Study on the effect of composite rare earths on the inclusion evolution in Al-containing steel
Tonglu Yao, Wei Wu, Longfei Li, Qing He, Chuanlei Yin, Bo Zhao, Ming LeiAbstract
Through experimental testing and thermodynamic calculations, the composite effects and differences of rare earth elements La and Ce on the inclusion evolution in Al-containing steel were studied. The experimental results showed that the typical inclusions in Al-containing steel without rare earth are CaO–Al 2 O 3 composite inclusions, sulfide inclusions such as MnS, CaS. After adding La–Ce composite rare earths with a total mass fraction of 67 × 10 −6 , the main inclusions in steel were transformed into composite inclusions of REAlO 3 , RE 2 O 2 S and incompletely modified Al 2 O 3 , CaS and so on. The proportion of inclusions measuring 2–10 μm in steel decreased by an average of 4.4 %, the average size of inclusions decreased by 25.9 %, and the average number of inclusions increased by 69.5 %. The thermodynamic calculation and FactSage analysis results indicated that the effects of La and Ce on the inclusions evolution were not the same, as rare earth content increased, the evolution path of La-containing inclusions was Al 2 O 3 + La 2 O 2 S → La 2 O 2 S → La 2 O 2 S + La x S y , while the evolution path of Ce-containing inclusion was Al 2 O 3 → Al 2 O 3 + CeAlO 3 → CeAlO 3 + Ce 2 O 3 → Ce 2 O 3 → Ce 2 O 3 + Ce 2 O 2 S → Ce 2 O 2 S, the mechanisms of La and Ce modifying inclusions were not identical. These findings provide new insights for inclusion control in composite rare earths steel.