A new kind of Mn Mo Nb Cu B bainite steel which satisfied mechanical demands of E690 offshore plate steel was designed. The effect of two processes thermomechanical control process （TMCP）＋ tempering （T） and thermomechanical control process （TMCP） ＋ reheating and quenching （RQ） ＋ tempering （T） on microstructure and mechanical properties were studied by means of scan electron microscope （SEM）, transmission electron micro- scope （TEM） and electron back scatter diffraction （EBSD）. The results showed that optimal mechanical properties were available when tempering at 550 ℃ for both processes. The microstructure of the TMCP＋T treated sample tempering in the range of 450 to 550 ℃ for 1 h did not change dramatically yet the lath in the TMCP＋RQ＋T trea- ted sample merged together and transformed into polygonal ferrite. At the same time, the sub-structure of grain bainite transformed from lath to cell shape to refine grains with tempering temperature mounting. Lots of sub-grain boundaries were located within bainite and adjacent bainite grain boundaries were high angle.
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机译：设计了一种满足E690海上板材的力学要求的新型Mn Mo Nb Cu B贝氏体钢。用扫描电子显微镜（SEM）研究了热力学控制过程（TMCP）＋回火（T）和热力学控制过程（TMCP）＋再热淬火（RQ）＋回火（T）两个过程对组织和力学性能的影响。 ），透射电子显微镜（TEM）和电子背散射衍射（EBSD）。结果表明，两种工艺均在550℃回火时可获得最佳的机械性能。经TMCP ＋ T处理的样品在450至550℃的温度下回火1 h的显微组织没有显着变化，但经TMCP ＋ RQ ＋ T处理的样品中的板条融合在一起并转变为多边形铁素体。同时，随着回火温度的升高，贝氏体晶粒的子结构由板条状转变为孔状，从而细化晶粒。贝氏体内部有许多亚晶界，相邻贝氏体晶界呈高角度。
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