction and from the magnet central portion of the sample in a 4.0 mm×4.0 mm×4.0 mm cube form, and analyzing their components by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPE-9000 (manufactured by Shimadzu Corporation)) are shown in Table 8.
As shown in Table 7, Table 8, and
[Step of Providing R1-T1-B Based Sintered Compact]
Sintered compacts were produced by the same method as in Experimental Example 1, except for weighing respective elements so that the sintered compacts would approximately result in the compositions in Table 9. Each resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of each resultant sintered compact is shown in Table 9. The respective components in Table 9 were measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPV-1017 (manufactured by Shimadzu Corporation)). The oxygen amount in each sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %.
[Step of Providing R2-Cu—Ga—Fe Based Alloy]
R2-Cu—Ga—Fe based alloys were provided by the same method as in Experimental Example 1, except for weighing respective elements so that the R2-Cu—Ga—Fe based alloys would approximately result in the compositions indicated in Table 10. The compositions of the R2-Cu—Ga—Fe based alloys, as measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPE-9000 (manufactured by Shimadzu Corporation)), are shown in Table 10. As Comparative Example, an R2-Cu—Fe based alloy (3-c) not containing Ga was also provided. The compositions of the resultant R2-Cu—Fe based alloys are shown in Table 10.
[Step of Performing First Heat Treatment]
Except for heating the R2-Cu—Ga—Fe alloy and R1-T1-B based sintered compact or the R2-Cu—Fe based alloy and R1-T1-B based sintered compact based on the temperature and time indicated for the first heat treatment in Table 11, the first heat treatment was performed by the same method as in Experimental Example 1.
[Step of Performing Second Heat Treatment]
Except for heating the R2-Cu—Ga—Fe alloy and R1-T1-B based sintered compact or the R2-Cu—Fe based alloy and R1-T1-B based sintered compact based on the temperatures and times indicated for the second heat treatment in Table 11, the second heat treatment was performed by the same method as in Experimental Example 1. Each sample after the heat treatment was processed by the same method as in Experimental Example 1, thereby providing a sintered R-T-B based magnet.
[Sample Evaluations]
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 11. In
Moreover, results of analyzing the components of each entire sample in a 4.0 mm×4.0 mm×4.0 mm cube form by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPV-1017 (manufactured by Shimadzu Corporation)) are shown in Table 12. Furthermore, using a method similar to that of Example 1, results of cutting out samples in a 1.0 mm×1.0 mm×1.0 mm cube form, from a magnet surface portion at a cross section perpendicular to the alignment direction and from the magnet central portion of the sample in a 4.0 mm×4.0 mm×4.0 mm cube form, and analyzing their components by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPE-9000 (manufactured by Shimadzu Corporation)) are shown in Table 12.
As shown in Table 11, Table 12, and in
[Step of Providing R1-T1-B Based Sintered Compact]
A sintered compact was produced by the same method as in Experimental Example 1, except for weighing respective elements so that the sintered compact would approximately result in the composition in Table 13, and except for the oxygen amount being adjusted to 0.4 to 0.7 mass %. The resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of the resultant sintered compact is shown in Table 13. The respective components in Table 13 were measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPV-1017 (manufactured by Shimadzu Corporation)). The oxygen amount in the sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.5 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %.
[Step of Providing R2-Cu—Ga—Fe Based Alloy]
An R2-Cu—Ga—Fe based alloy was provided by the same method as in Experimental Example 1, except for weighing respective elements so that the R2-Cu—Ga—Fe based alloy would approximately result in the composition indicated in Table 14. The composition of the R2-Cu—Ga—Fe based alloy, as measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPE-9000 (manufactured by Shimadzu Corporation)), is shown in Table 14.
[Step of Performing First Heat Treatment]
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperatures and time indicated for the first heat treatment in Table 15, the first heat treatment was performed by the same method as in Experimental Example 1.
[Step of Performing Second Heat Treatment]
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperature and time indicated for the second heat treatment in Table 15, the second heat treatment was performed by the same method as in Experimental Example 1. Each sample after the heat treatment was processed by the same method as in Experimental Example 1, thereby providing a sintered R-T-B based magnet.
[Sample Evaluations]
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 15. In
Moreover, results of analyzing the components of each entire sample in a 4.0 mm×4.0 mm×4.0 mm cube form by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPV-1017 (manufactured by Shimadzu Corporation)) are shown in Table 16. Furthermore, using a method similar to that of Example 1, results of cutting out samples in a 1.0 mm×1.0 mm×1.0 mm cube form, from a magnet surface portion at a cross section perpendicular to the alignment direction and from the magnet central portion of the sample in a 4.0 mm×4.0 mm×4.0 mm cube form, and analyzing their components by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPE-9000 (manufactured by Shimadzu Corporation)) are shown in Table 16.
As shown in Table 15, Table 16, and in
[Step of Providing R1-T1-B Based Sintered Compact]
Sintered compacts were produced by the same method as in Experimental Example 1, except for weighing respective elements so that the sintered compacts would approximately result in the compositions in Table 17. Each resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of each resultant sintered compact is shown in Table 17. The respective components in Table 17 were measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPV-1017 (manufactured by Shimadzu Corporation)). The oxygen amount in each sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %.
[Step of Providing R2-Cu—Ga—Fe Based Alloy]
An R2-Cu—Ga—Fe based alloy was provided by the same method as in Experimental Example 1, except for weighing respective elements so that the R2-Cu—Ga—Fe based alloy would approximately result in the composition indicated in Table 18. The composition of the R2-Cu—Ga—Fe based alloy, as measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPE-9000 (manufactured by Shimadzu Corporation)), is shown in Table 18.
[Step of Performing First Heat Treatment]
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperatures and time indicated for the first heat treatment in Table 19, the first heat treatment was performed by the same method as in Experimental Example 1.
[Step of Performing Second Heat Treatment]
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperature and time indicated for the second heat treatment in Table 19, the second heat treatment was performed by the same method as in Experimental Example 1. Each sample after the heat treatment was processed by the same method as in Experimental Example 1, thereby providing a sintered R-T-B based magnet.
[Sample Evaluations]
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 19. In
Moreover, results of analyzing the components of each entire sample in a 4.0 mm×4.0 mm×4.0 mm cube form by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPV-1017 (manufactured by Shimadzu Corporation)) are shown in Table 20. Furthermore, using a method similar to that of Example 1, results of cutting out samples in a 1.0 mm×1.0 mm×1.0 mm cube form, from a magnet surface portion at a cross section perpendicular to the alignment direction and from the magnet central portion of the sample in a 4.0 mm×4.0 mm×4.0 mm cube form, and analyzing their components by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (apparatus name: ICPE-9000 (manufactured by Shimadzu Corporation)) are shown in Table 20.
As shown in Table 19, Table 20, and in
Respective elements were weighed so that the R1-T1-B based sintered compact would approximately result in compositions indicated as Labels 6-A through 6-I in Table 21, and through casting by a strip casting method, raw material alloys in flake form having a thickness of 0.2 to 0.4 mm were obtained. After each resultant raw material alloy in flake form was hydrogen-pulverized, it was subjected to a dehydrogenation treatment of heating to 550° C. in a vacuum and then cooling, whereby a coarse-pulverized powder was obtained. Next, to the resultant coarse-pulverized powder, zinc stearate was added as a lubricant in an amount of 0.04 mass % relative to 100 mass % of coarse-pulverized powder; after mixing, an airflow crusher (jet mill machine) was used to effect dry milling in a nitrogen jet, whereby a fine-pulverized powder (alloy powder) with a particle size D50 of 4 μm was obtained. Note that the particle size D50 is a central value of volume (volume median particle diameter) as obtained by a laser diffraction method by airflow dispersion technique.
To the fine-pulverized powder, zinc stearate was added as a lubricant in an amount of 0.05 mass % relative to 100 mass % of fine-pulverized powder; after mixing, the fine-pulverized powder was pressed in a magnetic field, whereby a compact was obtained. As a pressing apparatus, a so-called orthogonal magnetic field pressing apparatus (transverse magnetic field pressing apparatus) was used, in which the direction of magnetic field application ran orthogonal to the pressurizing direction.
In a vacuum, the resultant compact was sintered for 4 hours at not lower than 1000° C. and not higher than 1050° C. (for each sample, a temperature was selected at which a sufficiently dense texture would result through sintering) and thereafter rapidly cooled, whereby an R1-T1-B based sintered compact was obtained. Each resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of each resultant sintered compact is shown in Table 21. The respective components in Table 21 were measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The oxygen amount in each sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %. In Table 21, “[T1]/[B]” is a ratio (a/b) between: a total (a) of the respective value of a result of dividing an analysis value (mass %) of each element (which herein are Fe, Al, Si and Mn) composing T1 with the atomic weight of that element; and (b) a result of dividing an analysis value (mass %) of B with the atomic weight of B. The same also applies to all tables below. Note that each composition, oxygen amount, and carbon amount in Table 1 do not total to 100 mass %. This is because the method of analysis differs for each component, as aforementioned. The same also applies to any other tables.
Respective elements were weighed so that the R2-Cu—Ga—Fe based alloy would approximately result in the composition indicated as Label 6-a in Table 22, and these raw materials were melted; thus, by a single roll rapid quenching method (melt spinning method), an alloy in ribbon or flake form was obtained. Using a mortar, the resultant alloy was pulverized in an argon ambient, and thereafter was passed through a sieve with an opening of 425 μm, thereby providing an R2-Cu—Ga—Fe based alloy. The composition of the resultant R2-Cu—Ga—Fe based alloy is shown in Table 22. The respective components in Table 22 were measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES).
The R1-T1-B based sintered compacts of Labels 6-A through 6-I in Table 21 were severed and cut into a 4.4 mm×10.0 mm×11.0 mm rectangular solid (where a 10.0 mm×11.0 mm face defined a face perpendicular to the alignment direction). Next, as shown in
In argon which was controlled to a reduced pressure of 200 Pa, by using a tubular flow furnace, the R1-T1-B based sintered compact having undergone the first heat treatment was subjected to the second heat treatment based on the temperature and times indicated for the second heat treatment in Table 23, followed by cooling. In order to remove any thickened portion in the R2-Cu—Ga—Fe based alloy existing in the surface vicinity of each sample after the heat treatment, a surface grinder was used to cut on the entire surface of each sample, whereby samples respectively in the form of a 4.0 mm×4.0 mm×4.0 mm cube (sintered R-T-B based magnet) were obtained. Note that the heating temperature for the R2-Cu—Ga—Fe alloy and R1-T1-B based sintered compact in the step of performing the first heat treatment and the heating temperature for the R1-T1-B based sintered compact in the step of performing the second heat treatment were each measured by attaching a thermocouple.
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 23. As shown in Table 23, examples of the present invention in which the R1-T1-B based sintered compact had a molar ratio [T1]/[B] greater than 14.0 but not greater than 15.0 all attained high Br and high HcJ. On the other hand, in sample Nos. 6-5 and 6-6 in which the molar ratio [T1]/[B] was 14.0 or smaller, HcJ had greatly reduced. Moreover, in sample No. 6-1 in which the molar ratio [T1]/[B] exceeded 15.0, Br had greatly reduced.
A sintered compact was produced by the same method as in Experimental Example 6, except for weighing respective elements so that the R1-T1-B based sintered compact would approximately result in the composition indicated as Label 7-A in Table 24. The resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of the resultant sintered compact is shown in Table 24. Respective components in Table 24 were measured by the same method as in Experimental Example 6. The oxygen amount in the sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %.
R2-Cu—Ga—Fe based alloys were provided by the same method as in Experimental Example 6, except for weighing respective elements so that the R2-Cu—Ga—Fe based alloys would approximately result in the compositions indicated as Labels 7-a through 7-i in Table 25. The compositions of the R2-Cu—Ga—Fe based alloys are shown in Table 25. Respective components in Table 25 were measured by the same method as in Experimental Example 6.
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperature and time indicated for the first heat treatment in Table 26, the first heat treatment was performed by the same method as in Experimental Example 6.
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperature and time indicated for the second heat treatment in Table 26, the second heat treatment was performed by the same method as in Experimental Example 6. Each sample after the heat treatment was processed by the same method as in Experimental Example 6, thereby providing a sintered R-T-B based magnet.
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 26. As shown in Table 26, examples of the present invention in which the R-Cu—Ga—Fe based alloy had an Fe amount of not less than 10 mass % and not more than 45 mass % attained high Br and high HcJ. Moreover, when the Fe amount in the R-Cu—Ga—Fe based alloy accounted for not less than 15 mass % and not more than 40 mass % of (sample Nos. 7-4 to 7-7), even higher Br and higher HcJ were obtained. On the other hand, in sample Nos. 7-1 and 7-2, in which the R-Cu—Ga—Fe based alloy had an Fe amount of 10 mass % or less (5 mass % or less), Br had greatly reduced. In sample No. 7-9, in which the R-Cu—Ga—Fe based alloy had an Fe amount exceeding 45 mass %, HcJ had greatly reduced.
Sintered compacts were produced by the same method as in Experimental Example 6, except for weighing respective elements so that the R1-T1-B based sintered compacts would approximately result in the compositions indicated as Labels 8-A and 8-B in Table 27. Each resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of each resultant sintered compact is shown in Table 27. Respective components in Table 27 were measured by the same method as in Experimental Example 6. The oxygen amount in each sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %.
R2-Cu—Ga—Fe based alloys were provided by the same method as in Experimental Example 6, except for weighing respective elements so that the R2-Cu—Ga—Fe based alloys would approximately result in the compositions indicated as Labels 8-a through 8-p in Table 28. The compositions of the R2-Cu—Ga—Fe based alloys are shown in Table 28. Respective components in Table 28 were measured by the same method as in Experimental Example 6.
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperature and time indicated for the first heat treatment in Table 29, the first heat treatment was performed by the same method as in Experimental Example 6.
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperature and time indicated for the second heat treatment in Table 29, the second heat treatment was performed by the same method as in Experimental Example 6. Each sample after the heat treatment was processed by the same method as in Experimental Example 6, thereby providing a sintered R-T-B based magnet.
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 29. As shown in Table 29, high Br and high HcJ were attained by examples of the present invention in which the R2 amount in the R2-Cu—Ga—Fe based alloy was not less than 35 mass % and not more than 85 mass %, the Ga amount was not less than 2.5 mass % and not more than 40 mass %, and the Cu amount was not less than 2.5 mass % and not more than 40 mass % On the other hand, if any of R, Cu and Ga in the R2-Cu—Ga—Fe based alloy was outside the ranges according to the present disclosure (i.e., Labels 8-a and 8-d had their R2 outside the range; Labels 8-e, 8-i, and 8-o had their Ga outside the range; Labels 8-j and 8-n had their Cu outside the range; and Label 8-p had its Cu and Ga outside the range), high HcJ could not be obtained. Thus, high Br and high HcJ are being obtained because of the R, Cu and Ga (and Fe, as indicated in Experimental Example 7) contents falling within the ranges according to the present disclosure.
A sintered compact was produced by the same method as in Experimental Example 6, except for weighing respective elements so that the R1-T1-B based sintered compact would approximately result in the composition indicated as Label 9-A in Table 30. The resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of the resultant sintered compact is shown in Table 30. Respective components in Table 30 were measured by the same method as in Experimental Example 6. The oxygen amount in the sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %.
An R2-Cu—Ga—Fe based alloy was provided by the same method as in Experimental Example 6, except for weighing respective elements so that the R2-Cu—Ga—Fe based alloy would approximately result in the composition indicated as Label 9—in Table 31. The composition of the R2-Cu—Ga—Fe based alloy is shown in Table 31. Respective components in Table 31 were measured by the same method as in Experimental Example 6.
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperatures and time indicated for the first heat treatment in Table 32, the first heat treatment was performed by the same method as in Experimental Example 6.
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperatures and time indicated for the second heat treatment in Table 32, the second heat treatment was performed by the same method as in Experimental Example 6. Each sample after the heat treatment was processed by the same method as in Experimental Example 6, thereby providing a sintered R-T-B based magnet.
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 32. As shown in Table 32, examples of the present invention satisfying the first heat treatment temperature (not lower than 700° C. and not higher than 1100° C.) and second heat treatment temperature (not lower than 450° C. and not higher than 600° C.) according to the present disclosure attained high Br and high HcJ. Moreover, as shown in Table 32, when the temperature of the first heat treatment was not lower than 800° C. and not higher than 1000° C. and the temperature of the second heat treatment was not lower than 480° C. and not higher than 560° C., even higher HcJ was obtained. On the other hand, when either the first heat treatment temperature or the second heat treatment temperature was outside the range according to the present disclosure (sample No. 9-1 was outside the range with respect to its first heat treatment; and sample Nos. 9-5 and 9-11 were outside the range with respect to their second heat treatment), high HcJ could not be obtained.
Sintered compacts were produced by the same method as in Experimental Example 6, except for weighing respective elements so that the R1-T1-B based sintered compacts would approximately result in the compositions indicated as Labels 10-A and 5-B in Table 33. Each resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of each resultant sintered compact is shown in Table 33. Respective components in Table 33 were measured by the same method as in Experimental Example 6. The oxygen amount in each sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %. In Table 33, “[T1]/[B]” is a ratio (a/b) between: a total (a) of the respective value of a result of dividing an analysis value (mass %) of each element (which herein are Fe, Co, Al, Si and Mn) composing T1 with the atomic weight of that element; and (b) a result of dividing an analysis value (mass %) of B with the atomic weight of B.
An R2-Cu—Ga—Fe based alloy was provided by the same method as in Experimental Example 6, except for weighing respective elements so that the R2-Cu—Ga—Fe based alloy would approximately result in the composition indicated as Label 10-a in Table 34. The composition of the R2-Cu—Ga—Fe based alloy is shown in Table 34. Respective components in Table 34 were measured by the same method as in Experimental Example 1.
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperatures and time indicated for the first heat treatment in Table 35, the first heat treatment was performed by the same method as in Experimental Example 6.
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperature and times indicated for the second heat treatment in Table 35, the second heat treatment was performed by the same method as in Experimental Example 6. Each sample after the heat treatment was processed by the same method as in Experimental Example 6, thereby providing a sintered R-T-B based magnet.
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 35. Results of measuring the components of each sample by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) are shown in Table 35. As shown in Table 35, high Br and high HcJ were obtained even when the R1-T1-B based sintered compact contained Dy, Co, Ga, Cu or Zr.
A sintered compact was produced by the same method as in Experimental Example 6, except for weighing respective elements so that the R1-T1-B based sintered compact would approximately result in the composition indicated as Label 11-A in Table 36. The resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of the resultant sintered compact is shown in Table 36. Respective components in Table 36 were measured by the same method as in Experimental Example 6. The oxygen amount in the sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %.
R2-Cu—Ga—Fe based alloys were provided by the same method as in Experimental Example 6, except for weighing respective elements so that the R2-Cu—Ga—Fe based alloys would approximately result in the compositions indicated as Labels 11-a and 11-b in Table 37. The compositions of the R2-Cu—Ga—Fe based alloys are shown in Table 37. Respective components in Table 37 were measured by the same method as in Experimental Example 6.
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperature and time indicated for the first heat treatment in Table 38, the first heat treatment was performed by the same method as in Experimental Example 6.
Except for heating the R2-Cu—Ga—Fe alloy and the R1-T1-B based sintered compact based on the temperature and time indicated for the second heat treatment in Table 38, the second heat treatment was performed by the same method as in Experimental Example 6. Each sample after the heat treatment was processed by the same method as in Experimental Example 6, thereby providing a sintered R-T-B based magnet.
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 38. As shown in Table 38, high Br and high HcJ were obtained even when the R2-Cu—Ga—Fe based alloy contained Co or Zn.
Respective elements were weighed so that the R1-T1-Cu—B based sintered compact would approximately result in the compositions indicated as Labels 12-A through 12-L in Table 39, and through casting by a strip casting method, raw material alloys in flake form having a thickness of 0.2 to 0.4 mm were obtained. After each resultant raw material alloy in flake form was hydrogen-pulverized, it was subjected to a dehydrogenation treatment of heating to 550° C. in a vacuum and then cooling, whereby a coarse-pulverized powder was obtained. Next, to the resultant coarse-pulverized powder, zinc stearate was added as a lubricant in an amount of 0.04 mass % relative to 100 mass % of coarse-pulverized powder; after mixing, an airflow crusher (jet mill machine) was used to effect dry milling in a nitrogen jet, whereby a fine-pulverized powder (alloy powder) with a particle size D50 of 4 μm was obtained. Note that the particle size D50 is a central value of volume (volume median particle diameter) as obtained by a laser diffraction method by airflow dispersion technique.
To the fine-pulverized powder, zinc stearate was added as a lubricant in an amount of 0.05 mass % relative to 100 mass % of fine-pulverized powder; after mixing, the fine-pulverized powder was pressed in a magnetic field, whereby a compact was obtained. As a pressing apparatus, a so-called orthogonal magnetic field pressing apparatus (transverse magnetic field pressing apparatus) was used, in which the direction of magnetic field application ran orthogonal to the pressurizing direction.
In a vacuum, the resultant compact was sintered for 4 hours at not lower than 1000° C. and not higher than 1050° C. (for each sample, a temperature was selected at which a sufficiently dense texture would result through sintering) and thereafter rapidly cooled, whereby an R1-T1-Cu—B based sintered compact was obtained. Each resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of each resultant sintered compact is shown in Table 39. The respective components in Table 39 were measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The oxygen amount in each sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %. In Table 39, “[T1]/[B]” is a ratio (a/b) between: a total (a) of the respective value of a result of dividing an analysis value (mass %) of each element (which herein are Fe, Al, Si and Mn) composing T1 with the atomic weight of that element; and (b) a result of dividing an analysis value (mass %) of B with the atomic weight of B. The same also applies to all tables below. Note that each composition, oxygen amount, and carbon amount in Table 39 do not total to 100 mass %. This is because the method of analysis differs for each component, as aforementioned. The same also applies to any other tables.
Respective elements were weighed so that the R2-Ga—Fe based alloy would approximately result in the composition indicated as Label 12-a in Table 40, and these raw materials were melted; thus, by a single roll rapid quenching method (melt spinning method), an alloy in ribbon or flake form was obtained. Using a mortar, the resultant alloy was pulverized in an argon ambient, and thereafter was passed through a sieve with an opening of 425 μm, thereby providing an R2-Ga—Fe based alloy. The composition of the resultant R2-Ga—Fe based alloy is shown in Table 40. The respective components in Table 40 were measured by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES).
The R1-T1-Cu—B based sintered compact of Labels 12-A through 12-L in Table 39 were severed and cut into a 4.4 mm×10.0 mm×11.0 mm rectangular solid (where a 10.0 mm×11.0 mm face defined a face perpendicular to the alignment direction). Next, as shown in
In argon which was controlled to a reduced pressure of 200 Pa, by using a tubular flow furnace, the R1-T1-Cu—B based sintered compact having undergone the first heat treatment was subjected to the second heat treatment based on the temperature and times indicated for the second heat treatment in Table 41, followed by cooling. In order to remove any thickened portion in the R2-Ga—Fe based alloy existing in the surface vicinity of each sample after the heat treatment, a surface grinder was used to cut on the entire surface of each sample, whereby samples respectively in the form of a 4.0 mm×4.0 mm×4.0 mm cube (sintered R-T-B based magnet) were obtained. Note that the heating temperature for the R2-Ga—Fe alloy and R1-T1-Cu—B based sintered compact in the step of performing the first heat treatment and the heating temperature for the R1-T1-Cu—B based sintered compact in the step of performing the second heat treatment were each measured by attaching a thermocouple.
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 41. As shown in Table 41, examples of the present invention in which the R1-T1-Cu—B based sintered compact had a molar ratio [T1]/[B] greater than 14.0 but not greater than 15.0 and a Cu content of not less than 0.1 mass % and not more than 1.5 mass % all attained high Br and high HcJ. On the other hand, in sample No. 12-5, in which the molar ratio [T1]/[B] was 14.0 or smaller, HcJ had greatly reduced; and in sample No. 12-1, in which the molar ratio [T1]/[B] exceeded 15.0, Br had greatly reduced. Moreover, in sample No. 12-6 in which the Cu content was less than 0.1 mass %, HcJ had greatly reduced; and in sample No. 12-10, in which the Cu content exceeded 1.5 mass %, Br and HcJ had greatly reduced.
A sintered compact was produced by the same method as in Experimental Example 12, except for weighing respective elements so that the R1-T1-Cu—B sintered compact would approximately result in the composition indicated as Label 13-A in Table 42. The resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of the resultant sintered compact is shown in Table 42. Respective components in Table 42 were measured by the same method as in Experimental Example 12. The oxygen amount in the sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %.
R2-Ga—Fe based alloys were provided by the same method as in Experimental Example 12, except for weighing respective elements so that the R2-Ga—Fe based alloys would approximately result in the compositions indicated as Labels 13-a through 13-h in Table 43. The compositions of the R2-Ga—Fe based alloys composition are shown in Table 43. Respective components in Table 43 were measured by the same method as in Experimental Example 12.
Except for heating the R2-Ga—Fe alloy and the R1-T1-Cu—B based sintered compact based on the temperature and time indicated for the first heat treatment in Table 44, the first heat treatment was performed by the same method as in Experimental Example 12.
Except for heating the R2-Ga—Fe alloy and the R1-T1-Cu—B based sintered compact based on the temperature and time indicated for the second heat treatment in Table 44, the second heat treatment was performed by the same method as in Experimental Example 12. Each sample after the heat treatment was processed by the same method as in Experimental Example 12, thereby providing a sintered R-T-B based magnet.
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 44. As shown in Table 44, examples of the present invention in which the R2-Ga—Fe based alloy had an Fe amount of not less than 10 mass % and not more than 45 mass % attained high Br and high HcJ. Moreover, when the Fe amount in the R—Ga—Fe based alloy accounted for not less than 15 mass % and not more than 40 mass % of (sample Nos. 13-4 and 13-6), even higher Br and higher HcJ were obtained. On the other hand, in sample Nos. 13-1 and 13-2, in which the R—Ga—Fe based alloy had an Fe amount of 10 mass % or less (5 mass % or less), Br had greatly reduced. In sample No. 13-8, in which the Ru-Ga—Fe based alloy had an Fe amount exceeding 45 mass %, HcJ had greatly reduced.
A sintered compact was produced by the same method as in Experimental Example 12, except for weighing respective elements so that the R1-T1-Cu—B sintered compact would approximately result in the composition indicated as Label 14-A in Table 45. The resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of the resultant sintered compact is shown in Table 45. Respective components in Table 45 were measured by the same method as in Experimental Example 12. The oxygen amount in the sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %.
R2-Ga—Fe based alloys were provided by the same method as in Experimental Example 12, except for weighing respective elements so that the R2-Ga—Fe based alloys would approximately result in the compositions indicated as Labels 14-a through 14-i in Table 46. The compositions of the R2-Ga—Fe based alloys are shown in Table 46. Respective components in Table 46 were measured by the same method as in Experimental Example 12.
Except for heating the R2-Ga—Fe alloy and the R1-T1-Cu—B based sintered compact based on the temperature and time indicated for the first heat treatment in Table 47, the first heat treatment was performed by the same method as in Experimental Example 12.
Except for heating the R2-Ga—Fe alloy and the R1-T1-Cu—B based sintered compact based on the temperature and time indicated for the second heat treatment in Table 47, the second heat treatment was performed by the same method as in Experimental Example 12. Each sample after the heat treatment was processed by the same method as in Experimental Example 12, thereby providing a sintered R-T-B based magnet.
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 47. As shown in Table 47, high Br and high HcJ were attained by examples of the present invention in which the R amount in the R2-Ga—Fe based alloy was not less than 35 mass % and not more than 85 mass %, and the Ga amount was not less than 2.5 mass % and not more than 40 mass %. On the other hand, if either R or Ga in the R2-Ga—Fe based alloy was outside the range according to the present disclosure (Label 14-a had its R2 outside the range; Label sample No. 14-d had its Ga outside the range; and Label 14-h had its R2 and Ga outside the ranges), high HcJ could not be obtained. Thus, high Br and high HcJ are being obtained because of the R and Ga (and Fe, as indicated in Experimental Example 13) contents falling within the ranges according to the present disclosure.
A sintered compact was produced by the same method as in Experimental Example 12, except for weighing respective elements so that the R1-T1-Cu—B sintered compact would approximately result in the composition indicated as Label 15-A in Table 48. The resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of the resultant sintered compact is shown in Table 48. Respective components in Table 48 were measured by the same method as in Experimental Example 12. The oxygen amount in the sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %.
An R2-Ga—Fe based alloy was provided by the same method as in Experimental Example 12, except for weighing respective elements so that the R2-Ga—Fe based alloy would approximately result in the composition indicated as Label 15-a in Table 49. The composition of the R2-Ga—Fe based alloy is shown in Table 49. Respective components in Table 49 were measured by the same method as in Experimental Example 12.
Except for heating the R2-Ga—Fe alloy and the R1-T1-Cu—B based sintered compact based on the temperatures and time indicated for the first heat treatment in Table 50, the first heat treatment was performed by the same method as in Experimental Example 12.
Except for heating the R2-Ga—Fe alloy and the R1-T1-Cu—B based sintered compact based on the temperatures and time indicated for the second heat treatment in Table 50, the second heat treatment was performed by the same method as in Experimental Example 12. Each sample after the heat treatment was processed by the same method as in Experimental Example 12, thereby providing a sintered R-T-B based magnet.
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 50. As shown in Table 53, examples of the present invention satisfying the first heat treatment temperature (not lower than 700° C. and not higher than 1100° C.) and second heat treatment temperature (not lower than 450° C. and not higher than 600° C.) according to the present disclosure attained high Br and high HcJ. Moreover, as shown in Table 50, when the temperature of the first heat treatment was not lower than 800° C. and not higher than 1000° C. and the temperature of the second heat treatment was not lower than 480° C. and not higher than 560° C., even higher HcJ was obtained. On the other hand, when either the first heat treatment temperature or the second heat treatment temperature was outside the range according to the present disclosure (sample No. 15-1 was outside the range with respect to its first heat treatment; and sample Nos. 15-5 and 15-11 were outside the range with respect to their second heat treatment), high HcJ could not be obtained.
Sintered compacts were produced by the same method as in Experimental Example 12, except for weighing respective elements so that the R1-T1-Cu—B based sintered compacts would approximately result in the compositions indicated as Labels 16-A and 16-B in Table 51. Each resultant sintered compact had a density of 7.5 Mg/m3 or more. A component analysis of each resultant sintered compact is shown in Table 51. Respective components in Table 51 were measured by the same method as in Experimental Example 12. The oxygen amount in each sintered compact was measured by a gas fusion infrared absorption method, which all indicated a value around 0.2 mass %. The C (carbon amount) was measured with a gas analyzer based on a combustion-infrared absorption method, which indicated a value around 0.1 mass %. In Table 51, “[T1]/[B]” is a ratio (a/b) between: a total (a) of the respective value of a result of dividing an analysis value (mass %) of each element (which herein are Fe, Co, Al, Si and Mn) composing T1 with the atomic weight of that element; and (b) a result of dividing an analysis value (mass %) of B with the atomic weight of B.
An R2-Ga—Fe based alloy was provided by the same method as in Experimental Example 12, except for weighing respective elements so that the R2-Ga—Fe based alloy would approximately result in the composition indicated as Label 16-a in Table 52. The composition of the R2-Ga—Fe based alloy is shown in Table 52. Respective components in Table 52 were measured by the same method as in Experimental Example 12.
Except for heating the R2-Ga—Fe alloy and the R1-T1-Cu—B based sintered compact based on the temperatures and time indicated for the first heat treatment in Table 53, the first heat treatment was performed by the same method as in Experimental Example 12.
Except for heating the R2-Ga—Fe alloy and the R1-T1-Cu—B based sintered compact based on the temperature and times indicated for the second heat treatment in Table 53, the second heat treatment was performed by the same method as in Experimental Example 12. Each sample after the heat treatment was processed by the same method as in Experimental Example 12, thereby providing a sintered R-T-B based magnet.
With respect to the resultant samples, Br and HcJ of each sample were measured by using a B—H tracer. Results of measurement are shown in Table 53. Results of measuring the components of each sample by using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) are shown in Table 53. As shown in Table 53, high Br and high HcJ were obtained even when the R1-T1-Cu—B based sintered compact contained Dy, Co, Ga, Cu or Zr.
A sintered R-T-B based magnet obtained according to the present invention can be suitably used in voice coil motors (VCM) of hard disk drives, various types of motors such as motors for electric vehicles (EV, HV, PHV, etc.) and motors for industrial equipment, home appliance products, and the like.
1 R1-T1-B based sintered compact (R1-T1-Cu—B based sintered compact)
2 R2-Cu—Ga—Fe based alloy (R2-Ga—Fe based alloy)
3 process chamber
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-233929 | Dec 2016 | JP | national |
| 2016-233930 | Dec 2016 | JP | national |
| 2016-251306 | Dec 2016 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/043058 | 11/30/2017 | WO | 00 |
