PROCESS AND APPARATUS FOR CONTINUOUS CASTING

Abstract: Process and apparatus for continuous casting in a twin­ belt casting machine in which the moving side (12, 13) dams are guided along opposite sides of the moulding cavity by guide means extending along beside the respective moving side dams, and the moving side dams are cooled by cooling fluid circulated in at least a part of said guide means and applied directly to the moving side dams. The moving side dams are cooled by cooling fluid sprayed through orifices in said guide means directly onto the moving side dams along at least a part of the downstream zone of the moulding cavity. During movement of the side dams along the mould­ ing cavity from its entrance to its exit, they pass successive­ ly through a first (or upstream) zone (A) in which they face molten metal and through a second (or downstream) zone (B) in which they face solidified metal. The cooling fluid is sprayed directly onto the moving side dams only in this second zone. The first zone occupies from approximately 3 / 10ths to approximately 1/2 of the overall length of the mould­ ing cavity, and the second zone accupies the remainder. The cooling fluid is advantageously sprayed directly toward the side dam for providing very effective cooling action, and this cooling fluid is aimed in a downstream direction that forms an acute angle with the moving direction of the side dam. Preferably this acute angle is in the range from ap­ proximately 20° to approximately 50° for propelling the cool­ ing fluid downstream away from the first zone, and prefer­ ably the cooling fluid is water.

Description: FIELD OF THE INVENTION The present invention relates to process and apparatus for continuous casting of molten metal in a twin-belt casting machine. BACKGROUND OF THE INVENTION In a twin-belt casting machine the moulding cavity is formed by means of moving walls, the lower wall being formed by the upper run of a lower endless flexible belt, the upper wall being formed by the lower run of an upper endless flexible bet, and the side walls being formed by a pair of spaced endless side dams, that move with the belts along the opposite sides of the moulding cavity from the inlet (or entrance) to the outlet (or exit) thereof and that are guided by guide means during their movement along the moulding cavity. The lower wall and the upper wall are cooled by contact with a cooling liquid on their respective reverse surfaces. That is, the cooling liquid is applied to the lower surface of the upper run of the lower belt, and the cooling liquid is also applied to the upper surface of the lower run of the upper belt. Molten metal is fed in at the entrance of the moulding cavity, and a cast product is delivered at the outlet of the moulding cavity. Thus, the side dams pass during their movement along the moulding cavity successively through a first zone, in which they face molten metal and through a second zone located downstream from the first zone in which they face solidified metal. Such a process and apparatus are described in United States Patent No. 3,036,348. In this known process and apparatus, there is a fixed guide in the form of a guide bar extending for a substantial distance along the outer face of each side dam. This guide bar extends from the inlet towards the outlet of the moulding cavity and, during their movement along the moulding cavity, the side dams are only cooled by the contact of their upper and lower faces with the belts. As shown in Fig. 10 of that U.S. patent and as described in column 10, lines 60-70 therein, it is known in the twin-belt casting machine art to provide a longitudinal passageway in each stationary dam which rests on top of the respective moving side dam adjacent to the pool of molten metal near the entrance to the moulding cavity and to feed liquid coolant through such passageways for cooling the stationary side dams. It is also known in the twin-belt casting machine art to provide a longitudinal passageway in each guide bar and to feed liquid coolant through such a passageway for cooling the guide bar. However, such guide bars and such stationary edge dams are stationary. Prior to the present invention, the moving side dams have only been cooled by the contact of their upper and lower surfaces with the belts. Relatively insignificant cooling is provided from such a stationary side dam or from such a stationary guide bar. Consequently, in the known process and apparatus relatively few calories are carried off from the moving side dams as they move along opposite sides of the moulding cavity. Thus, the moving side dams become heated to a relatively high tem perature during their movement along the moulding cavity. Such repeated high temperature heating influences in an unfavorable way the lifetime of these side dams. This high temperature heating of the side dams also imposes limitations on the casting speed, especially when rather thick products are cast, for example, products with a thickness of five or more centimetres. SUMMARY OF THE INVENTION The aim of the present invention is to provide a process and apparatus that avoid the drawbacks of the above-known process and apparatus. According to the present invention, a cooling fluid is circulated in at least a part of the fixed guides and this cooling fluid is sprayed through the fixed guides directly onto the moving side dams in at least a part of the aforesaid second zone in which the moving side dams face solidified metal. The present invention relates to apparatus for continuous casting comprising a moulding cavity formed by means of moving walls, the lower wall being formed by the upper run of a lower endless belt, the upper wall being formed by the lower run of an upper endless belt, and the side walls being formed by a pair of endless side dams, that are adapted to move with the belts along the opposite sides of the moulding cavity from the inlet to the outlet thereof, fixed guides to guide the side dams during their movement along the moulding cavity, means for spraying a cooling liquid on the reverse surfaces of the lower wall and upper wall, and a first zone, in which the side dams face liquid metal when the apparatus is running, and a second zone, in which the side dams face solidified metal when the apparatus is running, characterized in that the fixed guides are adapted to be cooled over at least a part of their length by circulation of a cooling fluid and they comprise means for spraying cooling fluid directly onto the moving side dams in at least a part of the aforesaid second zone. In the illustrative embodiment of the invention, as shown, the cooling fluid is advantageously sprayed directly toward the respective side dam for providing a very effective cooling action on the side dam as it is moving along the moulding cavity in the second zone facing the recently solidified metal, and the cooling fluid is aimed in a downstream direction for propelling the cooling fluid downstream away from the first zone in which the moving side dams face molten metal. Other details and characteristics of the invention will result from the description of an embodiment of the process and apparatus according to the invention, given hereafter as a non-restrictive example and with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 - is a schematic elevational lateral view of a twin-belt continuous casting apparatus according to the invention. Fig. 2 - represents an enlarged section through the apparatus of Fig. 1 made along line Il-Il of Fig. 1. Fig. 3 - represents an enlarged section through the apparatus of Fig. 1 made along line III-III of Fig. 1. Fig. 4 - is an enlarged and more detailed view of part of Fig. 2. Fig. 5 - is an enlarged and more detailed view of part of Fig. 3. Fig. 6 - represents an enlarged horizontal section through a fixed guide of the apparatus of Fig. 1. The same reference notations indicate identical elements in the different figures. The apparatus shown in Figs. 1 to 3 comprises an upper moving endless belt 1 and a lower moving endless belt 2. The upper belt 1 passes around rolls 3 and 4, and the lower belt 2 passes around rolls 5 and 6. Rolls 3 and 5 are driven in the direction indicated by arrows 10 and 11 and consequently drive belts 1 and 2 in the direction of arrows 9 and rolls 4 and 6 in the direction of arrows 7 and 8. Two moving endless side dams 12 and 13 are located partly between the lower run of the upper belt 1 and the upper run of the lower belt 2. The side dams 12 and 13 delimit with upper belt 1 and with the lower belt 2 a moulding cavity 14 between an inlet or entrance 15 and an outlet or exit 16. The movement of belts 1 and 2 causes the side dams 12 and 13 to move. These side dams move thus with belts 1 and 2 in the direction of arrows 9 from inlet 15 to outlet 16 of the moulding cavity 14. The side dams 12 and 13 are formed by a metal strap 17 and by a large number of metal blocks 18 strung on this strap. When moving along the moulding cavity 14, the side dams 12 and 13 are guided by fixed guides 19 and 20 in order to avoid their sidewards movement toward the outside which would make the profile of the cast product irregular. The construction of fixed guides 19 and 20 will be described and more detailed further on. The casting apparatus is supplied with molten metal by conventional metal feeding apparatus (not shown) feeding the moulding cavity 14 with molten metal. This feeding apparatus is located at inlet 15 of the moulding zone between side dams 12 and 13. The metal is cooled in the moulding cavity 14 on the one hand by spraying a cooling liquid on the reverse surfaces of belts 1 and 2, respectively, as schematically illustrated at 21 and 22, as detailed in the aforesaid U.S. Patent No. 3,036,348, and on the other hand by spraying a cooling liquid on side dams 12 and 13, as will be described further on. At outlet 16 of moulding cavity 14 the cast product issues in the shape of a strip or bar, that is either entirely solidified or is composed of a solidified metal sheath or skin enclosing a liquid metal core. The thickness of this strip or bar is determined by the distance between belts 1 and 2,and the width by the distance between the side dams 12 and 13. Side dams 12 and 13 thus pass, during their movement, along the moulding cavity 14, successively through a first zone, for example, zone A, in which they face molten metal and through a second zone, for example, zone B, in which they face solidified metal. The length of the first zone A depends on a number of factors such as the nature and temperature of the cast metal, the section that is cast, the inclination of the moulding cavity, the nature of the walls of the moulding cavity, the intensity of the applied cooling, the casting speed, etc. This length of zone A can be computed for each case in particular. Normally the length of zone A is in the range from approximately 3/l0ths to approximately 1/2 of the overall length of the moulding cavity 14. Preferably, the casting operation is carried out under such conditions that this length of zone A amounts to about three to four tenths of the length of the moulding cavity, which means that the second zone B normally extends over at least the second half of the moulding cavity 14, and preferably extends over approximately 6/lOths to approximately 7/l0ths of the total length of the moulding cavity. the Rolls 5 and 6 as well asicooling system 22 of the lower belt 2 are mounted on a lower frame 23, and rolls 3 and 4 and the cooling system 21 of the upper belt 1, on the upper frame 24. The lower frame 23 and the upper frame 24 are spaced by a certain number of spacers 25, passing through two tightening or adjusting elements 26 und 27 and serving for keeping these elements in position. Rods 28, which enable the adjustment of the position of the fixed guides 19 and 20, pass through the tightening elements 26 and 27. For clarity of illustration frames 23 and 24, spacers 25, tightening elements 26 and 27, and regulating rods 28 are not shown in Fig. 1. Figures 4 to 6 give a detailed view of the construction of the guide 19. This guide 19 is essentially composed of the following elements: a U-section 29; a flat section 30 welded at 31 to the legs of the U-section 29; a rectangular section 32 fixed by screws 33 (Fig. 6) to the flat section 30 on the end portion of the guide 19 nearer the inlet 15 of the moulding cavity 14; a U-section 34 fixed by screws 35 to the flat section 30 on the end portion of the guide 19 nearer the outlet 16 of the moulding cavity 14; a plate 36 closing section 29 on the upstream end of the guide 19 located near to the inlet 15; a plate 37 closing section 29 on the downstream end of the guide 19 located near to the outlet 16; a wall 38 separating a cavity 39 of section 29, that faces section 32, from a cavity 40 of section 29, that faces section 34; and a lug 41 to attach the guide to the lower frame 23. Moreover, there is a fluid supply port or opening 42 provided in the downstream end plate 37 and a series of fluid spray openings 43 provided in the wall formed by the- juxtaposition of section 34 and flat section 30. Seen from inlet 15 of moulding cavity 14, the openings 43 are each directed at an acute angle C towards the downstream moving direction 9 of the side dams 12 and 13, preferably at an angle C of approximately 200 to approximately 500. When the casting apparatus is in operation, a cooling fluid, preferably such as water, is introduced through the supply opening 42 in cavity 40, from where it sprays out through the openings or orifices 43 in the direction of side dam 12, thereby being directly applied onto the moving side dam 12 along at least a portion of the second zone B of the moulding cavity 14. By virtue of the fact that the fluid spray openings or orifices 43 are directed downstream at the angle C, the fluid is propelled in a downstream direction away from the first zone A in which the side dam faces molten metal. The fixed guide 19 as shown in Fig. 6 thus comprises a first upstream part, that is not adapted to spray cooling fluid on side dam 12 and that extends over at least zone A, and a second downstream part, that is adapted to spray cooling fluid on side dam 12 and that extends over at least a part of zone B. In the illustrative example both parts are shown as having almost the same length. It is to be understood that a cooling liquid such as water must not be sprayed on the moving side dam 12 in zone A, where the side dam still faces liquid metal, since the water might reach this liquid metal, thereby causing the explosively sudden disruptive generation of steam. In order to obtain the most effective cooling of the moving edge dam 12, it is desired that the portion of the length of the zone B along which the liquid coolant is directly applied to the moving-edge dam by the spray opening 43 in the guide 19 preferably be as large as possible. Thus, it is quite important that, in the application of the process and apparatus of this invention, there be an effective control of the liquid metal level at inlet 15 of the moulding cavity 14 for controlling the length of the first zone A for preventing the zone A from extending downstream beyond a predetermined limit 44. As shown in Fig. 6, said predetermined limit 44 is always located upstream from the most upstream one of the spray openings 43. Such control can be made by the process and apparatus described in U.S. Patent No. 4,276,921. It is to be understood that the other guide 20 is constructed like the guide 19, except it is a mirror image of the guide 19. The U-section 34 of the guide 19 defines a channel, as seen in Fig. 3, adjacent to the outside surface of the side dam 12. Similarly, the corresponding U-section of the other guide 20 defines a channel adjacent to the outside surface of the other side dam 13. The spray openings 43 are aimed toward the outside surfaces of the respective side dams 12,13 along these channels. These channels are open at their downstream ends, as seen in Fig. 6, for allowing the cooling fluid which has been applied to the side dams to escape near the outlet or exit 16 (Fig.1). As described above, the downstream angle C of the multiple spray openings 43 propels the cooling fluid in a downstream direction toward the open end of this channel as shown by the arrow 45 in Fig. 6. Moreover, it is to be understood that numerous variants of the afore-described guide 19 can be used in the process and apparatus of this invention. So, for example, it is possible to include such modifications as the following: Eliminate the wall 38 so that the cooling fluid might also circulate in the cavity 39. Eliminate the wall 38 and provide in the end plate 36 an outlet opening, with a small diameter (smaller than the size of the supply port 42), for the cooling fluid circulating in cavity 39 to exit. Eliminate the wall 38 and the opening 42 and provide in the end plate 36 a supply opening for the introduction of the cooling fluid. Replace section 32 by a hollow section and make the cooling fluid circulate in the cavity of this section, etc. It should be noted that when casting a copper bar with a thickness of 70 mm and a width of 130 mm, the direct cooling of the side dams in zone B through the fixed guides, as shown in Figs. 4 to 6, advantageously allowed the casting speed to be increased by approximately 10%; in other words, the tonnage production per hour of such copper bar was increased by approximately 10%.

Claims: Claims 1. A process for continuous casting according to which a moulding cavity is formed by means of moving walls, the lower wall being formed by the upper run of a lower endless belt, the upper wall being formed by the lower run of an upper endless belt and the side walls being formed by a pair of endless side dams, that move with the belts along the moulding cavity from the inlet to the outlet thereof and that are guided by fixed guides during their movement along the moulding cavity, the lower wall and the upper wall are cooled by contact with a cooling liquid, and mol ten metal is fed at the inlet of the moulding cavity and a cast product is delivered at the outlet of the moulding cavity, the side dams thus passing during their movement along the moulding cavity successively through a first zone, in which they face molten metal and through a second zone, in which they face solidified metal, this process being characterized in that: a cooling fluid is circulated in at least a part 40 of the fixed guides 19,20,and cooling fluid is sprayed through the fixed guides on the side dams 12,13 in at least a part of the afore said second zone B. 2. The process according to claim 1, characterized in that: the cooling fluid is sprayed through the fixed guides onto the moving side dams 12,13 after the moving side dams have travelled through approximately 1/3 to approximately 1/2 of the length A + B of the moulding cavity 14, and thereafter is sprayed onto the moving side dams until the moving side dams reach the outlet 16 of the moulding cavity. 3. The process according to claim 1 or 2, characterized in that the cooling fluid is sprayed through the fixed guides in a direction that, seen from the inlet of the moulding cavity forms an acute angle C with the moving direction 9 of the side-dams 12,13. 4. The process according to claim 3, characterized in that the acute angle C is in the range between approximately 20 to approximately 509. 5. The process according to anyone of claims 1 to 4, charac terized in that water is used as the cooling fluid di rectly sprayed onto the moving side dams 12,13 6. The process according to anyone of claims 3 to 5, charac terized in that each fixed guide 19,20 defines a channel 34 adjacent to the outside surface of the respective moving side dam 12 or 13 along the major portion of said second zone B, said channel being open at its downstream end near the outlet 16 of the moulding ca vity 14,the cooling fluid is sprayed onto the outside surface of the moving side dam at multiple locations 43 along said channel, and said acute angle C propels the fluid coolant along said channel toward the open downstream end 45 thereof. 7. A process for continuous casting molten metal wherein a moulding cavity is formed between two moving endless belts which respectively form the upper and lower walls of the moulding cavity and the side walls are formed by a pair of endless side dams that move with the belts along the moulding cavity from the inlet to the outlet thereof, the upper and lower walls being cooled by con tact with a cooling liquid, and molten metal is intro duced into the inlet and a product is discharged from the outlet which is solidfied at least on the outside thereof, the side dams thus passing during their move ment along the moulding cavity successively through a first zone in which they face molten metal and a se cond zone in which they face solidified metal, this process being characterized by directly applying cooling liquid against the moving side dams as they travel along at least a portion of the second zone B in which they face solidified metal. 8. The process according to claim 7, characterized in that the cooling liquid is sprayed directly against the out side surface of each moving side dam 12,13 at multiple spray locations 43 spaced along the major portion of said second zone B. 9. The process according to claim 7 or 8, characterized in that the cooling liquid is sprayed directly against the outside surface of each moving side dam 12,13 while being aimed in the downstream direction at an acute angle C for propelling the cooling fluid downstream toward the outlet 16 of the moulding cavity 14. 10.Continuous casting apparatus including a moulding cavity formed by means of moving walls, the lower wall being formed by the upper run of a lower endless belt, the upper wall being formed by the lower run of an upper endless belt, and the side walls being formed by a pair of endless side dams, that are adapted to move with the belts along the moulding cavity from the in let to the outlet thereof, fixed guides to guide the side dams during their movement along the moulding ca vity, means for applying a cooling liquid on the re verse surfaces of the lower and upper walls, and a first zone, in which the side dams face liquid metal when the apparatus is running, and a second zone, in which the side dams face solidified metal when the appa is running, said apparatus ratusrbeing characterized in that the fixed guides 19,20 are adapted to be cooled over at least a part of their length by circulation of a cooling fluid and they comprise means 34,43 for spraying cooling fluid on the side dams 12,13 in at least a part of the aforesaid second zone B. 11. Apparatus according to claim 10, characterized in that the means for spraying the cooling fluid on the side dams comprise openings 43 provided in the guides 19, 20. 12. Apparatus according to claim 10 or 11, characterized in that the means for spraying the cooling fluid on the side dams extend over at least 1/2 of the length A + B of the moulding cavity 14 along the downstream portion B thereof. 13. Apparatus according to claim 10 or 11, characterized in that the means for spraying the cooling fluid on the side dams are adapted to spray liquid coolant in a direction that , seen from the inlet 15 of the moulding cavity 14, forms an acute angle C with the moving direction 9 of the side dams 12,13. 14. Apparatus according to claim 13, characterized in that the acute angle C is in the range between approximate ly 200 and approximately 500. 15. Continuous casting apparatus for casting molten metal wherein a moulding cavity is formed between two moving belts which respectively form the upper and lower walls of the moulding cavity, and the side walls are formed by a pair of endless side dams that move with the belts along the moulding cavity from the inlet to the outlet thereof, the upper and lower walls being cooled by liquid coolant, and molten metal being introduced into the inlet and a product is discharged from the out let which is solidified at least on the outside there of, the side dams thus passing during their movement along the moulding cavity successively through a first zone in which they face molten metal and a second zone in which they face solidified metal, said apparatus comprising guide means 19,20 extending along adjacent to the outside of the respective moving side dam 12, 13 for guiding the moving side dam along the moulding cavity 14 and defining a channel 34 adjacent to the outside surface of the moving side dam along at least a portion of said second zone B, and means 41 43 for applying liquid coolant directly onto the moving side dams along said channel 34. 16. Continuous casting apparatus according to claim 15 in which said means for applying liquid coolant direct ly onto the moving side dams includes a plurality of spray openings 43 spaced along said channel 34 and aimed toward the outside surface of the moving side dam 12 or 13 along the respective channel 34 for spray ing the liquid coolant directly onto the outside sur face of the moving side dam. 17. Continuous casting apparatus according to claim 16, in which said channel 34 is open at its downstream end 45, and said spray openings 43 are aimed in the downstream direction at an acute angle C toward the outside surface of the moving side dam 12,13 for pro pelling the applied coolant in the downstream direc tion toward the open end of said channel.

Inventors: DOMPAS, JOHN M. A., MORTIER, RENE E. J., RASKIN, CHRISTIAN L. G., VANELDEREN, YVON L., Mortier, René E. J.
Applicants: HAZELETT STRIP-CASTING CORPORATION
Application year: 1983
Main classification: B22D11
IPC codes: B22D11