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820 Standard Yellow Rolling Master 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.
No gold content
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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