Metal founding – Means to shape metallic material – Continuous or semicontinuous casting
Reexamination Certificate
1998-12-28
2001-04-17
Pyon, Harold (Department: 1722)
Metal founding
Means to shape metallic material
Continuous or semicontinuous casting
C164S442000, C164S413000
Reexamination Certificate
active
06216769
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a process for guiding a strand in a continuous casting plant with a soft reduction zone in which hydraulic servo units continuously adjust the gap between oppositely located strand guide rollers, and to the corresponding strand guide for performing this process.
2. Description of the Prior Art
Continuous casting plants, especially continuous casting plants for steel, use rollers to guide the strand; these rollers limit the thickness of the strand which is not yet completely solidified and prevent bulging of the strand shell due to ferrostatic internal pressure.
Usually, groups of at least 4 pairs of rollers are combined in guide matter segments. The strand guide rollers arranged above the strand are fastened to a movable upper part, of the segment, while the strand guide rollers located below the strand are arranged at a fixed lower part, of the segment. The fixed part and movable part of the individual segment are connected with one another via 4 tension cylinders. These clamping cylinders, as they are called, pull the movable top part of the segment on spacers, so that the desired gap width results between the oppositely located rollers. This gap width of a segment of this type corresponds to the strand thickness.
A strand guide of the type mentioned above is known from DE 40 22 871 C2, wherein frame parts which carry the strand guide rollers that are located opposite to one another can be clamped relative to one another by means of a displacement device on one part of the segment until support devices contact counter-support devices which are provided with supporting surfaces located at different height positions and with counter-supporting surfaces, on the other part of the segment. The individual support disks are adjustable by means of rotation.
A device of this kind can only adjust a fixed gap width which cannot be readjusted during casting.
However, modern process technologies for improving product quality require that the gap width for a segment is changed during the casting process. In particular, soft reduction in the region of the lowest point of the liquid pool requires a wedge-shaped adjustment of the strand and a variable change in gap width of the corresponding segment.
A simple possibility for changing the gap width of segments with 4 clamping cylinders can be achieved in that the cylinders are constructed with position regulation as servo-hydraulic axles. In a solution of this type, the spacers, as they are called, can be dispensed with. The gap width of the segment is predetermined by a corresponding preset reference value for the 4 position-regulated piston-cylinder units. In so doing, the two servo units at the run-in end of the segment and the two servo units at the run-out end of the segment are regulated so as to be synchronized. Due to the use of a total of 4 servo units, this system is statically redundant.
DE 41 38 740 A1 discloses a process for the continuous casting of slabs or ingots in a continuous casting plant with a soft reduction zone which has rollers which can be continuously adjusted individually or as segments relative to one another by means of hydraulic cylinders and, with respect to their gap width, by means of spindles. The spindles can be moved to a desired gap spacing such that load is reduced. The movable part of the segment which is held in its position by four hydraulic cylinders is also statically redundant.
SUMMARY OF THE INVENTION
Therefore, it is the object of the invention to provide a process and a corresponding device for guiding a strand in a continuous casting plant in which the static redundancy brought about by the four-point support of the strand segment is eliminated and the tensioning of the movable parts of the segment brought about in this way is reduced.
This object is achieved by a process for guiding a strand having a soft reduction zone in a strand guiding segment of a continuous casting machine, the strand guiding segment having four servo piston cylinder units for adjusting a gap between oppositely arranged guide rollers of the strand guiding segment. In the process, two adjacent ones of the four servo piston-cylinder units are hydraulically linked and adjusted to the strand as a unit and the remaining servo piston-cylinder units are independently adjusted to the strand. The objects of the invention are also met by a strand guide for use in a continuous casting plant including a strand guide segment having oppositely arranged strand guide rollers defining a gap through which the strand is guidable. The strand guide segment includes four servo piston-cylinder units operatively connected for continuously adjusting the gap, wherein two of the servo piston-cylinder units are adjustable as a unit by a shared servo valve and the other of the four servo piston-cylinder units are independently adjustable by separate servo valves.
The subclaims indicate advantageous further developments of the invention.
According to the invention, in a strand guiding segment with 4 servo units, two adjacent servo units are linked with one another hydraulically and the rest of the servo units remain independently adjustable. As a result of the parallel connection of two cylinders to form a unit corresponding to communicating pipes with only one position regulator, the plane maintained by four cylinders is statically determinate and is transformed into three-point support.
The pair of cylinders connected with only one servo valve has one position transmitter per cylinder. A mean value is taken from the signals of the individual position transmitters of the servo piston-cylinder units which are combined with one another and this means value is supplied, as a position adjustment value, to the shared position regulator acting on both cylinders.
In an advantageous construction, the servo piston-cylinder units of the run-in or run-out of the strand guide segments are linked with one another. Each of the strand guide segments for a strand guide is preferably linked in the same way as the others; for example, all servo units connected at the run-in end are connected to a position regulator and all servo units connected at the run-out end are driven independently.
When a defined path value, for example, a distance that can be predetermined, is exceeded when determining the average value or other technical data pertaining to continuous casting, another pair of servo piston-cylinder units can be linked with one another.
REFERENCES:
patent: 5018569 (1991-05-01), Burau et al.
patent: 5709261 (1998-01-01), Streubel
Blask Rüdiger
Schwedmann Johannes
Wetter Jakob
Cohen & Pontani, Lieberman & Pavane
Lin I-H
Mannesmann AG
Pyon Harold
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