Synergistic Effects of Ti and Mo on the Microstructure and Properties of Low-Cost Fire-Resistant and Weather-Resistant Construction Steel

In order to meet the increasing demands of superior structural strength, reliability, and safety, low-cost advanced construction steels with excellent high-temperature strength and weather resistance need to be developed. In the present work, the effects of different Ti contents on the high-temperature resistance of low Mo-containing fire-resistant steel were investigated, and a fire-resistant weathering construction steel with the synergistic effect of low Mo and Ti microalloying was developed. The yield strength of the steel at 600 degrees C was 383 MPa, which was more than two-thirds (67.79%) of its yield strength at room temperature. Moreover, the corrosion resistance of the test steel was better than that of Q345 steel. The microstructure, nanoscale precipitation behavior, and corrosion resistance of the steel were discussed. It was found that the bainitic microstructure exhibited excellent stability at high temperatures. The amount of nanoscale precipitates increased after reheating and tempering at 600 degrees C for three hours. TiC and (Ti, Mo)C particles of similar to 10-nm size could pin dislocations effectively to guarantee high strength. The synergistic effect of Ti and Mo suppressed the growth of nanoscale precipitates, and the strength loss at 600 degrees C was compensated by nanoscale precipitation strengthening. Moreover, the thickness of the corrosion product layer formed on the steel matrix surface and the relative content of alpha-FeOOH increased with time; thus, the steel exhibited superb corrosion resistance.

Automated summary

A low Mo-containing fire-resistant weathering construction steel with the synergistic effect of low Mo and Ti microalloying was developed, which exhibited excellent high-temperature strength, weather resistance, and corrosion resistance superior to traditional Q345 steel.