초록 ▼

The casting belt is preheated with steam closely ahead of the entrance to the casting zone by providing wrap-around steam feed tubes having nozzles, such tubes being positioned in very deep circumferential grooves in input pulley or nip pulley which moves the casting belt into the input end of the c

The casting belt is preheated with steam closely ahead of the entrance to the casting zone by providing wrap-around steam feed tubes having nozzles, such tubes being positioned in very deep circumferential grooves in input pulley or nip pulley which moves the casting belt into the input end of the casting zone. These circumferential grooves of the input or nip pulley also house wrap-around liquid coolant feed tubes for cooling the casting belt near the beginning of the casting zone. The wrap-around steam feed tubes also have radial ports positioned to direct steam toward the reverse side of the endless belt, with the port being spaced from the nozzle thereby providing a staged elevation of temperature in the flexible casting belt on the input or nip pulley, while the belt is in contact therewith before the belt reaches the casting zone. Elevating the temperature prior to the endless belt reaching the casting zone and then suddenly cooling the belt when the molten metal is applied thereto improves casting conditions in the operation of such thin, flexible casting belt and enhances and speeds up the casting process. There are several ways for preventing coolant water from cooling the steam header and tubes of the bottom nip pulley in a twin-belt machine.

대표청구항 ▼

1. In the continuous casting of molten metal wherein the molten metal is contained and moved along in a casting zone having an input end and an output end by at least one thin, flexible endless casting belt, said output end of said casting zone being downstream from said input end of said casting zo

1. In the continuous casting of molten metal wherein the molten metal is contained and moved along in a casting zone having an input end and an output end by at least one thin, flexible endless casting belt, said output end of said casting zone being downstream from said input end of said casting zone, said casting belt having a front surface carrying said molten metal in said casting zone and having a reverse surface and wherein the casting belt travels partially around curved guide means adjacent to the input end of the casting zone with the reverse surface of the belt being curved concave where the belt travels around said guide means, the improved method of preheating the casting belt before it reaches the input end of the casting zone comprising the steps of: providing said guide means with deep circumferential grooves adjacent to said curved reverse surface of the casting belt, conducting steam along confining passages within said deep grooves, impinging first jets of steam directed radially outwardly from said confining passages in said deep grooves against the reverse surface of the belt for producing a first stage of elevation of the belt temperature before the belt reaches said input end of said casting zone, said first jets of steam being located upstream of the input end of the casting zone by an angular distance of at least 45° defined by the arc of a 45 degree angle as measured from said first jets to the input end of said casting zone with an axis of curvature of said guide means defining the apex of said angle, impinging second jets of steam aimed downstream from said confining passages in said deep grooves contacting the reverse surface of the belt with the steam in said second jets travelling downstream for producing a second stage of elevation of the belt temperature following said first stage of elevation of the belt temperature in front of the position where the belt reaches said input end of said casting zone and for creating a downstream flow of steam in said deep grooves travelling downstream toward the input end of said casting zone, said second jets of steam being angularly spaced downstream by a second angular distance of at least 20° from said first jets, conducting coolant liquid along other confining passages within said deep grooves, and impinging jets of liquid coolant aimed downstream from said deep grooves striking the reverse surface of the belt at an angle of incidence less than 25° near to the input end of the casting zone and travelling downstream along the reverse surface of the belt as the belt enters the casting zone. 2. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 1 further comprising: directing said first jets of steam radially outwardly impinging perpendicularly against the reverse surface of the casting belt for producing a sudden increase in temperature. 3. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 2 further comprising: directing said second jets of steam at an angle of incidence of less than 10° toward the reverse surface of the casting belt with the steam travelling along near the reverse surface of the belt in a direction generally toward the casting zone. 4. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 1 including the steps of: providing a significantly greater volume of steam in said second jets than in said first jets for boosting the belt temperature to a higher temperature level during the second stage of preheating than during the first stage. 5. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 1, in which: said first angular distance is in the range of 45° to 90°. 6. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 5, in which: said second jets of steam are angularly spaced by a second angular distance in front of the input to the casting zone, said second angular distance being in the range of 20° to 45°. 7. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 1, further comprising: supplying said steam at a pressure of at least 5 p.s.i. above atmospheric pressure. 8. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 7, further comprising: superheating said steam to a temperature in the range from 200° F. to 600° F. above the temperature of saturated steam at said supply pressure. 9. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 1 including the steps of: impinging additional jets of steam directed outwardly from said deep grooves against the reverse surface of the belt for producing an initial stage of elevation of the belt temperature ahead of said first jets, said additional jets of steam being located upstream from said first jets by an angular distance of at least 20°. 10. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 5, including the step of: supplying said steam at a pressure of at least 5 p.s.i. above atmospheric pressure. 11. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 1, including the steps of: wiping the liquid coolant from said deep grooves, and keeping the wipe-removed coolant away from cooling relationship with respect to the steam supply. 12. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 1, wherein said curved guide means is a pulley rotating about its axis of curvature, said pulley having said deep circumferential grooves, and including the further steps of: conducting coolant water along confined passages within said deep grooves on the opposite side of the pulley axis from the steam, providing hook-shaped means for suddenly reversing the direction of coolant flow in a position in said deep grooves slightly ahead of the input end of the casting zone, and discharging the suddenly-reversed coolant in a direction toward the reverse surface of the casting belt for impinging against said reverse surface close to the input end of said casting zone of said angle of incidence less than 25° and flowing along the reverse surface of the belt toward the casting zone. 13. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 12, including the step of: supplying said steam at a supply pressure of at least 5 p.s.i. above atmospheric pressure. 14. In the continuous casting of molten metal, the improved method of preheating the casting belt as claimed in claim 12, including the steps of: wiping the liquid coolant from said deep grooves, and channeling the wipe-removed coolant away from cooling relationship with respect to the supply steam. 15. In a machine for continuously casting molten metal wherein at least one thin, endless, flexible casting belt having a front face and a reverse face revolves around pulleys and passes along a casting zone having an input end and an output end, said output end of the casting zone being downstream from said input end, said belt moving along said casting zone from the input end to the output end of the casting zone for carrying the metal being cast against the front face of the casting belt through said casting zone, apparatus for preheating said casting belt with steam comprising: an input pulley for moving said casting belt into the input end of said casting zone, said input pulley having circumferential grooves therein underlying the reverse face of said casting belt as said casting belt revolves partially around said input pulley in moving toward and into the input end of the casting zone, wrap-around steam feed tubes each having a nozzle on the end thereof, said steam feed tubes and nozzles being positioned in the respective circumferential grooves of said input pulley, said steam feed tubes each having radial steam ports aimed toward the reverse face of the casting belt for applying steam from said radial ports to the reverse face of said endless belt near to the input end of the casting zone for preheating said belt before said belt enters the input end of said casting zone, said radial steam ports being located upstream of the input end of the casting zone by a first angular distance of at least 45° defined by an angular arc as measured from said first jets to the input end of said casting zone with an axis of rotation of said input pulley defining the apex of said angle, said nozzles being located downstream from said radial ports by a second angular distance of at least 20° from said radial ports, said second angular distance being defined by an angular arc as measured from said radial ports with said axis of rotation defining the apex thereof, and said nozzles being aimed downstream for applying steam travelling downstream from said nozzles impinging against the reverse face of the belt nearer to the input end of the casting region than said radial ports for producing a second stage of preheating said belt before the belt reaches said input end of the casting zone, said two stages of steam preheating reducing belt distortion caused by the tremendous heating effect of the molten metal for thereby enabling the speed of the casting machine to be increased. 16. In a machine for continuously casting molten metal, the apparatus as claimed in claim 15 in which: each of said wrap-around steam feed tubes has a radial port positioned to direct steam toward the reverse face of said endless belt, each such port being spaced from the respective nozzle on the respective steam feed tube. 17. In a machine for continuously casting molten metal, the apparatus as claimed in claim 15 including: wrap-around liquid coolant feed tubes one of which is positioned in each of said circumferential grooves with a wrap-around steam feed tube, said wrap-around liquid coolant feed tubes each having a nozzle positioned to direct a steam of liquid coolant on the reverse face of said endless belt near the location where said endless belt enters the input end of said casting zone. 18. In a machine for continuously casting molten metal, the apparatus as claimed in claim 15 including: wrap-around liquid coolant feed tubes one of which is juxtapositioned in each of said circumferential grooves of said input pulley with a steam feed tube, each of said coolant feed tubes having a nozzle which is positioned ahead of the nozzle of the juxtapositioned steam feed tube in the respective circumferential grooves, whereby said steam feed tubes preheat said belt prior to its entry into said casting zone and said liquid coolant feed tubes cool said endless belt as it enters said casting zone and comes into contact with the molten metal. 19. In a machine for casting molten metal, the apparatus as claimed in claim 15 having: a reverse-wrap liquid coolant feed tube positioned in each of said circumferential grooves of said input pulley, each of said reverse-wrap coolant feed tubes having a hook nozzle on the end thereof for suddenly reversing the direction of the coolant prior to issuing from said hook nozzle for impinging on the reverse face of said endless belt near the input end of said casting zone and flowing in a direction generally toward said casting zone. 20. In a machine for casting molten metal, the apparatus as claimed in claim 17, having: a flexible, bladed wiper shield positioned in and conforming to the configuration of said circumferential grooves, for wiping liquid coolant away from said circumferential grooves and for preventing the removed coolant from coming into contact with said steam tubes. 21. In a machine for casting molten metal, the apparatus as claimed in claim 17, having: a steam supply header and a coolant supply header, said coolant feed tubes being connected to said coolant header and said steam feed tubes being connected to said steam header. 22. In a machine for continuously casting molten metal, the apparatus as claimed in claim 16, in which: each of said radial ports is positioned at an angular distance at least 20° upstream of the nozzle on the respective steam feed tube. 23. In a machine for continuously casting molten metal, the apparatus as claimed in claim 16, in which: each of said radial ports is positioned at a first angular distance from the input end of the casting zone in the range of 45° to 90°. 24. In a machine for continuously casting molten metal, the apparatus as claimed in claim 21, having: a flexible wiper shield conforming with the configuration of said circumferential grooves and being positioned in said circumferential grooves and overlying said steam header for preventing coolant from falling directly on said steam header as well as wiping coolant away from said circumferential grooves. 25. In a machine for continuously casting molten metal, the apparatus as claimed in claim 24 in which: said wiper shield comprises a one-piece stiffly flexible molded scrapper. 26. In a machine for continuously casting molten metal, the apparatus as claimed in claim 24 in which: said wiper shield has a rigid back-up support, and an air supply is directed on said wiper shield and into said grooves for assisting said wiper shield in removing coolant from said grooves. 27. In a machine for continuously casting molten metal, the apparatus as claimed in claim 26 having: a second wiper shield extending into said grooves below said other wiper shield and said air supply, thereby providing a confined region between said shield for said air supply for requiring less air to assist in removal of coolant from said grooves. 28. In a machine for continuously casting molten metal, the apparatus as claimed in claim 19 having: a wiper shield extending into and conforming with the shape of said circumferential grooves in said input pulley, said wiper shield being finger-shaped with the fingers thereof extending under and beyond the end of the respective hook nozzles. 29. In a machine for continuously casting molten metal, the apparatus as claimed in claim 19 having: a steam supply header to which said steam feed tubes are connected and a coolant supply header to which said liquid coolant feed tubes are connected, a wiper shield positioned on the underside of said liquid coolant feed tubes but overlying said steam header for removing coolant from said grooves and for preventing coolant from falling directly onto said steam header or steam feed tubes.