ELASTOPLASTIC STRESS-ANALYSIS ON FORMATIO N MECHANISM OF GHOST-LINES IN COLD-ROLLED STEEL SHEET PRODUCED FROM CONTINUOUSLY CAST SLAB

Ghost-lines (GL) observed at polished surfaces of cold relied sheets, stretched perpendicular to rolling direction, produced from continuous ly cast slabs were examined in order to investigate formation mechanis m. Results obtained were as follows. (1)Degree of GL was influenced by conditions of segregations such as size, intensity, and position in t he sheet. (2)Simulations of the GL with elasto-plastic stress analysis were carried out under an assumption that there was a difference in s tress-strain curves between the sheet matrix and the segregation. It w as revealed that a convex part was formed at a stretched sheet surface and the convex height was proportional to the size of the segregation and inversely proportional to the depth of the segregation part from the sheet surface. The actual behaviors of the GL in the sheet produce d from continuous casting slab can be quantitatively explained by the calculated results. (3)From above, it was concluded that the GL was ca used by existence of uneven part of mechanical properties inside the s heet.