Oxidation Weight Gain Model for Welded 30CrNiMo8 Billets Electrodes During Electroslag Remelting

The high temperature oxidation behavior of the electroslag remelting (ESR) process of welded 30CiNiMo8 billets electrode is investigated. High-temperature oxidation experiments are conducted to clarify the scale formation kinetics for the model. The steel is heated at 700–1200°C under a 21% oxygen atmosphere. The oxidation kinetics of the steel follow a parabolic law, with the oxidation rate equilibrium constant lnK = −23.801×1/T+17.866 and apparent activation energy ΔEa = 197.88 J/mol. The temperature distribution on the electrode surface is obtained by measurement and fitted vertically and horizontally. The temperature increases exponentially with the electrode height, and the temperatures on the surface cross-section are inconsistent. Finally, the oxidation weight gain model is established by applying the isothermal oxidation kinetics model, the Arrhenius equation, and the Simpson formula. The amount of FeOx carried into the slag under the industry experiment is 58.68 mg/s with the content of FeO as 65 wt%, which is established by the EDS and EBSD of the scale, and 4.77 g of aluminum addition into the slag pool every 5 minutes is suggested to reduce the FeOx potential when using four 160×160 mm welded billets electrode with a descending speed as 1.19×10−4 m/s.