Arc Characteristics and Slag Pool Shape Evolution During the Arc-Striking Stage of the Protective-Atmosphere Electroslag Remelting Process

In protective-atmosphere electroslag remelting (P-ESR), the sealed furnace prevents direct observation of the slag state, making it difficult to define a clear endpoint during arc-striking and thereby complicating melting-time control and reducing the quality and yield of the initial ingot. A three-dimensional, transient, coupled electromagnetic-flow-temperature model for a 10-ton ESR furnace, operated with 50 Hz AC and currents between 4100 and 6000 A was established. The arc exhibits a bell-shaped profile with peak temperature near the cathode spot, motivating a Gaussian heat-flux model at the slag pool surface. Heat balance analysis indicates that approximately 65.5 pct of input power is consumed to melt the slag and approximately 17.6 pct is consumed to preheat the electrode, enabling a practical control model for slag-melting time. Industrial trials were conducted to validate the accuracy of the melting-time prediction model. A stabilized slag resistance of 6.7 mΩ was adopted as the complete-melting criterion, and the stabilized time was evaluated against the model-predicted melting time. The slag-melting time was further supported by a metallographic examination of the ingot bottom, which confirmed the absence of slag entrapment.