Effect of Tensile-Strain Rate on Mechanical Properties of High-Strength Q460 Steel at Elevated Temperatures

This paper presents the effect of temperature and tensile-strain rate on the mechanical properties of high-strength low-alloy structural Q460 steel. Standard coupon tensile tests were carried out to obtain the stress-strain curves of Q460 steel subjected to a temperature range of $25\mathrm{°C}–800\mathrm{°C}$. Three tensile-strain rates, namely, $0.001/\min$, $0.02/\min$, and $0.2/\min$, were selected to investigate the effect of strain rate on mechanical properties. Based on the stress-stain curves, the yield strength at different strain levels, tensile strength, and elastic modulus were determined. The reduction factors of mechanical properties of Q460 steel were calculated as the ratio of properties at elevated temperature to those at ambient temperature. The test results show that the strength and elastic modulus of Q460 steel remains 80% at temperatures lower than 500°C, and higher tensile-strain rate yields lower strength and elastic modulus properties. The reduction factors of mechanical properties decline significantly when the temperature exceeds 500°C, and the higher tensile-strain rate yields higher strength and elastic modulus properties. All the specimens experienced obvious necking before fracture and showed good ductility. Different high-strength steels exhibit different reduction factors even though the nominal strength of these steels is similar. The reduction factors suggested by other standards were not suitable to predict the properties deterioration of high-strength Q460 steels at elevated temperatures.