HIGH-STRENGTH STEEL SHEET WITH HIGH PROOF/ULTIMATE FACTOR, HIGH-STRENGTH COLD-ROLLED STEEL SHEET WITH HIGH PROOF/ULTIMATE FACTOR, HIGH-STRENGTH GALVANISED STEEL SHEET WITH HIGH PROOF/ULTIMATE FACTOR, HIGH-STRENGTH DIP GALVANISED STEEL SHEET WITH HIGH PROOF/ULTIMATE FACTOR, HIGH-STRENGTH ANNEALED DIP GALVANISED STEEL SHEET WITH HIGH PROOF/ULTIMATE FACTOR, METHOD OF MANUFACTURE OF HIGH-STRENGTH COLD-ROLLED STEEL SHEET WITH HIGH PROOF/ULTIMATE FACTOR, METHOD OF MANUFACTURE OF HIGH-STRENGTH DIP GALVANISED STEEL SHEET WITH HIGH PROOF/ULTIMATE FACTOR, AND METHOD OF MANUFACTURE OF HIGH-STRENGTH ANNEALED DIP GALVANISED STEEL SHEET WITH HIGH PROOF/ULTIMATE FACTOR

摘要

FIELD: metallurgy.;SUBSTANCE: invention relates to metallurgy, namely to high-strength steel sheet with the proof/ultimate factor 0.6 and more. The sheet is made from steel of the following composition, wt %: C - 0.03-0.20, Si - 1.0 or less, Mn - 1.5-3.0, P - 0.10 or less, S - 0.05 or less, Al - 0.10 or less, N - 0.010 or less, one or several elements from Ti, Nb and V, the total content of which amounts 0.010-1.000%, 0.001-0.01 Ta, the rest is Fe and background impurities. The sheet composition includes ferrite and secondary phase including martensite. The share of the ferrite area amounts 50% or more, and average size of the crystalline grain amounts 18 microns or less. The fraction of the martensite area in the secondary phase amounts 1-7%.;EFFECT: required strength and mouldability with decrease of sheet weight are provided.;20 cl, 6 tbl, 1 ex