| 摘要 |
<p>Disclosed are a hot-rolled coil which coils an inner spherical portion not having one surface of a plate exposed outside at a relatively lower temperature when compared with that of coiling an outer spherical portion, having one surface of the plate exposed outside to enable the inner spherical portion to have extracting substance continuously formed by slow cooling speed to ascend the material in order to reduce the difference in material of the inner and outer spherical portions; and a method of manufacturing the same. According to the present invention, a method of manufacturing a hot-rolled coil includes: (a) reheating a slab plate formed of 0.04-0.09 wt% of carbon (C), 0.2-0.5 wt% of silicon (Si), 1.3-1.6 wt% of manganese (Mn), equal to or less than 0.02 wt% of phosphorous (P), equal to or less than 0.003 wt% of sulfur (S), 0.03-0.09 wt% of niobium (Nb), 0.02-0.05 wt% of titanium (Ti), and the remainder consisting of iron (Fe) and inevitable impurities in a slab reheating temperature (SRT) equal to or greater than 1220°C; (b) hot-rolling the reheated slab plate in a finishing delivery temperature (FDT) ranging from 900-980°C; (c) cooling the hot-rolled plate, and rolling the plate in an outer spherical portion coiling temperature (CT) ranging from 630-670°C, and an inner spherical portion coiling temperature (CT) ranging from 580-620°C.</p> |
