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Dr. Barman Tambunan
Gedung BPPT II, Lt 22, Jl. MH Thamrin No. 8 Jakarta 10340
Pusat Teknologi Material (PTM) -Badan Pengkajian dan Penerapan Teknologi (BPPT)
Seminar Seminar MasyarakatMasyarakat PemulasPemulas Indonesia (MASPI)Indonesia (MASPI)
GedungGedung BPPT BPPT RuangRuang KomisiKomisi 33
Jakarta, 27 Jakarta, 27 MeiMei 20082008
Lubricant Film Thickness Estimation Lubricant Film Thickness Estimation at the Mould Inlet Region of a at the Mould Inlet Region of a Continuous Casting ProcessContinuous Casting Process
Objectives
To develop a thermal Reynolds equation applied to different surfaces velocities and temperatures condition
To implement the Thermal Reynolds equation to the inlet mould region of the continuous casting process
To estimate the mould inlet film thickness for various parameters in continuous casting
Research Question
How does the hydrodynamic lubrication in the mould region of a continuous casting process influence the casting product?
How can the thermal Reynolds equation be developed and implemented in the continuous casting process?
What are the influences of the various casting parameter to the lubrication in the continuous casting process?
Introduction• Practically all metals, which are not used in cast form are reduced to
some standard shapes for subsequent processing. • Manufacturing companies producing metals supply metals in form of
ingots which are obtained by casting liquid metal into a square cross section.– Slab (500-1800 mm wide and 50-300 mm thick)– Billets (40 to 150 sq mm)– Blooms (150 to 400 sq mm)
• Sometimes continuous casting methods are also used to cast the liquid metal into slabs, billets or blooms.
• 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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Sequence of operations for obtaining different shapes Steel Making Plant
• Surface quality• Internal quality
by sulphur print/ macro-etch
• Shape/dimension
• Temperature• Chemical comp.• Casting parameter
• Alloying (chemical comp.)• Desulfurisasi, deoksidasi,
dehidrogenisasi, decarburisasi
• Inclusion shaped control• Temperature
• Charging ratio• Chemical comp.• Temperature• Tap to tap time
INSPECTIONCASTINGSECONDARY METALLURGY
MELTING
STEEL MAKING PROCESS Continuous Casting Process
Area to be analyzed
End Product
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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.
Thermal Heat Transferin the Mold
• The slag between the steel shell significantly affects heat transfer.
• The mold wall is very cold, and causes the slag to freeze into a solid. The solid greatly reduces heat transfer.
• The slag along the shell stays hot, and in liquid form. It lubricates.
MOLDWALL
Solid Flux Film
Liquid Slag
SolidifyingShell
Heat Flux
Air Gap
Provides Liquid Lubrication in Gap Between Mold and
Solidifying Shell
Mold Wall
SolidFlux
LiquidSlag
Steel Shell
FluxVelocity
Liquid slag is drawn down into the gap along the steel shell. The liquid is a lubricant, allowing the steel to be withdrawn without sticking to the mold wall. If the steel sticks to the wall, it causes a breakout.
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Temperature Distribution of the Slab
Temperature Distribution of the Transverse Slice at the Mould Exit (time t = 39.4 sec)
Mould Flux Infiltration Analysis
h
ho
Mould
Lubricant
MoltenSteel Pool
Solidified Steel Strand
Meniscus Regionz
x
u2
T1
T2
x0
FerrostaticPressure
Centre of the Mould
Top of the MouldCenter line
( )⎟⎟⎠
⎞⎜⎜⎝
⎛ −++−−
⎥⎥
⎦
⎤
⎢⎢
⎣
⎡
−−=
212ln12
22ln
222
222qxq
xqq
xqH
Film thickness
H : Non-dimensional film thickness equation in the meniscus region
±u1
(Ref. Jimbo et al. (1991)) ( )2
12
⎟⎟⎠
⎞⎜⎜⎝
⎛Δ
=g
qργ
Thermal Reynolds Equation
⎟⎠⎞
⎜⎝⎛
∂∂
∂∂
=∂∂
=∂∂
zu
zzxP μτ The Pressure
Gradient = Shear Stress
EzTk =
∂∂
2
2
Constant Energy Dissipation∫
−
=2
2
h
h
dzuQ The Flow Rate
⎭⎬⎫
⎩⎨⎧
⎟⎠⎞
⎜⎝⎛ −
−−=2
exp 12 TTTs αμμThe viscosity of the mould lubricant
Thermal Reynolds Equation
( )QUhhpR
s −=
μ12
3'
( )2
2
khQUhF s −
=αμ
( )12 TTD −=α
( )k
uuS s2
21 −=αμ
khEE
2* α=
Non-dimensional Pressure Gradient
Non-dimensional Thermal Backflow parameter
Non-dimensional Temperature difference
Non-dimensional Velocity
Non-dimensional Energy Dissipation
kuL
20 αμ
=Non-dimensional Thermal Loading Parameter
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Applying Thermal Reynolds
Thermal Reynolds equation with the non-dimensional film thickness parameter H
( )RH
HAH
Gxd
dB32
00
1−=
32
20
220 12 ⎟⎟
⎠
⎞⎜⎜⎝
⎛=
tot
Fertot xU
PxAμFerPG γ=
The thermal Reynolds equation with the correction factor R was integrated numerically using a Fourth order Runge-Kutta program
peB γ−=3
1
20
00 12 ⎟⎟⎠
⎞⎜⎜⎝
⎛=
tot
Fer
xUPhHμ
Results and Discussion
0
0.5
1
1.5
2
2.5
3
3.5
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
G=1G=2G=3G=4G=5
Thermal Loading L(1/6)
Film Thickness Ho.L(1/6)
G=1
G=2
G=3
G=4
G=5
Film thickness variation for D = 2, S = 0 and various G
The Continuous Casting Rig
Oscillating Plate•Mould cylinder 32.5 mm •Outer diameter 74 mm •Length 400 mm
Lubricant Reservoir
Withdrawal Motor
Modelling
MLP-50 Load Cell
LVDT
molten bismuth based alloy
Copper Mould
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Evaluation of Continuous Casting
Lubricant film thickness between the strand and the mould wall were measured for various lubricants
Casting Withdrawal speed: 3.7 m/sec. Mould amplitude (Oscillated): 10 mm Mould velocity: 0 to +36.77 / -36.77 mm/sec
Produced Round Billet Shaped Cast
Molten Bismuth Alloy (Bi=50%, Pb=25%, Sn=12.5%, Cd=12.5%) in Boiled Water
• Castrol GTX2 oil• Castor oil• Propar 1800
Lubricant Applied during Casting:
Lubricant
Lubricant :Castrol GTX2 oilCastor oilPropar 1800 The viscosity measured at 40 ºC
η1(40ºC)=165 Pη2(40ºC)=263 cPη3(40ºC) = 12330 cP. At 40 ºC it shows that η3 which is the Propar 1800, has the highest viscosity of 12339 cP.
Film Thickness Variation
0.1
0.15
0.2
0.25
0.3
1 10 100 1000 10000
Viscosity (cp)
Film
Thi
ckne
ss (m
m)
Propar 1800
Castor Oil
Castrol GTX
Film thickness variation at various lubricant viscosities applied during
continuous casting
Result and DiscussionCastrol GTX 2 Castor GTX 2 Propar 1800
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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 continuouscasting 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 thickness was obtained for continuous casting where Propar1800 lubricant was used. Castrol GTX2 with the lowest viscosity gave the lowest estimated film thickness during casting
Gedung BPPT II, Lt 22, Jl. MH ThamrinNo. 8 Jakarta 10340
MASPIPusat Teknologi Material
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