| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a superhigh strength hot rolled steel sheet satisfying TS of≥1,180 MPa which has excellent surface properties and sheet flatness, and is further provided with excellent weldability. SOLUTION: A slab having a composition comprising, by mass, 0.10 to 0.17% C,≤0.30% Si, 1.00 to <2.00% Mn,≤0.020% P,≤0.01% S,≤0.005% N and 0.01 to 0.1% SolAl, and the balance Fe with inevitable impurities is directly, or after heating, subjected to hot rolling at a finishing temperature of an Ar3 point temperature or higher. Within 2 s after the finish of the hot rolling, the same is subjected to primary cooling to 450 to 650°C at a cooling rate of≥150°C/s, is next subjected to second cooling to≤300°C at a cooling rate of 20 to 100°C/s, and is then coiled at a coiling temperature of≤300°C, so as to produce the superhigh strength hot rolled steel sheet. COPYRIGHT: (C)2007,JPO&INPIT
|
