Types Of Moulding Sands | Core Sand | Parting Sand

Classification of moulding sands


According to their use in the foundry, moulding sands are classified into following categories:



1. Green sand:

  • It is sand used in the wet condition for making the mould. It is mixture of silica sand with 15-25 per cent clay and 6-8 per cent water

  • As explained earlier green sand moulds are not dried and metal is poured in them in the wet condition

  • Being damp the sand can be easily worked with hand to give it any desired shape

  • This sand is used for producing small to medium sized moulds which are not very complex

01-green sand-silica sand-green sand moulds



2. Dry sand:

  • Dry sand is the green sand that has been dried or baked after preparing the mould.

  • Drying sand gives strength to the mould so that it can be used for larger castings

01-baked sand-dry sand



3. Loam sand:


  • Loam sand is sand containing up to 50 % clay which has been worked to the consistency of builder mortar.

  • This sand is used for loam sand moulds for making very heavy castings usually with the help of sweeps and skeleton patterns.

01-loam sand-with 50% clay



4. Parting sand:


  • This sand is used during making of the mould to ensure that green sand does not stick to the pattern and the cope and drug parts can be easily separated for removing the pattern without causing any damage to the mould.

  • Parting sand consists of fine grained clay free dried silica sand, sea sand or burnt sand with some parting compounds.

  • The parting compounds used include charcoal, ground bone and limestone, groundnut shells, talc and calcium phosphate.

01-parting sand-dried silica sand-powder sand


5. Facing sand:


  • Facing sand is the sand which covers the pattern all around it. The remaining box is filled with ordinary floor sand.

  • Facing sand forms the face of the mould and comes in direct contact with the molten metal when it is poured.

  • High strength and refractoriness are required for this sand.

  • It is made of silica sand and clay without the addition of any used sand.

  • Graphite, mollases, plumbago etc. may be added to the facing sand. Thickness of the sand layer varies from 20 to 30 mm.

01-facing sand-silica sand with clay



6. Backing sand:


  • Backing sand is the bulk of the sand used to back up the facing sand and to fill up the volume of the flask.

  • It consists mainly of old, repeatedly used moulding sand which is generally black in colour due to addition of coal dust and burning on contact with hot metal.

  • Because of the colour backing sand is also sometimes called black sand.

  • The main purpose for the use of backing sand is to reduce the cost of moulding.

01-gate cutter-mold cavity cutter-mould tool


7. System sand:


  • This is the sand used in mechanized foundries for filling the entire flask.

  • No separate facing sand in used in a mechanized foundry.

  • Sand, cleaned and reactivated by the addition of water and binders is used to fill the flask. Because of the absence of any fresh sand, system sand must have more strength, permeability and refractoriness compared to backing sand.

01-system sand-used sand-sand after casting process over


8. Core sand:
  • Core sand is the sand used for making cores. This is silica sand mixed with core oil. That is why it is also called oil sand.

  • The core oil consists of linseed oil, resin, light mineral oil with some binders.

  • For larger cores, sometimes pitch or flour and water may also be used to save on cost.

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Hi, I`m Sostenes, Electrical Technician and PLC`S Programmer.
Everyday I`m exploring the world of Electrical to find better solution for Automation. I believe everyday can become a Electrician with the right learning materials.
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