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860 White All Purpose Alloy for 10-14K White Gold 1 oz. (28grams). Mix 860 white alloy 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.
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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