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INVESTMENT CASTING
 

Speciality Powders for the Cast Metal Investment Casting Industry

The term investment casting derives from the characteristic use of mobile ceramic slurries, or ‘investments’, to form moulds with extremely smooth surfaces. These are replicated from precise patterns and transmitted in turn to the castings. Although certain variants employ permanent patterns and multi-part moulds analogous to those used in sand casting, investment casting has become closely identified with the expendable pattern principle typified in the long-established lost wax process. In brief, disposable replicas of the required casting are formed by injecting molten wax into a die with the appropriately shaped cavity. The wax patterns are connected, singly or in groups, to a wax sprue and gating system and the whole is clothed in investment slurry. The wax is melted out and the investment consolidated by heating, leaving a hard ceramic mould to receive the molten metal. The mould is finally broken up to extract the solidified metal product.
 

Turbine engine components such as blades and vanes constitute the biggest single market for investment castings; nevertheless, there are a very great diversity of other applications.

 

In many cases, the choice of the investment casting route is dictated by technical considerations – property requirements, design complexity – but in more and more cases the process is being selected because if offers the cheapest manufacturing option in terms of total costs.

 
* Aerospace
* Power generation (land based gas turbines)
* Automotive products
* Food processing
* Fighting vehicles
* Petrochemical equipment
* Field guns
* Computers
* Automatic weapons
* Pumps
* Rifles/sporting guns
* Safety equipment
* Missiles
* Yachting chandlery
* Rocketry
* Bicycle parts
* Satellites
* Roulette Wheels
* Hovercraft
* Equestrian products
* Medical implants
* Artwork
* Medical instruments
* Golf clubs
* Orthopaedic appliances
* Musical instruments
* Nuclear power
* Cigarette making machinery

Minchem HMP Ltd has developed products in our ZircozonTM range that give additional strengths and benefits to the processes involved in the Cast Metal Investment Casting Industry. For full details please contact the office.

 
Zircozon 200M – multimodal zircon powder
Zircozon 300M – multimodal zircon powder
Zircozon Granular M170 – calcined zircon sand
 
 
Fused Silica
 

Fused Silica is an amorphous siliceous glass produced by high temperature fusion of high quality crystalline silica (quartz). The fusion produces a substance characterised by very low thermal expansion and a high resistance to temperature and thermal shock.

 

Fused Silica is employed in a variety of industrial applications including foundry (investment casting slurry and stucco, and mould release agent), refractory and ceramic (crucibles, saggars, rollers, pouring cups, ceramic cores, gas fire radiants and items for steel, non-ferrous metal and glass industries), and filler (electronic and adhesive).

Typical Chemical Composition

Silica
Si02
99.8%
Alumina
Al203
0.2%
Iron
Fe203
0.01%
Titania
Ti02
0.003%
Density:
 2.17g/cm3
min
 
Available Sizes:
 
-150 mesh powder (100 microns)  – D50 - 50
-200 mesh powder (75 microns)     – D50 - 35
-300 mesh powder (53 microns)     – D50 - 30
-325 mesh powder (45 microns)     – D50 – 20
 
Fused Alumina
 

Fusing aluminous raw materials electrically in an electric arc furnace can produce fused alumina. The fused product is then cooled into ingots, crushed and then classified. There are two types of fused alumina – white and brown.

 

White Fused Alumina is formed from calcined alumina. The only impurity in fused alumina is sodium, which is present in the form of alpha-alumina. Fused alumina, with its perfect crystallisation is difficult to sinter. It is inactive and does not readily react with other raw materials. Fused aluminas tend to be used in refractories which are exposed to very severe conditions.

 

Brown Fused Alumina is manufactured from bauxite. Its impurities are reduced to precipitate as Fe-Si-Ti system iron alloys, but some of the titanium forms a solid solution with alumina. This causes the brown colour of the material.

Fused Alumina has a very high degree of toughness and can be used to produce high purity refractory shapes and monolithics, investment casting shells and for abrasive applications.

Typical Chemical Composition

Alumina
Al203
99.2%
Silica
Si02
0.15%
Iron
Fe203
0.5%
Titania
Ti02
0.2%
 
Available sizes:
 
120 mesh powder (125 microns)
325 mesh powder (45 microns)
600 mesh powder (20 microns)
 

Zirconium and Yttrium Oxides

Speciality powders used in investment casting of titanium/alloys

Contact the office for further information.
 
Cobalt Aluminate
 

Used as an additive to control the microstructure of turbine blades and medical instrument investment castings. Contact the office for further information.