Using aluminium casting
are searching the areas where they may replace iron parts with aluminium parts. Most auto producers prefer alloys of aluminium specially the A 300 series which have a mix of silicon and a minor amount of magnesium.Silicon material provides fluidity while casting, which allows thinner parts to be cast. The magnesium will give strength. An important feature of aluminum is that in comparison with ferrous alloys which show a unlimited fatigue strength. The fatigue strength of aluminum alloys goes down with increase in number of stress cycles this needs to be taken into account while designing its parts.
When we need a high quality aluminium casting, we have to follow a variety of processes. While casting permanent molds precautions are taken to ensure that it gets required cooling and vacuum pressure is also applied to ensure correct flow and lessen porosity.
Aluminum alloys are more utilized in die aluminium casting than alloys of any metal. In USA alone 2.5 billion dollars worth aluminum alloy die castings are manufactured every year. Die aluminium casting is suitable for production of smaller parts. But when expensive manufacturing equipment
is used the castings weigh 5kg-50kg. Cost effectiveness of die aluminium casting can be obtained only by large scale production. With die casting it is possible to have close tolerance and fine finishing surface. Die castings are manufactured by injecting melted metal into metal molds under considerable pressure. Quick injecting and quick solidification under high pressure make a fine grain surface, which leads to having best wear and fatigue properties. Die aluminium castings are generally not given heat treatment, so they cannot be welded.
Permanent die aluminium casting is also known as gravity die casting and is suitable for large scale production. Their maximum weight is 10kg. But where heavy cost machinery and tools are used
the weight of casting may go up to 50kg. Permanent mold casting have low pouring rate but metal molds solidify quickly, mechanical properties of permanent mold castings may be further bettered by heat treatment.Sand aluminium casting is casting of a mold with sand. In normal sand casting, the mold is made around a design by forcing sand mixed along with a bonding agent on the design. Then the design is taken out which leaves a cavity for casting. Melted metal is poured into the mold and after its solidification the mold is broken to remove casting. The most normal bonding agent is a mix of clay and water. Good metal handling practice is needed for getting good castings.
Normally it uses plaster molds and throwaway designs of wax or other burnable materials. Plaster slurry is invested all round designs for many castings the designs are melted out as the plaster is baked. By this aluminium casting we can make precision parts, the aluminum parts can have walls as thin 0.40 to 0.75 mm. It is also used to make large number of parts of fine shapes which need no further machining.