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采用扫描电镜、透射电镜及性能测试等方法研究了回火工艺对海洋工程用钢E690组织和性能的影响。结果表明:在同一回火时间下,随着回火温度的增加,试验钢强度呈下降趋势,伸长率呈上升趋势,低温冲击吸收能量先上升然后下降。在同一回火温度下,随着回火时间的延长,试验钢强度呈下降趋势,伸长率先上升后下降,630℃和650℃回火温度下的低温冲击吸收能量受影响较小。试验钢回火后的组织以板条贝氏体为主;其组织随回火温度的增加,由板条贝氏体向粒状贝氏体转变,钢中析出物也相应粗化。
The effects of tempering process on the microstructure and properties of marine engineering steel E690 were studied by scanning electron microscopy, transmission electron microscopy and performance testing. The results show that under the same tempering time, with the increase of tempering temperature, the strength of the test steel decreases, the elongation increases and the energy of low temperature shock absorption first increases and then decreases. Under the same tempering temperature, with the extension of tempering time, the strength of the test steel decreased, the elongation increased first and then decreased, and the impact energy absorbed by low temperature at 630 ℃ and tempering temperature of 650 ℃ was less affected. The microstructure of the test steel after tempering was dominated by lath bainite. The microstructure of the test steels changed from bainite to granular bainite with the increase of tempering temperature, and the precipitates in the steel also roughened accordingly.