Ideal temp for smelting? zinc question too?

[Brother_Love]

I need to do a batch of smelting. I have WW, dental xray lead, industrial counterweights and a small amount of range scrap. What is the ideal temp to keep all the elements together? I am fluxing with beeswax.
Thank you.

Unfortunately I have about 200 lbs someone gave me but I think it is contaminated with zinc. Is there a "home remedy or test" I can use to find out. I would not want to mix it with my other ally if it is tainted.

 

[Rick]

Brother, Beeswax while a great reductant is not a flux, cannot do anything to clean your alloy. This process is explained precise easy to understand detail in the Book "From Ingot to Target" by Glen E. Fryxell. I highly recommend reading the entire book but chapter 4 is specifically on fluxing bullet alloy.

From Ingot to Target (pdf version)
From Ingot to Target (HTML version)
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[Brother_Love]

Thanks, already read that chapter and I read the whole book tonight and tomorrow night. It answered a lot of my questions about zinc too.

 

[Rick]

A very short list of Glen's accomplishments are, PhD in chemistry, Chief Scientist - Pacific Northwest National Laboratories, author of numerous books in his field, an ever growing list of citations from his peers. I discovered many years ago that when Glen speaks to sit back and pay close attention. Or in short . . . His book is a gold mine for casters.
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[Ian]

Hydrochloric acid is supposedly a test for zinc, I haven't tried it. Sulfur flowers crushed up and added to a large frying pan full of alloy that is carefully maintained at the grainy mush phase, stirred all together until the sulfur has all burned off and then heated to liquidus and the slag skimmed will remove zinc, but it is really quite a dangerous and unhealthy process for any breathing creature within several hundred yards, and isn't too great for the atmosphere, either.

I like to keep my ternary alloys around about 650°F when cleaning/fluxing/reducing. This seems just hot enough to get the sawdust to do its thing, and not so hot that zinc or Zamak WW melt in right away. I use sawdust or wood shavings to flux and reduce oxides, and save my beeswax for bullet lube. When processing soft lead scrap like shower pans, soil stack boots, lead roof flashing, clay pipe joint lead, etc, I usually have to go a bit hotter, like 700-750.

 

[Brother_Love]

I like to keep my ternary alloys around about 650°F when cleaning/fluxing/reducing. This seems just hot enough to get the sawdust to do its thing, and not so hot that zinc or Zamak WW melt in right away.


So, I might end up with mostly pure lead but it can be salvaged?

 

[Ian]

Doing as I described in the first paragraph will yield mostly zinc sulfate dross if used with alloy which has already been contaminated with zinc. The balance afterward will be whatever else was in the mix (tin, antimony, etc.), for the most part. The sulfur treatment won't necessarily remove the other metals as far as I understand it, and my results based on hardness testing support that.

My second paragraph was a description of how I keep zinc items that are accidentally added to the "smelting" pot from melting and contaminating the alloy in the first place.

Honestly, unless I was desperate for metal, I wouldn't do the sulfur treatment again. I've managed to get rid of some zinc contaminated alloy by casting it all in to .45 ACP bullets and paper patch cores (have to dial up the pot temperature quite a bit, like 750°F or more) and shooting it up at a public range.

 

[Rick]

Brother, what Ian was trying to say with smelting at 650 degrees is that zinc melts at 787 degrees. If your melting down wheel weights and your not sure if there are any zinc weights and your pot is 650 they won't melt, they will float to the top. Everything else in the alloy will be at full liquidus at 650 so if it floats scoop it out. Fluxing with sawdust will reduce the Sn oxides back into the melt and help remove any any Ca, Zn or Al impurities.

This won't work if zinc is already blended into the alloy but will keep zinc weights from melting. If that's the case Ian's suggestions are the things to try or if your sure zinc is in the alloy just not use it. You are correct though, don't blend it with known good alloy.
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[Rick]

So, I might end up with mostly pure lead but it can be salvaged?

No, that would be impossible. Once blended Sn, Sb & Pb are blended forever with the equipment and means of a home caster. It's possible to deplete (reduce) Sn or Sb percentages but not nearly to pure lead.
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[Ian]

Zinc wheel weights aren't pure zinc, they're an alloy (probably one of the better-casting Zamak varieties), which melts at something less than 787°. That's why I try to keep my rendering pot temperature not much higher than 650°.

 

[Brother_Love]

Thanks. I will reserve it for the fishing weights.