Gas–liquid two-phase flow affects electrolyte circulation and chlorine gas transport in the electrolysis cell. This study comparatively evaluates how anode–cathode distance (ACD), anode perforation number, anode bottom geometry, and the Lorentz force contribution affect cell-scale hydrodynamics in a Downs cell. A three-dimensional Euler–Euler two-phase flow model with standard k–ε turbulence closure was implemented in COMSOL Multiphysics. In the multi-physics framework, electric current and magnetic field calculations were performed sequentially, and the resulting Lorentz force density was applied as a volumetric source term in the electrolyte momentum equation. Mesh sensitivity was examined using a two-dimensional computational domain, while published molten salt electrolysis simulations were used only for a qualitative plausibility check because direct experimental validation was unavailable. Increasing the ACD from 33 to 63 mm generally reduced the calculated electrolyte velocity on the reported section of the interelectrode channel. For the 4-, 6-, 8-, and 12-hole anodes, the maximum electrolyte velocities were 0.35, 0.38, 0.44, and 0.49 m/s, respectively, and the corresponding vortex counts were 8, 8, 9, and 10. Among the cases examined, the 8-hole configuration showed a comparatively balanced hydrodynamic response, combining relatively high electrolyte velocity with moderate vortex development. The indented bottom anode produced 11.1 pct higher local fluid shear stress than the straight cylinder anode. Including the Lorentz force term increased the maximum z-direction electrolyte velocity from 0.678 to 1.095 m/s, corresponding to an increase of 61.6 pct, and reduced the spatial extent of the recirculation region above the electrodes. These results provide comparative hydrodynamic guidance for evaluating anode-structure effects under the stated modeling assumptions.
Near-eutectic A413 (Al–12Si) is one of the most fluid aluminum casting alloys and is widely suitable for thin-walled castings, including those produced from recycled feedstock. However, the effects of section thickness and melt cleanliness on its fluidity have not been sufficiently quantified. In this study, A413 alloy was gravity die cast into a four-channel mold with 2, 4, 6, and 8 mm sections and into a spiral mold. Melt cleanliness was evaluated using reduced pressure test (RPT) density/porosity measurements and the K-mold index. Twelve castings were produced: nine from degassed primary ingot at 660 °C, 700 °C, and 740 °C with pouring heights of 50, 100, and 150 mm, and three from untreated scrap under matched conditions. The multi-section response was summarized using the Fluidity Index, FI = Σ(Li/ti). Pouring temperature was the dominant variable: at a 50 mm pouring height, FI increased from 55.1 to 118.2 as temperature rose from 660 °C to 740 °C. Multiple linear regression showed that temperature was statistically significant (p = 0.002), whereas pouring height was not (p = 0.24). Melt cleanliness had a strong effect on fluidity. The degassed melt showed 2.652 g/cm3 density, 0.30 pct porosity, and K = 0.28, while untreated scrap showed 2.523 g/cm3, 5.15 pct, and K = 1.80. Under matched conditions, untreated scrap caused an FI loss of up to 41 pct. Spiral length correlated strongly with FI (r = 0.88), while FlowCast simulations overestimated flow distance by approximately 1.5 to 2.7 times. These results demonstrate that melt cleanliness is a critical fluidity variable in recycled A413 casting.
This study investigates the interfacial reaction between high-Mn high-Al steel and refining slag in gas-stirred ladles. An uncoupled model was established by integrating computational fluid dynamics (CFD) with the effective equilibrium reaction zone (EERZ) theory. By analyzing the transient characteristics of the slag–steel interface under varying argon blowing conditions, the effects of initial Al content, plug configuration, and slag composition on desulfurization efficiency and steel cleanliness were elucidated. The results indicate that the slag eye area expands with increasing argon flow rates. However, a single-plug configuration exhibits an inflection point at 250 NL/min, where the expansion rate drops to 41 pct of its initial value. A critical flow rate exists between 250 and 500 NL/min: a single-plug setup yields a larger slag eye at low flow rates, whereas the dual-plug configuration dominates at high flow rates. While dual-plug operation markedly promotes interfacial mass transfer, flow rates above 500 NL/min induce severe interfacial instability. N pickup via the slag eye is the primary mechanism at 1 wt pct Al, whereas AlN precipitates when Al exceeds 5 wt pct. Higher Al content reduces Al2O3 formation and promotes MgO reduction, leading to a transition of inclusions toward AlN and MgAl2O4 spinel. The total amount of MgAl2O4 is optimized under low flow single-plug (100 NL/min) or high flow dual-plug (≥ 500 NL/min) conditions, whereas AlN suppression demands an opposing strategy. Higher CaO/Al2O3 or lower Al2O3/SiO2 ratios enhance desulfurization and accelerate the transition of Al2O3 into MgAl2O4, CaMg2Al16O27 and CaAl4O7. This effect tends to stabilize beyond a CaO/Al2O3 ratio of 1.0 or an Al2O3/SiO2 ratio of 3.8.
A 1:3-scale water model was established to investigate mold slag emulsification and entrainment in a continuous casting mold. Mold-level fluctuation, internal flow field evolution, and slag-phase morphology were characterized using wave height measurements, particle image velocimetry, and image-based quantitative analysis. The results show that slag emulsification proceeds through initial, stable, and complete stages, driven mainly by argon bubble motion and gas–water–slag interaction. Four entrainment modes were identified: shear-induced, vortex-induced, bubble breakup-induced, and emulsified suction-induced entrainment. Casting speed mainly intensified the submerged entry nozzle (SEN) jet, mold-level fluctuation, and shear near the slag layer, thereby markedly promoting slag entrainment; the number of entrainment events increased from 1 to 36, and the cumulative entrainment area increased from 0.65 to 47.51 cm2. Increasing gas flow rate significantly increased the emulsified slag layer thickness, while the entrainment area first increased and then decreased, peaking at 1.64 L/min. Increasing SEN immersion depth weakened near-surface turbulence and reduced mold-level fluctuation, causing the entrainment area to decrease continuously from 57.35 to 0.329 cm2, while the emulsified slag layer thickness increased and then stabilized. These findings clarify the coupled effects of operating parameters on slag emulsification and entrainment.
Oxide inclusions strongly influenced the deformation compatibility of tire cord steel during hot working. In this study, the composition, size, number, spatial distribution, and deformation (morphology and aspect ratio) of oxide inclusions were quantitatively characterized across the full thickness of the billet and the full diameter of the first-pass (1st) hot-rolled rod using an automated microscopy system. The spatial distribution of inclusions changed after hot rolling: the average SiO2 content of the detected inclusions increased from 56.8 to 65.7 wt pct, with SiO2-rich inclusions becoming more prevalent in the near-surface region of the 1st hot-rolled rod. The maximum number densities of SiO2-rich and SiO2–MnO–Al2O3 inclusions were 5.10 mm−2 in the near-surface region and 4.76 mm−2 in the central region of the hot-rolled rod, respectively. The rolling process elongated the inclusions along the rolling direction. The average equivalent-area diameter decreased from 3.07 to 2.70 μm, whereas the average aspect ratio increased from 1.56 to 8.71. Moreover, the highest average diameter and aspect ratio were consistently observed in the central region. The deformation behavior of inclusions was strongly associated with their high-temperature deformability, which depends on their melting temperature (Tm), viscosity (η940), flow stress, and internal phase constitution. Multicomponent silicate inclusions with low Tm (< 1550 °C) and low η940 (< 16.12 ln(Pa·s)) exhibited excellent deformability, with aspect ratios exceeding 10 in the center. In contrast, S-type inclusions, with high Tm (> 1670 °C), underwent almost no deformation and restricted the final deformation of SiO2–MnO inclusions, resulting in an average aspect ratio of only 6.82 in the center.
