• Granular particles from the breakdown of rocks by frost, wind, heat and water currents
• Complex Composition in different places
• At bottom and banks of rivers
•
- mainly silica (86 to 90%); Alumina (4% to 8 %);
Iron oxide (2 to 5%) with oxides of Ti, Mn, Ca. etc .
NITC

NATURAL SAND , called Green sand. Only water as binder; can maintain water for long time
SYNTHETIC SAND .( 1)GREEN and (2)DRY types
(1) Artificial sand by mixing clay free sand, binder(water and bentonite)
Contains New silica sand 25%; Old sand 70%; bentonite 1.5%;moisture 3% to 3.5%
NITC

DRY SAND - for moulding large castings. Moulds of green sand dried and baked with venting done. Addcow dung, horse manure etc.
LOAM SAND - mixture of clay and sand milled with water to thin plastic paste. Mould made on soft bricks.
The mould dried very slowly before cast. For large regular shapes- drums, chemical pans etc.
FACING SAND - used directly with surface of pattern; comes in contact with molten metal; must have high strength, refractoriness.
Silica sand and clay without used sand- plumbago powder, Ceylon lead, or graphite used. Layer of 20 to
30 mm thick--about 10% to 15% of whole mould sand
NITC

BACKING SAND - old used moulding sand called floor sand black in colour. Used to fill mould at back of facing layer. Weak in bonding strength
SYSTEM SAND - used in machine moulding to fill whole of flask. Strength, premealibility and refractoriness high
PARTING SAND - used for separating boxes from adhering, free from clay
CORE SAND - for making cores. Silica sand with core oil
(linseed oil, rosin, light mineral oil, binders etc)
SPECIALISED SANDS - like CO
2 for special applications sand, Shell sand, etc
Mould washers - slurry of fine ceramic grains applied on mould surface to minimize fusing
NITC

1.
NATURAL SAND
2.
SYNTHETIC SAND.- GREEN and DRY
3.
DRY SAND
4.
LOAM SAND
5.
FACING SAND
6.
BACKING SAND
7.
SYSTEM SAND
8.
PARTING SAND
9.
CORE SAND
10. SPECIALISED SANDS
11. Mould washers
NITC

ADV - Acid Demand Value
Defined as the property of a sand or additive to affect the cure process as a function of the materials acidity or basicity on the pH scale.

•
Green StrengthAdequate strength after mixing, and plasticity for handling
•
Dry StrengthAfter pouring molten metal, adjacent surface loses water content. Dries. Dry sand must have enough strength to resist erosion
•
Hot StrengthStrength at elevated temperature after evaporation of moisture
•
PermeabilityPermeable or porous to permit gases to escape.
Ability of sand moulds to allow the escape of gases
NITC

• Thermal stabilityRapid expansion of sand surface at mould-metal interface. May crack. Results in defect called
SCAB
•
RefractorinessAbility of sand to withstand high temperature
•
FlowabilityAbility to flow & fill narrow portions around pattern
• Surface finishAbility to produce good surface finish in casting
•
CollapsibilityAllow easy removal of casting from mould
• ReclamationShould be reusable and reclaimable
NITC

Proper selection depends on:
• Composition and melting point of alloy to be cast
• Control of atmospheric contamination
• Capacity and rate of melting required
• Environmental considerations- noise, pollution
• Power supply, availability, cost of fuels
• Economic considerations-initial cost, operating cost, maintenance cost etc.
CUPOLAS (> 50 T, VERTICAL, HIGH RATES )
ELECTRIC FURNACES
INDUCTION FURNACES
NITC

(meaning melting & pouring)
• Pattern & Mould making- automated, computer integrated facilities- CAD/CAM
• Melting, controlling composition & impurities, pouring-
Use of conveyors, automated handling, shakeout, cleaning, heat treatment, inspection, etc.
NITC

CUPOLA
* CHARGE PASSES DOWNWARDS
UNDER GRAVITY
* MEETS FLOW OF HOT GASES
MOVING UPWARDS
* CONTINUOUS IN OPERATION
.Vertical steel shell, lined with fire bricks.
.Base on four steel columns
.Hinged doors in the base plate to remove residue at the end of melt.
.Air blast through tuyeres (number on size)
.Through charging door, coke, pig iron, scrap & lime stone charged.
.Cold & Hot blast cupolas.

TOWER FURNACE
TO MELT ALUMINIUM
& alloys
3 main sectionscharging elevator, melting unit, holding furnace (Cylindrical rotary unit).
Automatic controls
Grate above burners supports solid charge
Molten charge runs down

REVERBERATORY FURNACE
Small units (50kg) for melting non ferrous metals, large (about 25T)
10 T capacity to melt iron
AIR FURNACE:
One type of RB- to melt cast iron for roll mill rolls, malleable castings,
15 T capacity – Charge out of contact with fuel, less sulphur absorbed, long melting time enables control of composition, large size scrap handled.
Lump coal, pulverised fuel, oil used to fire. Solid coal burnt in a grate