| 摘要 |
PURPOSE:To develop a steel sheet for galvanizing having excellent deep drawing property by subjecting a dead soft steel sheet contg. specific amts. of Nb and Ti to a heat treatment under specific conditions. CONSTITUTION:Ti and Nb are added and incorporated as shown by the following equation in a dead soft steel contg. <0.007% C, <0.8% Si, <1.0% Mn, <0.08% P, 0.01-0.1% Al, <0.008% N as a steel sheet for galvanizing. More specifically, Ti is incorporated in the range of [N%-0.02%]X48/14<Ti%<4.0X C% 3.43N%, and Nb is incorporated at 0.003-0.025% with 2XC% or more in such a way that the total amt. of Nb+Ti is <0.04%. The steel slab having such compsn. is subjected to hot rolling and descaling then to cold rolling and further to heating at 730 deg.C-A3 transformation point, wherein the time until the slab is cooled down to 550 deg.C from the attainment at 730 deg.C is maintained at >=60sec and the cooling rate in this stage is 2 deg.C/sec-150 deg.C/sec. |
