Casting
By: Jackie Ho
Casting
 The process of which a material is
introduced into a mold in liquid state, and
is allowed to solidify inside the mold,
creating a fabricated part
Sand Casting
 Cavity formed by pattern made by wood
or metal
 Require a riser since molten metal
shrinks as it solidify
Material used in sand casting:
low temperature steel, Al, Mg, and Ni alloy
Riser is used to account for the shrinkage of the
molten metal when it solidifies. The function of
riser is just to feed molten metal into the void
where shrinkage occurs.
Permanent mold casting
Mold:
 Takes weeks to prepare
 is made out of cast iron
 is preheated to 200°C before pouring
 expand during the pour
 cavity is bigger than desired dimensions
Material used in permanent mold casting:
Fe, Al, Mg, Cu based alloys
Die casting
 Similar to permanent mold casting
(difference is high pressure is used in this type of casting)
 Mold cavity can be very precise
 Very technical and a great deal of skill is
required to create the die
Metal used in die casting:
non-Fe, Al, Mg, Zn, Cu based alloys
Centrifugal casting
 Has a spinning chamber at 300-3000rpm
 Spinning while molten metal is poured in
 Molten metal is thrown to the side where it
solidifies
 Parts produced have fine grained outer surface
and impurities in the inner diameter
Material used in centrifugal casting:
Fe, steel, stainless steel, and alloys of Al, Cu, Ni
Advantages
 Sand casting
 Produce large part
 Can be recycled
 Preparation time for sand mold is fast
 Permanent mold casting
 Fast production rate
 Lower cost production per unit
Advantages (cont.)
 Die casting
 Good for mass production
 Lifetime production of up to 500,000
castings
 Very fast production rate
 Centrifugal casting
 Very fine-grained outer surface
 Resistance to atmospheric corrosion
Disadvantages
 Sand Casting
 Limited quantities can be produced
 Metal wasted in the riser
 Permanent mold casting
 Molds take up storage space
 Die casting
 Require a long time to prepare the die
 Centrifugal casting
 Is only good for producing cylindrical parts