Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1992-02-20
1994-05-03
Sheehan, John P.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148111, 148308, H01F 104
Patent
active
053084110
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a grain-oriented electrical steel sheet having a high silicon content and a process for producing the same, and particularly to a soft magnetic material having a Si content of 5 to 7.1% and exceptional magnetic properties unattainable in the prior art and a process for producing the same.
2. Background Art
A grain-oriented electrical steel sheet comprises a crystal grain having a {110} plane in the steel sheet plane and <001> in the direction of rolling, that is, the so-called Goss orientation (expressed as a {110 } <001> orientation in the Miller indices), and is used as a soft magnetic material in an iron core for transformers and large size rotating machines such as a generator. This steel sheet should have good magnetizing and iron loss properties with respect to the magnetic properties. Whether the magnetizing property is good or bad is determined by the height of the magnetic flux density induced within an iron core under an applied given magnetic force. An increase in the magnetic flux density of a soft magnetic material (a grain-oriented electrical steel sheet) can be attained by controlling the orientation of the crystal grain of the steel sheet into {110 } <001> orientation to a high degree.
The iron loss is a power loss consumed as heat energy when a predetermined alternating current magnetic field is applied to an iron core. The iron loss property of the grain-oriented electrical steel sheet is influenced by the magnetic flux density, sheet thickness, amount of impurities, specific resistance, size of crystal grain, etc. The grain-oriented electrical steel sheet having a high magnetic flux density (usually expressed in terms of B.sub.8 value) enables the size of electrical equipment to be reduced and exhibits a low (good) iron loss, so that an effort has been made in the art to enhance the magnetic flux density of the grain-oriented electrical steel sheet.
The grain-oriented electrical steel sheet is produced through the so-called "secondary recrystallization" wherein a steel sheet subjected to a proper combination of hot rolling, cold rolling and annealing to have a final thickness is subjected to finish annealing at a high temperature to selectively grow a primary recrystallized grain having a {110 } <001> orientation.
The secondary recrystallization is attained when the following requirements are satisfied.
a) Fine precipitates, for example, MnS, AIN and MnSe, or intergranular elements, such as Sn, Sb and P, are present in a steel sheet before secondary recrystallization (these substances are called an "inhibitor").
b) The primary recrystallized grain structure is a proper one, which means, the crystal grains are homogeneous and the texture is one wherein a grain having a {110 } <001> orientation easily grows.
In the above-mentioned process for producing a grain-oriented electrical steel sheet, a technique which enables a product having a particularly high magnetic flux density to be produced is disclosed in Japanese Examined Patent Publication (Kokoku) No. 40-15644 by Taguchi and Sakakura. This technique is characterized in that AIN precipitated in a .alpha..fwdarw..gamma. transformation is utilized as an inhibitor and this AIN precipitate is further used to control a primary recrystallized structure after strong cold rolling. A production technique established by modifying the above-described technique is disclosed in Japanese Examined Patent Publication (Kokoku) No. 54-13846. This modified technique includes the step of holding the steel sheet at a temperature in the range of from 50.degree. to 350.degree. C. in a period between passes in the cold rolling.
The technique disclosed in Japanese Examined Patent Publication (Kokoku) No. 40-15644 has the following problem. When the Si content is increased for the purpose of lowering the iron loss of the product, as described in Japanese Examined Patent Publication (Kokoku) No. 61-60896, a linear recrystallized grain defect occurs in the product, so th
REFERENCES:
patent: 5082509 (1992-01-01), Ushigami et al.
Data Base WPIL, Week 9048, Derwent Publications Ltd., GB, AN 90-358380.
European Search Report, EP 91 91 1311.
J. Appl. Phys. vol. 64, No. 10 (1988) pp. 5367-5369 "Commercial Scale Production of Fe-6.5 wt % Si Sheet", Y. Takada et al.
International Search Report PCT/JP91/00829.
Honma Hodaka
Suga Yozo
Takahashi Nobuyuki
Ushigami Yoshiyuki
Nippon Steel Corporation
Sheehan John P.
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