| 摘要 |
PROBLEM TO BE SOLVED: To provide a method capable of stably manufacturing a high strength hot-rolled steel sheet which has high uniformity in the whole longitudinal and transverse directions of a coil, and to provide the high strength hot rolled steel sheet manufactured by the method. SOLUTION: Steel having chemical components containing, as essential components, by mass, 0.07 to 0.15% C, 0.8 to 2.0% Si and 1.2 to 3.0% Mn and the balance substantially Fe is hot-rolled, is coiled at <=600 deg.C, is reheated to be in the temperature range T1 of 750 to 900 deg.C and is held at this temperature for t1=>=60 sec. Thereafter, the steel is cooled to be in the temperature range T2 of 370 to 450 deg.C at a cooling rate CR of <=15 deg.C/s, is held at this temperature for t2=>=90 sec, and is cooled to room temperature.
|
