Manufacturing method of flat steel products and flat steel products

摘要

The present invention shows a Wsa (1-5) value of less than 0.35 占 퐉, a planar anisotropy (? R) of -0.5 to +0.5 in at least one of the surfaces of a flat steel product after 5% biaxial deformation, (H) of more than 0.1 GPa to less than 3.0 GPa from the surface of the steel product to a depth of less than 200 mu m. In order to accomplish this, it is preferable to use a material containing 0.0003-0.050% C, 0.0001-0.20% Si, 0.01-1.5% Mn, 0.001-0.10% P, 0.0005-0.030% S, 0.001-0.12% N, and in each case optionally 0.0001-0.15% Ti, 0.0001-0.05% Nb, 0.005% B, 0.15% Cu, 0.15% Cr, 0.15% Ni, 0.10% Mo, ≤ 0.05% Sn and the remainder Fe and unavoidable impurities are heated to a slab withdrawal temperature (Bzt) of 1200-1270 ° C, rough rolled at a thickness reduction rate of 80-90%, and then rolled at 850-950 ° C Rolled to a flat steel product of 3 to 5 mm thickness at a thickness reduction rate of 85 to 95% at a final temperature of 95 to 99.5% with a total strain of 95 to 99.5% and a thickness reduction (? DF) of 1 to 25 %, And the flat steel product is cooled to a winding temperature of 620 - 780 캜 at a cooling rate of 4 - 30 K / s and wound. After pickling, the flat steel product is cold rolled at a total strain of 70 to 90% and recrystallized annealed at 650-900 0 C. The slab withdrawal temperature (Bzt), the total residence time (GLZ), the thickness reduction in the final hot rolling pass (? DF), and the coiling temperature (HT) satisfy the following conditions. -0.529653 * Q + 0.944372 * HT_t + 0.711559 *? DF_t -0.1889459 Here, Bzt is input in ° C, GLZ is in minutes, HT is in ° C, and ΔdF is in%, and Q = ((Bzt / GLZ) - 5.55281 ° C / minute) / (1.777359 ° C / minute); HT_t = (HT - 728.13030C) /42.300114C and? DF_t = (? DF - 12.43384%) / 2.306328%.