| 摘要 |
<p>A hot-rolled steel plate for spiral pipes which has excellent low-tempera ture toughness and has a thickness as large as, e.g., 14 mm or more and a hi gh strength satisfying at least the API-X65 standards. Also provided is a pr ocess for producing the steel plate. The steel plate contains, in terms of m ass%, 0.01-0.1% C, 0.05-0.5% Si, 1-2% Mn, up to 0.03% P, up to 0.005% S, up to 0.003% O, 0.005-0.05% Al, 0.0015-0.006% N, 0.005-0.08% Nb, and 0.005-0.02 % Ti, provided that N-14/48 x Ti>0% and Nb-93/14 x (N-14/48 x Ti)>0.00 5%, and further contains 0.01-0.1%, excluding 0.1%, Mo, 0.01-0.3% Cr, and 0. 01-0.3% Cu, with the remainder being Fe and incidental impurities. The steel plate is characterized in that a pipe formed therefrom has a circumferentia l-direction section in which microstructure units have an elongation rate of 2 or lower.</p> |
