Q. How can you implement chemically coated sand?
Chemically coated sand: Clean silica grains are sometimes coated with a non thermosetting hydrocarbon resin, which acts as a binder. An additional binder in the form of clay can also be used. The advantage of this sand is that the carbon in the resin which is an excellent refractory surrounds the sand grains and does not allow the molten metal to reach the sand grains. This produces casting with the clean surface as the sand does not get fused in them. The moisture content in the sand is kept to above 3%. Moulding sand exhibits maximum strength at a moisture content of 4% for lean sands and of 6 to 7% for loam sands.
Typical green moulding sand for gray iron moulding are given below: Silica sand = 68 to 86%
Clay = 10 to 20%
Water = 3 to 6%
Additives = 1 to 6%