Cr-Nb-Cu系X80HD2大应变管线钢冷却转变规律研究

Research on Continuous Cooling Transformation Rule of Cr- Nb- Cu System X80HD2 High Strain Pipeline Steel

研究26.4 mm厚度X80HD2大应变管线钢在未变形和变形条件下的连续冷却转变行为。通过Gleeble-2000热模拟试验机与光学显微镜(OM)、扫描电镜(SEM)、透射电子显微镜(TEM)等相结合的方法,测定未变形和变形奥氏体的连续冷却转变曲线,并对不同冷速和变形条件下的组织进行观察分析。结果表明:冷速较低时,均得到以粒状贝氏体为主的多相组织,高冷速下得到以板条贝氏体为主的多相组织;Cr、Cu等元素能够增强过冷奥氏体稳定性,抑制先共析铁素体的形成,扩大贝氏体的形成区间;第二相粒子析出强化,晶粒细化、组织类型及比例的变化是显微硬度随冷却速度增大的主要原因。

The paper describes the study on continuous cooling transformation behaviors of 26.4 mm thickness XgOHD2 high strain pipeline steel under undeformed and deformed conditions respectively. In the study, continuous cooling transformation curves are determined for undeformed and deformed conditions, the mierostructure under the conditions of various cooling rates and different deformation are observed and analyzed by means of Gleeble - 2000 thermal simulator, OM, SEM and TEM. The results show that multiphase compound structure including granular bainite as major constituent is obtained at lower cooling rates, multiphase compound structure including lath bainite as major constituent at higher cooling rates. The elements such as Cr and Cu can enhance the stability of super - cooling austenite, inhibit the formation of proeutectoid ferrite, extend the temperature range of bainite formation. The second phase particle precipitation strengthening, grain refinement, types and proportion changes of microstructure are the major causes of micro- hardness increased with cooling rate.