| 摘要 |
Disclosed are a steel pipe for an oil well and a manufacturing method thereof capable of obtaining excellent corrosion resistance while having a tensile strength of 1000 MPa or higher by controlling alloy components and quenching and tempering (QT) thermal-treatment conditions to form a tempered martensite structure. According to the present invention, the manufacturing method of the steel pipe for an oil well comprises: (a) a step of reheating a slab comprising 0.23-0.29% of C, 0.2-0.4 wt% of Si, 0.3-1.0 wt% of Mn, 0.2-0.5 wt% of Ni, 0.4-1.2 wt% of Cr, 0.05-1.05 wt% of Cu, 0.05-0.80 wt% of Mo, 0.005-0.020 wt% of Ti, 0.005-0.060 wt% of Al, 0.05-0.10 wt% of V, 0.02-0.04 wt% of Nb, 0.006 wt% or less of N, and the remainder consisting of Fe and inevitable impurities at a slab reheating temperature (SRT) of 1200-1250°C; (b) a step of finish hot rolling the reheated slab at a finish delivery temperature (FDT) of 800-880°C; (c) a step of cooling the hot rolled slab at a speed of 20-30 °C/sec until 600-650°C to coil up; and (d) a step of uncoiling the coiled slab to quenching and tempering (QT) thermal treat the slab. |
