JPH09134813A - Flat fe-based alloy powder of high saturation magnetization for magnetic shield - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain magnetic shield powder of high saturation magnetization by a method wherein composition composed of boron, chrome, niobium, iron, and unavoidable impurities which are prescribed in composition ratio and each have a body-centered cubic crystal structure shown by X-ray diffraction is used. SOLUTION: An Fe-based alloy melt composed of 5 to 15% of B(boron), 2 to 8% of Cr(chrome), 2 to 12% of Nb(niobium), residual % of Fe(iron) and unavoidable impurities is turned into powder through a water atomizing method without using a quench roll method. By this setup, powder of body-centered cubic crystal structure shown by X-ray diffraction can be obtained. Powder below 50μm in diameter is selected out of the above material powder by classification, flattened by an attritor, subjected to a thermal treatment at a temperature of 350 to 750 deg.C for a prescribed time in an Ar atmosphere, and finally classified and controlled in size to have such a size distribution that a ratio of particle D50 to particle d is 20 to 500:1, wherein d denotes O. 02 to 0.6μm, and D50 is 3 to 60μm. The flattened Fe-based alloy powder is above 130emu/g in saturation magnetization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention exhibits high saturation magnetization, and therefore, when used in a magnetic shield, enables further improvement of magnetic shield performance and thinning of the magnetic shield layer and the magnetic shield sheet. Flat F
The present invention relates to an e-based alloy powder.

[0002]

2. Description of the Related Art Generally, various flat Fe-based alloy powders are used for forming magnetic shield layers, magnetic shield sheets, etc. for protecting various magnetic recording devices and electronic devices from the adverse effects of magnetic fields and electromagnetic waves. There is. Further, as a flat Fe-based alloy powder for magnetic shield, it is disclosed in Japanese Patent Application Laid-Open No. 4-4800.
As described in Japanese Patent Laid-Open No. 3 (1993), in atomic% (hereinafter,% means atomic%), B + Si: 18 to 33%, Cr + Nb: 2
.About.12%, Fe and unavoidable impurities: the rest, a Fe-based alloy having a composition consisting of: is melted, an amorphous strip (amorphous ribbon) is formed from this melt by a quenching roll method, and this is coarsely crushed, After classifying to a particle size of 50 μm or less, it is flattened with an attritor, and the flattened Fe-based alloy powder is subjected to a heat treatment at a temperature of 350 to 750 ° C. for a predetermined time in an Ar atmosphere, classified, and then averaged. Thickness (below,
“Indicated by“ d ”): 0.02 to 0.6 μm, totaling 5 from the smaller particle size determined by the viscosity distribution meter
Particle size at 0% (hereinafter referred to as "D ₅₀ "): 3
-60 μm, aspect ratio (D ₅₀ / d): 20-50
A flat Fe-based alloy powder produced by adjusting the grain size to 0 is known.

[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, B: 5 to 15%,
Cr: 2 to 8%, Nb: 2 to 12% are contained, and the balance is specified to a composition consisting of Fe and unavoidable impurities, and then this Fe-based alloy melt is subjected to a water atomizing method without using a quenching roll method. When powdered by X-ray diffraction, body-centered cubic by X-ray diffraction (hereinafter,
A powder having a (BCC) type crystal structure is obtained, and the powder is used as a raw material, and is classified and flattened by a conventional method.
After heat treatment and classification, that is, from the above-mentioned raw material powder, particles having a particle size of 50 μm or less are taken out by classification and flattened with an attritor, and then 350 to 7 in Ar atmosphere.
By subjecting to a heat treatment at a temperature of 50 ° C. for a predetermined time and finally classifying, and adjusting the particle size to d: 0.02 to 0.6 μm D ₅₀ : 3 to 60 μm D ₅₀ / d: 20 to ₅₀₀ The flattened Fe-based alloy powder produced has a research result that shows a high saturation magnetization of 130 emu / g or more.

The present invention has been made based on the above-mentioned research results, and the flat Fe-based alloy powder for magnetic shield showing high saturation magnetization is B: 5 to 15%,
It is characterized in that it contains Cr: 2 to 8%, Nb: 2 to 12%, the rest is composed of Fe and unavoidable impurities, and exhibits 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) BB has a function of suppressing the coercive force and improving the saturation magnetization, but if its content is less than 5%, a desired high saturation magnetization cannot be secured, and the coercive force is On the other hand, if the content exceeds 15%, the saturation magnetization tends to decrease.
%, Preferably 8 to 13%.

(B) Cr Cr has an action of improving the corrosion resistance and thus preventing the formation of rust and discoloration, but if the content of Cr is less than 2%, the desired corrosion resistance cannot be ensured. Its content is 8
%, The saturation magnetization decreases, and the desired excellent magnetic shield performance cannot be ensured. Therefore, the content is set to 2 to 8%, preferably 4 to 7%.

(C) Nb Nb has an effect of increasing the saturation magnetization and thus improving the magnetic shield performance, but if its content is less than 2%, the desired effect of the above effect cannot be obtained. If the content exceeds 12%, the saturation magnetization will suddenly decrease. Therefore, the content is 2 to 12%, preferably 4 to 8%.
%.

[0009]

Next, the flat Fe-based alloy powder of the present invention will be specifically described with reference to examples. Fe-B alloys, Fe-Nb alloys, Fe-Cr alloys, and electrolytic iron were used to prepare Fe-based alloy melts having the component compositions shown in Table 1 in a high-frequency induction furnace, and the melts were water atomized. Powdered by the method and classified to obtain a powder having a particle size of 50 μm or less, flattened by an attritor, and then subjected to a heat treatment for 2 hours at a predetermined temperature in the range of 350 to 750 ° C. in an Ar atmosphere, The flattened Fe-based alloy powder of the present invention (hereinafter referred to as the powder of the present invention) is obtained by conducting a classification treatment and adjusting to the degree shown in Table 1.
1-9 were manufactured respectively. For comparison purposes, Table 2
As shown in, the width is 15mm from the molten metal by the quenching roll method.
× Thickness: Under the same conditions except that a strip having a dimension of 0.015 mm is formed and crushed by a disc mill in an Ar atmosphere, that is, the subsequent steps of classification, flattening, heat treatment, and Comparative flatness F under the condition that classification is the same corresponding to each component composition of the powders 1 to 9 of the present invention
The e-based alloy powders 1 to 9 were manufactured.

Then, the powders of the present invention 1
9 and Comparative Powders 1 to 9 were observed for their crystal structures by X-ray diffraction.
Type ”diffraction pattern, and the latter are all“ BCC
It did not show a "type" diffraction pattern. The coercive force and saturation magnetization of these powders were measured, and the measurement results are also shown in Tables 1 and 2.

[0011]

[Table 1]

[0012]

[Table 2]

[0013]

EFFECTS OF THE INVENTION From the results shown in Tables 1 and 2, the powders 1 to 9 of the present invention having a BCC type crystal structure are all compared with the comparative powders 1 to 9 having a different crystal structure from the "BCC type". It is clear that it shows a much higher saturation magnetization without an increase in coercive force. As described above, the flat Fe-based alloy powder of the present invention exhibits a 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 the further improvement of the magnetic shield performance, but also has industrially useful properties such as making it possible to reduce the thickness of the magnetic shield layer and the magnetic shield sheet.

 ─────────────────────────────────────────────────── ─── 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. Atomic%, B: 5 to 15%, Cr: 2 to 8%, Nb: 2 to 12%, and the balance of Fe and inevitable impurities, and X-ray Flat Fe for magnetic shield showing high saturation magnetization characterized by showing a body-centered cubic crystal structure by diffraction
Base alloy powder.