| 摘要 |
<p>A seamless steel pipe for a line pipe having high strength and high toughness which has a chemical composition: c: 0.03 to 0.06 %, Si: 0.05 to 0.15 %, Mn: 1.6 to 2.0 %, Al: 0.010 to 0.10 %, Ni: 0.3 to 0.7 %, Mo: 0.10 to 0.40 %, V: 0.01 to 0.06 %, Nb: 0.003 to 0.03 %, Ti: 0.003 to 0.020 %, N: 0.0010 to 0.0100 %, and balance: Fe and inevitable impurities, with the proviso that Mo + 5V ≥ 0.4 % and 2Nb - V ≤ 0 %. The seamless steel pipe is capable of securing the strength and toughness of the X80 grade with stability, and has heat-treatment characteristics which allows the achievement of desired strength with ease independently of the size of a pipe.</p> |
