Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1987-01-30
1988-09-27
Sheehan, John P.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
H01F 104
Patent
active
047739487
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an improvement of a method of producing high silicon iron sheet of more than 4wt % Si having excellent soft magnetic properties by hot rolling and cold rolling processes.
BACKGROUND TECHNIQUE
Silicon iron alloys have excellent soft magnetic properties, and have been much used as magnetic cores of electric transformers or material for other electric devices. It is known that the more Si content, the more improved are the soft magnetic properties, and these properties show peaks at around 6.5 wt %. However, if Si content were more than 4.0 wt %, an elongation would be rapidly decreased, and ordinary cold rolling could not be practiced. Therefore it has been regarded as impossible to industrially produce sheet containing Si of more than 4 wt %.
This invention has been developed in view of such circumstances, and is to provide a method of effectively producing high silicon iron sheets of more than 4 wt % Si via the rolling processes.
DISCLOSURE OF THE INVENTION
In the invention, a molten Fe alloy is produced, which comprises Si: 4.0 to 7.0 wt %, Mn: not more than 0.5 wt %, P: not more than 0.1 wt %, S: not more than 0.02 wt % and Al: not more than 2 wt %. The produced alloy is made an ingot or slab by a continuous casting, subjected to a slabbing-roughing, or a roughing at a temperature of more than 1000.degree. C. and at total reduction of more than 50%, performed thereon with hot finish rolling under conditions specified as follows, and coiled at a temperature of not more than 750.degree. C. The oxide scale of the hot rolled strip or plate is removed by pickling or grinding, and after trimming if required, entered to a cold rolling. The cold roller strip or sheet is subjected to an annealing for improving the magnetic properties. The annealing is done at a temperature of the cold rolled strip or sheet being more than 800.degree. C.
The most noted thing in the invention is said hot finish rolling at a temperature of not more than 1100.degree. C. and the total reduction R(%), and the coiling at not more than 750.degree. C.
The total reduction R(%) is defined as follows.
Assuming that d(mm) is an average grain diameter before the hot finish rolling, and when .lambda..sub.0 is given by a following equation of d.ltoreq..lambda..sub.0, R(%).gtoreq.0.
Herein, if R(%)=0, the hot finish rolling is not of course carried out, and this invention also includes such a case.
The invention will be explained in detail.
The inventors made many experimental studies on an improvement of cold workability with respect to the above mentioned high silicon iron alloys, and found that if selecting the hot finish rolling conditions in response to a microstructure before the hot finish rolling, a hot rolled plate having excellent cold workability might be produced, and that the cold workability of silicon iron alloys was regulated by a microstructural parameter of the hot rolled plate.
FIG. 1 shows the cold workability of 6.5% silicon iron alloy, in which lateral and vertical axes indicate the average grain diameter d(mm) before hot finish rolling and the total reduction R(%) of the hot finish rolling respectively.
The figure was obtained by investigating the samples with various average grain diameter, which were prepared from the 50 kg ingots. The samples were soaked at a temperature of 1000.degree. C., and hot-rolled by 6 passes to each amount of the total reduction. The finish temperature was 650.degree..+-.10.degree. C.
In the figure, O indicates that no edge cracks generated when the hot-rolled plates were cold-rolled at the total reduction of 85%, in other words, the cold workability was preferable. X indicates that the cracks were generated at the beginning of said cold rolling and further rolling was impossible.
From this figure, it is obvious that when the average grain diameter d(mm) before the hot finish rolling is large, large hot rolling reduction is necessary to undertake the cold rolling (for example, when the average grain diameter is 3 mm, the total hot rolling r
REFERENCES:
patent: 4592789 (1986-06-01), Kawamo et al.
patent: 4615750 (1986-10-01), Mochinaga et al.
Hiura Akira
Inagaki Jun-ichi
Nakaoka Kazuhide
Takada Yoshikazu
Nields Henry C.
Nippon Kokan Kabushiki Kaisha
Sheehan John P.
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