Casting Simulations with STAR-Cast Julian Gänz, CD-adapco
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Casting Simulations with
STAR-Cast
Julian Gänz, CD-adapco
Need for Casting Simulation
Processes
Permanent Mold
Tilt –Casting
Low Pressure-Casting
High Pressure Die
Casting
Continuous Casting
...
Lost Mold
Sand Casting
Precision Casting
Centrifugal
Bridgeman
...
From Modern Casting
“2010 world census casting production”
Material Cost/tonne [$] Relative
Carbon Steel 550 1
Cast Iron 830 1,51
Aluminium/alloys 2220 4,0
Titanium /alloys 17 000 30,9
38,16
19,4
9 13,6
Market Overview [Mio tons]
Grey Iron
Ductile Iron
Steel
Non Ferrous alloys
• Variety of processes and materials
• Sophisticated geometries
• Simulation can help to meet the different and often contradicting demands
– Requirements
• Mold filling with solidification
• Defect Prediction
• Design tool
Need for Casting Simulation
12000 30000
100000 120000 150000
Tool Cost [$]
Fro
m A
ustin G
roup 2
002
Call for advanced
casting processes
• Best of both worlds
– Provide state of the art of casting simulation solution by combining the
engineering experience of two companies which have a long-standing
track record in providing CAE solutions and casting processes for over
25 years
– Established casting solution STAR-Cast
Strategic Partnership
• First released in 2009
• Dedicated design and engineering tool for the casting engineer
• Core -Capabilities
• Multiphase
• Resolution of the molten flow and filling front
• Model phase change
• Dedicated material database
• Dedicated User Interface
• STAR-CCM+’s state of the art meshing
STAR - Cast
• Speaking the language of the casting engineer
• Quickly adaptable to simulation needs
The Process
Geometry
• Any given CAD data
• 3D-CAD Modeller
Mesh
• Fluid /Solid Interfaces
• Appropriate meshing models
Physics
• Adapt to simulation goal
• Expandable
Post processing
• Transient Postprocessing
• Criteria functions, defect analysis
• VOF
• Isothermal- gating design
• Thermal - cooling/ solidification
• Particles/ erosion
Filling
• Progress of Solidification
• Influence on flow
• Misruns and cold shut Solidification
• Piston Motion
• Tilting
• Rotation Motion
• A dedicated Material Database is available in STAR-Cast, pooling
all relevant material information for the casting engineer
Industrial Challenge - Materials
• Mushy / Slurry Zone
– Transition from liquid to solid leads to partially solidified areas
– Carman Kozeny approach
• Solid - Flow Stop
– Complete stop of flow in solidified areas
Industrial Challenge - Solidification
Liquid Mushy Solid
fL= 0.0 fL= 0.3 fL= 1.0
vvK
Cv
Kx
p E
i
180f
)f1(),f(K
22
2s
3s
2s
• Deduct additional information about the solidification process
and the overall quality of the cast
• Gather Temperature gradients, cooling rates and local solidification times
• Compute criteria functions, such as Niyama or G/v criterion
• Estimate porosity characteristics
Industrial Challenge - Defect Prediction
centre line porosity
Ref: Access, STAR-Cast 1.10
• Phase selective wall porosities for VOF- Phases
– Capture the venting effect of a porous mold, core ( i.e. Sand, Investment
mold)
Industrial Challenge - Porous molds
Porosity to low Calibrated porosity
• Multi region problem ...
– Complex Geometry
– Fluid Cavity
– Surrounding Air
– Different solids ( mold, cooling
iron ..)
... Meshing requirements:
– Easy surface repair
– Multi region Volume meshing
– Prism layers
– Cell count effective meshing in
thin areas
Industrial Challenge - Complexity
Investment Casting: Shell generation
• For precision casting
– Dipping a wax model into a ceramic
based slurry
– Ceramic slurry dries and builds the
mold for the casting
– Wax is removed in an autoclave
Automatic shell mold generation
• Shell mold generator
– Mimics a manufacturing process
– Based on local curvature
Investment Casting: Shell generation
Investment Casting
• Challenges in Investment Casting
– Thin-walled components with designs at the limit of producibility
– Late design freeze, thus shorter development cycles
– New materials
– New processes
Investment Casting
Courtesy of
Access e.V.
• Answers Engineers are seeking
– Sensitivity analyses for process parameters, running and gating system
– Geometrical parameter studies
– Enhancement and conservation of raw materials and reduction of overall
manufacturing cost
Investment Casting
Example of a mould-filling optimization
Initial setup Optimized setup
Sprue cup
Crucible
Courtesy of
Access e.V. &
CD-adapco
Example of a mold-filling optimization 1
7
Non-optimized Optimized
Simulations show that in a non-optimized distributor the liquid metal
keeps rotating in the distributor for a longer time before entering the
sprue
• What kind of Defects are of relevance for Investment
Castings:
• Misruns
• Porosity
• Freckles
• Stray grain formation
• Segregation
• Hot tearing
Investment Casting
Predictions of misruns in a gravity-cast LPT blade 1
9
Shell
Mould
Runner
Blade
Schematic diagram of the process Polyhedral Volume Mesh
Sprue
Inlet
Comparison of simulation and casting trials
Gravity casting, Access
TechCenter
Value of secondary dendrite arm spacing was obtained from microstructure measurements
Magnitude of velocity Temperature
Courtesy of Access e.V. &
CD-adapco
DS/DX Castings: Stray Grain Formation
• Stray grains form when
corners of the part solidify and
there is no connection to the
main solidification front.
Marked corner will show a stray grain
• Enhance accuracy, robustness and ease of use for a wider range
of casting processes
• Include further solidification models
– Ductile Iron, Grey Iron
– Composite castings
• Next STAR-Cast release:
» Fully Based on STAR-CCM+
Looking ahead
• Latest solver and meshing capabilities
• Modern and easy handling
• All the physics to carry out casting simulations
– Material Database
– Shell mold generator
– Defect prediction
• Add on module to STAR-CCM+
STAR-Cast embedded in STAR-CCM+ : v8.02
• Dedicated mesher for investment
casting
– Automated Region generation
– Prism Layer + Embedded Thin Mesh
in thin areas
• Streamlined Workflow
• Simple set of input variables
STAR-Cast embedded in STAR-CCM+: 8.04
• Process driven GUI for casting applications:
– New approach to STAR-CCM+
– GUI adapts to the selected casting process
– “Best Practices” are stored
– High level of automation
– Guide the user through process
STAR-Cast embedded in STAR-CCM+ : Outlook
• Concept
• Expose only required functionalities
• Use casting terminology
• Shorten the learning curve
• “Conditions”: reusable
• Input is stored in an XML file
STAR-Cast embedded in STAR-CCM+ : Outlook
Casting Simulations with
STAR-Cast
Julian Gänz, CD-adapco
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