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] [ pressure die Casting Techniques]

[Die cast Part of automobile] [Die casting Fence fittings]

(Image courtesy: wiki)

(Hot Die Casting machine)

(Image courtesy: wiki)

There are two basic types of die casting machines: (1)hot-chamber machines (2) cold-chamber machines

cold-die-casting machine

(Image courtesy: wiki)

Attribute/process

sand investment Gravity die Pressure die

Max. size Several tons

Upto 20 kg Upto 50 kg Upto 8 kg

Dim. tolerance >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

Table : Capabilities of major casting processes

( 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)

MaterialMin. Thickness

mm (in)Min. Draft Angle (º)

Aluminum alloys0.9 mm

0.5

Zinc alloys0.6 mm

0.25

Copper alloys (Brass)1.25 mm

0.7

Minimum wall thicknesses and minimum draft angles for die casting are :

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.

Material Silicon CopperTensile Strength

MPa (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

Common aluminum alloys for die casting are summarized as follows:

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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