The liquid metal is injected into the mold under high pressure and allowed to solidify at the high pressure. It is common for Al, Zn and Mg castings.
The solidified cast is then taken out of the mold that is ready for the next cast. Pressure die casting is suitable for large batch size production.
Two types of pressure die casting. These are
High pressure die casting (Hot chamber die casting)
Low pressure die casting (Cold chamber die casting)
In pressure die casting very high production rates achieved with close dimensional control of the casting.
This method is not suitable for high melting temperature casting materials because die material has to withstand the temperature of the casting.
It contain porosity because of the entrapped air then the die in the pressure die casting process are very costly.
HOT-CHAMBER DIE-CASTING :
In hot chamber die-casting the metal is melted in a container attached to the machine.
A piston is used to inject the liquid metal under high pressure into the die.
The furnace to melt the material is component of the die itself thus the method is suitable for low-melting point temperature materials.
ADVANTAGES:
High productivity
Close tolerances
Good surface finish
DISADVANTAGES:
The injection system is submerged in the molten metal.
Only simple shapes.
APPLICATION:
Mass production of non-ferrous alloys with very low melting point.
COLD-CHAMBER DIE-CASTING
Molten metal is poured into the chamber from an external melting container.
A piston is used to inject the metal under high pressure into the die cavity.
ADVANTAGES:
Same as in hot chamber die-casting but less productivity.
DISADVANTAGES:
Only simple shapes.
APPLICATION:
Mass production of aluminium and magnesium alloys and brass.
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