Cryogenic Impact Toughness And Corrosion Study Of S30403 Stainless Steel Welded Joint

Austenitic stainless steel(ASS)is a kind of stainless steel with austenite as matrix phase,which has good mechanical property and corrosion resistance.In some special environments,the impact resistance and corrosion resistance of S30403 stainless steel are important factors that can affect its life.Therefore,S30403 stainless steel welded joints under different heat treatment conditions are used as materials in this paper.The effect of heat treatment on its cryogenic impact toughness and corrosion property are studied through experiments.Based on the experiment data,the pitting corrosion and galvanic corrosion of S30403 stainless steel welded joints are simulated by phase field method.The specific works and results of this paper are as follows:(1)Microstructure analysis: The microstructure of S30403 austenitic stainless steel joints were observed by OM,SEM and TEM respectively.The effect of heat treatment process on the microstructure of the joints was studied.It can be concluded that the microstructure and size of the joints with different heat treatment processes are different.When the heat treatment temperature is very high,chromium rich carbide will appear near the grain boundary.(2)Study on cryogenic impact toughness: The effect of heat treatment process on the cryogenic impact toughness of S30403 stainless steel weld was studied by cryogenic impact toughness test.The results show that the average impact values of S30403 austenitic stainless steel welds under different heat treatment processes decreased in different degrees compared with welded weld,and the decrease degree increased with the increase of heat treatment temperature.(3)Study on Corrosion property: The effect of heat treatment process on the electrochemical corrosion property of S30403 stainless steel weld was studied by electrochemical corrosion test.It can be concluded that heat treatment makes the corrosion sensitivity of S30403 stainless steel weld increase,and the corrosion sensitivity increases with the increase of heat treatment temperature;Heat treatment makes the corrosion rate of S30403 stainless steel weld decrease,and the degree of reduction increases with the increase of heat treatment temperature;Heat treatment makes the galvanic corrosion effect of S30403 stainless steel weld decrease,and the degree of reduction increases with the increase of heat treatment temperature.(4)Pitting simulation: The pitting of S30403 stainless steel weld was studied by phase field theory and relevant test data.It can be verified that :In the activation-control stage of pitting,the depth of pitting is proportional to the time;In the diffusion-control stage,the depth of pitting is proportional to the 1 / 2 power of time;The anodic polarization curve calculated from the simulation results fits well with the Tafel curve in the activation control stage;The interface dynamic parameter is linear with the interface movement rate;The larger the interface dynamic parameter is,the faster the corrosion rate is,and the deeper the pit is;The diffusion distance of every point on the boundary of two-dimensional pitting is equal at the same time.(5)Galvanic corrosion simulation: The galvanic corrosion of S30403 stainless steel weld was studied by using phase field theory,galvanic corrosion theory and relevant test data.It can be verified that :The phase field guiding equation and galvanic corrosion guiding equation can be coupled through the interface dynamic parameter;The interface dynamic parameter in the phase field guiding equation is related to the corrosion current density in the galvanic corrosion guiding equation;The cathode(austenite)in S30403 austenitic stainless steel will be protected by anode(ferrite)during galvanic corrosion;The corrosion of anode is not uniform,it is related to the distribution of current density.The results show that the phase field is a valuable method to understanding corrosion process.