Centrifugal casting
STAR-Cast‘s modelling basis
Motivation for centrifugal investment casting
Centrifugal investment casting of
● Low pressure turbine blades
● Turbocharger wheels
Future work
Talk overview
Centrifugal forces distributes the molten material in the mould
Rotation axis may be horizontal, vertical or inclined
Preferred for high quality cast parts
Rolls, nozzles, wheels, jewellery, etc
Casting materials: iron ,steel, alloys of Aluminium, Copper, Titanium etc
Top rollers
Casting
Mould Coating
Liquid metal Bottom rollers
Introduction to centrifugal casting
Schematic of horizontally rotated
bimetallic casting
Coupled flow and solidification model : Multi phase approach: gas, liquid and solidified metal
● HRIC: ensures sharp resolution of free surface, entrapped gas bubbles
● Porous walls: Escape of gas through shell moulds
● Interfacial forces: Surface tension and wetting angle effects
● Rotational forces : are modeled based on rotating frame of reference
● Moving grids: to model crucible tiling and pouring into the funnel
Polyhedral meshes: for complex geometries and multiphysics simulations
Material data: Comprehensive and fully documented data dedicated for casting simulation
High performance computing: Scales almost linear on parallel machines down to 10.000 cells per processor: STAR-Cast Power Version
STAR-Cast‘s modelling approach
Advanced liquid-solid state transition model
● Resistance to flow is a function of secondary dendrite arm spacing
Liquid Mushy Solid
fL= 0.0 fL= 0.3 fL= 1.0
STAR-Cast‘s modelling approach
Aero-engine manufacturers are introducing using new light weight materials
Intermetallic TiAl alloys
● 50% lower weight compared to conventional Ni-based alloys.
Centrifugal investment casting can deliver
high quality requirements
Ni basis Vs. TiAl blades
Casting of TiAl components with centrifugal investment process
But a difficult material to cast ● Potential of misrun ● Components like LPT blades have trailing edges of around 0.5 mm
Near-net-shape parts manufacture of Titanium Aluminides
HPC Vanes LPT Blades
Medical Implant Turbocharger Wheel
Typical casting defects in LPT blades
Misruns Porosity
The foundry engineer faces an uphill task!!!!
Gas entrapments
Ceramic Particles
Ceramic breakouts
Hot tearing
Induction Skull Melting Copper Crucible
Tilting
Melt Separation valve
(open) Heating
box Melting chamber
Casting chamber
Sprue
Melt distributor
Rotating table Rotation
Process characteristics
Two chamber system
Melting capacity: 10.0 kg (optional 25 kg)
Rotation speed:0-400 rpm
Mould filling in 1.5 seconds
Centrifugal investment casting LPT Blades
STEP 1: Simulate the crucible pouring process moving grids
Metal flow Velocity field
Simulation of the pouring process
Wetting
Simulation of the pouring process
Obtain inlet mass flow rate for the casting cluster Optimize the pouring process
Skull weights on funnel Funnel outflow
STEP 2: Simulate the casting cluster
● Generate the shell mould and mesh
● Apply inlet, initial and boundary conditions
● Use appropriate time step size (around 1.0e-4s)
● Solve on a high performance computing cluster
(With around 72 processors total computing time is 4
days)
Objectives: ● Predict misruns : i.e., if a fully filled blade is achievable or not
Simulation of the casting cluster of LPT blades
LPT blade Distributor
Runner Ingates
Inlet
Typical casting cluster of LPT Blades
Rotating at 200 RPM
Final outcome!!!!
Simulations
Casting designs
Next time anyone flying on an aircraft fitted with these blades be assured it has been developed using state-of-the-art tool STAR-Cast
Centrifugal investment casting TiAl turbo charger wheel
Centrifugal investment casting furnace, shell mold and turbocharger wheel
Centrifugal investment casting TiAl turbo charger wheel
Process characteristics
Melting capacity: 2.0 kg (max)
1 Chamber process
Wrapping around parts slows down the solidification
process
Ceramic shell mold calculated using the STAR-Cast shell mold generator
Centrifugal investment casting TiAl turbo charger wheel
Multiple frame of references coupled with solidification
Centrifugal casting of multiple alloys
Particle tracking during mould filling
Coupling to thermomechanics
Future work
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