Ultrahigh-strength steels at elevated temperatures

The main purpose of this research is to bring deeper understanding about the use of compression loaded ultrahigh-strength steel components at elevated operating temperatures. Another reason for this research is lack of design guidelines concerning ultrahigh-strength steels. This paper provides elevated temperature tensile test data for S700 and S960 ultrahigh-strength steels and discusses the implications of the data from the point of view of structural engineering based on Eurocode 3 design procedures. The experimental part of this paper consists of the tensile testing of two ultrahigh-strength steels grades at temperatures between room temperature and 1000 °C. The models for predicting the temperature reduction factors of Young's modulus, yield strength, ultimate strength and proportional limit are also proposed based on the test results. The obtained proportional limit values together with calculations exhibited that the capacities against buckling of S700 and S960 steels at elevated temperatures are weaker than assumed in Eurocode 3 and Tetmajer's theory for these steel grades. This is mainly due to the lower proportional limit values at room temperature than expected. However, the detected proportional limits do not decrease as fast as Eurocode 3 assumes while the operating temperature increases.