Crazy Alloy Characteristics!

[303Guy]

Got some grade 11 Babbit and added what seemed an appropriate amount to my pot of drain pipe lead with some solder jointing in it so tin content is quite high. This stuff casts well and is fairly hard and pretty strong. But, it 'flows' under load given a little time. The first peculiarity I noticed was when a casting came out good then I noticed a slight depression in the side. So OK, a shrinkage depression. The next time I looked the depression seemed deeper and I thought 'nah, I'm imagining things'. When I looked again there was no doubt this depression had deepened.

Well, firing these things was revealing. First off, they were quite firm to size even the smallest amount. But at low charges (making the boolit recoverable) I found that the short flat noses had slumped or bumped up to fill the grooves yet had withstood the catch medium quite well.

It's as though the alloy is tough and fairly hard but flows slowly. Kinda the opposite way round to what one would want in a boolit alloy.

Any thoughts and ideas? I want an alloy that expands and holds together on impact but does not 'slump' in the bore.

This one started out as a bore rider.
http://i388.photobucket.com/albums/oo327/303Guy/256grImoldAUTOSOL003.jpg

This one was a bore ride half patch. The shank ahead of the patch was an 'interference' bore ride.
http://i388.photobucket.com/albums/oo327/303Guy/FIRE-POLISHING001.jpg

This one here was a bore-ride nose patched boolit. Even the very short nose has bumped up to fill the grooves.
http://i388.photobucket.com/albums/oo327/303Guy/BoolitSkid.jpg

The thing is that for the boolit to be captured in this condition the velocity has to be low or this is what happens to them.

http://i388.photobucket.com/albums/oo327/303Guy/15828W748POLY003.jpg

Maybe they just need to be driven faster so as to not give them time to upset in the bore? That first one is a 257gr so the acceleration has to be quite low yet the nose has bumped up that much.

[runfiverun]

how high is high on the tin?
15-1 20-1 pounds of lead to tin.
how much copper is in this #11 babitt?
it's not acting strange, it's just doing what this alloy does.

[303Guy]

I did work out the proportions but I've lost them. They'll turn up. Anyway, it's 85% tin with equal copper and antimony. It is a nice alloy so stay with it you think? I had been thinking of raising the antimony content to about half the tin for initial hardness.

If the alloy is good for patch then I'll leave it and use something else for plain cast, like WW if I can sneak some from the fishermen (swap them drain pipe ingots maybe).

[runfiverun]

okay that explains a few things.
the antimony should equal the tin, unless it's something like 1% or less.
my normal alloys have less tin that antimony.
if you are seeing dark spots in the alloy that is tin that is torn away from the antimonial chain
forming hard spots of tin on the surface those spots are surrounded by soft lead.
the copper is fighting with the torn tin on the surface.
that would also explain the malleability of the alloy.
remember the numbers i gave you before of the @ 3% antimony .5% copper and 2% tin.
that gives you a balance of tin to antimony and enough to keep the copper in suspension.
it also allows the fill out of the mold.
if you keep the antimony under 1%, it helps hardness about 2-3 bhn without interfering with the Sn-Pb bond and copper solubility.
set back should have been controlled by the paper even with this alloy.
the bump back would have torn the paper and caused leading at any velocity over about 11-1200.