| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a high strength steel sheet having≥750 MPa tensile strength and having excellent low-temperature toughness and also excellent low-temperature toughness of weld zone even in a very low temperature environment of -46°C and also to provide its manufacturing method. <P>SOLUTION: The high strength steel sheet is composed of steel having a composition which consists of 0.01 to 0.10% C,≤0.30% Si, 1.20 to 2.50% Mn,≤0.010% P,≤0.002% S, 0.2 to 1.5% Ni, 0.1 to 0.8% Mo, 0.005 to 0.06% Nb, 0.004 to 0.025% Ti,≤0.05% sol.Al,≤0.0050% N,≤0.003% O(oxygen) and the balance Fe with impurities or further contains prescribed amounts of one or more elements among Cr, Cu, V, B, Ca, Mg, Zr and REM and in which the value of A represented by equation A=12P+45S+67(N+O) (where the symbol of an element means the content of the element contained in the steel) is made to≤0.5%. The steel sheet has≥0.18°half-width of X-ray diffraction intensity from the (110) plane and≥750 MPa tensile strength or further has a prescribed metallic structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
