This set of Foundry Multiple Choice Questions & Answers (MCQs) focuses on “Types of Binders in the Moulding Sand, Types of Base Sand”.
1. _________________ binders are used for large dry sand cores.
a) Sulfate Binders
b) Pitch
c) Dextrin
d) Gelatinalized Starch
View Answer
Explanation: Sulfate Binders are compounds of wood sugars produced in paper pulp process. It is being used (up to 15%) in the large and dry sand cores as an ingredient of the Pitch as it contains the specified qualities required.
2. __________ is a binder that resists molten metal.
a) Coal tar
b) Core oil
c) Pitch
d) Chamotte
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Explanation: Pitch is a coal tar product. In the form of ground powder, the pitch may be added to up to 3% or more. With the presence of the molten metal around the core, pitch develops the hot strength to resist the molten metal.
3. ______________ contributes towards the baked strength of molding sand.
a) Natural Resin
b) Carbon
c) Olivine
d) Core Oil
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Explanation: The vegetable oils, mineral oils are regarded as the core oils. Their content in the sand varies from 0.5% to 3.0% by weight and hence they contribute to in increasing baked strength of molding sand.
4. __________ is an excellent water soluble binder.
a) Cereal Binder
b) Zircon
c) Dextrin
d) Silica Sand
View Answer
Explanation: Dextrin is a water soluble binder. The air hardens rapidly and resists core sagging during the handling. The increased moisture content develops the higher tensile strength, baked scratch and the edge hardness.
5. _________________ is used as the core coating medium.
a) Fire Clay
b) Plumbago
c) Bentonite
d) Cement
View Answer
Explanation: Just like mould coating, Core coating is also done. It is known as Core washing, dressing etc. Core Surfacing is done my Plumbago or Silica Flour. Plumbago is obtained from plants and imparts a good finishing. It is applied by dipping, spraying etc.
6. _________________ sands are best molding sands.
a) Refractory Sand
b) Loam Sand
c) Natural Sand
d) Synthetic Sand
View Answer
Explanation: Refractory Sands maintain their shape and other characteristics even at very high temperatures while they are in contact with the molten metals. Hence they are termed as the best molding sands.
7. __________ is refractory sand that can be molded to intricate shape.
a) Quartz
b) Olivine
c) Bentonite
d) Clays
View Answer
Explanation: Olivine is refractory sand. When packed as the mold cavity, they remain sufficiently porous or permeable to give vents to the mould gases to escape out. Hence they are chemically immune and can be molded in intricate shapes.
8. Which of the following cannot be used repeatedly for making moulds?
a) Sillimanite
b) Dolomite
c) Natural Sand
d) Silica Sand
View Answer
Explanation: The Natural Sands are to be used for making moulds as soon as it is received from the source. The content of the binding particles is less which makes it unsuitable for the making of moulds which are needed repeatedly.
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