Effect of Pearlite Structure of Cerium-Containing Heavy Rail Steel on Atmospheric Corrosion

The impact of its structure against atmospheric corrosion was studied by adding Ce to the heavy rail steel to change the structure of the heavy rail steel. The U71Mn was used for smelting experiments in an intermediate frequency induction furnace, and air-cooled after rolling. The lamella spacing of the experimental steel was measured by SEM. The corrosion of the experimental steel in an industrial atmosphere was simulated in a NaHSO3 solution with a concentration of (1.0±0.05)×10-2 mol∙L-1. Thermodynamic calculation, weight loss rate, SEM, XRD and electrochemical methods were used to study the effect of pearlite on anti-atmospheric corrosion. After thermodynamic calculations, the main phase Ce2O2S was precipitated from Ce-containing U71Mn at 1600~800 ℃, thereby reduced the precipitation of MnS and reduced the harmful inclusion precipitation in steel. With the increase of Ce addition amount, the interlayer spacing of U71Mn steel pearlite decreases first and then increases. At 40×10-6, the interlayer spacing of pearlite reaches the minimum value of 0.2480 μm. As the corrosion cycle increases, the weight loss increases. In the later period of the corrosion, the weight loss rate is basically constant, and has a linear relationship with time. The slopes are 1.3755, 1.0008 and 1.3396 g∙(m2·h)-1. Compared with the addition of 40×10-6 Ce and the addition of 80×10-6 Ce, the corrosion resistance of U71Mn steel without Ce increased by 12.50% and 10.4%, respectively. In the electrochemical experiment, the currents of the three groups of samples added with 0, 40×10-6, and 80×10-6 of cerium in the fifth cycle were 1.93×10-4, 3.71×10-9 and 2.01×10-7 A, respectively. XRD phase semi-quantitative analysis of the ratios of stable and unstable products in the three groups of samples were 0.670, 1.625, and 1.11, respectively. For the analysis of the surface morphology of the corroded samples, the surface of the corroded samples are all flower-shaped γ-FeOOH, the grains with the addition of 40×10-6 Ce are the largest, the smallest are the U71Mn steel without Ce, and 80×10-6 Ce is the middle. © 2021, Editorial Office of Journal of the Chinese Society of Rare Earths. All right reserved.