Production mannered null mass of the precipitation enhanced hot rolling steel sheet whose mechanical characteristics

摘要

PROBLEM TO BE SOLVED: To provide a method of producing a high strength hot rolled steel sheet having uniform mechanical properties.;SOLUTION: Steel comprising 0.01 to 0.16% C, ≤1.0% Si, 0.1 to 1.9% Mn, ≤0.05% P, ≤0.01% S, 0.01 to 0.1% Al, 0.015 to 0.060% Nb and ≤0.006% N is subjected to hot rolling at a finish rolling temperature of ≥Ar3. Within 2 s after the completion of the hot rolling, the steel is cooled at a cooling rate of ≥200°C/s to 600 to 750°C, is subjected to secondary cooling at a cooling rate of 5 to 50°C/s and is coiled at 550 to 650°C. The steel may contain one or more kinds of metals selected from ≤0.1% Ti, ≤0.05% V, ≤1% Cr, ≤0.3% Mo, ≤0.3% Cu, ≤0.3% Ni and ≤0.003% B. Further, at the time of the coiling at 550 to 650°C, preferably, the temperature difference in the whole length of the coil in the coiling temperature is controlled to ≤30°C, and the temperature difference in the whole width is controlled to ≤20°C.;COPYRIGHT: (C)2005,JPO&NCIPI