US 6,551,396 B1 · Phosphate investment compositions

Abstract

An investment composition is described for use in investment casting (also called lost wax casting). The composition is a phosphate bonded material that contains mono-ammonium phosphate (MAP), magnesium oxide and silica filler (quartz, cristobalite, or a mixture thereof). It has been discovered that controlling the amount and ratio of these components has a significant impact on gas permeability (porosity), set time, cast smoothness and cast softness. The most outstanding feature of the new investments is the short mold fabrication and processing time that they allow due to their high gas permeability. The investments can be placed in a bum out furnace while still wet and can be heated rapidly to the firing temperature. The casts can be broken by sandblasting the casts with glass beads. Molds made from the casts have smooth surfaces indicating that the casts are free of visible inclusions and other defects.

Claims10

Dependent claims

An investment composition consisting essentially of the following components in the following amounts:

(a) mono-ammonium phosphate in an amount ranging from 10% w/w to 17% w/w;
(b) magnesium oxide in an amount ranging from 7% w/w to 15% w/w;
and
(c) silica filler in an amount ranging from 72% w/w to 80% w/w,
wherein 15-25% of the silica filler has a size of over 45 microns and 0.0-0.2% of the silica filler has a size of over 212 microns.

2 more elements

Dependencies are inferred from the claim text.

Phosphate investment compositions

Life of this patent

Phosphate investment compositions

Life of this patent

Abstract

Claims10