Metal treatment – Process of modifying or maintaining internal physical... – With casting or solidifying from melt
Patent
1992-10-02
1994-02-15
Dean, Richard O.
Metal treatment
Process of modifying or maintaining internal physical...
With casting or solidifying from melt
148541, 148546, 148551, 148552, 148554, 148556, 148557, 148111, 164476, 295277, C21D 812
Patent
active
052863158
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for preparing a rollable metal sheet from a quench solidified thin cast sheet as a starting material capable of providing a good rolled shape when rollable metal sheets including various alloy sheets, such as soft iron, stainless steel, silicon steel, nickel-iron (permalloy), cobalt-iron (permendur), nickel, aluminum and copper sheets are prepared from a quench solidified thin cast slab or cast thin strip (hereinafter generally referred to as "thin cast sheet") as a starting material.
BACKGROUND ART
Conventionally, various rollable metal sheets are produced by, for example, (i) a continuous casting to prepare a 200 mm-thick cast slab, (ii) heating the slab, (iii) hot rolling, (iv) annealing the hot rolled material, (v) cold rolling, and (vi) an optional heat treatment for working. Recent demands for a reduction in production costs have led to proposals of various methods of eliminating the above-described steps (ii) and (iii) including the single roll and twin roll methods, which comprise continuously feeding a molten metal onto a cooling material having one or two cooling surfaces being transferred and renewed for quench solidification, thereby preparing a thin cast sheet having a thickness of several ten .mu.m to about 10 mm. The above-described single and twin roll methods, etc., provide a rollable metal with a high productivity at a low cost but are plagued by several fundamental problems, and therefore, currently the technology in this field is incomplete, although some products have been put to practical use.
Among the above-mentioned problems, one of the most serious is a loss of the rolling property. In general, contrary to the smooth surface of a hot rolled sheet prepared by the conventional hot rolling process, the surface of a thin cast sheet prepared by the single roll method, twin roll method or the like often has an unevenness of as much as several ten % or more of the sheet thickness, due to rippling, and further, suffers from large variations in the thickness of the sheet in the width direction thereof.
This is a defect inherent to the quench solidifying system and is attributable to a localized difference in the shrinkage accompanying the solidification of the molten metal and a thermal deformation of the roll surface, etc., and can be avoided to some extent by attention to the design and operation of the machinery. This alleviation, however, is limited because, in a rollable metal sheet prepared by a series of production steps wherein a cold rolling or warm rolling step is essential, a ripple or the like on the surface of the metal is squeezed in the rolling direction during the rolling and causes a dimple to be formed in the direction of the sheet body; this is the cause of the occurrence of "scab". The above-described uneven portion also is often a cause of a cracking of a fragile material during cold rolling. In recent years, various methods have been proposed, including a method which comprises casting a soft iron sheet or a stainless steel sheet to a thickness of several ten .mu.m to several mm through a single or twin roll method, and annealing and cold rolling the sheet to prepare a foil strip having a thickness of several ten .mu.m to several hundred .mu.m. Nevertheless, in this method also, the uneven portion present in the thin cast sheet is a cause of contraction or breaking during the cold rolling. As described above, compared to the conventional hot rolling process, the single or twin roll method is an excellent production method having not only the merit of a reduction of costs, such as an elimination of steps and the need for less plant and equipment investment, but also having an advantage in that a cold rolled material having a thickness as small as about several ten .mu.m can be directly prepared. These methods, however, have not been put to practical use, due to problems with the rolling process.
In particular, when the above-described thin cast sheet is used as a starting material for stainless steel sheets
REFERENCES:
patent: 4799974 (1989-01-01), Mahoney et al.
patent: 4909859 (1990-03-01), Nazmy et al.
patent: 4969593 (1990-11-01), Kennedy et al.
European Search Report EP 90 90 5626.
"Seitestu Kenkyu (Study in Iron Manufacturing)" N 292 (1977), pp. 100-112 (with partial translation).
Iwanaga Isao
Iwayama Kenzo
Miyazawa Kenichi
Mizoguchi Toshiaki
Sumitomo Hidehiko
Dean Richard O.
Ip Sikyin
Nippon Steel Corporation
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