| 摘要 |
Disclosed is a method for manufacturing a steel plate for an ultrahigh-strength line pipe, whereby: steel comprised of 0.03-0.08% C, 0.01-0.50% Si, 1.5-2.5% Mn, 0.01% or less P, 0.0030% or less S, 0.0001-0.20% Nb, 0.0001-0.03% Al, 0.003-0.030% Ti, 0.0010-0.0050% N, 0.0050% or less O, in terms of mass%, with the remainder being iron and unavoidable impurities, is shaped into ingots; this steel is cast into billets; these billets are hot-rolled to form a steel plate; the surface of the steel plate is cooled until the surface temperature of the aforementioned steel plate is a prescribed temperature that is higher than 540°C, with a water quantity concentration of 0.6 m3/(m2 ° min) or less; and then the surface of the aforementioned steel plate is cooled with a water quantity concentration of 1.3 m3/(m2 ° min) or more. |
