Effects of La and Ce treatment on changes in inclusion characteristics of 304 stainless steel during industrial production

The extent of inclusion modification achieved after adding various contents of rare earth elements to 304 stainless steel in practical applications was explored, additionally the pitting behavior of the inclusions in a chloride environment before and after modification. The mechanisms by which the compositions of inclusions evolved throughout the production process in response to various rare earth element (REE) contents were investigated, and their consequential impact on the corrosion resistance of steel was evaluated. The results indicated that with increasing rare earth content from 0 to 50.37 × 10⁻⁶, REE inclusions were preferentially generated in the following order when they were modified: REAlO₃ → RE₂O₂S → RE₂O₃. The inclusion size and density were negatively correlated and positively correlated with the REE content in 304 stainless steel, respectively. The formation of Mg–Al spinel and MnS in the continuously cast billet was suppressed by the addition of rare earth elements. The voltage potential differences between the REE-modified inclusions and the steel substrate were obviously less than those between the unmodified inclusions and the steel substrate. The addition of rare earth elements contributed to the improvement in the corrosion resistance of 304 stainless steel.