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MOULDING SAND

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MOULDING SAND 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 – PowerPoint PPT presentation

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Title: MOULDING SAND


1
MOULDING SAND
  • 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
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  • 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 1.5moisture 3 to 3.5
  • (2) New 15 Old 84
  • bentonite and moisture 0.5 each

NITC
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  • DRY SAND- for moulding large castings. Moulds of
    green sand dried and baked with venting done.
    Add- cow 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
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  • 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 CO2 sand, Shell sand,
    etc for special applications
  • Mould washers- slurry of fine ceramic grains
    applied on mould surface to minimize fusing

NITC
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About MOULDING SAND
  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
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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.
8
MOULDING SAND- PROPERTIES
  • Green Strength- Adequate strength after mixing,
    and plasticity for handling
  • Dry Strength- After pouring molten metal,
    adjacent surface loses water content. Dries. Dry
    sand must have enough strength to resist erosion
  • Hot Strength- Strength at elevated temperature
    after evaporation of moisture
  • Permeability- Permeable or porous to permit gases
    to escape. Ability of sand moulds to allow the
    escape of gases

NITC
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  • Thermal stability- Rapid expansion of sand
    surface at mould-metal interface. May crack.
    Results in defect called SCAB
  • Refractoriness- Ability of sand to withstand high
    temperature
  • Flowability- Ability to flow fill narrow
    portions around pattern
  • Surface finish- Ability to produce good surface
    finish in casting
  • Collapsibility- Allow easy removal of casting
    from mould
  • Reclamation- Should be reusable and reclaimable

NITC
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FURNACES
  • 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 (gt 50 T, VERTICAL, HIGH RATES)
  • ELECTRIC FURNACES
  • INDUCTION FURNACES

NITC
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FOUNDRIES
  • From Latin word- fundere (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
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  • CRUCIBLE FURNACE

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OIL FIRED FURNACE
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CUPOLA CHARGE PASSES
DOWNWARDS UNDER GRAVITY MEETS FLOW OF HOT GASES
MOVING UPWARDS CONTINUOUS IN OPERATION.Vertica
l 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.
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TOWER FURNACETO MELT ALUMINIUM alloys3 main
sections- charging elevator, melting unit,
holding furnace (Cylindrical rotary unit).
Automatic controlsGrate above burners
supports solid chargeMolten charge runs down
25
REVERBERATORY
FURNACE Small units (50kg) for melting non
ferrous metals, large (about 25T) 10 T capacity
to melt iron AIR FURNACEOne 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
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TYPICAL DIRECT ARC FURNACE
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A TYPICAL DIRECT
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