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.

What is claimed is: 
     
         1 . A method of continuously casting thin strip by controlling roll crown comprising the steps of:
 a. assembling a caster having 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;   b. positioning at least two expansion rings within and adjacent 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 at least one heating element and an insulating coating thereon and 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;   c. assembling a metal delivery system capable of forming a casting pool supported on the casting surfaces of the casting rolls above the nip with side dams adjacent to the ends of the nip to confine the casting pool; and   d. controlling the radial dimension of the expansion rings responsive to at least one of digital or analogous signal received from at least one sensor to control the roll crown of the casting surfaces of the casting rolls during the casting campaign.   
     
     
         2 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 1  further comprising the step of:
 e. positioning at least one sensor capable of sensing at least one of the following properties:
 temperature of the expansion rings; 
 thickness profile of the cast strip downstream; 
 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 generating digital or analogous signal or signals indicative of at least one of the above mentioned properties of the cast strip. 
     
     
         3 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 1  further comprising the step of:
 e. positioning at least one expansion ring within the cylindrical tube corresponding to center portions of the cast strip formed on the casting rolls during casting, each expansion ring having at least one heating element and an insulating coating thereon and adapted to increase in radial dimension causing the cylindrical tube to expand changing the crown of the casting surfaces of the casting rolls and thickness profile of the cast strip during casting. 
 
     
     
         4 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 2  further comprising the step of:
 f. positioning at least one expansion ring within the cylindrical tube corresponding to center portions of the cast strip formed on the casting rolls during casting, each expansion ring having at least one heating element and an insulating coating thereon and adapted to increase in radial dimension causing the cylindrical tube to expand changing the crown of the casting surfaces of the casting rolls and thickness profile of the cast strip during casting. 
 
     
     
         5 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 1  further comprising the step of:
 e. providing water passages in each expansion ring, wherein water can flow through said water passages, and controlling said water flow and regulating the expansion of the expansion rings. 
 
     
     
         6 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 3  further comprising the step of:
 f. providing water passages in each expansion ring, wherein water can flow through said water passages, and controlling said water flow and regulating the expansion of the expansion rings. 
 
     
     
         7 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 1  where the heating elements of the expansion rings are made of stainless steel, nickel or nickel alloy. 
     
     
         8 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 2  further comprising the step of:
 f. controlling casting roll drive to vary the speed of rotation of the casting rolls while varying the radial dimension of the expansion rings with insulating coating thereon responsive to at least one of digital or analogous signals received from the at least one sensor to control roll crown of the casting surfaces of the casting rolls during the casting campaign. 
 
     
     
         9 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 4  further comprising the step of:
 g. controlling casting roll drive to vary the speed of rotation of the casting rolls while varying the radial dimension of the expansion rings with insulating coating thereon and spaced from the edge portions of the cast strip and the radial dimension of each expansion ring with insulating coating thereon corresponding to center portions of the cast strip are responsive to at least one of digital or analogous 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. 
 
     
     
         10 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 1  where each expansion ring with insulating coating thereon and spaced from the edge portions of the cast strip has an annular dimension between 50 and 150 mm. 
     
     
         11 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 3  where each expansion ring with insulating coating thereon and spaced from the edge portions of the cast strip has an annular dimension between 50 and 150 mm and each expansion ring with insulating coating thereon corresponding to center portions of the cast strip has an annular dimension between 50 and 150 mm. 
     
     
         12 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 1  where each expansion ring with insulating coating thereon and spaced from the edge portions of the cast strip has a width of up to 200 mm. 
     
     
         13 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 3  where each expansion ring with insulating coating thereon and spaced from the edge portions of the cast strip has a width of up to 200 mm and each expansion ring with insulating coating thereon corresponding to center portions of the cast strip has a width of up to 200 mm. 
     
     
         14 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 1  where each expansion ring with insulating coating thereon and spaced from the edge portions of the cast strip provides a heating input of up to 30 kW. 
     
     
         15 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 3  where each expansion ring with insulating coating thereon and spaced from the edge portions of the cast strip provides a heating input of up to 30 kW and each expansion ring with insulating coating thereon corresponding to center portions of the cast strip provides a heating input of up to 30 kW. 
     
     
         16 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 1  where the radial dimension of each expansion ring with 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. 
     
     
         17 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 3  where the radial dimension of each expansion ring with insulating coating thereon and spaced from the edge portions of the cast strip and each expansion ring with insulating coating thereon corresponding to center portions of the cast strip can be controlled independently to control the roll crown of the casting surfaces of the casting rolls. 
     
     
         18 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 4  further comprising the step of:
 g. controlling the position of the casting roll to vary the horizontal distance between the casting roll axial centerlines while varying the radial dimension of the expansion rings, each expansion ring with insulating coating thereon corresponding to at least one property in a center portion or edge portion of the cast strip responsive to at least one of digital or analogous signals received from the at least one sensor to control roll crown of the casting surfaces of the casting rolls during the casting campaign. 
 
     
     
         19 . A method of continuously casting thin strip by controlling roll crown comprising the steps of:
 a. assembling a caster having 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;   b. positioning at least one expansion ring within the cylindrical tube corresponding to center portions of the cast strip formed on the casting rolls during a casting campaign, the at least one expansion ring having at least one heating element and an insulating coating thereon and adapted to increase in radial dimension causing the cylindrical tube to expand changing crown of the casting surfaces and thickness profile of the cast strip during casting;   c. assembling a metal delivery system capable of forming a casting pool supported on the casting surfaces of the casting rolls above the nip with side dams adjacent ends of the nip to confine the casting pool;   d. controlling the radial dimension of the at least one expansion ring with insulating coating thereon responsive to at least one of digital or analogous signals received from at least one sensor to control the roll crown of the casting surfaces of the casting rolls during the casting campaign.   
     
     
         20 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 19  further comprising the step of:
 e. positioning at least one sensor capable of sensing at least one of the following properties:
 temperature of the at least one expansion ring; 
 thickness profile of the cast strip downstream; 
 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 generating digital or analogous signal or signals indicative of at least one of the above mentioned properties of the cast strip. 
 
     
     
         21 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 19  further comprising the step of:
 e. providing water passages in the at least one expansion ring, wherein water can flow through said water passages, and controlling said water flow and regulating the expansion of the at least one expansion ring. 
 
     
     
         22 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 19  wherein the at least one heating element is made of stainless steel, nickel or nickel alloy. 
     
     
         23 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 20  further comprising the step of:
 f. controlling casting roll drive to vary the speed of rotation of the casting rolls while varying the radial dimension of the at least one expansion ring with insulating coating thereon responsive to at least one of digital or analogous signals received from the at least one sensor to control roll crown of the casting surfaces of the casting rolls during the casting campaign. 
 
     
     
         24 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 19  wherein the at least one expansion ring with insulating coating thereon has an annular dimension between 50 and 150 mm. 
     
     
         25 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 19  wherein the at least one expansion ring with insulating coating thereon has a width of up to 200 mm. 
     
     
         26 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 19  wherein the at least one expansion ring with insulating coating thereon provides a heating input of up to 30 kW. 
     
     
         27 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 19  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. 
     
     
         28 . The method of continuously casting thin strip by controlling roll crown as claimed in  claim 20  further comprising the step of:
 f. controlling the position of the casting roll to vary the horizontal distance between the casting roll axial centerlines while varying the radial dimension of the at least one expansion ring, each expansion ring with insulating coating thereon corresponding to at least one property in the center portion of the cast strip responsive to at least one of digital or analogous signals received from the at least one sensor to control roll crown of the casting surfaces of the casting rolls during the casting campaign. 
 
     
     
         29 . An apparatus for continuously casting thin strip by controlling roll crown comprising:
 a. 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;   b. at least two expansion rings positioned within and adjacent 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 at least one heating element and an insulating coating thereon and 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;   c. 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.   
     
     
         30 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 29  further comprising:
 d. at least one sensor capable of sensing at least one of the following properties:
 temperature of the expansion rings; 
 thickness profile of the cast strip positioned downstream of the nip; 
 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 analogous signal or signals indicative of at least one of the above properties to 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:
 d. 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 at least one heating element and an insulating coating thereon and adapted to increase in radial dimension causing the cylindrical tube to expand changing roll crown of the casting surfaces and thickness profile of the cast strip during casting. 
 
     
     
         32 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 30  further comprising:
 e. 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 at least one heating element and an insulating coating thereon and adapted to increase in radial dimension causing the cylindrical tube to expand changing roll crown of the casting surfaces and thickness profile of the cast strip during casting. 
 
     
     
         33 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 30  further comprising:
 e. a control system 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 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 32  further comprising:
 f. a control system 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 and the radial dimension of the at least one expansion ring with an insulating coating thereon corresponding to center 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. 
 
     
     
         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 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 31  where each expansion ring with an insulating coating thereon spaced from the edge portions of the cast strip has an annular dimension between 50 and 150 mm and each expansion ring with an insulating coating thereon corresponding to center portions of the cast strip has an annular dimension between 50 and 150 mm. 
     
     
         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 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 31  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 and each expansion ring with an insulating coating thereon corresponding to center portions of the cast strip has a width of up to 200 mm. 
     
     
         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 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 31  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 and each expansion ring with an insulating coating thereon corresponding to center portions of the cast strip provides a heating input of up to 30 kW. 
     
     
         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 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 31  where the radial dimension of each expansion ring with insulating coating thereon and spaced from the edge portions of the cast strip and each expansion ring with insulating coating thereon corresponding to center portions of the cast strip can be controlled independently to control the roll crown of the casting surfaces of the casting rolls. 
     
     
         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 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 31  wherein the heating elements are made of stainless steel, nickel or nickel alloy. 
     
     
         45 . An apparatus for continuously casting thin strip by controlling roll crown comprising:
 a. 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;   b. 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 at least one heating element and an insulating coating thereon, the at least one expansion ring adapted to increase in radial dimension causing the cylindrical tube to expand changing crown of the casting surfaces and thickness profile of the cast strip during casting;   c. 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.   
     
     
         46 . The apparatus for continuously casting thin strip by controlling roll crown as claimed in  claim 45  further comprising:
 d. at least one sensor capable of sensing at least one of the following properties:
 temperature of the at least one expansion ring; 
 thickness profile of the cast strip positioned downstream of the nip; 
 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 analogous signal or signals indicative of at least one of the above properties to 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  further comprising:
 e. a control system 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 and regulating 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.