Method for casting metal strip with crown control

Abstract

A method and apparatus of continuously casting thin strip by controlling roll crown is provided. The apparatus for continuously casting thin strip by controlling roll crown includes at least two expansion rings positioned within and adjacent a cylindrical tube and spaced within 450 mm of edge portions of the cast strip formed on opposite end portions of casting rolls during a casting campaign. Alternatively or in addition, the apparatus includes at least one expansion ring within the cylindrical tube at a position corresponding to center portions of the cast strip formed on the casting rolls during a casting campaign. Each expansion ring has at least one heating element and an insulating coating thereon and is adapted to increase in radial dimension causing the cylindrical tube to expand changing roll crown of the casting surfaces of the casting rolls and thickness profile of the cast strip during casting.

1 - 28 . (canceled) 
     
     
         29 . An apparatus for continuously casting thin strip by controlling roll crown comprising:
 a pair of counter rotating casting rolls with a nip there between capable of delivering cast strip downwardly from the nip, each casting roll having a casting surface formed by a cylindrical tube having thickness of no more than 80 millimeters of a material selected from the group consisting of copper and copper alloy, optionally with a metal or metal alloy coating thereon, and having a plurality of longitudinal water flow passages extending through the cylindrical tube;   at least two expansion rings positioned within and engaging the cylindrical tube and spaced within 450 mm of edge portions of the cast strip formed on opposite end portions of the casting rolls during a casting campaign, each expansion ring having an insulating coating where the expansion ring engages the cylindrical tube, at least one heating element, and an expansion ring temperature sensor, wherein a thickness of the insulating coating is selected such that, when the heating elements are operated and cooling water flows through the longitudinal water flow passages, the expansion rings generate a temperature difference between the expansion ring and the cylindrical tube sufficient for the expansion rings to expand and cause the cylindrical tube to expand changing roll crown of the casting surfaces of the casting rolls and thickness profile of the cast strip during casting;   a metal delivery system positioned above the nip and capable of forming a casting pool supported on the casting surfaces of the casting rolls with side dams adjacent ends of the nip to confine the casting pool;   a thickness profile sensor positioned downstream of the nip; and   a control system operatively connected to receive signals from the expansion ring temperature sensors and the thickness profile sensor and configured to vary power applied to the heating element in response to expansion ring temperatures and cast strip thickness profile.   
     
     
         30 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 29  further comprising:
 at least one sensor capable of sensing at least one of the following properties: 
 local thickness of the cast strip at a defined spot close to the cast strip edges; 
 casting roll surface crown during the casting campaign; 
 radial casting roll expansion at a defined spot close to the cast strip edges; 
 and capable of generating digital or analog signal or signals indicative of at least one of the above properties to further control radial dimension of the expansion rings responsive to the signals received from the at least one sensor to control the roll crown of the casting surfaces of the casting rolls during the casting campaign. 
 
     
     
         31 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 29  further comprising:
 at least one expansion ring within the cylindrical tube corresponding to center portions of the cast strip formed on the casting rolls during the casting campaign, each expansion ring having an insulating coating where the expansion ring engages the cylindrical tube, at least one heating element, and an expansion ring temperature sensor, wherein a thickness of the insulating coating is selected such that, when the heating element is operated and cooling water flows through the longitudinal water flow passages, the expansion ring generates a temperature difference between the expansion ring and the cylindrical tube sufficient for the expansion ring to expand and cause the cylindrical tube to expand changing roll crown of the casting surfaces and thickness profile of the cast strip during casting. 
 
     
     
         32 . (canceled) 
     
     
         33 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 30  wherein the control system is further capable of controlling casting roll drive and varying the speed of rotation of the casting rolls while varying the radial dimension of the expansion rings with an insulating coating thereon and spaced from the edge portions of the cast strip responsive to electrical signals received from the at least one sensor to control the roll crown of the casting surfaces of the casting rolls during the casting campaign. 
     
     
         34 . (canceled) 
     
     
         35 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 29  where each expansion ring with an insulating coating thereon and spaced from the edge portions of the cast strip has an annular dimension between 50 and 150 mm. 
     
     
         36 . (canceled) 
     
     
         37 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 29  where each expansion ring with an insulating coating thereon and spaced from the edge portions of the cast strip has a width of up to 200 mm. 
     
     
         38 . (canceled) 
     
     
         39 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 29  where each expansion ring with an insulating coating thereon and spaced from the edge portions of the cast strip provides a heating input of up to 30 kW. 
     
     
         40 . (canceled) 
     
     
         41 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 29  where the radial dimension of each expansion ring with an insulating coating thereon and spaced from the edge portions of the cast strip can be controlled independently to control the roll crown of the casting surfaces of the casting rolls. 
     
     
         42 . (canceled) 
     
     
         43 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 29  wherein the heating elements are made of stainless steel, nickel or nickel alloy. 
     
     
         44 . (canceled) 
     
     
         45 . An apparatus for continuously casting thin strip by controlling roll crown comprising:
 a pair of counter rotating casting rolls with a nip there between capable of delivering cast strip downwardly from the nip, each casting roll having a casting surface formed by a cylindrical tube having thickness of no more than 80 millimeters of a material selected from the group consisting of copper and copper alloy, optionally with a metal or metal alloy coating thereon, and having a plurality of longitudinal water flow passages extending through the cylindrical tube;   at least one expansion ring within the cylindrical tube at a position corresponding to center portions of the cast strip formed on the casting rolls during a casting campaign, the at least one expansion ring having an insulating coating where the expansion ring engages the cylindrical tube, at least one heating element, and an expansion ring temperature sensor, wherein a thickness of the insulating coating is selected such that, when the heating element is operated and cooling water flows through the longitudinal water flow passages, the expansion ring generates a temperature difference between the expansion ring and the cylindrical tube sufficient for the expansion ring to expand and cause the cylindrical tube to expand changing crown of the casting surfaces and thickness profile of the cast strip during casting;   a metal delivery system positioned above the nip and capable of forming a casting pool supported on the casting surfaces of the casting rolls with side dams adjacent ends of the nip to confine the casting pool;   a thickness profile sensor positioned downstream of the nip; and   a control system operatively connected to receive signals from the expansion ring temperature sensor and the thickness profile sensor and configured to vary power applied to the heating element in response to expansion ring temperature and cast strip thickness profile.   
     
     
         46 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 45  further comprising:
 at least one sensor capable of sensing at least one of the following properties: 
 local thickness of the cast strip at a defined spot close to the cast strip center; 
 casting roll surface crown during the casting campaign; 
 radial casting roll expansion at a defined spot close to the cast strip center, 
 and capable of generating digital or analog signal or signals indicative of at least one of the above properties to further control radial dimension of the at least one expansion ring responsive to the signals received from the at least one sensor to control the roll crown of the casting surfaces of the casting rolls during the casting campaign. 
 
     
     
         47 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 46  wherein the control system is further capable of controlling casting roll drive and varying the speed of rotation of the casting rolls while varying the radial dimension of the at least one expansion ring responsive to electrical signals received from the at least one sensor to control the roll crown of the casting surfaces of the casting rolls during the casting campaign. 
     
     
         48 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 45  wherein the at least one expansion ring with an insulating coating thereon corresponding to center portions of the cast strip has an annular dimension between 50 and 150 mm. 
     
     
         49 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 45  wherein the at least one expansion ring with an insulating coating thereon corresponding to center portions of the cast strip has a width of up to 200 mm. 
     
     
         50 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 45  wherein the at least one expansion ring with an insulating coating thereon corresponding to center portions of the cast strip provides a heating input of up to 30 kW. 
     
     
         51 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 45  wherein each expansion ring with insulating coating thereon corresponding to the center portions of the cast strip can be controlled independently to control the roll crown of the casting surfaces of the casting rolls. 
     
     
         52 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 45  further comprising water passages in the at least one expansion ring, wherein water can flow through said water passages, and controlling said water flow regulates the expansion of the at least one expansion ring. 
     
     
         53 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 45  wherein the at least one heating element is made of stainless steel, nickel or nickel alloy. 
     
     
         54 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 29 , wherein the insulating coating is at least 0.010 inch thick. 
     
     
         55 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 45 , wherein the insulating coating is at least 0.010 inch thick. 
     
     
         56 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 29 , wherein the insulating coating comprises Yttria stabilized Zirconia. 
     
     
         57 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 45 , wherein the insulating coating comprises Yttria stabilized Zirconia. 
     
     
         58 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 29 , further comprising water passages in each of the at least two expansion rings, wherein water can flow through said water passages, and controlling said water flow regulates the expansion of the at least two expansion rings.