CO2 Molding Process

8/18/2019 CO2 Molding Process

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CO2

Molding Process


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CO2 Molding Process

• The Mold for Co2 Casting is made ofa mixture of sand and liquid silicatebinder

• Which is hardened by passing Co2gas over the mold.

• Carbon dioxide molding deliver greataccuracy in production.


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CO2-Sodium Silicate Casting

• ind of !and casting process – "imensionally accurate castings #ith $ne surface $nish

– Process is not economical than green sand casting

process

– %ts rapid mold hardening

– Moisture is completely eliminated from the moldingsand

– &ood surface $nish

– Thin section casting

– 'ard mold

– (ess machining

– 'igh production run


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Mold• The material for ma)ing the mold

– Clean dry silica sand

• The binder used is sodium silicate liquid*+a2!iO,- about , to /.

• That mold receive its strength from theaddition of sodium silicate0

• 1 liquid inorganic binder that is also )no#nas #ater glass and become harder by o#of carbon die oxide gas.

• CO2 is blo#n into the mold or core at a

pressure of around 23 psi0 #hich hardensthe mold.


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1pplications

• The modi$cation of CO2 process can be

used

• Where speed and exibility is the prime

requirement.

• When certain portions of a mold requirehigh strength0 better accuracy0 thinner

sections or deep dra#s.• Molds and cores of a varied si4es and

shapes can be molded by this process.


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CO2-Sodium Silicate Casting• Cylinder

• %mpellers5 a rotating device used to force a uidin a desired direction under pressure

• 1gricultural machines6 lifting machines6 grindingmachines6 medical machines0 automobile cars0

etc


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• !ome sodium silicate bonding agentpermit self7setting action #ithoutCO2.

• !pecial carbonaceous sands or seacoal improves sha)eout *The act ofremoving castings from the sandmold -.

• %t also reduces ollution.


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• !ilicate bonded sands can be sha)en outrelatively easily by mixing additives inthem to enhance the collapsibility of

sodium silicate mold.• !ugar is used up to 82/ as a brea)do#n

agent so the core deteriorates fully aftersolidi$cation of mold.

• The molding sand can be reused byadding ,3/ ne# sand.


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Procedure:• The mold is prepared from this mixture by

– !tandard molding machines – Core blo#ers – 9y hand

• 1fter the mold has been prepared #ith therequired cavity.

• 9efore removing the molding :ac)et – CO2 gas)et is $tted on top of the as) or a

hood is placed on top of larger molds – CO2 is blo#n into the mold.


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• !odium !ilicate binder reacts #ith the CO2 to form silica gel0 #hich gives it a strongand smooth surface.

• The reaction is as follo#5

+a2!iO, ; CO2 !iO2 ; +a2CO,

• This silica gel acts as cement to bond sandgrains together.

• %n some case0 CO2 molding has been used

together #ith 4ircon sand to give superior$nish and to ma)e permenent molds or


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• CO2 must be blo#n uniformly through thesand body #ith pattern to harden thecontact area.

• !mall tubes and vented pattern facilitatethis process.

• The time of CO2 blo#ing is 8< to ,3s.

• !and mixed #ith sodium silicate is pac)ed

around a metal pattern to a depth of about8 in follo#ed by regular molding sand.


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"isadvantages

• The hardened sand has poorcollapsibility0 so creates sha)eoutand core removal di=culty and the

additives are generally to enhancethe collapsibility.

• Care must be ta)en to prevent thecarbon dioxide in air from hardeningthe sand before the mold ma)ingprocess is complete.

• %t is more expensive than the othersand methods0 and harder to sha)e

Documents

CO2 Molding Process