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44man
01-14-2007, 01:23 PM
Somehow I got some zinc in my pure lead. Might have been a diving weight I threw in. I mixed up a batch for my BPCR and could not get a good boolit. Bands would not fill and they looked galvanized. I poured it all into ingot molds and the tops were crinkly, galvanized. I tried something with another batch yesterday. I melted 30# of the nasty ingots and at the second the last ingot melted, I skimmed the thick stuff off the surface. I kept skimming a lot before adding my tin for a 30 to 1 mix. After I poured it into ingots I still seen some on the tops so I just scraped it a little with a knife, as you can see in the picture.
I did the same when in the pot, as soon as the last ingot melted, I skimmed the top of thicker stuff.
I cast these today and all are perfect, zero rejects. The first boolit is on the left.
When I added more ingots before shutting off the pot, I did the same thing. As soon as the lead melted, I skimmed it.
You don't know how happy I am!

44man
01-14-2007, 01:32 PM
Here is a close up of the first boolit

IcerUSA
01-14-2007, 01:34 PM
Nice looking pile of bullets there, hope they shoot as good as they look :Fire:

9.3X62AL
01-14-2007, 01:46 PM
44--

That close-up shows fine work, indeed. I have yet to find any zinc in my metal, thankfully. I'm glad to hear that you were able to salvage the good metal from the contaminated mix, and I will try to keep your method in mind if that ever occurs during my casting work.

Casting "work". If Mark Twain is correct, work consists of what a body is obliged to do, and play consists of what a body is not obliged to do. It's play, for sure. :-)

felix
01-14-2007, 02:55 PM
Al, Mark Twain is close, but his cigar is bent. Work is defined as something you are presently doing and presently wishing, at the same time, to be doing something different. ... felix

Ricochet
01-14-2007, 03:37 PM
Commercial metal refiners get zinc out of lead by skimming it right after the lead's molten. It works for us, too.

ron brooks
01-14-2007, 08:55 PM
Commercial metal refiners get zinc out of lead by skimming it right after the lead's molten. It works for us, too.

So it doesn't alloy like tin does? That is good news.

Ron

Ricochet
01-14-2007, 09:07 PM
If you keep on heating it past melting, the zinc will melt and mix in. Then when it cools, the zinc crystallizes before the rest of the alloy solidifies, making a sludge that will be inhomogeneous when it finishes solidifying.

Melt it slowly and then skim. I can't promise you won't lose some other alloying elements along with the zinc, but it will get the zinc out.

ron brooks
01-14-2007, 09:41 PM
Great news! I had understood it was always there. Still to be avoided, but something can be done about it.

Thanks,

Ron

Mallard57
01-14-2007, 10:01 PM
I was smelting down some ww the other day and found several that didn't melt, I'm assuming they're zinc. What temperature does zinc melt at?
Thanks,
Jeff

Ricochet
01-14-2007, 10:10 PM
Zinc (http://www.google.com/url?q=http://www.chemicalelements.com/elements/zn.html&sa=X&oi=answers&ct=result&usg=__2hNwmJbav0WNFPoxTW6x2_2d9eg=) — Melting Point: 419.58 °C (692.73 °K, 787.24396 °F)
According to http://www.chemicalelements.com/elements/zn.html

Mallard57
01-14-2007, 10:12 PM
Thank you!

DaveInFloweryBranchGA
01-14-2007, 11:13 PM
So if you monitor your smelting operation with a thermometer and keep the temperature in the 625-650 range, one is definately safe and can avoid dealing with skimming.

John Boy
01-14-2007, 11:56 PM
Here's a Zinc Wheel Weight ...
http://www.leadfreewheels.org/zincdh.jpg ... Notice they are marked Zn. There is a big environmental program in many states to also use steel weights. Also heard that there are TIN weights on the market ... gotta get a couple buckets of them [smilie=1:

Ricochet
01-15-2007, 12:00 AM
Dave, if any of the alloy you smelt already contains zinc it'll need skimming.

Sven Dufva
01-15-2007, 08:15 AM
You can boil it away too

357maximum
01-15-2007, 08:20 AM
You can boil it away too

Explain please.....I have about 500 pounds of mystery alloy(don't cast worth shi*), and enquiring minds want to know....the skimitoff method sounds real good...but the boilitoff method has my attention also...

44man
01-15-2007, 09:55 AM
I don't know if we can get the lead hot enough with a stove to boil any metals off and I think you have to add chemicals, not sure. I didn't want to lose any tin to speak of and the way the boolits cast, I would say I didn't.
Just keep the melt to about 600 degrees and as soon as the last ingot just melts, skim all the stuff from the surface. The zinc will still be thick. You can't get all of it of course but the difference is real nice. This will save me a good 100# of lead that I was worried about.
I don't know where the stuff came from because most of my lead was cable sheathing and water pipe. It had to be from the divers weight, I can't find it so I must have dropped it in the pot. I never seen any indication of zinc on the thing.
If you cast a clean, new ingot, let it cool and look at the top, you will see a galvanized surface where the zinc rose to the top. The ingot will be silver colored too, not the slight blue of pure lead. Tin will make them silver but without the crinkly looking surface. No other metal will show up like zinc does. It doesn't seem to stay alloyed good and seeks the surface when cooling and is the problem in a boolit mold, preventing fill out. It starts to harden before the base metal and moves through it. That galvanized boolit surface might cause leading too when it scrapes off although a pure zinc boolit would probably not cause a problem. I don't know that much about it, just observations on my part, so take what I say with a grain of salt until someone can clarify it.
You have to remove all you can right at the lead melting point or it will not work.
I also noticed that my lead surface stayed cleaner after skimming too even though I cast at just over 800 degrees.

Ricochet
01-15-2007, 02:07 PM
I doubt boiling is a practical way of getting the zinc out. By the time you get to 1000°F or so the lead's vapor pressure is getting significant, too, so you'd need to take precautions against breathing it. It's hard to completely remove small quantities of liquids from mixtures even when well above the boiling point of the minority ingredient. The nice thing about the skimming process is that the zinc stays solid and is much less dense than lead, so it floats readily to the top. Often you can see crystals that resemble frost.

9mmcast
01-15-2007, 03:47 PM
You can boil it away too

Boiling Zinc away would not be a smart play to make. Lead fumes at 825 degrees farenheit. It would be risky (to say the least) to work with the metal beyond 825 degrees even outdoors.

357maximum
01-15-2007, 06:09 PM
44's method seems to be the way to go...boiling not good apparently

Lon
01-16-2007, 01:32 AM
9mmcast, I don't understand, "Lead fumes at 825 degrees farenheit." Are you saying liquid lead turns to gaseous lead at 825 F? Or something else?

Sven Dufva
01-16-2007, 02:22 AM
I talk to a metalurg in new boliden a swedish melt plant he told me that is the way they doit. I agree it a risky way to doit. When zn is boiling it goes away as posion gas. You most check temp all the time if it to hot you boil away tin and lead.

T-Bird
01-16-2007, 08:40 AM
I thought I read a long time ago when I first began fooling with all this stuff that lead began to vaporize at 1100F.If it vaporizes at 825, I am going back to using a thermometer. Shoot straight, T-Bird

44man
01-16-2007, 09:37 AM
1100 degrees sounds more plausible. A lot of us cast at over 800 degrees without a problem. Some guys have had themselfs tested for lead and after year and years of casting had a lower body lead amount then the general population.
I have a hunch that once the vaporization point is reached, there won't be any more dross form on the surface. Does any one know?

Lon
01-16-2007, 03:22 PM
Pure lead boils at 3180 °F. I believe boiling means that the liquid, at the bottom of a bottom heated pot, turns to a vapor or gaseous state and rises to the surface of the liquid. I cannot achieve those temperatures. I don't know the boiling points of various alloys we use, undoubtedly less but not much. I melt wheelweights, etc. very carefully because the smoke of UNKNOWN crud could be harmful. I do not believe any caster has ever inhaled gaseous lead. You certainly can coat your hands in oxides of lead (dark grey surfaces) and then suck your thumb and ingest lead. You can also use a very high RPM grinder/sander on lead and produce particles small enough to inhale before gravity can pull them to the floor.
When I was a boy, 60 some years ago, the folk treatment for painful boils was to swallow fine birdshot of a shotshell. I'm guessing a little dark grey lead oxide got into their bodies and the lead which is very chemically inert passed through. I do NOT advocate this remedy, obviously.

Sven Dufva
01-17-2007, 01:13 AM
Boiling temp lead 3180 F Melting temp lead 620 F
Boiling temp ZN 1665 F Melting temp ZN 786 F
Boiling temp TIN 4715 F Melting temp TIN 447 F
Boiling temp Antimon 2888 F Melting temp Antimon 1166 F

Sven Dufva
01-17-2007, 02:19 AM
Here is a close up of the first boolit

That the way boolits should look. Must be perfect temp and a good alloy and a experence caster.

44man
01-17-2007, 12:21 PM
There are still mystery things about metal. I bought antimony chunks and flux from Bill Furguson to make my hard alloy. It takes a small amount of flux and a temperature of 600 degrees to melt the antimony into the base metal even though it has a very high melting point. Without the flux, you must get the base metal super hot.
Now if we could find a zinc magnet to drop in the pot and pull it all out---huuuum, anyone have contact with aliens?

Ricochet
01-17-2007, 12:26 PM
What you're doing there is not so much melting the antimony as dissolving it, like a lump of sugar in a cup of hot coffee.

The flux is keeping a surface oxide layer from keeping the antimony and lead apart so it can't readily dissolve.

When we heat treat boolits in the oven at 475F or so, the crystals of antimony in the mix are "dissolving" into the surrounding matrix of solid lead.

felix
01-17-2007, 01:05 PM
Keep in mind that if tin does not surround the antimony, lead will. In other words, if there is no tin present in the amount necessary to "cover" all of the antimony, the boolit is just as prone to leading as if no antimony was present. No matter how "hard" the boolit is. ... felix

44man
01-17-2007, 02:41 PM
Felix is right, I add a small amount of tin too. I follow Bill's formula for the alloy I want.