Deeper understanding of process Virtual variation of operation parameters Assists in –Identifying critical process parameters –Optimizing production process –Improve productivity

1. NUMERICAL MODELING IN
COPPER BILLET CASTING
Ioannis Contopoulos, ELKEME
Numerical Modeling Department 1

2. ELKEME
• The R&D Center of VIOHALCO
• Founded 1999
• Industrial research, technological
development and analysis of
–Aluminum
–Copper
–Steel
–Zinc
Lab/Section Name 2

3. ELKEME
• Applied technology research towards
– Quality Improvement of existing products
– Development of new, innovative, high added
value products
– Optimization of Industrial Processes
• Energy and cost efficiency
• Health and safety
• Environment and sustainable growth
Numerical Modeling Department 3

4. ELKEME
• State of the art laboratories
• Highly capable scientists, engineers,
technicians
• Continuous professional development
• Collaborations with External Laboratories
• Research projects in Metallurgy, Material
Sciences and Environmental Engineering
• Build knowledge and competence network
Numerical Modeling Department 4

5. ELKEME
• Long term relationships with academic and research
institutes (National Tech. Univ. of Athens, Universities of
Patras, Ioannina, Delft, Ghent, Manchester)
• Supervision of Diploma/Master’s/PhD theses
• Student training programs
• Seminars
• International collaborations
• Participation in international scientific/engineering
associations
• Contributions to scientific journals and conferences
(ICEFA, ICAA, ICEAF, Thermec, TMS, etc.)
Numerical Modeling Department 5

6. 100
120
140
160
180
200
220
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7(mm)
ΗV1.0
1

9. Numerical Modeling Department 10
Process
Metallurgy
Physical
Metallurgy &
Forming
Corrosion
Environmental
Metallography &
Electron Optics
Mechanical
Testing &
Manufacturing
Technology
Numerical
Modeling
Surface Science
& Coatings
Analytical
Chemistry

10. ELKEME Numerical Modeling
13Numerical Modeling Department

11. 14
ELKEME Numerical Modeling
• Software:
– ANSYS Workbench
• Design Modeler
• Meshing
• Fluent (FV)
• Mechanical Enterprise (FE)
– Design Explorer
– AQWA
• 2 HPC
• Maxwell 2D
Numerical Modeling Department

12. Numerical Modeling Department 15

13. NUMERICAL MODELING IN
COPPER BILLET CASTING
Ioannis Contopoulos, ELKEME
Numerical Modeling Department 17

14. Numerical Modeling
• Deeper understanding of process
• Virtual variation of operation parameters
• Assists in
– Identifying critical process parameters
– Optimizing production process
– Improve productivity
Numerical Modeling Department 19

15. Numerical setup
• ANSYS Fluent 12.0/16.2, solidification model
• Double precision, axisymmetric, 1mm mesh resolution
• Geometry: mold, distributor, air gap, water curtain
• Insulated top (graphite flux)
• DHP Copper physical properties (thermal properties,
solidification properties: latent heat, liquid fraction,
porosity)
– No thermal shrinking
– No micro/macro solute segregation
• Casting speeds: A→1.15A→1.20A→…
• Various cooling setups
Numerical Modeling Department 20

16. Numerical problems
• The simulation of casting is a very difficult
numerical problem. The fast transition from the
liquidus to the solidus temperature (energy
release-latent heat, viscosity transition from liquid
to solid) makes the equations very “stiff”: small
changes lead to instabilities and to the destruction
of the solidification front
• It is very difficult to find a convergent solution
• Unless one finds a convergent solution, one must
not trust the small details of the final result
Numerical Modeling Department 21

17. Numerical problems
• We tried many different numerical
approaches
• We were able to obtain convergent
solutions that we can trust!
Numerical Modeling Department 22

18. Numerical grids
Numerical Modeling Department 23

19. air gap
distributor
water curtain mould: ΔΤwater=+1 oC

20. air gap
distributor
water curtain mould: ΔΤwater=+1 oC

21. air gap mould
distributor
water curtain

22. 3D phi-periodic (8 inlets)
Numerical Modeling Department 27

23. 3D asymmetric installation
Hotter side
Numerical Modeling Department 28

24. 3-D periodic simulation: Corellation between casting speed and
liquid pool depth
490
500
510
520
530
540
550
560
125 130 135 140 145 150 155
Casting Speed (mm/min)
LiquidPoolDepth(mm)
91kW
136kW
181kW
Linear (91kW)
Linear (136kW)
Linear (181kW)
Numerical Modeling Department 29
Low Medium
Casting Speed
High

25. 3-D periodic Simulation: Correlation between casting speed and
primary cooling zone width
0
5
10
15
20
25
30
35
40
45
125 130 135 140 145 150 155
Casting Speed (mm/min)
Primarycoolingzonewidth(mm)
91kW
136kW
181kW
Linear (91kW)
Linear (136kW)
Linear (181kW)
Numerical Modeling Department 30
Low Medium
Casting Speed
High

26. Solidification rates
Numerical Modeling Department 31

27. Primary Conclusions
• The original setup had limitations that did
not allow the increase of productivity
• Setup asymmetries
 Fix
Numerical Modeling Department 32

28. Revisited problem 2015
• Basic factors related with productivity:
– Depth/Geometry of molten metal in mould
 Modifications
 Speed increase 15-20% !
 Need to go even faster!
• Setup asymmetries
 Fixed !
Numerical Modeling Department 33

29. Preliminary results 2015
• The shape of the solidification front
consists of 3 parts:
1. The growing solidification front in the mold
2. An almost cylindrical front in the air gap
region below the mold
3. A V-shaped final solidification front in the
water curtain region
Numerical Modeling Department 34

30. 220mm air gap
155mm/min
Water cooled
mold
Air gap
Water curtain
Third part
Second part
First part Setup A

31. 220mm air gap
165mm/min
Water cooled
mold
Air gap
Water curtain
Third part
Second part
First part Setup B

32. 270mm air gap
165mm/min
Water cooled
mold
Air gap
Water curtain
Third part
Second part
First part Setup C

33. 220mm air gap
165mm/min
Semi-solidified
zone
Metalostaticpressure Zone of
slow solidification rate
Setup B

34. Zone of
slow solidification rate

35. Metalostatic pressure
required to fill
solidification shrinkage
porosity

36. 220mm air gap
165mm/min
Re-heated zone
prone to remelting
of eutectics
Setup B

37. 220mm air gap
165mm/min
Mold exit temperature
around 850-900oC
non uniform
air gap temperature
Setup B

38. Conclusions
• The shape of the central solidification front
depends only on the casting speed
• The improvement IS NOT due to changes in
the shape of the front at the center
• Increased metalostatic pressure compensates
for solidification shrinkage porosity
• Thermo-mechanical investigation of cooling
beyond solidification
Numerical Modeling Department 44

39. Conclusions
• Increasing the height of the air gap leads
to secondary problems due to very slow
solidification rates and/or remelting at
intermediate radii
• Future trials:
– Modified cooling
– Thermo-mechanical investigation with ANSYS
Mechanical
Numerical Modeling Department 45