Carat : 18 - 22
Colour : Indian Yellow
Melting Temp of Alloy : 870 0C
Application: The alloy SP 183/2 is an ideal choice for hand-made and investment cast jewellery, usable from 18 to 22 carat. It is suitable for jewellery manufactured for both Indian as well as Western markets. It gives desired softness in 18 carat; and with its good fluidity it ensures very sound and porosity-free cast finished products.
Recommended Practice: 18K 22K
Application : Casting / H-made Casting / H-made
Alloying Temp. : 10000C - 10300C 10400C - 10600C
Casting Temp. : 9800C - 10200C 10200C - 10400C
Flask Temp. [Normal Cast] : 6400C - 6600C 6400C - 6500C
Flask Temp. [Stone Cast] : 6200C - 6400C 6200C - 6400C
Quenching Time : 10 - 15 minutes. 15 - 25 minutes
Pre-Alloying is strongly recommended simply to ensure better homogeneity in castings as well as in hand made products. Also, for still better results, pre-alloying in an inert atmosphere is always preferred.
The actual casting temperatures and flask temperatures shall be decided by the parameters like the section thickness of the items (thick, medium or thin), the overall size/bulk of the cast tree, the design intricacies etc.
As a thumb rule, for thinner sections higher temperatures are selected and for thicker sections lower temperatures are preferred. At the same time, designs demanding higher form filling capabilities, higher than normal temperatures are an obvious choice.
The 18 carat casings have a tendency to get hardened and subsequently give problems of cracking especially when flasks are cooled very slowly. For this reason, it is recommended that the flasks are cooled as fast as permitted by the quality of diamonds and also by the design parameters.
Cast Tree Cleaning & Drying procedure: After primary removal of the investment during quenching, submerge tree in a hot (80-100oC) 50% phosphoric acid solution for 15-20 minutes. Rinse well with cool water to remove remaining investment powder and base metal oxides. Dry with compressed air.
For reusing the castings we recommend 60% fresh carat gold with 40% castings.