Zinc casting.

[Double D]

There is a discussion going on over on Cast Boolits on casting with zinc. Has anyone cast zinc bollits?

As usual in these type discussion there were the "I think posters" and the "I know posters".  Here's what I have gleaned from the I know" group.

I used to cast a lot of zinc bullets. I just sized and lubed with a wax lube, and used a target-level or midrange load for the as-cast weight. Works fine. I also used to pour a lot of zinc for other purposes, so I had a lot of experience with pouring zinc and had little difficulty. Like the commercial says-- your results may vary.

This is definitely a job for an iron mold. The melting point of aluminum has nothing to do with it. An aluminum mold with an aluminum sprue plate would almost surely be damaged severely quite soon-- not to mention the fact that zinc will readily stick to bare aluminum. In fact, molten zinc will aggressively and rapidly dissolve aluminum even though aluminum melts at a higher temp. The best way to start is to use well-fluxed zinc and a large caliber one-or two cavity mold, such as 44 or 45cal.

Anyone who attempts this should note that even the smallest splashed droplet of zinc will burn you such that you remember it for a very long time. All safety precautions must be observed strictly when working with molten zinc.

Best of luck!

Note that welding galvanized steel will actually burn the zinc and vaporize it. A similar risk is posed when alloying copper and zinc to form brass. If you've ever worked in a brass forge, you're seen that green/blue/whitish flame of burning zinc. That is the source of risk for 'metal fume fever.'

Simply heating and pouring zinc at normal casting temps does not expose one to risk of metal fume fever from volatilized zinc. As safe as, or safer than, pouring lead. Burning (vaporizing) lead runs similar or worse risks of toxicity, but lead kept at 'normal' pouring temps poses little risk of exposure to toxic vapors.

Just shining a little light on it. Keep on keepin on!

Editted the bullet shooting stuff out and left the cast infor

HI,
FOUND THIS:
GOOD CASTING ALLOYS OF ZN ARE ZAMAK/ZAMAC. But there are 12 diff. versions. Kirksite or zamak #2 has more Cu. In europe Zamac is called Mazak (made with a slightly different process). all 12 alloys are mixes of Zn, Cu, Mg, &Al.

They can be fluxed by Salicytic acid (asprin). Do not need a lot of fluxing.

...

May have to run alloy temp. to cast about 50* higher then melt temp. for good results. This means about 800-850*. Also avoid higher temp. as alloy will pick up Fe from pot.

Need spru holes25-50% bigger than for Pb casting. Don't let Spru completly harden as cutting gets VERY DIFFICULT.
 
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Will try to find more & post it.

HI,

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You want to preheat the mould to at least 400 degrees F.
you want to use the lowest temp. you can to get good bullets as higher temp. leads to cracks & poreosity. And the Zn will pick up Fe from the pot.

I think from what I could glean from the metilurgical engeneering sites that we want to get hypoeutectic alloys with less Al than 4%, & less Fe than 1%. so Zamak 2 might be best. It is used in gravity casting.
Zamak 3 is used in die casting, Zamak & is lower in Mg to increase fluidity of the alloy so it might be a good canadate too.

 

All Zamac alloys are much harder than pure zinc. Sprue cutting can be a real chore with Zamac.

Super hard is not what you want. Just scoot down to the local marine supply and buy a pure zinc anode in the size/weight you want. Anode zinc is easy to work with.

There's no secret trick to it, just melt the zinc and pour. Gotta keep the mold hot, but correct heat management is part of the process with both lead and zinc.

It would be interesting to read the source material, or some confirmation of the above statement.

I have zinc bullets cast many years ago, and they're still as as shiny and solid as they day they were cast--
in some very old Lyman 45ACP molds previously used with lead.

I posted a request for Boom Boom to share the links to the sites he refers to .

[GGaskill]

It would be interesting to read the source material, or some confirmation of the above statement.

I am guessing that this is referring to a comment that old zinc castings will disintegrate into a powder.  This was a known problem in some old diecast railroad models.  It turned out that the problem was caused by impurities in the alloy which caused internal corrosion.  It has been found that more accurately mixed metals do not have this problem.

It was also found that moulds and melting apparatus should be different for lead casting and zinc casting.  The zinc somehow contaminates the pieces and will not cast good lead bullets afterward.  This is probably not a serious problem with cannon size shot.