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10K gold melts before solder


#1

A few weeks ago, I made a 14K rose gold that was cracking and decided to turn it into 10K yellow. With the 10K yellow it rolled out just fine. The problem now is that when a I come to solder it with 14K hard solder, the gold melts before the solder. The alloy is now:

41.7% pure gold
35.9% Pure copper
22.4% pure silver

The solder was 14K hard solder from rio grande with a flow point of 804 degrees Celsius. I don’t know the liquidus of my homemade gold alloy but I am inclined to believe it is lower than that of the solder. Checking the flow point of rio gramde’s 10K hard, it is 802 degrees Celsius and so only 2 degrees lower. Do commercial 10K yellow golds melt at higher temperatures? This seems surprising abs they all have around 8% zinc or even more which to my knowledge lowers the melting point? Should I seek out a lower melting temperature 10K hard solder or maybe try a medium or easy? Would the join be too weak with a lower temp solder or is it proportional with the melting temp of the alloy being used?


#2

Get a gold-silver-copper phase diagram and learn how to read it. You will then be able to know at a glance the melting point of any gold-silver-copper alloy you care to make. Well worth your time and effort.

Janet in Jerusalem