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

Abstract

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% TiO2 and 2% SiO2 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 Al2O3–CaO–TiOx–MgO to MnO–SiO2–Al2O3–TiOx. Thermodynamic calculations reveal that the decrease in temperature promotes the precipitation of Ca2Ti2O5 and Ca2Ti2O6 in inclusions. As the oxygen content from reoxidation increases, the formation of SiO2 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.