Net shape steel and titanium castings
02 August 2011
Castings Technology International (Cti) has perfected the manufacture of castings from precision-machined polystyrene patterns. As in the Lost Wax process, layers of ceramic are built up on the pattern, which is removed on firing to leave an inert ceramic shell mould. These can be used to produce prototype Replicast castings and to meet a market need for short lead-time, one-off and low volume castings.
Further development has resulted in MEGAshell technology, which enables exceptionally large ceramic shell moulds to be produced to deliver the benefits of Replicast for one-off and low volume castings of a size and weight far greater than most casting manufacturers would have believed possible.
So far, ceramic moulds with dimensions up to 2 x 2 x 2m have been produced so that, for example, heavy section valve castings weighing several tonnes can be manufactured that are more than 20% lighter than the sand cast equivalent. Machining cost reductions of 50% or more can be achieved along with all the other benefits of the Replicast Process.
To date, more than 3,500 ceramic moulds have been manufactured via the MEGAshell process, proving its capability to meet the market demand for large, near net shape castings, especially in costly alloys of steel and nickel – and latterly, Cti has refined the technology so that it can be used for reactive alloys of titanium and zirconium.
Pictured: a 27% component weight saving was achieved with this 1.6 x 1.5 x 1.2m MEGAshell mould, into which 2 tonnes of ASTM A217 Grade C12A steel was poured.
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