Numerical Simulation on Saffman Force Controlled Inclusions Removal during the ESR Process

Abstract

Electroslag remelting (ESR) is an effective method for removing nonmetallic inclusions from steels or alloys. The main stage of inclusion removal during ESR is the aggregation of liquid metal film (LMF) to form droplets at the consumable electrode tip. In this study, a lab-level ESR experiment was carried out. The number and size of inclusions at the characteristic position of the electrode were quantitatively counted. The number of inclusions in the center position of LMF were larger than that in other regions. To elucidate these phenomena, a two-dimensional mathematical model was established to study the migration of inclusions in LMF. The results indicate that due to the large velocity gradient in LMF, the Saffman force is strong enough to offset the buoyant force and drag the inclusions toward the slag/LMF interface (SFI), where the inclusions will be dissolved in the SFI region by the molten slag. This study demonstrates that the Saffman force plays a key role in the removal of nonmetallic inclusions in LMF during the ESR process.

Electrode manufacture for the remelting processes

“…If this latter circumstance is the case, the inclusions would rapidly dissolve in, or react with, an ESR process slag. An example of this effect is shown by Sun et al [43] where both oxide and TiN inclusions are found collected in the liquid metal film on the electrode/slag interface. Using the data provided by Burel [15], a spherical alumina inclusion of 40 µm diameter would fully dissolve in ∼2 s; a 5 µm inclusion in <1 s. Voronov et al [24] studied the removal of MgO inclusions and reports that an oxide inclusion of 15 µm diameter should fully dissolve in the slag in 1 s. It could be reasonably assumed, therefore, that most if not all, inclusions contacting the ESR process slag during electrode melting are fully dissolved into the slag or are substantially modified by it.…”

“…acidic silicates or MnO). Dong [14] reports that in the electrode melting process, many of the oxide inclusions are rejected to the slag/ liquid metal interface by surface tension forces, the mechanism possibly also including the Saffman effect [43]. If this latter circumstance is the case, the inclusions would rapidly dissolve in, or react with, an ESR process slag.…”

Decrease of Nozzle Clogging through Fluid Flow Control

“…In previous works [4,48] it has been established that the leading forces for the particle motion are buoyant, drag and Saffman, being possible to avoid the pressure gradient force and virtual mass force. However, to obtain more accurate results in the present research work, all forces mentioned above are considered in the mathematical simulation.…”