A method of continuously casting steel including steps of forming a casting pool of molten steel comprising a carbon content of less than 0.5% by weight on casting surfaces of a pair of internally cooled casting rolls having a nip formed between them, counter rotating the casting surfaces of the casting rolls toward each other to produce a cast steel strip moving downwardly away from the nip between the casting rolls, guiding the cast strip through a first enclosure adjacent the casting rolls as the strip moves away from the casting rolls, the first enclosure having a reducing atmosphere containing carbon monoxide and optionally hydrogen of at least 0.1%, establishing the reducing atmosphere in the first enclosure to control ingress of atmospheric air so as to maintain said atmosphere with a CO to CO2 ratio of at least 1.5 during steady state operation.