JP6733871B2 - Magnetic compound and method for producing the same - Google Patents

Description

The present disclosure relates to magnetic compounds and methods of making the same. The present disclosure particularly relates to a magnetic compound having a low α-Fe phase content and a method for producing the same.

Applications of permanent magnets cover a wide range of fields such as electronics, information communication, medical care, machine tools, industrial and automobile motors. In addition, there is an increasing demand for suppression of carbon dioxide emissions, and due to the widespread use of hybrid cars, energy saving in the industrial field, and improvement of power generation efficiency, expectations for the development of permanent magnets with even higher characteristics have increased in recent years. ..

At present, Nd-Fe-B system magnets, which are dominant in the market as high-performance magnets, are also used as drive motor magnets for HV/EHV. In response to the recent pursuit of further downsizing and higher output of motors (increase in remanent magnetization of magnets), development of new permanent magnet materials has been promoted.

As one of the development of materials having performance exceeding that of Nd-Fe-B based magnets, research on rare earth-iron based magnetic compounds having a ThMn ₁₂ type crystal structure is under way.

For example, Patent Document 1, the formula ^{_{(R 1 (1-x)}} R 2 x) a (Fe (1-y) Co y) b T c M d (R 1 is, Sm, Pm, Er, Tm, And at least one element selected from the group consisting of Yb, and R ² is one selected from the group consisting of Zr, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, and Lu. The above elements, T is one or more elements selected from the group consisting of Ti, V, Mo, Si, and W, and M is an unavoidable impurity element and Al, Cr, Cu, Ga, Ag, and Au. One or more elements selected from the group consisting of 0≦x≦0.7, 0≦y≦0.7, 4≦a≦20, b=100-a-c-d, 0<c< 7.7, 0≦d≦3), which is a magnetic compound having a ThMn ₁₂ type crystal structure and an α(Fe, Co) phase volume fraction of less than 12.3%. Compounds are disclosed.

JP, 2017-57471, A

A permanent magnet is required to have high remanence and coercive force. In order to improve the coercive force without lowering the residual magnetization, it is important to reduce the content of the soft magnetic phase in the magnet.

When a rare earth-iron-based magnetic compound having a ThMn ₁₂ type crystal structure is used as a raw material for a permanent magnet, it is important to minimize the α-Fe phase (soft magnetic phase) in the magnetic compound. Is.

In the magnetic compound disclosed in Patent Document 1, it has been desired to further reduce the content of the α-Fe phase. From this, the present inventors have found a problem that it is desired to further reduce the content of the α-Fe phase in a rare earth-iron magnetic compound having a ThMn ₁₂ type crystal structure. ..

The present disclosure has been made to solve the above problems, and an object thereof is to provide a rare earth-iron-based magnetic compound having a ThMn ₁₂ type crystal structure with a small α-Fe phase content, and a method for producing the same. And

The present inventors have conducted extensive studies to achieve the above object, and completed the magnetic compound of the present disclosure and a method for producing the same. The summary is as follows.
<1> formula _{(Sm (1-x-y} ) R y Zr x) a (Fe (1-z) Co z) b T c M d
(In the above formula, R is one or more rare earth elements other than Sm,
T is one or more elements selected from the group consisting of Ti, V, Mo and W,
M is an unavoidable impurity element and one or more elements selected from the group consisting of Al, Si, Ni, C, O, N, Cr, Cu, Ga, Ag and Au, and
0<x≦0.3,
0≦y≦0.1,
0≦z≦0.3,
7.7<a≦9.1,
b=100-a-c-d,
3.8<c≦7.7, and
0≦d≦1.0)
Has a composition represented by
In the above formula, the relationship of a≧1.0x+7.7 and c≧−2.5x+4.7 is satisfied, and
Has a ThMn ₁₂ type crystal structure,
Magnetic compound.
<2> The magnetic compound according to the item <1>, which contains 10 to 100 ppm of N.
<3> The magnetic compound according to item <1> or <2>, wherein 3.1≦c≦6.5 in the above formula.
<4> formula _{(Sm (1-x-y} ) R y Zr x) a (Fe (1-z) Co z) b T c M d
(In the above formula, R is one or more rare earth elements other than Sm,
T is one or more elements selected from the group consisting of Ti, V, Mo and W,
M is an unavoidable impurity element and one or more elements selected from the group consisting of Al, Si, Ni, C, O, N, Cr, Cu, Ga, Ag and Au, and
0<x≦0.3,
0≦y≦0.1,
0≦z≦0.3,
7.7≦a≦9.1,
b=100-a-c-d,
3.8<c≦7.7, and
0≦d≦1.0)
And has a composition represented by
In the above formula, preparing a molten metal satisfying the relationship of a≧1.0x+7.7 and c≧−2.5x+4.7, and
Quenching the molten metal at a rate of 1×10 ² to 1×10 ⁷ K/sec to obtain flakes;
The method for producing a magnetic compound according to the item <1>, comprising:
<5> The method according to <4>, which contains 10 to 100 ppm of N.
<6> The method according to the item <4> or the item <5>, wherein 3.1≦c≦6.5 in the above formula.
<7> The method according to any one of <4> to <6>, further including heat treating the flakes at 800 to 1300° C. for 2 to 120 hours.

According to the present disclosure, it is possible to provide a magnetic compound in which the content of the α-Fe phase is minimized and a method for producing the same by specifying the overall composition of the magnetic compound in consideration of the component composition in the magnetic phase. it can.

FIG. 1 shows the Zr content ratio x and the rare earth site content a and Ti content c for the overall compositions of the magnetic compounds of Examples 1 to 8 and Comparative Examples 1 to 6 based on the analysis results of Table 1. It is a graph that summarizes the relationship. FIG. 2 is a ternary phase diagram of Sm-Fe-Ti. FIG. 3 is a graph showing the stable region of the T component in the R′Fe _12-v T _v compound. FIG. 4 is a schematic view of an apparatus used in the strip casting method. FIG. 5 summarizes the relationship between the Zr content ratio x′, the rare earth site content p and the Ti content q for the compositions of the magnetic phases of Examples 1 to 8 and Comparative Examples 1 to 6 from Table 4. It is a graph.

Hereinafter, embodiments of the magnetic compound and the method for producing the same according to the present disclosure will be described in detail. The embodiments described below do not limit the magnetic compound of the present disclosure and the method for producing the same.

The magnetic compound of the present disclosure has a ThMn ₁₂ type crystal structure. Since the magnetic compound of the present disclosure contains Sm, Fe, and Ti as main elements, the composition in which the ThMn ₁₂ type crystal structure is easily stabilized will be described in the Sm-Fe-Ti ternary system.

2 shows a ternary phase diagram of Sm-Fe-Ti (Source: AC Neiva, et al., Journal of the Less-Common Metals 170, 293 (1991)). As it can be seen from Figure 2, in the ternary system of _{SmFe-Ti, SmFe 12-w} Ti w _{phase, Sm 1 Fe 9-w Ti} w -phase, and _Sm 2 _{Fe 17-w} Ti w phase are present obtain. These phases are represented by "1-12", "1-9", and "2-17" in FIG. 2, respectively. Among these phases, the SmFe _12-w Ti _w phase has a ThMn ₁₂ type crystal structure. Examples of the SmFe _12-w Ti _w phase include the SmFe ₁₁ Ti phase. Hereinafter, the SmFe _12-w Ti _w phase, the SmFe _9-w Ti _w phase, and the Sm ₂ Fe _17-w Ti _w phase are referred to as 1-12 phase, 1-9 phase, and 2-17 phase, respectively. May be expressed.

In these phases, the Sm content ratio (molar ratio) when the Fe and Ti contents are 1 is 0.083 for the 1-12 phase, 1-9 phase, and 2-17 phase, respectively. 0.111 and 0.118. That is, the 1-9 phase and the 2-17 phase have a higher Sm content than the 1-12 phase.

As can be seen from FIG. 2, in the Sm-Fe-Ti ternary system, an α-Fe phase may be present in addition to the 1-12 phase, the 1-9 phase, and the 2-17 phase. When the Sm content is 7.7 atomic %, the 1-12 phase is most easily stabilized, and the α-Fe phase content is likely to decrease. When the content of Sm is less than 7.7 atomic %, the 1-9 phase, the 2-17 phase and the like are unlikely to exist, and the content of the α-Fe phase easily increases. On the other hand, when the content of Sm is more than 7.7 atomic %, the contents of the 1-9 phase, the 2-17 phase and the like tend to increase, and the α-Fe phase content tends to decrease. In addition, "1-9 phase, 2-17 phase, etc." means the general term of the phase with a large content of Sm compared with the 1-12 phase. As such a phase, in addition to the 1-9 phase and the 2-17 phase, for example, a phase in which a part of Sm is missing in the 1-9 phase and the 2-17 phase, and a 1-9 phase Examples of the 2-17 phase include a phase in which a smaller number of Sm atoms have penetrated.

As shown in FIG. 2, the composition region in which the 1-12 phase stably exists is very narrow. From this, when the content of Sm is reduced in the whole magnetic compound, the 1-12 phase is not stable and the content of the α-Fe phase tends to increase. On the other hand, if the content of Sm is increased, the 1-12 phase is not stable and the contents of the 1-9 phase, the 2-17 phase, etc. are likely to increase.

It has been conventionally performed to add Zr to the ternary system of Sm-Fe-Ti in order to stabilize the 1-12 phase. However, with respect to the Zr content, in the past, only studies such that the Zr content ratio (molar ratio) should not be higher than the Sm content ratio (molar ratio) so as not to inhibit the action effect of Sm. I wasn't apprehended. Therefore, for example, the magnetic compound disclosed in Patent Document 1 could not sufficiently reduce the content of the α-Fe phase.

A magnetic phase and a grain boundary phase exist in the magnetic compound. The grain boundary phase is complicated because various phases are mixed. In addition, many magnetic properties of magnetic compounds are derived from the magnetic phase. Therefore, first, the content ratio of Zr in the magnetic phase was investigated.

Without being bound by theory, it is believed that most of Zr in the magnetic compound is replaced with a part of Sm. Therefore, the relationship between the Zr content ratio (molar ratio) x′, where the total content of Sm and Zr in the magnetic phase is 1, and the total content (atomic %) p of Sm and Zr with respect to the entire magnetic phase investigated.

As a result, the present inventors have found the following.

The numerical value x'and p in the magnetic phase have a linear relationship (proportional relationship), and the slope thereof is positive. From this, it can be said that when the Zr ratio x′ in the magnetic phase is increased, the content p of the rare earth site represented by Sm _(1-x−y) R _y Zr _x in the magnetic phase increases.

Further, x′ in the magnetic phase and x in the overall composition are almost equal. From this, when the total content of Sm and Zr in the overall composition is 1, the Zr content ratio (molar ratio) is x, and the total content of Sm and Zr in the overall composition (atomic %) is a. , Investigated the relationship. As a result, as in the case of magnetic phase, increasing the Zr ratio x of the whole composition, the content a of the rare earth site represented by the whole composition of _{Sm (1-x-y)} R y Zr x is It turned out to increase.

Further, regarding the relationship between x and a, it was found that when a<1.0x+7.7, the magnetic phase was not stable and many α-Fe phases were present in the grain boundary phase. This is a phase diagram of the Sm-Fe-Ti ternary system (not containing Zr) shown in FIG. 2, and it means that if the Sm content is low, the α-Fe phase content tends to increase. To do.

On the other hand, when a≧1.0x+7.7, the content of the α-Fe phase existing in the grain boundary phase decreases. It was also found that the grain boundary phase contains a small amount of 1-9 phase and 2-17 phase. This is a phase diagram of the ternary system of Sm-Fe-Ti (not containing Zr) shown in FIG. 2, and when the content of Sm is large, the content of the α-Fe phase is apt to decrease, This corresponds to the presence of the 9th phase and the 2-17th phase.

Up to now, the knowledge when Zr is added to the ternary system of Sm-Fe-Ti in order to stabilize the 1-12 phase has been described. The findings obtained by examining the Ti content in order to further stabilize the 1-12 phase will be described below.

A magnetic phase and a grain boundary phase exist in the magnetic compound. The grain boundary phase is complicated because various phases are mixed. In addition, many magnetic properties of magnetic compounds are derived from the magnetic phase. Therefore, first, the content ratio of Zr in the magnetic phase was investigated.

Therefore, the relationship between the Zr content ratio (molar ratio) x'when the total content of Sm and Zr in the magnetic phase is 1 and the Ti content (atomic %) q with respect to the entire magnetic phase was investigated.

As a result, the present inventors have found the following.

The numerical values x'and q in the magnetic phase have a linear relationship (proportional relationship), and the slope thereof is negative. From this, it can be said that when the Zr ratio x′ in the magnetic phase is increased, the Ti content q in the magnetic phase decreases.

Further, x′ in the magnetic phase and x in the overall composition are almost equal. From this, when the total content of Sm and Zr in the overall composition is 1, the content ratio (molar ratio) of Zr is x, and the content of Ti (atomic %) in the overall composition is c, and the relationship is shown. investigated. As a result, increasing the Zr ratio x of the whole composition, the content c of the rare earth site represented by the whole composition of _{Sm (1-x-y)} R y Zr x was found to be reduced.

Furthermore, regarding the relationship between x and c, it was found that when c<−2.5x+4.7, the magnetic phase was not stable and many α-Fe phases were present in the grain boundary phase. This is a phase diagram of the Sm-Fe-Ti ternary system (not containing Zr) shown in FIG. 2, and it means that if the Sm content is low, the α-Fe phase content tends to increase. To do.

On the other hand, when c≧−2.5x+4.7, the content of the α-Fe phase existing in the grain boundary phase decreases. It was also found that the grain boundary phase contains a small amount of 1-9 phase and 2-17 phase. This is a phase diagram of the ternary system of Sm-Fe-Ti (not containing Zr) shown in FIG. 2, and when the content of Sm is large, the content of the α-Fe phase is apt to decrease, This corresponds to the presence of the 9th phase and the 2-17th phase.

The constituent features of the magnetic compound of the present disclosure and the method for producing the same, which have been completed based on the findings described above, will be described below.

<Magnetic compound>
Magnetic compounds of the present disclosure, having a composition represented by the formula _{(Sm (1-x-y} ) R y Zr x) a (Fe (1-z) Co z) b T c M d. This formula represents the overall composition of the magnetic compound of the present disclosure.

In the above formula, Sm is samarium, R is one or more rare earth elements other than Sm, Zr is zirconium, Fe is iron, and Co is cobalt. T is at least one element selected from the group consisting of Ti, V, Mo and W. Ti is titanium, V is vanadium, Mo is molybdenum, and W is tungsten. M is an unavoidable impurity element and one or more elements selected from the group consisting of Al, Si, Ni, C, O, N, Cr, Cu, Ga, Ag and Au. Al is aluminum, Si is silicon, Ni is nickel, C is carbon, O is oxygen, Cr is chromium, Cu is copper, Ga is gallium, Ag is silver, and Au is gold.

x and y _are each _{Sm (1-x-y)} when set to 1 whole earth site represented by R y Zr _x, the content of Zr and R (molar ratio). At rare earth sites, Sm is the balance of R and Zr.

z is the content ratio (molar ratio) of Co when the entire iron group site represented by Fe _(1-z) Co _z is 1. At the iron group site, Fe is the balance of Co.

a, b, c, and d are the contents (atomic %) of the rare earth site, the iron group site, T, and M, respectively, when the total amount of the magnetic compound of the present disclosure is 100 atomic %. Since b=100-a-c-d in the above formula, the iron group site is the rest of the rare earth site, T, and M in the entire magnetic compound.

The constituent elements of the above formula will be described below.

<Sm>
Sm is a rare earth element and expresses permanent magnet characteristics, and is an essential component of the magnetic compound of the present disclosure. A conventionally known compound having a composition of NdFe ₁₁ N _w having a ThMn ₁₂ type crystal structure exhibits a uniaxial magnetic anisotropy due to N, and thus has a high anisotropic magnetic field. However, since N is desorbed at a high temperature of 600° C. or higher to reduce the anisotropic magnetic field, it has been difficult to achieve high performance due to full-densification such as sintering. On the other hand, the SmFe ₁₁ Ti compound containing Sm as described above is substantially free of N, and is therefore advantageous in terms of full-densification.

<R>
R is one or more rare earth elements other than Sm. In the present specification, unless otherwise specified, the rare earth elements are Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and It is Lu.

In the magnetic compound of the present disclosure, the rare earth element in the magnetic compound is specified as Sm, the content of Sm is specified, and the content of the α-Fe phase in the magnetic compound is minimized. It is difficult to eliminate the rare earth element R other than Sm from the raw material of Sm. _However, in the rare earth site represented by _{Sm (1-x-y)} R y Zr x, if the value of y is 0 to 0.1, the characteristics of the magnetic compounds of the present disclosure, when R is nil And may be considered to be substantially equivalent.

Ideally, the value of y is 0, but excessively increasing the purity of the Sm raw material causes an increase in manufacturing cost. Therefore, the value of y is 0.01 or more, 0.02 or more, It may be 0.03 or more, 0.04 or more, or 0.05 or more. On the other hand, the value of y is preferably low as long as the purity of the Sm raw material does not increase excessively. Therefore, the value of y is 0.09 or less, 0.08 or less, 0.07 or less, or 0.06 or less. You can

<Zr>
A part of Sm and/or R is substituted with Zr and contributes to the stability of the ThMn ₁₂ type crystal structure. Substitution of Sm and/or R in a ThMn ₁₂ type crystal with Zr causes shrinkage of the crystal lattice. As a result, the ThMn ₁₂ type crystal structure is easily maintained even when the magnetic compound is heated to a high temperature (600° C. or higher). On the other hand, in terms of magnetic properties, a strong magnetic anisotropy derived from Sm is weakened by substituting a part of Sm with Zr. Therefore, the Zr content is determined from both aspects of the stability of the ThMn ₁₂ type crystal structure and the magnetic properties.

Zr is essential because it stabilizes the ThMn ₁₂ type crystal structure and suppresses the decomposition of the magnetic compound at high temperatures. Zr, even a small amount, since the effect can be _observed, in the rare earth site represented by _{Sm (1-x-y)} R y Zr x, the value of x may be a 0 than. From the viewpoint of clearly enjoying the effect of Zr, the value of x may be 0.02 or more, 0.04 or more, 0.06 or more, or 0.08 or more. On the other hand, when the value of x is 0.3 or less, the anisotropic magnetic field does not significantly decrease. Further, it is difficult to generate the Fe ₂ Zr phase. If the Fe ₂ Zr phase is hard to generate, the expression of coercive force is hard to be inhibited. From these viewpoints, the value of x may be 0.28 or less, 0.26 or less, 0.24 or less, or 0.22 or less.

So far has been described, Sm, R, and the total content of Zr _is represented by _{Sm (1-x-y)} R y Zr content of the rare earth site represented by _x a. When the content a of rare earth sites is 7.7 atomic% or more, the ThMn ₁₂ type crystal structure becomes difficult to decompose even when the magnetic compound is heated to a high temperature (600° C. or more). When the ThMn ₁₂ type crystal structure is decomposed, the content of the α-Fe phase increases. Therefore, if it becomes difficult to decompose the ThMn ₁₂ type crystal structure, it becomes difficult to increase the content of the α-Fe phase. From this viewpoint, the content a of rare earth sites is preferably more than 7.7 atom %, more preferably 7.8 atom% or more, still more preferably 7.9 atom% or more, and 8.0 atom% or more. Even more preferred. On the other hand, when the content a of the rare earth site is 9.1 atom% or less, the magnetic anisotropy of the magnetic compound is hard to decrease. This is because when a large amount of Sm is replaced with Zr, a large amount of phases other than the magnetic phase are generated and the strong magnetic anisotropy derived from Sm is significantly reduced. From the viewpoint of suppressing the decrease in magnetic anisotropy, the content a of rare earth sites is preferably 8.9 at% or less, more preferably 8.5 at% or less, and even more preferably 8.2 at% or less. ..

Furthermore, as described above, in the overall composition of the magnetic compound, when the Zr content ratio x at the rare earth site and the rare earth site content a satisfy the relationship of a≧1.0x+7.7, the α-Fe phase Content of 2% by volume or less based on the whole magnetic compound.

In this specification, the content of the α-Fe phase is represented by volume% measured according to the following procedure. A magnetic compound is embedded in a resin and polished, and the magnetic compound is observed at a plurality of locations using an optical microscope or SEM-EDX, and the average area ratio of the α-Fe phase on the observed surface is measured by image analysis. The average area ratio means the average of the area ratios measured at individual observation points.

Assuming that the texture in the magnetic compound is not oriented in a specific direction, the relationship of S≈V is established between the average area ratio S and the volume ratio V. From this, regarding the content of the α-Fe phase, the value of the average area ratio (area %) of the α-Fe phase measured in the above-described manner is defined as the content (volume %) of the α-Fe phase. ..

<T>
T is at least one element selected from the group consisting of Ti, V, Mo and W. It can be considered that Ti, V, Mo and W have the same action and effect, respectively. FIG. 3 is a diagram showing a stabilization region of T in an R′Fe _12-v T _v compound (R′ is a rare earth element) (Source: KHJ Buschow, Rep. Prog. Phys) 54, 1123 (1991)). By adding Ti, V, Mo and W as the third element to the binary system of R′-Fe, the ThMn ₁₂ type crystal structure becomes stable and excellent magnetic properties are shown in FIG. Known by.

Conventionally, in order to obtain the stabilizing effect of the T component, a ThMn ₁₂ type crystal structure is formed by adding T in an amount larger than necessary. Therefore, the content rate of the Fe component constituting the magnetic compound becomes low, and the occupied site of the Fe atom that most affects the magnetization is replaced with, for example, the T atom, thereby lowering the overall magnetization. Moreover, when the content of T is large, Fe ₂ T is easily generated.

When the content c of T is less than 7.7 atomic %, the magnetization is less likely to decrease and Fe ₂ Ti is less likely to be generated. From these viewpoints, the content c of T is preferably 7.6 atom% or less, more preferably 6.0 atom% or less, still more preferably 5.6 atom% or less.

On the other hand, when the content c of T exceeds 3.8 atomic %, the ThMn ₁₂ type crystal structure is likely to be stable. From this viewpoint, 4.2 at% or more is preferable, 4.7 at% or more is more preferable, and 5.5 at% or more is even more preferable.

Further, as described above, in the overall composition of the magnetic compound, when the content ratio x of Zr at the rare earth site and the content c of T satisfy the relationship of c≧−2.5x+4.7, the α-Fe phase is obtained. Content of 2% by volume or less based on the whole magnetic compound.

<M>
M is an unavoidable impurity element and one or more elements selected from the group consisting of Al, Si, Ni , C, O, N, Cr, Cu, Ga, Ag and Au. The unavoidable impurities are the impurities contained in the raw materials of the magnetic compounds or the impurities that are mixed in the manufacturing process, and it is unavoidable to avoid their inclusion, or in order to avoid them, the manufacturing cost increases significantly. Impurities that cause Examples of the unavoidable impurity element include Mn and the like.

M (excluding incidental impurity elements), the viscosity of the suppression of grain growth of the _12-inch ThMn crystal, or a phase other than the phase with the crystal structure of _12-inch ThMn (e.g., the grain boundary phase), which contributes to the melting point However, it is not essential in the magnetic compound of the present disclosure.

The content d of M is 1.0 atomic% or less. When the content d of M is 1.0 atomic% or less, the content rate of the Fe component constituting the magnetic compound becomes low, and as a result, the overall magnetization is unlikely to decrease. From this viewpoint, the content d of M is preferably 0.8 at% or less, more preferably 0.6 at% or less, and even more preferably 0.4 at% or less.

On the other hand, from the viewpoint of clearly enjoying the effects of M (excluding inevitable impurity elements), the content of M is preferably 0.1 atom% or more, more preferably 0.2 atom% or more, Even more preferably, it is 3 atomic% or more. Further, when one or more elements selected from the group consisting of Al, Si, Ni, C, O, N, Cr, Cu, Ga, Ag and Au is not contained, the content d of M is unavoidable. It is the content. The content of the unavoidable impurities is preferably as small as possible. However, if the content of the unavoidable impurities is excessively reduced, the manufacturing cost is increased, and the magnetic properties of the magnetic compound are not substantially affected. Within the range, a small amount of unavoidable impurities may be contained. From this viewpoint, the lower limit of the content d of M may be 0.05 atom %, 0.1 atom %, or 0.2 atom %.

In the magnetic compound having the Sm-based ThMn ₁₂ type crystal structure, N does not develop uniaxial magnetic anisotropy unlike the magnetic compound having the Nd-based ThMn ₁₂ type crystal structure. N penetrates into the grain boundary phase to reduce the magnetic decoupling property, and when a magnet is made of a magnetic compound, N may reduce the coercive force. From this, the content of N is preferably 100 ppm or less, more preferably 70 ppm or less, and further preferably 40 ppm or less, based on the entire magnetic compound (overall composition). On the other hand, if the content of N is excessively reduced, the manufacturing cost is increased, and therefore, a small amount of N may be contained within a range that does not substantially affect the magnetic properties of the magnetic compound. From this viewpoint, the lower limit of the N content may be 10 ppm, 20 ppm, or 30 ppm.

<Fe and Co>
In the magnetic compound of the present disclosure, Fe other than the above elements is Fe, but a part of Fe may be replaced with Co. When part of Fe is replaced with Co, part of Fe in the α-Fe phase is replaced with Co. In the present specification, when expressed as an α-Fe phase, unless otherwise specified, the α-Fe phase includes a phase in which a part of Fe in the α-Fe phase is replaced with Co.

By substituting a part of Fe with Co, the spontaneous magnetization is increased by the Slater-Pauling rule, and both the anisotropic magnetic field and the saturation magnetization are improved. Further, since a part of Fe is replaced by Co, the Curie point of the magnetic compound rises, which has an effect of suppressing a decrease in magnetization at high temperature.

In order to clearly enjoy these effects, the Co content ratio (molar ratio) z is 0.05 or more when the whole iron group site represented by Fe _(1-z) Co _z is 1. Preferably, it is 0.10 or more, more preferably 0.15 or more.

On the other hand, even if the Co content is excessive, it is difficult to obtain the effect according to the Slater Pauling rule. When the Co content ratio (molar ratio) z is 0.30 or less, the effect of the Slater-Pauling rule is not easily weakened. From this viewpoint, the Co content ratio (molar ratio) z is preferably 0.26 or less, more preferably 0.24 or less, and even more preferably 0.20 or less.

<Crystal structure>
The magnetic compound of the present disclosure has a ThMn ₁₂ type crystal structure. The crystal structure of ThMn ₁₂ type is tetragonal. The Sm-based ThMn ₁₂ type crystal structure exhibits the strongest X-ray diffraction intensity when 2θ is 42.46° ((321) plane) by X-ray diffraction (XRD) of a Cu radiation source. Further, when 2θ is 33.07° ((310) plane), weak X-ray diffraction intensity is exhibited.

In the ThMn ₁₂ type crystal structure, the X-ray diffraction intensity at 2θ of 42.46° ((321) plane) was measured by I _c (321) and 2θ at 33.07° ((310) plane). When the intensity is represented by I _c (310) and I _c (321) is 100, I _c (310) is 13.6.

It is known that when the Sm-based ThMn ₁₂ type crystal structure collapses (disorders), it changes to a ThMn ₉ type (1-9 type) crystal structure. The ThMn ₉ type crystal structure shows the strongest X-ray diffraction intensity when 2θ is 42.68° ((111) plane) by X-ray diffraction (XRD) of a Cu radiation source. However, when 2θ is 33°, the X-ray peak does not appear.

From these facts, when the actual measurement value of the X-ray diffraction intensity on the (310) plane of the magnetic compound is Im(310), the ThMn ₁₂ type crystallinity is defined by I _m (310)/I _c (310). be able to. The ThMn ₁₂ type crystallinity indicates the proportion of the Sm-based ThMn ₁₂ type crystal structure in the magnetic compound. If the crystal structure is perfect ThMn ₁₂ type, the ThMn ₁₂ type crystallinity is 100%, and if the crystal structure is perfect ThMn ₉ type, the ThMn ₁₂ type crystallinity is 0%.

In the magnetic compound of the present disclosure, the ThMn ₁₂ type crystal structure occupies 50% or more, that is, the ThMn ₁₂ type crystallinity is preferably 50% or more. When the ThMn ₁₂ type crystallinity is 50% or more, the ThMn ₁₂ type crystal structure is stabilized in the magnetic compound, and as a result, the α-Fe phase is difficult to increase. From the viewpoint of the stability of the ThMn ₁₂ type crystal structure, the higher the ThMn ₁₂ type crystallinity, the more preferable, and 60% or more, 70% or more, 80% or more, or 90% or more is preferable. On the other hand, the ThMn ₁₂ type crystallinity does not have to be 100% and may be 98% or less, 96% or less, 94% or less, or 92% or less.

As described above, according to the magnetic compound of the present disclosure, the content of the α-Fe phase in the magnetic compound can be minimized.

"Production method"
The method for producing a magnetic compound according to the present disclosure includes a molten metal preparation step and a molten metal quenching step. Hereinafter, each of these steps will be described.

<Molten metal preparation process>
In the magnetic compound of the present disclosure, as described above, the overall composition of the magnetic compound and the composition of the molten metal prepared when manufacturing the magnetic compound are substantially the same. Regarding the composition of the molten metal, it is not taken into consideration that the components of the molten metal are depleted due to evaporation during the holding and/or solidification of the molten metal. When the molten metal component is worn out due to manufacturing conditions and the like, the raw materials may be blended in consideration of the amount of wear.

If the melt depletion does not need to be considered, the molten metal having a composition represented by the formula _{(Sm (1-x-y} ) R y Zr x) a (Fe (1-z) Co z) b T c M d prepare. In the above formula, Sm, R, Zr, Fe, Co, T, and M are the same as those described in the magnetic compound. Further, x, y, and z, and a, b, c, and d are the same as those described in the magnetic compound. Then, in the above equation, the relationship of a≧1.0x+7.7 and c≧−2.5x+4.7 is satisfied.

<Melted metal quenching process>
The molten metal having the above composition is rapidly cooled at a rate of 1×10 ² to 1×10 ⁷ K/sec. The rapid cooling stabilizes the ThMn ₁₂ type crystal structure and facilitates minimizing the α-Fe phase content.

As the rapid cooling method, for example, a rapid cooling device 10 as shown in FIG. 4 may be used to cool at a predetermined rate by the strip casting method. In the quenching apparatus 10, the raw materials are melted in the melting furnace 11, and the molten metal 12 having the above composition is prepared. The molten metal 12 is supplied to the tundish 13 at a constant supply amount. The molten metal 12 supplied to the tundish 13 is supplied to the cooling roll 14 from the end portion of the tundish 13 by its own weight.

The tundish 13 is made of ceramics or the like, and can temporarily store the molten metal 12 continuously supplied from the melting furnace 11 at a predetermined flow rate, and can rectify the flow of the molten metal 12 to the cooling roll 14. The tundish 13 also has a function of adjusting the temperature of the molten metal 12 immediately before reaching the cooling roll 14.

The cooling roll 14 is formed of a material having a high thermal conductivity such as copper or chromium, and the surface of the cooling roll 14 is plated with chromium or the like in order to prevent corrosion with a high temperature molten metal. The cooling roll 14 can be rotated in the direction of the arrow at a predetermined rotation speed by a driving device (not shown). By controlling this rotation speed, the cooling rate of the molten metal can be controlled to a rate of 1×10 ² to 1×10 ⁷ K/sec.

When the cooling rate of the molten metal is 1×10 ² K/sec or more, the ThMn ₁₂ type crystal structure can be stabilized, and the α-Fe phase content can be easily minimized. From this viewpoint, the cooling rate of the molten metal is more preferably 1×10 ³ K/sec or more. On the other hand, when the cooling rate of the molten metal is 1×10 ⁷ K/sec or less, there is little possibility that the molten metal is cooled at an unnecessarily fast rate, although the effect obtained by the rapid cooling is saturated. The cooling rate of the molten metal may be 1×10 ⁶ K/sec or less or 1×10 ⁵ K/sec or less.

The molten metal 12 that has been cooled and solidified on the outer periphery of the cooling roll 14 becomes a thin piece 15 that is separated from the cooling roll 14 and collected by a collecting device. If necessary, the thin pieces 15 may be crushed using a cutter mill or the like to obtain powder.

<Heat treatment process>
Further, in the manufacturing method of the present disclosure, the thin piece 15 obtained in the above step may be heat-treated at 800 to 1300° C. for 2 to 120 hours. By this heat treatment, a phase having a ThMn ₁₂ type crystal structure (hereinafter, sometimes referred to as “ThMn ₁₂ phase”) is homogenized, and both the characteristics of anisotropic magnetic field and saturation magnetization are further improved. The pulverization of the thin piece 15 may be performed before the heat treatment or after the heat treatment.

When the heat treatment temperature is 800° C. or higher, the ThMn ₁₂ phase can be homogenized. From the viewpoint of homogenization of the ThMn ₁₂ phase, 900°C or higher is preferable, 1000°C or higher is more preferable, and 1100°C or higher is even more preferable. On the other hand, when the heat treatment temperature is 1300° C. or lower, there is little possibility that the structure of the magnetic compound is decomposed and the α-Fe phase is generated. From this viewpoint, the temperature is preferably 1250° C. or lower, more preferably 1200° C. or lower, still more preferably 1150° C. or lower.

Hereinafter, the magnetic compound of the present disclosure and the method for producing the same will be described in more detail with reference to Examples and Comparative Examples. The magnetic compound and the method for producing the same according to the present disclosure are not limited to the conditions used in the following examples.

<<Preparation of sample>>
A sample of magnetic compound was prepared as follows.

A molten metal having the composition shown in Table 1 was prepared, quenched by a strip casting method at a rate of 10 ⁴ K/sec to prepare a quenched thin piece, and heat-treated at 1200° C. for 4 hours in an Ar atmosphere. Next, in an Ar atmosphere, the flakes were crushed using a cutter mill, and particles having a particle size of 20 μm or less were collected.

<<Evaluation of sample>>
The size and area ratio of the α-Fe phase were measured from the SEM image (backscattered electron image) of the obtained particles, and the content (volume %) of the α-Fe phase was calculated as the area ratio=volume ratio. Further, the obtained particles were subjected to X-ray diffraction (XRD), and the ThMn ₁₂ type crystallinity was calculated by the method described above.

The results are shown in Table 1. In Table 1, for the overall composition of the magnetic compound, a sample was taken from the magnetic compound and analyzed by ICP emission spectroscopy. Since a trace amount of unavoidable impurities was detected as M, the content of M is shown in Table 2. In addition, ppm in Table 2 is mass ppm. The analysis results in Table 1 were almost the same as the composition of the molten metal charged. From the analysis results in Table 1, the relationship between the Zr content ratio x and the rare earth site contents a and Ti contents c was summarized for the overall compositions of the magnetic compounds of Examples 1 to 8 and Comparative Examples 1 to 6. The graph is shown in FIG.

As can be seen from Table 1 and FIG. 1, in the samples of Examples 1 to 8, the content of the α-Fe phase was 2% by volume or less because the entire composition of the magnetic compound was in the proper range. I was able to confirm that. Further, in Examples 1 to 8, it was confirmed that the ThMn ₁₂ type crystallinity was 50% by volume or more.

On the other hand, in the samples of Comparative Examples 2 to 5, it was confirmed that the content of the α-Fe phase exceeded 2% by volume because the entire composition of the magnetic compound was not within the proper range.

In the sample of Comparative Example 1, although the content of the α-Fe phase was 2% by volume or less, when the magnetic compound did not contain Zr (z=0) and the magnetic compound was exposed to a high temperature (600° C.). , May decompose to form an α-Fe phase.

In the sample of Comparative Example _6, a rare earth site represented by _{Sm (1-x-y)} R y Zr x, the proportion x of Zr is exceeded the upper limit of the present invention, _Fe 2 Zr phase generation It had been.

Regarding the overall composition of the magnetic compound, there are a method of displaying the content of each of the rare earth site, the iron group site, Ti, and M in atomic %, and a method of displaying the content in molar ratio. For reference, Table 3 shows the overall composition of the magnetic compound by both methods. Since the content of M is very small, the display of the content of M was omitted in the molar ratio display.

The magnetic compound has a magnetic phase and a grain boundary phase. Using the EPMA ZAF method, the composition of the magnetic phase can be measured separately from the composition of the grain boundary phase. Table 4 is a summary of the measurement results of the composition of the magnetic phase. Table 4 also shows the entire composition of the magnetic compound shown in Table 1. Further, in Table 4, the content of the rare earth site, the iron group site, and Ti with respect to the composition of the magnetic phase is shown by both a method of displaying it in atomic% and a method of displaying it in a molar ratio. Since the content of M is very small, the composition of the magnetic phase is shown by omitting the content of M.

Further, from Table 4, a graph summarizing the relationship between the Zr content ratio x′, the rare earth site content p, and the Ti content q for the compositions of the magnetic phases of Examples 1 to 8 and Comparative Examples 1 to 6. Is shown in FIG.

As can be seen from FIG. 5, the compositions of the magnetic phases of Examples 1 to 8 and Comparative Examples 1 to 6 have a linear relationship between x′ and p, and the inclination is positive, x′ and q It was confirmed that there was a linear relationship between the two and the slope was negative.

From these results, the effects of the magnetic compound of the present disclosure and the method for producing the same were confirmed.

10 Quenching device 11 Melting furnace 12 Molten metal 13 Tundish 14 Cooling roll 15 Thin piece

Claims (5)

Formula _{(Sm (1-x-y} ) R y Zr x) a (Fe (1-z) Co z) b T c M d
(In the above formula, R is one or more rare earth elements other than Sm,
T is one or more elements selected from the group consisting of Ti, V, Mo and W,
M is an unavoidable impurity element and one or more elements selected from the group consisting of Al, Si, Ni, C, O, N, Cr, Cu, Ga, Ag and Au, and
0<x≦0.3,
0≦y≦0.1,
0≦z≦0.3,
7.7<a≦9.1,
b=100-a-c-d,
3.8<c≦ 5.6 , and
0≦d≦1.0)
Has a composition represented by
In the above formula, the relationship of a≧1.0x+7.7 and c≧−2.5x+4.7 is satisfied, and
Has a ThMn ₁₂ type crystal structure,
Magnetic compound. The magnetic compound according to claim 1, which contains 10 to 100 ppm by mass of N. Formula _{(Sm (1-x-y} ) R y Zr x) a (Fe (1-z) Co z) b T c M d
(In the above formula, R is one or more rare earth elements other than Sm,
T is one or more elements selected from the group consisting of Ti, V, Mo and W,
M is an unavoidable impurity element and one or more elements selected from the group consisting of Al, Si, Ni, C, O, N, Cr, Cu, Ga, Ag and Au, and
0<x≦0.3,
0≦y≦0.1,
0≦z≦0.3,
7.7≦a≦9.1,
b=100-a-c-d,
3.8<c≦ 5.6 , and
0≦d≦1.0)
And has a composition represented by
In the above formula, preparing a molten metal satisfying the relationship of a≧1.0x+7.7 and c≧−2.5x+4.7, and
Quenching the molten metal at a rate of 1×10 ² to 1×10 ⁷ K/sec to obtain flakes;
The method for producing a magnetic compound according to claim 1, comprising: The method according to claim 3 , which contains 10 to 100 ppm by mass of N. The method according to claim 3 or 4 , further comprising heat treating the flakes at 800-1300°C for 2-120 hours.

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