Effects of Zinc in casting

[chaos]

I have a spare bottom pour which is an OLD saeco. This thing has a run away thermostat and the base glows orange. For ****s and giggles, I purposely melted in 2 zinc wheel weights with approximately 8lbs of lead. This lead was stick on wheel weights. Cranked the pot till glowing and cast perfect fishing weights out of it. They weigh a small bit less than they are supposed to.

Gonna try it on some bullets next.

[docone31]

That slight amount might just harden the casting.
Watch for fumes though. When I tried to cast brass, I got a small case of foundry disease from inhaleing zinc fumes. Two days of flue like symptoms.
I do not melt brass anymore.

[chaos]

If that's teh case, then what's the big fuss about picking wheel weights of zinc out before casting?

[docone31]

Its the too much zinc.
Like copper in the alloy, a little dab will do ya.
Too much zinc, and you have gumbo, small castings, and hard, hard, hard castings.
I am not sure they will imprint the rifling and give accuracy.
A little, and it might make a slightly higher velocity possibility. Maybe, I haven't knowlegeably tried it.
I am sure I get a little zinc in the alloy from time to time. I do know, the last batch after I scooped out a bunch of zinc, cast really well, and did not lead at all. I am sure there was some in there. Frankly, I liked the finished performance. Especially the zero leading.
I had less hang ups in the 1911 than ball ammo.

[STP22]

Because when there is enough zinc ww`s in the mix, it will cling to the wall of your pot when drained, and the residual zinc left behind is a PITA to remove. It`s best to recycle known zinc ww`s when they are identified, then seperated from what we need to cast with. Been there, done that...on purpose in fact. Don`t bother.

[docone31]

I whole heartedly agree.
I removed the excess zinc for a reason. I am sure a little got alloyed, and maybe it helped with the casting, but, I am talking a little.
All in all, it makes a real mess, and it is not worth it.

[imashooter2]

Fishing weights don't have the bands and sharp details we want to be perfect in boolits. You'll see the difference shortly...

[runfiverun]

it is the heat that worked for you.
zinc is the enemy??
the more i research zinc as a small time alloy partner, the more i may be using it as a component in some alloys.

[DLCTEX]

I've cast good boolits with zinc in the alloy, but I have to run my bottom pour a lot hotter than normal to prevent spout freeze and tails hanging from the spout. DALE

[Potsy]

I posted over on the zinc wheelweight sticky but didn't get a reply to my question. This pretty much answers it. Or at least, this is the conclusion I have came to:
Zinc in the alloy, while not the end of the world, will cause lighter, smaller dia. bullets.
It would help explain why I don't get the pretty, shiny, smooth, sized down driving bands all the way around on a lot of my Lyman 452424's when run through a .452 sizing die. Particularly when the mold and the alloy isn't REAL hot. For that matter, I've got a Lyman 358429, that after sizing and lubing the bullets in a .358 sizer, the bullets don't even look like they've contacted the die.
I'm going to have to run my pot out, clean it, smelt another batch of alloy and see what happens. Probably won't fool with that until winter though. I am excited at the prospect of having something to blame besides my sorry shooting!!!
I would heartily accept any additional input, opinions, or recommendations.

[docone31]

Fire up the pot, then cool it just untill the zinc floats on top. The melt will be liquid, and the zinc will be like porige.
Ladle out the zinc. What is left will be minimal. Next melt, crank the pot up and use it up.
There will probably always be some zinc in the melt. Keeping it to a minimum is an asset.
I once thought, zinc did not hurt. In small amounts, that might be true. True to form, I had a lot of zinc in one melt. I have since learned better.
I like to pour hot. To get my zinc out, I turned my Lee Pot to 6 and let it cool down. I stirred and let it sit. Eventually, the zinc floated and I could scoop it out.

[cbrick]

Fire up the pot, then cool it just untill the zinc floats on top. The melt will be liquid, and the zinc will be like porige. Ladle out the zinc.

Hmmm . . . What color is this floating "zinc"? Is it silver and look a bit lumpy like oatmeal? If so it sounds very much to me like you are removing antimony, not zinc. Assuming WW alloy this should be fluxed back into your melt at around 700 degrees, not removed. The difference in melting temps of WW (485) vs antimony (1150) can cause this lumpy antimony to form on top of the melt as the pot heats up.


I like to pour hot. To get my zinc out, I turned my Lee Pot to 6 and let it cool down. I stirred and let it sit. Eventually, the zinc floated and I could scoop it out.

Pouring HOT will not help get the zinc out, it will assure that you alloy the zinc into your alloy and not melt it out. That's exactly how the metals industry gets zinc alloyed with lead in the first place . . . HEAT! The way to aid in keeping zinc out of your wheel weight alloy in the first place is to cast at or below 650 degrees. Zinc melts at 787 degrees. Cast hotter than this and you are assured of alloying any zinc present INTO your alloy.

I have of coarse come across zinc weights in buckets full of WW but not nearly enough to float lumpy on top of the melt. Neither have I ever had the melt hot enough (while smelting WW into ingots) to alloy the zinc into the melt.

Perhaps you can get a few tips on alloys and melting temps from this article. Cast Bullet Alloys. (http://www.lasc.us/CastBulletAlloy.htm) Hope it helps.

Rick

[KYCaster]

Hmmm . . . What color is this floating "zinc"? Is it silver and look a bit lumpy like oatmeal? If so it sounds very much to me like you are removing antimony, not zinc. Assuming WW alloy this should be fluxed back into your melt at around 700 degrees, not removed. The difference in melting temps of WW (485) vs antimony (1150) can cause this lumpy antimony to form on top of the melt as the pot heats up.Rick


Rick, if this is true, how do you account for the fact that adding Sb to the alloy works best at lower temp.?

The method described to me by Bill Ferguson, The Antimony Man, involves temps in the very low liquidous range. I've found, from personal experience, that it works even better with the flux I use, at even lower temps, in the slushy stage.

I'm not a metalurgist, but I have worked with several of them and they often used Pb,Sn,Sb alloys as teaching aids because they have been well researched, are easily duplicated and are very predictable. Nowhere in any of the documented research have I ever read anything that would indicate that the individual components of a Pb,Sn,Sb alloy will seperate simply by changing the temp. of the alloy.

I have not seen any research concerning Pb,Zn alloys so I won't comment on that other than to say that I am currently having some issues with some range scrap. I have not yet had any of it alalyzed to see for sure if it Zn, Al, Bi or something else that's causing the problem.

Just wondering if you could shed some light on this for me.
Jerry

[cbrick]

KYCaster,

I'm not a metallurgist either but the majority of what I have learned of this has been from studying metals industry papers.

I didn't explain it very well I guess, I didn't say or mean to imply that simply changing the temp would separate the constituents, it won't. From a solid (cold) as the alloy heats to the melting point the lead melts first (this is the solidus stage), while the antimony is still slushy the antimony near the surface can cause this lumpy appearance. Skimming this off depletes the alloy of the antimony. Because of this is the reason I explain the difference of solidus and liquidus to new casters and recommend not fluxing until liquidus is reached. For me just in the interest of simplicity liquidus temp is full casting temp of 700 degrees.

The surprising part of this to me isn’t that it happens but rather it happens once in a while (for me), not never and not always, just every so often. I assume it has something to with how fast the pot heats up and how quickly both lead and antimony reach liquidus but again, I’m no metallurgist.

Rick

[leftiye]

If you are smelting "new" wheelweights into ingots, the zinc wheelweights won't melt below 785 degrees, so they float on top of the melt. Likewise when you remelt ingots or other lead with zinc in it, you will experience a mush stage after the solidus of the lead alloy is exceeded. This can then be skimmed off ( at say 650 degrees). As CBrick said other metals also produce a mush like this, copper and antimony being two.

[docone31]

Yeah, I saved the scooped out mush in the hopes of putting back whatever antimony came out with it.
However, the melt now seems ok.
I sure have a lot of zinc ingots though.
I am a dummy. Being a jeweler, people bring me junk jewelery. They just give it to me. I got perhaps 50lbs of "pewter" jewelery. I thought it was perhaps wheel weight poured into molds.
Wrong. It was mostly zinc.
I melted that batch into ingots, then mixed some of them into my pot melt.
Whoopsie. It did the whole thing, curdled up, and eventually plugged my pour spout. I had thought stirring might have been the answer. I had mushy lumps throughout my pot.
Reading threads on this forum, I turned the melt down to where it just kept the lead alloy soft. I then scooped out the curdle. Cranking the heat up again, it made great castings!
Good sizing, molds well, I guess I got a good batch. Next melt, I will crank the pot back up and cast most of what is left.
Hey, I am just trying stuff out right now, so a bunch of mongrels won't hurt.

[prs]

Some of us have yet another perspective. Zinc is sure not gonna help those of us casting for muzzelloaders or black powder cartridges. I've learned to get by with WW alloy in BP cartridges, but please no harder than that! So, I try to keep the zinc and other stray metals to a minimum.

prs