亚温淬火工艺对低碳低合金高强钢组织及性能的影响

Influence of lamellarizing process on microstructure and properties of low carbon low alloy high-strength steel

对低合金高强钢分别进行淬火+回火(QT)热处理和淬火+两相区的亚温淬火+回火(QLT)三段式热处理,采用光学显微镜(OM)、扫描电镜(SEM)、电子背散射衍射(EBSD)方法等观察分析其显微组织形貌、组成相和大角度晶界的密度分布,并测试其力学性能。结果表明:相比于QT工艺,低合金高强钢在QLT工艺后,强度虽稍有下降,但低温冲击韧性显著提高,而且屈强比降低,表现出良好的综合力学性能。在发生奥氏体逆转变以及两相区等温过程中,亚温淬火工艺细化新生成的奥氏体晶粒尺寸、增加大角度晶界密度,使有效晶粒尺寸明显减小,残留奥氏体的含量明显增加。

The microstructure morphology,composition of the phase and large-angle grain boundary density distribution of a low carbon low alloy high strength steel treated by QT（ quenching and tempering） and QLT（ lamellarizing process between quenching and tempering）processes were analyzed by means of optical microscope（ OM）,scanning electron microscopy（ SEM）,electron back-scattered diffraction（ EBSD） technique and mechanical properties test.The results show that compared with QT process,the tensile strength of the steel treated by QLT process decreases slightly,and the low temperature impact toughness increases significantly and the yield ratio decreases.The steel treated by QLT process exhibits better comprehensive mechanical properties than that treated by QT process.QLT process can refine the effective grain size,increase the large-angle grain boundary density,and the content of the residual austenite increases.