1. Lubricant Film Thickness Estimation
at the Mould Inlet Region of a Objectives
Continuous Casting Process
To develop a thermal Reynolds equation applied
to different surfaces velocities and temperatures
condition
Seminar Masyarakat Pemulas Indonesia (MASPI) To implement the Thermal Reynolds equation to
the inlet mould region of the continuous casting
Gedung BPPT Ruang Komisi 3 process
Jakarta, 27 Mei 2008
To estimate the mould inlet film thickness for
various parameters in continuous casting
Dr. Barman Tambunan
Pusat Teknologi Material (PTM) -
Badan Pengkajian dan Penerapan Teknologi (BPPT) Gedung BPPT II, Lt 22,
Jl. MH Thamrin No. 8
Jakarta 10340 barman@webmail.bppt.go.id
Research Question Introduction
• Practically all metals, which are not used in cast form are reduced to
How does the hydrodynamic lubrication in the some standard shapes for subsequent processing.
mould region of a continuous casting process • Manufacturing companies producing metals supply metals in form of
influence the casting product? ingots which are obtained by casting liquid metal into a square cross
section.
How can the thermal Reynolds equation be – Slab (500-1800 mm wide and 50-300 mm thick)
developed and implemented in the continuous – Billets (40 to 150 sq mm)
casting process?
– Blooms (150 to 400 sq mm)
What are the influences of the various casting • Sometimes continuous casting methods are also used to cast the
parameter to the lubrication in the continuous liquid metal into slabs, billets or blooms.
casting process? • These shapes are further processed through hot rolling, forging or
extrusion, to produce materials in standard form such as plates,
sheets, rods, tubes and structural sections.
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2. Sequence of operations for
obtaining different shapes Steel Making Plant
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STEEL MAKING PROCESS Continuous Casting Process
Area to be
analyzed
MELTING SECONDARY CASTING INSPECTION End
METALLURGY Product
• Charging ratio • Alloying (chemical comp.) • Temperature • Surface quality
• Chemical comp. • Desulfurisasi, deoksidasi, • Chemical comp. • Internal quality
• Temperature dehidrogenisasi, • Casting parameter by sulphur print/
• Tap to tap time decarburisasi macro-etch
• Inclusion shaped control • Shape/dimensio
• Temperature n
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3. Mould Flux Infiltration Continuous Casting Mold Flux
Performs Five Basic Functions :
• Thermally insulates the molten steel meniscus to
prevent premature solidification.
• Protects the molten steel in the mold from
reacting with atmospheric gases.
• Absorbs products of de/reoxidation from the
molten steel.
• Provides a lubricating film of molten slag to
prevent the steel from adhering to the mold wall
and to facilitate strand withdrawal.
• Modifies thermal heat removal in the mold.
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Thermal Heat Transfer Provides Liquid Lubrication in
in the Mold Gap Between Mold and
Solid Flux Film
Solidifying Shell
• The slag between the steel
shell significantly affects heat Liquid slag is drawn down Solid Liquid Steel
Heat Flux
transfer. into the gap along the Flux Slag Shell
Liquid
MOLD steel shell. The liquid is a
• The mold wall is very cold, WALL
Slag
and causes the slag to freeze lubricant, allowing the
into a solid. The solid greatly steel to be withdrawn Flux
reduces heat transfer. Solidifying without sticking to the Velocity
• The slag along the shell stays Shell mold wall. If the steel Mold
hot, and in liquid form. It sticks to the wall, it causes Wall
lubricates. a breakout.
Air Gap
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4. Mould Flux Infiltration Analysis
Temperature Distribution of the
Top of the Mould
Slab Mould
Meniscus Region
Center line
z
Lubricant
x Molten
Steel Pool
x0 h
ho
Ferrostatic
Pressure
T2
Film thickness
u2
Centre of the
Mould
±u1
T1
Solidified Steel
Strand
H : Non-
dimensional film
thickness H=
q ⎢
ln
⎡
x
⎤ ⎛ ⎞
⎥ − 2 q 2 − x 2 + q⎜1 + ln 2 − 1 ⎟ ( )
2 ⎢ 2 q2 − 2 q2 − x2 ⎥ ⎜ 2 ⎟
Temperature Distribution of the Transverse Slice at the Mould Exit ⎣ ⎦ ⎝ ⎠
equation in the 1
(time t = 39.4 sec) ⎛ 2γ ⎞ 2
meniscus region ⎜
q=⎜ ⎟
⎟
(Ref. Jimbo et al. (1991)) ⎝ (Δρ )g ⎠
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Thermal Reynolds Equation Thermal Reynolds Equation
∂P ∂τ ∂ ⎛ ∂u ⎞
p 'h 3 Non-dimensional Pressure
The Pressure R =
(Uh − Q )
= ⎜μ ⎟
12 μ
= s
Gradient
Gradient =
∂x ∂z ∂z ⎝ ∂z ⎠ Shear Stress F =
μ s α (Uh − Q )2
2
Non-dimensional Thermal
Backflow parameter
kh
The viscosity D = α (T2 − T1 )
Non-dimensional
⎧ ⎛ T2 − T1 ⎞⎫
μ = μs exp⎨−α ⎜T − ⎟⎬of
the mould Temperature difference
⎩ ⎝ 2 ⎠⎭
lubricant ∂ 2T μ s α (u 1 − u 2 )2
k = E S = Non-dimensional Velocity
∂z 2 k
h
2
Constant Energy Eα h 2 Non-dimensional Energy
Q= ∫ u dz The Flow Rate Dissipation
E *
=
k Dissipation
−h
2
μ α u
2 Non-dimensional Thermal
L = 0
Loading Parameter
k
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5. Applying Thermal Reynolds
Results and Discussion
3.5
Thermal Reynolds equation with the non- G=1 G=5
dimensional film thickness parameter H 3 G=2
G=3
G=4
G (H − 1)
2.5 G=4
G=5
dB Film
= Thicknes 2
R s Ho.L(1/6)
G=3
d x H0 A0 2 H 3 1.5 G=2
1
G=1
The thermal Reynolds equation with the 0.5
correction factor R was integrated numerically
using a Fourth order Runge-Kutta program 0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9
Thermal Loading L(1/6)
1 2 Film thickness variation for D = 2, S = 0 and
⎛ ⎞ 2 ⎛ ⎞
3 3
PFer PFer
G = γ P Fer A0 = xtot ⎜ various G
⎜ 12 μ U x 2 ⎟
H 0 = h0 ⎜ − γp
⎜ 12 μ U x 2 ⎟ B=e
2
⎟ ⎟
⎝ 0 tot ⎠ ⎝ 0 tot ⎠
The Continuous Casting Rig Modelling
•Mould cylinder 32.5 mm
•Outer diameter 74 mm Copper LVDT
•Length 400 mm Oscillating Plate Mould
Lubricant Reservoir
MLP-50 Load Cell
molten
bismuth
based
alloy
Withdrawal Motor
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6. Evaluation of Continuous Casting Lubricant
Lubricant Applied Produced Round Lubricant :
during Casting: • Castrol GTX2 oil Billet Shaped Cast Castrol GTX2 oil
• Castor oil Castor oil
• Propar 1800 Propar 1800 The viscosity measured at 40 ºC
η1(40ºC)=165 P
Casting Withdrawal speed: 3.7 m/sec.
Mould amplitude (Oscillated): 10 mm
η2(40ºC)=263 cP
Mould velocity: 0 to +36.77 / -36.77 η3(40ºC) = 12330 cP.
mm/sec At 40 ºC it shows that η3 which is
the Propar 1800, has the highest
Lubricant film thickness between Molten Bismuth Alloy viscosity of 12339 cP.
the strand and the mould wall (Bi=50%, Pb=25%,
were measured for various Sn=12.5%, Cd=12.5%)
lubricants in Boiled Water
Film Thickness Variation Result and Discussion
0.3
Propar 1800
Castor Oil
Castrol GTX 2 Castor GTX 2 Propar 1800
0.25 Castrol GTX
F T ic n s (m )
ilm h k e s m
0.2
0.15
0.1
1 10 100 1000 10000
Viscosity (cp)
Film thickness variation at various
lubricant viscosities applied during
continuous casting
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7. Conclusions
• Low melting point material i.e. Bismuth based alloy material
was successfully used in this continuous casting experimental
rig to study the film layer formation of hydrodynamic
lubrication at the strand mould interface.
• The initial film thickness variation occurring during continuous
casting as shown here is influenced by the viscosity of the
lubricant.
• The highest viscosity lubricant applied during casting
produces the thickest lubricant film. A higher estimate of film Pusat Teknologi Material
thickness was obtained for continuous casting where Propar Deputi TIEM - BPPT MASPI
1800 lubricant was used. Castrol GTX2 with the lowest
viscosity gave the lowest estimated film thickness during Gedung BPPT II, Lt
22, Jl. MH Thamrin
casting No. 8 Jakarta 10340
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