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Manufacture Lec.7

The document summarizes metal casting processes and sand casting. It discusses two trends impacting the casting industry: increasing mechanization/automation and demand for high quality castings. It classifies molds as expendable, permanent, or composite and describes sand casting steps. Key sand casting components include the cope and drag pieces, pouring basin, sprue, runner system, riser, and cores/vents.

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38 views7 pages

Manufacture Lec.7

The document summarizes metal casting processes and sand casting. It discusses two trends impacting the casting industry: increasing mechanization/automation and demand for high quality castings. It classifies molds as expendable, permanent, or composite and describes sand casting steps. Key sand casting components include the cope and drag pieces, pouring basin, sprue, runner system, riser, and cores/vents.

Uploaded by

Mhamed
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOCX, PDF, TXT or read online on Scribd
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Chapter 11

Metal- casting processes


Two trends are currently having major impact on casting industry:

A. Continuing mechanization and automation.


B. Increasing demand for high quality casting.

Molds classified as following:

1) Expendable molds
2) Permanent mold
3) Composite molds

Expendable molds Permanent mold

Composite molds
Sand casting
Sand casting consists of the following steps:

a. Placing a pattern.
b. Incorporating a gating system.
c. Filling the resulting cavity with molten metal.
d. Allowing the metal to cool until solidify.
e. Breaking a way the sand mold.
f. Removing the casting.

Fig 11.5 outline of production steps in atypical sand – casting operation


Sands
Sands (Sio2) use in casting mold

Naturally bonded (bank sand)


Sands
Synthetic (lake sand)

The sands have fine round grains closely packed and form
a smooth mold surface mold strength, but it has low
permeability.

Fig. Effect of shape and size of sands on casting products

The mold should have good collapsibility to allow for casting to shrink
while cooling avoiding defects in the casting (hot tearing cracking).
Clay

Zircon

Sands additives Olivine

(Mulling machines)

Iron silicate

Chromite

Types of sand molds

 Green molding sand, which are mixture of


a. Sand
b. Clay
c. Water
 Cold box mold, process varies organic and inorganic binders are
blended into the sand to bond the grains chemically for greater
strength.
 No-bake mold process, synthetic liquid resin is mixed
The following are the major components of the sand mold:

1. The mold consists of two pieces, cope on the top and drag on the
bottom.
2. Pouring basin or pouring cup, into which molten metal is
poured.
3. Sprue, through which the molten metal flows downward.
4. Runner system, which has channels that carry the molten metal
from the sprue to the mold cavity.
5. Riser, which supply additional metal to the casting as it shrinks
during solidification.

Fig. Possible types and positions for risers in sand casting


6. Cores, which are inserts made from sand, they are placed in the
mold for hollow regions.
7- Vents, which are placed in the molds to carry out the gases produced
when molten.

Video
How it is made alloy wheels

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