Special casting Techniques

Shell Casting

Shell casting

• Metal pattern is maintained at 300 -400 c• Pattern is sprayed with lubricating agent

(silicon) to prevent sticking • Dump box contain sand resin mixture (phenol

formaldehyde 4-5 kg of each 100 kg of sand)

Ceramic mould

• Ceramic slurry is prepared by mixing fine grained refractory powders of zircon (ZrSiO4) alumina ( Al2O3), fused silica (SiO2)

• This slury is applied over the pattern surfaces to form a thin coating

• After applying coating baked in fire clay • Pattern is removed out from the mould and

further heating of the mould is done for about 1000 C. Metal is poured to produce castings.

Investment casting, Lost wax pattern

(c)InvestingA specially formulated slurry is poured and allowed to

hardened for 8 hours through drying d) Heating – wax melts leaving the cavity After that the mould cavity is used for pouring metal.

CO2 Moulding

Hardening the sand mould by gassing with CO2

CO2 at a pressure 1.5kg/cm2 is diffused to initiate hardening reaction CO2 (produces) carbonic acid forms colloidal gel Hardens and forms a bond between sand grains.Na2SiO3 + CO2 Na2CO3 +SiO2Sod. Silicate Silica gel

Cupola furnace