Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1985-01-15
1987-10-27
Sheehan, John P.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148112, H01F 104
Patent
active
047027800
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a grain oriented silicon steel sheet aiming at the improvement of the surface properties and the magnetic characteristics of a high silicon steel containing not less than 3.1% by weight (hereinafter referred to briefly as "%" of Si).
BACKGROUND ART
As well known, the grain oriented electromagnetic steel sheet which is mainly used as an iron sheet for the transformers is required to have a high magnetic flux density represented by B.sub.10 value as the magnetization characteristics, a low iron loss represented by W.sub.17/50 value, and excellent surface properties of a product steel sheet. In order to enhance the magnetic characteristics of the grain oriented silicon steel sheet as mentioned above, it is necessary to highly arrange the <001> axis of the secondary recrystallized grains of the product in a rolling direction. There have been heretofore huge improvements for this purpose, and it has now become possible to industrially produce a gain oriented silicon steel sheet having B.sub.10 value of larger than 1.89 T (Tesla) and an iron loss of W.sub.17/50 value of not higher than 1.05 W/kg. However, recently from the standpoint of the energy saving, it has been strongly demanded to lower the electric power loss than as before with respect to the electric appliances such as the transformers, and accordingly with respect to the grain oriented silicon steel sheet as the iron core material of the transformer and the like, there has been also demanded the one having a further lower iron loss value. In addition, there has been demanded to reduce the surface defects such as surface flawns and form an excellent insulating film with respect to the surface properties of the product.
On the other hand, the ultimate aim to have Si contained in the grain oriented silicon steel sheet is to increase the electric resistance of the raw material and to thereby lower the eddy current loss, that is, to reduce the iron loss. Therefore, to increase the content of Si is extremely effective to reduce the iron loss value. However, the increase in the content of Si leads to the problem that the surface properties of the steel sheet is deteriorated. That is, in the case of the process of making the grain oriented silicon steel sheet by using the AlN precipitation phase as an inhibitor, the slab is generally required to be heated at a higher temperature than in the ordinary steel prior to hot rolling in order to dissociate and solid-solve MnS to be coexistent as an inhibitor with AlN. However, if the slab is heated at such a higher temperature, it is likely that hot tear is produced during the slab soaking or hot rolling to develop the surface defects on the product. Particularly, if the content of Si exceeds 3.0%, the surface properties of the product conspicuously degrades with the rapid deterioration of the hot processability. Therefore, it has been so far compulsory that the content of Si is restricted to not higher than 3.0% so as to obtain the product having excellent surface properties. Thus, it has been considered to be actually difficult to reduce the iron loss value by further increasing the content of Si.
DISCLOSURE OF THE INVENTION
Based on the above-mentioned present situation, it is an object of the present invention to provide a process for manufacturing a grain oriented silicon steel sheet being extremely excellent in the surface properties thereof and low in iron loss by exceedingly stable steps.
Noting that a silicon steel raw material containing as much as 3.1-4.5% of Si when AlN precipitation phase being utilized is a material which is intrinsically suitable for the production of a product with a high magnetic flux density and a low iron loss, the present inventors have strenuously made experiments and studies to find out solutions for diminishing the deterioration in the surface properties which is the defect in this case. Consequently, they have found that even when a high content of Si is contained, the grain oriented silicon steel sheet having the e
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patent: 4108694 (1978-08-01), Shiozaki et al.
patent: 4280856 (1981-07-01), Inokuti et al.
patent: 4469533 (1984-09-01), Inokuti et al.
Ikeda Shigeko
Inokuchi Yukio
Ito Yoh
Kawasaki Steel Corporation
Sheehan John P.
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