Method and apparatus for controlling temperature of thin cast strip

Abstract

An apparatus and method for continuously casting thin steel strip includes a pair of counter-rotatable casting rolls having a nip there between capable of delivering cast strip downwardly from the nip, a metal delivery system capable of forming a casting pool supported on casting surfaces of the casting rolls above the nip with side dams adjacent the ends of the nip to confine the casting pool, and a hot rolling mill having work rolls with work surfaces forming a gap between them through which hot strip delivered from the casting rolls is rolled, the work rolls having work surfaces relating to the desired strip profile across the work rolls. Misting jets may be in intervals along the path of the cast strip exiting from the hot rolling mill to form a cooling zone, the misting jets capable of directing toward surfaces of the cast strip a mixture of gas and water having a ratio of gas over water between 9 and 90 to cool the cast strip at more than 1.6° C. per liter of water used.

1 . A method of producing thin cast strip with controlled cooling comprising the steps of:
 a. assembling a thin strip caster having a pair of casting rolls having a nip there between capable of delivering cast strip downwardly from the nip;   b. assembling a metal delivery system capable of forming a casting pool supported on casting surfaces of the casting rolls above the nip with side dams adjacent the ends of the nip to confine the casting pool;   c. assembling adjacent the thin strip caster a hot rolling mill having work rolls with work surfaces forming a gap between them through which hot strip delivered from the casting rolls is rolled, the work rolls having work surfaces relating to the desired strip profile across the work rolls; and   d. positioning misting jets in intervals along the path of the cast strip exiting from the hot rolling mill to form a cooling zone, the misting jets capable of directing toward surfaces of the cast strip a mixture of gas and water having a ratio of gas over water between 9 and 90 (both measured in liters) to cool the cast strip at more than 1.6° C. per liter of water used.   
   
   
       2 . The method as claimed in  claim 1  where the mixture of gas and water has a ratio of gas over water between 20 and 70 (both measured in liters). 
   
   
       3 . The method as claimed in  claim 1  where the gas used to form the mixture of gas and water is selected from the group consisting of nitrogen, inert gas, and air. 
   
   
       4 . The method as claimed in  claim 1  where the water has a turn down ratio of at least 10 to 1 by volume. 
   
   
       5 . The method as claimed in  claim 1  where the cast strip is between 0.3 and 2.0 millimeters in thickness. 
   
   
       6 . A method of producing thin cast strip with controlled cooling comprising the steps of:
 a. assembling a thin strip caster having a pair of casting rolls having a nip there between capable of delivering cast strip downwardly from the nip;   b. assembling a metal delivery system capable of forming a casting pool supported on casting surfaces of the casting rolls above the nip with side dams adjacent the ends of the nip to confine the casting pool;   c. assembling adjacent the thin strip caster a hot rolling mill having work rolls with work surfaces forming a gap between them through which hot strip delivered from the casting rolls is rolled, the work rolls having work surfaces relating to the desired strip profile across the work rolls;   d. positioning misting jets in intervals along the path of the cast strip exiting from the hot rolling mill to form a cooling zone, the misting jets capable of directing toward surfaces of the cast strip a mixture of gas and water having a ratio of gas over water between 9 and 90 (both measured in liters) to cool the cast strip at more than 1.6° C. per liter of water used;   e. forming a shroud extending from adjacent the hot rolling mill to at least end of the cooling zone through which the cast strip moves during cooling; and   f. generating steam from heating the mixture of gas and water by the strip to form a protective atmosphere of less than 5% oxygen in the shrouded cooling zone such that the strip exiting the cooling zone has less than about 2 micron scale.   
   
   
       7 . The method as claimed in  claim 6  further where the cooling zone extends to pinch rolls positioned in the path of the cast strip. 
   
   
       8 . The method as claimed in  claim 6  where nitrogen is introduced into the shroud adjacent instrumentation to inhibit the steam from affecting measurements in the protective atmosphere. 
   
   
       9 . The method as claimed in  claim 6  further where the temperature of the strip at entry to the cooling zone is greater than 750° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       10 . The method as claimed in  claim 6  further where the temperature of the strip at entry to the cooling zone is greater than 850° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       11 . The method as claimed in  claim 6  further where the temperature of the strip at entry to the cooling zone is between 750 and 850° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       12 . The method as claimed in  claim 6  further where the cast strip exiting the cooling zone has less than 20° C. in temperature variation across the width thereof. 
   
   
       13 . A method of producing thin cast strip with controlled cooling comprising the steps of:
 a. assembling a thin strip caster having a pair of casting rolls having a nip there between capable of delivering cast strip downwardly from the nip;   b. assembling a metal delivery system capable of forming a casting pool supported on casting surfaces of the casting rolls above the nip with side dams adjacent the ends of the nip to confine the casting pool; and   c. positioning misting jets in intervals along the path of the cast strip downstream of the casting rolls to form a cooling zone, the misting jets capable of directing toward surfaces of the cast strip a mixture of gas and water having a ratio of gas over water between 9 and 90 (both measured in liters) to cool the cast strip at more than 1.6° C. per liter of water used.   
   
   
       14 . The method as claimed in  claim 12  where the mixture of gas and water has a ratio of gas over water between 20 and 70 (both measured in liters). 
   
   
       15 . The method as claimed in  claim 13  where the gas used to form the mixture of gas and water is selected from the group consisting of nitrogen, inert gas, and air. 
   
   
       16 . The method as claimed in  claim 13  where the water has a turn down ratio of at least 10 to 1 by volume. 
   
   
       17 . The method as claimed in  claim 13  where the cast strip is between 0.3 and 2.0 millimeters in thickness. 
   
   
       18 . A method of producing thin cast strip with controlled cooling comprising the steps of:
 a. assembling a thin strip caster having a pair of casting rolls having a nip there between capable of delivering cast strip downwardly from the nip;   b. assembling a metal delivery system capable of forming a casting pool supported on casting surfaces of the casting rolls above the nip with side dams adjacent the ends of the nip to confine the casting pool;   c. positioning misting jets in intervals along the path of the cast strip downstream of the casting rolls to form a cooling zone, the misting jets capable of directing toward surfaces of the cast strip a mixture of gas and water having a ratio of gas over water between 9 and 90 (both measured in liters) to cool the cast strip at more than 1.6° C. per liter of water used;   d. forming a shroud extending from adjacent the pair of casting rolls to at least the end of the cooling zone through which the cast strip moves during cooling; and   e. generating steam from heating the mixture of gas and water by the strip to form a protective atmosphere of less than 5% oxygen in the shrouded cooling zone such that the strip exiting the cooling zone has less than 2 micron scale.   
   
   
       19 . The method as claimed in  claim 18  where nitrogen is introduced into the shroud adjacent instrumentation to inhibit the steam from affecting measurements in the protective atmosphere. 
   
   
       20 . The method as claimed in  claim 18  further where the cooling zone extends to pinch rolls positioned in the path of the cast strip. 
   
   
       21 . The method as claimed in  claim 18  further where the temperature of the strip at entry to the cooling zone is greater than 750° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       22 . The method as claimed in  claim 18  further where the temperature of the strip at entry to the cooling zone is greater than 850° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       23 . The method as claimed in  claim 18  further where the temperature of the strip at entry to the cooling zone is between 750 and 850° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       24 . The method as claimed in  claim 18  further where the cast strip exiting the cooling zone has less than 20° C. in temperature variation across the width thereof. 
   
   
       25 . An apparatus for casting thin cast strip comprising:
 a. a thin strip caster having a pair of casting rolls having a nip there between capable of delivering cast strip downwardly from the nip;   b. a metal delivery system capable of forming a casting pool supported on casting surfaces of the casting rolls above the nip with side dams adjacent the ends of the nip to confine the casting pool;   c. a hot rolling mill positioned adjacent the thin strip caster having work rolls with work surfaces forming a gap capable of rolling hot strip delivered from the casting rolls, with work surfaces of the work rolls relating to the desired strip profile across the work rolls; and   d. misting jets positioned in intervals along the path of the cast strip exiting from the hot rolling mill to form a cooling zone, the misting jets capable of directing toward surfaces of the cast strip a mixture of gas and water having a ratio of gas over water between 9 and 90 (both measured in liters) to cool the cast strip at more than 1.6° C. per liter of water used.   
   
   
       26 . The apparatus for casting thin cast strip as claimed in  claim 25  where the mixture of gas and water has a ratio of gas over water between 20 and 70 (both measured in liters). 
   
   
       27 . The apparatus for casting thin cast strip as claimed in  claim 25  where the gas used to form the mixture of gas and water is selected from the group consisting of nitrogen, inert gas, and air. 
   
   
       28 . The apparatus for casting thin cast strip as claimed in  claim 25  where the water has a turn down ratio of at least 10 to 1 by volume. 
   
   
       29 . The apparatus for casting thin cast strip as claimed in  claim 25  where the cast strip is between 0.3 and 2.0 millimeters in thickness. 
   
   
       30 . An apparatus for casting thin cast strip comprising:
 a. a thin strip caster having a pair of casting rolls having a nip there between capable of delivering cast strip downwardly from the nip;   b. a metal delivery system capable of forming a casting pool supported on casting surfaces of the casting rolls above the nip with side dams adjacent the ends of the nip to confine the casting pool;   c. a hot rolling mill positioned adjacent the thin strip caster having work rolls with work surfaces forming a gap capable of rolling hot strip delivered from the casting rolls, with work surfaces of the work rolls relating to the desired strip profile across the work rolls;   d. misting jets positioned in intervals along the path of the cast strip exiting from the hot rolling mill to form a cooling zone, the misting jets capable of directing toward surfaces of the cast strip a mixture of gas and water having a ratio of gas over water between 9 and 90 (both measured in liters) to cool the cast strip at more than 1.6° C. per liter of water used;   e. a shroud extending from adjacent the hot rolling mill to at least the end of the cooling zone through which the cast strip moves during cooling; and   f. a protective atmosphere of less than 5% oxygen in the shrouded cooling zone comprising steam generated from heating the mixture of gas and water such that the strip exiting the cooling zone has less than 2 micron scale.   
   
   
       31 . The apparatus for casting thin cast strip as claimed in  claim 30  where nitrogen is introduced into the shroud adjacent instrumentation to inhibit the steam from affecting measurements in the protective atmosphere. 
   
   
       32 . The apparatus for casting thin cast strip as claimed in  claim 30  where the cooling zone extends to pinch rolls positioned in the path of the cast strip. 
   
   
       33 . The apparatus for casting thin cast strip as claimed in  claim 30  where the temperature of the strip at entry to the cooling zone is greater than 750° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       34 . The apparatus for casting thin cast strip as claimed in  claim 30  where the temperature of the strip at entry to the cooling zone is greater than 850° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       35 . The apparatus for casting thin cast strip as claimed in  claim 30  where the temperature of the strip at entry to the cooling zone is between 750 and 850° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       36 . The apparatus for casting thin cast strip as claimed in  claim 30  where the cast strip exiting the cooling zone has less than 20° C. in temperature variation across the width thereof. 
   
   
       37 . An apparatus for producing thin cast strip comprising:
 a. a thin strip caster having a pair of casting rolls having a nip there between capable of delivering cast strip downwardly from the nip;   b. a metal delivery system capable of forming a casting pool supported on casting surfaces of the casting rolls above the nip with side dams adjacent the ends of the nip to confine the casting pool; and   c. misting jets positioned in intervals along the path of the cast strip downstream of the casting rolls to form a cooling zone, the misting jets capable of directing toward surfaces of the cast strip a mixture of gas and water having a ratio of gas over water between 9 and 90 (both measured in liters) to cool the cast strip at more than 1.6° C. per liter of water used.   
   
   
       38 . The apparatus for casting thin cast strip as claimed in  claim 37  where the mixture of gas and water has a ratio of gas over water between 20 and 70 (both measured in liters). 
   
   
       39 . The apparatus for casting thin cast strip as claimed in  claim 37  where the gas used to form the mixture of gas and water is selected from the group consisting of nitrogen, inert gas, and air. 
   
   
       40 . The apparatus for casting thin cast strip as claimed in  claim 37  where the water the water has a turn down ratio of at least 10 to 1 by volume. 
   
   
       41 . The apparatus for casting thin cast strip as claimed in  claim 37  where the cast strip is between 0.3 and 2.0 millimeters in thickness. 
   
   
       42 . An apparatus for casting thin cast strip comprising:
 a. a thin strip caster having a pair of casting rolls having a nip there between capable of delivering cast strip downwardly from the nip:   b. a metal delivery system capable of forming a casting pool supported on casting surfaces of the casting rolls above the nip with side dams adjacent the ends of the nip to confine the casting pool;   c. misting jets positioned in intervals along the path of the cast strip downstream of the casting rolls to form a cooling zone, the misting jets capable of directing toward surfaces of the cast strip a mixture of gas and water having a ratio of gas over water between 9 and 90 (both measured in liters) to cool the cast strip at more than 1.6° C. per liter of water used; and   d. a shroud extending from adjacent the pair of casting rolls to at least the end of the cooling zone through which the cast strip moves during cooling and capable of forming a protective atmosphere of steam of less than 5% oxygen in the shrouded such that the strip exiting the cooling zone has less than 2 micron scale.   
   
   
       43 . The apparatus for casting thin cast strip as claimed in  claim 42  where the cooling zone extends to pinch rolls positioned in the path of the cast strip. 
   
   
       44 . The apparatus for casting thin cast strip as claimed in  claim 42  where the temperature of the strip at entry to the cooling zone is greater than 850° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       45 . The apparatus for casting thin cast strip as claimed in  claim 42  where the temperature of the strip at entry to the cooling zone is greater than 750° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       46 . The apparatus for casting thin cast strip as claimed in  claim 42  where the temperature of the strip at entry to the cooling zone is between 750 and 850° C. and the temperature of the strip at the exiting from the cooling zone is greater than 300° C. as desired. 
   
   
       47 . The apparatus for casting thin cast strip as claimed in  claim 42  where the cast strip exiting the cooling zone has less than 20° C. in temperature variation across the width thereof. 
   
   
       48 . The apparatus for casting thin cast strip as claimed in  claim 42  where the mixture of gas and water has a ratio of gas over water between 20 and 70 (both measured in liters). 
   
   
       49 . The apparatus for casting thin cast strip as claimed in  claim 42  where the gas used to form the mixture of gas and water is selected from the group consisting of nitrogen, inert gas, and air. 
   
   
       50 . The apparatus for casting thin cast strip as claimed in  claim 42  where nitrogen is introduced into the shroud adjacent instrumentation to inhibit the steam from affecting measurements in the protective atmosphere.