METHOD FOR PRODUCING HIGH STRENGTH STEEL SHEET HAVING NOT LOWER THAN 760 MPA TENSILE STRENGTH AND EXCELLENT STRAIN-AGING CHARACTERISTIC AND METHOD FOR PRODUCING HIGH STRENGTH STEEL TUBE USING IT

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a high strength steel sheet having ≥760 MPa class tensile strength and excellent strain-aging characteristic and a method for producing a high strength steel tube using the above steel sheet.;SOLUTION: This method for producing the high strength steel sheet having ≥760 MPa class tensile strength and excellent strain-aging characteristic is performed as the followings: the steel composed by mass% of 0.01-0.5% C, 0.01-3.0% Si, 0.1-5.0% Mn, ≤0.03% P, ≤0.01% S and the balance Fe with inevitable impurities, is melt and cast and further; hot-rolling is performed; at the cooling time, this steel is cooled at 0.5-40°C/s average cooling speed at the center part of the steel sheet in the temperature range of 600-450°C; and a cold-working or a warm-working is applied at the room temperature to 300°C working temperature and 1.5-15 working ratio. Further, the method for producing the high strength steel sheet having ≥760 MPa class tensile strength and excellent strain-aging characteristic is produced into the steel tube by using the above steel sheet.;COPYRIGHT: (C)2007,JPO&INPIT