热连轧生产厚规格X80管线钢的静态再结晶行为及工艺优化

Static recrystallization behavior and technological improvement of X80 pipeline steel with heavy thickness produced by hot continuous rolling

  • 摘要: 通过双道次压缩实验对首钢迁安公司2160热连轧生产的厚规格X80管线钢形变奥氏体静态再结晶行为进行了研究,依据实验规律对生产工艺进行了改进与优化.通过力学拉伸、冲击及落锤实验,对改进工艺后生产的X80钢的综合性能进行了检测,利用光学显微镜、扫描电镜和透射电镜对X80钢卷显微组织进行了观察分析.结果表明:变形温度是影响奥氏体静态再结晶行为的主要因素;微合金碳氮化物的析出抑制了再结晶的进行,使软化率曲线出现了平台;利用实验结果回归计算出了X80管线钢的静态再结晶激活能为380kJ·mol-1,并根据文献研究讨论了结果的合理性.通过工艺改进与优化,所生产X80钢卷的显微组织细小均匀,呈现典型的针状铁素体特征;析出相中主要包含复合的(Ti,Nb)(C,N)以及单个的NbC;X80钢卷棒状试样的拉伸性能较相关标准均有较大富余量,尤其在冲击、落锤性能方面表现出了良好的低温韧性.

     

    Abstract: The static recrystallization behavior of deformed austenite in X80 pipeline steel with heavy thickness manufactured by the 2160 Hot Continuous Rolling Production Line in Shougang Qiangang was investigated by double hit compression experiment.According to the results,the production technology was improved and optimized.The mechanical properties of X80 pipeline steel obtained by the optimized production technology were tested using tensile,impacting and drop weight tearing tests(DWTT).The microstructure was observed and analyzed using optical microscope(OM),scanning electron microscope(SEM) and transmission electron microscope(TEM).It is shown that deformation temperature is the main factor that influences the static recrystallization behavior.Carbonitride precipitation inhibits recrystallization and causes a plateau in the softening ratio curve.The static recrystallization activation energy of X80 pipeline steel was regressed and calculated to be 380 kJ·mol-1,and its rationality was also discussed according to previous references and investigations.After the technology optimization,the microstructure of X80 pipeline steel is uniform and refined,and represents typical acicular characteristics.Precipitates in the steel mainly include the complex(Ti,Nb)(C,N) and single NbC particles.The tensile properties of X80 steel(tested with bar specimens) exceed relevant standards a lot;especially the toughness at low temperature such as impacting and DWTT properties is excellent.

     

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