Study On Tensile And Fatigue Properties Of Weathering Steel Under Simulated Industrial Marine Atmosphere

Weathering steel is increasingly being used in practical projects such as bridges and towers due to its excellent performance.However,the applicability of coating-free low-nickel weathering steel has not been fully demonstrated in some special environments.In this paper,aiming at one of the common atmospheric environments in industrial marine atmosphere,we conducted periodic immersion corrosion tests to carry out experimental research on weathering performance,uniaxial tensile performance and fatigue performance of weathering steel under corrosive conditions.The main research work and results are as follows :(1)A periodic infiltration accelerated corrosion test program that can simulate the industrial marine atmosphere is designed,and the corresponding relationship between the accelerated test and the natural atmospheric exposure corrosion test is established through the corrosion of Q235 B ordinary steel in the same corrosive environment.The applicability of the energized corrosion test to weathering steel is discussed,and the rust layer product after corrosion and the morphology of the steel determine that the energized corrosion test is not suitable for weathering steel.(2)Through the surface observation,matrix scanning,rust layer analysis and corrosion depth calculation of the steel after periodic infiltration and corrosion,it is found that Q355 NHD has certain weather resistance under the simulated industrial marine atmosphere,but its corrosion rate and other macro indicators are compared It is not prominent in ordinary steel.(3)The uniaxial tensile test of Q355 NHD under different corrosion time shows that after 8 weeks of periodic infiltration corrosion(corrosion depth is 0.336 mm,which is equivalent to 20 years of corrosion in industrial marine atmosphere)Q355NHD base material specimen’s yield strength and tensile strength decreased by 8.1% and 7.2%,respectively,and the butt weld specimens decreased by 14.1% and 12.5%.(4)The fatigue test study of Q355 NHD under different corrosion time showed that the design fatigue strength of Q355 NHD base metal specimens decreased by 32.0% and35.6% after periodic immersion corrosion for 5 weeks and 8 weeks;The design fatigue strength decreased by 20.7% and 30.3% respectively.After 8 weeks of corrosion,Q355 NHD still meets the fatigue design requirements of the "Steel Structure Design Standard",with a confidence level of 95% and a failure probability of not more than1%.The design fatigue strength of the base metal specimen and the butt weld specimen after corrosion have safety margins of 89.3% and 143.5%,respectively.