Rare earth magnet materials and magnets

Abstract

To provide a rare earth magnet material presenting a higher coercive force, and a magnet.SOLUTION: In a rare earth magnet material according to the present invention, the content of M (at least one element selected from among Zr, Ti, Hf, V, Nb, Ta, Cr, Mo and W) is 1.6 atom% or more and 5.0 atom% or less, the content of Sm is 7.0 atom% or more and 11.0 atom% or less, the content of N is 11.0 atom% or more and 19.5 atom% or less, and the content of Fe is 69.5 atom% or more and 82.0 atom% or less, and the rare earth magnet material contains C.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to rare earth magnet materials and magnets.

Background Art

[0002] As one of the rare earth magnetic materials, a samarium iron nitride-based magnetic material containing samarium (Sm), iron (Fe), and nitrogen (N) is known. The samarium iron nitride-based magnetic material is used, for example, as a raw material for bonded magnets.

[0003] For example, in Patent Document 1, Sm x Fe 100-x-y N v , Sm x Fe 100-x-y-v M 1 y N v , or Sm x Fe 100-x-z-v M 2 z N v [M 1 is Hf or Zr, M 2 is selected from Si, Nb, Ti, Ga, Al, Ta, and C, one or more kinds, 7 ≦ x ≦ 12, 0.5 ≦ v ≦ 20, 0.1 ≦ y ≦ 1.5, and 0.1 ≦ z ≦ 1.0] of powder magnet materials having alloy components are disclosed.

[0004] On the other hand, in Patent Document 2, a SmFeN-based magnet material containing 7.0 to 12 atomic% of Sm, one or more elements selected from the group consisting of Hf, Zr, and Sc of 0.1 to 1.5 atomic%, Si of 0.02 to 0.14 atomic%, C of 0.08 to 0.5 atomic%, N of 10 to 20 atomic%, and Co of 0 to 35 atomic% and the balance being Fe is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] Incidentally, Patent Document 1 describes that magnetic properties can be improved by adding Zr, but that increasing the amount of Zr added leads to the deposition of a soft magnetic phase, which reduces coercivity (for example, paragraph 0022). Furthermore, both Patent Documents 1 and 2 describe that adding C improves the residual magnetic flux density, compensating for insufficient deoxidation during the production of the raw material molten metal, but that if a large amount of C remains in the SmFeN-based magnet, the residual magnetization and coercivity will decrease (for example, paragraph 0024 of Reference Document 1, paragraph 0013 of Reference Document 2).

[0007] The present invention aims to provide rare-earth magnetic materials and magnets that exhibit higher coercivity. [Means for solving the problem]

[0008] The first rare earth magnet material according to the present invention has an Sm content of 7.0 atomic% to 11.0 atomic%, an M (at least one element selected from Zr, Ti, Hf, V, Nb, Ta, Cr, Mo, W) content of 1.6 atomic% to 5.0 atomic%, an N content of 11.0 atomic% to 19.5 atomic%, and an Fe content of 69.5 atomic% to 82.0 atomic%, and also contains C.

[0009] The above-mentioned rare-earth magnet material may contain a crystalline phase (MC phase) mainly composed of M and C.

[0010] The above-mentioned rare earth magnet material may further contain Co, with the Co content being 5 atomic percent or less.

[0011] The magnet according to the present invention comprises a binder and any of the above-mentioned rare earth magnetic materials dispersed within the binder. [Effects of the Invention]

[0012] The rare earth magnet material and magnet of the present invention can achieve higher coercivity. [Brief explanation of the drawing]

[0013] [Figure 1] These are images of Example 2 and Comparative Example 1 observed by a transmission electron microscope (TEM), and elemental mapping images obtained by energy-dispersive X-ray spectroscopy (EDX). [Modes for carrying out the invention]

[0014] The rare earth magnet material of the present invention comprises samarium (Sm), iron (Fe), and nitrogen (N), and also contains M (at least one selected from Zr, Ti, Hf, V, Nb, Ta, Cr, Mo, W) and C.

[0015] Thus, by adding M and C simultaneously, it is possible to create a multicomponent system in which the order of the crystal lattice is easily disrupted due to the coexistence of elements with different physical properties, while also lowering the heat of mixing of the constituent elements and creating a state in which the coexistence of elements is more likely to occur. Furthermore, the presence of C, which has a smaller atomic radius than other elements and can easily penetrate between crystal lattices, makes the order of the crystal lattice composed of Sm and Fe more easily disrupted. For these reasons, the ability to form amorphous structures in thin bands is greatly improved by adding M and C simultaneously. This effect promotes the amorphous formation of rapidly cooled thin bands, as described later, and reduces crystal precipitation in rapidly cooled thin bands. As a result, the generation of coarse crystallites due to heat treatment is suppressed, and the coercivity is increased. In contrast, when the C content is high, C is distributed to phases other than the main phase during cooling, and the MC phase is formed as described below. This further increases the coercivity.

[0016] The rare earth magnet material of this embodiment can be one in which a crystal phase (M-C phase) mainly composed of M and C is precipitated. Due to the precipitation of the non-magnetic M-C phase with a low Fe concentration, the precipitation of the M-Fe phase, which is a soft magnetic phase generated when M is added, is suppressed. As a result, the coercive force increases. Further, due to the precipitation of the non-magnetic M-C phase, the precipitation of Sm-Fe-C phases and the like with a low coercive force generated when C is added is suppressed, and as a result, the coercive force of the entire magnet is improved.

[0017] To precipitate such an M-C phase, for example, the content of M can be set to 1.6 atomic % or more and 5.0 atomic % or less, and more preferably 2.0 atomic % or more and 3.5 atomic % or less. If the content of M is too low, the M-C phase cannot be precipitated, and if the content of M is too high, the precipitation amount of the M-Fe phase, which is a soft magnetic phase, increases. Although the content of C does not need to be determined, for example, the content of C can be set to 0.2 atomic % or more and 2.0 atomic % or less, and more preferably 0.5 atomic % or more and 1.5 atomic % or less. If the content of C is too low, the precipitation of the M-C phase may not occur, and if the content of C is too high, Sm-Fe-C phases and the like may precipitate, and the magnetic properties may deteriorate. When the content of C is less than 0.5 atomic % (for example, 0.1 atomic % or more and less than 0.5 atomic %), the M-C phase may not precipitate, but even in that case, as described above, if M and C are added simultaneously, the coercive force will increase.

[0018] In the SmFeN-based magnetic powder according to the present invention, the content of Sm is, for example, 7.0 atomic % or more and 11.0 atomic % or less, preferably 9.0 atomic % or more and 10.0 atomic % or less. If the content of Sm is low, phases such as α-Fe with low coercive force are likely to precipitate. If the content of Sm is high, the crystallite size of the main phase tends to increase, resulting in a decrease in the coercive force. The content of N can be, for example, 11.0 atomic % or more and 19.5 atomic % or less, preferably 12.0 atomic % or more and 13.0 atomic % or less. In the SmFeN-based magnetic powder according to the present invention, the balance can be Fe. Specifically, the content of Fe can be, for example, 69.5 atomic % or more and 82.0 atomic % or less, preferably 73 atomic % or more and 79 atomic % or less.

[0019] The rare earth magnet material of the present invention may contain any other suitable element.

[0020] For example, the rare earth magnet material of the present invention may contain Co, and may contain Co with a content of 5.0 atomic % or less, preferably 1.0 atomic % or more and 3.0 atomic % or less. When the SmFeN-based magnetic powder contains Co, this can reduce the melt viscosity when producing a magnetic material by the super rapid cooling method described later, thereby reducing the quench loss (raw material loss occurring when obtaining a thin strip) and improving the yield (production efficiency). In the crystal structure of the SmFeN-based magnetic material, Co is considered to be able to substitute for Fe at its position, but the present embodiment is not limited to such a mode.

[0021] For example, the rare earth magnet material of the present invention may further contain one or more of Al and Si. The content of Al is preferably, for example, 0.0 atomic % or more and 10.0 atomic % or less, and more preferably 0.1 atomic % or more and 5.0 atomic % or less. The content of Si is preferably, for example, 0.0 atomic % or more and 1.0 atomic % or less, and more preferably 0.2 atomic % or more and 0.6 atomic % or less. In the crystal structure of the SmFeN-based magnetic powder, Al and Si are considered to be able to substitute for Fe at its position, but the present invention is not limited to such a mode.

[0022] Other elements that may be added include at least one selected from the group consisting of, for example, Nd, Pr, Dy, Tb, La, Ce, Pm, Eu, Gd, Ho, Er, Tm, Ym, Lu, Mn, Ga, Cu, Ni, etc. If such elements are present, their content (the sum of the content of each element if there are multiple elements) may be, for example, 2.0 atomic percent or less, and more specifically, 1.8 atomic percent or less. If O is also present as an unavoidable impurity, its content may be 10.0 atomic percent or less, and more specifically, 5.0 atomic percent or less.

[0023] Furthermore, the total content of each element in the rare earth magnet material does not exceed 100 atomic percent. Theoretically, the total content of all elements that can be contained in the rare earth magnet material equals 100 atomic percent.

[0024] The atomic percentage (A) of each element in rare earth magnet materials can be measured by inductively coupled plasma analysis (ICP-AES). Furthermore, the O and N content can be measured by the inert gas fusion method.

[0025] The rare earth magnet material of the present invention can have any suitable shape. For example, it can be a magnetic powder with a particle size of about 1 to 300 μm. Furthermore, a bonded magnet of the rare earth magnet material can be obtained by mixing the rare earth magnet material with a binder such as resin or plastic and molding and solidifying it into a predetermined shape.

[0026] The rare earth magnet material of the present invention can be manufactured, for example, by an ultra-rapid cooling method. The ultra-rapid cooling method can be carried out as follows. First, a master alloy is prepared by mixing the raw material metals constituting the rare earth magnet material in a desired composition ratio. This master alloy is melted (in a molten state) under an argon atmosphere and sprayed onto a rotating single roll (for example, at a peripheral speed of 30 to 100 m / s), thereby ultra-rapidly cooling to obtain a thin strip (or ribbon) made of the alloy. This thin strip is pulverized to obtain a powder (for example, with a maximum particle size of 250 μm or less). The obtained powder is subjected to heat treatment under an argon atmosphere at a temperature above the crystallization temperature (for example, at 650 to 850 °C for 1 to 120 minutes).

[0027] Next, the heat-treated powder is subjected to nitriding. Nitriding can be carried out by heat-treating the heat-treated powder under a nitrogen atmosphere (for example, at 350-600°C for 120-960 minutes). However, nitriding can also be carried out under any suitable conditions using, for example, ammonia gas, a mixture of ammonia and hydrogen, a mixture of nitrogen and hydrogen, or other nitrogen raw materials. The rare earth magnet material of the present invention is obtained as the powder after nitriding.

[0028] The rare-earth magnet material obtained in this way may have a fine crystalline structure. The average size of the crystal grains may be, for example, 10 nm to 1 μm, preferably 10 to 200 nm, but the present invention is not limited to this embodiment.

[0029] Although a rare-earth magnet material and magnet in one embodiment of the present invention have been described in detail above, the present invention is not limited to this embodiment. [Examples]

[0030] The following describes embodiments of the present invention. However, the present invention is not limited to these embodiments.

[0031] (Preparation of examples and comparative examples) The raw metals were mixed in proportions corresponding to the alloy composition shown in Table 1, and the master alloy was prepared by melting them in a high-frequency induction heating furnace. This master alloy was melted under an argon atmosphere and sprayed onto a Mo roll rotating at a peripheral speed of 70 m / s, thereby ultra-rapidly cooling to obtain a thin strip. This thin strip was pulverized to obtain a powder with a maximum particle size of 32 μm or less (sieved using a sieve with a mesh size of 32 μm).

[0032] The obtained powder was heat-treated in an argon atmosphere at 665-755°C for 10 minutes. Next, the heat-treated powder was nitrided in a nitrogen atmosphere at 405-535°C for 8 hours. The resulting powder yielded samples of rare-earth magnet materials corresponding to the examples and comparative examples.

[0033] Examples 1-16 and Comparative Examples 2-5 contain the carbon necessary for the formation of the MC phase, but Comparative Example 1 does not contain the carbon necessary for the formation of the MC phase. Examples 1-4 involve varying the Zr content while keeping the content of other elements the same. Examples 5 and 6 are based on the composition of Example 2, but with an increased or decreased Sm content. Examples 7, 8, and 9 contain Nb, Ti, or Cr as the element M that generates the MC phase. Examples 10 and 11 are based on the composition of Example 3 with the addition of Co. Examples 12 and 13 are based on the composition of Example 3 with the addition of Al. Examples 14 and 15 are based on the composition of Example 3 with the addition of Si. Example 16 is based on the composition of Example 4, but with an increased nitrogen content. Comparative Example 1 does not contain the amount of C necessary to produce the MC phase based on the composition of Example 3. Comparative Examples 2 and 3 are based on the composition of Example 2, but with variations in Sm content. Comparative Examples 4 and 5 are based on the composition of Example 2, but with variations in Zr content. Comparative Example 6 is based on the composition of Example 11, but with an increased Co content.

[0034] [Table 1]

[0035] (Evaluation of magnetic properties) The magnetic properties of the above examples and comparative examples were evaluated. For the evaluation, the true density of the sample (powder) was set to 7.6 g / cm³, no demagnetization correction was performed, and the coercivity Hcj was measured using a vibrating sample magnetometer (VSM).

[0036] [Table 2]

[0037] Example 1 contains M and C, and also contains the C necessary for the formation of the MC phase, thus exhibiting higher coercivity compared to Comparative Example 1. Examples 2 and 3 are based on the composition of Example 1, but with increased Zr content. Example 2 has the highest coercivity, while Examples 3 and 4, with higher Zr content than Example 2, have lower coercivity than Example 2. Furthermore, Comparative Example 2, with a lower Zr content than Example 1, and Comparative Example 3, with a higher Zr content than Examples 3 and 4, have lower coercivity than Examples 1-4.

[0038] Example 5, which had a higher Sm content than Example 1, showed increased coercivity compared to Example 1, while Example 6, which had a lower Sm content, showed decreased coercivity compared to Example 1. Furthermore, Comparative Example 4, which had a lower Sm content than Example 5, and Comparative Example 5, which had a higher Sm content than Example 6, both showed lower coercivity than Examples 5 and 6. Examples 7 to 9 contained Nb, Ti, or Cr as the element M that forms the MC phase, and all of them showed higher coercivity than Comparative Example 1, which did not form the MC phase.

[0039] Examples 10 and 11 are based on the composition of Example 3 with the addition of Co. When a small amount of Co is added, the coercivity of Example 10 increases, but as in Example 11, when the amount of Co added increases, the coercivity decreases. Examples 12 to 15 are based on the composition of Example 3 with the addition of Al or Si, and all show higher coercivity than Comparative Example 1. Example 16 is based on the composition of Example 4 with an increased N content. Example 16, with an increased N content, shows higher coercivity than Comparative Example 1.

[0040] Samples obtained in the examples and comparative examples were processed with a focused ion beam and examined by energy-dispersive X-ray spectroscopy (TEM-EDX) using a transmission electron microscope. Table 3 shows the presence or absence of the MC phase in each example and comparative example, as determined from the observation results. [Table 3]

[0041] Examples 1-16 and Comparative Examples 2-6 were confirmed to have a crystalline phase mainly composed of Zr and C. Example 7 was confirmed to have precipitated a crystalline phase mainly composed of Nb and C. Example 8 was confirmed to have precipitated a crystalline phase mainly composed of Ti and C. Example 9 was confirmed to have precipitated a crystalline phase mainly composed of Cr and C. No such crystalline phases were observed in Comparative Example 1.

[0042] As representative examples, for Example 2 and Comparative Example 1, the obtained powders were processed with a focused ion beam, and as shown in Figure 1, observation images using a transmission electron microscope (TEM) and elemental mapping images using energy-dispersive X-ray analysis (EDX) were obtained.

[0043] As shown in Figure 1, comparing the EDX mapping images of Example 2 and Comparative Example 1, Comparative Example 1 shows scattered phases with high Zr concentration (white areas). On the other hand, in Example 2, the positions of the phases with high Zr concentration and the phases with high C concentration (white areas) coincide, indicating that compounds mainly composed of Zr and C have precipitated. In other words, in Example 1, compounds mainly composed of Zr and C with a low Fe concentration have precipitated. This suppresses the precipitation of soft magnetic phases mainly composed of Zr and Fe, as seen in Comparative Example 1. Furthermore, in Example 2, since Zr and C form compounds, no Sm-Fe-C compound precipitation is observed. This suggests that Example 2 achieves high coercivity.

Claims

1. The content of M (at least one element selected from Zr, Ti, Hf, V, Nb, Ta, Cr, Mo, W) is 1.6 atomic percent or more and 5.0 atomic percent or less. The Sm content is 7.0 atomic% or more and 11.0 atomic% or less. The N content is between 11.0 atomic percent and 19.5 atomic percent. Fe content is between 69.5 atomic percent and 79 atomic percent. It includes C, A rare earth magnet material containing a crystalline phase (M-C phase) mainly composed of M and C.

2. The rare earth magnet material according to claim 1, further containing Co, wherein the Co content is 5.0 atomic percent or less.

3. Binder and A magnet comprising the rare earth magnetic material according to claim 1 or 2, dispersed within the binder.

Images