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820 Standard Yellow Rolling Alloy for 10-14K. 1 oz. (28 grams).
Mix Alloy #820 with fine gold to obtain 10K or 14K standard yellow gold for sheet, plate and wire fabrication. Can also be used for investment casting if desired.
Alloy #820
Purpose
- Mix Alloy # 820 with fine gold to obtain 10K or 14K standard yellow gold for sheet, plate and wire fabrication.
- Can also be used for investment casting if desired.
Melting
- #820 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 1040°C/1904°F.
- Drop the temperature somewhat before pouring as listed below.
- Boracic Acid flux may be used to keep the metal clean during the melting process.
- The metal should be mixed well with a stirring rod before pouring to assure a good mix.
Pouring Temperature for Ingots
- 10K 980°C/1796°F
- 14K 950°C/1742°F
Pouring
- Metal should be poured into 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 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
- The metal ingot should be removed from the mold and quenched immediately in pickle solution or water.
- For heavy ingots, a one minute cool-down before quenching prevents quench cracking.
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. After annealing, continue the reduction at 50% before annealing again.
- Clean the ingot after each anneal.
- Keep the rolls, dies and metal clean to prevent defects in the finished stock.
Annealing
- Annealing temperature: 675° C/1250° F for 20 minutes.
- Quench immediately in water or pickle solution.
- A Boracic Acid fire coat should be applied before annealing in an open atmosphere oven to protect the metal from heavy oxidation.
- Avoid over-annealing wire or plate stock as this can cause excessive grain growth, creating an orange peel effect on the surface of finished goods.
Re-Melting
- Use 50% scrap to fresh mix when remelting to prevent oxide build-up in the metal.
Investment Casting
- Pre-alloy #820 and fine gold and pour into water to make shot.
Pre-Alloying Temperature Casting Temperature
- 10K 960° - 980° C, 1760° - 1796° F.
- 14K 930° - 950°C, 1706° - 1742° F.
Flask Temperature- Normal recommended temperature.
Quench Time
- Wait 15 minutes before quenching flasks.
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