09CuPTi-Nb weathering steel was produced by a two-stage rolling in a hot strip rolling production line. The influence of rolling process parameters on microstructure and mechanical properties were investigated. It shows that microstructure of three test steel is mainly acicular ferrite and bainite. When a final cooling temperature is 530℃ and cooling rate is 25℃/s, microstructure is composed of fine and homogeneous lath bainite. Yield strength and tensile strength is 617MPa and 702MPa, respectively, and ductile-brittle transition temperature is lower. At this condition the tested steel has high strength and toughness. The corrosion evolution of B sample of 09CuPTi-Nb weathering steel and reference steels in a simulated industrial atmosphere environment was studied. It shows that the corrosion rate increases with increasing the wet / dry cycles in the initial stage of the test, however it decreases in the latter stage of the test. Corrosion rate of 09CuPTi-Nb weathering steel is near to SPA-H steel and lower than that of Q345 steel. Rust layer of 09CuPTi-Nb weathering steel is divided into outer and inner layers, and inner rust layer is dense and mainly composed of α-FeOOH and a little of γ-Fe2O3 composition. Rust layer of Q345 steel is composed of α-FeOOH, γ-Fe2O3 and Fe3O4 composition. The electrochemistry test indicates that the corrosion product can promote the cathodic process and restrain the anodic process.
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Footnotes
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