不锈钢中MnS夹杂物极易诱发点蚀，严重恶化钢的耐腐蚀性能，实施MnS夹杂调控技术或改性技术是提高不锈钢耐腐蚀性能的有效途径。以S32550双相不锈钢为研究对象，在实验室条件下采用真空感应炉冶炼不同Ce、Ti含量的试验钢，通过JSM - 6510型扫描电子显微镜、周期腐蚀失重实验、交流阻抗测试、Tafel极化曲线测试等检测方法，研究了微量Ce和Ti对不锈钢中MnS夹杂物的变性效果以及对不锈钢耐腐蚀性能的影响。结果表明：向钢中加入0.047%(质量分数，下同)Ce后，S32550钢中夹杂物由MnS变为Mn - S - Ce - O复合夹杂，夹杂物尺寸由14 μm左右减小为3 μm左右，腐蚀速率较未添加Ce时降低了63%；向钢中加入0.051%Ti后，夹杂物由MnS变为Mn - S - Ti - N复合夹杂，尺寸由14 μm左右减小为4 μm左右，腐蚀速率较未添加Ti时降低了33%；添加0.052%Ce和0.054%Ti后，夹杂物由MnS变为Mn - Ce - Ti - O复合夹杂，尺寸由14 μm左右减小到2 μm左右，腐蚀速率较未添加Ce和Ti时降低了76%。添加Ce、Ti均能够增大试验钢的容抗弧半径和自腐蚀电位，并降低自腐蚀电流，显著提高S32550钢的耐腐蚀性能，其中Ce的作用效果优于Ti，同时添加Ce和Ti的作用效果较单独添加Ce和Ti时显著。
MnS inclusions in stainless steel can easily induce pitting corrosion, which seriously deteriorates the corrosion resistance of steel. Applying MnS inclusion control technology or modification technology is an effective way to improve the corrosion resistance of stainless steel. In this paper, the S32550 duplex stainless steel was taken as the research object, and the test steels with different Ce and Ti contents were smelted in a vacuum induction furnace under laboratory conditions. The modification effects of trace amounts of Ce and Ti on MnS inclusions in stainless steel and their effects on the corrosion resistance of stainless steel were studied by JSM - 6510 scanning electron microscope, periodic corrosion weight loss test, AC impedance test, Tafel polarization curve test and other test methods. Results showed that after adding 0.047% (mass fraction) Ce into the steel, the inclusions in S32550 steel changed from MnS into Mn - S - Ce - O composite ones, the size of the inclusions was decreased from about 14 μm to about 3 μm, and the corrosion rate was reduced by 63% compared with that before adding Ce. After adding 0.051% (mass fraction) Ti into the steel, the inclusions changed from MnS into Mn - S - Ti - N composite ones, and the size was decreased from about 14 μm to about 4 μm. The corrosion rate was reduced by 33% compared with that before adding Ti. Furthermore, after adding 0.052% (mass fraction) Ce and 0.054% (mass fraction) Ti, the inclusions changed from MnS into Mn - Ce - Ti - O composite ones, and the size was decreased from about 14 μm to about 2 μm. The corrosion rate was reduced by 76% compared with that before adding Ce and Ti. Therefore, adding Ce and Ti could both increase the capacitive arc radius and self - corrosion potential of the test steel and decrease their self - corrosion current, significantly improving the corrosion resistance of S32550 steel. Besides, the effect of Ce was better than that of Ti, and the effect of adding Ce and Ti together was better than adding Ce or Ti alone.
