MOULDING SAND COMPOSITION-
Main ingredients of moulding sand are silica grain (SiO2), Clay (binder) and moisture (to activate clay and provide plasticity)
(a) Silica sand- this is the major portion of the moulding sand. About 96% of this sand is silica grain. Rests are oxides (Al2O3), sodium (Na2O +K2O) and magnesium oxide (MgO +CaO). Main source of silica sand is river sand (with /without washing). Fusion point of sand is 14500C for cast iron and 15500C for steels. Grain size varies from micrometer to millimetre. The shape of the grains may be round, angular, sub angular or very angular.
(b) Zircon sand- The main composition is zirconium silicate (ZrSiO2).
Composition- ZrO2- 66.25%
SiO2-30.96%
Al2O3-1.92%
Fe2O3-0.74%
Other - oxides
It is very expensive. In India, it is available at quilon beach, kerela. The fusion point of the sand is 2400oC.
Advantage - High thermal conductivity
High chilling power
High density
Requires very small amount of binder (3%)
Use - Precision steel casting
Precision investment casting
(c) Chromite sand – The sand is crushed from the chrome ore. The fusion point of the sand is 18000C. It requires very small amount of binder (3%).
Composition- Cr2O3- 44%
Fe2O3 -28%
SiO2 -2.5%
CaO -0.5%
Al2O3 +MgO -25%
Use – heavy steel castings
Austenitic manganese steel castings
(d) Olivine sand- This sand composed of the minerals of fosterite (Mg2SiO4) and fayalite (Fe2SiO4). It is versatile in nature.
Main ingredients of moulding sand are silica grain (SiO2), Clay (binder) and moisture (to activate clay and provide plasticity)
(a) Silica sand- this is the major portion of the moulding sand. About 96% of this sand is silica grain. Rests are oxides (Al2O3), sodium (Na2O +K2O) and magnesium oxide (MgO +CaO). Main source of silica sand is river sand (with /without washing). Fusion point of sand is 14500C for cast iron and 15500C for steels. Grain size varies from micrometer to millimetre. The shape of the grains may be round, angular, sub angular or very angular.
(b) Zircon sand- The main composition is zirconium silicate (ZrSiO2).
Composition- ZrO2- 66.25%
SiO2-30.96%
Al2O3-1.92%
Fe2O3-0.74%
Other - oxides
It is very expensive. In India, it is available at quilon beach, kerela. The fusion point of the sand is 2400oC.
Advantage - High thermal conductivity
High chilling power
High density
Requires very small amount of binder (3%)
Use - Precision steel casting
Precision investment casting
(c) Chromite sand – The sand is crushed from the chrome ore. The fusion point of the sand is 18000C. It requires very small amount of binder (3%).
Composition- Cr2O3- 44%
Fe2O3 -28%
SiO2 -2.5%
CaO -0.5%
Al2O3 +MgO -25%
Use – heavy steel castings
Austenitic manganese steel castings
(d) Olivine sand- This sand composed of the minerals of fosterite (Mg2SiO4) and fayalite (Fe2SiO4). It is versatile in nature.
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