Metal founding – Process – With measuring – testing – inspecting – or condition determination
Patent
1997-04-21
1998-11-10
Lin, Kuang Y.
Metal founding
Process
With measuring, testing, inspecting, or condition determination
164477, 164417, 295277, B22D 1112, B21B 104
Patent
active
058329854
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a process for producing a steel strip with the properties of a cold-rolled product, as well as to a machine for implementing this process.
From EP 0 541 574 B1 a generic process is known in which finished strip with the properties of a cold-rolled product is produced in a hot-rolling train directly from feedstock that was cast close to final size. In this process, a thin continuous slab with a maximum thickness of 100 mm is produced in a continuous casting machine. The cast strip, which has a liquid core, is then rolled to solidification thickness (cast rolling) on a rolling device located directly behind the continuous casting mold. After this, the thin slab is descaled and hot-rolled at temperatures above 1100.degree. C. to a thickness of 10-30 mm on a rolling device with, for example, three stands. The intermediate strip hot-rolled in this manner is divided into partial lengths by means of strip shears. Preferably, these partial lengths are wound into coils and later unwound for further hot rolling and, as needed, further descaling. Prior to being hot rolled again, and preferably before being wound into coils, the strip-type material is reheated inductively to a hot-rolling temperature above 1100.degree. C. The second hot-rolling process is carried out at a temperature above Ar.sub.3. Immediately after this, the strip is cooled to a temperature below Ar.sub.3, preferably a temperature in the range of 600.degree. to 250.degree. C. The strip produced in this manner is subsequently finish-rolled by being cold rolled on one or more sequential stands and then wound into coils.
The known process is intended to produce cold-rolled strip while expending as little energy as possible. For this purpose, the methods of casting close to final size (thin slab production) and cast-rolling are used, i.e., thickness reduction is carried out while the hot cast strip still has a partly liquid core. Furthermore, hot rolling is carried out, in part, using the heat left over from the continuous casting process. It is disadvantageous that, despite the utilization of heat from the continuous casting, the strip-type intermediate product must be heated inductively for the second portion of hot rolling.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a process, as well as a machine for its implementation, which avoids separate reheating of the strip-type intermediate product and the energy and equipment expense associated therewith. In addition, the properties of the produced material are to be improved to the greatest extent possible in the direction of cold-rolled properties.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a process for producing a steel strip with the properties of a cold-rolled product, by carrying out the following sequential steps: a) producing a thin slab 30 to 100 mm thick from a steel melt by continuous casting in a continuous casting machine, and after a cast strip emerges from a mold of the continuous casting machine, cast rolling the a cast strip with a liquid core to reduce the thickness of the cast strip by at least 10%; b) descaling the thin slab produced according to step a); c) hot rolling the descaled thin slab at temperatures in a range of 1,150.degree. to 900.degree. C. for reducing thickness by at least 50% to produce an intermediate strip with a maximum thickness of 20 mm; d) after hot rolling, accelerated cooling of the intermediate strip to a temperature in a range of 850.degree. to 600.degree. C.; e) rolling down the cooled intermediate strip by isothermic rolling at 850.degree. to 600.degree. C. on a finishing train with at least three stands into strips with a maximum thickness of 2 mm, whereby the strip thickness is reduced by at least 25% per roll pass; and f) subsequently cooling the isothermic rolled steel strip in accelerated fashion to a temperature no greater than 100.degree. C.
In another embodiment
REFERENCES:
patent: 5329688 (1994-07-01), Arvedi et al.
Bleck Wolfgang
Pleschiutschnigg Fritz-Peter
Splinter Paul
von Hagen Ingo
Lin Kuang Y.
Mannesmann Aktiengesellschaft
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