Method and apparatus for casting thin cast strip

Abstract

Twin roll casters for casting thin steel strip comprise cooled casting rolls mounted on carriers. One roll is fixed and the other is moveable laterally and biased toward the other roll by carrier drive units acting on the moveable roll carriers. A casting pool of molten steel is supported on the rolls which are rotated to produce a solidified steel strip delivered downwardly from the nip therebetween. A gap is regulated between the rolls such that unsolidified molten metal passes through the nip between the solidified shells of the forming strip and solidifies below the nip. The carrier drive units are effective to apply to the biased roll substantially intermediate biasing forces such that the roll separation force at the casting rolls is regulated to a value between 2 and 4.5 Newtons per millimeter.

1 . An apparatus for continuously casting metal strip comprising:
 a pair of cooled casting rolls forming a nip therebetween;   a metal supply system to deliver molten metal into the nip between the rolls to form a casting pool of molten metal supported on casting roll surfaces above the nip;   a pair of closure plates to confine the molten metal in the casting pool against outflow adjacent the ends of the nip;   a roll drive mechanism to drive the casting rolls in counter-rotational directions to produce a solidified strip of metal delivered downwardly from the nip;   at least one of the casting rolls mounted on a pair of moveable roll carriers that allow that roll to move toward and away from the other roll;   a pair of carrier drive units acting one on each of the pair of moveable roll carriers to bias said one roll toward the other roll; and   a control system to control operation and capable of positioning of the carrier drive units so as to provide a roll separation force at the casting rolls that is regulated to a value of between 2 and 4.5 Newtons per millimeter during a casting operation.   
   
   
       2 . The apparatus of  claim 1  wherein the carrier drive units comprise servo-mechanisms. 
   
   
       3 . The apparatus of  claim 1  wherein the carrier drive units comprise roll biasing units comprising:
 a thrust transmission structure connected to the respective roll carrier;   a thrust reaction structure;   a thrust generator acting between the thrust reaction structure and the thrust transmission structure to exert a thrust on the thrust transmission structure and the respective roll carrier; and   a positioning unit operable to vary the position of the thrust reaction structure.   
   
   
       4 . The apparatus of  claim 1  wherein said control system is operable to move said one roll.