Corrosion Resistance Research And Optimization Design Of Pressure Vessel In Deep Sea Service Environment

Ocean exploration is still a challenge for scientists due to the rapid development of deep-sea equipment,which provides valuable situations for ocean research.Since China is one of the major marine countries,the advanced nature of marine equipment in our country directly reflects the achievements in national defense and economic construction.A simulation on the actual working conditions of deep-sea pressure vessels is constructed in this paper,based on which we further discuss the corrosion behavior of shell materials,and provide a corrosion protection scheme.Our research here provides a theoretical and experimental basis for its practical engineering.First,the strength and stiffness of the pressure vessel in the deep-sea service environment are studied by using the contemporary mainstream engineering application finite element analysis software.A deep-sea pressure vessel model was established in Solid Works,with a parameterized size,and was imported into finite element analysis software for thermo-mechanical coupling analysis.The analysis shows that when two different materials,Q420 R and 13 Mn Ni Mo R,are given to the container,the strength and stiffness of the container meet the allowable requirements under the combined action of the temperature and pressure fields.Since the price of the 13 Mn Ni Mo R material is lower,this material is selected as the material for the container.Second,the corrosion rate of the pressure vessel shell material was measured by the weight loss method,where the changes of the macroscopic morphology were recorded by a digital camera,and the microscopic morphology was observed by SEM,and a neutral salt spray test was carried out for the high-performance anti-corrosion coating.The measured corrosion rates of Q420 R and 13 Mn Ni Mo R after immersion in simulated seawater for 180 days are about 0.038 mm/a and 0.036 mm/a,respectively.The classification and rating standards of corrosion resistance are both grade 4.The corrosion resistance of the two materials is outstanding,and the difference is within an acceptable range.The surface coatings of both materials showed good overall performance after neutral salt spray test.Consistent with the material selection of thermo-mechanical coupling analysis,13 Mn Ni Mo R is determined as the shell material of the pressure vessel.Finally,since the analysis results show that the strength and stiffness of the structure are within the allowable requirements,there is a large space for optimization.The thickness and temperature of the vessel are selected as the optimization variables,with the minimum mass and the maximum stress being the target variables,and the influence of the thickness and temperature of the vessel on the maximum stress is studied.After optimization,the total mass of the container was reduced by 4.29 kg,namely 41.97%.