Strip casting

A cast steel strip made by the following steps:

• assembling a pair of cooled casting rolls having a nip between them and closures adjacent the ends of the nip,
• introducing molten metal between said pair of casting rolls to form a casting pool between the rolls with closures confining the pool adjacent the ends of the nip,
• rotating the rolls such that shells of metal solidify from the casting pool onto the casting rolls and are brought close together at the nip to produce a solidified strip delivered downwardly from the nip,
• biasing at least one of the pair of casting rolls toward the other roll of the pair under a substantially constant biasing force such that a substantially constant gap is maintained between the rolls at the nip sufficient to provide separation between the solidified shells at the nip, wherein the biasing force is a force creating a roll separation force less than 0.45 kN, and
• passing molten metal between the solidified shells through the nip where at least a portion of said molten metal is solidified in the strip below the nip.

An apparatus for continuously casting metal strip comprising:

• a pair of parallel casting rolls forming a nip between them,
• 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 immediately 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,
• a control system to control operation and positioning of the carrier drive units so as to maintain a substantially constant gap between the rolls.

An apparatus for continuously casting metal strip comprising:

• a pair of parallel casting rolls forming a nip between them,
• means for delivering molten metal into the nip between the rolls to form a casting pool of molten metal supported on casting roll surfaces immediately above the nip,
• means for confining the molten metal in the casting pool against outflow adjacent the ends of the nip,
• a roll drive 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 roll biasing units acting one on each of the pair of moveable roll carriers to bias said one roll toward the other roll, each roll biasing unit 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,
• means for varying the position of the thrust reaction structure, and
• means for controlling the means for varying the position of the thrust reaction structure so as to replicate a pattern of movement of the roll carriers due to roll eccentricities as an applied pattern of movements of the thrust reaction structure to maintain a constant roll biasing force, and
• means for controlling the roll gap to increase the gap between the rolls after said applied pattern of movements has been established.