Method of operation of twin roll strip caster to reduce chatter

A method of casting thin strip comprising the steps of:

• assembling a pair of counter-rotating casting rolls laterally forming a gap between circumferential casting surfaces of the casting rolls at a nip between the casting rolls through which metal strip is cast;
• assembling side dams adjacent end portions of the casting rolls to permit a casting pool of molten metal to be formed and supported by the casting surfaces of the casting rolls;
• assembling a metal delivery system above the casting rolls adapted to deliver molten metal to form the casting pool supported on the casting surfaces of the casting rolls above the gap and confined by the side dams;
• counter-rotating the casting rolls such that the casting surfaces of the casting rolls each travel inwardly toward the nip to form metal shells on the surfaces of the casting rolls and deliver a cast strip downwardly from the gap between the casting rolls with a mushy internal portion;
• and
• providing a drive mechanism to directly move one or more casting rolls of the pair of casting rolls to oscillate the gap between the casting rolls at an amplitude between ±5 and ±50 μm at a frequency between 1 and 7 hertz to vary thickness of the mushy internal portion in the cast strip and reduce chatter during casting.