Investigation on the control of rare earth content and surface quality of ingot during electroslag remelting process

Rare earth element played an important role in the carbide and solidification structure of high carbon steel. Reasonable control of rare earth content in electroslag remelting (ESR) of special steel can obviously improve the quality of steel. This paper focused on the thermodynamics between rare earth slag and steel to improve the homogeneous distribution control of rare earth element along the height of ESR ingot. The melting temperature, viscous characteristics of CaF2-CaO-Al2O3-Ce2O3-based slags were measured. The results showed that the CaO played an important role in activity coefficients of SiO2, Al2O3, Ce2O3. The content of Ce in ESR ingot increased with the increase of CaO content in slags, but the excessive CaO deteriorated the physical properties of the slag and the surface quality of electroslag ingots. When the slag compositions met the condition of CaF2: CaO: Al2O3: Ce2O3 = 50: 10: 20: 20, it not only had the low melting temperature and appropriate viscous characteristics but also could control the rare earth content in steel to a greater extent. Finally, ESR ingots with good surface and homogeneous distribution of Ce along the height of ingot were obtained.