Effect of rare earth Ce treatment on the microstructure and properties of 430 ferritic stainless steel bearing Sn and Cu

Abstract

The effects of rare earth Ce on purifying molten steel, modifying inclusions and micro-alloying in 430 ferritic stainless-steel bearings with Sn and Cu has been studied in this paper. The results demonstrate that Ce can purify molten steel, modify inclusions, enhance the mechanical properties and improve the pitting and corrosion resistance of the experimental steel. Ce effectively purifies the molten steel, reducing the total oxygen (T. O) content to as low as 0.00086 wt.% and sulphur (S) content to 0.0020 wt.%. The transformation of inclusions in the steel follows the sequence of MnS·Al2O3 → CeAlO3 → Ce2O2S → Ce2O3 with increasing Ce content. The number of inclusions initially decreases and then increases, with the experimental steel containing 0.012 wt.% Ce showing the best cleaning effect. Additionally, Ce treatment only slightly improves the mechanical properties of the experimental steel, but significantly enhances its pitting corrosion resistance and intergranular corrosion resistance by changing the enrichment state of carbides and impurity elements at the grain boundaries. In detail, Ce can partially inhibit the precipitation of M23C6 type carbides at grain boundaries, thereby improving the intergranular corrosion resistance of the experimental steel.