Abstract: The continuous cooling transformation (CCT) curves of round casting bloom of pipeline steel L360NB (/%: 0. 14C, 0. 32Si, 0. 14Mn, 0. 020Ti, 0. 010V, 0. 038Nb, 0. 040Al) has been measured by a Gleeble-1500 thermal simulation machine, and the structure of steel with cooling rate 0. 1 〜50 °C/s is observed by optical microscope. Results show that with cooling rate 0.1 °C the main structure of steel is lath bainite + quasi-polygonal ferrite with minor acicular ferrite, with cooling rate ≥l.0°C/s the quasi-polygonal ferrite decreases and the lath bainite and acicular ferrite increase, as cooling rate ≥10°C /s the main structure in specimen is lath bainite + acicular ferrite with minor quasi-polygonal ferrite, as 50 °C/s the block quasi-polygonal ferrite is not observed in specimen, it is indicated the Nb-V-Ti compound alloying promotes the formation of bainite.

摘要： 用Gleeble-1500热模拟试验机测定了L360NB管线钢圆铸坯(/%:0.14C、0.32Si、0.14Mn、0.020Ti、0.010V、0.038Nb、0.040Al)的连续冷却转变(CCT)曲线,并用光学显微镜观察了0.1～50℃/s冷却速度的组织。结果表明,当冷却速度为0.1℃/s时,钢的组织主要为板条贝氏体和准多边形铁素体,有少量针状铁素体,当冷却速度≥1.0℃/s,准多边形铁素体减少,板条状贝氏体和针状铁素体增加;当冷却速度≥10℃/s时试样的组织主要为板条状贝氏体和针状铁素体,准多边形铁素体很少,在50℃/s时未观察到块状准多边形铁素体,说明Nb、V、Ti复合微合金化促进贝氏体形成。

关键词: L360NB管线钢, CCT曲线, 组织