DIE CASTING

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DIE CASTING

• Presented by
• Chandra bhan prajapati
• 2008AMD2934

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The casting process is subdivided into two
distinct subgroups
1 - Expendable mold casting (sand, plastic,
shell, and investment (lost-wax technique)
mouldings.)
2 - Nonexpendable mold casting (permanent, die,
centrifugal, and continuous casting).
Classification of die casting (a)Gravity Die
Casting (also called permanent mould process)
(b)Pressure Die Casting
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Die Casting Process Flow
(Image courtesy wiki)
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pressure die Casting Techniques
Pressure-die casting
Die casting Fence fittings
Die cast Part of automobile
(Image courtesy wiki)
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There are two basic types of die casting
machines (1)hot-chamber machines (2)
cold-chamber machines

(Hot Die Casting machine)
(Image courtesy wiki)
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cold-die-casting machine
(Image courtesy wiki)
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Table Capabilities of major casting processes
Attribute/process sand investment Gravity die Pressure die
Max. size Several tons Upto 20 kg Upto 50 kg Upto 8 kg
Dim. tolerance gt0.6 mm gt0.1 mm gt0.4 mm gt.05 mm
Surface finish gt200 rms gt60 rms gt150 rms gt30 rms
Min. thickness gt6 mm gt1.5 mm gt4.5 mm gt0.8 mm
Economic quantity Any no. gt100 gt500 gt2500
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( Cooling Curve for casting) (Image courtesy
wiki)
Chvorinov's rule The local solidification time
can be calculated using Chvorinov's rule, which
is
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Structure
(Intermediate cooling rates from melt result in a
dendritic microstructure.
(Image courtesy wiki)
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Minimum wall thicknesses and minimum draft angles
for die casting are
Material Min. Thicknessmm (in) Min. Draft Angle (º)
Aluminum alloys 0.9 mm 0.5
Zinc alloys 0.6 mm 0.25
Copper alloys (Brass) 1.25 mm 0.7
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• Die casting materials
• Zinc the easiest alloy to cast high ductility
  high impact strength easily plated economical
  for small parts promotes long die life.
• Aluminum lightweight high dimensional stability
  for complex shapes and thin walls.
• Magnesium the easiest alloy to machine
  excellent strength-to-weight ratio lightest
  alloy commonly die cast.
• Copper high hardness high corrosion resistance
  highest mechanical properties of alloys die cast
  excellent wear resistance.

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Common aluminum alloys for die casting are
summarized as follows
Material Silicon Copper Tensile StrengthMPa (ksi) Properties
AA 380(UNS A03800) 8.5 3.5 324(47) Fair easy to fill
AA 384(UNS A03840) 11 4 331(48) Easy to fill
AA 386(UNS A03860) 9.5 0.6 317(46) Good corrosion resistance
AA 390(UNS A03900) 17 4.5 283(41) Good wear resistance
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• Advantages
• Excellent dimensional accuracy
• Smooth cast surfaces (12.5 µm rms).
• Thinner walls can be cast
• Inserts can be cast-in (such as threaded inserts,
  heating elements )
• Reduces or eliminates secondary machining
  operations.
• Rapid production rates.
• tensile strength as high as 415 MPa .

• Disadvantages
• Casting weight must be between 30 grams and 10 kg
  
• Casting must be smaller than 600 mm
• High initial cost.
• Limited to high-fluidity metals.
• A certain amount of porosity is common.
• Thickest section should be less than 13 mm
• A large production volume is needed to make this
  an economical .

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