Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1995-11-21
1996-12-17
Lin, Kuang Y.
Metal founding
Process
Shaping liquid metal against a forming surface
164476, B22D 1122
Patent
active
055843379
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for producing a thin cast strip of carbon steel by a continuous casting machine in which the mold walls are moved in synchronization with the cast strip, and particularly relates to the process wherein the properties of scale formed on the cast strip are controlled
BACKGROUND OF THE INVENTION
A twin drum continuous casting machine, for example, is known as a continuous casting machine in which the mold walls are moved in synchronization with the cast strip. The machine is an apparatus for casting a thin cast strip, wherein a pouring basin of molten steel is formed by a pair of cooling drums each rotating in a direction opposite to that of the other drum and a pair of side gates applied to the respective ends of a pair of the cooling drums by pushing, a molten steel is supplied to the pouring basin, the molten steel is cooled and solidified along the peripheral surface of the cooling drums to form solidified shells, and the solidified shells are united in the gap between the cooling drums.
When a carbon steel containing up to 5% of C is cast into a thin cast strip having a thickness up to 10 mm by such a continuous casting machine, a thick scale containing FeO as its main component is formed on the cast strip surface. When a cast strip on which such a scale is formed is pickled, a rough surface appears. When such a cast strip is cold rolled, defects such as scab are formed on the cold rolled steel sheet, and the surface properties of the products are markedly impaired. Moreover, when the cast strip on which such a scale is formed is press worked or bent, there arises a problem that the scale is peeled off to impair the surface properties of the products.
There has heretofore been known a method as, for example, disclosed in Japanese Unexamined patent publication (Kokai) No. 59-199152, for completely inhibiting scale formation on a cast strip in twin drum type continuous casting, which method comprises transferring a cast strip sent from cooling drums along rolls in an inert atmosphere in a seal chamber, which is provided so that it surrounds the casting machine, to cool the strip to a temperature of up to 150.degree. C.
However, since the casting rate of the twin drum continuous casting machine is as fast as about 80 m/min, holding the cast strip in an inert atmosphere until the strip temperature becomes up to 150.degree. C. causes problems that a long and large cooling apparatus is required, that the productivity becomes poor, and that a large amount of inert gas is consumed.
DISCLOSURE OF THE INVENTION
The present invention is intended to make the scale formed on a cast strip thin in continuous casting a thin carbon steel strip, and also make the composition of the scale suited to working such as cold rolling and pressing after continuous casting.
Furthermore, the present invention is intended to simplify an apparatus for inhibiting the formation of scale on a cast strip, reduce the consumption of the inert gas and efficiently produce cast strips.
As described below is the subject matter of the process for producing a thin cast strip of the present invention which process solves the problems as mentioned above.
(1) In a process for producing a thin cast strip wherein a carbon steel comprising up to 0.5% of C and less than 0.1% of Cr or Cu is cast into a thin cast strip having a thickness up to 10 mm by a continuous casting machine having mold walls which move in synchronization with the cast strip, and the thin cast strip is coiled in a coil form by a coiler, a process for producing a thin cast strip with a reduced surface scale which comprises the steps of holding the thin cast strip, subsequently to casting into the strip, in an atmosphere comprising up to 5.0% of oxygen and the balance an inert gas through a temperature region to up to 1,200.degree. C., then cooling the cast strip at a rate of at least 10.degree. C./sec through a temperature region to 800.degree. to 750.degree. C., and coiling the cast strip in a coil form by the
Akamatsu Satoshi
Fukuda Yoshimori
Matsumura Yoshikazu
Miyazaki Masafumi
Nakashima Hiroyuki
Lin Kuang Y.
Nippon Steel Corporation
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