Magnetic Materials and Their Manufacturing Methods

Abstract

The present invention relates to a magnetic material and a method for manufacturing the same. The magnetic material of the present disclosure includes a main phase having a crystal structure of R2T 14 B type (R is a rare earth element, and T is a transition metal element). The main phase has a composition represented by ((Nd, Pr) (1‑x‑y) La x R 1 y ))2((Fe (1‑z‑w) (Co, Ni) z M w )) 14 B (where R 1 is a rare earth element other than Nd, Pr, and La, M is an element other than Fe, Co, Ni, and rare earth elements, etc., 0.25 ≦ x ≦ 1.00, 0 ≦ y ≦ 0.10, 0.15 ≦ z ≦ 0.40, and 0 ≦ w ≦ 0.1). The method for manufacturing the magnetic material of the present disclosure includes melting and solidifying raw materials containing the elements constituting the main phase.

Description

Technical Field

[0001] The present disclosure relates to magnetic materials and methods for manufacturing the same. The present disclosure particularly relates to magnetic materials of the R-Fe-B series (where R is a rare earth element). Background Art

[0002] The magnetic material of the R-Fe-B series has a main phase having a crystal structure of the R2T 14 B type (where T is a transition metal element). Through this main phase, high remanent magnetization is obtained.

[0003] Among the magnetic materials of the R-Fe-B series, the Nd-Fe-B series magnetic material (neodymium magnetic material) that selects Nd as R has an excellent balance between performance and price and is the most common magnetic material. Therefore, the Nd-Fe-B series magnetic material has been rapidly popularized, and it is expected that the usage amount of Nd will also increase sharply in the future, and the future usage amount of Nd may exceed the reserves. Therefore, attempts have been made to replace part or all of Nd with light rare earth elements such as Ce, La, Y, and Sc.

[0004] For example, Japanese Patent Application Laid-Open No. 2020-107849 discloses a magnetic material obtained by using an Nd-Fe-B series magnetic material in which part of Nd is replaced with La and / or Ce as a precursor and allowing a modification material containing a rare earth element other than the light rare earth element to diffusely penetrate into the interior of the precursor. It should be noted that in this specification, unless otherwise specified, "and / or" means "at least one".

[0005] In addition, for example, Japanese Patent Application Laid-Open No. 2020-31144 discloses an Nd-Fe-B series magnetic material in which part of Nd is replaced with La and / or Ce and optionally part of Fe is replaced with a small amount of Co.

[0006] Moreover, for example, Japanese Patent Application Laid-Open No. 61-159708 discloses an R-Fe-B series magnetic material in which part or all of Nd is replaced with La and / or Ce. Summary of the Invention

[0007] Compared with other magnetic materials, the Nd-Fe-B series magnetic material can obtain high saturation magnetization, and thus is often used in high-output motors and the like. The magnetic material used in high-output motors and the like is often exposed to high temperatures due to the heat generated by the motors and the like.

[0008] The magnetic properties of the magnetic material decrease as the temperature rises and disappear at the Curie temperature. It is known that compared with other magnetic materials, the decrease in magnetic properties caused by temperature rise in the Nd-Fe-B series magnetic material is sharp.

[0009] When a part or all of Nd is simply replaced with light rare earth elements in order to reduce the amount of Nd used, the magnetic properties at high temperatures, particularly the reduction in coercivity at high temperatures, are significant. The magnetic materials disclosed in JP-A-2020-107849, JP-A-2020-31144, and JP-A-61-159708 optimize the types of light rare earth elements and their replacement ratios to improve the coercivity at high temperatures.

[0010] On the other hand, the Nd-Fe-B-based magnetic material has a relatively high saturation magnetization at high temperatures. Therefore, even if the saturation magnetization at high temperatures decreases due to replacing a part or all of Nd with light rare earth elements, it rarely becomes a problem in practical use. However, in recent years, the high output and miniaturization of motors and the like have been rapidly developing, and the decrease in saturation magnetization at high temperatures cannot be ignored. Therefore, the present inventors have found the following problem: It is desired to suppress the decrease in saturation magnetization at high temperatures within a range where there is no problem in practical use, or to further increase the saturation magnetization at high temperatures, even when a part or all of Nd is replaced with light rare earth elements.

[0011] The magnetic material and its manufacturing method of the present disclosure have been completed to solve the above problems. The object of the present disclosure is to provide an R-Fe-B-based magnetic material and its manufacturing method that suppress the decrease in saturation magnetization at high temperatures within a range where there is no problem in practical use, or further increase the saturation magnetization at high temperatures, even when the amount of Nd used is reduced. It should be noted that in this specification, unless otherwise specified, the so-called "high temperature" means 373 to 473 K.

[0012] The present inventors have repeatedly conducted in-depth research to achieve the above object and have completed the magnetic material and its manufacturing method of the present disclosure. The magnetic material and its manufacturing method of the present disclosure include the following aspects.

[0013] 〈1〉 A magnetic material having a main phase with a crystal structure of R2T 14 B type, where R is a rare earth element, T is a transition metal element, and the main phase has a composition represented by the molar ratio formula ((Nd, Pr) (1-x-y) La x R 1 y ))2((Fe (1-z-w) (Co, Ni) z M w )) 14 B, where R 1 is one or more rare earth elements other than Nd, Pr, and La, M is one or more elements other than Fe, Co, Ni, and rare earth elements and inevitable impurity elements, 0.25 ≦ x ≦ 1.00, 0 ≦ y ≦ 0.10, 0.15 ≦ z ≦ 0.40, and 0 ≦ w ≦ 0.1.

[0014] 〈2〉The magnetic material according to item 〈1〉, wherein x satisfies 0.25 ≤ x ≤ 0.61.

[0015] 〈3〉The magnetic material according to item 〈1〉 or 〈2〉, wherein the volume fraction of the main phase is 80.0 to 100%.

[0016] 〈4〉The magnetic material according to any one of items 〈1〉 to 〈3〉, wherein the lattice volume of the main phase is 0.930 to 0.955 nm 3 。

[0017] 〈5〉The magnetic material according to any one of items 〈1〉 to 〈4〉, wherein the density of the main phase is 7.00 to 7.90 g / cm 3 。

[0018] 〈6〉A method for manufacturing a magnetic material, which is the method for manufacturing the magnetic material according to item 〈1〉, and includes: melting and solidifying a raw material containing elements constituting the main phase.

[0019] 〈7〉The method according to item 〈6〉, wherein an ingot obtained by melting and solidifying the raw material is heat-treated at 1273 to 1573 K for 6 to 72 hours.

[0020] According to the present disclosure, it is possible to provide an R-Fe-B-based magnetic material in which even when the amount of Nd used is reduced, by selecting La as the light rare earth element and replacing a part of Fe with Co and / or Ni in a specified molar ratio range, the decrease in saturation magnetization at high temperature is suppressed to a range where there is no practical problem, or the saturation magnetization at high temperature is further increased.

[0021] In addition, according to the present disclosure, it is possible to provide a method for manufacturing an R-Fe-B-based magnetic material in which even when the amount of Nd used is reduced, by selecting La as the light rare earth element and replacing a part of Fe with Co and / or Ni in a specified molar ratio range, the decrease in saturation magnetization at high temperature is suppressed to a range where there is no practical problem, or the saturation magnetization at high temperature is further increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The features, advantages, and technical and industrial significance of the exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and wherein:

[0023] Figure 1 A coordinate diagram showing the relationship between the reduction ratio of the amount of Nd and Pr used and the saturation magnetization Ms at high temperature (453 K).

[0024] Figure 2A coordinate diagram showing the relationship between temperature and saturation magnetization Ms for Example 4, Example 5, and Comparative Example 2. Detailed Description of the Invention

[0025] Embodiments of the magnetic material and its manufacturing method of the present disclosure will be described in detail below. Additionally, the embodiments shown below do not limit the magnetic material and its manufacturing method of the present disclosure.

[0026] Without being bound by theory, the reasons for being able to suppress the decrease in saturation magnetization at high temperatures within a practically acceptable range or further increase the saturation magnetization at high temperatures even when reducing the amount of Nd used will be described below.

[0027] The R-Fe-B based magnetic material includes a main phase having a crystal structure of R2T 14 type B. R is a rare earth element, and T is a transition metal element. In the main phase having a crystal structure of R2T 14 type B, the most representative composition of the main phase is represented by Nd2Fe 14 B. Hereinafter, the phase having such a composition may sometimes be referred to as the "Nd2Fe 14 B phase".

[0028] In order to reduce the amount of Nd used, conventionally, a part of Nd in the Nd2Fe 14 B phase has been replaced with a light rare earth element. On the other hand, it is known that a phase in which all of R in the R2Fe 14 B phase is La, that is, the La2Fe 14 B phase, is very unstable. Therefore, as an element for reducing the amount of Nd used, La has been conventionally avoided as much as possible. Even when La is selected, a light rare earth element other than La, especially Ce, is also selected, and the content ratio (replacement ratio) of La is reduced as much as possible.

[0029] However, the present inventors have found that even when a part of Nd is replaced with La in a specified molar ratio or more, by replacing a part of Fe with Co and / or Ni in a specified molar ratio range, a phase having a crystal structure of R2T 14 type B can be stabilized. Moreover, the present inventors have found that thereby, the decrease in saturation magnetization at high temperatures can be suppressed within a practically acceptable range, or the saturation magnetization at high temperatures can be further increased.

[0030] Furthermore, without being bound by theory, the present inventors have found the reasons for being able to suppress the decrease in saturation magnetization at high temperatures within a practically acceptable range or further increase the saturation magnetization at high temperatures by the above-described arrangement as follows.

[0031] In magnetic materials in which part of Nd is replaced with Ce in order to reduce the amount of Nd used, the magnetic properties at high temperatures, especially the saturation magnetization, have not been improved in many cases even if part of Fe is replaced with Co. The reason for this is believed to be that when part of Fe is replaced with Co, even if the Curie temperature rises, the magnetic properties, especially the saturation magnetization, in the high temperature region until the Curie temperature is reached may not be improved.

[0032] As described above, in order to reduce the amount of Nd used, when part of Nd is replaced with a light rare earth element, the La2Fe 14 The instability of the B phase is avoided as much as possible by replacing it with La. However, the inventors dare to choose La as the 14 The R of the phase (main phase) of the B-type crystal structure is obtained by replacing part of Fe with Co within a specified range, thereby obtaining a phase having R2T 14 The phase (main phase) of the B-type crystal structure is stable.

[0033] Considered to have R2T 14 The stabilization of the phase (main phase) of the B-type crystal structure can be explained by the ionic radius of each constituent element which has a great influence on the crystal structure. Table 1 shows the ionic radius of Nd, Ce, La, Pr, Fe, Co and Ni.

[0034]

Table 1

[0035] (×10 -1 nm)

[0036] Nd Ce La Pr Fe Co Ni 1.123 1.01 1.172 1.13 0.785 0.75 0.74

[0037] As can be understood from Table 1, the ionic radius of La is larger than that of Nd. Therefore, when a part of Nd is replaced by La, the R2T 14 In particular, if all Nd is replaced by La, the stability of the phase (main phase) with R2T 14 The stability of the phase (main phase) with a B-type crystal structure is greatly impaired. 14 B phase (consisting essentially of La, Fe, and B, with R2T 14 The phase (main phase) of the B-type crystal structure is unstable.

[0038] However, even if part or all of Nd is replaced by La, if part of Fe is replaced by Co, it is possible to obtain a material having R2T 14Stabilization of the phase (main phase) with a B-type crystal structure. It is considered that this is because the ionic radius of Co is smaller than that of Fe. Therefore, by replacing a part of Fe with Co, the crystal structure expanded due to replacing a part or all of Nd with La can be appropriately reduced.

[0039] Moreover, even if a part or all of Nd is replaced with La, as long as the phase (main phase) with a B-type crystal structure of R2T 14 is stable, the saturation magnetization at high temperature of this phase (main phase) is not inferior to or even superior to that of the Nd2Fe 14 B phase. Specifically, compared with the saturation magnetization at high temperature of the Nd2Fe 14 B phase, the saturation magnetization at high temperature of the La2(Fe, Co) 14 B phase is not inferior. In addition, compared with the saturation magnetization at high temperature of the Nd2Fe 14 B phase, the saturation magnetization at high temperature of the (Nd, La)2(Fe, Co) 14 B phase is even higher. It should be noted that the "Nd2Fe 14 B phase" refers to a phase that is composed basically only of Nd, Fe, and B and has an R2T 14 B-type crystal structure. The "La2(Fe, Co) 14 B phase" refers to a phase in which basically all of Nd is replaced with La and a part of Fe is replaced with Co. The "(Nd, La)2(Fe, Co) 14 B phase" refers to a phase in which a part of Nd is replaced with La and a part of Fe is replaced with Co. "Not inferior" means that compared with the saturation magnetization at high temperature of the Nd2Fe 14 B phase, the decrease in the saturation magnetization at high temperature is within a range that is not problematic in practice.

[0040] As described above, for the conventional magnetic materials in which a part of Nd is replaced with Ce and a part of Fe is replaced with Co, the saturation magnetization at high temperature is not necessarily improved (including the case of "not inferior"). Thus, it is considered that for the magnetic material of the present disclosure in which a part or all of Nd is replaced with La and a part of Fe is replaced with Co, it is not the increase in the Curie temperature caused by Co that improves the saturation magnetization at high temperature. On the contrary, it is the physical properties of La that improve the saturation magnetization at high temperature (including the case of "not inferior"). That is, in the magnetic material of the present disclosure, it is considered that it is not because the Curie temperature rises by replacing a part of Fe with Co, so that the saturation magnetization at high temperature is improved, but because of the physical properties of La, the saturation magnetization at high temperature is improved. Moreover, it is considered that Co in the magnetic material of the present disclosure contributes to the La2(Fe, Co) 14 B phase and / or (Nd, La)2(Fe, Co)14 Stabilization of the B-phase.

[0041] It is known that Pr has physical properties similar to those of Nd. In addition, as can be understood from Table 1, the ionic radius of Nd is close to that of Pr. Therefore, in the magnetic material of the present disclosure, Nd and Pr can be treated as equivalent elements.

[0042] It is known that Fe, Co, and Ni have similar physical properties as iron group elements. Moreover, among these iron group elements, regarding Co and Ni, as can be understood from Table 1, the ionic radius of Co is close to that of Ni. Therefore, in the magnetic material of the present disclosure, Co and Ni can be treated as equivalent elements.

[0043] Based on these understandings, the technical features of the magnetic material of the present disclosure and its manufacturing method will be described below.

[0044] "Magnetic Material"

[0045] The magnetic material of the present disclosure having a main phase with a crystal structure of R2T 14 B-type exhibits magnetism through the main phase. The main phase will be described below.

[0046] 〈Crystal Structure of the Main Phase〉

[0047] The main phase has a crystal structure of R2T 14 B-type. R is a rare earth element, and T is a transition metal element. The crystal structure of the main phase can be identified by, for example, performing X-ray diffraction analysis on the magnetic material of the present disclosure.

[0048] It should be noted that in this specification, the rare earth elements include 17 elements: Sc (scandium), Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium).

[0049] 〈Composition of the Main Phase〉

[0050] The main phase has a composition represented by the molar ratio formula ((Nd, Pr) (1-x-y) La x R 1 y ))2((Fe (1-z-w) (Co, Ni) z M w )) 14 B. Nd is neodymium, Pr is praseodymium, La is lanthanum, Fe is iron, Co is cobalt, and Ni is nickel. R 1is one or more rare earth elements other than Nd, Pr, and La, and M is one or more elements other than Fe, Co, Ni, and rare earth elements, as well as inevitable impurity elements. In addition, in the above formula, for the sake of convenience of explanation, (Nd, Pr) is sometimes (1-x-y) La x R 1 y referred to as the rare earth site, and (Fe (1-z-w) (Co, Ni) z M w is referred to as the iron group site.

[0051] As can be understood from the above formula, the main phase contains one or more elements in 2 moles of the rare earth site, one or more elements in 14 moles of the iron group site, and 1 mole of boron (B). That is, a phase having the above crystal structure is formed by one or more elements in the rare earth site, one or more elements in the iron group site, and boron.

[0052] The rare earth site is composed of Nd, Pr, La, and R 1 and the sum of Nd and Pr, La, and R 1 are present in a ratio of (1 - x - y) : x : y in terms of molar ratio. (1 - x - y) + x + y = 1, so it means that a part of Nd and / or Pr is replaced by one or more elements selected from La and R 1 among them.

[0053] The iron group site is composed of Fe, Co, Ni, and M, and the sum of Fe, Co, and Ni, as well as M, are present in a ratio of (1 - z - w) : z : w in terms of molar ratio. (1 - z - w) + z + w = 1, so it means that a part of Fe is replaced by one or more elements selected from Co, Ni, and M.

[0054] The following explains each element constituting the above formula and its content ratio (molar ratio).

[0055] 〈Nd〉

[0056] Nd is a main element that forms the above crystal structure together with Fe and B. A part of Nd is replaced by one or more elements selected from La and R 1 among them. In addition, as described above, Nd can be treated as an element equivalent to Pr. The following explains Pr, La, Ce, and R 1 in turn.

[0057] 〈Pr〉

[0058] As described above, Pr and Nd have similar physical properties, and the ionic radius of Pr is close to that of Nd. Therefore, Pr can be processed equally with Nd. Thus, the magnetic material of the present disclosure can be applied to Di (praseodymium-neodymium, didymium).

[0059] 〈La〉

[0060] By substituting a part of Nd and / or Pr with La, it helps to increase the saturation magnetization at high temperatures. In addition, even when all of Nd and / or Pr are substituted with La, by substituting a part of Fe with Co and / or Ni, a saturation magnetization at high temperatures comparable to that of the Nd2Fe 14 B phase can be obtained.

[0061] 〈R 1 〉

[0062] R 1 is one or more rare earth elements other than Nd, Pr, and La. R 1 is one or more elements that can be contained within a range that does not impair the magnetic properties of the magnetic material of the present disclosure. R 1 Typically, it is one or more rare earth elements other than Nd, Pr, and La that are difficult to completely separate from each other when refining the respective raw materials containing Nd, Pr, and La, and remain in small amounts in the raw materials and the like.

[0063] 〈Fe〉

[0064] Fe is a main element that forms the above crystal structure together with Nd and B. A part of Fe can be substituted with one or more elements selected from Co, Ni, and M. Co, Ni, and M will be described below.

[0065] 〈Co〉

[0066] Substituting Co for a part of Fe helps to stabilize the main phase. This is because the ionic radius of Co is smaller than that of Fe, so Co can be used to shrink the crystal structure expanded due to substituting a part or all of Nd and / or Pr with La.

[0067] If a part of Fe is substituted with Co, the Curie temperature of the main phase rises, and it is advantageous because the decrease in saturation magnetization at high temperatures (403 - 473 K) can be suppressed.

[0068] 〈Ni〉

[0069] As described above, Ni is an iron group element, and the ionic radius of Ni is close to that of Co. Therefore, Ni can be processed equally with Co. That is, substituting Ni for a part of Fe helps to stabilize the main phase.

[0070] As described above, from the viewpoint of stabilizing the main phase, Ni can be treated equally with Co. However, compared with Fe and Co, Ni contributes less to the manifestation of magnetization. In addition, Ni also contributes less to increasing the Curie temperature as Co does. Therefore, when it is desired to improve the magnetic properties as much as possible, particularly the saturation magnetization, or when it is desired to increase the Curie temperature, it is preferable to reduce the content ratio (molar ratio) of Ni.

[0071] 〈M〉

[0072] M is one or more elements other than Fe, Co, Ni, and rare earth elements, and inevitable impurity elements. M is one or more elements and inevitable impurity elements that are allowed to be contained within a range that does not impair the magnetic properties of the magnetic material of the present disclosure. The so-called inevitable impurity elements refer to impurity elements that are inevitably contained during the manufacture of the magnetic material of the present disclosure or the like, or impurity elements that cause a significant increase in manufacturing cost in order to avoid their inclusion.

[0073] Examples of M other than inevitable impurity elements include one or more elements selected from Ti (titanium), Cr (chromium), Mn (manganese), V (vanadium), Mo (molybdenum), W (tungsten), and C (carbon). These elements, for example, form nucleating substances during the formation of the main phase, contributing to the promotion of the refinement of the main phase and / or the suppression of the grain growth of the main phase.

[0074] Examples of M other than inevitable impurity elements include one or more elements selected from Ga (gallium), Cu (copper), and Al (aluminum). These elements lower the melting point of the R-rich phase described later. Thereby, liquid-phase sintering can be applied when sintering the powder, and when hot-working the sintered body, it is possible to easily melt the R-rich phase and promote the anisotropic growth of the main phase.

[0075] The magnetic material of the present disclosure can obtain the desired saturation magnetization at high temperatures by containing the elements described so far in the following molar ratios. In this regard, the x, y, z, and w of the formula ((Nd, Pr) (1-x-y) La x R 1 y ))2((Fe (1-z-w) (Co, Ni) z M w )) 14 for expressing the composition of the main phase will be described.

[0076] 〈x〉

[0077] In the above formula expressing the composition of the main phase, the value of x represents the substitution ratio (molar ratio) of a part of Nd and / or Pr with La. x satisfies the following values.

[0078] If the value of x is 0.25 or more, the desired saturation magnetization can be obtained at high temperatures. From this viewpoint, the value of x can be 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, or 0.50 or more. On the other hand, even if the value of x is 1, if a part of Fe is replaced with Co and / or Ni so that the replacement ratio is within the range described later, the main phase can also be stabilized. From the viewpoint of stabilizing the main phase, the value of x can be 0.95 or less, 0.90 or less, 0.85 or less, 0.80 or less, 0.75 or less, 0.70 or less, 0.65 or less, 0.61 or less, 0.60 or less, 0.55 or less, or 0.52 or less.

[0079] 〈y〉

[0080] In the above formula representing the composition of the main phase, y represents the ratio (molar ratio) of replacing a part of Nd and / or Pr with R 1 The value of y satisfies the following values.

[0081] As described above, R 1 is one or more rare earth elements that can be contained within the range that does not impair the magnetic properties of the magnetic material of the present disclosure. Thus, y can be 0.10 or less, 0.08 or less, 0.06 or less, 0.04 or less, or 0.02 or less. On the other hand, the magnetic material of the present disclosure may contain no R 1 at all, that is, y can be 0, but it is difficult to make the raw materials contain no R 1 at all when manufacturing the magnetic material of the present disclosure. From this viewpoint, y can be 0.01 or more.

[0082] 〈z〉

[0083] In the above formula representing the composition of the main phase, the value of z represents the ratio (molar ratio) of replacing a part of Fe with Co and / or Ni. The value of z satisfies the following values.

[0084] As described above, by replacing a part of Fe with Co and / or Ni, the crystal structure expanded due to replacing a part or all of Nd and / or Pr with La can be reduced. If the value of z is 0.15 or more, the expanded crystal structure can be reduced and the main phase maintains the R2T 14 type crystal structure. From this viewpoint, the value of z can be 0.18 or more, 0.20 or more, or 0.22 or more.

[0085] On the other hand, compared with Fe, the contributions of Co and / or Ni to magnetic properties, particularly saturation magnetization at room temperature, are small. If the value of z is 0.40 or less, saturation magnetization at room temperature is not impaired practically, and saturation magnetization at high temperatures can be increased. From this viewpoint, the value of z can be 0.38 or less, 0.36 or less, 0.34 or less, 0.32 or less, 0.31 or less, 0.30 or less, 0.28 or less, 0.26 or less, 0.24 or less, 0.22 or less, 0.21 or less, or 0.20 or less.

[0086] 〈w〉

[0087] In the above formula representing the composition of the main phase, w represents the ratio (molar ratio) of replacing a part of Fe with M. As described above, M is one or more elements and inevitable impurity elements that can be contained within a range that does not impair the magnetic properties of the magnetic material of the present disclosure. Thus, w can be 0.10 or less, 0.08 or less, 0.06 or less, 0.04 or less, or 0.02 or less. On the other hand, the magnetic material of the present disclosure may contain no M at all, that is, w can be 0, but it is difficult to completely exclude inevitable impurity elements in M. From this viewpoint, w can be 0.01 or more.

[0088] As described above, Nd and Pr can be treated equally, and Co and Ni can be treated equally. Thus, in the formula ((Nd, Pr) (1-x-y) La x R 1 y ))2((Fe (1-z-w) (Co, Ni) z M w )) 14 B representing the molar ratio of the composition of the main phase, the notations “(Nd, Pr)” and “(Co, Ni)” do not limit the molar ratio of Nd and Pr and the molar ratio of Co and Ni, but can be limited as described below.

[0089] 〈Molar ratio of Nd and Pr〉

[0090] The following relationship can be satisfied for the molar ratio of Nd and Pr. The part “(Nd, Pr)” in the formula representing the molar ratio of the composition of the main phase is replaced with the molar ratio formula “(Nd (1-p) Pr p )” for explanation.

[0091] As described above, the physical properties of Nd and Pr are similar. From this perspective, p can be 0 or more, 0.01 or more, 0.03 or more, 0.05 or more, 0.07 or more, 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.50 or more, and can be 1 or less, 0.99 or less, 0.97 or less, 0.95 or less, 0.90 or less, 0.80 or less, 0.70 or less, or 0.60 or less.

[0092] That p is 0 means that all of them are Nd among Nd and Pr. However, in the raw materials of the magnetic materials of the present disclosure, since it is often difficult to completely separate Nd and Pr, basically, p is 0.01 or more. In addition, that p is 1 means that all of them are Pr among Nd and Pr. However, due to the above problems of the raw materials, basically, p is 0.99 or less.

[0093] Compared with the Pr2Fe 14 B phase, the magnetic properties of the Nd2Fe 14 B phase are slightly more excellent. Thus, when the magnetic properties of the entire magnetic material are particularly improved, p can be 0 or more, 0.01 or more, 0.03 or more, 0.05 or more, 0.07 or more, 0.1 or more, or 0.2 or more, and can be 0.5 or less, 0.4 or less, or 0.3 or less.

[0094] 〈Mole ratio of Co and Ni〉

[0095] Regarding the mole ratio of Co and Ni, the following relationship can be satisfied, and the part of “(Co, Ni)” in the formula representing the mole ratio of the main phase is replaced with the mole ratio formula “(Co (1-q) Ni q )” for explanation.

[0096] As described above, the physical properties of Co and Ni are similar. From this perspective, q can be 0 or more, 0.01 or more, 0.03 or more, 0.05 or more, 0.07 or more, 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.50 or more, and can be 1 or less, 0.99 or less, 0.97 or less, 0.95 or less, 0.90 or less, 0.80 or less, 0.70 or less, or 0.60 or less.

[0097] That q is 0 means that all of them are Co among Co and Ni. However, in the raw materials of the magnetic materials of the present disclosure, since it is often difficult to completely separate Co and Ni, basically, q is 0.01 or more. In addition, that q is 1 means that all of them are Ni among Co and Ni. However, due to the above problems of the raw materials, basically, q is 0.99 or less.

[0098] Co increases the Curie temperature, but the contribution of Ni thereto is small. In addition, the contribution of Co to the saturation magnetization is slightly larger than that of Ni. Therefore, when increasing the Curie temperature or particularly increasing the saturation magnetization of the entire magnetic material, q can be 0 or more, 0.01 or more, 0.03 or more, 0.05 or more, 0.07 or more, 0.1 or more, or 0.2 or more, and can be 0.5 or less, 0.4 or less, or 0.3 or less.

[0099] 〈Volume fraction of the main phase〉

[0100] The magnetic material of the present disclosure includes a main phase having an R2T 14 B-type crystal structure, and the main phase has the above composition. In the main phase of the magnetic material of the present disclosure, part or all of Nd and / or Pr must be replaced with La, and part of Fe must be replaced with Co and / or Ni. Therefore, the process of forming the main phase having an R2T 14 B-type crystal structure is based on the formation process of the Nd2Fe 14 B phase. Thus, in addition to the main phase, the magnetic material of the present disclosure may include a so-called R-rich phase. By including the R-rich phase, the formation of the α-Fe phase can be minimized when the main phase of the magnetic material of the present disclosure is formed.

[0101] The α-Fe phase is a soft magnetic phase. When the α-Fe phase exists in the magnetic material, the apparent saturation magnetization increases, but the coercivity decreases. Therefore, in the magnetic material of the present disclosure, it is preferable to minimize the proportion (volume fraction) of the α-Fe phase. Furthermore, the so-called R-rich phase is a phase having a higher molar ratio of rare earth elements than the main phase, and typically, it is a non-magnetic phase. The R-rich phase magnetically divides (separates) the main phases from each other, which helps to ensure the coercivity. As the R-rich phase, for example, an equivalent in which part or all of Nd of the Nd-rich phase of the Nd-Fe-B-based magnetic material having the Nd2Fe 14 B phase is replaced with one or more elements selected from Pr, La, and R 1 and part of Fe is replaced with one or more elements selected from Co, Ni, and M can be cited.

[0102] The R-rich phase is a phase formed by mixing phases having various compositions with a higher R concentration than the main phase. Therefore, it is difficult to represent the R-rich phase by a composition formula (formula of molar ratio). Therefore, it is generally called the "R-rich phase".

[0103] The magnetic material of the present disclosure includes a main phase having the above composition, may include a small amount of the R-rich phase, and may also include an extremely small amount of the α-Fe phase. The α-Fe phase also includes a phase in which part of Fe is replaced with one or more elements selected from Co, Ni, and M.

[0104] If the volume fraction of the main phase of the magnetic material of the present disclosure is 80.0% or more, the decrease in saturation magnetization caused by the R-rich phase can be suppressed within a range that is not problematic in practical applications, and the decrease in coercivity caused by the α-Fe phase can be suppressed within a range that is not problematic in practical applications. From this perspective, the volume fraction of the main phase can be 82.0% or more, 84.0% or more, 86.0% or more, 88.0% or more, 90.0% or more, 92.0% or more, 94.0%, or 95.0% or more. On the other hand, the volume fraction of the main phase can be 100%, but it is preferable to suppress the formation of the α-Fe phase by forming the R-rich phase, and by having the R-rich phase present around the main phase to magnetically separate the main phases from each other, thereby ensuring the coercivity. From this perspective, the volume fraction of the main phase can be 99.5% or less, 99.0% or less, 98.5% or less, 98.0% or less, 97.5% or less, 97.0% or less, 96.5% or less, 96.0% or less, 95.9% or less, or 95.5% or less.

[0105] Regarding the volume fraction of the main phase, the overall composition of the magnetic material is measured using high-frequency inductively coupled plasma optical emission spectrometry (ICP-AES: Inductively Coupled Plasma Atomic Emission Spectroscopy), assuming that the magnetic material is phase-separated into (Nd, Pr, La, R 1 )2(Fe, Co, Ni, M) 14 B phase and the R-rich phase, and the volume fraction of the main phase is calculated from the measured values. It should be noted that (Nd, Pr, La, R 1 )2(Fe, Co, Ni, M) 14 The B phase refers to (Nd, Pr)2Fe 14 B phase, (Nd, Pr)2Fe 14 B phase in which part or all of the Nd and / or Pr are replaced by one or more elements selected from La and R 1 , a phase in which part of the Fe in the (Nd, Pr)2Fe 14 B phase is replaced by one or more elements selected from Co, Ni, and M, and (Nd, Pr)2Fe 14 B phase in which part or all of the Nd and / or Pr are replaced by one or more elements selected from La and R 1 and part of the Fe in the (Nd, Pr)2Fe 14 B phase is replaced by one or more elements selected from Co, Ni, and M.

[0106] 〈Lattice volume of the main phase〉

[0107] It is considered that if the lattice volume of the main phase is the same as that of Nd2Fe 14If the lattice volume of the B phase is approximated, a phase with a crystal structure of R2T 14 type can be stably maintained. Without being bound by theory, it is considered that the reason is that the lattice volume reflects the three-dimensional similarity of the crystal structure. Nd2Fe 14 The lattice volume of the B phase is 0.949 nm 3 . Thus, the lattice volume of the main phase can be 0.930 nm 3 or more, 0.935 nm 3 or more, 0.940 nm 3 or more, or 0.945 nm 3 or more, and can also be 0.955 nm 3 or less, or 0.950 nm 3 or less. When the lattice volume of the main phase is within the above range, the main phase can stably maintain the crystal structure of R2T 14 type.

[0108] The lattice volume of the main phase can be obtained as follows. Perform X-ray diffraction analysis on the R-Fe-B-based magnetic material, and based on the X-ray diffraction pattern, calculate the a-axis length and the c-axis length according to the relationship between the plane indices and the interplanar spacing (d value). When calculating the a-axis length and the c-axis length, since the main phase of the R-Fe-B-based magnetic material of the present disclosure has the above crystal structure, the main phase can be assumed to be tetragonal. Therefore, as the plane indices, the (311) plane, (214) plane, (313) plane, (224) plane, (410) plane, and (411) plane can be used. Then, calculate the lattice volume according to the following formula.

[0109] (Lattice volume) = (a-axis length) 2 ×(c-axis length)

[0110] 〈Density of the main phase〉

[0111] The density of the main phase is usually inversely proportional to the lattice volume of the crystal. Thus, the density of the main phase is preferably close to the density of the Nd2Fe 14 B phase. The density of the Nd2Fe 14 B phase is 7.23 g / cm 3 . Thus, it can be 7.00 g / cm 3 or more, 7.03 g / cm 3 or more, 7.05 g / cm 3 or more, 7.07 g / cm 3 or more, 7.10 g / cm 3 or more, or 7.20 g / cm 3 or more, and can be 7.90 g / cm 3 or less, 7.80 g / cm 3 or less, 7.70 g / cm3 7.60 g / cm or less 3 7.50 g / cm or less 3 7.40 g / cm or less 3 7.35 g / cm or less 3 or 7.30 g / cm or less 3 or less.

[0112] The density of the main phase is obtained, for example, by pulverizing the magnetic material to obtain a powder and measuring the density of the powder using the picnometer method.

[0113] <<Manufacturing Method>>

[0114] Next, the manufacturing method of the magnetic material of the present disclosure (hereinafter sometimes referred to as "the manufacturing method of the present disclosure") will be described.

[0115] The manufacturing method of the present disclosure includes a melting and solidification step, and an optional homogenization heat treatment step. Each step will be described below.

[0116] <<Melting and Solidification Step>>

[0117] In the manufacturing method of the present disclosure, a raw material containing the elements constituting the above main phase is melted (fused) and solidified to obtain an ingot. When obtaining the ingot, it is preferable to form a rich R phase and suppress the formation of the α-(Fe, Co, Ni, M) phase. By suppressing the formation of the α-(Fe, Co, Ni, M) phase, the coercivity of the magnetic material can be ensured. It should be noted that the α-(Fe, Co, Ni, M) phase refers to a phase in which a part of Fe in the α-Fe phase is replaced by one or more elements selected from Co, Ni, and M.

[0118] Due to the rich R phase, the saturation magnetization of the entire magnetic material decreases. However, by forming the rich R phase, the formation of the above-mentioned α-(Fe, Co, Ni, M) phase is suppressed, and the main phases are magnetically separated from each other by the rich R phase, so that the coercivity of the entire magnetic material can be ensured. Therefore, by making the volume fraction of the main phase within the above range, the saturation magnetization of the entire magnetic material can be made within a practically acceptable range.

[0119] In order to make the volume fraction of the main phase within the above range, it is preferable that the total molar ratio of rare earth elements in the composition of the raw material is equal to or higher than the total molar ratio of rare earth elements in the main phase. Thus, the composition of the raw material is preferably ((Nd, Pr) (1-x-y) La x R 1 y )) t ((Fe (1-z-w) (Co, Ni) z Mw )) 14 B (where t is 2.00 to 3.00). At this time, x, y, z, and w can be the same as x, y, z, and w in the formula representing the composition of the above-mentioned main phase. From the viewpoint of suppressing the appearance of the α-(Fe, Co, Ni, M) phase, t is preferably 2.01 or more, 2.02 or more, 2.03 or more, 2.04 or more, 2.05 or more, 2.06 or more, 2.08 or more, 2.10 or more, 2.20 or more, 2.30 or more, 2.40 or more, or 2.50 or more. On the other hand, from the viewpoint of making the volume fraction of the R-rich phase the necessary minimum (minimizing), t is more preferably 2.90 or less, 2.80 or less, 2.70 or less, or 2.60 or less. It should be noted that in the manufacturing process, if there is no loss of specific elements, etc., the overall composition of the magnetic material (the sum of the main phase and the phases other than the main phase) is substantially the same as the composition of the raw material mixture.

[0120] The melting and solidification of the raw materials can be carried out by known methods. As a method for melting the raw materials, for example, the following methods can be cited: loading the raw materials into a container such as a crucible, and performing arc melting or high-frequency melting of the raw materials in the container to obtain a molten metal. As a method for solidifying the molten metal, for example, injecting the molten metal into a mold such as a book-shaped mold or solidifying the molten metal in a crucible, etc. From the viewpoints of suppressing the coarsening of the main phase and homogenizing the main phase, etc., it is preferable to increase the cooling rate of the molten metal. Therefore, it is preferable to inject the molten metal into a mold such as a book-shaped mold. Furthermore, from the viewpoints of further suppressing the coarsening of the main phase and homogenizing the main phase, etc., for example, the following method can be applied. That is, an ingot obtained by high-frequency melting or arc melting and solidifying the raw materials in a container can be remelted by high-frequency melting, etc., and the molten metal is quenched using a strip casting method and a liquid quenching method, etc., to obtain a thin sheet.

[0121] 〈Homogenization heat treatment process〉

[0122] In order to homogenize the main phase in the ingot, the ingot can be heat-treated (hereinafter, such heat treatment is sometimes referred to as "homogenization heat treatment"). The thin sheet obtained by quenching using a strip casting method and a liquid quenching method, etc., can be subjected to homogenization heat treatment.

[0123] The temperature of the homogenization heat treatment can be, for example, 1273 K or more, 1323 K or more, or 1373 K or more, and can be 1573 K or less, 1523 K or less, 1473 K or less, or 1423 K or less. The time of the homogenization heat treatment can be, for example, 6 hours or more, 12 hours or more, 18 hours or more, or 24 hours or more, and can also be 48 hours or less, 42 hours or less, 36 hours or less, or 30 hours or less.

[0124] In order to suppress the oxidation of the ingot, the homogenization heat treatment is preferably carried out in an inert gas atmosphere. For the inert gas atmosphere, a nitrogen atmosphere is included.

[0125] 〈Crushing process〉

[0126] Before or after the homogenization heat treatment, the ingot can be crushed. Typically, the ingot is crushed after the homogenization heat treatment.

[0127] Regarding the crushing of the ingot, known methods can be applied. As the crushing method, for example, methods using a shredder, a ball mill, a jet mill, etc. can be cited. These methods can be combined.

[0128] The crushing of the ingot is preferably carried out in an inert gas atmosphere. Thereby, the oxidation of the ingot and the crushed powder can be suppressed. The inert gas atmosphere includes a nitrogen atmosphere. As the particle size of the crushed powder, represented by D 50 it can be 5 μm or more, 10 μm or more, or 15 μm or more, and can be 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, or 20 μm or less.

[0129] 《Modification》

[0130] The magnetic material and its manufacturing method of the present disclosure are not limited to the embodiments described so far, and can be appropriately modified within the scope described in the patent claims. For example, the magnetic material of the present disclosure can be a powder or a molded body of the powder. The molded body can be a bonded molded body or a sintered molded body. Regarding the bonded molded body, typically, a resin-bonded molded body, etc. can be cited. The sintering method can be appropriately selected, such as pressureless sintering and pressure sintering, according to the particle size of the main phase, etc.

[0131] Hereinafter, the magnetic material and its manufacturing method of the present disclosure will be described more specifically with examples, comparative examples, and conventional examples. Furthermore, the magnetic material and its manufacturing method of the present disclosure are not limited to the conditions used in the following examples, etc.

[0132] 《Preparation of specimens》

[0133] Specimens of the magnetic material were prepared according to the following procedures.

[0134] Metals Nd, Ce-Fe alloy, metal La, metal Pr, metal Fe, metal Co, metal Ni, Fe-B alloy, metal Ga, and metal Cu were blended in such a way that the main phase had the composition shown in Table 2, and the blend was high-frequency melted and solidified to obtain a magnetic material ingot. When blending the raw material powders, the total molar number of Nd, Ce, La, and Pr blended was made larger than the total molar number of Nd, Ce, La, and Pr in the main phase in such a way that the volume fraction of the main phase was 95 to 100%. It should be noted that in this specification, for example, "metal Nd" refers to unalloyed Nd. Of course, inevitable impurities may be contained in metal Nd.

[0135] In an argon atmosphere, the magnetic material ingot was subjected to homogenization heat treatment at 1398 K for 24 hours.

[0136] The magnetic material ingot after homogenization heat treatment was placed in a glove box, and in an argon atmosphere, the magnetic material ingot was crushed using a shredder. The particle size of the crushed magnetic material powder is represented by D 50 and is 20 μm or less.

[0137] "Evaluation"

[0138] For each specimen, the composition, volume fraction, density, and lattice volume of the main phase were determined by the above-described measurement method. In addition, for each specimen, using a physical property measurement system PPMS (registered trademark)-VSM, with a maximum applied magnetic field of 9 T, the magnetic properties were measured. Regarding the measurement of the magnetic properties, the powder of each specimen was magnetically oriented in epoxy resin and cured at the same time. For the magnetic properties of each cured specimen, the measurements were carried out in the easy magnetization axis direction and the hard magnetization axis direction at 300 to 453 K. Based on the measured values in the easy magnetization axis direction, the saturation magnetization Ms was calculated using the saturation approach rule. In addition, based on the measured values in the hard magnetization axis direction, the anisotropy magnetic field Ha was determined using the SPD (Singular Point Detection) method.

[0139] The results are shown in Table 2. In Table 2, "R2T 14 B phase" refers to "a phase having a crystal structure of the R2T 14 B type". In Table 2, as reference values, the saturation magnetization change rate (% / K) per unit temperature is also shown. The saturation magnetization change rate per unit temperature is an evaluation of the ratio of the change in saturation magnetization when the magnetic material is heated from room temperature (300 K) to 453 K per 1 K, and can be calculated by the following formula (1).

[0140] [{(Ms (453K) - Ms (300K) ) / Ms (300K)} / (453 K - 300 K)] × 100 ··· Formula (1)

[0141] wherein, Ms (300K) : saturation magnetization at 300K

[0142] Ms (453K) : saturation magnetization at 453K

[0143] Figure 1 is a coordinate graph showing the relationship between the reduction ratio of the usage amounts of Nd and Pr and the saturation magnetization Ms at high temperature (453K). Figure 2 is a coordinate graph showing the relationship between temperature and saturation magnetization Ms for Example 4, Example 5, and Comparative Example 2. Further, the reduction ratio of the usage amounts of Nd and Pr corresponds to 1 - x - y in the formula representing the composition of the above-mentioned main phase.

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150] It can be understood from Figure 2 that: for the sample of Comparative Example 8 (Nd2Fe 14 B phase), due to the rise in temperature, the saturation magnetization decreases sharply, but for the samples of Example 4 and Example 5 in which part or all of Nd is replaced by La and part of Fe is replaced by Co, the decrease in saturation magnetization caused by the rise in temperature is alleviated. Moreover, in Figure 1 the dotted line connecting Example 4 (the sample in which all of Nd is replaced by La and part of Fe is replaced by Co) and Comparative Example 8 (Nd2Fe 14 B phase) is a line predicting the decrease in saturation magnetization at high temperature as the reduction ratio (La content ratio) of the usage amounts of Nd and Pr increases. The saturation magnetization at high temperature of all the samples of Examples 1 to 8 is above the value shown by the dotted line. Thus, it can be understood that: in all the samples of Examples 1 to 8, the decrease in saturation magnetization at high temperature is suppressed within a range where there is no practical problem, or the saturation magnetization at high temperature is further increased.

[0151] On the other hand, it can be understood from Table 2 and Figure 1 that: the samples of Comparative Examples 1 to 13 did not form a phase having a crystal structure of R2T 14 B type, or even if a phase having a crystal structure of R2T 14In the phase with the crystal structure of type B, the saturation magnetization at high temperatures is not good either. It can be understood that this is because: in the specimens of Comparative Examples 1 to 13, a part of Nd was not replaced with La, or even if it was replaced with La, the replacement rate was not appropriate, or a part of Fe was not replaced with Co, or even if it was replaced, the replacement rate was not appropriate.

[0152] From the above results, the effects of the magnetic material and the method for manufacturing the same according to the present disclosure can be confirmed.

Claims

1. A magnetic material having a main phase with a crystal structure of the R2T 14 B type, where R is a rare earth element and T is a transition metal element, The main phase has a composition represented by the formula (Nd (1-x) La x )2(Fe (1-z-w) Co z M w ) 14 B, where M is one or more elements other than Fe, Co, Ni, and rare earth elements, and inevitable impurity elements, 0.25 ≤ x ≤ 0.61, 0.15 ≤ z ≤ 0.40, and 0 ≤ w ≤ 0.

1.

2. The magnetic material according to claim 1, wherein The volume fraction of the main phase is 80.0 to 100%.

3. The magnetic material according to claim 1, wherein, The lattice volume of the main phase is 0.930 to 0.955 nm 3 .

4. The magnetic material according to claim 1, wherein, The density of the main phase is 7.00 to 7.90 g / cm 3 .

5. The manufacturing method of the magnetic material, which is the manufacturing method of the magnetic material described in claim 1, includes: A raw material containing the elements constituting the main phase is melted and solidified.

6. The method according to claim 5, wherein, The ingot obtained by melting and solidifying the raw material is heat-treated at 1273 to 1573 K for 6 to 72 hours.

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