Dia Casting And Its TypesBy Alpha Metal Industries

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

Aluminum Pressure Die Casting [ pressure die Casting Techniques]

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

(Hot Die Casting machine)

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

cold-die-casting machine

ALUMINUM GRAVITY DIE CASTING

Structure:

(Intermediate cooling rates from melt result in a dendritic microstructure.

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

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 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

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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