Effects of the electromagnetic stirring on the removal of inclusions of oxide from liquid steel

Abstract

This study concerns the rate of removal and the localization of oxide inclusions during the deoxidation of an electromagnetically stirred steel bath. Experiments were conducted at laboratory scale, either with 1 kg or 0.5 kg of iron in a coreless induction furnace. Induction currents were in the frequency range 4.7 to 28.1 kHz. From the estimation of the kinetic energy of stirringEc and the turbulent diffusivity coefficientDp, it was found that the rate of removal of alumina clusters depends only onEc, whereas the rate of removal of silica inclusions depends also on the intensity of the electromagnetic forces. By means of the resolution of the Navier Stokes’ equation, the stream line pattern of the movement is compared with the localization of radioactive oxide inclusions. It was found that the size of the upper recirculating loop determines the quantity of inclusions removed through the free surface. It seems that whatever scale is considered, laboratory scale or plant scale, the use of electromagnetic stirring with a stationary field could enhance the rate of removal of inclusions and modify the location of the inclusions in the ladle. List of Symbols

μ :

Magnetic permeability Henry m^-1

σ :

Electrical conductivity Ω^-1 m^-1

ω :

Pulsation of the electromagnetic fields sec^-1

δ :

Depth of penetration of eddy currents m

R :

Crucible radius m

Ru :

Dimensionless parameter

J :

Current density A m^-2

B :

Magnetic field V sec m^-1

A :

Vector potential V sec

t :

Time sec

ϕ :

Phase of the vector potential

v :

Kinematic viscosity m^-2 sec^-1

π :

Density Kg m^-3

Ω :

Vorticity

ψ:

Stream function

Ec :

Kinetic energy

Ej :

Joule energy

Um :

Mean velocity

Dp :

Turbulent diffusivity

τ_1/2 :

Half time of deoxidation