低碳微合金管线钢的连续冷却相变及组织研究

Study on Microstructures and Continuous Cooling Transformation Behavior of Low-Carbon Microalloyed Pipeline Steel

通过Gleeble-3800热模拟试验机测定了该低碳微合金管线钢的静态(无热变形)和动态连续冷却相变曲线,并通过光学显微镜和电子显微镜对连续冷却后的组织进行了详细观察和分析。发现随着冷却速度的提高,在连续冷却转变组织中依次出现多边形铁素体(PF)、珠光体(P)、针状铁素体(AF)、粒状贝氏体(GB)和下贝氏体(LB)。在未再结晶区的热变形使C曲线发生左移,扩大了试样的针状铁素体区,并使得相变后的组织得到细化。

Static （without deformation） and dynamic （after deformation in the non-recrystallized austenitic region） curves of continuous cooling transformation were measured by the high-resolution dilatometer attached to the thermomechanical simulator Gleeble-3800 at the various cooling rates. Microstructures after different cooling rates were characterized by optical microscope and electronic microscope. The microstructures in samples change from polygonal ferrite, pearlite, acicular ferrite, granular bainite to lower bainite with the increasing microhardness when cooling rateincreases. It is found that deformation in the non-recrystallized region can shift C-curve to the left side, expand the range of formation of acicular ferrite and lead to finer microstructures in samples.