18(2014-032).fmISIJ International, Vol. 54 (2014), No. 10, pp.
2273–2282
Magnetohydrodynamic Phenomena, Fluid Control and Computational
Modeling in the Continuous Casting of Billet and Bloom
Shenqiang WANG,1)* Gonzalo ALVAREZ DE TOLEDO,2) Kari VÄLIMAA3) and
Seppo LOUHENKILPI1)
1) Department of Materials Science and Engineering, Aalto
University, Vuorimiehentie 2K, FI-02150, Espoo, Finland. 2) Gerdau
Investigación y Desarrollo Europe, 48970 Basauri Vizcaya, Spain. 3)
Ovako Imatra Oy Ab, Terästehtaantie 1, FI-55100, Imatra,
Finland.
(Received on January 13, 2014; accepted on June 20, 2014)
Magnetohydrodynamic flow phenomena with electromagnetic stirring
were studied in billet casting. Solidification microstructure and
oscillation marks were also investigated. EMS with 310 A current
was proven to increase central equiaxed zone from 10–15% in
unstirred billet to over 45% in stirred billet for steel grade
40CrMo4. Dendritic microstructures at the billet corners were found
to deflect downwards due to the sustained upward flow along the
mould corners. Rhomboidity was observed to relate to the unsteady
flow in the mould during changes of casting speed and EMS
intensities. Computational model- ing was performed and validated
with the results obtained from the casting experiments. Through
model- ing, a declining phenomenon of the injected stream from the
SEN was observed towards the back wall under certain stirring
intensities. This would influence thermal distribution of the
strand shell and casting qualities, thus requiring correct matching
of the vertical shear flow field with the horizontal rotation flow
in order to obtain a favorable flow field. In addition, vortexes
were found on the free surface around the SEN tube, which were
influential to the cleanliness of steel melt. Modeling was also
performed for a bloom caster with various SEN designs in the
context of cleanliness. It was found that ported SENs showed
obvious advantage on inclusion removal over the straight bore SEN.
Reducing casting speed is actually an effective way to improve
cleanliness. Casting trials with 65 bloom casting heats verified
the modeling results and remarkable improvement in cleanliness was
observed by using a 2-port SEN.
KEY WORDS: electromagnetic stirring; solidification microstructure;
fluid flow; oscillation marks; inclu- sions; steel cleanliness;
magnetohydrodynamics; computational fluid dynamics.
1. Introduction During the 1970’s to 1980’s, there came a common
under-
standing that increased solidification rate would reduce seg-
regation and improve homogeneity of microstructures. Driven by the
rapid expansion of market need and elevation of the downstream
automation level, casting speed, i.e. productiv- ity, had been
universally increased on the continuous casting machines
afterwards. Technically, the residence time of steel melt through
the casting mould was greatly reduced. This brought new challenges
for process control, defect preven- tion, and quality assurance in
the continuous casting tech- nologies. Fluid control techniques
have been widely used to implement the target, including
magnetohydrodynamic method, geometric method and thermophysical
method, etc., assisted with computational fluid dynamic
method.
Modern billet and bloom casting has ever stringent demands for
product quality, meanwhile maintaining high productivity as well as
low production cost. This requires better understanding and control
of the casting process, including fluid flow phenomena,
solidification microstruc- tures, as well as various defect
formation mechanisms. Especially, inclusion control has become a
top important issue in the steel production worldwide, which is
deeply involved in almost every aspect of steelmaking and
casting
processes. Great effort sustained for over half a century has been
put into cleanliness control in the various process stages from
ladle to tundish till the casting mould and solidifying strand, and
formed a comprehensive concept and technology called “clean steel”
in the 1980’s.1–3) Even though, inclusions, including
micro-inclusions (<25 μm) and macro-inclusions (>25 μm),
originated from the upstream steelmaking and de- oxygen processes
will still be carried over into the casting stage and finally
remained in the solidified microstructure.4)
The remaining inclusions tend to exist interdendritically and
intergranularly and may result in hot tearing and cracks during the
solidification process. Also, internal and surface cracks may form
in the downstream deforming and thermomechani- cal processes,
finally deteriorating the mechanical properties, especially fatigue
performances, of the component.5)
In addition to cleanliness control measures in the ladle and
tundish, casting stage is the last opportunity to remove inclusions
to the top slag layer which covers the steel melt in the mould.
When casting engineering steel grades, a sub- merged entry nozzle
(SEN) is usually applied to guide the steel melt from the tundish
into the casting mould. Except for deoxidation products remaining
in the steel melt there are other exogenous inclusions, typically
reoxidation prod- ucts, which can be very harmful and therefore
should be removed from the melt and thus prevented from entering
into the solidifying strand. Since the steel melt is the carrier of
these inclusions, thereby, in order to implement inclusion control,
fluid flow control in the mould is more significant.
* Corresponding author: E-mail:
[email protected] DOI:
http://dx.doi.org/10.2355/isijinternational.54.2273
© 2014 ISIJ 2274
ISIJ International, Vol. 54 (2014), No. 10
Nowadays, there are two approaches which are mostly used to
implement fluid flow control. One is to impose an external force on
the flowing fluid through magnetohydrodynamic techniques, e.g.
electromagnetic stirring (EMS); another is to constrain
geometrically the fluid flow in the mould via improved design and
arrangement of mould, SEN and strand guiding segment to attain
demanded cleanliness as well as favorable solidified
microstructures.
In slab casting, a two-port design on the SEN end is the normal
construction because of the flat geometry of the slab mould. In
bloom and billet casting, straight bore metering SEN is normally
used. A typical drawback of the straight bore SEN design is that
melt stream penetrates deep into the liquid pool within the strand.
Except for the thermal impact to the lower strand shell, the
inclusions dispersed with the stream also have difficulties in
floating up to the top slag to be removed.6,7) Especially, with
high casting speed, this problem becomes more serious.8)
Many studies have been carried out to investigate swirl- ing SEN
designs through various approaches. Sormann et al.7) developed a
precision control valve (PCV) at the tundish exit, combined with a
swirl SEN. The swirling flow was generated with an eccentric
throttle slot in the piston of the PCV. The stream penetration
depth was remarkably reduced and the meniscus wave diminished even
at higher casting speed. Meanwhile, using rotational
electromagnetic field to generate a swirling flow in the SEN was
suggested. Yokoya and Kholmatov et al.9–11) studied a swirling SEN
with various divergent angles at the SEN end for square and round
billets, where the swirling flow was created by swirl blades
mounted at the upper end of the tube. The swirling flow enhanced
dissipation of the melt superheat in the mould and remarkably
reduced stream penetration depth so that the inclusions were
favored for floatation. The present authors12) studied the effect
of a rotational electromagnetic field around the SEN tube (SEN-EMS)
on the inclusion removal for bloom casting by computational
modeling. The SEN-EMS clearly increased the removal rate of
inclusions for various inclusion sizes, due to reduced stream
penetra- tion and lateral dissipation flow in the mould. However,
considering the operational conveniences and cost, these approaches
have not been widely used in the practice.
Bloom is different from billet by leaving much larger space in the
mould for more complicated SEN design and thus for better control
of the flow field and cleanliness. Pin- dor and Michalek13) studied
multi-port designs with 4 and 5 outlets, via mathematical and water
modeling as well as casting trials. Finally they came to an
“umbrella design” with a spherical cap to guide the upward 4 ports.
The main idea is to distribute the melt stream sideways and upwards
to the lateral mould walls in order to enhance the removal of
inclusions. Their study indicated that immersion depth of the SEN
was an important casting factor. The immersion depth between
200–240 mm gave the best results. The cast- ing trials showed that
the semis quality for carbon content less than 0.3 wt% was greatly
improved, and product rejec- tion rate was reduced from 1.39% to
zero compared with the cast product using straight bore metering
SEN.
In this paper, the two fluid flow control techniques, i.e. EMS and
SEN design were investigated experimentally and numerically in
billet and bloom casting. The influence of the fluid flow on
initial solidification microstructure was stud- ied by casting
trials in a steel plant. The effect of EMS induced rotational flow
on the meniscus shape and oscilla- tion marks was also studied. SEN
designs including 2-port designs with various guiding angles, a
4-port and a straight metering SEN were simulated and their effect
on the inclu- sion removal was compared by using computational
fluid dynamics modeling. In-mould electromagnetic stirring was
simulated to evaluate the influence of EMS on the fluid flow
and inclusion removal. The industrial casting trials with a 2- port
SEN were performed and compared with the results by the metering
SEN.
2. In-plant Casting Experiments about the Effect of EMS on Fluid
Flow, Solidification Microstructure and Meniscus Shape
2.1. In-mould EMS Setups and Measurement of Mag- netic Field
Experimental work for characterizing the effect of in- mould EMS on
the liquid flow was carried out at Gerdau Special Steels Europe
Basauri plant. Figure 1 shows a sketch of the stirrer situated at
the end of the mould cassette and measurement of the magnetic flux
density along the mould axis for the 185 mm billet. It is seen that
the maxi- mum values of the magnetic field are situated at the
stirrer centre, around 734 mm apart from the mould top. Near the
meniscus, 150 mm distance from the mould top, the mag- netic field
value was 5% of the maximum value at the centre of the mould.
2.2. Fluid Flow and Solidification Microstructure The liquid flow
in the mould was evaluated based on the
deflection of the primary dendritic arms in the microstruc- ture.
Even, comparison with other techniques used to mea- sure liquid
flow on the meniscus during casting was made. It is known that
during solidification process in the mould, the primary dendrites
will grow in a deflected direction opposite to the melt flows.
Takahashi et al.14) developed the following mathematical expression
relating the degree of the dendritic deflection with the fluid
velocity of the steel melt in the solidification front which is
correspondent to the intensity of the local magnetic field:
......... (1) where θ is the deflection angle in degrees; U the
fluid veloc- ity in cm·s–1; and V the solidification front speed in
cm·s–1.
Industrial trials to assess the effect of mould EMS on the
solidification structure and steel cleanliness were also car- ried
out. A heat of steel grade 40CrMo4 was cast with 3 dif- ferent EMS
settings of 0, 150, and 310 A electric current. Figure 2 shows the
solidification structure and geometric quality of the billet with
the defined casting parameters under the different EMS intensities.
The EMS was switched off after 5 minutes of casting for 35 minutes
then switched on and the electric current was raised up to 310 A.
After 57 minutes of casting it was decreased to 150 A of electric
cur-
Fig. 1. Sketch of the mould stirrer situated at the lower part of
the mould and variation of the magnetic flux density along the
billet caster mould. Measurements were carried out at the Gerdau
Special Steels Europe, Basauri plant for 185 mm square
billets.
θ = ×− −22 49 3 72 100 177 3 2 08. log( . / ). .U U V
ISIJ International, Vol. 54 (2014), No. 10
2275 © 2014 ISIJ
rent. The melt temperature and casting speed remained con- stant
during the testing period of time.
The squared marked line in Fig. 2(a) represents the changes of
rhomboidity measured from the transversal sam- ples of the cast
billet. Four of the eight samples showed sig- nificant
rhomboidities. The first two bigger rhomboidity values could be
related to the increase of casting speed at the beginning of the
test and the latter two high values might correspond to the changes
in the mould EMS intensity dur- ing casting. It can be concluded
that changes of flow field in the mould, i.e. the stirring
intensity and casting speed, enhance rhomboidity, whereas casting
under stabilized flow field produces better geometric quality of
the cast billet. This finding agrees principally with Madias15)
that rhom- boidity is generally attributed to non-uniform cooling
during the initial shell formation in the mould.
The percentage area occupied by the equiaxed structure was measured
from the transversal samples and is also pre- sented in Fig. 2(a).
It is clearly seen that by increasing the mould EMS intensity, the
proportion of central equiaxed zone remarkably increased. The
equiaxed crystal ratio (ECR) increased from 10–15% without stirring
to over 45% with 310 A stirring intensity, and then down to 30–35%
with 150 A stirring intensity.
2.3. Near-meniscus Flow and Oscillation Marks The standard
deviation calculated for 1 minute time peri-
od of the meniscus level, measured by the radioactive con- trol
system, can be seen in Fig. 2(b). It is noteworthy that no change
was observed for the mould level stability by
changing the mould EMS. This result suggested that if the mould
stirrer was mounted far below the meniscus (the upper edge of
stirrer coil was 470 mm from the meniscus), it had no significant
influence on the meniscus level. How- ever, this result seems
opposite to the effect of the EMS on the deflection of dendrites
just below the billet surface as shown in Fig. 3, where the
microstructure near the surface for a sample was produced with 310
A EMS. It can be observed that the deflection of dendrites started
from almost the billet surface. Using the Takahashi et al.
expression, EMS induced flow velocity of 0.2 m/s can be deduced
when the dendrite deflected 21°. Some discontinuity in the den-
drite growth is observed at 9 mm from the surface possibly because
the solid shell reached the zone of the maximum magnetic field.
These observations indicate that there was a rotational flow of the
liquid steel near the meniscus agitated by the stirrer, but this
rotational flow didn’t bring about sen- sible disturbance to
stability of the mould level. In order to clarify this apparent
contradiction, some more metallo- graphic studies and modeling were
also carried out.
Oscillation marks are, in general, regarded as regularly spaced,
transversal indentation defects and overlapping marks formed at the
initial solidification stage of the shell wafers on the surface of
continuously cast products due to mould oscillations and fluid
instabilities in the liquid strand pool.16) In order to study the
influence of EMS on the menis- cus solidification, i.e. oscillation
marks, longitudinal slices with 15 mm thickness were cut from all
the four faces of a 250 mm billet length sample. Figure 4 shows the
photo- graph of all the four slices (marked 1–4). The off corner
regions against the EMS induced liquid flow (flow hitting the wall)
are marked with “X”. Figure 5 presents the oscil- lation marks
morphology by hot acid etching on the billet surface. Typical
surface oscillation marks shown in Fig. 5(a) (for 40CrMo4 steel
cast with 310 A EMS) indicate that the oscillation marks arose
around 8–10 mm towards the billet corner, in the area which was
against the liquid flow. Similar results were observed for all the
other faces. Samples taken without mould EMS did not show such a
rise in the oscilla- tion marks at the corners. To further verify
this phenome- non, longitudinal billet surface samples were also
prepared from another heat. Figure 5(b) shows the oscillation marks
on one surface of the billet produced with new composition (steel
C10E with 0.1%C cast with 270 A MEMS). It can be seen that about 6
mm rise of the oscillation marks has occurred at the corner side
against the liquid flow and sim- ilar rise for all the other faces
as well.
2.4. Vertical Upward Flow and Downward Deflection of Primary
Dendrites at the Corners
A metallographic analysis of the two end longitudinal
Fig. 2. Influence of the EMS intensities (0, 150 and 310 A) during
casting a heat of grade 40CrMo4 on casting parameters and billet
metallographic characteristics: (a) Measured central equiaxed zone
ratio and rhomboidity; (b) Meniscus level deviation (Gerdau
R&D).
Fig. 3. A typical microstructure near the surface in which
dendrites are seen tilted. This indicates that there is a
rotational flow of the liquid steel near the meniscus agitated by
the stirrer (Gerdau R&D).
© 2014 ISIJ 2276
ISIJ International, Vol. 54 (2014), No. 10
surfaces of billet face 1, in Fig. 4, showed an interesting result:
dendrites were also deflected in one of the sample ends, and the
deflecting direction indicated an upward fluid flow towards the
meniscus at the corner side against the rotational liquid flow. The
deflection angle was measured at about 18° which corresponds to a
vigorous liquid velocity of around 0.14 m/s in this region
calculated by Eq. (1). In order to investigate if the upward liquid
flow exists all along the entire perimeter, one of the billet
surface samples was cut in 20 mm wide slices, each of which was hot
acid etched to reveal the primary dendrite morphology. Figure 6(a)
shows the positions of the billet face (arrowed) where
upward flow was observed and the corresponding liquid flow velocity
calculated from dendrite tilting measurements with Eq. (1) are
displayed in Fig. 7(a). It seems that there was an upward liquid
flow only at the corner sides which were against the rotational
flow and this upward flow at the corners drove the oscillation
marks at the meniscus area to rise and formed a waved configuration
of the oscillation marks. This is diagrammatically demonstrated in
Fig. 6(b).
In addition to the studies above on the EMS induced flow in the
billet mould, casting trials were also carried out on a bloom
caster at Ovako Imatra plant to study the effect of SEN designs on
steel cleanliness, which is described in a lat- ter section.
3. Computational Modeling 3.1. Mould Setups of the Billet and Bloom
Casters
The setups of the billet mould at Gerdau R&D and the bloom
mould at Ovako are listed in Table 1, where the billet section is
185×185 mm2 with an arc radius of 9 m and the bloom section is of
the size 371×311 mm2 with an arc radius of 15 m. EMS stirring
center is positioned 734 mm below the mould top for billet and 500
mm for the bloom. Figure 8 illustrates the different SEN designs
for the bloom caster and the geometric details can been seen in
Table 2, where (a) is a straight bore type; (b)–(d) are two-port
types with various port geometries and guiding angles; and (e) is
the four port type. The inner and outer diameters of the SENs are
ø55 mm and ø108 mm respectively. For the ported SENs, (b) and (c)
are of rectangular port with sizes of 62×42 mm2 and 50×48 mm2
respectively; (d) is of round port with a diameter of ø55 mm, which
is the same as the inner diameter of the SEN tube; (e) is a
combination of round and rectangular with an outer size of ø38×55
mm2. For the guiding angle of the port, (b) and (c) are 30° and
15°
Fig. 4. Longitudinal surface slices for metallographic analysis to
study the influence of mould EMS on billet surface quality and
oscillation marks formation. “X” indicates the corner side against
the liquid flow (Gerdau R&D).
Fig. 5. Influence of EMS on the rising of oscillation marks at the
corner side against the EMS induced rotational liquid flow, with
view of the billet surface after hot acid etching. (a) Steel grade
40CrMo4, EMS current 310 A; (b) Steel grade C10E, EMS current 270 A
(Gerdau R&D).
Fig. 6. (a) Observation and estimation of the longitudinal fluid
flow based upon deflecting of the primary dendrite mor- phology in
one of the billet faces of Fig. 4 billet surface samples. (b) A
sketch of the relationship between EMS induced liquid rotation,
liquid upwards flow and elevation of the oscillation marks (Gerdau
R&D).
ISIJ International, Vol. 54 (2014), No. 10
2277 © 2014 ISIJ
downward respectively; (d) and (e) are 15° upward. For the SEN
immersion depth, (a)–(c) are 150 mm below the menis- cus; (d) and
(e) are 180 mm below the meniscus.
3.2. Fluid Flow Models The steel melt flow in the mould was
computed by apply-
ing the ANSYS-FLUENT CFD software. The turbulence of the flow was
treated with the realizable k-ε turbulence mod- el. Heat transfer
was not considered in this simulation. The
boundary conditions were defined corresponding to the cast- ing
speed of 0.6 m/min. The physical properties were sup- posed to be
constant: the density of molten steel was between 7 000–7 200 kgm–3
depending on the steel grade and the density of slag 3 500 kgm–3;
the viscosity of steel melt and slag was chosen 0.0063 and 0.065
Pa·s respectively.
The momentum balance equations are as follows:
.......................................... (2) where μ = μ0 + μt.
μ0, μt, and μ are the molecular dynamic viscosity, turbulent
viscosity, and effective viscosity (Pa·s). ρ is the density of
steel melt (kgm–3). ui, uj are fluid veloc- ities in the ith and
jth directions respectively (ms–1). gi is gravitational
acceleration in the ith direction (ms–2). p is the pressure in the
fluid (Pa). t is time (s). xi, xj are the spatial coordinates in
the ith and jth directions (m). i, j denote the three directions in
the global Cartesian coordinate system. F is the external forces
acting on the fluid except for gravita- tion. The Lorentz force
resulting from EMS is added through this item F.
Equation of continuity is:
.................................. (3)
The realizable k - ε turbulence model is used to treat the tur-
bulence characteristics of the fluid flow, which is shown
below:
.......................................... (4)
........ (5)
Fig. 7. Longitudinal upward liquid steel velocity in the billet
face shown at Fig. 6(a). The fluid flow velocity has been calcu-
lated using the Takahashi et al.14) equation and the deflec- tion
measurements of the primary dendrites at different surfaces of
billet slides (Gerdau R&D) (a) and using CFD modeling
(b).
Table 1. Mould-SEN-EMS setups of the billet and bloom.
Billet Bloom
Mould length, m 1.0 0.7
Strand bending arc radius, m 9.0 15
SEN diameter, mm Ø36–46(Ø73–76) Ø55(Ø108)
SEN immersion depth, mm 110 150–180
Casting speed, m/min 1.25 0.6
EMS current, A 0, 150, 310 0, 150, 300
EMS magnetic flux, Gauss 0, 420, 870 (rms) 0, 870 (rms)
EMS frequency, Hz 3.0 Hz 2.0 Hz
EMS stirring position, mm –734 –500
Fig. 8. SEN types (a)–(e) for the bloom caster (Ovako
Imatra).
Table 2. Geometric details of the SEN designs for the bloom caster
used in the modeling.
(a) (b) (c) (d) (e)
Number of ports 0 2 2 2 4
Tube diameters, mm
Port size, mm – 62×42 50×48 ø55 ø38×55
Guiding angle, ° –90 –30 –15 +15 +15
SEN immersion depth, mm 150 150 150 180 180
ρ ∂ ∂
ρ ∂ ∂
where , , .
In these equations, Gk represents the generation of turbu- lence
kinetic energy due to the mean velocity gradients. Gb is the
generation of turbulence kinetic energy due to buoy- ancy. C2 and
C1ε are constants. σk and σε are the turbulent Prandtl numbers for
the turbulent kinetic energy k and the dissipation rate of
turbulent kinetic energy ε, respectively. Sk and Sε are
user-defined source terms.
This turbulence model differs from the standard k - ε model in the
following two aspects: 1) the realizable k - ε model contains a new
formulation for the turbulent viscos- ity; 2) a new transport
equation for the dissipation rate has been derived from an exact
equation for the transport of the mean-square vorticity
fluctuation. The term “realizable” means that the model satisfies
certain mathematical con- straints on the Reynolds stresses,
consistent with the physics of turbulent flows. The benefit of the
realizable k - ε model is to predict accurately the spreading rate
of both planar and round jets. It provides superior performance for
flows involving rotation, boundary layers under strong adverse
pressure gradients, separation and recirculation. This model has
been extensively validated for a wide range of flows,17)
including rotating homogeneous shear flows, free flows including
jets and mixing layers, channel and boundary lay- er flows, and
separated flows. For all these cases, the per- formance of the
model has been found to be substantially better than that of the
standard k - ε model. Especially, the realizable k - ε model
resolves the round-jet anomaly, i.e., it predicts the spreading
rate for axis-symmetric jets as well as that for planar jets. More
mathematical details of this model can be referenced in the
ANSYS-FLUENT manuals. Thereby, the realizable k -ε model is
considered to be suit- able for the prediction of rotational flow
driven by electro- magnetic field. Still, the standard wall
function model is used to treat the turbulent boundary layer. The
convergence conditions for the flow variables are set to
10–4–10–6.
3.3. Lorentz Force Model The complexity in this simulation is the
EMS driven flow
phenomenon. As is known, the rotational electromagnetic field
generated by the EMS coils induces an electric current in the
conductive steel melt. The interaction of the electric current with
the magnetic field produces a Lorentz force act- ing on the fluid
which carries the current. The Lorentz force strives to brake the
relative movement between the fluid and the magnetic field. For the
rotational EMS field, the Lorentz force drives the fluid to flow
following the rotational direc- tion of the electromagnetic field.
The Lorentz force can be calculated by first solving Maxwell’s
equations and then applying Ohm’s law as is done by the previous
works.18–22)
In this paper, instead of solving the complicated Maxwell’s
equations, a semi-empirical equation is proposed to calcu- late the
Lorentz force in time-averaged scheme:
.............. (6)
.............. (7)
....................... (8)
................ (9)
where , , . In these
equations, Fx, Fy, Fz are the Lorentz force in the three direc-
tions, Nm–3; Ux, Uy, Uz are fluid flow velocity, ms–1; σ is
electrical conductivity, 714 000 S/m. fm is a distribution function
of the measured magnetic field along the mould center; B0 is the
flux density of the magnetic field at the stir- ring center based
on in-house measurement as shown in Figs. 1 and 9, T; f is the
stirring frequency, Hz; μ0 is mag- netic permeability,
1.256637614×10–6 Hm–1; Ut is tangential velocity, ms–1; x, y, z are
coordinate points in the calculation domain and (0,0,z) is the
central axis of the rotational elec- tromagnetic field, m. a and b
are the half sizes of the bloom/ billet, m; c0 and c1 are
coefficients, c0, c1 < 1.
In addition, Joule heating Q (W/m3) is also included with the
following proposed model:
... (10)
where c2 is coefficient. This method can save large amount of
computation time and effort being used on the grid oper- ation
between electromagnetic field and fluid flow field. Thus, the
computation efficiency can be much improved for the complicated
magneto-hydrodynamic phenomenon in the casting process, meanwhile
representing major rotational flow features under the action of
EMS.
Since the stirred flow usually results in severe surface
deformation due to the upward stream along the mould cor- ners, the
free surface phenomenon at the steel melt/slag lay- er is also
simulated by the volume of fluid (VOF) method. The predicted
surface wave can be compared with the oscil- lation marks left on
the bloom/billet surface to validate the models and methods being
used in the simulation.
3.4. Inclusions Tracking After the flow field is computed, particle
trajectories are
simulated to capture the movement of inclusions inside the steel
melt due to the difference of densities from the steel melt and the
difference of inclusion sizes. The inclusions in the melt can float
upwards being trapped by the liquid slag, or flow downwards with
the fluid into the deeper strand pool being merged in the
solidified structure. To simplify the computation, the reflection
boundary condition is used on the strand shell. This is to say that
when an inclusion touch- es the solidified strand shell, it is
bounced back into the melt. Only two destinations are considered in
the calcula- tion, being removed by the slag layer or flowing out
to the deeper pool and included into the solidified shell. In order
to calculate the transient movement of inclusions in the steel
flow, the Euler-Lagrange approach was used and the equa- tion is as
below:
C1 0 43 5
F c f B U fyx m x= − − 1
2 21 0
2σ α π( ) ( )
2 21 0
2σ α π( ) ( )
2 0 2σ α( )
ab = 2
π Fig. 9. Measured Lorentz force distribution in the bloom
mould
(Ovako Imatra).
Q c f B U fy U fx Um x y z= − + + + 1
2 2 22 0
2279 © 2014 ISIJ
............... (11)
Here, Up is the moving velocity of a particle in the melt (ms–1);
ρp is density of the particle (kgm–3). The left hand of the
equation is the acceleration term of the particle to be calculated.
The first term on the right hand is the drag force. The second term
is the buoyancy term. The third term is the virtual mass force,
which represents an additional resistance due to the attached,
“virtual” fluid mass around the particle in the process of
acceleration movement. The fourth term
is the action force of a shear flow field on the
particle, which is resulted from a gradient of the fluid veloc-
ities around the particle and the direction of which is oppo- site
to that of the velocity gradient. In a rotational flow field, this
force supplies a pushing force pointing to the rotation center to
drive the particle to move with the fluid rotation- ally. In this
context, a centripetal force is not needed to impose on the
particle, even though it rotates in the fluid, since the fourth
term has already played this role. Turbu- lence treatment on the
interaction of the particle with turbu- lent eddies in the fluid
can be referenced in Trindade et al.23)
Due to the random nature in the trajectory calculations resulting
from the turbulence treatment, one trajectory can- not be
reproduced by another even with all the same com- putation
parameters. However, by injecting a large number of particles
through the SEN into the mould, statistic results can give a clear
trend to show the percentage of the inclu- sions which are trapped
by the slag layer. The particle diam- eter ranges from 1 to 200
microns so that the effect of flow field on almost all sizes of
inclusions can be demonstrated. Thereafter, the influence of the
different SEN designs on inclusions can be evaluated.
4. Modeling Results
4.1. Flow Field and Validation with a Billet Casting The rotational
flow field is simulated for the billet casting
with three EMS settings of 0 A (no stirring), 150 A, and 310 A
electric current, as shown in Fig. 10. When stirring is not applied
(Fig. 10(a)), the liquid stream straightly pen- etrates deep into
the strand pool. At 150 A stirring intensity (Fig. 10(b)), the
rotation flow of the steel melt is observed, the maximum velocity
of which is around 0.35 m/s in the near wall region of the stirring
center. Using again Takahashi et al. expression (Eq. (1)), the
corresponding dendrite deflecting for this calculated liquid flow
would be 25°, which is little higher than the measured values. The
reason might be that the maximum tangential velocity exists only
for a short while at the solidification front with the contin- uous
downward movement of the strand shell.
An interesting phenomenon in Fig. 10(b) is that the incoming stream
is declined towards the back wall of the strand shell under the
interaction of the horizontal shear flow field in the rotational
flow with the vertical shear flow field of the injecting stream.
Simultaneously, penetration depth is decreased due to the
dissipating effect of the rota- tional flows on the incoming
stream. The declined injecting stream may result in non-uniform
thermal distribution on the strand shell facing the stream, and if
more seriously, may lead to vertical central cracks and even
break-out.
When the stirring intensity is increased to 310 A, the incoming
stream is straightened and shortened under the action of the
strengthened shear flow field of the horizontal
rotation, see Fig. 10(c). The maximum tangential velocity is around
0.8 m/s in the stirring central zone. It can be seen that correct
matching of the horizontal rotation flow with the vertical
injection flow in the mould is significant for casting qualities,
which is related to casting speed, geometrical design and stirring
parameters.
To validate the flow field especially the upward corner flows,
vertical components of the flow field are presented as in Fig. 11
for unstirred (a) and stirred (310 A) (b) cases. Upward corner
flows are observed for stirred case with the magnitude of 0.10–0.22
m/s along the corners above the stirring center, and in most of the
corner length the upward flow is between 0.15–0.20 m/s, which is
over predicted compared with the casting experiments evaluated by
den- drite deflections in the corner region where 0.14 m/s was
measured (see Section 2.4). A horizontal distribution of the
maximum vertical velocity above the stirring center was shown in
Fig. 7(b) for comparison with the measured results. Naturally, the
modeling results above the stirring center are higher than the
measured results on the average meaning. Generally, the modeling
results agree with the experiments in the flow pattern and trend.
It is noteworthy that below the stirring center, corner flows are
converted to
dU
d
∂ ∂
Fig. 10. Simulated flow field in the billet mould with different
EMS intensities (0, 150, 310 A).
Fig. 11. Vertical component of the fluid flow velocities on hori-
zontal sections of 40, 300, 584 (stirring center), and 1 000 mm
below meniscus. Red represents upward flow; blue represents
downward flow. (a) Unstirred; (b) Stirred with 310 A.
© 2014 ISIJ 2280
ISIJ International, Vol. 54 (2014), No. 10
downward directions and the central flow converted to upward, just
opposite to the volumetric flow pattern above the stirring center.
Besides, on the stirring central plane, the vertical velocity
component is relatively uniform (Fig. 11(b)), demonstrating a plug
flow feature to the downward direction. However, considering the
tangential components, as can be seen in Fig. 10(c), majored by a
horizontal rotation flow, the plug flow on the stirring central
plane is actually a rotational plug flow toward the downward
direction.
Resulting from the upward flows at the mould corners, the raised
free surface waves were also predicted in the simulation as can be
seen in Fig. 12. The wave height was 10 mm at the corners above the
average meniscus level. This is in agreement with the measured
oscillation marks as shown in Fig. 5(a). Because of the
simplification on the model assumptions and limitation of VOF
method, the dis- continuity phenomenon of the oscillation marks at
the cor- ner cannot be exactly represented by the present modeling.
However, the asymmetry of the surface wave at the corners can be
clearly predicted in the contour map as shown in Fig. 12.
Considering initial solidification, this discontinuity can be
explained that the impinging momentum pushed the thin shell wafer
to a closer contact with the counterpart corner wall and enhances
the initial solidification on this side of the corner, so as to
form a discontinued, or say, uneven wafer shell on the connected
two sides of the cor- ners.
Another interesting phenomenon from the modeling results (Fig. 12)
is that four vortexes appeared on the free surface around the SEN
tube, geometrically corresponding to the four corners or four side
walls. The reason might be owing to the negative pressure caused by
the non-uniform tangential circulation flows around the shroud wall
affected by the square or rectangular geometric feature of the
mould. Another reason, which also contributes to deepen these vor-
texes, is that the “pulling” effect of the injection stream causes
pressure drop to the free surface above. These vor- texes may
re-entrain the slag droplets or trapped inclusions in the slag
layer back into the steel melt and deteriorate cleanliness. By
reducing stirring intensity and deepening immersion depth, these
vortexes can be relieved.
4.2. Effect of Different SEN Designs on the Free Menis- cus for
Bloom Casting
Figure 13 demonstrates the free meniscus influenced by the
different SEN designs in the bloom casting process. The red color
at the mould corners represents the raised wave above the average
meniscus level, and the blue color around
the tube represents the vortexes below the average meniscus level.
The meniscus wave at the corners is mainly driven by upward corner
flows caused by the rotational flow field as illustrated in the
billet simulation (Fig. 11(b)). From Fig. 13, it is seen that the
influence of different SENs on the free sur- face wave is little on
the general free meniscus configura- tion.
4.3. Effect of Different SEN Designs on Inclusion Removal
Inclusion tracking is performed for the bloom casting with various
SEN designs. By tracking the trajectories of a large number of
particles, herein 10 000 in the calculation, statistic results of
inclusion removal rate are obtained, as shown in Fig. 14. The
curves in Fig. 14 indicate that ported SENs give better removal
rate than the straight bore meter- ing SEN. Especially, the 2-port
SEN with guiding angle of upward 15° shows the best result. The
4-port SEN does not give the best result as expected. Generally
speaking, it is clear from the simulation results that ported SENs
show obvious advantage in cleanliness over the metering SEN and the
4-ported SEN does not show superior to the 2-port SENs.
4.4. Effect of Casting Speed on Inclusion Removal Casting speed is
one of the main factors influencing the
removal rate of inclusions, since it directly determines the flow
field magnitude in the mould, and also the residence time of steel
melt through the mould. Figure 15 illustrates the influence of
casting speed on the inclusion removal, by using (a) the straight
bore SEN and (b) the 2-port SEN with
Fig. 12. Free surface wave in the billet casting with 310 A EMS.
The surface is raised up by 10 mm at the corners which is in good
agreement with the measured oscillation marks at the corners. Fig.
13. The free meniscus waves with various SEN designs.
ISIJ International, Vol. 54 (2014), No. 10
2281 © 2014 ISIJ
the guiding angle of upward 15°. When the casting speed was reduced
from 0.6 m/min to 0.355 m/min, the removal rate was increased
substantially. This is also to say that reducing casting speed is
an efficient way to increasing cleanliness if productivity
allows.
From another side, this example also indicated that increasing
casting speed brings about very stringent techni- cal demands for
cleanliness control owing to the reduced residence time of the
steel melt through the mould. With this understanding, it can be
deduced that larger product section
with lower casting speed is favorable for cleanliness, sup- posing
the productivity is maintained on the same level. This is
conflicting to the concept and practice of near net shape casting
developed and applied in the recent three decades.24) Another
option is the multi-strand caster arrangement with an appropriate
casting speed to compro- mise cleanliness, sizes and productivity.
Anyhow, metallur- gical engineering marches ahead this way,
depending on practical needs, technological capabilities and
economical motivations.
5. Casting Trials with Two-port SEN and Metering SEN on a Bloom
Caster
Based on the modeling results obtained for the bloom casting, plant
trials were carried out on a two-strand bloom caster with 75 t heat
size, 15 m radius, stopper rod control and M-EMS. The CFD modeling
showed the best cleanli- ness results for the 2-port SEN design
with guiding angle upward 15°. However, due to practical reasons,
the 2-port SEN design with the guiding angle downward 15° was cho-
sen for the plant trials.
In the trial campaign a straight bore SEN was used on one strand,
and the 2-port SEN with downward 15° guiding angle on the second
strand. Altogether 65 heats were cast in the trials with varying
steel grades: quenching and temper- ing steels, boron steels,
engineering steels, case hardening steels, micro-alloyed steels and
spring steels.
Sampling of the heats was carried out at the rolling mill from the
hot rolled bars. Samples were obtained from both strands at the
beginning and in the middle of the heat. Sam- ple length varied
between 210 to 500 mm depending on the bar diameter. Non-metallic
inclusion content was evaluated with immersion ultrasound method.
In the method the steel samples were machined to give them a 90×90
mm or less cross-section, again depending on the sample diameter. A
spherical ultrasonic transducer with a 20 mm diameter and a 10 MHz
frequency was used for scanning the sample per- pendicular to the
casting direction.
For each heat, the cleanliness results were compared between the
2-port SEN and the straight bore SEN. The comparison yielded the
result in Fig. 16. Of the 65 heats, 10 heats showed that 2-port SEN
influenced cleanliness nega- tively while 8 heats showed no
influence and 47 heats showed improvement in cleanliness.
Particularly, of the 47 heats with positive results, 39 casts
indicated over 60% reduction in the non-metallic inclusion amount.
This is a significant improvement in the cleanliness of the
product.
Fig. 14. Inclusion removal rate with various SEN designs.
Fig. 15. Casting speed substantially influences the inclusion
removal rate.
Fig. 16. Casting trials show the improvement of inclusion removal
with 2-port SEN compared with the straight bore SEN (Ovako).
© 2014 ISIJ 2282
ISIJ International, Vol. 54 (2014), No. 10
6. Summary Remarks Comprehensive billet casting trials were carried
out to
study the effect of magnetohydrodynamic phenomena induced by EMS on
the flow field and the solidification microstructures. It was found
that: 1) application of EMS did not cause sensible disturbance to
the meniscus stability; 2) EMS induced rotational flow resulted in
a rise of oscilla- tion marks at the mould corners due to the
upward flow streams along the mould corners; 3) the sustained
upward flow streams along the mould corners led to downward
deflected dendrite morphology at the billet corners; 4) there
appeared to be a discontinuity of the oscillation marks at the
intersecting place of the connected walls, which was formed by the
impinging effect on one side of the corner by the rota- tional
flow; 5) EMS clearly increased central equiaxed zone from 10–15% in
the non-stirring case to over 45% with the 310 A stirring
intensity; 6) rhomboidity was observed to relate to the unsteady
flow in the mould during changes of casting speed and EMS
intensity.
Using CFD method, EMS induced rotational flow phe- nomenon and near
meniscus phenomenon in a billet casting were simulated and
validated with casting trial experiments. Simulated corner flow
agreed well with the measured result evaluated from dendrite
deflections, and the free surface wave coincided with the measured
oscillation marks. From the modeling results, a declining
phenomenon of the inject- ed stream from the SEN was observed
towards the back wall under certain stirring intensities. This
would influence ther- mal distribution of the strand shell and
casting qualities, thus requiring correct matching of the vertical
shear flow field with the horizontal rotation flow in order to
obtain favorable flow field. In addition, vortexes were found on
the free sur- face around the SEN tube, which were influential to
the cleanliness of steel melt.
Through modeling the free meniscus and inclusion trajec- tories for
a bloom casting with various SEN designs, their influence on the
cleanliness was evaluated. It was found that ported SENs
demonstrated obvious advantage on inclusion removal over the
conventional straight bore SEN. The 4- port SEN did not give better
results than the 2-port SENs. Casting trials with 65 bloom casting
heats verified the mod- eling results and showed remarkable
improvement in clean- liness by using a 2-port SEN. Reducing
casting speed is also an effective way to improve cleanliness
because of the increased residence time of the steel melt through
the cast- ing mould.
In general, application of magnetohydrodynamic tech- niques greatly
changes the volumetric flow pattern in the mould and deeper strand
pool, and remarkably impacts the microstructural morphology,
segregation, soundness, clean- liness and even properties of the
cast products. Geometric constraint directly controls the fluid
boundary and injecting guidance in the upper mould and sensibly
influences surface quality, even subsurface quality, and
cleanliness. Computa- tional modeling has become an essential and
indispensable assisting technique in fluid control engineering and
designs. It supplies quantitative solutions,
macroscopic/microscopic descriptions, process representations and
optimizations for a complicated fluid flow system. In addition, it
can also reveal inaccessible and even unrevealed phenomena with
proper models as shown above. These experimental and modeling
results stress again the importance of mould flow patterns and
comprehensive fluid control techniques in the pursuit of ever
cleaner steels and better cast qualities.
Acknowledgment The authors appreciate EU MAGNETO-HYDRO
project
(RFCS-CT-2007-00012) for the financial support. The authors would
like to thank Dr. Shahid Riaz, Tata Steel (UK), for valuable
discussions and supplying numerous casting cases during the
project. The authors would also thank Gerdau R&D and Ovako
Imatra Oy Ab for supplying the casting trial data and permission
for publishing the results.
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<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>
/ESP
<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>
/FRA
<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>
/GRE
<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>
/HEB
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
/HRV (Za stvaranje Adobe PDF dokumenata pogodnih za pouzdani prikaz
i ispis poslovnih dokumenata koristite ove postavke. Stvoreni PDF
dokumenti mogu se otvoriti Acrobat i Adobe Reader 5.0 i kasnijim
verzijama.) /HUN
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/ITA (Utilizzare queste impostazioni per creare documenti Adobe PDF
adatti per visualizzare e stampare documenti aziendali in modo
affidabile. I documenti PDF creati possono essere aperti con
Acrobat e Adobe Reader 5.0 e versioni successive.) /KOR
<FEFFc7740020c124c815c7440020c0acc6a9d558c5ec0020be44c988b2c8c2a40020bb38c11cb97c0020c548c815c801c73cb85c0020bcf4ace00020c778c1c4d558b2940020b3700020ac00c7a50020c801d569d55c002000410064006f0062006500200050004400460020bb38c11cb97c0020c791c131d569b2c8b2e4002e0020c774b807ac8c0020c791c131b41c00200050004400460020bb38c11cb2940020004100630072006f0062006100740020bc0f002000410064006f00620065002000520065006100640065007200200035002e00300020c774c0c1c5d0c11c0020c5f40020c2180020c788c2b5b2c8b2e4002e>
/NLD (Gebruik deze instellingen om Adobe PDF-documenten te maken
waarmee zakelijke documenten betrouwbaar kunnen worden weergegeven
en afgedrukt. De gemaakte PDF-documenten kunnen worden geopend met
Acrobat en Adobe Reader 5.0 en hoger.) /NOR
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/POL
<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>
/PTB
<FEFF005500740069006c0069007a006500200065007300730061007300200063006f006e00660069006700750072006100e700f50065007300200064006500200066006f0072006d00610020006100200063007200690061007200200064006f00630075006d0065006e0074006f0073002000410064006f00620065002000500044004600200061006400650071007500610064006f00730020007000610072006100200061002000760069007300750061006c0069007a006100e700e3006f002000650020006100200069006d0070007200650073007300e3006f00200063006f006e0066006900e1007600650069007300200064006500200064006f00630075006d0065006e0074006f007300200063006f006d0065007200630069006100690073002e0020004f007300200064006f00630075006d0065006e0074006f00730020005000440046002000630072006900610064006f007300200070006f00640065006d0020007300650072002000610062006500720074006f007300200063006f006d0020006f0020004100630072006f006200610074002000650020006f002000410064006f00620065002000520065006100640065007200200035002e0030002000650020007600650072007300f50065007300200070006f00730074006500720069006f007200650073002e>
/RUM
<FEFF005500740069006c0069007a00610163006900200061006300650073007400650020007300650074010300720069002000700065006e007400720075002000610020006300720065006100200064006f00630075006d0065006e00740065002000410064006f006200650020005000440046002000610064006500630076006100740065002000700065006e007400720075002000760069007a00750061006c0069007a00610072006500610020015f006900200074006900700103007200690072006500610020006c0061002000630061006c006900740061007400650020007300750070006500720069006f0061007201030020006100200064006f00630075006d0065006e00740065006c006f007200200064006500200061006600610063006500720069002e002000200044006f00630075006d0065006e00740065006c00650020005000440046002000630072006500610074006500200070006f00740020006600690020006400650073006300680069007300650020006300750020004100630072006f006200610074002c002000410064006f00620065002000520065006100640065007200200035002e00300020015f00690020007600650072007300690075006e0069006c006500200075006c0074006500720069006f006100720065002e>
/RUS
<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>
/SLV
<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>
/SUO
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/SVE
<FEFF0041006e007600e4006e00640020006400650020006800e4007200200069006e0073007400e4006c006c006e0069006e006700610072006e00610020006f006d002000640075002000760069006c006c00200073006b006100700061002000410064006f006200650020005000440046002d0064006f006b0075006d0065006e007400200073006f006d00200070006100730073006100720020006600f60072002000740069006c006c006600f60072006c00690074006c006900670020007600690073006e0069006e00670020006f006300680020007500740073006b007200690066007400650072002000610076002000610066006600e4007200730064006f006b0075006d0065006e0074002e002000200053006b006100700061006400650020005000440046002d0064006f006b0075006d0065006e00740020006b0061006e002000f600700070006e00610073002000690020004100630072006f0062006100740020006f00630068002000410064006f00620065002000520065006100640065007200200035002e00300020006f00630068002000730065006e006100720065002e>
/TUR
<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>
/ENU (Use these settings to create Adobe PDF documents suitable for
reliable viewing and printing of business documents. Created PDF
documents can be opened with Acrobat and Adobe Reader 5.0 and
later.) /JPN
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>> >> setdistillerparams << /HWResolution [1200
1200] /PageSize [596.130 795.120] >> setpagedevice