Study on Slag Skin Solidification Behavior of Slag Systems for Lifting‐Mold‐Type Electroslag Remelting
Shuainan Han, Yu Zhang, Lei Liu, Chengyu Jiu, Ruixing Xue, Erfang Tian, Xin Geng, Zhouhua Jiang, Fubin LiuDuring the electroslag remelting (ESR) process, the crystallization behavior and phase evolution of molten slag significantly influence the surface quality of remelted ingots. This study systematically investigated the formation mechanisms and structural characteristics of slag skins in three CaF 2 –Al 2 O 3 –CaO–SiO 2 slag systems (60F, 40F, and 32F) during the ESR of GCr15‐bearing steel through thermodynamic calculations and multiscale characterization. The 60F slag preferentially precipitates high‐melting‐point CaO·6Al 2 O 3 (Calcium hexaaluminate, CaAl 12 O 19 , 1875°C), while the 40F and 32F slags predominantly form CaO·2Al 2 O 3 (CaAl 4 O 7 , 1765°C) and 2CaO·Al 2 O 3 ·SiO 2 (Ca 2 Al 2 SiO 7 , 1593°C), respectively. All three slag systems develop multilayered slag‐skin structures. The 60F slag skin, composed of interlocking plate‐like CaO·6Al 2 O 3 structures, demonstrates exceptional thermal stability and radial thermal insulation. This unique microstructure promotes axial heat transfer and mitigates edge‐cracking risks during ingot withdrawal. In contrast, the 2CaO·Al 2 O 3 ·SiO 2 in the 32F slag exhibits a lower melting point and enhanced fluidity during the ingot withdrawal process. This facilitates timely feeding of slag and molten metal to compensate for solidification shrinkage. Additionally, its excellent lubricating properties effectively reduce frictional damage during ESR process with ingot withdrawal or mold lifting.