Novel Opposite Stirring Mode in Bloom Continuous Casting Mould by Combining Swirling Flow Nozzle with EMS
Abstract
:1. Introduction
2. Model Description
2.1. Assumptions
- (1)
- The molten steel flow in the mold cavity is a steady-state, incompressible flow process. The density, the viscosity, and the specific heat were assumed to be constant over temperature.
- (2)
- The influence of mold oscillation and mold curvature on the melt flow was not considered.
- (3)
- Flux or slag layer was considered on top of the molten metal free surface only for insulation.
- (4)
- The latent heat of the peritectic transformation and the joule heating generated by the induced current compared to the latent heat of fusion were considered to be negligible [12]. The mushy zone was treated as a porous medium, wherein the melt flow obeyed Darcy’s law.
- (5)
- The effect of melt flow on the electromagnetic field was ignored due to the small magnetic Reynolds number (about 0.01 [13]) in the stirring region.
- (6)
- The iron core of the stirrer was assumed to be magnetically linear with a constant permeability [13]. The cooling water jacket of the CC mold, the stainless steel protective jacket of the EMS, and the other insulation material in the EMS device were all simplified as a paramagnet in this model.
2.2. Macroscopic Transport Model
2.3. Solidification Model
2.4. VOF Model
2.5. Boundary Conditions and Computational Procedure
2.5.1. Boundary Conditions
2.5.2. Computational Procedure
3. Results and Discussions
3.1. Electromagnetic Field
3.2. Fluid Flow and Heat Transfer
3.3. Level Fluctuation and Flow Condition below the Meniscus
4. Conclusions
- The opposite stirring mode in the mold cavity can be formed by adopting SFN plus with M-EMS. Here, a swirling flow in the anti-clockwise direction generated by SFN, and the other swirling flow in the clockwise direction induced by M-EMS are observed at the areas with a distance ranging from 0 m to 0.11 m and 0.218 m to 1.4 m from the meniscus, respectively.
- As compared to the case of a bilateral-port nozzle plus with M-EMS, the soundness and centerline segregation of the as-cast bloom can be improved remarkably, and the fluctuation range of carbon segregation at the strand axis reduces from 0.16 to 0.06 because of the better superheat dissipation effect in the mold cavity by adopting the SFN plus with M-EMS.
- The opposite stirring mode generated by the SFN plus with M-EMS can build a steady bulk flow below the meniscus in the mold cavity. The magnitude of mold level reduces from 5.6 mm to 2.3 mm, as compared to the case of the bilateral-port nozzle plus with M-EMS.
- The formation reason for the deep erosive slag line on the external wall of the bilateral-port nozzle can contribute to the higher meniscus level, the impact flow with a larger melt radial velocity, and the vortex flow near the nozzle wall when compared to the case of SFN plus with M-EMS.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Models | Equations | Variables * | ||
---|---|---|---|---|
Fluid flow model | Continuous | 1 | 0 | 0 |
Momentum | ||||
Turbulent kinetic energy | ||||
Turbulent energy dissipation rate | ||||
Heat-transfer model | Enthalpy | 0 |
Parameters | Inner Diameter (Di), m | External Diameter (Do), m | Outlet Height (H), m | Outlet Width (W), m | Outlet Angle, deg | Immersion Depth, m | |
---|---|---|---|---|---|---|---|
Nozzle Types | |||||||
Swirling flow nozzle | 0.050 | 0.1 | 0.045 | 0.022 | 15 | 0.10 | |
Bilateral-port nozzle | 0.050 | 0.1 | 0.050 | 0.040 | 15 | 0.10 |
Parameters | Value | Parameters | Value |
---|---|---|---|
Density of molten steel | 7200 kg·m−3 | Mold effective length | 0.7 m |
Thermal conductivity of steel (solid phase) [24] | 26 W·m−1·K−1 | Model length | 1.4 m |
Thermal conductivity of steel (liquid phase) [24] | 39 W·m−1·K−1 | Viscosity of molten steel | 0.0062 kg·m−1·s−1 |
Liquidus temperature of molten steel | 1748 K | Latent heat of molten steel | 272 kJ·kg−1 |
Solidus temperature of molten steel | 1658 K | Specific heat of molten steel | 725 J·kg−1·K−1 |
Density of air | 1.225 kg·m−3 | Viscosity of air | 1.789 × 10−5 kg·m−1·s−1 |
Thermal conductivity of air | 0.0242 W·m−1·K−1 | Specific heat of air | 1006 J·kg−1·K−1 |
Relative permeability of steel, air, and copper mold [13] | 1 | Iron core relative permeability [13] | 1000 |
Molten steel conductivity [13] | 7.14 × 105 S·m−1 | Copper mold conductivities (T = 298 K [25] and 423 K [25]) | 4.7 × 107 and 3.18 × 107 S·m−1 |
Inlet velocity | 0.716 m/s | Inlet temperature | 1781 K |
Outlet velocity | 0.01033 m/s (0.62 m/min) | Heat flux density of mold wall [26] |
Parameters | Value | Parameters | Value |
---|---|---|---|
Sectional dimension | 320 × 425 mm2 | Strand adopted swirling flow nozzle | I |
Casting speed | 0.62 m/min | Strand adopted bilateral-port nozzle | II/III/IV/V |
Steel grade | 65 Mn | Running current and frequency of F-EMS | 600/5 Hz |
Running current and frequency of M-EMS | 500 A/2.5 Hz | Centre location of M-EMS | 0.465 m (below the meniscus) |
Height of M-EMS | 0.40 m | Inner and external diameter of M-EMS | 0.836 m/1.236 m |
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Sun, H.; Li, L.; Liu, C. Novel Opposite Stirring Mode in Bloom Continuous Casting Mould by Combining Swirling Flow Nozzle with EMS. Metals 2018, 8, 842. https://doi.org/10.3390/met8100842
Sun H, Li L, Liu C. Novel Opposite Stirring Mode in Bloom Continuous Casting Mould by Combining Swirling Flow Nozzle with EMS. Metals. 2018; 8(10):842. https://doi.org/10.3390/met8100842
Chicago/Turabian StyleSun, Haibo, Liejun Li, and Chengbin Liu. 2018. "Novel Opposite Stirring Mode in Bloom Continuous Casting Mould by Combining Swirling Flow Nozzle with EMS" Metals 8, no. 10: 842. https://doi.org/10.3390/met8100842