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8/8/2019 Sand Additives & Binders
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SAND ADDITIVES &BINDERSSARTHAK KATYAL
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Index
Sand Binders
1) Organic Binders
1) Dextrins
2) Molasses
3) Cereal Binders
4) Linseed Oil
5) Resins
2) Inorganic Binders1) Clay Binders
2) Portland Cement
3) Sodium Silicate
Sand Additives
1) Sea Coal
2) Silica Flour
3) Wood Flour
4) Iron Oxide
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Sand Binders
There are two types of Sand Binders:
1) Organic Sand Binders
2) Inorganic Sand Binders
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Organic Sand Binders
1) Dextrin
2) Molasses
3) Cereal Binders4) Linseed Oil
5) Resins
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Dextrins
Dextrin's are produced by
the hydrolysis of starchor glycogen
Dextrin's are white, yellow or brown powdersthat are partially or fully water-soluble,yielding optically active solutions of
low viscosity.
Used as Sand Binding in Green Sand Mould
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Molasses
A thick syrup produced in refining raw sugarand ranging from light to dark brown in colour.
Cane molasses, unrefined and containing 60 to
70 per cent sugar solids, may be used forincreases dry strength of the sand and edgehardness of moulds. Dextrin's may be used forthe same purpose
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Cereal Binders
It acts as binder and is finely ground corn
flour or gelatinized and ground starch from
corn. Cereals may be used in moulding sandsfor increased green or dry strength or
collapsibility in amounts up to 2 percent.
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Linseed Oil
Linseed Oil is one of the most traditional
material used in foundary binder for sand
cores. It belongs to the group classified as Drying Oil
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Resins
Urea-formaldehyde, also known as urea-
methanal is a non-
transparent th
ermosetting resin or plastic,made from urea and formaldehyde heated in
the presence of a mild base such
as ammonia or pyridine.These resins are used
in adhesives, finishes, MDF, and mouldedobjects.
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Inorganic Sand Binders
Clay Binders
Portland Cement
Sodium Silicate
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Clay Binders
Moulding sands may contain about 2 to 50
per cent of clay. With suitable water content,
it is th
e principal source of th
e strength
andplasticity of the moulding sand. Clay is thus
the bond or binder of moulding sands.
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Portland Cement
Portland cement (often referred to as OPC,from Ordinary Portland Cement) is the mostcommon type of cement in general usearound the world because it is a basicingredient of concrete, mortar. It is afine powder produced by grinding Portlandcement clinker (more than 90%), a limited
amount of calcium sulphate (which controlsthe set time) and up to 5% minorconstituents.
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Sodium Silicate
Sodium silicate is the common namefor a compound sodium metasilicate,
Na2SiO3. It is available in aqueous
solution. Sodium carbonate and silicondioxide react when molten to formsodium silicate and carbon dioxide:
Na2CO3 + SiO2Na2SiO3 + CO2
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Sand
Additives
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Types Of Sand Additives
Sea coal
Silica Flour
Wood Flour(Cellulose Material) Iron Oxide
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Sea Coal
It is a finely ground soft coal used in moulding
sand for cast irons, principally for the purpose
of improving th
e surface finish
and ease ofcleaning the castings. It is usually ground to
fineness similar to that of the moulding sand
in which it is used. Percentages employed in
sands are about 2 to 8 percent.
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Silica Flour
Pulverized silica, finer than 200 mesh, is
called silica flour. It may be used in amounts
up to 35 percent forth
e purpose of increasinghot strength of the sand. It also increases the
density of the sand for resistingmetal
penetration.
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Wood Flour
Ground wood flour or other cellulose
materials such as cob-flour, cereal hulls, and
carbonized cellulose may be added inamounts of 1 to 2 per cent to the weight of
the moulding sands.They may function to
control the expansion of the sand by burning
out at elevated temperature.They canimprove collapsibility and flow ability of the
sand.
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Iron Oxide
Fine iron oxide is used in small percentage in
some sands to obtain added hot strength
Aid to thermal transfer ofheat from themould-metal interfaceand provides stabilityto the moulds dimensional properties
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The End
Thank You