Distribution and Detriment of Bubbles in Continuous Casting Interstitial Free Steel Slab

The distribution and detriment of bubbles in ultra low carbon interstitial free steel were studied by X-ray radiographic and cold-rolled experiment; a total of 24 pieces samples with size 230 mm x 65 mm x 2 mm were detection and 150 bubbles were counted; the results showed that: (1) Two bubbles bands formed in continuous casing slab; bubbles distributed asymmetrically in thickness direction of the slab; small bubbles mainly concentrated in inner art side 1/8 to 1/4 in thickness direction; large bubbles were main in center of the slab in thickness direction; (2) Hundreds of inclusions with sizes 2 mu m to 10 mu m accumulated in cone-shape region after bubbles. Inclusions or Fe and FeO particles often attached or mixed with the bubbles. (3) Small bubbles entered into down-flow easily and rushed out the mould, bubbles and inclusions accumulative band formed in inner art side of the slab. (4) The bubbles, inclusions around the bubbles or large Fe and FeO particles mixing with bubbles became source of the sliver defect.