Re-zinc contaminated lead

[44man]

I had to add more ingots to my pot today and did a better job cleaning the 20 to 1 mixture. I turned the Lee pot to 550 degrees and just let it melt. Took some time because the pot cycled a lot.
I skimmed the surface until the lead looked very clean, turned it to 800, fluxed and made a pot full of boolits. I did not have a single reject for the whole pot. Ladle poured, of course. These are Postell's.
I thought you would like to see what came off the surface. It is very hard.

[GP100man]

44MAN
good job & good looking postells!!!
not to many yrs ago that contaminated leadwould have been fish sinkers ,
a sign of the times i guess.
GP

[bigborefan]

44man, So after bringing up the temperature, you just skimmed the surface without fluxing it and then fluxing at 800 degress? Does any of the tin or antimony get skimmed with the zinc contamination? I think I'll try that with my next batch of casting lead.

[44man]

I only skimmed at 550 degrees, then raised the temp to 800, fluxed and only had the normal dirt on top to skim. It doesn't seem like I lost any tin because the boolits cast real nice. The tin stays alloyed while zinc floats.
If you cast boolits with any zinc, it rushes to the surface as it cools.
I had a few pounds left in the pot so I poured it into my ingot mold. They look good with no galvanized appearance. I dumped the pot, removed the bottom pour drip-o-matic and plugged the hole with a slightly tapered brass piece. More room for my ladle now.
I haven't tried it with WW metal yet so I don't know if you will lose antimony. I am going to experiment by trying it and then casting something to compare the hardness.

[Taylor]

I have had the same issue lately,a lot of stuff on top.It's almost like you are wasting lead. The boolits come out fine,is this zinc? I do know where I got it,and did manage to keep it separate from all else. In one casting I had to add extra 95/5 to make it work,and I have been fluxing the day lights out of it.

[44man]

I am going to clean up all of my lead that is supposed to be pure. Anything that floats at 550 degrees doesn't belong there. A teaspoon or two out of a pot doesn't amount to anything and there is no sense fluxing it and mixing it in.
I hate the thought of diluting it with known good lead and making a larger batch of contaminated stuff.
That divers weight I added must have been made from a lot of scrap and had to have the zinc in it. All the other lead was cable sheathing and pipe. The problem is that when all of the ingots are piled together, there is no way to tell which batch the bad stuff is so all of it has to be treated as bad.
I don't know what the antimony in WW's will do at the low temperature. I add extra antimony at 600 degrees and even though it has a very high melting point, it melts and mixes just fine. Just need the right flux.
What I have to know is if I take a batch of my alloy and re-melt it at 550 degrees, will the antimony float or stay alloyed? How much tin is floating?
I guess I will test a small batch, whatever I skim off can be just put back in and fluxed so it is no loss. It would be nice if the skim could be analyzed at home.

[montana_charlie]

44man, I'm no metallurgist, but try this way of thinking about it, and see if it makes sense to you.

Say you are melting wheelweights. You bring the pot up to 700-800 degrees, and most everything melts...but some stuff doesn't. If you flux the bejeezus out of it, the clips (and other things which aren't hot enough to melt) still float around on the surface.

With that in mind, turn your attention to your present project.

You have a mixture that (you believe) contains some zinc...which you know needs more heat to melt than tin, lead, or antimony does. So think of the zinc the way you view wheelweight clips.

Tin lowers the melting point of lead...maybe even below 500 degrees.
If you have the pot at 500 degrees (or a bit less), anything that isn't melted must be zinc. No matter how much you flux (to re-combine tin and antimony) the zinc is going to float - like clips, sand, and tire valves - 'cuz it isn't melted.

How does that compare with what you already know?
CM

[felix]

Not necessairly so, MC. Antimony melts at a very high temperature too, and you can flux that in fairly easily, once it has been fluxed in before. Best to let everything melt and not stir at all. Then take everything off of the top and trash it into another trash pot for later analysis. In general, zinc melts into a floating cow patty that is quite obvious. Anything that does not melt, we are talking about the monster melts in the MOAS now, gets pitched for permanent disposal. We just don't have the energy and/or time to mess with it. Yes, perhaps some good stuff gets thrown out, but we have other stashes of stuff we can use to re-augment the smaller casting pots when necessary. ... felix

[mto7464]

44man, what is the stuff you skimmed off in your pic? I just did a pot a skimmed alot of like looking stuff off.

[44man]

I'm sure it was zinc. I left the pot on for quite a while at 550 degrees, did not stir it and skimmed off the slush. Thats what it looks like, slush.
Remember this was pure lead with a small amount of tin added when I cast the ingots.
The slush is very hard when it gets cold. The lead looked very clean after and made perfect boolits.
When I first tried to cast with this stuff the boolit would not fill out and they had that galvanized look, not the same as a frosted boolit from a hard alloy. Poured into an ingot mold left the surface with the same look, just like galvanized steel.
Montana, the zinc does almost melt all the way but it is slushy and thick. You sure don't want to flux it because it will mix in. It has some lead and tin mixed with it but not enough to worry about wasting. If it was just a chunk of pure zinc, it would just float. If you were to start fluxing and stirring, that chunk would eventually melt in.
Thats why you should keep the temperature down when smelting WW's. Skim off all the clips and anything that doesn't melt before doing any fluxing.

[truckjohn]

Saw the same thing last weekend while casting.

Seemed like things started going south on me. Lo and behold,
stir the top of the pot and it is covered with clumpy trash.

Skim it all back out a couple times and go back to casting.
All of a sudden, things are back to casting right again.

I also ended up with another pile of WW's that just won't melt.
They look riveted together... not cast. Figured they might be Zinc --
so saved them till the end to melt in with the clumpy trash from last weekend...
They don't melt -- all the way up to bright orange hot.... Are people
starting to use Stainless steel wheel weights instead of Zinc or Lead?

Thanks

John

[mto7464]

John, There are steel WW. that is probably what you have.