I have pretty much exhausted the search engine on here and the net on alloys of lead + bismuth in casting what we do.....boolits. There is really no definitive experience with it by anyone I can find....so here goes with some fresh info........
Recently I happened on MANY pounds of large ingots of an unknown shiny alloy. I now call & stamp it "Banger's Alloy" (BA) so I can keep it segregated from the other shiny ingots in my "stash".
Upon analysis with a $40K x-ray gun, it is made up of:
Bi 56%
Pb 26%
Sn 13%
Sb 5%
It has a hardness of 22+ bhn on my Cabine tester.
It melts at EXACTLY 160F! It is reeeeeeely neat to drop a small hunk of this in some hot water right out of the microwave and see it melt in the bottom of the cup! Impresses the crapola out of people. It seems so strange to melt a 10# hunk of this stuff with no smoke/fumes/reducing on a hotplate set at medium! And......you can stick your finger (quickly ) in molten silver metal without getting 3° burns.
It is a eutectic alloy used for something, but is does not behave like Cerrobend (it does not shrink in 30 min) so you cannot get it out of a tube/barrel! It is somewhat brittle when in a thin form, something like Linotype. I think it may be some sort of low temp "holding" alloy used in the aerospace/aviation industry around here in the Southwest. Any thoughts from the crowd are most welcome!
There nothing on Rotometals that is close to this mix and there is NO Cadmium or Indium in it. Closest composition I can find on the net is Rose's metal, but it's melt point is at 200F+.
Well.....after several experimental melts/mixes, and ignoring the collection of several "Honey do's" that were gathering dust, I came up with the following:
1# of dead pure lead (~5bhn) + 1.5oz of BA gives me a perfect 14+ hardness "as air dropped" that becomes 18+ in 48 or so hours. It fills the molds beautifully.
After 48 hours, I did my standard "Banger's Impact Test" (pounding the slugs flat from nose to base on a 4" dia x 2" thick steel round with a 4# hammer) and there is absolutely no sign of flaking/brittleness/cracking.
So, we can now guestimate that a small ratio of Bi and Sn ( with a little help from the small amount of Sb) when alloyed with Pb work hand in hand and accomplish what we are all after - a hard shiny alloy that fills our molds perfectly!
I now have a lifetime+ supply of this stuff.
Hope this helps anybody else out there that has access to Bi/Sn alloys.
bangerjim