JP3017835B2 - Method for producing iron-rare earth-nitrogen based magnetic material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an iron-rare earth-nitrogen magnetic material having excellent magnetic properties.

[0002]

2. Description of the Related Art One or two selected from the group consisting of Co and R (Y, Th and all lanthanoid elements)
Some of the intermetallic compounds comprising a combination of more than one element exhibit high crystal magnetic anisotropy and large saturation magnetization, and are promising as permanent magnet materials having high coercive force and high energy product. . However, since Co is expensive, it is desirable to reduce its usage from an industrial point of view. Also,
Since the saturation magnetization of Fe is larger than the saturation magnetization of Co, there is a possibility that the Fe-based alloy can obtain a larger saturation magnetization than the Co-based alloy. However, it is often difficult to obtain a high Curie point or uniaxial crystal magnetic anisotropy with a binary alloy composed of only Fe—R. For this purpose, a material improved in this respect by adding N as a third element has been provided by the present inventor (JP-A-60-131944). However, as described in detail in the specification of the application, N is not localized in the material in the form of a nitride with Fe, R, etc., but exists as an interstitial interpenetrating atom. Must exist so as to give a change to the lattice itself composed of Fe and R.

[0003]

However, it is said that the above-mentioned state of nitrogen may be relatively unstable. In particular, it is said that it is unstable at high temperatures and gradually decomposes to α-Fe and rare earth-nitrogen compounds from about 700 ° C. or more. For this reason, it is said that it is difficult to use an iron-rare earth-nitrogen based magnetic material as a sintered material.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to improve this point. The present invention provides a sub-zero treatment for an iron-rare earth-nitrogen based magnetic material so that the presence of nitrogen as described above can be improved. The state, that is, N is not evenly localized in the material in the form of a nitride with Fe, R, etc., but is present as an interstitial interpenetrating atom. The presence of nitrogen in the form realizes the stabilization of the existing state of nitrogen, which acts to change the lattice itself composed of Fe and R. That is, in the present invention, when R is one or a combination of two or more elements selected from the group consisting of Y, Th, and all lanthanoid elements, R: 3 to 3 in atomic percentage.
0%, N (nitrogen): 0.3 to 50%, with the balance being substantially Fe, wherein the iron-rare-earth-nitrogen-based magnetic material is made of a sub-zero treatment. A method for producing an iron-rare earth-nitrogen based magnetic material. Hereinafter, the method for producing an iron-rare earth-nitrogen based magnetic material of the present invention will be described in detail. First, iron
A rare earth-nitrogen based magnetic material is prepared. Of particular note is the method of adding nitrogen. As described above, N is F
The presence of N in the lattice in a substantially uniform form, such as interstitial interstitial atoms, instead of being localized in the material in the form of a nitride with e, R, etc. It must be present in the material in such a way as to give a change to the lattice itself consisting of Fe and R. To do this,
As a method of causing N to be contained in the material, a method that originally contains N may be used as a raw material, but rather, an iron-rare earth alloy is first prepared by a conventional method, and then the subsequent steps are performed. In this method, it is recommended that N be introduced into the material by treating in an appropriate gas or liquid. Examples of the gas used for infiltrating N include N ₂ gas, N ₂ + H ₂ mixed gas, NH ₃ gas, and a mixed gas thereof (including a case where the gas is diluted with H ₂ gas or other inert gas).
Can be used. In this case, the processing temperature may be generally 200 to 1000 ° C, particularly 400 to 700 ° C. In addition, the processing time in that case may be generally about 0.2 to 50 hours, but may be appropriately selected according to the desired characteristics of the material. Iron prepared as described above
Sub-zero treatment is performed on the rare earth-nitrogen based magnetic material. In the present invention, the sub-zero treatment is not performed in the "low-temperature phase" of the iron-rare earth-nitrogen based magnetic material, that is, N is localized in the material in the form of a nitride with Fe, R, etc. Since N exists in the lattice in a substantially uniform form, such as being present as an interstitial atom, the nitrogen acts in such a manner as to act to change the lattice itself composed of Fe and R. Has a great effect on the stabilization of the phase in which is present. Here, “sub-zero processing” means processing at a temperature of 0 ° C. or lower (“sub-zero processing” may be referred to as “deep cooling processing”). Generally, dry ice (sublimation point: −79 ° C.) is used.
In some cases, the treatment up to 0 ° C. is distinguished as “normal sub-zero treatment”, and the treatment using liquid nitrogen (boiling point: −196 ° C.) or less at −130 ° C. or less is referred to as “ultra-sub-zero treatment”. Without further explanation, it will be simply referred to as “sub-zero processing”. In the present invention, the reason why such sub-zero processing is effective is considered to be as follows. In the first case, after the material has been subjected to the N intrusion treatment as described above, the material has not been exposed to a very high temperature, and thus the decomposition into α-Fe and the rare earth-nitrogen compound has not progressed so much. That is, the transformation reaction involving long-range diffusion of atoms has hardly progressed. In this case, even if the “low-temperature phase” is becoming somewhat unstable for some reason, the “low-temperature phase” is firmly stabilized by performing the sub-zero treatment of the present invention. The effect of is greatly exhibited. This is considered to be due to the fact that, from a thermodynamic point of view, the lower the temperature, the smaller the entropy term in the free energy and the larger the contribution of the enthalpy term. Moreover, in the first case, since the local composition does not change much because the long-range diffusion of atoms does not occur, if the entropy is reduced only by performing the sub-zero treatment of the present invention. It seems that each atom can recover to the complete "low-temperature phase" very easily by non-diffusion transformation such as martensitic transformation with only slight displacement. The second case is when the material has been subjected to a relatively high temperature after being subjected to the N intrusion treatment as described above, for example, has been subjected to a sintering treatment. In this case,
Since decomposition into α-Fe and rare earth-nitrogen compounds, that is, a transformation reaction accompanied by long-range diffusion of atoms has progressed, local compositional changes in the material have occurred. However, it is impossible to recover the "low temperature phase" by the non-diffusion transformation as in the first case. Therefore, in this case, it is effective to carry out the sub-zero treatment of the present invention after once bringing the material to a temperature as high as possible. The reason for once raising the material to as high a temperature as possible is that it increases the entropy and the atomic disorder, ie, the α produced in the “medium temperature” region.
This is for destroying -Fe and rare earth-nitrogen compounds to measure a uniform element concentration distribution. However, at this time, it is needless to say that it is necessary to pay sufficient attention to the heat treatment conditions such as the atmosphere so that the nitrogen does not diffuse out of the material. After completion of the heat treatment, the mixture is cooled to the “low temperature range” as soon as possible, so that α-Fe and rare-earth
It is necessary to prevent nitrogen compounds from being formed again. In such a case, it may be better to immerse the material in water or oil or the like and then perform the sub-zero treatment, rather than immersing the material in liquid nitrogen immediately after performing the sub-zero treatment of the present invention. The reason is that if the heated material is suddenly immersed in liquid nitrogen, the vaporization reaction of nitrogen will be so intense that a large amount of air bubbles will be generated, enclosing the material, and the cooling effect may be weakened. This is wasteful and uneconomical. However, in some cases, it is possible to prevent cracking of the material due to quenching by taking advantage of the fact that the cooling rate is initially slowed by the generation of bubbles, so that the heated material is immediately immersed in liquid nitrogen. Sometimes it is more effective. In the sub-zero treatment of the present invention, the holding time at a predetermined processing temperature (for example, liquid nitrogen temperature) does not usually have a great effect on obtaining the effect of the present invention, and therefore, the material is not affected by the temperature. You only have to reach it. However, in order to ensure the effect sufficiently, it is preferable that the material is immersed for at least about one minute after reaching the target temperature. Also,
If the reaction is continued for a longer period of time (several hours or several days), the reaction may gradually progress. In the present invention, R is a very important constituent element that plays an essential role in generating magnetic anisotropy and generating coercive force when the magnetic material is used as a permanent magnet material. R represents Y, Th and all lanthanoid elements, that is, Y, La, Ce, Pr, Nd, Pm, Sm, Eu,
Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Th are included and may be used as a combination of one or more elements selected from the group consisting of these. In the material of the present invention, R is Sm, Nd, Pr, D
One or more elements selected from y and Ce are particularly effective. R needs to be in the range of 3 to 30%, preferably 5 to 20%, more preferably 7 to 15% in atomic percentage. If R is less than 3%, no holding power can be obtained, so the lower limit of R is set to 3%. On the other hand, if R is 30
%, The saturation magnetization becomes too small, and the material is very oxidized, resulting in extremely poor corrosion resistance. Therefore, the upper limit of R is set to 30%. In order to obtain stable magnetic properties, it is desirable that the amount of R is usually selected in the range of 5 to 20%. In particular, when the amount of R is 7 to 15%, large saturation magnetization is easily obtained. In order to obtain permanent magnet characteristics with a small amount of R, the main phase may have a ThMn _12- type body-centered tetragonal structure. To that end, it is effective to select R to be 7 to 10%. It is. In the present invention, N (nitrogen)
Is an important element effective in increasing the saturation magnetization and generating high coercive force when the present magnetic material is used as a permanent magnet material, but its content is 0.3 atomic percent. ５０50%, preferably 2-20%, more preferably 5-15%. N
Is less than 0.3%, the effect of adding N is not recognized, and the saturation magnetization is small. Therefore, the lower limit of N is set to 0.3%. On the other hand, if N exceeds 50%, the saturation magnetization is rather too small, so the upper limit of N is set to 50%. In order to obtain stable magnetic properties, the amount of N is usually 2 to 20%, especially 5 to 1%.
It is desirable to select in the range of 5%. However, as described above, N is not localized in the material in the form of a nitride with Fe, R, etc., but exists as an interstitial interpenetrating atom.
Must be present in the material in such a way that the presence of Al in the lattice in a substantially uniform manner changes the lattice itself made of Fe and R itself. For this purpose, N may be contained in the material by using a material which originally contains N as a raw material, but rather, in a later step, treatment is carried out in an appropriate gas or liquid. By doing
The method of infiltrating into the material is recommended. As a gas used for infiltrating N, N ₂ gas, N ₂ + H ₂
Mixed gas, NH ₃ gas, and a mixed gas thereof (H
₍ Including the case of dilution with _two gases or another inert gas). In this case, the processing temperature is usually 200 to 1000 ° C, particularly 400 to 70 ° C.
The temperature may be set to 0 ° C. In addition, the processing time in that case may be generally about 0.2 to 50 hours, but may be appropriately selected according to the desired characteristics of the material. In the present invention, M is an element having a great effect in generating a body-centered tetragonal structure. As described above, it is often difficult to obtain a high Curie point or uniaxial crystal magnetic anisotropy with an alloy composed of only a Fe—R binary system. It is not suitable as a permanent magnet material from both points of view and crystal magnetic anisotropy. However, in recent years,
Attempts have been made to improve the characteristics by adding Ti, V, Cr, Al, Si, Mo and W as elements of (KHJ Bushow: Journal of Applied Physics, 63).
Volume, p. 3130, published in 1988). That is, G is Ti, V,
When Cr, Al, Si, Mo, and W are used, Sm (Fe
G) An alloy having a composition of ₁₂ stabilizes the body-centered tetragonal structure, which indicates excellent permanent magnet properties. Among them, SmFe ₁₁ Ti is said to be excellent. M is an element having a great effect in generating this body-centered tetragonal structure. M is Ti, Cr, V, Z
r, Nb, Al, Mo, Mn, Hf, Ta, W, Mg,
Si, Sn, and Ge are included and may be used as a combination of one or more elements selected from the group consisting of Si, Sn, and Ge. In order to exert these effects, the amount of M may be 0.5 to 30% in atomic percentage, but is usually 1%.
It is preferably about 15%. If M is less than 0.5%, the above effects cannot be obtained, so the lower limit of M is set to 0.5%. On the other hand, if M exceeds 30%, the saturation magnetization becomes too small, so the upper limit of M is set to 30%. Among them,
In order to obtain stable magnetic properties, the amount of M is usually 1 to 1
It is desirable to select in the range of 5%. In the present invention, F
By replacing a part of e with X, the saturation magnetization is increased, and S is also effective in obtaining a high coercive force when the present magnetic material is used as a permanent magnet material. Here, X is C (carbon) or B (boron) or a combination of these elements. X shows substantially the same effect as complementing the effect of N (nitrogen). However, as a method for incorporating N into the material, it is recommended that N be introduced into the material by treating it in an appropriate gas or liquid as described above. Regarding the method of containing X, it is generally possible to use a material that originally contains X as a raw material. However, in this case, if the compound in the form of X is used, a very stable compound such as a carbide with the element M,
A carbide with R, a boride with M element, a boride with R, and the like do not dissociate into a single X atom form in the alloy, and therefore, it is often difficult to exist as interstitial atoms. So less preferred. As a raw material of X, a pure element such as graphite or metal boron, or a compound having relatively low stability, for example, a carbide with Fe such as Fe ₃ C, or general ferroboron is recommended. In the present invention,
B is characterized in that it is easiest to add B from the raw material into the alloy as compared with the other two interstitial elements N and C. Further, N and C or B have a common point in that both are atoms that can exist in an interstitial manner, but as described above, C and B are from raw materials, N is from gas, If the elements are intentionally included in the alloy through different mechanisms, each element can occupy the interstitial position which is more likely to be occupied by each mechanism. It is expected that the use of the interstitial structure can make the formation of the interstitial interstitial structure more reliable. It is expected that there will be a difference in the details of the mechanism between N and X due to such a difference in the mechanism.
It is also expected that there is a difference between B and B due to differences in atomic diameter, valence (= electronic structure) and the like. In order to obtain these effects, the content of X must be 0.1 atomic percent.
It needs to be in the range of 3 to 50%, preferably 2 to 20%, more preferably 5 to 15%. X is 0.3
%, The effect of addition of X is not recognized and the saturation magnetization is small. Therefore, the lower limit of X is set to 0.3%. On the other hand, when X exceeds 50%, the saturation magnetization is rather too small.
Is 50%. In order to obtain stable magnetic properties, it is desirable that the amount of X is selected in the range of usually 2 to 20%, particularly 5 to 15%. In the present invention, the temperature characteristics of the magnetic properties of the material can be improved by substituting a part of Fe with Co. For this purpose, the amount of Co is desirably in the range of 1 to 50%, preferably 5 to 30% in atomic percentage. If the Co content is less than 1%, the effect of improving the temperature characteristics of the material magnetic properties is small, and if it exceeds 50%, the saturation magnetic flux density gradually decreases. Co amount 5
By selecting from 30% to 30%, the effect of improving the temperature characteristics is remarkable.
In the present invention, the corrosion resistance of the material can be improved by substituting a part of Fe with Ni. For this purpose, the amount of Ni is desirably in the range of 0.5 to 30%, preferably 2 to 10% in atomic percentage. If it is less than 0.5%, the effect of improving the corrosion resistance is small, and if it exceeds 30%, the saturation magnetic flux density decreases. By subjecting the various iron-rare earth-nitrogen based magnetic materials as described above to the sub-zero treatment of the present invention, various crystal structures can appear by selecting the conditions.
Those having a main phase of an h ₂ Zn ₁₇ type rhombohedral structure, a Th ₂ Ni ₁₇ type hexagonal structure and a ThMn ₁₂ type body centered tetragonal structure are particularly useful as permanent magnet materials.

[0005]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto. (Example 1) Fe 70.8%, Sm 29.2% by weight ratio
Was melted in an argon atmosphere. This alloy corresponds to 86.7% of Fe and 13.3% of Sm in atomic%. The obtained ingot was annealed at 1050 ° C. for 5 hours, and then pulverized using an iron mortar and a disc mill to about 15 minutes.
A powder having a diameter of μm was obtained. This powder was treated at a temperature of 550 ° C. in N ₂ gas in order to incorporate N in the powder. As a result of this treatment, 2.71% by weight of N was contained in the material. From this calculation, the composition of the material as a whole is
Atomic%: Fe 76.4%, Sm 11.7%, N 11.9
%become. Next, according to the present invention, a sub-zero treatment was performed in which the obtained powder was immersed in liquid nitrogen and held for 30 minutes. After this treatment, the sample was taken out of the liquid nitrogen and at the same time put in a desiccator to return to room temperature while preventing dew condensation. The powder obtained in this way is 20 kOe
After being oriented in a magnetic field of, it was solidified with wax and its magnetic properties were measured. The saturation magnetization (4πIs) was 12
3 emu / g and coercive force (Hc) were 2100 Oe. For comparison, the magnetic properties of the powder that was not subjected to the sub-zero treatment had a saturation magnetization (4πIs) of 115 e.
mu / g and coercive force (Hc) were 1800 Oe. (Example 2) A powder having a diameter of about 15 µm was obtained in the same manner from the same alloy used in Example 1. This powder was treated at a temperature of 550 ° C. in N ₂ gas in order to incorporate N in the powder. This powder was further subjected to jet mill pulverization using N ₂ gas to obtain a powder having a diameter of about 5 μm.
It was oriented and pressed in the magnetic field of e. After sintering the molded body in N ₂ gas at a temperature of about 1200 ° C., the molded body was immersed in liquid nitrogen in a stainless steel container for 15 mi.
n was retained and sub-zero processed. Next, this sample was transferred to liquid nitrogen in a Dewar bottle, immersed, and
Sub-zero treatment for 6h retention was further performed. After the holding, the sample was taken out and returned to room temperature, and then the surface of the sample was removed by about 1 mm by grinding to obtain a test material. As a result of gas analysis, N in this sample was 2.33% by weight. Calculating from this, the composition of the material as a whole is Fe77.7 in atomic%.
%, Sm 11.9%, and N 10.4%. When the magnetic properties of this sample were measured, the saturation magnetization (4πI
s) is 138 emu / g and coercive force (Hc) is 2300 O
e. (Example 3) Fe 65.7% by weight, Sm 23.0
% And 11.3% of Ti were melted in an argon atmosphere. This alloy contains 75.2% Fe in atomic%, Sm
9.77% and 15.0% of Ti. The obtained ingot was annealed at 1050 ° C. for 5 hours, and then pulverized using an iron mortar and a disc mill to obtain a powder having a diameter of about 15 μm. This powder was treated at a temperature of 550 ° C. in N ₂ gas in order to incorporate N in the powder. As a result of this treatment, 3.73% by weight of N was contained in the material. Calculating from this, the composition of the material as a whole is Fe63.9 in atomic%.
%, Sm 8.31%, Ti 12.8%, and N 15.0%. Next, based on the present invention, a sub-zero treatment was performed in which the obtained powder was immersed in liquid nitrogen and held for 5 hours as it was. After this treatment, the sample was taken out of the liquid nitrogen and at the same time put in a desiccator to return to room temperature while preventing dew condensation. The powder obtained in this way is 20 kOe
After being oriented in a magnetic field of, it was solidified with wax and its magnetic properties were measured. The saturation magnetization (4πIs) was 11
It was 1 emu / g. For comparison, the magnetic properties of the powder that was not subjected to the sub-zero treatment were the saturation magnetization (4
πIs) was 98 emu / g.

[0006]

As described above, according to the method for producing an iron-rare earth-nitrogen based magnetic material according to the present invention, an excellent magnetic material, particularly a material which can be an excellent permanent magnet material, can be stably produced. It is very useful in practice.

Claims (16)

(57) [Claims] 1. When R is one or a combination of two or more elements selected from the group consisting of Y, Th and all lanthanoid elements, R: 3 to 3 in atomic percentage.
0%, N (nitrogen): 0.3 to 50%, with the balance being substantially Fe, wherein the iron-rare-earth-nitrogen-based magnetic material is made of a sub-zero treatment. A method for producing an iron-rare earth-nitrogen based magnetic material. 2. The method for producing an iron-rare earth-nitrogen magnetic material according to claim 1, wherein the sub-zero treatment uses liquid nitrogen. Method. 3. The method for producing an iron-rare earth-nitrogen based magnetic material according to claim 2, wherein the sub-zero treatment using liquid nitrogen is performed after a cooling treatment using water is performed. A method for producing an iron-rare earth-nitrogen based magnetic material, comprising: 4. The method for producing an iron-rare earth-nitrogen based magnetic material according to claim 1, wherein M is Ti, Cr, V, Zr, Nb, Al, Mo, Mn, H
When one or more elements selected from the group consisting of f, Ta, W, Mg, Si, Sn, and Ge are used, the iron-rare earth-nitrogen-based magnetic material is one of Fe Is replaced by M, so that, in atomic percent, M: 0.5
A method for producing an iron-rare-earth-nitrogen-based magnetic material, characterized in that the magnetic material contains about 30%. 5. The method for producing an iron-rare earth-nitrogen based magnetic material according to claim 1, wherein X is C (carbon) or B (boron) or a combination of these elements. At this time, the iron-rare earth-nitrogen based magnetic material is
By substituting a part of e with X, in atomic percent,
X: A method for producing an iron-rare earth-nitrogen based magnetic material, comprising 0.3 to 50%. 6. The method for producing an iron-rare earth-nitrogen based magnetic material according to claim 1, wherein a part of Fe of the iron-rare earth-nitrogen based magnetic material is replaced by Co. A method for producing an iron-rare-earth-nitrogen-based magnetic material, wherein the iron-rare-earth-nitrogen-based magnetic material contains, by atomic percentage, Co: 1 to 50%. 7. The method for producing an iron-rare earth-nitrogen magnetic material according to claim 1, wherein a part of Fe of the iron-rare earth-nitrogen magnetic material is replaced by Ni. As a result, Ni: 0.5 to 30 in atomic percentage.
% Of the iron-rare earth-nitrogen based magnetic material. 8. The method for producing an iron-rare earth-nitrogen based magnetic material according to claim 1, wherein R is one selected from the group consisting of Sm, Nd, Pr, Dy, and Ce. Alternatively, a method for producing an iron-rare earth-nitrogen based magnetic material, comprising two or more elements. 9. The method for producing an iron-rare earth-nitrogen based magnetic material according to claim 1, wherein the iron-rare earth-nitrogen based magnetic material has an atomic percentage of R: 5 to 5%.
20% by mass of the iron-rare earth-nitrogen based magnetic material. 10. The method for producing an iron-rare earth-nitrogen magnetic material according to claim 9, wherein the iron-rare earth-nitrogen magnetic material contains R: 7 to 15% by atomic percentage. A method for producing an iron-rare earth-nitrogen based magnetic material, comprising: 11. The method for producing an iron-rare earth-nitrogen based magnetic material according to claim 10, wherein the iron-rare earth-nitrogen based magnetic material contains R: 7 to 10% by atomic percentage. A method for producing an iron-rare earth-nitrogen based magnetic material, comprising: 12. The method for producing an iron-rare earth-nitrogen based magnetic material according to claim 1, wherein
The iron-rare earth-nitrogen based magnetic material is represented by N:
A method for producing an iron-rare earth-nitrogen based magnetic material, comprising: 2 to 20%. 13. The method for producing an iron-rare-earth-nitrogen-based magnetic material according to claim 12, wherein the iron-rare-earth-nitrogen-based magnetic material contains N: 5 to 15% by atomic percentage. A method for producing an iron-rare earth-nitrogen based magnetic material, comprising: 14. The method for producing an iron-rare earth-nitrogen based magnetic material according to claim 1, wherein
The main phase of the iron-rare earth-nitrogen based magnetic material is Th ₂ Zn ₁₇
A method for producing an iron-rare earth-nitrogen based magnetic material having a rhombohedral structure. 15. The method for producing an iron-rare earth-nitrogen based magnetic material according to claim 1, wherein
The main phase of the iron-rare earth-nitrogen based magnetic material is Th ₂ Ni ₁₇
A method for producing an iron-rare earth-nitrogen based magnetic material having a rhombohedral structure. 16. The method for producing an iron-rare earth-nitrogen based magnetic material according to claim 1, wherein
A method for producing an iron-rare earth-nitrogen based magnetic material, wherein the main phase of the iron-rare earth-nitrogen based magnetic material has a ThMn _12- type body-centered tetragonal structure.