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