| 摘要 |
<p>PURPOSE: A high strength steel plate and a manufacturing method thereof are provided not only to have an excellent burring character, but also to have a high strength which is more than 980 MPa of a tensile strength. CONSTITUTION: A method of manufacturing a high strength steel plate comprises the following steps: a slab board comprises 0.04-0.1% of carbon (C), 0.2-1.0% of silicone (Si), 0.7-1.7% of manganese (Mn), 0.01-0.1% of phosphorus (P), 0.001-0.01% of sulfur (S), 0.7-1.2% of chrome (Cr), 0.01-0.09% of niobium (Nb), 0.01-0.09% of titanium (Ti), 0.001-0.005% of boron (B), and a rest iron (Fe) and an unavoidable impurity as a weight%; the slab board is hot-rolled at 850-950°C of a finish rolling temperature condition; the hot-rolled board is primary-cooled until 750-600°C; the primary-cooled board is secondary-cooled for 5-10 seconds at a cooling speed which is less than 10°C/sec; and the secondary-cooled board is third-cooled until 400-550°C at a cooling speed which is faster than a cooling speed of a secondary cooling. [Reference numerals] (AA) Start; (BB) Hot rolling (FDT: 850-950°C); (CC) First cooling (50-100°C/sec, 600-750°C); (DD) Second cooling (below 10°C/sec, 5-10 seconds); (EE) Third cooling/wrapping (50-100°C/sec, 400-550°C); (FF) End</p> |
