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860 White All Purpose Master Alloy for 14-18K White Gold 1 oz. (28grams). Mix 860 white alloy with fine gold to obtain 14K or 18K white gold for sheet, plate and wire fabrication. Can also be used for investment casting if desired.
No gold content
Purpose
- Mix Alloy #860 with fine gold to obtain 10K or 14K white gold for sheet, plate and wire fabrication.
- Can also be used for investment casting if desired.
Melting
- #860 Alloy and fine gold should be melted together in a clean crucible. Put the alloy in the bottom of the crucible and the fine gold on top.
- Initial melting temperature should be 1070°C / 1958°F. Drop the temperature somewhat before pouring as listed below.
- Boracic acid flux should be used to keep the metal clean during the melting process. The molten metal should be mixed well with a stirring rod before pouring to assure a good mix.
- A neutral of reducing cover gas is very helpful in melting white gold alloys.
Pouring Temperature for Ingots
- 10K 1040°C / 1904°F.
- 14K 1010°C / 1850°F.
Pouring
- Metal should be poured in to a preheated, vertical graphite or lightly lubricated iron mold.
- A steady, even pouring motion should be used, slowing down at the end of the pour to prevent shrinkage in the the top of the ingot.
- Use a round rod mold for wire, and a 2-piece, L-shaped mold for plate and sheet.
- A combination ingot mold may also be used.
Quenching
- Remove the ingot from the mold and allow to air cool - don't quench. Nickel white gold rolling alloys will be much softer if allowed to air cool after pouring and after annealing.
- Soak ingot in a hot pickle solution to remove surface oxides.
Fabrication
- The metal ingot should be cleaned of all adhering oxide or fluxes before rolling.
- The ingot should be rolled or drawn to a 50% reduction in size before annealing.
- Too small of a reduction can cause the ingot to crack during anneal.
- After annealing, continue the reduction at 50% before annealing again. Clean the ingot after each anneal in hot pickle solution.
- Keep the rolls, dies and metal clean to prevent defects in the finished stock.
Annealing
- Annealing temperature: 732°C / 1350°F for 20 minutes.
- DO NOT QUENCH INGOT - allow ingot to air cool.
- A boracic acid fire fire coat should be applied before annealing in an open atmosphere oven to protect the metal from heavy oxidation.
- Clean the ingot in hot pickle solution to remove surface oxidation after annealing.
- Avoid over-annealing wire, plate or sheet stock as this can cause excessive grain growth, creating an orange peel surface or poor strength in finished goods.
Re-Melting
- Use a 30% scrap to 70% fresh mix on nickel white gold alloys.
- White gold alloys have about 1/3 the re-usability of yellow gold alloys.
Investment Casting
- Pre-alloy #860 alloy and fine gold and pour into water to make shot.
- White gold alloys have about 1/3 the re-usability of yellow gold alloys.
Pre-Alloying Temperature
Casting Temperature
- 10K 1040°C / 1904°F.
- 14K 1000°C / 1832°F.
Flask Temperature
- Use a somewhat hotter flask temperature.
Quench Time
- 8 to 12 minutes for invested flasks.
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