DH36 Steel Plate Welded Joint Research In The Seawater Corrosion Mechanism Under Different Stress

With the development of science,marine industry begins to flourish.Domestic and foreign research on corrosion problem of marine steel also witnesses an increasing deepening.In marine engineering,large steel structure is ubiquitous.Both residual stress caused by manufacturing or workload of components have led to large and thick steel structure under stress value of complex distributions and high value.Moreover,stress value is the key factor that will influence structural corrosion.Therefore,it is significant to study the corrosion problem of the large and thick plate welding structure stress.Seawater corrosion mechanism topic of welding joint of DH36 steel plate in different stresses takes ABAQUS software to create simplified model to carry out numerical simulation to thick plate DH36 steel butt joint surface’s residual stress,which largely improves the calculation efficiency of multi-layered and multi-channel welding types’ numerical simulation.Additionally,impact indentation method is taken to verify the simulated results of the simplified model.Based on the stress distribution of numerical simulation,together with four-point bending test assisted electrochemical test to study the influence of the tensile stress on the corrosion electrochemical characteristics of DH36 steel base material,welding seam and heat-affected zone.By weight-loss method to measure the corrosion rate of DH36 steel under different tensile stresses.(1)By ABAQUS to create simplified model and conclude the residual stress distribution on the surface of DH36 steel’s welding joint.Apart from the arc start and arc end of the first welding seam,horizontal and vertical residual stresses along the welding direction of the joint cover surface are all performed as tensile stress.In the midpoint of the third welding seam,the maximum tensile stress value of 310 Mpa will be concluded.Horizontal and vertical residual stresses in the middle part of the welding seam perpendicular to the direction of welding seam is shown as tensile stress,with compressive stress around.In the midpoint of the fourth welding seam,it is the maximum tensile stress value of 349 Mpa.(2)By indentation impact method to measure the residual stress distribution on the surface of DH36 steel welding joint and verify the simulated results made by ABAQUS simplified model,it turns out that measured results of indentation impact method have good coherence to the simulated results of the simplified model.This indicates that the numerical simulation simplified model of multi-layered and multi-channel welding is effective and feasible.(3)Four-point bending test together with electrochemical test are taken to study the influence of tensile stress in three areas of welding seam,heat-affected zone and base material on the corrosion resistance.It turns out that the welding seam is the best in the same tensile stress,and base material takes the second place,while heat-affected zone performs the worst.In the same place under different tensile stress,the corrosion resistance of materials will reduce with the increase of tensile stress.When the tensile stress is more than 240 Mpa,pitting corrosion electrochemical characteristic will happen.(4)By weight-loss method to observe the corrosion morphology of DH36 steel under different tensile stresses,and measure the corrosion speed.It turns out that the corrosion speed of DH36 will increase with the increase of tensile stress,and obvious corrosion pit will happen under tensile stress of 240 Mpa and 320 Mpa.(5)According to the results of electrochemical test and weight-loss method,combined with pitting penetration model to analyze the seawater corrosion mechanism of DH36 thick steel plate welding joint under tensile stress.Tensile stress has improved the instability of metal thermodynamics that promotes the occurrence of corrosion..