| 摘要 |
PURPOSE: An ultra-high strength steel sheet with 980 MPa grade of a tensile strength and an excellent plating ability and a method of manufacturing thereof are provided to secure an excellent plating ability through a process control including an alloy component modulation such as carbon, chrome, etc., an annealing treatment, and a primary cooling etc. CONSTITUTION: A method of manufacturing an ultra-high strength steel sheet with 980 MPa grade of a tensile strength and an excellent plating ability comprises the following steps: a steel sheet consisting of 0.11-0.15% of C, 0.2-0.4% of Si, 2.0-2.5% of Mn, less than 0.02% of P, less than 0.003% of S, 0.02-0.04% of availability Al, 0.3-0.7% of Cr, 0.02-0.08% of Mo, less than 40ppm of N, a rest Fe, and an unavoidable impurity is heated at 770-830°C; after the steel plate is performed an annealing process at 770-830°C, the steel plate is primary cooled at 480-580°C; and after the primary cooled steel plate is processed with over-aging, the steel plate is secondary cooled at a martensite temperature field. [Reference numerals] (AA) Start; (BB) End; (S110) Heat a steel sheet; (S120) Annealing process; (S130) First cooling; (S140) Over aging process; (S150) Second cooling |
