淬火工艺对马氏体高强钢组织和性能的影响

摘要：采用拉伸、冲击、金相、电子背散射衍射、透射电镜、X射线衍射等试验手段，研究了在线直接淬火+回火（DQT）与离线再加热淬火+回火（RQT）工艺对马氏体高强钢组织性能的影响。结果表明，2种试验钢组织均为板条马氏体，RQT试验钢原奥氏体晶粒及板条束呈等轴状，板条块较短，板条较宽，DQT试验钢原奥氏体晶粒呈扁平状，板条束贯穿整个晶粒，板条块呈细长状，板条宽度较小；位错强化是DQT试验钢强度较RQT高的主要原因；板条束为控制DQT和RQT试验钢韧性的最小单元；DQT试验钢大角晶界比例较低，其具有较大的马氏体板条束尺寸以及更高的位错密度，断裂应力较低，低温韧性较差。

Effect of quenching process on microstructure and properties of martensitic high strength steel

Abstract： The effects of online direct quenching + tempering (DQT) and offline reheating quenching + tempering (RQT) on the microstructure and properties of martensitic high strength steel were studied by means of tensile test, impact test, metallographic examination, electron backscatter diffraction, transmission electron microscopy and X ray diffraction. The results show that, the microstructures of the two tested steels are lath martensite, the prior austenite grain and packet of RQT steel are equiaxed, the block is shorter and the lath is wider; but the prior austenite grain of DQT steel is pancaked, the packet runs through the whole grain, the block is elongated and the lath is narrower; dislocation strengthening is the main reason for the higher strength of DQT steel than that of RQT steel; packet is the smallest unit to control the toughness of DQT and RQT steels; DQT steel has a lower proportion of large angle grain boundary, larger packet size and higher dislocation density, which makes its fracture stress lower, so the low temperature toughness is poor.