Control of Steel Composition and Evolution of Inclusions During Electroslag Remelting of NiCrMoV High‐Strength Steel

Herein, the control of steel composition and evolution of inclusions during the electroslag remelting (ESR) of NiCrMoV high‐strength steel are investigated by laboratory experiments and thermodynamic calculations. The effects of slag systems, atmosphere protection, and surface quality of the consumable electrode are discussed. Results show that slag containing 5% TiO 2 and 2% SiO 2 is beneficial for controlling Ti and Si losses in steel during the ESR. Using argon gas protection reduces the total oxygen (TO) and nitrogen contents in ESR ingots and improves steel cleanliness, while it has little influence on the types of inclusions. The oxide scales on the electrode surface lead to the reoxidation of liquid steel during the ESR. The TO content increases to 113 ppm and Si, Ti, Als, and Mn contents in ESR ingots are considerably reduced. The inclusions are transformed from Al 2 O 3 –CaO–TiO x –MgO to MnO–SiO 2 –Al 2 O 3 –TiO x . Thermodynamic calculations reveal that the decrease in temperature promotes the precipitation of Ca 2 Ti 2 O 5 and Ca 2 Ti 2 O 6 in inclusions. As the oxygen content from reoxidation increases, the formation of SiO 2 and MnO in inclusions in ESR ingots is promoted. Appropriate process parameters are proposed to control the composition and cleanliness of steel during the ESR.