超500 MPa高强钢高温蠕变性能试验研究

Experimental study on high temperature creep behavior of high strength structural steels over 500 MPa

火灾发生时,钢材的高温蠕变效应可能会引起结构失效。对高强结构钢Q550,Q690和Q890进行了一系列高温蠕变试验,试验的温度点包括400、550、700℃和800℃,每个温度点下设3个应力水平,分别为0.4 f1,T、0.6 f1,T和0.8 f1,T(f1,T为高温屈服强度),得到了钢材在不同温度和应力条件下的蠕变曲线与蠕变速率曲线,并根据蠕变速率曲线的特征对蠕变的特征阶段进行划分。试验中观察到当温度与应力水平较低时,蠕变发展极为缓慢;而当温度与应力水平较高时,蠕变发展迅速,总蠕变应变很大;在高温、高应力条件下,蠕变速率曲线呈现三阶段特征,即先下降,随后基本保持恒定,然后迅速升高的三阶段;而在较低温度下,蠕变速率曲线仅呈现前两个阶段,可见温度及应力水平对钢材蠕变的发展具有显著影响。

Creep behavior may lead to the failure of steel structures in fire condition. A series of creep experiments on high strength structural steel Q550,Q690 and Q890 at elevated temperature were carried out. Creep curves and creep rate curves were obtained under different stress and temperature level conditions. According to the characteristics of creep rate curves,three stages of creep curves were demarcated. It can be observed that when the temperature and stress level are low,the development of creep is extremely slow. Nevertheless,when the temperature and stress level are high,the development of creep is very fast. Under the condition of high temperature and high stress level,the creep rate curve can be divided into three stages,i. e. first decreasing,then keeping constant,and then rising rapidly.While under the condition of relatively lower temperature,the creep rate curve can be divided into only the first two stages. It can be seen that the temperature and stress level have a significant influence on the development of steel creep.