Transcript Slide 1

Presented by:
Chandra bhan prajapati
2008AMD2934
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
Die Casting Process Flow
(Image courtesy: wiki)
[Pressure-die casting]
[Die cast Part of automobile]
[ pressure die Casting Techniques]
[Die casting Fence fittings]
(Image courtesy: wiki)
There are two basic types of die casting machines:
(1)hot-chamber machines
(2) cold-chamber machines
(Hot Die Casting machine)
(Image courtesy: wiki)
cold-die-casting machine
(Image courtesy: wiki)
Table : Capabilities of major casting processes
Attribute/proc
ess
Max. size
sand
investment
Gravity die
Pressure die
Upto 20 kg
Upto 50 kg
Upto 8 kg
Dim. tolerance
Several
tons
>0.6 mm
>0.1 mm
>0.4 mm
>.05 mm
Surface finish
>200 rms
>60 rms
>150 rms
>30 rms
Min. thickness
>6 mm
>1.5 mm
>4.5 mm
>0.8 mm
Economic
quantity
Any no.
>100
>500
>2500
( Cooling Curve for casting)
(Image courtesy: wiki)
Chvorinov's rule:
The local solidification time can be calculated using Chvorinov's rule,
which is:
Structure:
(Intermediate cooling rates from melt
result in a dendritic microstructure.
(Image courtesy: wiki)
Minimum wall thicknesses and minimum draft angles for die casting
are :
Material
Aluminum alloys
Zinc alloys
Copper alloys (Brass)
Min. Thickness
mm (in)
0.9 mm
0.6 mm
1.25 mm
Min. Draft Angle (º)
0.5
0.25
0.7
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 strengthto-weight ratio; lightest alloy commonly die cast.
•Copper: high hardness; high corrosion resistance; highest
mechanical properties of alloys die cast; excellent wear
resistance.
Common aluminum alloys for die casting are summarized as fol
Silicon
Copper
Tensile Strength
MPa (ksi)
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
Material
Properties
Advantages:
•Excellent dimensional accuracy
•Smooth cast surfaces (1—2.5 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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