Abstract: The continuous cooling transformation (CCT) curves of Φ406.4 mm x 16.5 mm X70 seamless steel tube for deep-sea pipe-line (/% : 0. 07C, 0. 70Si, 0. 80Mn, 0.008P, 0. 002S, 0. 25Ni, 0. 25Cr, 0. 20Mo, 0. 10Cu, 0. 06V, 0. 03Nb, 0. 04Alt,0.006 ON) have been measured by using Gleeble-3500 thermo-mechanical simulator, and the structure feature of the steel tube with cooling rate 0. 1 ~ 100 ℃/s is analyzed by optical microscope, scanning electron microscope and HV hardness meter. Results show that with cooling rate 0.15℃ /s the main structure in steel is ferrite + pearlite, as cooling rate more than 5 ℃/s the structure in steel is bainite + ferrite ； with increasing cooling rate the structure of steel is fined and the hardness of steel increases ； with cooling rate 30 〜50 °C /s the suitable amount of lath bainite structure is obtained therefore to insure getting excellent mechanical properties of pipe-line steel.

摘要： 利用Gleeble-3500热模拟试验机,测定了Φ406.4 mm×16.5 mm X70深海无缝管线钢管（/%:0.07C,0.70Si,0.80Mn,0.008P,0.002S,0.25Ni,0.25Cr,0.20Mo,0.10Cu,0.06V,0.03Nb,0.04Alt,0.0060N）的CCT曲线,并通过光学显微镜,扫描电子显微镜,HV硬度计分析了0.1~100℃/s的冷却速度下钢管的组织特征。结果表明,冷却速度为0.15℃/s时钢中组织主要为铁素体+珠光体,当冷却速度大于5℃/s时,钢中组织为贝氏体+铁素体;随冷却速度的提高,钢组织细化,硬度增加;当冷却速度为3050℃/s时,可以获得适量的板条贝氏体组织,从而可保证管线钢有良好的力学性能。