Bizarre Smelt - Contaminants???

[Bigslug]

Over the last week or so I've been going through the various bits of scrounged metal, figuring out what I had stashed.

Some of this stuff consisted of ingots from the hoard of an old caster who had "left the range". I ran all of these through the hardness tester and segregated them into categories for today's smeltdown.

Maybe ten of these ingots fell into the BHN range of 11-13, so naturally, I figured they started life as wheel weights. I put them in my pile of shotgun pellets and similarly hard scrounged boolits I had no use for in their current form. To maintain some uniformity during the smelt, I tried to add roughly equal amounts of these ingots, shot, and each type of boolit to the pot for each melt.

One of these melts was. . .weird. When pouring the ingots, the surface tended to form small bubbles like you might see on a milkshake. None of the other melts did this, so I re-potted, re-melted, re-sawdusted, and re-poured. Same thing, though not to the same degree. Ingots very frosty and running 10-12BHN without any benefit of age hardening.

I'm guessing there was something wonky in one of the old guy's ingots. I'm keeping that twenty or so pounds separated for now in the event it's truly something evil.

Any ideas what happened?

[runfiverun]

bet it was kinda grey colored too.
that is what high antimony alloys do.
easy nuff to deal with, just turn up the heat and flux.
turn down the heat and wait for the fluff to come out.

[Bigslug]

Very light grey, in fact. Seems to have large ugly crystals - kinda like you'd see in ice cream that's thawed and refrozen, though that's on its second melt. It was getting windy later in the day, and that did play a part in keeping the temperature consistent.

The thing that has me puzzled is that I got that bubbly result - twice - with this batch in between multiple batches of (theoretically) the same stuff.

[dbosman]

Very light grey, in fact. Seems to have large ugly crystals = Gray metallic antimony crystals.
From what I've read, the color varies depending on the specific oxide or chloride chemical composition.

[Bigslug]

Quite possibly. There's no shine to these new ingots at all - kind of a flat, titanium color.

Everything in this series of melts tested to 11-14BHN beforehand. In each of the 4-5 melts, there were probably 2-3 of the old guy's 1# ingots mixed in with 6-8# of the miscellaneous boolits, and then up to the top of the 25# pot with birdshot from the same source.

I guess this particular batch may have gotten a little more antimony despite my best efforts to keep it all semi-consistent. It's already testing at full wheelweight hardness without any aging. . .maybe I accidentally made linotype.:mrgreen:

[dbosman]

Hard bird shot has antimony.

[leadman]

Some shot is also Bismuth. Don't know what this does when melted.
I use Marvelux to flux and it makes a foamy head like a milk shake but once cooled it breaks apart very easily and is brittle almost like glass.

[runfiverun]

bismuth lowers the melt temp but also adds hardness.

the graphite from the shot will also act all goofy on top of the pot when melted down.
the shot also has extra arsenic in the mix.

[Bigslug]

No questions about the shot. Part of it was a 25# bag of unused #9 magnum shot, the rest was all known-source @#7 It's all antimonied lead, probably with the usual trace of arsenic.

Like I say, there were about 4-5 batches and just this one turned out strange. The only differences between those batches might have been in content of Old Guy Ingots or slightly more or less of the shot or bullets that were grouped together by calibrated eyeball. This got me thinking "bad ingot", and was wondering what the "bad" might be.