Zinc in Lead

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Sep 14, 2006

I am confused. In the article "The metallurgy of Molten Lead Alloys" by Dennis Marshall in the 3rd Edition of Lymans Cast Bullet Handbook I don't understand the properties of lead + zinc. Let's say I melt some wheel weights, which I did, and some where zinc....I didn't think so but.....

At 787.2 F zinc melts. Lead melts at 621.5 F.

I melted the wheelweights over my Coleman stove and pore my ingots. Some looked weak and 2 even broke. Malleability was not there.

If I do have a zinc contamination can I separate the zinc from the lead by remelting the ingots at a temperature above 621 but below 787?

I am using a bottom pour (Lee) system.
I had a batch of WW get contaminated with a few zinc ww's. It only takes one or two to screw the pooch. I noticed what looked like crystals forming in the currents of the lead when stirring. Makes for some nasty slag too.
If you're sure it's contaminated with zinc, pour into ingots and save it for the scrapyard. I got about $.60 /lb for my aborition, IIRC.
I still don't get it. According to the article mentioned, the two should separate and form an immicible layer. With lead being more dense the zinc should rise to the surface, allowing me to cast off of the bottom.

yeh or ney?
ney. Zinc ruins lead like crazy. Depending on your casting experience. I have seen new casters cast bullets with dirt in them. then the bullets break. You need to flux the lead first before you rule out zinc. Take a good pea sized piece of wax and stir it in the lead. alot really good scraping the sides and everything. The dirt will rise to the top. Scoop it up and disgard. Thats probably the stuff in your bullets. do it a couple times to make sure you have it all out. Now make sure your molds are hot very hot heated up. to wear if you were to slowly drag a corner over a piece of wood it would put a burn mark on it. Now start filling the molds. if after around 5 trys the bullets do not look clean all filled out. Then you may have zinc in the batch. Common signs for zinc is not filling out the molds. Almost half looking bullets with rounded edges not clean cut edges. If you have that. Best thing to do is disgard the lead. As all it take is a very small amount of lead to ruin a pot.

I will try that. I will put about 7-8 pounds in my Lee, get it melted and flux the bejeebers out of it. I know I pulled a lot of dirt out during the first melt. I will flux some more. As far as I was concerned, I did a good job of checking the wheel weights.

The first time I did wheel weights I did smaller batches in my Lee but decided to do the 20 lbs in a pot over a Coleman. It is possible I didn't get it clean enough. The first two sets of ingots looked fine. Then came two sets of bad ones... 2 even broke as I dumped them out of the ingot mold. The final ingots looked ok.
According to what I've seen over on cast boolits .com, IF you have a thermometer, you just bring the melt up to over the melting point of the lead, but under the melting point of zinc. It WILL separate and form a scum on the surface of the melt. Then just skim that zinc off the surface, discard it.

I've never had to deal with it, so I don't know if it works or not.

Thank you.

That is what I thought and was asking for clarification. I do have an RCBS thermometer and I know I can controll the temperature between the two melting points. The zinc should rise to the top...lower density and I bottom pour the ingots.

Do others agree???????
depending on what lee pot you have. if you have the adjustable type. take it to number 6 and just wait like crazy until it melts. its going to take a while as you usually have to put it on 9 then bring it down to 7 for a good temp.
The zinc should rise to the top...lower density and I bottom pour the ingots.

Do others agree???????

I disagree. If the zinc is dissolved in the lead, it won't separate out significantly. It will oxidize faster that the lead, but I don't know of any practical way to take advantage of that.
According to the above mentioned article, the zinc doesn't go into significant solution until much higher temperatures.
If I do have a zinc contamination can I separate the zinc from the lead by remelting the ingots at a temperature above 621 but below 787?
My guess is No. You will take out all the antimony that makes the bullet hard. If you can't form good bullets with the pot temp at its highest setting, then the alloy is not usable.
243.....I would be casting the bullets at a later time. Right now I want to determine if I can remove the zinc by temperature control and density differences. Later I will remelt the now "good" ingots at a very high casting temperature.
I stopped casting years ago before this was a problem. Is there any telltale sign that a person could use to sort zinc from lead WWs before they even go into the pot?
Reading your description I'm not sure it's zinc.
Flux it and cast some bullets you will know pretty quick.
I have some WW of unknown origin.

After problems with fill out, I have been worried about the Zinc contamination as well.

Lead, tin, antimony, copper, zinc and a few other things are common in WW. Of the three popular(Pb,Sn,Sb) bullet-making elements, Tin has the lowest melting point(449F), then Lead(629F) and Antimony(1167F) having the highest. Zinc has melting point of (787F). However, I have read that Zinc will not separate by melting the composite WW.

I am very new at bullet casting.

After researching on Castboolits, this, and other sites, I decided to do a lot of skimming, fluxing, temperature experimentation, etc. to clean it up. The fill out is much better.

Zinc or not, I shoot these bullets at between 750 and 900 fps in Lee FN 200gr .452 configuration out of my 1911. I have shot some out of the XD, but have sold that gun to my brother. I don't have a scale that goes past 100gr, so not sure on final weight, but the bullets perform great.

I have also heard of people adding Tin solder to the WW. I have put my WW cornbread ingots into Lee mold ingot(I'm fancy :D) and will experiment with the Tin.

I use the Lee bottom pour pot as well. The small one.

Cast a few, lube and size them and shoot em up. If you can shoot them into a bullet trap for retrieval, then great.
FWIW - I was really paranoid about this when I started smelting about a year and 1/2 ago . . . .it's a non issue if you keep your temp around 700 degree's (or lower) in the smelting pot. If I have any doubts as to whethe a weight is zinc I drop it in the melt and see if it floats after 2-3 seconds . . if it floats it gets skimmed and tossed. I think the guys that get in trouble are the one's that fill a huge pot, set it on the turkey fryer and then go mow the lawn for an hour . . .if you're watching, skimming clips and monitoring the temp you'll NEVER have a problem.

Just my .02

Removing zinc and copper from the alloy

Take your scrap metals, put in a large pot, mix, flux, remove by skimming copper jackets, dross, misc for pot. Sand will lay on the bottom. Make ingots using a ladle. Now take you clean ingots, remelt to a temperature just hot enough to melt the alloy. Tin and Lead will melt first. Do NOT flux or stir the pot. The copper, zinc, antimony will come to the surface as lumps. Skim these lumps from the surface with a tablespoon without stiring or mixing the alloy. This will leave tin and lead in the pot. This is a slow process as the temperature must be raised very slowly, starting at 500 degrees. Your really over thinking the casting process. Its very simple in most cases. Melt alloy, flux, cast. Set temperature high enough to make the bullet fill out completely. Check the bullet diameter as the bullets drop from the mould to make sure they are not undersized at the start of your casting session. Don't worry about bullet weight. Use a soft bullet lube. Most of the information comes from casting for over 40 years. There also was a story i read on removing copper from the alloy that plugs the bottom pour pots. It works but a very slow process. I solved the copper plugging by opening the hole in the spout and higher temperatures.
Sand will come to the top with the rest of the crap.

Antimony in the alloy is a good thing unless you are casting for a muzzleloader. Why would you want to oxidize it out (and take a good bit of the tin with it)?
zxcvbob, if its not sand, its something else. The antimony we want to keep, but you can not tell the difference between zinc, copper, or antimony by looking. All 3 will come to the top if starting at 500 degrees and trying to get rid of zinc. And i still think you can NOT get rid of zinc in this manner, it will work with coppe deposit because copper melts at a higher temp. When you have all these metals in the same alloy, the melting temp. is changed for all metals in the mix.
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In the first place in lead alloys, once a metal is incorporated into the lead, it stays alloyed. The theory that the lighter metals "float" out is erroneous. You will have an oxide layer that forms on the surface of the melt. That's why we flux, to re-incorporate those oxides into the alloy. Any carbon based compound will work as a flux.

Now we come to the zinc that's alloyed into the lead. Will it "float" out? There's someone over on cast boolits that is doing an experiment to find a way to do that reliably. He may have posted here, wanted zinc contaminated lead for his experiment. Nothing from him lately, I'm sure he will let us know what he's found out.

As said, temp. control when smelting wheelweights is the best solution to preventing it in the first place.
I've had a few batches that just wouldn't pour and fill out well, for whatever reason. I fussed with the stuff for a while, then said, "What the heck" or something like that and used that stuff up pouring fishing weights. Those don't have to fill out perfectly!
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