Title of Invention

PROCESS FOR CASTING THIN CONTINUOUS CASTINGS AND STRIP-CASTING PLANT FOR PRODUCING THIN CONTINUOUS CASTINGS

Abstract

The invention relates to a process and to a strip-casting plant for producing thin continuous casting, in particular of steel, comprising an endless belt on to which is directed liquid metal via a feeding means which comprises a casting duct and is in communication with a metallurgical vessel. In this regard, the feeding means (11) is designed to be a resistance duct part (14), and a second casting duct part (15), the month (16) of which faces the endless belt (31) and has dimensions which correspond to the finished product (S) in its cross-sectional area, and the feeding means (11) is connected to a receptacle (12) which is designed to be fed with liquid melt (M) from a metallurgical vessel (21), and measuring devices (71) are provided for detecting the level (P) of the liquid melt (M) in the receptacle (12) and/or the thickness (ds) of the continuous casting disposed on the endless belt (31). In addition, the measured values are in communication with an actuator (73) via a measuring and controlling device (72) which is connected to a device (24, 25) for adjusting the outflow rate from the metallurgical vessel (21).

Full Text

The invention relates to a process for casting thin continuous castings, in particular of steel, using a strip-casting plant in which liquid metal is fed from a metallurgical vessel via a feeding means on to an endless belt, and a corresponding strip-casting plant. When producing strips in a strip-casting process, with the strip surface cooled on one side, difficulties arise in the production of these strips with narrow thickness tolerances. According to DE 35 21 778 C2, it is known to produce metal continuous castings in strip form, whereby the molten metal from a nozzle is applied on to the cooling surface, with a cooling body which is displaced past the nozzle with a narrow gap therebetween. In this regard, the outlet-side nozzle lip is adjustable with regard to its spacing from the cooling surface of the cooling body. The nozzle width (clear spacing) of the nozzle lip on the incoming and on the outgoing side of the continuous casting is arranged at a spacing which corresponds to the length of the cold solid-liquid interface. Strip produced using this process and this apparatus does not provide satisfactory results. The object of the invention is to provide a process together with a corresponding apparatus for casting thin continuous castings, by means of which it is possible to produce a continuous strip with close tolerance and the desired strip thickness, using simple constructional means and a reliable control of the process. Accordingly the present invention provides a process for casting thin continuous castings, in particular of steel, using a strip-casting plant in which liquid metal is fed from a metallurgical vessel via a feeding means on to an endless belt, characterized by the following steps: a) the liquid metal is directed from the metallurgical vessel into a receptacle to which is connected the feeding means, b) prior to the liquid metal making contact with the endless belt, the liquid metal thread in the feeding means encounters a resistance which reduces the flow rate of said liquid metal thread such that it makes contact with the endless belt at a flow rate which corresponds to the rate of withdrawal of the strip and that it has a width in the contacting region which corresponds to the thickness of the continuous casting, c) the level of the liquid metal disposed in the receptacle and/or the thickness of the continuous casting disposed on the endless belt is measured and maintained at a constant value by control technology, d) the updated measured values are supplied to an actuator which controls the quantity of liquid metal discharged from the metallurgical vessel. Accordingly the present invention also provmes a stnp-casnng plant lor producing thin continuous castings, in particular of steel, comprising an endless belt on to which is directed liquid metal via a feeding means which comprises a casting duct and is in communication with a metallurgical vessel, for carrying out the process described hereinabove, characterized in that the feeding means is designed to be a casting duct, which comprises a first casting duct part, which is designed to be a resistance duct part, and a second casting duct part, the mouth of which faces the endless beh and has dimensions which correspond to the finished product in its cross-sectional area, and in that the feeding means is connected to a receptacle which is designed to be fed with liquid melt from a metallurgical vessel, and in that measuring devices are provided for detecting the level of the liquid melt in the receptacle and/or the thickness of the continuous casting disposed on the endless beh, and in that the measured values are communicated to an actuator via a measuring and controlling device, which is connected to a device for adjusting the outflow rate fi"om the metallurgical vessel. According to the invention, the quantity of liquid metal supplied is maintained constant relative to the quantity of finished product discharged, i.e. the cast strip withdrawn from the endless beh installation. Prior to the liquid metal making contact with the endless belt, the flow rate of the liquid metal thread is reduced such that it makes contact with the endless belt at a rate corresponding to the rate of withdrawal of the strip and, in the contacting region, the liquid metal thread has a thickness which is adjusted to the desired thickness of the continuous casting. In this regard, the level of the liquid metal in the metallurgical vessel upstream of the feeding means is adjusted such that the geodetic height conforms to P For the purpose of accurately maintaining the height of the level, measuring means, e.g. a float or a bubble-type level indicator, are provided for detecting the level, and for maintaining the thickness of the strip, e.g. distance probes are provided, and these act, via a measuring and controlling means, on an actuator which controls shut-off devices for controlling the flow rate. It is possible for these shut-off devices to be sliding gates or even a plug. In order to adjust the flow rate of the liquid metal thread in a reliable manner, the casting duct is designed such that the first casting duct part constitutes a resistance duct part. The mouth of the second casting duct part is designed such that it has the same cross-sectional area as the subsequent finished product. In an advantageous development, the resistance duct part is designed to be a throttle, having a width which is smaller than the subsequent thickness of the continuous casting, according to the formula dw = 0.5 to 0.8 x ds, with dv = the width of the resistance duct part and dg = the thickness of the continuous casting. In addition, the casting duct has a shape such that the first duct part, which is designed to be a resistance duct, is longer than the second duct part. In a further advantageous development, a resistance member is provided in the resistance duct, and said member is designed to be a filter, having a free area of 0.6 to 0.8 x the cross-sectional area of the casting duct. In this regard, it is possible for the free area of said filter to be formed by bores provided in a refractory plate. In one embodiment, the liquid metal thread is heated in the region of the feeding means. To this end, it is proposed that the wall of the casting duct be constructed of an electrically conductive refractory material and that an induction coil be used as the heating means. An advantageous development of the invention involves decelerating the flow rate of the liquid metal thread. For this purpose, an eddy current brake is provided, on its own or in addition to the above-described throttle, the static magnetic field of which eddy current brake decelerates the flow rate of the liquid metal thread. In a further development, a linear motor-like arrangement is provided for decelerating the flow rate of the liquid metal thread by generating a field which travels in a direction opposite to the direction of flow of the melt. In a specific embodiment, the first casting duct part is designed to be a pipe. It is possible for said pipe to be arranged in the bottom of the receptacle so as to point in a vertical direction. In the present embodiment, the mouth of said first casting duct part is connected to a second casting duct part which is designed in the manner of a gaping funnel, the mouth of which has dimensions which correspond to the finished product. In this regard, it is possible for the second duct part, in order to ensure a uniform outflow rate across the breadth of the continuous casting, to have cross-sectional areas which become smaller in the direction of flow of the melt in the casting duct part. An example of the invention is illustrated in the attached drawing, in which: Figures 1 and 3 diagrammatically show the entire strip-casting plant for producing thin continuous castings. Figure 2 shows resistance members in the casting duct. Figures 1 and 3 show a metallurgical vessel 21 filled with liquid metal M and comprising a bottom opening 22 in the bottom. An immersion spout 23, which dips into a melt M which is disposed in a receptacle 12, is arranged at said bottom opening 22. In Figure 1, the bottom opening 22 of the metallurgical vessel 21 is designed to be sealed by means of a sliding gate 25, and in the vessel of Figure 3 by means of a plug 24. Via control exercised by an actuator 73, the quantity of liquid metal M flowing out of the metallurgical vessel 21 is continuously and steadily controllable. The level of the liquid metal M disposed in the receptacle 12 is detected via a level-measuring device 71, this being a float 74 in Figure 1 and a bubble-type level indicator 75 in Figure 3. The actuator 73 and the level-measuring device 71 are connected to a measuring and controlling device 72. An endless belt 31, which has a driven guide roller 32 and a free roller 33, is provided below the receptacle 12. The liquid metal is deposited on to the carrying run 34 of the endless belt, where it solidifies and is then removed as the finished product S. In Figure 1, the feeding means 11 is designed to be a casting duct which comprises a first casting duct part 14 which is designed to be a resistance duct part. Connected to said first casting duct part 14 is a second casting duct part 15 which comprises an outlet opening 16. The width d of the resistance duct part is smaller than the thickness dg of the continuous casting. In this regard, the resistance duct part has a length L14 which is greater than the length of the second duct part L,j. Instead of the smaller width d,, it is possible to provide a resistance member in the first casting duct part, as is illustrated in Figure 2. It is possible to be designed as an independent resistance member 41 having a rectangular opening (top part of the drawing) or it may be a filter 42 having bores 43 (bottom half of the drawing) . In this regard, the free area Ap is composed of the sum total of the bores 43, and has a size of 0.6 to 0.8 X AK (cross-sectional area of the casting duct) . A heating means 51 is outlined in the wall 17 in the lower part of the feeding means 11, and an induction coil 52 in the upper part. In Figure 3, the first casting duct part 14 is designed to be tubular and a second casting duct part 15 of the feeding means 11 is connected thereto. In this regard, the second casting duct part is designed as a gaping funnel which is inclined toward the carrying run 34 of the endless belt 31. LIST OF REFERENCE NUMBERS Feed 11 feeding means 12 receptacle 13 casting duct 14 first casting duct part / resistance duct part 15 second casting duct part 16 outlet opening 17 wall Belt 31 endless belt 32 driven guide roller 33 loose roller 34 carrying run Resistance 41 resistance member having a rectangular opening 42 filter 43 bores Heating 51 heating means 52 induction coil Deceleration 61 eddy current brake 62 linear induction motor Measuring and controlling means 71 level-measuring device 72 measuring and controlling device 73 actuator 74 float 75 bubble-type level indicator WE CLAIM : 1. Process for casting thin continuous castings, in particular of steel, using a strip-casting plant in which liquid metal is fed from a metallurgical vessel via a feeding means on to an endless belt, characterized by the following steps: a) the liquid metal is directed from the metallurgical vessel into a receptacle to which is connected the feeding means, b) prior to the liquid metal making contact with the endless belt, the liquid metal thread in the feeding means encounters a resistance which reduces the flow rate of said liquid metal thread such that it makes contact with the endless belt at a flow rate which corresponds to the rate of withdrawal of the strip and that it has a width in the contacting region which corresponds to the thickness of the continuous casting, c) the level of the liquid metal disposed in the receptacle and/or the thickness of the continuous casting disposed on the endless belt is measured and maintained at a constant value by control technology, d) the updated measured values are supplied to an actuator which controls the quantity of liquid metal discharged from the metallurgical vessel. 2. Process as claimed in claim 1, wherein the supplied quantity of liquid metal is adjusted in the metallurgical vessel such that the geodetic height of the liquid level (P) relates to the thickness (dg) of the continuous casting as P ds- 3. Process as claimed in claim 1 or claim 2, wherein the liquid metal thread is heated in the region of the feeding means. 4. Process as claimed in claim 3, wherein the liquid metal is maintained at a temperature near its melting point. 5. Process as claimed in any one of claims 1 to 4, wherein the flow rate of the liquid metal thread is reduced by means of throttling elements. 6. Process as claimed in any one of claims 1 to 4, wherein the flow rate of the liquid metal thread is decelerated and that a static magnetic field is generated for decelerating the flow rate of the liquid metal thread. 7. Process as claimed in any one of claims 1 to 4, wherein the flow rate of the liquid metal thread is decelerated and that a magnetic field, which is directed oppositely to the direction of flow of the melt, is generated for decelerating the flow rate of the liquid metal thread. 8. Strip-casting plant for producing thin continuous castings, in particular of steel, comprising an endless belt on to which is directed liquid metal via a feeding means which comprises a casting duct and is in communication with a metallurgical vessel, for carrying out the process as claimed in claim 1, characterized in that the feeding means (11) is designed to be a casting duct (13), which comprises a first casting duct part, which is designed to be a resistance duct part (14), and a second casting duct part (15), the mouth (16) of which faces the endless belt (31) and has dimensions which correspond to the finished product (S) in its cross-sectional area, and in that the feeding means (11) is connected to a receptacle (12) which is designed to be fed with liquid melt (M) from a metallurgical vessel (21), and in that measuring devices (71) are provided for detecting the level (P) of the liquid melt (M) in the receptacle (12) and/or the thickness (d2) of the continuous casting disposed on the endless beh (31), and in that the measured values are communicated to an actuator (73) via a measuring and controlling device (72), which is connected to a device (24, 25) for adjusting the outflow rate from the metallurgical vessel (21). 9. Strip-casting plant as claimed in claim 8, wherein the resistance duct part (14) has a width (d), in accordance with d = 0.5 to 0.8 x dg, with 4 = thickness of the continuous casting. 10. Strip-casting plant as claimed in claim 8 or 9, wherein the resistance duct part (14) has a length (L14), wherein Lu > L15; with L15 length of the second duct part (15). 11. Strip-casting plant as claimed in claim 8, wherein a resistance member (41) is provided in the resistance duct part (14) and is designed to be a filter (42) having a free area (AF), with AF 0.6 to 0.8 x AK, with AK cross-sectional area of the casting duct. 12. Strip-casting plant as claimed in claim 11, wherein the free area (AF) of the filter (42) is constituted by bores (43) provided in a refractory plate (44). 13. Strip-casting plant as claimed in any one of claims 8 to 12, wherein a heating means (51) is provided in the wall (17) of the casting duct (13). 14. Strip-casting plant as claimed in claim 13, wherein the wall (17) of the casting duct (13) is constructed of electrically conductive refractory material, and in that the heating means (51) is an induction coil (52). 15. Strip-casting plant as claimed in claim 8, wherein an eddy current brake (61) is provided in the wall (17) of the casting duct (13) for decelerating the flow rate of the liquid metal thread by means of a static magnetic field. 16. Strip-casting plant as claimed in claim 8, wherein a linear motor-like arrangement (62) is provided for decelerating the flow rate of the liquid metal thread by generating a field which travels in a direction opposite to the direction of flow of the melt. 17. Strip-casting plant as claimed in any one of claims 8 to 16, wherein the first casting duct part (14) is designed to be a pipe, the cross-sectional area in the region of its opening being designed to be a gaping funnel, and in that the second duct part (15) has substantially the same cross-sectional area as that of the continuous casting (S). 18. Strip-casting plant as claimed in claim 17, wherein the cross-sectional areas of the casting duct (13) become smaller in the direction of flow of the melt, in order to ensure a uniform outflow rate of the liquid metal across the breadth of the metal thread. 19. Process for casting thin continuous castings, substantially as hereinabove described and illustrated with reference to the accompanying drawings. 20. Strip-casting plant for producing thin continuous castings, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

Documents:

432-mas-1998 abstract-duplicate.pdf

432-mas-1998 abstract.jpg

432-mas-1998 abstract.pdf

432-mas-1998 assignment.pdf

432-mas-1998 claims-duplicate.pdf

432-mas-1998 claims.pdf

432-mas-1998 correspondence-others.pdf

432-mas-1998 correspondence-po.pdf

432-mas-1998 description (complete)-duplicate.pdf

432-mas-1998 description (complete).pdf

432-mas-1998 drawings-duplicate.pdf

432-mas-1998 drawings.pdf

432-mas-1998 form-1.pdf

432-mas-1998 form-13.pdf

432-mas-1998 form-19.pdf

432-mas-1998 form-2.pdf

432-mas-1998 form-26.pdf

432-mas-1998 form-29.pdf

432-mas-1998 form-4.pdf

432-mas-1998 form-6.pdf

432-mas-1998 others.pdf

432-mas-1998 petition.pdf