Effect of Trace Element Cr on Microstructures and Properties of Welded Joints of Marine Corrosion Resisting Steels

To explore the effects of trace element Cr on microstructure, mechanical performances and corrosive nature of welded joints in the virtual environment in which the bottom plates of cargo oil tanks were taken as the prototype, different joints were researched by adding wires with Cr or without Cr. The corrosion rate of the joint was calculated by weight loss of the samples before and after corrosion. However, the micro and macro morphology of the corroded samples were described by scanning electron microscope (SEM) and optical microscope (OM), and the element distribution was measured by EDS. In addition, the polarization curve was measured in the preset corrosion environment. The results indicate that the minor addition of Cr inhibits the eutectoid ferrite to some extent and refines the acicular ferrite. The mechanical performance of the joints is little affected by the addition of Cr, and the tensile strength of the base metal is lower than that of the joint, and the shock level was not changed greatly. However the impact level is the same and the hardness distribution is similar. No significant changes are observed in anti-corrosion nature by adding trace amounts of Cr, but the corrosion potential of the weld metal decreases, meanwhile, the corrosion rate increases.