Claims
- 1. A method of manufacture of a ceramic shell mold comprising,applying a coating of a prime coat slurry comprising refractory material and a colloidal silica sol onto an expendable pattern of thermoplastic material to produce a prime coated preform, drying said prime coated preform, applying at least one coating of a refractory back-up coat slurry comprising refractory material and a colloidal silica sol binder onto said prime coated preform to produce a refractory back-up coated preform, drying said refractory back-up coated preform, removing said thermoplastic pattern from said refractory backup coated preform to produce a green shell mold, wherein in at least one of said prime coat slurry and said refractory back-up coat slurry said colloidal sol is a blend of a large particle size aqueous colloidal silica sol having an average particle size of about 40 nanometer, a small particle size aqueous colloidal silica sol having an average particle size of about 8 nanometer, and potassium silicate.
- 2. The method of claim 1 further comprising applying stucco material to at least one of said prime coated preform or refractory back-up coated preform prior to drying of said prime coated preform or refractory back-up coated preform.
- 3. The method of claim 2 wherein said large particle size aqueous colloidal silica sol having an average particle size of about 40 nanometer is present in an amount of about 10% to about 87% by weight of said blend, and the potassium silicate is present in an amount of about 3% to about 8% by weight of said blend, and the small particle size aqueous colloidal silica sol having an average particle size of about 8 nanometer is present in an amount of about 5% to about 87% by weight of said blend.
- 4. The method of claim 1, wherein said large particle size aqueous colloidal silica sol has a solids content of about 40% to about 50%.
- 5. The method of claim 1 wherein the silica sol has a basic pH.
- 6. The method of claim 1 wherein the large particle size sol and the small particle size sol are present in a ratio of 87 to 5.
- 7. The method of claim 1 wherein the large particle size sol, the small particle size sol, and the potassium silicate are present in a ratio of 87 to 5 to 8 respectively.
- 8. A ceramic shell mold made by applying a coating of a prime coat slurry comprising refractory material and a colloidal silica sol onto an expendable pattern of thermoplastic material to produce a prime coated preform,drying said prime coated preform, applying at least one coating of a refractory back-up coat slurry comprising refractory material and a colloidal silica sol binder onto said prime coated preform to produce a refractory back-up coated preform, drying said refractory back-up coated preform, removing said thermoplastic pattern from said refractory backup coated preform to produce a green shell mold, wherein in at least one of said prime coat slurry and said refractory back-up coat slurry said colloidal sol is a blend of a large particle size aqueous colloidal silica sol having an average particle size of about 40 nanometer, a small particle size aqueous colloidal silica sol having an average particle size of about 8 nanometer, and potassium silicate, and applying stucco material to at least one of said prime coated preform or refractory back-up coated preform prior to drying of said prime coated preform or refractory back-up coated preform.
- 9. The mold of claim 8 wherein the silica sol has a basic pH.
Parent Case Info
This application is a continuation of application U.S. Ser. No. 09/105,782 filed Jun. 26, 1998, now U.S. Pat. No. 6,000,457. This Application also claims benefit to provisional Application 60/074,366 Feb. 11, 1998.
US Referenced Citations (8)
Foreign Referenced Citations (1)
Number |
Date |
Country |
207 864 |
Jan 1987 |
EP |
Non-Patent Literature Citations (1)
Entry |
Rusher, Strength Factors of Ceramic Shell Molds, Cast Metals Research Journal, vol. 10, No. 4, Dec. 1974. |
Provisional Applications (1)
|
Number |
Date |
Country |
|
60/074366 |
Feb 1998 |
US |
Continuations (1)
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Number |
Date |
Country |
Parent |
09/105782 |
Jun 1998 |
US |
Child |
09/447782 |
|
US |