High intensity cold rolling steel sheet, production manner of high intensity melting galvanized steel sheet and high intensity alloy melting galvanized steel sheet, and high intensity cold rolling steel sheet and production manner of high intensity melting galvanized steel sheet, production mannered null mass of high intensity alloy

摘要

PROBLEM TO BE SOLVED: To provide a high strength cold rolled steel sheet, high strength hot dip galvanized steel sheet, and high strength alloyed galvannealed steel sheet having maximum tensile strength of 780 MPa, an appropriately high yield ratio and suitable for skeleton sections of automobile bodies, a production method of a high strength cold rolled steel sheet, a production method of a high strength galvanized steel sheet, and a production method of a high strength alloyed galvannealed steel sheet.;SOLUTION: The high strength cold rolled steel sheet contains, by mass%, 0.055 to 0.095% C, 1.2% Si, 1.9 to 2.5% Mn, 0.001 to 0.03% P, 0.0001 to 0.008% S, 0.3% Al, 0.0005 to 0.06% N, 0.014 to 0.028% Ti, 0.34 to 0.046% Nb, 0.005 to 0.27% Mo, 0.0006 to 0.0026% B, and 0.0005 to 0.0045% O, and consists of the balance iron and inevitable impurities.;COPYRIGHT: (C)2007,JPO&INPIT