Introduction of Green Sand Casting
What is green sand casting?
Green sand casting is a common sand casting process using green
sand as the molding material. Green sand does not mean sand in
green color, but is a kind of wet quartz sand in the sense that
it is used in a wet environment.
The mold is made by ramming prepared sand around a pattern, held
in a flask. The patterns are withdrawn, leaving the mold cavity
into which metal will be poured. Molds are made in two halves,
an upper portion, the cope, and a lower portion, the drag. The
boundary between cope and drag is known as the parting line.
Cores, made from sand bonded with resins and baked to give
sufficient strength, may be supported within the mold cavity to
form the internal structure of hollow castings. Chills of
various designs may be embedded in the mold cavity wall to
control the solidification process.
Risers are reservoirs of molten metal used to ensure that all
regions of the casting are adequately fed until solidification
is complete. Risers also act as heat sources and thereby help
promote directional solidification. Molten metal is introduced
into the mold cavity through a sprue and distributed through a
system of gates and runners.
What are the materials of green sand casting?
Green sand casting is suitable for manufacturing various cast
iron castings, like ductile iron castings, gray iron castings.
It is also suitable for producing some simple aluminum castings.
As steel castings require larger air permeability, so it is not
workable for making steel castings.
Advantages of green sand castings
*Simple production process: Comparatively, the production
process of green sand casting is easier than other casting
*Low production cost: For its low material cost and simple
casting process, the production cost of green sand casting is
*High production rate: For the floor molding with green sand, we
could produce castings about 200 sand boxes each day. Now we are
also developing automatic molding production line, it could
produce green sand castings of 20t each day.
Disadvantages of green sand castings
*Defects are easy produced: With green sand casting process,
defects like sand residuals, sand holes, air holes and
shrinkages are common.
*Rough surface: As the simple production process, the surface of
green sand castings is rough. If iron foundry chooses fine green
sand, then the surface will be better, but the cost of fine
green sand is higher.
*Bad casting dimensions: The size tolerance of green sand
casting is CT11-CT12.So it is only suitable for castings with
low size accuracy.
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