国产Q690高强钢高温下力学性能试验研究

通过国产Q690高强钢的稳态试验研究，得到20~800℃下钢材的试验现象、应力-应变关系曲线、力学性能参数，并将所得试验结果与相关规范和已有研究进行比较。研究发现：随温度升高，试验后钢材表面及断口形貌区别明显，应力-应变关系曲线的初始线弹性段缩短、极限应力对应应变减小、下降段趋于平缓；弹性模量、屈服强度和抗拉强度等力学性能指标随温度升高而降低；而断后伸长率在200~500℃时相较于常温值有小幅度下降，600℃后明显增加；当温度低于500℃时，不同名义屈服强度折减系数之间存在较大差异。目前已有研究建议的钢材高温力学性能模型并不适用于Q690高强钢，通过试验结果拟合得到了高温下Q690钢力学性能模型，以期用于Q690钢材的钢结构抗火安全评估与设计。

Experimental research on mechanical properties of domestichigh strength steel Q690 at elevated temperatures

An experimental study was conducted on domestic high strength steel Q690 by steady-state test. The experimental phenomena, mechanical properties and stress-strain curves at elevated temperatures ranged from 20℃ to 800℃ were obtained. The tests results were compared with current codes and observations of other researchers. Results show that, the surface and fracture of the specimens undergo significant change with the increase of temperature. The linear elasticity of the stress-strain curve shortens, the strain corresponding to tensile strength decreases, and the descending stage tends to be gentle. The elastic modulus, yield strength and tensile strength decrease with the increase of temperature. The elongation slightly decreases for heating temperature between 200℃ to 500℃, and it significantly increases for heating temperature above 600℃. When the temperature is below 500℃, different nominal yield strength reduction factors are different. The models of high temperature mechanical properties presented in existing researches are not applicable for Q690. For fire safety assessment and design of steel structure with Q690, predictive equations were proposed for evaluation of material performance of Q690 at elevated temperatures.