MX2008006245A

MX2008006245A - Twin roll caster, and equipment and method for operating the same

Info

Publication number: MX2008006245A
Application number: MX/A/2008/006245A
Authority: MX
Inventors: Fukase Hisahiko; Otsuka Hiroyuki; Iso Yoshiyuki; Nakayama Katsumi; Osada Shiro
Original assignee: Ishikawajima Harima Heavy Ind Co Ltd
Priority date: 2005-11-16
Filing date: 2008-05-14
Publication date: 2008-09-02

Abstract

Casting rolls (12) for a twin roll continuos casting machine comprise a plurality of cooling passages extending through a central portion (17). The cooling passages comprise longitudinal cooling passages (14). The cooling passages also comprise at least one bend in the cooling passages which requires cooling fluid flowing through a cooling passage to undergo a change in direction. Each casting roll also comprises a flow control member, such as baffles (32), positioned in the bend to control the flow of cooling fluid around the bend.

Description

DOUBLE ROLLER FOUNDER, AND EQUIPMENT AND METHOD TO OPERATE THE SAME TECHNICAL FIELD This invention relates generally to double roll casters, and more particularly to cast rolls for a double roll caster. The double roll method of continuous casting of thin metal strip of molten metal between a pair of opposite rotary casting rolls and through a line of contact between the rolls is known. Figures 14 and 15 show an example of a continuous casting machine of a prior art. With reference to the Figures, the casting rollers 2 are in contact with lateral reservoirs 1 on the circumferential end surfaces of the casting rollers 2 and have hollow stub axles 3 axially coupling the two ends of the casting rollers 2 (see for example, North American Patent No. 6,241,002). The two end portions of the casting rollers 2 are smaller than the central portions and have a shape so as to make contact with the lateral deposits 1. In the continuous casting machine, the casting rollers 2 are arranged laterally to one another, such that the contact line of the rollers of The cast iron can be adjusted according to the thickness of the S-band to be manufactured. The side tanks 1 are in contact respectively with the end surfaces of larger diameter central portions of the casting rolls 2. The arrangement is such that the casting rollers 2 and the side tanks 1 contain the molten metal M. The speed and direction of revolution of the cast rolls are configured so that the outer circumferential surfaces move towards the opening of the cast rolls at the same speed. Radially below and spaced from the position of the lateral reservoirs, the known casting rollers 2 have a plurality that extend axially, i.e., internal, longitudinal cooling passages 4, located circumferentially equidistantly, and a plurality of passages 5. of cooling that extend radially connected to the ends of the longitudinal cooling passages 4. The cooling passages 4 extend from one end of the cast rolls to the other end of the cast rolls radially below the position of the side tanks. The screws 7 or plugs 6 at the ends served as plugs to close the ends of the longitudinal cooling passages 4. The radial cooling passages 5 extend from a circumferential surface inside the casting rolls at right angles to the longitudinal cooling passages 4. The radial cooling passages 8 pass through the hollow shaft 3 to allow the cooling water W to flow through a hollow shaft 3 to the radial cooling passages 5, then to the longitudinal cooling passages 4, corresponding to the passages 8, 5 radially cooling at the other end of the casting roll 2, and finally into the other hollow shaft 3. In such a continuous casting machine, the heat is removed by means of cooling water w flowing through the radial cooling passages 5 and the longitudinal cooling passages 4 while the molten metal M is poured into the space bounded by the deposits 1 casting rollers 2 forming an accumulation of molten metal M on the contact line between the casting rollers. While the cast rolls rotate, the metal being cooled on the outer circumferential surfaces of the casting rolls 2 forms solidified sheets that form an S-band, and the S-band moves downwardly from the opening of the cast rolls . However, the cooling rate of the molten metal is limited by the conductivity of the heat from the circumferential surfaces up to the cooling passages. Therefore, it is apparent that it would be of advantage to provide an apparatus and an alternative method that provides more efficient casting of melted web. Accordingly, a suitable alternative is provided which includes features described more fully hereinafter.

DESCRIPTION OF THE INVENTION An apparatus and method for melting metal strip having a pair of casting rollers located laterally forming a line of contact between them is described. A molten metal supply system distributes molten metal to the nip between the cast rolls and forms an accumulation of molten metal cast on the cast rolls immediately above the nip. A pair of side tanks, one on each end of the pair of cast rolls, limit the accumulation of molten metal and splice the axial end surfaces of the cast rolls. Each casting roller comprises a cylindrical body. In one modality the body is a body step cylindrical comprising a cylindrical central portion of an outer diameter greater than the adjacent cylindrical end portions extending axially from each end of the central portion in an inwardly stepped projection forming a radially extending end surface. Each casting roller also comprises a plurality of cooling passages extending through the central portion, typically between the radially extending end surfaces. The cooling passages comprise longitudinal cooling passages. The cooling passages also comprise at least one elbow in the cooling passages which requires cooling fluid to flow through a cooling passage to undergo a change of direction. Each casting roller also comprises a flow control member located in the elbow to control the flow of cooling fluid around the elbow. Each casting roller may comprise radial cooling passages extending from an inner periphery of the casting rolls and connected to a longitudinal cooling passage, with a bend being formed where the radial and longitudinal cooling passages are joined.

In one embodiment each casting roller comprises at least one circumferential section that interconnects with the adjacent longitudinal cooling passages so that the cooling fluid can flow from a longitudinal cooling passage into and then along a longitudinal cooling passage. adjacent with the elbow that is formed in the circumferential section. In one embodiment, the flow control member comprises a baffle that is formed and positioned at the elbow to change the flow of cooling fluid around the elbow. For example, the baffle is positioned to extend from an inner corner of the elbow to an outer corner of the elbow. This arrangement reduces the cross section of the elbow and causes an increase in the speed of the cooling fluid, such as water, and also directs the cooling fluid towards the outer corner of the elbow. In one embodiment, the flow control member is a plurality of fins that are formed and placed on the elbow to change the flow of cooling fluid around the elbow. For example, the fins are aligned circumferentially and project from positions in the vicinity of the radially extending end surfaces and extend in the direction of the passage of longitudinal cooling, and cooling fluid, such as water, is caused to flow through the cooling passage. Therefore, the fins reduce the cross section of the elbow and therefore increase the speed of the cooling fluid, and also conduct the heat of the casting roller from the fins to the cooling fluid. In one embodiment, the flow control member is a plurality of inserts that are positioned in the elbow to change the flow of cooling fluid around the elbow. For example, the inserts fill a portion of the elbow and therefore reduce the cross-sectional area of the elbow and therefore increase the speed of the cooling fluid, such as water, and also direct the cooling fluid to the vicinity of the circumferential surface outside of the roller on the elbow. The examples mentioned above are not the only possible flow control members. The foregoing and other aspects will become apparent from the following detailed description of the invention when considered together with the figures of the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic drawing showing a vertical cross section of a continuous casting machine mode; Figure 2 is a schematic drawing showing one of the baffles shown in Figure 1; Figure 3 is a schematic drawing showing an axial view of the cast rolls and the stub axles shown in Figure 1; Figure 4 are two diagrams comparing the distribution of the flow rate of the cooling water in the continuous casting machine shown in Figure 1, ie, with internal baffles, and in an example of a continuous casting machine in the which there are no internal deflectors; Figure 5 are two diagrams comparing the distribution of the flow rate of the cooling water in the continuous casting machine shown in Figure 1, ie, with internal deflectors, and in an example of a continuous casting machine in the which there are no internal deflectors; Figure 6 is a schematic drawing showing a vertical cross section of another embodiment of a continuous casting machine; Figure 7 is a schematic drawing of the fins shown in Figure 6; Figure 8 are two diagrams comparing the distribution of the flow rate of the cooling water in the continuous casting machine shown in Figure 6, that is, with internal fins, and in an example of a continuous casting machine in the which there are no internal deflectors; Figure 9 are two diagrams comparing the distribution of the flow rate of the cooling water in the continuous casting machine shown in Figure 6, ie, with internal fins, and in an example of a continuous casting machine in the which there are no internal deflectors; Figure 10 is a schematic drawing showing a vertical cross section of another embodiment of a continuous casting machine; Figure 11 is a schematic drawing showing a side cross-sectional view of the positions of the longitudinal cooling passages, circumferential cooling passages, and inserts of Figure 10; Figure 12 is a schematic drawing showing a horizontal cross-sectional view of the positions of the longitudinal cooling passages, circumferential cooling passages, and inserts of Figure 10; Figure 13 are two diagrams that compare the distribution of the flow rate of the cooling water in the continuous casting machine shown in Figure 10 in which there are internal circumferential cooling passages and in an example of a continuous casting machine in which there are no circumferential cooling passages; Figure 14 is a schematic drawing showing a vertical cross section of a continuous casting machine of a prior art; and Figure 15 is a schematic drawing showing an axial view of the cast rolls and the stub axles shown in Figure 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In general terms, Figures 1 to 5 show cylindrical cast rolls with a central portion and projecting portions adjacent to the lateral deposits. The projecting portions define the radially extending end surfaces of the central portion. The cast rolls have longitudinal cooling passages extending through each of the central portions of the cast rolls from one projection portion to the other projecting portion. The radial cooling passages pass through each of the cast rolls from the inner circumferential surfaces.

The radial cooling passages are in positions that are close to the radially extending end surfaces. The cylindrical plugs, with closed base ends, couple the ends of the longitudinal cooling passages. In use, the cooling water flows in sequence through a radial cooling channel, a longitudinal cooling channel, and another radial cooling channel at the opposite end of the casting roller. In more specific terms, Figures 1 to 5 show a continuous casting machine with a described embodiment of the smelting rolls described herein. Such casting machines having cast rolls 12, whose outer diameters are greater in the central portions 17 than in the end portions 28 at the ends of the rolls. The central portions 17 comprise radially extending end surfaces. The side tanks 11 contact the end surfaces of the central portions 17 in an operative position of the casting machines. The cast rolls 12 also comprise hollow stub axles 13 which axially couple the two end portions 28. The stub axles 13 have diameters which are similar to the outer diameters of the two end portions 28 of the 12 casting rollers. The longitudinal cooling passages 14 pass through the cast rolls 12 between the radially extending end surfaces of the central portions 17 of the casting rolls 12. The longitudinal cooling passages 14 are arranged substantially equidistantly circumferentially in the cast rolls 12. In this position, the longitudinal cooling passages 14 have a good heat transfer ratio with the outer surfaces of the rollers. The radial cooling passages 15 extend radially through the cast rolls 12 from the inner circumferential surfaces of the cast rolls near the end portions 28 of the cast rolls 12 and connect to the longitudinal cooling passages 14. Consequently, the radial and longitudinal cooling passages 14, 15 form a right angle that slopes to these places. In addition, the plugs 19 with a circular plate shape close both ends of the longitudinal cooling passages 14. The plugs 19 are fixed to the cast rolls 12 by means of fastening rings 20. Materials of Seals, such as O-rings, are also used between the plugs 19 and the inner circumferential surfaces of the longitudinal cooling passages 14. As a consequence, the cooling water W is caused to continuously flow in sequence to one of the radial cooling passages 15 communicating with the longitudinal cooling passages 14, that longitudinal cooling passage 14 and the other of the cooling passages 15 radial that communicates with that passage 14 longitudinal cooling. In addition, the cylindrical spacers 31 are located in each of the radial cooling passages 15 and define the deflectors 32 that extend partially to the longitudinal cooling passages 14. The deflectors 32 are integrally provided in the main end portions of the spacers 31. The deflectors 32 are formed and positioned to project from an interior corner of the elbows defined by the longitudinal cooling passages 14, 15 outward toward the exterior corner of the elbows, with the cross-sectional area of the passages that were halved before and after the baffles 32. The stub axles 13 are hollow and include radial cooling passages 18 extending radially through the axes 13 of the stub axle so that The cooling water W may continuously flow in sequence to one of the radial cooling passages 15 communicating with the longitudinal cooling passages 14, that longitudinal cooling passage 14, and the other of the radial cooling passages 15, and rotating connections. and the like in the radial cooling passages 18. When operating the continuous casting machine, the pair of casting rolls 12, the stub axles 13 and the plugs 16 are positioned laterally to each other, and in such a way that a contact line of the casting rolls can be adjusted according to the thickness of the S band to be manufactured. In addition, the side tanks 11 contact the radially extending end surfaces of the central portions 17 of the casting rolls 12. In such a continuous casting machine, the heat is removed from the casting rolls 12 by means of cooling water W flowing through the radial cooling passages 15 and the longitudinal cooling passages 14 while the molten metal is poured into the molten metal. a space on the contact line delimited by the side tanks 11 and the casting rollers 12 to form a melt accumulation of molten metal M. While the cast rolls rotate, the metal that has been cooled by the outer circumferential surfaces of the casting rollers 12 and is formed downwardly by moving the web S to the contact line. As mentioned above, the longitudinal cooling passages 14 extend between the radially extending end surfaces of the central portions 17 of the casting rolls 12. The arrangement is such that there is a small opening T3 only between the longitudinal cooling passages 14 and the outer circumferential surfaces of the casting rolls 12, while maintaining a space of T4 between the outer surfaces of the end portions 28 and the outer surfaces. of the central 17 portions. Therefore, in use, the cooling water passing through the longitudinal passages 14 of the casting rolls 12 can effectively cool the outer circumferential surfaces of the casting rolls 12. In addition, deflectors 32 reduce by approximately half the cross-sectional area of the passages in the bends when compared to the example illustrated in Figures 14 and 15 in which deflectors 32 are not provided in the bends. Therefore, the speed of the cooling water V increases and in addition the cooling water W is directed towards the outer corners of the elbows which results in a more effective cooling of the parts of the casting rolls 12. The beneficial impact of the baffles 32 in both directions of flow is illustrated by the cooling water velocity profiles in Figures 4 and 5. Therefore, the cooling effect on the cast rolls 12 is increased in the rolls 12. of casting described above, and therefore it is possible to increase the number of revolutions of the casting rolls 12, ie, increase the casting speed and improve the production efficiency of the S-band. Figures 6 to 9 show a machine continuous casting comprising a second embodiment of the casting rolls 12, wherein those parts represented by the same symbols as in Figures 1 to 5 refer to the same objects. In this casting roll 12 a plurality of integrally formed fins 33 projecting to the longitudinal cooling passages 14 and chocked at the outlets of the radial cooling passages 15 is provided in place of the spacers 31 and deflectors 32 described above . Therefore, the cross-sectional area of the passages in the elbows defined by the intersections of the radial and longitudinal cooling passages 14, 15 is reduced approximately by half. The plurality of fins 33 is disposed circumferentially within casting rollers 12 such that it does not directly impede the flow of cooling water W, and with the leading ends of the fins forming at acute angles and with the inner corners of the elbows extending. In a continuous casting machine employing such cast rolls, the cooling water is caused to flow through the longitudinal cooling passages 14 and the radial cooling passages 15 and extracts the heat from the casting rolls 12 while the Molten metal is poured into an accumulation defined by the side tanks 11 and the casting rolls 12. The longitudinal cooling passages 14 extend between the radially extending end surfaces of the central portions 17 of the casting rolls 12. The arrangement is such that there is a small opening T3 only between the longitudinal cooling passages 14 and the outer circumferential surfaces of the casting rolls 12, while a space of T4 is maintained between the outer surfaces of the end portions 28 and the surfaces outside of the central 17 portions. Consequently, the cooling water W passes close to the outer circumferential surfaces of the cast rolls 12 and effectively cools those surfaces of the casting rolls 12. In addition, the speed of the cooling water W increases because the cross-sectional area of the passages in the elbows is reduced by approximately half when compared to the example in which the fins 33 are not provided as shown in the drawings. Figures 14 and 15 and, in addition, the heat received by the casting rollers 12 of the molten metal is transported through the plugs 19 and the fins 33 to the cooling water W, with the result that the casting rolls 12 are cooled efficiently . The beneficial impact of the fins 33 in both directions of flow is illustrated by the cooling water velocity profiles in Figures 8 and 9. Therefore, the cooling effect of the casting rolls 12 is high in the rolls 12. of casting described above, and therefore it is possible to increase the rate of rotation of the casting rolls 12, i.e., increase the casting speed and increase the production efficiency of the S-band. Figures 10 to 13 show a machine of continuous casting employing a third, but not the only one possible, mode of the casting rolls, in which those parts represented by the same symbols as in Figures 1 to 5 refer to the same objects.

This cast roller has circumferential cooling passages 34 which interconnect with the adjacent longitudinal cooling passages 14 and facilitate the flow of cooling water W that has passed through the entire length of a longitudinal cooling passage 14 to a passage 14. of adjacent longitudinal cooling. The circumferential cooling passages 34 are formed by cutting openings from the inside to the outside of the casting rolls 12 and by closing the openings in positions in proximity to the rotational axis of the casting rolls 12 by means of plugs 35 for interconnecting the two longitudinal cooling passages 14. In addition, the inserts 36 are located in the longitudinal cooling passages 14, and the cross sectional area of the passages is reduced by approximately half. The main ends of the inserts 36 are shaped to be at acute angles and elongate along the rotational axis of the casting rolls 12. In the continuous casting machine employing the casting rolls 12 described above the heat is extracted from the casting rolls 12 by causing the cooling water W to flow through the passages 14 of longitudinal cooling and radial cooling passages 15 while the molten metal is poured into the space formed by the side weirs 11 and the roller bodies 12. The longitudinal cooling passages 14 extend from a radially extending end surface in a position in which the outer radius of the casting rolls 12 expands and which is spliced by the side reservoir 11 to the other end surface that is it extends radially in a position in which the outer radius of the cast rolls 12 expands and which is spliced by the side reservoir 11. Therefore, the contact T4 between the lateral reservoir 11 and the radially extending end surface in that portion of the casting rolls 12 in which the outer radius is larger, while allowing the greatest possible reduction in the distance T3 between the longitudinal cooling passages 14 and the outer circumferential surface of the casting rolls 12. Consequently, the cooling water W passes through the surface layer of the casting rolls 12 and effectively cools the outer circumferential surface of the casting rolls 12. In addition, the speed of the cooling water W increases because the cross-sectional area of the passages in the elbows is reduced by approximately half andin addition, the cooling water W is directed to the vicinity of the outer circumferential surface of the cast rolls 12 in the elbows, with the result that the cast rolls 12 are cooled efficiently. The beneficial impact of the inserts 36 in a flow direction is illustrated by the cooling water velocity profiles in Figure 13. Therefore, the casting rolls described above allow increases in the rotation rate of the rollers 12 of casting, that is, increases in the casting speed and higher production efficiency for the S-band because the cooling effect of the casting rolls 12 is improved. The cast rollers shown herein are not limited to implementation modes described above and can of course be modified as long as such modifications do not violate the spirit of the invention. The cast rolls depicted herein can be used for the continuous casting of steel and some other metals.

Claims

CLAIMS 1. An apparatus for melting metal strip comprising: (a) a pair of laterally positioned casting rollers forming a line of contact between them, each casting roller comprising a cylindrical body with a central portion, and a plurality of cooling passages extending through the central portion, the cooling passages comprising longitudinal cooling passages, the cooling passages which also comprise at least one bend in the cooling passages which requires cooling fluid to flow to through a cooling passage to undergo a change of direction, and a flow control member located at the elbow to control the flow of cooling fluid around the elbow; and (b) a molten metal supply system for distributing molten metal over the nip between the nip rolls to form an accumulation of molten metal cast on the nip rolls immediately above the nip. The metal band melting apparatus of claim 1 wherein each casting roller comprises a radially extending end surface at each end of the central portion capable of supporting a deposit lateral, and the cooling passages extend through the central portion between the radially extending end surfaces. The metal band melting apparatus of claim 1 or claim 2 wherein the cooling passages further comprise a plurality of radial cooling passages, each radial cooling passage extending from an inner periphery of the casting roll to one of the longitudinal cooling passages at one end of the central portion, with the elbow forming where the radial and longitudinal cooling passages meet. The metal band melting apparatus of claim 3 wherein the flow control member comprises a baffle extending from an inner corner of the elbow to an outer corner of the elbow. The metal band melting apparatus of claim 3 wherein the flow control member comprises a plurality of fins extending from the end surfaces radially extending in the direction of the longitudinal cooling passage. The metal band melting apparatus of claim 1 or claim 2 wherein the cooling passages comprise at least one circumferential section that interconnects with the passages of adjacent longitudinal cooling so that the cooling fluid can flow from a longitudinal cooling passage in and then along an adjacent longitudinal cooling passage, with the elbow forming in the circumferential section. The metal band melting apparatus of claim 6 wherein the flow control member comprises an insert that partially fills the elbow and reduces the cross-sectional area of the elbow. 8. A casting roll comprising: (a) a cylindrical body having a central portion; and (b) a plurality of cooling passages extending through the central portion, the cooling passages comprising longitudinal cooling passages, the cooling passages that also comprise at least one bend in the cooling passages required of cooling fluid flowing through a cooling passage to undergo a change of direction, and a flow control member located at the elbow to control the flow of cooling fluid around the elbow. The casting roller of claim 7 wherein the cylindrical body is a stepped cylindrical body having the central portion with a first outer diameter and an end portion having a second outer diameter extending axially from each end of the central portion, and the second outer diameter which is smaller than the first outer diameter. 10. The casting roller of claim 7 or claim 8 comprises an end surface radially extending at each end of the central portion capable of supporting a side reservoir, and the cooling passages extending through the central portion between the reservoirs. extreme surfaces that extend radially. The casting roller of any of claims 7 to 9 wherein the cooling passages further comprise a plurality of radial cooling passages, each radial cooling passage extending from an inner periphery of the casting roll to one of the passages of longitudinal cooling at one end of the central portion, with the elbow forming where the radial and longitudinal cooling passages meet. The casting roller of claim 10 wherein the flow control member comprises a baffle extending from an inner corner of the elbow to an outer corner of the elbow. The casting roller of claim 10 wherein the flow control member comprises a plurality of fins extending from the end surfaces radially extending in the direction of the longitudinal cooling passage. The casting roller of claim 9 or claim 10 wherein the cooling passages comprise at least one circumferential section that interconnects with the adjacent longitudinal cooling passages so that the cooling fluid can flow from a longitudinal cooling passage inside and then along an adjacent longitudinal cooling passage, with the elbow forming in the circumferential section. The casting roller of claim 13 wherein the flow control member comprises an insert that partially fills the elbow and reduces the cross-sectional area of the elbow. 16. A method of continuous casting of thin metal strip comprising the steps of: (a) assembling a pair of laterally positioned casting rolls forming a line of contact between them, each casting roll comprising a cylindrical body with a portion central, and a plurality of cooling passages extending through the central portion, the cooling passages comprising longitudinal cooling passages, the cooling passages which also comprise at least one bend in the cooling passages requiring cooling fluid to flow through a cooling passage to undergo a change of direction, and a flow control member located at the elbow to control the flow of cooling fluid around the elbow; (b) distribute cast through a metal supply system over the nip between the cast rolls to form an accumulation of molten metal cast on the cast rolls immediately above the nip between nip rolls; and (c) conversely rotating the cast rolls to form sheets of the melt build up on the cylindrical surfaces of the cast rolls and form a thin cast strip in the nip between the cast rolls distributed downwardly. 17. An apparatus for melting metal strip comprising: (a) a pair of laterally positioned casting rollers forming a line of contact between them, each casting roll comprising a cylindrical body with a central portion and an end surface that is radially extends at each end of the central portion capable of supporting a lateral deposit, and a plurality of cooling passages extending through the central portion between the radially extending end surfaces, the cooling passages comprising longitudinal cooling passages, the cooling passages which also comprise at least one bend in the cooling passages which requires cooling fluid to flow through. a cooling passage to undergo a change of direction, and a flow control member located at the elbow to control the flow of cooling fluid around the elbow; and (b) a molten metal supply system for distributing molten metal over the nip between the cast rolls to form a molten metal melt buildup supported on the cast rolls immediately above the nip line delimited by lateral deposits located adjacent to the radially extending end surfaces.