| 摘要 |
PURPOSE:To obtain the titled slab from which large diameter round bar steel having stable quality is obtd. without using continuously cast bloom of large section, by respectively specifying ratio of diameter of round bar steel to slab thickness and ratio of width to thickness in slab. CONSTITUTION:In the invention, a ratio (D/t) of a diameter D of round bar steel manufactured from slab to a thickness (t) of slab is prescribed to <=0.9. In this way, draft in slab thickness direction can be approached to that in slab width direction. As the result, occurrence of wrinkles flaw on round bar steel surface due to smaller draft in slab thickness direction compared with that in slab width direction can be prevented. By ensuring percentage of reduction in area (r) to <=3.5 at rolling to round bar steel from slab while prescribing a ratio (B/t) of a width B of slab to the thickness (t) to >=2.2, deterioration of inner part quality of round bar product can be prevented. Further, by prescribing the ratio (B/t) to 3.0, deformation, etc., due to buckling of round bar can be prevented. |
