over cooked lead?

[Shadow9mm]

Trying to understand some things. I am working with an unknown alloy of around 13bhn. I have been melting the lead down over a coleman camp stove, fluxing, and pouring into ingots. Last time it was taking a while for the ingots to cool in the mold and when I dumped them out of the mold they kind of slumped and tore showing what appeared to be fibers.

In my recent reading It appears that if you get your alloys too hot it can cause the tin and or antimony to oxidize. It is possible that I over cooked the lead and rendered it closer to a pure form by oxidizing off the tin and or antimony?

I think I may have been running my lee pot too hot as well. I used to crank it to max until it melted then back off to around 7. After getting my lead thermometer this appears to be over 1000F. I am currently running it around a 3 to get around 700F.

How can I tell if I over cooked this lead? If I did over cook it can I just treat it as pure and re-alloy it? Would an extended cook at high temp be a good way to de-alloy lead and get pure if needed?

Trying to make sure I am doing things properly going forward.

[bangerjim]

AT 1K°F you most certainly could have "cooked off" the Sn and Sb! Now that you know to get it down to 730-760°F you will not lose much. That is why you use beeswax as a reducer in your casting pot to reduce those two valuable metals back in.

If you were at 13 hardness, you had some serious amounts of Sb in there. It may still be there, but you can pretty much guess most of the Sn is gone. Did you save the sludge you skimmed? That is where all the Sn is! Bring it back up to ~750°F and let it render out.

One thing you can do is preheat ALL your feed ingots to just about 10-15°F below the liquidous temp of your alloy. That saves lots of cycling time when loading them in your casting pot. Also, pre-heat ALL your molds on that same plate to full casting temp be ever starting. No perching the mold on the edge of the pot or dipping the end in the Pb any longer!

I get perfect drops from the 1st batch by doing that.

Just watch your re-melting and casting temps and stay within the published guidelines for Pb alloys we use.

[JimB..]

Be assured that the only thing that comes out of your pot is what you take out. Tin in particular will oxidize at the surface, but I believe that the layer of oxides then protects the rest of the pot. If you stir it up and scrape it off, maybe you can reduce the percentage of tin significantly, but you gotta work at it.

Assuming that you did just that, well throw it all back into your smelting pot and flux with some wood chips and wax, I bet it’ll be fine. See how it casts, then go from there.

[centershot]

Yikes! 1000*!? For sure you've ruined it, send it to me for proper disposal and start over with fresh material!

[Shadow9mm]

Be assured that the only thing that comes out of your pot is what you take out. Tin in particular will oxidize at the surface, but I believe that the layer of oxides then protects the rest of the pot. If you stir it up and scrape it off, maybe you can reduce the percentage of tin significantly, but you gotta work at it.

Assuming that you did just that, well throw it all back into your smelting pot and flux with some wood chips and wax, I bet it’ll be fine. See how it casts, then go from there.

The lead is coming from a bad batch of hi-tek coated bullets. I am melting them down and re-casting them. I typically heat on a coleman stove until molten, then back the temp down, not sure how much yet, have not done it since I got my thermometer. I scrape off the coatings from the top straining the liquid metal back into the pot, then flux and scrape off the rest of what came to the top. After cleaning there is just generally the light flakey burnt up coatings along with a very small amount of metal, maybe the size of 1 quarter worth or less for about 6lb of lead. and that is just want I was not able to strain out.

[JimB..]

The lead is coming from a bad batch of hi-tek coated bullets. I am melting them down and re-casting them. I typically heat on a coleman stove until molten, then back the temp down, not sure how much yet, have not done it since I got my thermometer. I scrape off the coatings from the top straining the liquid metal back into the pot, then flux and scrape off the rest of what came to the top. After cleaning there is just generally the light flakey burnt up coatings along with a very small amount of metal, maybe the size of 1 quarter worth or less for about 6lb of lead. and that is just want I was not able to strain out.

Sounds fine. Try casting with it, if the fillout is poor then add 1 oz of pewter.

[JonB_in_Glencoe]

you alloy is fine.
you don't need to get the melt that hot, obviously...but you didn't hurt anything.

When processing/cleaning/smelting alloy and pouring lots of ingots, I cool the ingot molds on a water soaked old beach towel. That solidifies even the hottest ingots in 10 or 20 seconds.

[45_Colt]

Be careful of going too hot, when the lead starts to vaporize it is an easy way to get too much into you. Not a good thing.

45_Colt

[Rickf1985]

1,000 degrees is the vaporization point of lead and you do NOT want to breath that. Lead casting is safe as long as you do not get it that hot and there is no reason to ever get hotter then 750-800 degrees. If you keep it at 700 or below you will also not have to worry about zinc because zinc melts at 750.

[turtlezx]

doubt your thermometer is correct for 1k

also 3 setting on a lee pot for 700* unlikely

[bangerjim]

1,000 degrees is the vaporization point of lead and you do NOT want to breath that. Lead casting is safe as long as you do not get it that hot and there is no reason to ever get hotter then 750-800 degrees. If you keep it at 700 or below you will also not have to worry about zinc because zinc melts at 750.

Actually, Pb boils / vaporizes at more like 3,100°F. You could never get a Lee pot hot enough to vaporize lead, so don't worry about Pb vapors. Just do not ingest it or eat after handling it, especially white oxidized Pb ingots. And the white PbO2 dust can be inhaled.

[Rickf1985]

doubt your thermometer is correct for 1k

also 3 setting on a lee pot for 700* unlikely

#3 on my Lee pot will give me 700 or above at times. It is very inconsistent. That is why I went with a PID on it. I still have the original Lee thermostat hooked up but I leave it set at 7 so if something happens to the PID it will limit the upper reach's of the lead temp. A Lee pot, unregulated, can glow red. And a PID can fail, my temp probe failed and the PID went into full heat mode.

[Rickf1985]

Actually, Pb boils / vaporizes at more like 3,100°F. You could never get a Lee pot hot enough to vaporize lead, so don't worry about Pb vapors. Just do not ingest it or eat after handling it, especially white oxidized Pb ingots. And the white PbO2 dust can be inhaled.

So why do all of the experts (the real ones with degrees) say that once lead reaches 1,000 degrees it becomes dangerous due to fumes?

[JonB_in_Glencoe]

Lead "Fumes" at 1000 deg f
Nope! not possible.

[bangerjim]

So why do all of the experts (the real ones with degrees) say that once lead reaches 1,000 degrees it becomes dangerous due to fumes?

If you don't believe JohnB or me, just do some research on the net. So simple to do. Any site you look up on metallurgy will list Pb as boiling at 3100F. It will not fume at 1K. It's a scientific physical fact. The experts you are listening to probably have degrees in basket-weaving, psychology or family studies. Or just like to listen to themselves talk on Youtube, like they all do.



PS.....I have a 4-year (+2 more) degree in REAL engineering!

[Rickf1985]

Not arguing, just looking for the real truth. I have always been told and heard, long before the internet, that 1,000 degrees was the limit. Above that you were running into fuming issues. I have seen it mentioned on here probably a hundred times and nobody has ever disputed it in the past, that is why I went with it and asked.

[JimB..]

Not arguing, just looking for the real truth. I have always been told and heard, long before the internet, that 1,000 degrees was the limit. Above that you were running into fuming issues. I have seen it mentioned on here probably a hundred times and nobody has ever disputed it in the past, that is why I went with it and asked.

Might as well argue, who knows, you could be right.

You get vapor long before you get anything like a rolling boil.

Not sure that anyone would believe data from a university, but for what it’s worth https://oem.msu.edu/images/annual_re...ading-sept.pdf

[Mitch]

Just a few things I have found along the way that might be useful.I do not use a thermometer much anymore.I like to clean or alloy lead at about 700 to 750. Neither bees wax or sawdust will instantly burstinto flames when added to the pot.If I get instant flames I let the pot cool and try again.This just seems to work for me in telling if i am to hot.

[PBaholic]

Trying to understand some things. I am working with an unknown alloy of around 13bhn. I have been melting the lead down over a coleman camp stove, fluxing, and pouring into ingots. Last time it was taking a while for the ingots to cool in the mold and when I dumped them out of the mold they kind of slumped and tore showing what appeared to be fibers. In my recent reading It appears that if you get your alloys too hot it can cause the tin and or antimony to oxidize. It is possible that I over cooked the lead and rendered it closer to a pure form by oxidizing off the tin and or antimony?I think I may have been running my lee pot too hot as well. I used to crank it to max until it melted then back off to around 7. After getting my lead thermometer this appears to be over 1000F. I am currently running it around a 3 to get around 700F.How can I tell if I over cooked this lead? If I did over cook it can I just treat it as pure and re-alloy it? Would an extended cook at high temp be a good way to de-alloy lead and get pure if needed?

Trying to make sure I am doing things properly going forward.

Nope, you're good. You can't overcook it in a Lee pot. When the alloy slumps and you pull on it, you are seeing the partially crytsaline structure of the alloy.

Just realize that every time you melt an alloy containing Antimony, that some of it comes out as drose. That is why many people believe in fluxing, to try and get that Antimony back in. The problem is most people flux incorrectly. If the drose stays on the top of the melt, it will never combine back into the alloy. Antimony will dissolve into a lead based alloy, but it must be without any oxygen, so it MUST be submerged.

Old timers used to use pine sawdust as a flux. The resin in the sawdust was a good flux, and when you stirred in the sawdust, it attached to the drose, and got pulled down into the pot.

I've since given up on fluxing, as I don't care all that much about hardness. I Powder Coat, so the hardness needs to be above 8 or so. I keep my drose, and refine it back down into mostly antimony, and then combine it back into pure lead, with a little pewter to add tin.

You should think about getting a thermometer that covers 450 to 1000 degrees, as it comes in handly.

[45_Colt]

As for lead vapors being created at lower then boiling point... Does water need to boil in order to evaporate (creating water vapor) and go into the atmosphere?

45_Colt.