Helpful Hints for Investment Casting Pure Gold and Silver
Casting pure gold and silver can be done with regular casting equipment. With pure metals there is a much smaller casting window due to the rapid chill rate of the metal. Casters familiar with casting platinum will find casting pure gold and silver relatively easy applying the same type of sprue systems to the castings as those used in platinum casting. The designs being cast in pure gold & pure silver should avoid thin or highly detailed areas that will present fill problems when using pure metals. The designs must be sprued to the heaviest part of the casting to avoid shrinkage porosity in heavy areas. Much higher casting and flask temperatures are required to cast pure gold & pure silver due to the rapid chill rates of the pure metals. The casting may be done with centrifugal or vacuum casting equipment using regular jewelry investment. Extra care is required during investment removal to prevent scratches, dents or bending of the metal due to the softness inherent in pure gold & silver. Smaller trees are normally used for pure metals due to the rapid chill rate of the metals. Joining of pure gold & silver must be done by fusion and pure gold or silver sizing stock must be used. Pure gold or silver will bond to itself at high heat.
PURE GOLD CASTING PARAMETERS
Melting Point - 1064 degrees C. / 1945 degrees F.
Specific Gravity - 19.32 grams per cc. – 19.32 x Wax weight.
Casting range - 1160 to 1170 degrees C. / 2120 to 2138 degrees F.
Flask Temperature - Vacuum Cast - 1200 to 1350 deg. F./ 648 to 732 deg. C.
Centrifugal Cast – 1050 to 1100 deg. F./ 565 to 598 deg. C.
Flask temperatures should be adjusted to the size and weight of the castings.
PURE SILVER CASTING PARAMETERS
Melting Point - 962 degrees C./ 1762 degrees F.
Specific Gravity – 10.49 grams per cc. – 10.49 x Wax weight.
Casting range – 1050 to 1060 degrees C./ 1922 to 1940 degrees F.
Flask Temperature – Vacuum Cast – 1150 to 1300 deg. F. / 621 to 704 deg. C.
Centrifugal Cast – 1000 to 1100 deg. F./ 537 to 598 deg. C.
Flask Temperatures should be adjusted to the size and weight of the castings.
Note: Pure silver can dissolve many times its volume of oxygen in a molten state. A reducing cover gas or neutral cover gas is strongly recommended during the melting process to protect the molten silver. For high production casting, a small addition of lithium is helpful in removing dissolved oxygen.
No guarantees are made for the aforementioned procedures that are provided as information for United customers.
Precious Metal Spot Prices
|Gold||2019-04-23 2:18 PM|
|Silver||2019-04-23 2:18 PM|
|Platinum||2019-04-23 2:18 PM|
|Palladium||2019-04-23 2:18 PM|
Prices shown are for reference only. Please contact our trading desk for accurate, up-to-the-minute pricing.