Q690D-QT高强钢材的高温动态拉伸力学性能

Tensile mechanical properties of Q690D-QT at high temperatures and high strain rate

为了研究温度20~700℃下国产Q690D-QT高强钢的拉伸力学性能,开展了系列高温准静态和动态拉伸力学性能试验。试验结果表明:准静态拉伸下随温度上升,弹性模量和名义屈服强度f_(0.2)、f_(0.5)(其中f_(0.2)取为应力-应变曲线和应变0.2%比例偏移线交点的应力,f_(0.5)取应变为0.5%时对应的应力)不断下降,而名义屈服强度f_(1.0)、f_(1.5)、f_(2.0)(其中f_(1.0)、f_(1.5)、f_(2.0)分别取应变为1.0%、1.5%和2.0%时对应的应力)和抗拉强度在200~300℃间先略有上升,后不断下降;动态拉伸下屈服强度在室温下应变率效应不明显,在700℃时应变率效应明显。进一步地,采用多项式拟合给出了准静态弹性模量、屈服强度和抗拉强度的高温折减系数预测公式;并标定了可有效描述温度20~700℃、应变率1 000 s^(-1)下Q690D-QT高强钢拉伸力学性能的Johnson-Cook模型参数(A=760 MPa,B=402 MPa,n=0.534,C=0.004,m=0.966)。

Through the steady-state test and high-temperature SHTB test of domestic high-strength steel Q690D-QT,the quasi-static and dynamic tensile mechanical properties of the steel at 20-700 ℃ were investigated.The steady-state test results show that the elastic modulus and the nominal yield strength f_(0.2) and f_(0.5)(f_(0.2) is the intersection point of the stress-strain curve and the proportional line offset by 0.2% strain,f_(0.5) is determined from the intersection of the stress-strain curve and vertical line at 0.5% strain) decrease continuously with the increase of temperature,while the nominal yield strength f_(1.0),f_(1.5),f_(2.0)(f_(1.0),f_(1.5) and f_(2.0) are determined from the intersection of the stress-strain curve and vertical line at 1.0%,1.5%,and 2.0% strain) and ultimate strength first increased slightly between 200-300 ℃ and then decreased continuously.The dynamic test results show that the strain rate effect of tensile yield strength at 700 ℃ is more significant than that at room temperature.With polynomial fitting,prediction formulae were obtained for the elastic modulus,yield strength,and ultimate strength reduction coefficient.The Johnson-Cook model parameters(A=760 MPa,B=402 MPa,n=0.534,C=0.004,m=0.966) were determined to describe the high-temperature dynamic tensile mechanical properties of Q690D-QT high-strength steel at temperature ranging from 20 ℃ to 700 ℃ and at a strain rate of 1 000 s^(-1).