Research on Mechanical Properties and Constitutive Model of Q355GNH Weathering Steel After Corrosion Damage

In this study, acetic acid salt spray test was carried out on Q355GNH weathering steel, and its weathering performance in industrial marine atmospheric corrosion environment was analyzed. After the corrosion tests, the monotonic tensile test was carried out to study the degradation trend of the mechanical properties of pre-corroded Q355GNH with the increase of corrosion rate, and the corrosion damage constitutive model of Q355GNH with 6 mm and 14 mm thickness was established. The results showed that the tensile strength and elongation of the weathering steel decreased after corrosion. The corrosion rate had the greatest influence on the fracture strain, followed by the yield strength and ultimate strength; the yield ratio of weathering steel was always stable after corrosion, and the tensile fracture mode was still ductile fracture; the smaller the thickness of steel was, the more obvious the decrease of mechanical properties of steel after corrosion was; with the increase of corrosion time, the constitutive curve of Q355GNH steel changed, the yield platform and plastic strengthening stage gradually became shorter, and the yield platform of 6 mm material specimen disappeared just after 40 days of corrosion. Based on the constitutive model of Q355GNH weathering steel with smooth surface, the constitutive model of pre-corroded weathering steel was proposed by introducing parameters k₁, k₂, k₃, C, which was in good agreement with the constitutive curve of Q355GNH after corrosion.