LES Modeling of the Cold Crucible
Melting Process
E. Baake, A. Umbrashko,
Institute for Electrothermal Processes
University of Hanover (Germany)
A. Jakovics
Laboratory for Mathematical Modelling of Environmental and
Technological Processes, University of Latvia,
Riga (Latvia)
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2nd Sino-German Workshop on EPM Dresden 2005
Contents
 Introduction to the cold crucible skull
melting process
 Main features and optimisation potentials
 Numerical modeling and results
- Melt flow and temperature distribution
- Particle transportation
 Conclusions and Outlook
Chinese-German Project
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Cold crucible induction skull melting process I
p
vacuum chamber
M
crucible
Heizer
inductor
M
Induktor
Luft
Trichter
 High reactive and high
purity materials, e.g. TiAl
Evakuierung
Tiegel
Kokille
 Melting, alloying, overheating and casting
in one process
M
Argon
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Cold crucible induction skull melting process II
crucible
free surface
real
inductor
ideal
Optimisation potentials of the process
 Maximisation of the overheating
temperature, which is one of the
key parameter
 Improvement of the total efficiency and
reduction of energy consumption
contact point
wall-skull
 Control of the melt composition and
reduction of skull formation
bottom-skull
crucible-bottom
 Reliable, reproducible and stable
melting process
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Physical Correlations
magnetic field
- distribution of power
- electromagn. forces
velocity field
homogenisation of
melt
meniscus shape
geometry of melt
temperature field
- overheating
- heat flow
skull formation
alloy composition
liquid-solid-interface
melt components
optimisation of design and operating parameters
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Numerical models and numerical tools
start
3D-electromagnetic
- Commercial software
(ANSYS)
2D-meniscus shape
- self-developed code
calculation of
meniscus shape
stop criteria
fullfilled
3D-transient-LES
- Commercial software
(FLUENT)
no
Surface stability during semilevitation process allows to
uncouple electromagnetic and
fluid-dynamic calculations
calculation of
hydrodynamic and
thermal field
stop criteria
fullfilled
end
no
Shape of free surface is calculated
with self-developed finite-element
code
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Temperature and melt flow measurements in
aluminium
Thermo-couple with ceramic protection
Melt flow velocity sensor
stainlesssteel case
stainlesssteel holder
coil
6 14
35
magnet core
electrodes
E=vxB
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RANS (k-ε model)
DNS
• Whole energy spectrum is modelled
• All scales are resolved directly
• Relatively low mesh resolution
requirements
• Very high requirements for
computational resources
• Steady-state simulations
•Simulations of industrial installations
are impossible
CFD problem
Re  104
LES
• Large scales are resolved directly while only small
scales are modelled
• Relatively high mesh resolution requirements
• Transient 3D simulations
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Flow pattern and temperature distribution simulated
with 2D RNG k-ε turbulence model
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3D LES-modeling of cold crucible melting process
~3•106 elements
Time step 10 ms
Smagorinsky-Lilly subgrid
viscosity model
Parallel computations with
FLUENT 6.1 software at the
HLRN* supercomputer and
institute's workstation
cluster (4+1 AMD64 3200+)
*HLRN – scientific supercomputer
network of North Germany
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Results of 3D transient LES modeling with aluminium melt I
[m/s]
vm~40 cm/s
Time-averaged flow pattern
[m/s]
An intermediate flow pattern
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Results of 3D transient LES modeling with aluminium melt II
ºC
ºC
Time-averaged temperature
distribution
Measured temperature
distribution
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Velocity and temperature distribution in TiAl alloy
(LES and k-ε results)
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Temperature oscillations in the melt of the IFCC
T, K
Calculated
in TiAl
Measured in Al
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3D-instationary flow velocity distribution in the cold
crucible melting TiAl alloy calculated with LES model
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3D-instationary temperature distribution in the cold
crucible melting TiAl alloy calculated with LES model
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3D-instationary temperature distribution in the cold
crucible melting TiAl alloy calculated with LES model
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Melt flow velocity distribution for different crucible geometries
crucible radius: 8 cm
melt mass: 6 kg TiAl
power in the melt: 50 kW
crucible radius: 6 cm
melt mass: 6 kg TiAl
power in the melt: 50 kW
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Melt temperature distribution for different crucible geometries
crucible radius: 8 cm
power in the melt: 50 kW
total power: 275.3 kW
electrical efficiency: 18.2%
crucible radius: 6 cm
power in the melt: 50 kW
total power: 138.6 kW
electrical efficiency: 36.1%
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Transient 3D Particle Tracing I
Starting
Point
Starting
Point
- Density of particles and melt is equal
- 6 s of transient tracing in the melt
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Transient 3D Particle Tracing II
Starting
Point
Starting
Point
- Density of particles is 10 times smaller than melt density
- 3 s of transient tracing in the melt
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Conclusions and Outlook
 Heat and mass transfer processes in the melt of induction
furnaces are significantly influenced by large scale
low-frequency oscillations of the recirculating flow
 3D-transient LES is a reliable numerical tool to simulate the
turbulent melt flow and the heat and mass transfer in
cold crucible skull melting processes
 3D-LES model will be coupled with 3D-electromagnetic
model for the induction furnace with cold crucible
 Modelling of transient skull formation at the crucible wall and
particle transportation by electromagnetic forces in the melt
are in progress
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Chinese-German Project
founded by NSFC / DFG
Project Title:
Cold Crucible Induction Skull Melting
Process of Titanium Aluminium Alloys
Project Partner
Harbin Institute of Technology (HIT)
School of Materials Science and Engineering
Coordinator: Prof. Dr. Guo Jingjie
University of Hannover
Institute for Electrothermal Processes (ETP)
Coordinator: Prof. Dr.-Ing. Egbert Baake
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Contributions of HIT and ETP to the
cold crucible skull melting project
Harbin Institute of Technology (HIT)
• Experimental investigations of the TiAl melting process
especially form metallurgical point of view
• Investigations of the mechanism of skull formation
including the microstructure of the skull
• Investigations of melt composition control and evaporation
behaviour of alloy components
Institute for Electrothermal Processes (ETP)
• Numerical modeling of the skull melting process
including coupled 3D electromagnetic and 3D transient
melt flow and temperature fields
• Simulation of skull formation
• Investigations of design and process parameters
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Main Objectives of the Project (Draft)
• Experimental investigation and numerical simulation
of the complete cold crucible induction skull melting
process of TiAl
• Analysis and improvement of the process and design
parameters from electromagnetic, thermal,
hydrodynamic, metallurgical point of view
• Optimisation of the key parameters of the melting
process: overheating temperature of the melt, control
of melt composition, reduction of skull formation,
increasing of efficiency
• Investigation of up scaling criteria from small sized
units to large mass production furnaces
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Thank you for your kind attention!
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