Effects of Simultaneous Static and Traveling Magnetic Fields on the Molten Steel Flow in a Continuous Casting Mold

The drawback of steel fluid flow phenomena for a continuous casting mold under an electromagnetic stirrer with a traveling magnetic field is the resulting severe meniscus fluctuations due to the high-velocity and excessive downward flow in the casting direction. This can result in slab surface defects due to mold flux or inclusion entrainment. To inhibit these defects in the as-cast steel products, the implementation of braking forces using static magnetic fields in combination with a traveling magnetic field was studied in the current study. The numerical results of the fluid flow in the mold under a combined traveling and static magnetic field operation show not only 50 pct lower downward flow speed, but also more enhanced rotational flow to improve washing effects. The numerical results were validated in commercial-scale operations. The results suggest the optimized range of the ratio between the traveling and static magnetic flux densities is 65 to 75 pct to ensure steel quality improvements; this range maintains a balance between the fluid forces from the jet flow and the magnetic forces in the mold.

a _CG :

Length from the rotation axis to the center of weight of the rod (m)

α :

Tilted angle of the rod (deg)

B :

Magnetic flux density (Tesla)

B ₀ :

External magnetic flux density (Tesla)

b :

Induced magnetic flux density (Tesla)

C _D :

Drag coefficient (–)

D :

Initial length of the rod immersed from the meniscus (m)

D _proj :

Immersed depth in the vertical direction of the tilted rod (m)

D _α :

Immersed depth of the tilted rod (m)

ε :

Energy dissipation rate per mass (m² s⁻³)

F :

Lorentz force (N m⁻³)

F _im :

Fluid force of impinged jet flow (N m⁻³)

F _st :

Lorentz force of static magnetic fields (N m⁻³)

F _tr :

Lorentz force of traveling magnetic fields (N m⁻³)

g :

Gravity acceleration (m s⁻²)

H :

Magnetic field (inductance) (Wb A⁻¹)

J :

Current density (A m⁻²)

K :

Turbulence kinetic energy per mass (m² s⁻²)

L :

Total length of the rod (m)

M :

Weight of the rod (kg)

μ :

Viscosity (kg m⁻¹ s⁻¹)

μ _t :

Turbulent viscosity (kg m⁻¹ s⁻¹)

μ _m :

Magnetic permeability (H m⁻¹)

O :

Rotation axis point of the paddle rod

p :

Hydrostatic pressure (N m⁻²)

r ₀ :

Radius of the rod (m)

ρ :

Density of the fluid material (kg m⁻³)

ρ _steel :

Density of steel (kg m⁻³)

S :

Source term

σ :

Electrical conductivity (Ω⁻¹)

σ _k :

Prandtl number for the transport of turbulence kinetic energy

σ _ε :

Prandtl number for transport of the turbulent dissipation rate

t :

Time (s)

u :

Relative velocity between conductor and magnetic fields (m s⁻¹)

u _{i, j} :

Velocity vector (m s⁻¹)

v :

Velocity of fluid flow (m s⁻¹)

x _{i, j} :

Length vector (m)

Authors and Affiliations

1. Graduate School of Engineering Mastership, Pohang University of Science and Technology, Pohang, Gyeongbuk, 790-784, Republic of Korea

   Sang-Woo Han & In-Beum Lee

2. Steelmaking Research Group, Technical Research Laboratories Pohang Research Lab, POSCO, Pohang, Gyeongbuk, 790-300, Republic of Korea

   Sang-Woo Han & Hyun-Jin Cho

3. Steelmaking Department, POSCO, Gwangyang, Jeollanam-do, 545-711, Republic of Korea

   Sun-Yong Jin

4. Metallurgy Products, Industrial Automation, ABB AB, Terminalvagen 24, Bldg340, 721 59, Vasteras, Sweden

   Martin Sedén

5. Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea

   Il Sohn

Corresponding author

Correspondence to Il Sohn.

Manuscript submitted January 11, 2018.

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