HIGH STRENGTH HOT-ROLLED STEEL SHEET AND METHOD OF MANUFACTURING THE HOT-ROLLED STEEL SHEET

摘要

PURPOSE: A high-strength hot rolled steel sheet and a manufacturing method thereof are provided to obtain a super high strength and superior elongation ratio of 15% or more by implementing a maintenance process in the ferrite temperature range to form enough ferrite. CONSTITUTION: A method for manufacturing a high-strength hot rolled steel sheet comprises the steps of: reheating a slab panel(S110), hot rolling the reheated panel at an FDT(Finishing Delivery Temperature) of 800-950°C(S120), cooling the hot rolled panel to the ferrite temperature range and maintaining the panel in the ferrite temperature range for three seconds or longer(S130), and cooling the panel to a martensite temperature range(S140). [Reference numerals] (AA) Start; (BB) End; (S110) Reheating slab(SRT:1150-1250°C); (S120) Hot rolling(FDT:800-950°C); (S130) First cooling/maintaining(maintaining:650-750°C, 3 seconds or longer); (S140) Second cooling(cooling finish temperature:450°C, 3 seconds or longer)