CONTINUOUS CASTING INSTALLATION FOR THIN SLABS

Abstract

An apparatus for the continuous casting of thin slabs, having a strand guide, which is arranged downstream of a permanent mold in the casting direction and which guides the strand output from the permanent mold along a first direction, having an adjoining bending/straightening region, which a mechanism for driving and bending the strand in a second direction, which differs from the first direction, having a cutting device, which cuts the strand into thin slabs, and having a first furnace, which is provided for temperature compensation in the strand, wherein the first furnace extends in an arched manner at least partially over the bending/straightening region and in part along the second direction.

Claims

1-12. (canceled)

13. A device for continuous casting of thin slabs, comprising; a permanent mold; strand guide that, in a casting direction, is disposed behind the permanent mold and guides a strand that is delivered by the permanent mold along a first direction; a bending/straightening region that adjoins said strand guide and has means for driving and bending the strand in a second direction that differs from the first direction; a cutting installation that cuts the strand into thin slabs; and a first furnace provided for equalizing temperature in the strand, wherein the first furnace extends in an arcuate manner at least partially across the bending/straightening region and in part along the second direction.

14. The device according to claim 13, further comprising at least one cooling segment provided in a region of the strand guide for cooling the strand.

15. The device according to claim 13, wherein the first furnace is curved in a range between 10° and 80°.

16. The device according to claim 13, wherein the device is configured for casting thin slabs having a thickness between 35 mm and 90 mm.

17. The device according to claim 16, wherein the device is configured for casting thin slabs having a thickness between 40 mm and 60 mm.

18. The device according to claim 13, wherein the cutting installation is disposed, in the casting direction, behind the first furnace.

19. The device according to claim 13, further comprising a second furnace behind the first furnace, the cutting installation being provided between the two furnaces.

20. The device according to claim 13, wherein the bending/straightening region is formed by a bending region having bending rollers, and by a straightening region having straightening rollers, wherein at least one of the bending rollers and/or the straightening rollers is disposed in the first furnace.

21. The device according to claim 13, further comprising a water wiper for removing splash water provided ahead of an entry to the first furnace.

22. The device according to claim 13, wherein a region at an entry of the first furnace is configured so that a strand is directable past the first furnace.

23. The device according to claim 21, wherein a forward region of the first furnace is configured so as to be displaceable and/or pivotable.

24. The device according to claim 13, further comprising at least one heat-resistant camera provided in the first furnace.

25. The device according to claim 13, wherein at least one roller is displaceable in the bending/straightening region.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0020] FIG. 1a shows a conventional CSP plant having a horizontal furnace; FIG. 1b shows temperature profiles of a strand cast therewith, as a function of the distance from the meniscus.

[0021] FIG. 2a shows a conventional CSP plant having a horizontal furnace; FIG. 2b shows temperature profiles of a strand cast therewith, as a function of the distance from the meniscus.

[0022] FIG. 3 shows a CSP plant according to one exemplary embodiment, having a curved furnace.

[0023] FIG. 4 shows an enlarged fragment of the furnace entry of the exemplary embodiment of FIG. 3.

[0024] FIG. 5a shows a CSP plant according to a further exemplary embodiment, having two furnaces; FIG. 5b shows a temperature profile of a strand cast therewith, as a function of the distance from the meniscus.

[0025] FIG. 6a shows a CSP compact plant according to a further exemplary embodiment, having two furnaces; FIG. 6b shows a temperature profile of a strand cast therewith, as a function of the spacing from the meniscus.

DETAILED DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS

[0026] Exemplary embodiments of the invention will be described in detail hereunder with reference to the drawings. It is to be pointed out that the exemplary embodiments described herein are not intended to limit the invention but to explain the invention, wherein the features or combination of features of the exemplary embodiments presented do not always have to be essential to the invention.

[0027] FIG. 3 shows a vertical bending plant according to a first exemplary embodiment. A funnel-type permanent mold from which the cast steel exits as a strand 1 in a vertically downward manner is identified by the reference sign 10. The strand 1 thus demolded is subsequently guided along a strand guide 20 (in continuing vertically downward manner) and is cooled by means of cooling segments 30. The cooling segments 30 form the so-called secondary cooling. The strand 1 is completely solidified at or shortly before the end of the last cooling segment 30. The strand 1 subsequently makes its way below the strand guide 20 into the bending region 40 where said strand 1 is exposed to bending forces. This is performed by means of rollers and roller pairs 41, the position of which can be derived from FIG. 1a. The straightening region 50 in which the strand 1 is brought to the horizontal alignment adjoins the bending region 40. Rollers 51 are provided here too. One or a plurality of the rollers 51 is/are drive rollers and propel the strand in the transportation direction; other rollers 41, 51 serve for guiding and straightening the strand 1. To this extent, the rollers 41 and 51 form means for driving and bending the strand.

[0028] By contrast to the plant of FIG. 1a, no cutting installation 60 is illustrated in FIG. 3, since said cutting installation 60 is located behind the furnace 80. The furnace 80 has a horizontal portion 85 (generally a portion along the second direction) and a curved portion 86 which extends at least partially across the bending/straightening region 40, 50. As compared to the plant of FIG. 1a, the furnace 80 is thus lengthened toward the front, in the direction of the permanent mold 10, into or beyond the straightening region 50. The furnace 80 is preferably embodied as a tunnel furnace and serves for equalizing the temperature in the strand. The strand 1 is subsequently cut into thin slabs by means of the cutting installation 60 (not illustrated). The transportation direction of the strand 1 is indicated by an arrow line T.

[0029] The arc length of the portion 86 of the furnace is preferably in the range from 10° to 80° . Already a minor lengthening of 10° into the straightening region 50 achieves a significant reduction in the temperature drop of the strand 1. A lengthening beyond 80° is difficult to implement in technical terms. The strand 1 should preferably be completely solidified ahead of the furnace entry 80, on the one hand, while a spacing between the end of the strand guide 20, or between the end of the last cooling segment 30 and the furnace entry 81, respectively, for reasons of maintenance and other reasons which will become evident further below, is desirable, on the other hand. However, the furnace 80 should tend to be constructed so as to be as close as possible to the end of the cooling 30, since the hot strand 1 radiates much heat specifically at high temperatures.

[0030] Following on from the furnace 80, the strand 1 is cut into thin slabs by means of the cutting installation 60 (not illustrated in FIG. 3). FIG. 5a which, except for the embodiment of the furnace 80 and the position of the cutting installation 60, is similar to the plant of FIG. 3, shows that the positioning of the cutting installation 60 can also be performed differently. The cutting installation in FIG. 5a keeps the conventional position thereof (as compared to the plant of FIG. 1a). To this end, the cutting installation 60 is located in an intermediate space between the furnace 80, which in this context is also referred to as the first furnace, and a second furnace 90. The second furnace is provided so as to be entirely horizontal, or along the second direction, respectively.

[0031] In that the furnace 80 is lengthened toward the front and is curved, it cannot be entirely precluded that residual splash water can ingress into the furnace 80. For this reason, a water wiper (not illustrated) is preferably provided ahead of the furnace entry 81. The water wiper can be implemented for instance by means or one or a plurality of wiping plates and/or air pressure and/or water blasting and/or by means of a suction installation.

[0032] The furnace entry 81 is preferably configured such that the dummy strand, in particular when being threaded out (not illustrated in the figures), or the strand 1 in the case of damage can be directed past the furnace 80. This can be achieved by beveling the furnace entry 81, as is shown in FIG. 4. Alternatively or additionally, the furnace entry 81 or the front region of the furnace 80 is configured so as to be displaceable at least on the lower side, this also including any potential pivoting movement. “Dummy strand” herein is understood to be that strand that is introduced into the casting plant prior to the start of casting. The liquid material is cast onto this dummy strand. The dummy strand serves to prevent the material that at the start of casting is still liquid from rapidly flowing through the cooling segments 30 but instead to first form a firm strand trough and to subsequently be slowly drawn conjointly with the dummy strand through the secondary cooling 30. The material after cooling is solidified to the core and can be guided onward without the dummy strand. According to this embodiment, this dummy strand is to be separated from the real strand 1 ahead of the furnace 80 and to be removed in a vertically downward manner. The dummy strand can be made as a dummy strand chain.

[0033] One or a plurality of the rollers 41, 51 is/are provided so as to be displaceable in order for threading of the strand 1 into the furnace 80 to be facilitated. In particular, the positions of the two entry rollers which are identified by the reference sign 82 are preferably provided so as to be modifiable. However, a displacing capability of this type can also be provided for other rollers, in particular for the straightening rollers 51. To this end, the furnace 80 has to offer sufficient space in an upward direction in order for the straightening rollers 51 to be able to be opened out sufficiently in relation to the strand guide 20. The setting of the respective rollers 41, 51 in the furnace 80, the diverging of roller pairs, etc., can be implemented by means of a hydraulic controller. In order for the threading to be able to be observed from the outside, one or a plurality of heat-resistant cameras (not illustrated) is/are preferably installed in the furnace 80.

[0034] The furnace 80, or part thereof, can be conceived as a passive furnace which is actively heated only in the case of the start of casting or at low casting speeds (comparatively low average temperature); said furnace 80 otherwise serves as a good insulation. Whether the furnace 80 is operated as an active or a passive furnace can vary depending on the individual situation, and depends heavily on the specific casting conditions. Examples thereof will be discussed further below.

[0035] In order to avoid that the straightening rollers 51 are damaged by the high environmental temperatures, said straightening rollers 51 are preferably cooled. Alternatively, the rollers 51 are made from a high-strength and heat-resistant material such that no heat is dissipated by way of the rollers 51. These exemplary embodiments can be applied in an analogous manner to other rollers of the bending/straightening region.

[0036] FIG. 5a, introduced above, shows an exemplary embodiment that is similar to that of FIG. 3. However, two furnaces 80 and 90 are provided instead of one furnace 80, the cutting installation 60 being disposed between said furnaces 80 and 90.

[0037] A special operating configuration of this plant is to be described hereunder. To this end, an exemplary temperature profile of the strand 1 along the transportation direction is shown in FIG. 5b. The graph shows the temperature profile on the surface of the strand 1, in the core, and the average temperature as a function of distance, proceeding from the meniscus on the permanent mold, for a low-carbon material having a slab size of 1600 mm×60 mm at a casting speed of 5.2 m/min.

[0038] According to this example, the 60 mm thick strand is cast in the CSP plant so as to have a metallurgical length of approximately 8 m. A low-carbon material having a liquidus temperature of 1529° C. and a solidus temperature of 1499° C. in the case of superheating at 25° C. solidifies after approximately 7.4 m. The average temperature at the end of the cooling segments 30 at approx. 8 m is approximately 1250° C., and by radiation and contact with the bending rollers 41 up to the furnace entry 81 at approx. 11 m drops to approximately 1200° C. The first furnace 80 in this example is approximately 6 m long and does not have to actively heat the strand 1 at this casting speed. However, said first furnace 80 does have to be heated up to 1200° C. at least prior to the first casting. Furthermore, said first furnace 80 is conceived as an active furnace for comparatively low casting speeds or in the case of a comparatively thin material of the strand 1. It is furthermore assumed that the straightening rollers 51 that are located in the first furnace 80 do not substantially extract heat from the strand 1. At the furnace exit, which is identified by the reference sign 84, the temperature in the strand 1 after approx. 17 m has been equalized and at each cross-sectional position is approximately 1200° C. The cutting installation 60 can be located over the next 3 m. The average temperature of the strand 1, by way of the free thermal radiation and by contact with the rollers, drops by approx. 50° C. to approximately 1150° C. The strand 1 now reaches the second furnace 90. Therein, an equalization of temperature is performed anew. Behind the second furnace 90 which is typically shorter than the first furnace 80 and in the present example has a length of 5 m, the temperature in the strand 1 has again been equalized, optionally without active heating, and the strand 1 can run directly into the adjoining rolling mill. In order for lower temperatures to be obtained upon secondary cooling, and in order to have sufficient safety zones in the case of malfunctions, the furnaces 80, 90 can be constructed so as to be substantially longer, and the position of the cutting installation 60 could be located further to the rear.

[0039] An alternative exemplary embodiment which is loosely based on the compact plant of FIG. 2a is shown in FIG. 6a. The temperature profile of the plant is derived from FIG. 6b. In a manner analogous to that of FIG. 2b, the graph of FIG. 6b shows the temperature profile on the surface of the strand 1, in the core, and the average temperature as a function of distance, proceeding from the meniscus on the permanent mold, for a low-carbon material having a slab size of 1350 mm×40 mm at a casting speed of 4 m/min. Moreover, the same construction of the individual components and the functions thereof still apply, and a repeat of the description is dispensed with for the sake of avoiding redundancy.

[0040] It is a common feature of all exemplary embodiments that the average temperature of the strand 1 between the exit from the last cooling segment 30 up to the cutting installation 60 drops less severely than is the case with plants according to FIGS. 1a and 2a, for instance. This is clearly derived from a comparison of the respective temperature profiles.

[0041] Lower energy costs are one positive consequence. This is amplified when the furnace 80 and/or 90 has to be heated only prior to the start of casting and in the case of low casting speeds, and otherwise can be utilized for passive thermal equalization. Since the temperature does not drop so severely, less precipitation is created, on account of which the risk of fissures is reduced, and the mechanical properties of the slabs are improved. The growth in scale is reduced by the oxygen-starved furnace atmosphere, leading to higher output. Overall, the furnace can be constructed in a more compact manner, and the production shed can thus be constructed in a shorter manner. Even when a cutting installation is installed between two furnaces 80 and 90 (approx. 3 m free radiation) the average strand temperature is still sufficiently high for the adjoining rolling mill.

[0042] To the extent that they are applicable, all individual features which are illustrated in the exemplary embodiments can be combined with one another and/or replaced by one another without departing from the scope of the invention.

LIST OF REFERENCE SIGNS

[0043] 1 Strand [0044] 10 Permanent mold [0045] 20 Strand guide [0046] 30 Cooling segments [0047] 40 Bending region [0048] 41 Rollers of the bending region [0049] 50 Straightening region [0050] 51 Straightening rollers [0051] 60 Cutting installation [0052] 70 Furnace [0053] 71 Furnace entry [0054] 80 First furnace [0055] 81 Furnace entry [0056] 82 Entry rollers [0057] 84 Furnace exit [0058] 85 Furnace portion along the second direction [0059] 86 Curved furnace portion [0060] 90 Second furnace [0061] T Transportation direction of the strand or of the thin slabs, respectively