Research On Corrosion Behavior Of Dissimilar Metal Welded Joints

The submerged arc welding process is used, H08Mn2MoA welding materials as filler wire is selected in this experiment, 13MnNiMo54 and 20MnMo metals of 106mm slab thickness is welded, as well as the mechanical property and microhardness of Welded joints is tested. In a room temperature, the corrosion tests are conducted by respectively putting base metal, boundary zone metal and weld metal in HCl, NaOH and NaCl solution. After corrosion, through SEM, microstructure, hardness test, the corrosion rate and corrosion thermodynamics, the mechanical properties and microstructure of 13MnNiMo54 and 20MnMo, and the corrosion behavior of the base metal, boundary zone metal and weld metal of the welded joints in sour, alkali and saline environments are analyzed and studied respectively.The test results show that in a room temperature,both tensile strength and impact energy of the welded joints are higher than the corresponding value of the base metal 13MnNiMo54 and 20MnMo,and the microhardness data of the side boundary zone of 20MnMo gets to its peak and its distribution is asymmetry. The observation and analysis of the welded joints before corrosion indicates that the metal of middle layer of the weld zone is made of fine lump ferrite, while the metal of its top layer is mainly made of thick eutectoid ferrite and acicular ferrite. After immersing base metal, boundary zone metal and weld metal in HCl solution, NaOH solution and NaCl solution respectively for 21 days, their average corrosion rate is calculated and their microstructure morphologies are analyzed, which show that the average corrosive rate of welded joint in HCI solution is the fastest, and its corrosion is also the most serious and the weld metal is the most serious part eroded. Welded joints in NaOH solution and NaCl solution are corroded far less than that in HCI solution, and after the welded joint is corroded in NaOH solution, the corrosion resistance of the metal made of its weld metal is the strongest. At last, by thermodynamic calculation and analysis, the corrosive thermodynamic behaviors of welded joints in different corrosive mediums are fixed.