High-Temperature Mechanical Properties and Microstructural Evolution of Q370qE Bridge Steel

Abstract This study examines the high-temperature mechanical properties of Q370qE steel, focusing on yield strength, ultimate strength, elastic modulus, and elongation at break. High-temperature tensile tests were conducted from 20°C to 700°C to assess these key properties. Results show that with increasing temperature, yield strength, ultimate strength, and elastic modulus decrease significantly, with reductions of 76%, 79%, and 50%, respectively, at 700°C. Elongation at break increases significantly with an enhancement of over 200%. Microstructural analysis, including optical microscopy and scanning electron microscopy, reveals significant changes in grain structure and fracture mechanisms at elevated temperatures. Comparisons with international design codes reveal significant prediction deviations for the temperature-dependent reduction factors of mechanical properties. Based on these findings, new predictive equations were developed, offering improved accuracy in estimating mechanical behavior across the full temperature range. These equations provide valuable insights into the high-temperature performance of Q370qE steel and support its application in thermally demanding structural environments.