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Mouldind Sand.pptx

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Molding sand is a mixture of silica sand, clay, and water that is used to create molds for metal casting. The most common type is green sand, which contains 15-25% clay and 6-8% water. Green sand molds are not dried before pouring metal. Dry sand has been baked after forming the mold to increase strength for larger castings. Loam sand contains up to 50% clay for very heavy castings. Parting, facing, and backing sands all serve different purposes in the mold assembly, with facing sand contacting the molten metal and requiring high strength and refractory properties. Core sand is mixed with core oil or other binders to form cores inserted into molds.

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MOLDING SAND Molding sand are the most commonly used for making all types of molds irrespective of whether they are used for producing casting of ferrous or non-ferrous metal Most sand casting operations are used silica sand. Sand used to manufacture a mould for casting process is held by mixture of water and clay. A typical mixture by volume could be 89% sand,4% water and 7% clay.
CHARACTERISTIC OF MOLDING SAND Molding sands are refractory in nature and can withstand temperature of metal being poured without fusing. The molding sand do not chemically react with molten metal. The sand have high degree of permeability and thus allow gases formed during pouring to escape. These strength , permeability and hardness of the sand mix can be varied by changing the structure of sand .
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
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
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
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 drag 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.
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, mollasses etc. may be added to the facing sand. Thickness of the sand layer varies from 20 to 30 mm
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 molding sand which is generally black in color due to addition of coal dust and burning on contact with hot metal. Because of the color backing sand is also sometimes called black sand. The main purpose for the use of backing sand is to reduce the cost of molding.
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.
Mouldind Sand.pptx
Mouldind Sand.pptx
Mouldind Sand.pptx
Mouldind Sand.pptx

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Mouldind Sand.pptx

  • 1. MOLDING SAND Molding sand are the most commonly used for making all types of molds irrespective of whether they are used for producing casting of ferrous or non-ferrous metal Most sand casting operations are used silica sand. Sand used to manufacture a mould for casting process is held by mixture of water and clay. A typical mixture by volume could be 89% sand,4% water and 7% clay.
  • 2. CHARACTERISTIC OF MOLDING SAND Molding sands are refractory in nature and can withstand temperature of metal being poured without fusing. The molding sand do not chemically react with molten metal. The sand have high degree of permeability and thus allow gases formed during pouring to escape. These strength , permeability and hardness of the sand mix can be varied by changing the structure of sand .
  • 3. 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
  • 4. 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
  • 5. 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
  • 6. 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 drag 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.
  • 7. 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, mollasses etc. may be added to the facing sand. Thickness of the sand layer varies from 20 to 30 mm
  • 8. 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 molding sand which is generally black in color due to addition of coal dust and burning on contact with hot metal. Because of the color backing sand is also sometimes called black sand. The main purpose for the use of backing sand is to reduce the cost of molding.
  • 9. 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.