Metal founding – Means to shape metallic material – Continuous or semicontinuous casting
Reexamination Certificate
1999-05-26
2001-12-11
Dunn, Tom (Department: 1725)
Metal founding
Means to shape metallic material
Continuous or semicontinuous casting
C164S448000
Reexamination Certificate
active
06328093
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a strand guiding segment for slab casting plants with a guiding width for the cast strand which is adjustable between guide rollers of a frame on a fixed side and a frame on a detachable or loose side, wherein the frames interact with adjusting means for overcoming the ferrostatic pressure and for adjusting the desired sectional width of the strand.
2. Description of the Related Art
The configuration of the strand guiding segments and the base frames is an essential factor for the competitiveness in the field of continuous casting plants. The strand guiding segments and the base frames must meet the operational requirements in an optimum manner, on the one hand, and, on the other hand, they must be competitive with respect to cost, particularly because, depending on the requirements, the portion of the costs of the strand guidance constitutes about 30 to 70% of the total costs of the plant.
Continuous casting plants, particularly continuous casting plants for casting steel slabs, utilize rollers for guiding the strand, wherein the rollers serve to limit the thickness of the strand which is not yet fully solidified and to prevent bulging of the strand shell due to the ferrostatic internal pressure.
For this purpose, groups of at least four pairs of rollers are usually combined into segments. The strand guiding rollers arranged above the strand are mounted on the upper part of the segment or on the detachable frame part, while the strand guiding rollers located below the strand are mounted on the lower part of the segment or the fixed part of the segment. The fixed part and the detachable part of the individual segments are usually connected to each other through four tension cylinders. These so-called clamping cylinders pull the upper part of the segment onto spacers, so that the desired opening width between the oppositely located rollers is obtained. This opening width corresponds to the strand thickness.
Modern process technologies for improving the product quality make it necessary that the opening width can be changed during the casting process. Particularly the so-called soft reduction in the area of the tip of the liquid phase of the strand requires a conical adjustment and a variable opening width adjustment of the corresponding segment. A conventional possibility for changing the opening width of segments with four clamping cylinders is to construct the cylinders with hydraulic servo position control.
DE 196 27 336 C1 discloses a method and an apparatus for guiding a strand in a continuous casting plant with a soft reduction section in which the hydraulic servo units adjust the opening width of the oppositely located strand guiding rollers in an infinitely variable manner. The conventional strand guiding unit, which has in each segment four servo distance/cylinder units for the infinitely variable adjustment of the opening width of the oppositely located strand guiding rollers, is characterized in that the hydraulic lines connect the annular surfaces and piston surfaces of two adjacent servo piston/cylinder units to a common servo valve, and that position pickups of the servo piston/cylinder units controlled by a common servo valve can be coupled to each other through control technology.
The clamping cylinders are usually arranged on the segment laterally next to the rollers and, thus, are located together with the hydraulic lines and servo valves of the servo piston/cylinder units in the range of the radiation influence of the cast strand. Consequently, the clamping cylinders must be arranged at such a distance between the middle of the segment and the hydraulic cylinders that the radiation influence remains within acceptable limits. Because of the load influence on the frames, the required width of the frames of the segment leads to a comparatively great structural weight which, in turn, significantly increases the cost of the manufacture and assembly and the costs of the strands.
SUMMARY OF THE INVENTION
Therefore, starting from the prior art discussed above, it is the primary object of the present invention to significantly simplify a strand guiding element for slab casting machines of the above-described type as compared to conventional constructions, so that a significant saving of costs of the manufacture and assembly of the strand guiding elements is achieved while using pressure cylinders which are located outside of the cooling chamber due to the fact that they are supported in the area of the upper frame and by providing a lighter weight frame construction and a simplified water cooling system as well as locations of the lines for the roller cooling means.
It must be taken into consideration in this connection that the room for structural improvements in a component which has been technically further developed with continuous progress over decades is relatively small, so that at first glance it would appear that significant improvements and cost savings are not possible.
In this connection, the present invention which provides an innovative segment adjustment with upper pressure cylinders is further based on the concept of finding solutions for dynamically adjustable controllable upper frames of the segment, so that
the upper frame is pivotable with respect to all axes while being stiff with respect to bending and twisting, wherein
an adjustment of the upper frame is possible with exact dimensional accuracy of the desired opening width geometry with respect to thickness and inclination in the direction of the longitudinal and width axis,
the hydraulic cylinders can be constructed as pressure cylinders with relatively small diameters in order to reduce the load moment by reducing the lever arm, wherein
the cylinders including their measuring and control units are located outside of the cooling chamber, and wherein
the outer segment rollers are drivable due to the changed construction,
so that, while simultaneously operating in an optimum manner, an inexpensive segment type is obtained which is superior to the conventional type with tension cylinders and replaces the conventional type.
In accordance with the present invention, the above object is surprisingly met by
providing as adjusting means four independently adjustable pressure cylinders and arranging the pressure cylinders outside of the radiation range at the upper side of the segment, wherein the distance between the segment middle and cylinder which determines the segment width is reduced on both sides by the dimension of the cylinder which has been moved to the upper side of the segment,
providing the segment crossbeams with radiation protection plates instead of water cooling means, and
by flanging cooled side frames laterally to the bottom frames.
As a result of the configuration according to the present invention, the cylinders are connected in a novel manner and are located outside of the radiation range of the strand on the upper side of the segment and, thus, the cylinders including their pipe connections and valve arrangements are less susceptible to thermal danger. Moreover, because of the smaller segment width, the frame construction may have a significantly smaller weight while the stiffness remains the same; this is because the lever arm between the pressure cylinders and the ferrostatic force is reduced. In addition, tests have shown that by providing the segment crossbeams with radiation protection plates, the previously used complicated crossbeam and frame cooling means using cooling water is no longer required for preventing an undue heating of the crossbeams; also contributing to this is the fact that cooled side frames are flanged laterally to the bottom frame.
Additional advantageous results are obtained by providing significant further developments of the strand guiding segment according to present invention for an optimum solution of the above-mentioned object. These results are
a box-shaped side frame part is constructed as a water-conducting duct; and
water connections for cooling the rollers
Arnolds Gerhard
Becker Martin
Zajber Adolf
Dunn Tom
Kueffner Friedrich
SMS Schloemann--Siemag Aktiengesellschaft
Tran Len
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