Fusing two metals during cast

Hello,

I am casting a two tone ring and want to cast one component onto the
other. Meaning cast the white gold component semi finish it and then
attach the yellow gold (wax) component to the white gold and invest
it. Casting the yellow gold into the flask and attempting to fuse the
two metals. Is there any published info on this technique, or has
anyone had any experience with it? I have done thousands of small
inserts into two tone flower designs but am having issues with
heavier ring designs.

Thank you

JBF
www.jbfriedman.com