JPH05311390A - Production of fe16n2 iron nitride having high saturation magnetization - Google Patents

Abstract

PURPOSE:To produce an Fe16N2 iron nitride having high saturation magnetization by nitriding the surface of a thin sheet of iron or iron alloy having a specified texture to form Fe16N2 and then etching off the iron or iron alloy. CONSTITUTION:A steel sheet is annealed while impressing a magnetic field in the rolling direction to grow a crystal grain with the [100] axes strongly accumulated in the rolling direction. The iron or iron alloy thin sheet thus obtained is nitrided at about 100-700 deg.C in a nitriding atmosphere while impressing a magnetic field in the rolling direction, and Fe16N2 is formed on the thin sheet surface. The nitrided thin sheet is then preferably quenched and etched with a weak liq. etchant such as aq. several % nitric acid, and the iron or iron alloy is removed and the nitride is extracted. An Fe16N2 iron nitride having high saturation magnetization is stably supplied in large quantities in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an advantageous method for producing Fe ₁₆ N ₂ iron nitride having a high saturation magnetization.

[0002]

2. Description of the Related Art Recent breakthroughs in the electronic industry are greatly owed to the research and development of magnetic materials, but recently, especially due to the downsizing of iron cores, magnetic recording, electrical equipment, and high density of information, saturation has occurred. There is a demand for a magnetic material having a high magnetic moment and good magnetostriction characteristics. In the past, in order to obtain a material with a high magnetic moment, the method of increasing the saturation magnetization by alloying iron was the mainstream, but such alloying additive elements are expensive elements such as Pt and Pd. However, it has not been industrially used yet.

In 1972, Takahashi et al. {Mr. Takahashi: Solid State Physics. Vol. 7 (1972), 483}, {TKKim and M. Takaha.
In Shi: Appl. Phys. Lett. Vol.20 (1972), 492} and {Mr. Takahashi: Academic Monthly Report, Vol.24 (1972), 719},
The saturation magnetization value of the iron thin film deposited in the nitrogen atmosphere of 2 × 10 ^{−4 to} 2 × 10 ⁻³ Torr is 26400 to 29000 Gauss (G), which is higher than that of the pure iron thin film of 21500G. It showed a very interesting experimental result that is much higher. And it was clarified from the crystal structure analysis by electron diffraction that this high saturation magnetization originates from the iron nitride of Fe ₁₆ N ₂ preferentially formed in the iron thin film. After that, Mitsuoka and Chikazumi et al. {Katsuya Mitsuoka, Hideki Miyajima, Sonobu Chikaku, 2nd Annual Meeting of the Applied Magnetics Society of Japan, (1978) P.176} and {Sonobu Chikaku: Applied Physics,
53 (1984), 291}, Fe ₁₆ N ₂ iron nitride is described in B. C.
T. Since the structure is a (Body Centered Tetragonal) structure, it has been shown that the magnetization increases due to the lattice extension caused by the penetration of N atoms.

In addition to the above-mentioned technique, the inventors have proposed {Y.
Inokuti, N.Nishida and N.Ohashi: Met. Trans. 6A (1
975), 733} and {Seio Iguchi: The Japan Institute of Metals, 15 (197)
5), 101}, pure iron single crystal with (100) orientation was treated in a nitriding atmosphere of ammonia and hydrogen gas in the temperature range of 450 ° C to 500 ° C, and 0.5 to 5 μm was formed near the surface of the single crystal sample. The degree of Fe ₁₆ N ₂ preferentially precipitates, and the matching relationship between Fe ₁₆ N ₂ and the matrix is

## EQU1 ## It has been shown that {001} Fe ₁₆ N ₂ // {001} α, <100> Fe ₁₆ N ₂ // <100> α is satisfied.

More recently, Kozono et al. Of Hitachi Research Laboratories noted in the Nikkan Kogyo Shimbun (published November 28, 1989) that the lattice constant of Fe ₁₆ N ₂ is the same as that of indium and gallium arsenide alloys. By the method, a thin film of Fe ₁₆ N ₂ was created.
It was shown to have a saturation magnetization of 29000G. Also NTT
Ono et al. Prepared an Fe thin film on GaAs (100) in N ₂ atmosphere using ECR sputtering method, and Nakajima et al. In Nagaoka University et al. Used Fe on MgO (100) by ion plantation method. Thin films were prepared [Mr. Takahashi: Material for General Purpose Material, November 22, 1990, (JCRM)], and all reported that these thin films had high saturation magnetization.

[0006]

[Problems to be Solved by the Invention] However, Fe ₁₆ N ₂
It is often pointed out that the recent research results on Fe are mainly thin films of Fe, which are too small to be used as industrial materials, so that they are difficult to stably use in large quantities as materials. In addition, since the process of using Fe ₁₆ N ₂ deposited in the Fe thin film is unstable, it is possible to stably obtain Fe ₁₆ N ₂ having a high saturation magnetization, and to use such Fe ₁₆ N ₂ Development of a manufacturing method capable of supplying a large amount of precipitates has been awaited. The present invention advantageously responds to the above-mentioned requirements, and an object thereof is to propose a manufacturing method capable of stably supplying a large amount of Fe ₁₆ N ₂ iron nitride having high saturation magnetization.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to meet the above demands, and as a result, nitrided a thin plate having crystal grains in which the [100] axis was strongly integrated in the rolling direction. by performing processing, Fe ₁₆ N ₂ is preferentially deposited on the surface layer, yet the knowledge that the Fe ₁₆ N ₂ is Fe ₁₆ N ₂ having a high saturation magnetization by extracting by etching easily obtained Obtained. The present invention is based on the above findings.

That is, the present invention is based on [100] crystal grains.
The iron or iron alloy thin plate having a texture in which the axis is strongly integrated in the rolling direction is subjected to a nitriding treatment, Fe ₁₆ N ₂ is preferentially formed on the surface of the thin plate, and then the iron or iron alloy is removed by etching. method of manufacturing a Fe ₁₆ N ₂ iron nitride having a high saturation magnetization which comprises taking out a Fe ₁₆ N ₂ iron nitride (first invention)
Is.

Further, according to the present invention, the [100] axis of the crystal grain is
Iron or iron alloy with a texture that is strongly integrated in the rolling direction
Nitriding treatment is applied to a thin plate while applying a magnetic field in the same direction as the rolling direction.
The surface of the thin plate.₁₆N₂Was formed preferentially
After removing iron or iron alloy by etching,₁₆N₂iron
Fe with high saturation magnetization consisting of taking out nitrides
₁₆N₂It is a method for manufacturing an iron nitride (second invention).

Hereinafter, the experimental results which are the basis of the present invention will be described. C: 0.002 wt% (simply indicated by% hereinafter), Si: 0.003%, Mn: 0.08%, P: 0.005%, S:
0.005%, Al: 0.004%, N: 0.0015% and O: 0.007
%, And the balance is a high-purity molten steel having a composition of substantially Fe.
A hot rolled sheet having a thickness of 1.6 mm was used. Then, a so-called cross rolling in which the cold rolling in the same direction as the hot rolling direction (L direction) and the 90 ° direction (C direction) are alternately performed was performed to obtain a cold rolled sheet having a thickness of 0.15 mm. After that, by annealing at a temperature of 880 ° C. while applying a magnetic field in the rolling direction to grow crystal grains in which the [100] axis is strongly integrated in the rolling direction, the surface is ground,
Then, electrolytically polish it to a mirror finish and then 450 ℃
Nitrogen treatment in the nitrogen atmosphere of
₁₆ N ₂ was deposited. The nitriding treatment was performed under the three conditions shown in Table 1, that is, (a) the sample and the vertical direction, and (b) the sample and the rolling direction, respectively, while applying a 2000 G magnetic field, and (c) without applying a magnetic field. .. Then, Fe ₁₆ N ₂ precipitated on the surface of the steel sheet was extracted using an etching solution composed of a mixed aqueous solution of oxalic acid and H ₂ O ₂ . Fe ₁₆ extracted in this way
The results of examining the saturation magnetization of N ₂ are also shown in Table 1.

[0011]

[Table 1]

As is clear from the table, (b), (c), (a)
The saturation magnetization is higher in the order of. SE of each of these samples
Observation of Fe ₁₆ N _{2 with} M revealed that
As shown in (b) and (c), respectively, a difference was observed in the precipitation state of Fe ₁₆ N ₂ . Moreover, when the same SEM observation was performed on Fe ₁₆ N ₂ after precipitation, the sample of (b) was almost perfect, that is, the paper {Y. Inokuti, N. Nishida and N. Ohashi: Met. Tran
s., 6A (1975), 733} same as 0.5 ~ 5 μm Fe ₁₆ N
It was confirmed that ₂ could be extracted in almost perfect form. On the other hand, under the conditions of (a) and (c), a situation in which Fe ₁₆ N ₂ and Fe were mixed was observed. Further, in this case, it was also observed that the shape of Fe ₁₆ N ₂ was broken by etching.

From the above experimental results, according to the present invention,
Fe with a high degree of [100] -axis integration of crystal grains in the rolling direction
Or for Fe alloy sheet, nitriding, and more preferably under a magnetic field applied to the [100] axial direction, subjected to a nitriding treatment, the Fe ₁₆ N ₂ to prioritize precipitate, then almost completely the Fe ₁₆ N ₂ By extracting in the form, it became possible to stably obtain a magnetic material with high saturation magnetization.

[0014]

The starting material of the present invention is not particularly limited as long as it has Fe as a main component, and the additive element is not particularly limited. However, particularly preferred is a high-purity steel in which each element is restricted as described below.

C: 0.05% or less If C is present in a large amount in the steel, not only the magnetic properties are deteriorated, but also it becomes difficult to develop the crystal grains focused on the [100] axis. Preferably.

Si: 0.001 to 0.1% Si is a useful element that increases the electric resistance and lowers the iron loss, but addition of a large amount causes a decrease in the magnetic flux density, so it is necessary to make it 10% or less, In order to develop the crystal grains that are strongly integrated in the [100] axis, 0.001 to 0.1% is preferable.

Mn: 0.01 to 0.5% Mn effectively contributes to the improvement of workability, but if added in a large amount, not only the magnetic characteristics are deteriorated but also the amount of inclusions such as MnS increases, so 0.01 to 0.5%. A degree is preferable.

P: 0.05% or less P is concentrated in the crystal grain boundaries and the surface in the steel and causes frequent intergranular cracking, so P is preferably suppressed to about 0.05% or less.

S: 0.02% or less S, like P, is a grain boundary segregation element in the steel and is concentrated at crystal grain boundaries and surfaces to cause frequent grain boundary cracking.
It is preferable to suppress it to about 02% or less.

Al: 0.01% or less Al is an element that forms inclusions such as oxides and inhibits preferential precipitation of Fe ₁₆ N _2. Therefore, it is preferable to suppress it to 0.01% or less.

N: 0.01% or less N is contained in the starting material as small as possible in order to produce crystal grains having a high [100] axis integration degree, and specifically, it is about 0.01% or less. preferable.

O: 0.02% or less O, like Al, forms inclusions such as oxides, and Fe ₁₆
Since it is also an element that inhibits preferential precipitation of N ₂ , it is preferable to suppress it to 0.02% or less.

As for other elements, the present invention is not hindered as long as the amount is small.

Next, the manufacturing method will be specifically described. Now, the molten steel adjusted to the desired composition is made into a slab by continuous casting, and then a hot rolled sheet is produced by a normal manufacturing process, that is, slab heating-rough rolling-hot rolling, and then rolled in a direction perpendicular to the hot rolling direction (C Direction rolling) or after cross rolling as described above, preferably by recrystallization annealing or repeating such rolling and annealing {1
Although crystal grains having a {00} plane orientation are developed, in order to obtain crystal grains that are strongly integrated on the [100] axis rather than on the {100} plane as in the present invention, the rolling / recrystallization treatment recovery / initial recrystallization treatment is performed. 20 to 200,000 in the same direction as the rolling direction at the crystallization stage
It is necessary to apply a magnetic field of about G.

Then, the crystal grains [10
[0] A thin plate having axes highly integrated in the rolling direction is subjected to nitriding treatment after surface polishing in a nitriding atmosphere at 100 to 700 ° C, more preferably while applying a magnetic field in the rolling direction of the thin plate. Fe ₁₆ N ₂ iron nitride is preferentially precipitated in the precipitation morphology shown in FIG. 1 (b). The cooling after the nitriding treatment is preferably a quenching treatment. After that, in order to take out only Fe ₁₆ N ₂ precipitated on the steel plate surface from the base steel surface,
Since Fe ₁₆ N ₂ is a metastable substance, the iron substrate may be removed using weak etching, for example, HNO ₃ solution of several% or a mixed solution of oxalic acid and H ₂ O ₂ .

[0026]

【Example】

[Table 2] Each of the hot-rolled sheets containing the above and having the balance of substantially Fe was cross-rolled to form a cold-rolled sheet having a thickness of 0.1 mm. Then, while applying a magnetic field of 500 G in the rolling direction, it was annealed at 880 ° C. to develop crystal grains strongly integrated on the [100] axis, and then the sample surface was polished to a mirror-finished state.
Then, in (NH ₃ + H ₂ ), applying a magnetic field of 1000 G in the rolling direction (a-1, b-1), and without applying a magnetic field (a-2, b-2).
After nitriding treatment at 460 ℃ for 20 minutes, several% of HNO ₃
Fe ₁₆ N ₂ was extracted in the liquid.

When the saturation magnetization of the Fe ₁₆ N ₂ thin film thus obtained was measured, the values shown in Table 3 were obtained. In addition, for comparison, the measurement results of those obtained by performing recovery / recrystallization without applying a magnetic field (a-3, b-3, a-4, b-4) are also shown.
It is also shown in Table 3.

[Table 3]

[0028]

As described above, according to the present invention, Fe ₁₆ N ₂ having extremely high saturation magnetization can be obtained easily and easily,
Therefore, the large-scale supply can be stably performed.

[Brief description of drawings]

FIG. 1 shows Fe ₁₆ N ₂ when a magnetic field is applied to the sample in a direction perpendicular to the sample (FIG. 1A), a parallel direction (FIG. 1B) and no magnetic field (FIG. 1C). It is the figure which compared and showed the precipitation state of.

Claims (2)

[Claims] 1. An iron or iron alloy thin plate having a texture in which [100] axes of crystal grains are strongly integrated in the rolling direction is subjected to a nitriding treatment to preferentially form Fe ₁₆ N ₂ on the surface of the thin plate. later, the manufacturing method of the Fe ₁₆ N ₂ iron nitride having a high saturation magnetization, wherein the iron or iron alloy is removed by etching retrieve the Fe ₁₆ N ₂ iron nitride. 2. An iron or iron alloy thin plate having a texture in which [100] axes of crystal grains are strongly integrated in the rolling direction, is subjected to a nitriding treatment while applying a magnetic field in the same direction as the rolling direction, After the Fe ₁₆ N ₂ was preferentially formed on the surface, of the Fe ₁₆ N ₂ iron nitride having a high saturation magnetization, wherein the taking out by removing the iron or iron alloy Fe ₁₆ N ₂ iron nitride by etching Production method.