Structural Optimization of Electromagnetic Swirling Flow in Nozzle of Slab Continuous Casting

doi:10.1007/s40195-018-0808-3

Abstract

Abstract:

During the slab continuous casting process, the flow field of molten steel in the mold plays a decisive role in the quality of the slab. In this paper, electromagnetic swirling flow in nozzle technology is proposed to control the flow field in mold. This technology can drive molten steel to rotate inside the submerged entry nozzle by electromagnetic force, thereby controlling the flow field. This research shows that it can reduce the impact of molten steel on the bottom of nozzle and partly reduce the negative pressure at the upper part of nozzle outlet which is even eliminated by optimizing the structure and angle of nozzle. The area of heat flux of the mold wall becomes larger, and the crest value of heat flux gets lower than that without swirling in nozzle and any nozzle optimization. The meniscus fluctuates smoothly, and the flow velocity at the top surface is within a reasonable range. The temperature field distribution in the mold is uniform which was beneficial to the growth of equiaxed crystal and decreased element segregation.

Key words: Continuous, casting, Submerged, entry, nozzle, Electromagnetic, swirling, flow, Slab, Numerical, simulation

Xiao-Wei Zhu, De-Wei Li, Chun-Lei Wu, Katsukiyo Marukawa, Qiang Wang. Structural Optimization of Electromagnetic Swirling Flow in Nozzle of Slab Continuous Casting[J]. Acta Metallurgica Sinica (English Letters), 2018, 31(12): 1317-1326.

Figures/Tables 16

Fig. 1 Geometric model including an SEN, a mold and an electromagnetic swirling flow generator used in the simulation: a wide face side view, b narrow face side view, c vertical view (unit: mm)

Table 1 Simulation parameters

Process parameters	Value
Casting speed	1.52 m/min
Domain width	1320 mm
Domain thickness	230 mm
Domain length	3000 mm
SEN depth	170 mm
ρ	7020 kg/m³
ρ _slag	3000 kg/m³
\( \mu \)	0.0062 Pa s
Specific heat capacity	680 J/(kg K)
Thermal conductivity	26 W/(m K)
Current intensity	250 A
Current frequency	50 Hz
Temperature of inlet	1550 °C
Temperature of wall	1525 °C

Fig. 2 Mesh in vertical section of the SEN and mold for Wakayama slab: a mesh in Ref. [24], b mesh used in the simulation in this paper

Fig. 3 Flow field in vertical section of the SEN with a swirl blade: a simulation result in Ref. [24], b simulation result in this paper

Fig. 4 Flow field in vertical section of the nozzle with EMSFN: a schematic of mechanical swirling flow nozzle [24], b schematic of EMSFN; c flow field in vertical section with EMSFN

Fig. 5 Distribution of magnetic flux density in nozzle axis

Fig. 6 Lorentz force distributes in middle section of EMSFN device

Fig. 7 Flow field of the molten steel in the SEN with and without swirling: a without swirling flow, b with swirling flow, c distribution of tangential velocity in middle section of EMSFN device, d wall shear stress distribution of nozzle with swirling flow

Fig. 8 Flow field of the molten steel in vertical section of the nozzle outlet: a without swirling flow, b with swirling flow

Fig. 9 Flow field distribution near the nozzle outlet after optimization: a flow field in vertical section, b flow field of nozzle outlet

Fig. 10 Flow field in horizontal section of z?=?-?500 mm: a without swirling flow, b with swirling flow

Fig. 11 Flow field in the mold: a without swirling flow (front view), b without swirling flow (top view), c with swirling flow (front view), d with swirling flow (top view)

Fig. 12 Flow field in the mold with swirling flow and nozzle rotation: a front view, b top view

Fig. 13 Distribution of wall heat flux in wide and narrow surfaces: a without swirling flow and no nozzle rotation, b with swirling flow and no nozzle rotation, c with swirling flow and nozzle rotation

Fig. 14 Meniscus profile and velocity distribution along the center line of wide top surface: a meniscus profile, b velocity distribution

Fig. 15 Temperature distribution in mold: a conventional casting, b EMSFN with optimization

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