Heat transfer in ESR slags

Abstract

The extensively published models of the ESR process assume a singular value of the slag thermal conductivity and employ that value in a format which assumes heat conduction entirely by a phonon mechanism. In this work we investigate the possibility that the mechanism is a phonon/ photon mechanism in a slag which is diathermanous. The conclusion is that such a model assumption better represents the practical behaviour of the process and should be used in model structures. It is also suggested that the concept has a wider application to other metallurgical processes which use slags having some degree of photon conductivity.

Effect of Different Remelting Parameters on Slag Temperature and Energy Consumption during ESR

“…This effect may be partially the result of a change in the slag heat balance due to a change in the slag thermal conductivity from a phonon mechanism in low-CaF 2 slags to one of photon conductivity in high-CaF 2 compositions. 19) Energy consumption for the lab scale remelting of two Ni-base-alloys and one bearing steel reported in 20) for general ESR operation ranges from 1 265 to 1 587 kWh/t. This value can be reduced to 735-924 kWh/t by an additional electrode, acting also as thermal barrier in the upper part of the mold.…”

“…Changing the slag system from pure CaF 2 to CaF 2 + 25% Al 2 O 3 at a similar slag temperature of about 1 650°C almost tripled the slag skin thickness, which may also be an indication of the change in slag thermal conductivity mechanism as oxide is added to pure fluoride. 19) However, an in-depth analysis of the corresponding overall heat transfer coefficient indicates, that the effect of the slag temperature and the related slag skin thickness is only in the range of about 30%. 2,27) A strong influence of the slag temperature on the thickness of the slag skin was also documented in 28) for two different slags.…”

“…Athough the power density leads to the above dependence of temperature distribution on slag resistivity, the same tendency is also supported by the changes in slag thermal conductivity due to the addition of oxides to a CaF 2 base. 19) Generally it can be concluded that inner slag temperatures are usually in the range of 1 650 to 1 750°C but depend also strongly on the power input. The temperature distribution inside the slag but more important towards the free slag surface and the mold wall is substantially affected by the slag composition.…”

Optimization of Process Parameters for ESR Waspaloy Superalloy by Numerical Simulation

“…The fluid flow in slag pool and molten pool is mainly driven by buoyancy and electromagnetic force, and the flow is turbulent [ 21 , 22 ]. Therefore, the fluid flow in slag pool and molten pool can be controlled by continuity equation and Navier–Stokes equation, as shown in Equations (7) and (8), and the turbulent stirring degree can be calculated by RNG K–ε model, as shown in Equations (9) and (10):…”

Agents of exploration and discovery

“…Early research in the area focused on induction of numeric equations (Langley 1981; Langley and Zytkow 1989), sometimes referred to as equation discovery (Todorovski 2011). Initial results involved examples from the history of physics and chemistry (Langley et al 1987), but later endeavors have produced novel results in metallurgy (Mitchell et al 1997), ecology (Todorovski, Džeroski, and Kompare 1998; Todorovski et al 2003), and other scientific fields. Work on the problem has continued unabated, with more recent efforts examining classical physics (Wu and Tegmark 2019), fluid dynamics (Bruntona, Proctor, and Kutz 2016; Raissi and Karniadakis 2018), visual attention (Lane et al 2016), and macroeconomics (Georgiev and Kazakov 2015).…”