一种具有极高屈强比的高强钢的室温蠕变特性

Room temperature creep characteristics of a high strength steel with extremely high yield ratio

利用MTS万能试验机研究了屈强比为99.7%的高强钢在不同加载应力条件下的室温蠕变行为,并对不同蠕变条件下的组织演变特征进行了分析。结果表明:在低于屈服强度的应力作用下,试验钢表现出明显的室温蠕变,且蠕变曲线呈现出以稳态阶段为主的双阶段室温蠕变特征。从蠕变曲线的拟合结果可知,曲线符合对数规律,并且蠕变速率随着蠕变时间的增加逐渐降低,其可相差两个数量级。在不同的室温蠕变条件下,该高强钢在室温蠕变过程中组织变化不明显,晶粒都以细小晶粒为主,多数为5μm以下,且晶界都是以15°以下的小角晶界为主,而大角晶界多集中于50°~60°。

The room temperature creep behavior of a high strength steel with yield ratio of 99.7%under different loading stress conditions was studied by using MTS universal testing machine,and the characteristics of microstructure evolution under different creep conditions were analyzed.The results show that under the loading stress lower than the yielding strength,the tested steel shows obvious creep phenomenon at room temperature,and the creep curve shows typical two-stage room temperature creep characteristics based on steady state stage.From the fitting results of the creep curves,it can be found that the curves follow the log law,and the creep rate decreases gradually with the increase of creep time,which may vary by two orders of magnitude.Under different room temperature creep conditions,the change of microstructure of the high strength steel is not obvious in the process of room temperature creep.The grain sizes are very small and most of them are less than 5μm.Besides,the grain boundary is dominated by the small angular grain boundary below 15°,while the large angle grain boundary is mostly concentrated in the 50°-60°range.