Method for casting metal strip with crown control

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 substantially cylindrical tube having thickness of no more than 80 millimeters of a material selected from the group consisting of copper and copper alloy and having a plurality of longitudinal water flow passages extending through the tube;
• b. positioning at least one expansion ring within and adjacent the cylindrical tube at a position corresponding to a center of the cast strip formed on the casting rolls during a casting campaign, the 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. 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. positioning at least one sensor capable of sensing at least one of the following properties:
• the thickness profile of the cast strip downstream;
• the local thickness of the cast strip at a defined spot closer to the center of the cast strip than cast strip edges;
• the casting roll surface crown during the casting campaign;
• the radial casting roll expansion at a defined spot close to the center of the cast strip;
• and generating digital or analogous signals indicative of the at least one above mentioned properties of the cast strip;
• and
• e. controlling the radial dimension of the expansion ring responsive to at least one of the 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.

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 substantially cylindrical tube having thickness of no more than 80 millimeters of a material selected from the group consisting of copper and copper alloy and having a plurality of longitudinal water flow passages extending through the tube;
• b. two expansion rings within and adjacent the cylindrical tube, each expansion ring spaced within 450 mm of edge portions of the cast strip formed on opposite end portions of the casting rolls during a casting campaign, the expansion rings 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;
• and
• d. at least one sensor capable of sensing at least one of the following properties:
• the thickness profile of the cast strip positioned downstream of the nip;
• the local thickness of the cast strip at a defined spot closer to the cast strip edges than a center of the cast strip;
• the casting roll surface crown during the casting campaign;
• the radial casting roll expansion at a defined spot close to the cast strip edges;
• and generating 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.

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, with a coating thereon, and having a plurality of longitudinal water flow passages extending through the tube;
• b. at least one expansion ring within and adjacent the cylindrical tube at a position corresponding to a center of the cast strip formed on the casting rolls during a casting campaign, the 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;
• and
• d. at least one sensor capable of sensing at least one of the following properties:
• the thickness profile of the cast strip positioned downstream of the nip;
• the local thickness of the cast strip at a defined spot closer to the cast strip center than cast strip edges;
• the casting roll surface crown during the casting campaign;
• the radial casting roll expansion at a defined spot close to the cast strip center;
• and generating 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.