Q355、Q460和Q690钢材火灾降温阶段力学性能对比

Comparison of Mechanical Properties of Q355， Q460 and Q690 Steel at the Cooling Stage of Fire

摘要:

基于Q355、Q460和Q690钢材在火灾升温和降温全过程中的力学性能试验结果，对3种钢材火灾降温阶段的断口形貌和力学性能进行对比分析.结果表明：当最高受热温度在700 ℃以内时，Q460和Q690钢材的降温阶段弹性模量折减系数相近，3种钢材屈服强度f_0.2折减系数相差较大，屈服强度f_2.0折减系数相近，极限强度折减系数有一定差距；当最高受热温度为800、900 ℃时，3种钢材降温阶段弹性模量和屈服强度折减系数相差较大，而极限强度折减系数相差较小；将现有规范推荐的钢材高温力学性能与3种钢材降温阶段力学性能进行对比得出，现有规范中钢材升温阶段力学性能折减系数无法系统地预测钢材降温阶段力学性能.

Abstract:

Based on the experimental results， the fracture morphology and mechanical properties of Q355， Q460， and Q690 steels during the cooling stage were analyzed and compared. The results show that when the peak heating temperature is below 700 ℃， the reduction factors of Young’s modulus for Q460 and Q690 steel at the cooling stage are similar. The differences in reduction factor of yield strength f_0.2 among the three kinds of steels are large， while they are small in that of yield strength f_2.0 and ultimate strength. At peak heating temperatures of 800 ℃ or 900 ℃， the differences in the reduction factors for Young’s modulus and yield strength among Q355， Q460， and Q690 steels at the cooling stage are more pronounced， while the differences in ultimate strength reduction factors are smaller. The high temperature mechanical properties of steel recommended by the existing specification are compared with the mechanical properties of the three kinds of steel at the cooling stage. The results also show that the reduction factors proposed in the existing specifications cannot predict the mechanical properties of steel at the cooling stage well.