Patent ID: 8016021

Claim:
A thin cast strip having low surface roughness and low porosity made by the steps comprising: a. assembling a pair of cooled casting rolls having a nip between them and with confining closure adjacent the ends of the nip; b introducing molten steel having a total oxygen content of at least 100 ppm and a free oxygen content between 30 and 50 ppm between the pair of casting rolls to form a casting pool between the casting rolls at a temperature such that a majority of oxide inclusions formed therein are in liquidus state; c. counter-rotating the casting rolls and transferring heat from the molten steel to form metal shells on the surfaces of the casting rolls such that the metal shells grow to include oxide inclusions relating to the total oxygen content of the molten steel and to form steel strip free of crocodile surface roughness; and d. forming through the nip between the casting rolls from said solidified shells solidified thin steel strip of low carbon steel having a carbon content in the range of 0.001% to 0.1% by weight, a manganese content in the range of 0.1% to 10.0% by weight, a silicon content in the range of 0.01% to 10% by weight, and oxide inclusions of MnO, SiO 2 , and Al 2 O 3 with an inclusion density of between 2 and 4 grams per cubic centimeter, where the oxide inclusions have an Al 2 O 3 content of at least 3%.