Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1998-09-28
2000-07-25
Batten, Jr., J. Reed
Metal founding
Process
Shaping liquid metal against a forming surface
164417, B21B 146, B21B 1322, B22D 1112
Patent
active
060925868
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and an arrangement for producing hot-rolled steel strip from continuously cast semi-finished steel in directly successive work steps.
2. Description of the Prior Art
Steel strip is produced by the deformation of, for example, a cast semi-finished steel, whose weight depends on the coil weight of the finished product, to the desired geometric dimensions in one or more rolling processes. The casting and deformation processes usually occur discontinuously not successively. However, such sequential processes entail long processing times, expensive rolling devices and significant energy losses during processing. Moreover, the discontinuous operation results in output and quality losses.
A number of completely continuous cast-rolling arrangements are mentioned in the literature. However, it is always noted that these configurations are not practically applicable, because the final rolling temperatures needed to establish the desired hot-strip properties cannot be reached with such machines. Due to their low casting speed, the strip would cool so quickly that operation without intermediate heating would be impossible, while operation with the required expensive heating units would not be economical.
An arrangement and a process for the continuous production of strip steel or sheet steel from continuously cast flat products is known from WO-A-89/11363. In this prior art arrangement and process, a continuously cast thin slab, after reduction in a first roll pass, is subjected to induction heating and, directly thereafter, is rolled in a multi-stand finishing train into a strip, which is coiled up at the end of the finishing train. This known solution does not disclose details of temperature control with the goal of always ensuring that the finish-rolling of the strip occurs in the austenitic temperature range.
In producing hot strip, the strict restriction that products be finish-rolled in the austenitic range (.gtoreq.880.degree. C.) makes the selection of suitable casting parameters especially important. Casting thickness and casting speed play an important role, because they determine the temperature control throughout the entire arrangement during operation.
SUMMARY OF THE INVENTION
The object of the invention is to create a process and an arrangement for producing hot strip from continuously cast semi-finished steel, wherein the hot strip is rolled into a finished product directly from the melt in a continuous, endless process and finish-rolling is carried out in the austenitic temperature range. Further, process heat from the casting process is to be used in producing the hot strip, so that the process and arrangement operate more economically than conventional discontinuous processes and arrangements.
This object is attained in a process for producing hot-rolled steel strip from continuously cast semi-finished steel in directly successive work steps, in which the semi-finished steel produced by a continuous casting machine is fed directly from the continuous casting machine to a continuous hot rolling mill, without prior separation, and an endless thin steel strip is produced at the final rolling temperatures usual in process technology directly from the primary heat, using the following parameters: machine h.sub.o [m] and the casting speed v.sub.c [m/min] fulfill the relation: whereby it holds that: centimeters (cm).
The strictest restriction in hot-strip production, i.e., the requirement that products be finish-rolled in the austenitic range, can be overcome by a suitable selection of casting parameters (casting thickness h.sub.o and casting speed v.sub.c). It has been found that when the product of the slab thickness [m] and the casting speed [m/min] exceeds 0.487 m.sup.2 /min, it is possible to achieve a successful production process for hot strip with finish-rolling in the austenitic range if, at the same time, the number of deformation steps n in the rolling mill conforms to the formula (m=0.51+3.29 lg.sub.10 (h
REFERENCES:
patent: 4793401 (1988-12-01), Matsuoka et al.
patent: 5113678 (1992-05-01), Mannaka et al.
patent: 5634257 (1997-06-01), Kajiwara et al.
Batten, Jr. J. Reed
Mannesmann AG
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