Die casting is done by introducing molten metal into th […]
Die casting is done by introducing molten metal into the mold at high or low pressure. Earlier only low-pressure die-casting was used but nowadays high pressure die casting is used more extensively. Molds are well designed to give complex products with stunning accuracy and smooth finishing. They are made of high quality steel as steel has higher melting point. These molds can be reused thousands of times. Casts can be single cavity that produces only a single component, multiple cavity that produces multiple identical parts at a time, unit die that produces different parts and combination die that produces different parts in one go. Usually zinc, copper, aluminium, magnesium, lead, pewter and tin based alloys are used for die casting.
Using die casting we can make products with pore-free products that do not allow gas to pass though them and making them strong. Two types of machines are used for die-casting. Cold-chamber and hot-chamber die-casting.
Hot-chamber die casting is used for high-fluidity metals. First the molten metal is collected using goose neck and then the metal is shot into the mold. The advantage of this method is the cycles/min are increased. But the disadvantage is that high melting point metals and aluminum pick-sup iron particles.
Cold chamber die casting is used where hot-chamber can not be used. In this process the molten metal is transferred to the injector and then the injector injects the metal into the mold. Metals with high melting points can be die casted using this process but the disadvantage is it is slow than hot-chamber process.
Die Casting Process
In this process molten metal or other materials are forced, under high pressure into the cavities of the steel mold. Dies are two part molds that are made of alloy tool steel - The fixer die half and the ejector die half. The die or mold is fabricated with the impression of the component that is to cast. There are four types of dies,
l Single cavity to produce one component
l Multiple cavity to produce a number of identical parts
l Unit die to produce different parts at one time
l Combinations die to produce several different parts for an assembly
The molten metal is injected into the die under high pressure and high speed, which helps in producing a casting that is smooth and precise as the original mold. The pressure is maintained on the mold until the hot metal solidifies. When the metal is hardened, the die is opened to remove the casting.
There are several variations on the basic process that can be used to produce castings for specific applications. These include:
Squeeze casting - A method by which molten alloy is cast without turbulence and gas entrapment at high pressure to yield high quality, dense, heat treatable components.
Semi-solid molding - A procedure where semi-solid metal billets are cast to provide dense, heat treatable castings with low porosity.
Economical process that can be used for a wide range of complex application
Parts have longer service life, dimensional accuracy and close tolerance
Post machining can be totally eliminated
A process that can be fully automated
Mold can be use repeatedly.