CORE AND CORE MAKING

Cores are sand blocks they are used to make hollow portion in a casting. It is placed in a mould so that when molten metal is poured into the mould. This apart of mould will remain vacant i.e. the molten metal will not fill this part of the mould. So, when the mould is broken and the castings removed a hollow portion will result in the casting.

MATERIALS

• Water soluble binders (2 to 4% by weight)

• Oil binders (1-3% by weight)

• Pitch and resin binders (1-35 by weight)

BINDER

• organic or organic substance.

• clay acts as binder which may be Kaolinite, Ball Clay, Fire Clay, Limonite, Fuller’s earth and Bentonite.

• Binders included in the organic group are dextrin, molasses, cereal binders, linseed oil and resins likephenol formaldehyde, urea formaldehyde etc.

• Organic binders are mostly used for core making. Among all the above binders, the bentonite variety of clay is the most common.

• However, this clay alone cannot develop bonds among sand grins without the presence of moisture in moulding sand and core sand.