Research On Corrosion Performance Of X80 Pipeline Steel Welded Joints

As the main steel for long-distance pipelines,X80 pipeline steel has attracted much attention for its mechanical properties and corrosion resistance.However,when the welding of X80 pipeline steel is completed,the structure and corrosion resistance of the weld will undergo certain changes.It will have a certain impact on its service in a complex environment.Therefore,it is very important to research on the microstructure,performance,and corrosion behavior of X80 pipeline steel welded joints,which will provide certain theoretical support for the application of X80 pipeline steel.The main research contents and conclusions of this paper are as follows:(1)Through the metallographic corrosion experiment,the metallographic structure of the X80 welded joint is analyzed.The results show that the heat-affected zone is dominated by the coarse austenite structure,the base metal area is uniform acicular ferrite,and the weld area is needle Shaped ferrite and bainite;the hardness test results of the welded joints show that the center of the weld has the lowest hardness,and the hardness value gradually increases to both sides;the outer surface hardness of X80 pipeline steel is slightly higher,and the inner surface hardness value is relatively low.(2)The electrochemical experiment results of X80 base metal and welding seam in an unstressed state show that in the simulated solution of acid red soil,the base metal has a more negative corrosion potential and a larger corrosion current density than the weld seam;The force-electrochemical corrosion experiment of X80 base metal and welding seam results show that the greater external force,the more negative corrosion potential,and when the external force is the same,the base metal has a more negative corrosion potential and higher corrosion tendency than the welding seam.(3)The welding simulation results show that the welding residual stress in the center of the weld is the largest;the force-electrochemical corrosion numerical simulation results show that the welding residual stress will affect the corrosion performance of the material,and under the same welding residual stress,the greater internal pressure of the pipeline,the more negative corrosion potential of the weld,the greater corrosion current density,and the more serious corrosion.(4)Numerical simulation results of weld-base metal corrosion galvanic couple show that in the weld-base metal galvanic couple,The base metal is corroded for the anode,and the weld is protected for the cathode;The width of the weld has a great effect on the anodic corrosion performance.The wider weld,the greater the anodic coupling current,the higher the anodic corrosion rate,and the greater the anodic electrode corrosion deformation,while the width of the base metal has little effect on the anodic corrosion performance.