亚稳奥氏体对高强度海洋工程用钢力学性能的影响

采用力学性能测试、组织观察等方法研究临界退火和不同温度回火对海洋工程用钢显微组织和力学性能的影响.结果表明，实验钢经两相区退火和不同温度回火后，获得了回火马氏体及不同体积分数(0~6%)的残余奥氏体.随实验钢中残余奥氏体体积分数的增加，屈服强度从753MPa降低到506MPa，抗拉强度介于794~843MPa，屈强比从0.9降低到0.6，延伸率从31.3%提高到36.2%.实验钢中残余奥氏体能够提高冲击塑性变形能力并阻碍裂纹扩展，在-80℃冲击功达到236J，然而热稳定性差的残余奥氏体在低温下优先转变成马氏体并降低了低温韧性，冲击功下降到136J.

Effect of Metastable Austenite on Mechanical Properties of High-Strength Steel in Oceaneering

The effects of critical annealing and tempering at different temperatures on the microstructure and mechanical properties of marine engineering steels were studied. The results show that the microstructure of the tested steel contains tempered martensite and different volume fraction (0~6%) retained austenite after two-phase zone annealing and tempering at different temperature. When the volume fraction of retained austenite increases from 0 to 6%， the yield strength decreases from 753~506MPa and the tensile strength ranges from 794~843MPa， the yield ratio decreases from 0.9 to 0.6， and the elongation increases from 31.3%~36.2%. The retained austenite in the tested steel can improve the impact work for plastic deformation and hinder the crack propagation. The impact energy at -80℃ reaches 236J. However， due to the poor thermal stability， the retained austenite prefers to transform into martensite at low temperature， leading to a reduction of low-temperature toughness and the impact energy at -80℃ drops to 136J.