Formation Mechanism of Sliver-type Surface Defect with Oxide Scale on Sheet and Coil

Laboratory rolling test of continuously cast steel slab with artificial defects was conducted to determine the origin of sliver-type surface defects with oxide scale on sheet and coil. The results obtained are summarized as follows: (1) The surface crack and pinhole could be the origins of sliver-type surface defects with oxide scale. (2) The deformation behavior of crack-type artificial defects during rolling varied depending on the depth and width of artificial defects, and on the kinds of steel. (3) The crack-type artificial defects of Ti-SULC steel tended to remain after rolling than those of LC-Al-K steel and SUS430 steel, because of the difference in the oxidation behavior at the subsurface during heating. (4) The critical depth for the pinhole-type artificial defects to be exposed by rolling was estimated to be about 4 to 5 mm.