Mechanical properties of TMCP high strength steels with different strength grades at elevated temperatures

Abstract

High strength steel (HSS) is attracting increasing attention because of its economic and environmental benefits, but special concern should be attached to the fire-resistant design as their mechanical properties may deteriorate faster than normal strength steel (NSS) in a fire. Also, the deterioration may be different when their strength grades are different due to the different heat-treatment processes under which they are produced. Aiming to investigate the different mechanical properties of HSS with different strength grades, a type of S460 steel was tested under axial tension at elevated temperatures using steady-state and transient-state methods, and compared with a type of S690 steel, both are produced in thermo-mechanical controlled process (TMCP) but through different routes. It is discovered that the elastic moduli of S460 steel and S690 steel were similar at elevated temperatures but their strengths deteriorated differently; as their strengths turned to be comparable under fire, the structural members made from them could achieve a similar load-carrying capacity. When compared with NSS structural members with the same conditions in fire, said S460 and S690 steel members reserve no advantages arising from their high strength beyond 400 °C.