ALLOY COMPARISONS

SILICON DE-OXIDIZED ALLOYS

ADVANTAGES:

1. Resists absorption of air (oxygen).
2. Low porosity rates.
3. Castings do not oxidize after cast.
4. High reusability factor.
5. Low scrap factor.

DISADVANTAGES:

1. If the silicon oxide that is formed during repeated use is allowed to remain in the melt, the silicon may cause cracking. This is discussed at length later on.
2. Floric base devesting solutions are needed if any cyanide treatments are to be performed after casting.
3. Silicon alloys have a large grain structure which makes it more difficult to roll or form.

SILICON-BORON ALLOYS

ADVANTAGES:

1. The same advantages as silicon only alloys plus.
2. Better fluidity.
3. Better solidification characteristics reduce shrinkage porosity.

NON DE-OXIDIZED ALLOYS

ADVANTAGES:

1. Most malleable of all alloys.
2. Most fluid of all alloys.
3. Best in centrifugal casting when small pours are made.

DISADVANTAGES:

1. Subject to high porosity rates when exposed to air
2. Dark coating on cast after break-out.
3. Low reusability rate, due to copper oxide build-up.
4. Requires higher ratios of fresh gold.

BORON DE-OXIDIZED ALLOYS

ADVANTAGES:

1. Moderate de-oxidizing properties.
2. Better fluidity than silicon alloys.
3. Slightly better cast appearance than non de-oxidized alloys.
4. Works well in centrifugal casting.

DISADVANTAGES:

1. Lower reusability rates than silicon alloys.
2. Marginal protection from porosity.

Were commend silicon alloys when ever their use is appropriate, when vacuum casting where high productivity and reusability is needed. Choosing the proper alloy will depend on production equipment and productivity requirements.