Reaction Behaviour between Cerium Ferroalloy and Molten Steel during Rare Earth Treatment in the Ultra-low Carbon Al-killed Steel

In this work, the melting process and reaction behaviour of cerium ferroalloy in the liquid ultra-low carbon interstitial free steel was investigated through a special designed hot crucible experiment using standard metallographic techniques including SEM, EDS, XRF, and XRD in combination with the thermodynamic software FactSage 7.2. The evolution mechanism of cerium-containing phases in the cerium ferroalloy during the melting process was proposed. The cerium-containing phases stretched and migrated along the direction of heat flow, in further the arms of the network structures became thinner and finally dissolved into the molten steel. It was concluded that the thinner of network structures' arms, the higher of the Ce content in cerium-containing phases. During the melting process, the cerium content in the cerium-enriched phase was increased from 43.9 wt% in the matrix of the cerium ferroalloy to 90.44 wt% in the reaction zone, and the average width of the network arms was decreased from 18 mu m to 2 mu m accordingly. The main reaction products in the interface among cerium ferroalloy, molten steel, and slag were Ce2O3 and CeAlO3.