Casting Processes
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ME 4210: Manufacturing Processes and Equipment Prof. J.S. Colton GIT 2011
Types of Parts Made
Engine blocks Pipes Jewelry Fire hydrants
ME 4210: Manufacturing Processes and Equipment Prof. J.S. Colton GIT 2011
Complex, 3-D shapes
Near net shape Low scrap Relatively quick process Intricate shapes Large hollow shapes No limit to size Reasonable to good surface finish
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Processes
Sand Shell Plaster Ceramic Investment Lost foam Pressure Vacuum Die Centrifugal Squeeze Semi-solid Single crystal Directional solidification Slush Continuous
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ME 4210: Manufacturing Processes and Equipment Prof. J.S. Colton GIT 2011
Metals processed by casting
Sand casting 60% Investment casting 7% Die casting 9% Permanent mold casting 11% Centrifugal casting 7% Shell mold casting 6%
ME 4210: Manufacturing Processes and Equipment Prof. J.S. Colton GIT 2011
Breakdown of Castings
Ingots for bulk deformation processing 85% Cast to near net shape - 15%
ME 4210: Manufacturing Processes and Equipment Prof. J.S. Colton GIT 2011
Ingots
Iron or steel molds Water-cooled molds Continuous casting
ME 4210: Manufacturing Processes and Equipment Prof. J.S. Colton GIT 2011
Shapes
Permanent mold (cavity)
die casting hot chamber cold chamber
Expendable Molds
sand shell slurry investment
lost wax lost foam
ME 4210: Manufacturing Processes and Equipment Prof. J.S. Colton GIT 2011
Shapes
Centrifugal
pipes spinning
Capabilities
Dimensions
sand casting - as large as you like small - 1 mm or so
Tolerances
0.005 in to 0.1 in
Surface finish
die casting 8-16 micro-inches (1-3 mm)
sand casting - 500 micro-inches (10-25 mm)
Casting Steps
quick route from raw material to finished product
Melt metals Pour / force liquid into hollow cavity (mold) Cool / Solidify Remove Finish
Melting
Raw material (charge)
scrap, alloying materials
Heat
Furnace Atmosphere
Atmosphere Heating
Raw materials
Air (oxygen), vacuum, inert gas (argon) External - electric, gas, oil Internal - induction, mix fuel with charge
steel making in blast furnace -mix coke with iron
Furnace material
refractory ceramics
Furnaces
Blast furnace
Basic Oxygen Furnace
Furnaces
Electric Arc Furnace
Oxygen-Fuel, Oxygen Lance Furnace
Furnaces
Induction Furnace
Electric Furnace
Sand Casting
ME 4210: Manufacturing Processes and Equipment Prof. J.S. Colton GIT 2011
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Sand Casting
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Sand Casting
S
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Sand Casting Steps
S
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Sand Cast Parts
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Permanent Mold Casting
P
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Low Pressure Casting
M
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Die Casting (high pressure)
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Die Casting Machine
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Die Casting
n
Cold chamber
Hot chamber
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Direct Squeeze Casting
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Die Casting Part Example
C
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Continuous Casting
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Investment Casting
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Vacuum Casting
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Investment (top) and Conventional Castings
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Lost Foam Casting
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Lost Foam Castings
L
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Centrifugal Casting
s
horizontal
sand-lined mold casting
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vertical
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Centrifugal Casting
Pipe Casting Process
Directional Solidification
Casting Characteristics
Table 5.6 Typical materials cast
All All
Weig ht (kg)
Process
Sand Shell Expendab le mold pattern
Minimum Maximum
0.05 0.05 No limi t 100+
Typical surface finish (micron, Ra)
5-25 1-3
Section thickness (mm ) Shape complexity Di mensional Minimum Maximum * accuracy* Porosity*
4 4 1-2 2-3 3 2 3 2 No limi t --
All Nonferrou s (Al, Mg, Plaster Zn, Cu) mold All (High melting pt.) Investment Permanen t mold All Nonferrou s (Al, Mg, Zn, Cu) Die Centrifuga l All
0.05
No limi t
5-20
No limi t
0.05
50+
1-2
1-2
--
0.005 0.5
100+ 300
1-3 2-3
3 2-3
1 3-4
1 1
1 2
75 50
<0.05 50 1-2 1-2 3-4 1 -5000+ 2-10 1-2 3-4 3 *Relative rating: 1 best, 5 worst. Note : These ratings are only gene ral; significant variations can occ ur, depend ing on the method s use d d.
0.5 2
12 100
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Microstructure
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Microstructure - Dendrites
Finer structure at walls Grains / dendrites grow to center
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Grains on Willie Bs head
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Microstructure - Dendrites
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Fluidity
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Casting Defects - Porosity
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Casting Defects
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Shrinkage
TABLE 5.1 Volumetric solidification contraction (%) 6.6 6.3 3.8 2.53 4 4.9 Volumetric solidification contraction (%) 4.5 4 Expansion to 2.5 4.2 45.5 6.5
Metal or alloy Aluminum Al4.5%Cu Al12%Si Carbon steel 1% carbon steel Copper Source: After R. A. Flinn.
Metal or alloy 70%Cu30%Zn 90%Cu10%Al Gray iron Magnesium White iron Zinc
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Differential Cooling
Transition between thicker and thinner sections can lead to porosity
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Pipe Defect
Due to shrinkage giving rise to a funnel-like cavity Solutions
insulate top (glass wool) heat top (exothermic mixture thermit)
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Defects - Hot Tears
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Chills
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Car Rims
Stamped
Cast
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ME 4210: Manufacturing Processes and Equipment Prof. J.S. Colton GIT 2011
Casting Defects - Porosity
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Design Rules Summary
Uniform wall thickness Flat parting lines Gradual thickness transitions Draft for removal
tapers: 0.5 to 2 degrees
Surface of mold gives surface of part
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Sand Casting Rules
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Casting costs
TABLE 5.10 Cost* Process Die Equipment L M-H M L-M M H H Labor LM LM MH H LM LM LM Production rate (Pc/hr) <20 <50 <10 <1000 <60 <200 <50
Sand L Shell-mold LM Plaster LM Investment MH Permanent mold M Die H Centrifugal M * L, low; M, medium; H, high.
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Process economics
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