ULTRA-HIGH STRENGTH STEEL SHEET OF 1000MPa GRADE HAVING EXCELLENT WELDED ZONE TOUGHNESS AND METHOD FOR MANUFACTURING THE SAME

摘要

The present invention relates to a super-high-strength steel sheet and a manufacturing method thereof which enable the manufacture of a tensile strength 1000-MPa class super-high-strength steel sheet of which a base material and a welded portion have excellent toughness by precisely controlling alloy components and manufacturing conditions of structural steel. The super-high-strength steel sheet comprises 0.06-0.10 wt% of C, 2.5-4.0 wt% of Mn, 0.5-1.5 wt% of Al, 0.005-0.10 wt% of Nb, 0.005-0.10 wt% of Ti, 0.0015-0.0150 wt% of N, 0.001-0.004 wt% of B, and the rest of Fe and unavoidable impurities. A modified structure includes 85-90% of martensite and 10-15% of ferrite in respect to the total area of the modified structure.