Investment powder
AssigneeGoodwin PLC
InventorsSimon Robert GOODWIN, Michael Gerard PALIN
Life of this patent
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Abstract
An investment powder which is safer than conventional powders comprising tricalcium phosphate, and being substantially or entirely free of free silica in the respiratory portion yet providing an overall expansion at 750° C. of 1% or higher sufficient to prevent mould cracking during casting. A method of making a casting comprising forming a slurry by mixing a gypsum bonded investment powder with water, pouring the slurry into a stainless steel flask around a low melting point material model, allowing the slurry to set to define a mould, heating the mould to burn out the model and casting material into the mould wherein the stainless steel flask consists of a 400 series martensitic stainless steel.
Claims24
A gypsum bonded investment powder comprising tricalcium phosphate, and containing less than 1% by weight free silica in the respiratory fraction.
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Use of a composition as an investment powder, said composition comprising
- 10 to 30% plaster
- 25 to 75% tricalcium phosphate
- 10 to 65% magnesium oxide
- 0 to 25% of one or more low silica minerals
- 0 to 10% additives
A method of making a casting comprising forming a slurry by mixing a gypsum bonded investment powder with water, pouring the slurry into a stainless steel flask around a low melting point material model, allowing the slurry to set to define a mould, heating the mould to burn out the model and casting material into the mould wherein the stainless steel flask consists of a 400 series martensitic stainless steel.
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Dependencies are inferred from the claim text.