numerical modeling in copper billet casting

NUMERICAL MODELING IN

COPPER BILLET CASTING

Ioannis Contopoulos, ELKEME

Numerical Modeling Department

1

ELKEME

• The R&D Center of VIOHALCO

• Founded 1999

• Industrial research, technological

development and analysis of

– Aluminum

– Copper

– Steel

– Zinc

Lab/Section Name 2

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

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


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.)


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


Process Metallurgy

Physical Metallurgy &

Forming

Corrosion

Environmental

Metallography & Electron Optics

Mechanical Testing &

Manufacturing Technology

Numerical Modeling

Surface Science & Coatings

Analytical Chemistry

ELKEME Numerical Modeling

13 Numerical Modeling Department

14

ELKEME Numerical Modeling

• Software:

– ANSYS Workbench

• Design Modeler

• Meshing

• Fluent (FV)

• Mechanical Enterprise (FE)

– Design Explorer

– AQWA

• 2 HPC

• Maxwell 2D


NUMERICAL MODELING IN

COPPER BILLET CASTING

Ioannis Contopoulos, ELKEME


17

Numerical Modeling

• Deeper understanding of process

• Virtual variation of operation parameters

• Assists in

– Identifying critical process parameters

– Optimizing production process

– Improve productivity


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 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 problems

• We tried many different numerical

approaches

• We were able to obtain convergent

solutions that we can trust!


Numerical grids


23

air gap

distributor

water curtain mould: ΔΤwater=+1 oC

air gap mould

distributor

water curtain

3D phi-periodic (8 inlets)


27

3D asymmetric installation

Hotter side


28

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 155Casting Speed (mm/min)

Liq

uid

Po

ol

Dep

th (

mm

) 91kW

136kW

181kW

Linear (91kW)

Linear (136kW)

Linear (181kW)


29

Low Medium

Casting Speed

High

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)

Pri

mary

co

oli

ng

zo

ne w

idth

(m

m)

91kW

136kW

181kW

Linear (91kW)

Linear (136kW)

Linear (181kW)


30

Low Medium

Casting Speed

High

Solidification rates


31

Primary Conclusions

• The original setup had limitations that did

not allow the increase of productivity

• Setup asymmetries

Fix


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 !


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


220mm air gap

155mm/min

Water cooled

mold

Air gap

Water curtain

Third part

Second part

First part Setup A

220mm air gap

165mm/min

Water cooled

mold

Air gap

Water curtain

Third part

Second part

First part Setup B

270mm air gap

165mm/min

Water cooled

mold

Air gap

Water curtain

Third part

Second part

First part Setup C

220mm air gap

165mm/min Semi-solidified

zone

Meta

losta

tic

pre

ssu

re

Zone of

slow solidification rate

Setup B

Zone of

slow solidification rate

Metalostatic pressure

required to fill

solidification shrinkage

porosity

220mm air gap

165mm/min

Re-heated zone

prone to remelting

of eutectics

Setup B

220mm air gap

165mm/min

Mold exit temperature

around 850-900oC

non uniform

air gap temperature

Setup B

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


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
