JPH09137260A - Flat iron base alloy powder for magnetic shield showing high saturation magnetization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the thinning of a magnetic shield layer or the like in alloy powder by forming the components of the alloy powder of specified atomic % of Al, Si, Cr, Cu, and the balance Te and allowing it to show a body-centered cubic type crystal structure. SOLUTION: The components of an Fe base alloy are formed of, by atom, 15 to 30% of one or two kinds of Al and Si, 2 to 6% Cr, 1 to 6% Cu, and the balance Fe with inevitable impurities. At the time of powdering the molten metal of the above Fe base alloy by a water atomizing method, powder showing a body-centered cubic type crystal structure by X-ray diffraction can be obtd. This powder is subjected to classifying, flattening, heat treatment and classifying, i.e., the grain size of the water atomizing powder is regulated to <=50μm by the classifying, and this powder is flattened by an attoritor. Thus, a contribution to the more improvement of its magnetic shield capacity can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat Fe-based alloy powder used for forming a magnetic shield layer or a magnetic shield sheet for protecting various magnetic recording devices and electronic devices from the adverse effects of magnetic fields and electromagnetic waves. It is about.

[0002]

2. Description of the Related Art Conventionally, as a flat Fe-based alloy powder for magnetic shield, as described in, for example, Japanese Patent Application Laid-Open No. 3-295206, in atomic% (hereinafter,% means atomic%), Al and Si. One or two of the above: 15 to 15
30%, Cr: 2 to 6%, with the balance being Fe and inevitable impurities, and having a body-centered cubic (hereinafter referred to as "BCC") type crystal structure by X-ray diffraction It has been known. Further, the above-mentioned flat F for the conventional magnetic shield
In practical use, an e-based alloy powder and many others have an average thickness (hereinafter referred to as “d”): 0.02 to 0.6 μm.
m, the particle size when the cumulative weight reaches 50% from the smaller particle size determined by the particle size distribution meter (hereinafter,
It is well known that the particle size is adjusted to “D ₅₀ ”): 3 to 60 μm and the aspect ratio (D ₅₀ / d): 20 to ₅₀₀ .

[0003]

On the other hand, in recent years, it has been remarkable that magnetic recording devices and electronic equipment have become multifunctional, compact, and have a high output. Accordingly, magnetic shielding performance has been further improved, and magnetic shielding has been further improved. There is a tendency to require thinner layers and magnetic shield sheets.
Development of a magnetic shield powder showing higher saturation magnetization is desired.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoint, as a result of paying attention to the above-mentioned conventional flat Fe-based alloy powder for magnetic shield and conducting research to improve the saturation magnetization thereof, Al and / or Si: 15 to 30%, Cr : 2 to 6%, Cu: 1 to 6%, the rest is Fe and unavoidable impurities, and the Fe-based alloy melt is pulverized by a water atomizing method. A powder exhibiting a BCC type crystal structure was obtained with, and the powder was classified under normal conditions,
Flattening, heat treatment, and classifying, that is, the water atomized powder is classified to have a particle size of 50 μm or less, and flattened by an attritor, and then in an Ar atmosphere,
A heat treatment is performed at a temperature of 350 to 750 ° C. for a predetermined time, and then classification is performed to obtain d: 0.02 to 0.6 μm, D ₅₀ : 3 to 60 μm, D ₅₀ / d: 20 to 500. The research results show that the flat Fe-based alloy powder produced by adjusting the grain size exhibits a high saturation magnetization of 130 emu / g or more.

The present invention has been made based on the above research results, and contains Al and / or Si: 15 to 30%, Cr: 2 to 6%, Cu: 1 to 6%, It is characterized by flattened Fe-based alloy powder for magnetic shield having the composition of the balance of Fe and unavoidable impurities, and exhibiting a BCC type crystal structure by X-ray diffraction.

Next, the reason why the composition of the flat Fe-based alloy powder of the present invention is limited as described above will be explained. (A) Al and Si These components have the effect of improving the saturation magnetization, but if the content is less than 15%, the desired high saturation magnetization cannot be obtained, but rather the coercive force becomes high, which is excellent. The magnetic shield performance cannot be ensured, and on the other hand, when the content exceeds 30%, the saturation magnetization is rapidly reduced. Therefore, the content is 15 to 30%, preferably 20%.
２５25%.

(B) Cr Cr has an action of improving the corrosion resistance and thus preventing the formation of rust and discoloration, but if its content is less than 2%, the desired excellent corrosion resistance cannot be ensured. On the other hand, when the content exceeds 6%, the saturation magnetization is reduced, and the deterioration of the magnetic shield performance is unavoidable.
6%, preferably 3-5%.

(C) Cu Cu has an action of increasing the saturation magnetization in a state in which the increase of the coercive force is remarkably suppressed, but if the content thereof is less than 1%, the desired saturation magnetization improving effect cannot be obtained. Its content is 6
%, The coercive force will increase and the magnetic shield performance will inevitably decrease.
-6%, preferably 2-4%.

[0009]

Next, the flat Fe-based alloy powder of the present invention will be specifically described with reference to examples. High purity A
Fe, Fe-Si alloy, Fe-Cr alloy, electrolytic copper, and electrolytic iron were used to prepare Fe-based alloy melts having the component compositions shown in Tables 1 to 3 in a high-frequency induction furnace. Powderized by water atomization method, classified and 50μ
A powder having a particle size of m or less was made flat, then flattened by an attritor, and then heat-treated for 2 hours in Ar atmosphere at a predetermined temperature within the range of 350 to 750 ° C. 1 to 22 of the present flattened Fe-based alloy powders (hereinafter referred to as the present invention powders) which show a BCC crystal structure by X-ray diffraction by adjusting the grain sizes shown in 1 to 3 and Cu as an alloy component No Comparative flat Fe-based alloy powder (hereinafter referred to as comparative powder) 1
~ 11 were produced respectively. The coercive force and the saturation magnetization of the powders 1 to 22 of the present invention and the comparative powders 1 to 11 thus obtained were measured, and the measurement results are shown in Tables 1 to 3.

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

[Table 3]

[0013]

From the results shown in Tables 1 to 3, the powders 1 to 22 of the present invention show substantially higher coercive force and higher saturation magnetization than the comparative powders 1 to 11 containing no Cu. It is clear. As described above, the flat Fe-based alloy powder of the present invention exhibits high saturation magnetization without an increase in coercive force, and therefore, when it is used as a magnetic shield, it exhibits excellent magnetic shield performance, Therefore, it not only contributes to further improvement of the magnetic shield performance,
It has industrially useful properties such as enabling thinning of magnetic shield layers and magnetic shield sheets.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuaki Yoshioka 1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd. (72) Inventor Atsushi Umezawa 1-chome, Ichigaya-Kagacho, Shinjuku-ku, Tokyo No. 1 in Dai Nippon Printing Co., Ltd. (72) Koichi Ishiyama 1-297 Kitabukuro-cho, Omiya-shi, Saitama Inside Mitsubishi Materials Co., Ltd. Research Institute (72) Kiichi Komada 1-297 Kitabukuro-cho, Omiya-shi, Saitama Mitsubishi Materials Co., Ltd.

Claims (1)

[Claims] 1. In atomic%, one or two of Al and Si: 15 to 30
%, Cr: 2 to 6%, Cu: 1 to 6%, the rest of which has a composition of Fe and inevitable impurities, and exhibits a body-centered cubic crystal structure by X-ray diffraction. Flat Fe for magnetic shield showing high saturation magnetization
Base alloy powder.