Mechanical Properties Test of Butt Welds of Corroded Q690 High Strength Steel under the Coupling of Damp-heat Cycle Dipping

Abstract In order to study the mechanical property degradation rule of butt welds of Q690 high strength steel in the marine environment, high strength steel specimens under different corrosion cycles were obtained through indoor artificial acceleration tests, and uniaxial tensile and cyclic loading tests were performed to analyze the different degrees of corrosion affects the Elastic Modulus, yield strength, ductility, and hysteretic energy dissipation performance of the specimen. Based on the secondary plastic flow model and the Ramberg-Osgood model, a constitutive model for butt welds of corroded Q690 high strength steel was established. The results show that with the increase of the corrosion cycle, reddish-brown layered rust products are formed on the surface of the steel, and the metal luster is basically lost. The size of the pits continues to increase, and the maximum depth reaches 440 μm at 100 days of corrosion. Under the action of unidirectional tensile load, the yield strength and elastic modulus of the test specimens decreased by 8.28% and 7.8% after 100 days of corrosion. Based on the quadratic plastic flow model, the stress-strain curve was fitted. The curve shape parameters k1 and k2 were reduced by 26.5% and 19.3%, respectively. Under reciprocating load, the hysteresis energy of the test piece after 100d corrosion was reduced by 10.2%, the cyclic strengthening coefficient K’ and the cyclic strengthening index n’ were reduced by 13.4% and 37.3%, respectively. The research provided basic data and theoretical basis for the mechanical property degradation and reliability evaluation of high strength steel in the low-lying areas of the ocean.