Did I Screw Up?

Mike W1

Active Member
First off, partial quotes from another thread.
"fiver
when I first got mine it wouldn't go over 615*
perfect for mixing antimony in the alloy, and fine for ladle casting.
Ian
It isn't really melting, just dissolving into the molten lead. Tin helps it dissolve.
fiver
antimony ore will melt into lead at around 600-625-F.
the trick is to break down the surface tension and patience.
I have done it with marvelux and wax."

Mixed up an alloy last week hoping to get something in the range of Pb 96%, Sb 2.5%,Sn 1% range. I do realize those don't add up 100%!
What I came up with was close. EXCEPT!!! I sent 2 samples off and one had 6.7% Sb and 1.1% Sn. The other was close to my guess.

So I finally did what I should have long ago and checked the melt point of RotoMetals SuperHard which is 745°. Like a knothead I can be I kept my temperature at less than 700° through out the process. Melted the lead, fluxed with stearine, added the SuperHard, and stirred till I could no longer feel any lumps. Fluxed again, and then added the Sn and fluxed again with the Stearine and of course much stirring throughout the process.

I feel that the amount of stirring I did was more than sufficient but am now wondering if keeping the temperature of the melt that low may have been a big blunder.

Could that small sample (bb sized) have been some Sb that really didn't get into the alloy?

Gentleman that ran the test normally presses the samples before he runs the test and he said he felt one sample compress differently than the other. I've tried to do some comparisions with samples off those 2 particular ingots as well as a number of others from that batch. I do remember when I cut the pieces for the original samples that one was hard to cut than the other was.

So after the long way getting here, should I just remelt the whole batch? There's no way those metals had over 6% Sb in them.

Appreciate any thoughts on this!
 

popper

Well-Known Member
I cast my superhard in an old mould. Known weight! Your sample size is pretty small (BB?). I always let my mix cook for an hour and stir well, usually run the pot @725. Part of alloy could separate if near liquidous temp but not probable - but if the sample is taken off the top it would be mostly tin (if near liquidous temp). No idea what Stearine is, just use wax.
 

Rick

Moderator
Staff member
I too have no idea what Stearline might be. Given that a wax, any wax is not flux I stick with sawdust which is both a flux and a reducer. All of the Super Hard I've blended was done at my normal casting temp of 700 degrees. Never an issue of any kind, it will melt and blend with the alloy.
 

Mike W1

Active Member
Stearine is what we used to use working with lead in the TELCO splicing business. That was about what I knew and no more but it was explained thusly in an old thread on here.
"Stearine is a tryglyceride derived from beef tallow. It's a sacrificial reducant, same as NEI's rosin.
So they both fit into the reducant category, not the adsorbent flux category occupied by woods and borates."
 

Brad

Administrator
Staff member
Stearine sounds a lot like stearic acid or something similar. Think a true soap, like Ivory.
it would work as a reducing agent.
 

Ian

Notorious member
The soaps are metal salts resulting from the fatty acid/metal hydroxide chemical reaction. Soap doesn't make a very good flux or reducant but does make a stink and black tar coating inside the furnace. Stearic acid is also called strearine iirc, works fine for reducing oxides by providing hydrogen and carbon to the redox reaction.

Antimony will fool you. It breaks down into mushy granules and if you don't keep the oxygen off the top while it's melting/dissolving in it will get coated in its own ixide and there you're stuck. Heating it and keeping a layer of ash on top for a long time will get the antimony to settle in. It took me a week of heating, stirring, reducing, and heating some more omto finally get the pure antimony I had to fully alloy with my soft scrap. After that I just buy the Rotometals Superhard pellets, dump them into the pot and stir while fluxing with resiny yellow pine sawdust.
 

Mike W1

Active Member
The point is I guess do you think I'll have to heat that batch up past 745° for that Sb to fully alloy? Or is it probably already "settled in". XRF results I got would make me think it is.
 
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Rick

Moderator
Staff member
It most likely is fine. The problem with Sb is initially getting it to blend with Pb. The entire purpose of Roto Metals Super Hard is that the professionals have already done that for you. Super Hard is an alloy of lead and antimony already blended, by using it you are merely diluting the concentration of Sb to suit your needs. No need to over think it, you'll be fine with it.
 

Brad

Administrator
Staff member
Antimony will fool you. It breaks down into mushy granules and if you don't keep the oxygen off the top while it's melting/dissolving in it will get coated in its own ixide and there you're stuck. Heating it and keeping a layer of ash on top for a long time will get the antimony to settle in. It took me a week of heating, stirring, reducing, and heating some more omto finally get the pure antimony I had to fully alloy with my soft scrap. After that I just buy the Rotometals Superhard pellets, dump them into the pot and stir while fluxing with resiny yellow pine sawdust.
So true!
i fight to get monotype to mix in really well all the time. It requires lots of sawdust for reduction and lots of stirring. I find I need to flux 3-4 times as much as when adding a lower Sb alloy.

I would keep reject the mix, stir a bunch, then add lots of sawdust on the surface. Let the sawdust begin to smoke then ignite it. Stir a bunch while the flames are lit. If you still see anything other than ashes on a smooth, shining surface then repeat until you do.

Time, agitation via stirring, and a low, smokey flame are your friends here. Reducing the Sb back in takes some time so don’t rush it.
 

fiver

Well-Known Member
I'm sure we have all seen the grey foam, or some lumps [kind of makes you think you got zinc] or an alloy just be weird for no particular reason.
most all of that is generally antimony being stupid, it gets an oxide layer on the surface and just won't cooperate.
quite often just turning up the heat and giving it some incentive to break that oxide barrier is all it needs.
other times the alloy needs diluted and then re-mixed back to what you want.

usually adding in something like the super hard, lino-type, or whatever is nothing more than dumping in the chunks and letting them melt, give the pot a 10 second whirl, scrape off the gunk while the alloy temp comes back to normal and go.
 
F

freebullet

Guest
No expert but, I dial up the temp when alloying. Little chain saw dust stirred in a few times seems to work quickly. Once it gets to 8-900 you can watch the oxides precipitate back into the melt with no flux. Almost self stirring.
 

popper

Well-Known Member
I just use craft store beewax for fluxing and alloy is all Roto. No tin and only get a little crinckly looking on top when i toss the sprue back in. Touch the wax chunk onto the surface, then let it burn. When finished, touch the chunk back in and let it cool with the alloy. Yes, I mix my alloy in the casting pot.
To the OP. ? - mixed a single pot, poured into ingots, sample from 2 ingots for testing and they are different? If true, re-melt the entire batch, flux and stir, cook at temp (700+ but NOT 900) for 1/2 hr.
 

Mike W1

Active Member
I chatted with someone on RotoMetals but they don't have a tech dept so were unable to be of any real help. My inclination is to leave things as are. Figure on the high Sb reading it probably was an unlucky little lump and being that the sample size's were like a fat BB it wouldn't take much. By the time I was ready to pour the ingots the surface was perfectly smooth and clean. Feel confident the Sb wasn't separating out anyhow. Alloy is for my 1911's and I've not had any problems with the last batch which was of similar composition. Besides I'm thinking I'm not that great a handgun shot that I'd ever be able to tell any difference if there were any. BUT, if I ever do this again I'm going to raise the temperature of the melt to above 750°.
Thanks for the insight fellows.
 

Mike W1

Active Member
Gotta love the web sometimes. Was fooling around with my crude searchs on Google tonight and found something of interest to me. Of course Binary alloys don't melt at a specific point but found a couple charts on 2% Sb and 98% Pb and another of 1.5% Sb that show the melting points of those alloys fall between 486-650°. A wide range naturally but falling in the area of where I kept my temperatures. I was at 650-700° so chances are I lucked out!
 

Ian

Notorious member
Note that the context of my post that you quoted about antimony is not in the same context as Superhard. Don't get the two confused, Fiver and I both were referring to PURE antimony. Once antimony is alloyed with some lead and/or tin, gettng it to alloy with anything else is much easier.
 

Rick

Moderator
Staff member
Note that the context of my post that you quoted about antimony is not in the same context as Superhard. Don't get the two confused, Fiver and I both were referring to PURE antimony. Once antimony is alloyed with some lead and/or tin, gettng it to alloy with anything else is much easier.
Exactly . . . That's the point I was trying to make and is the reason for Super Hard. Let the professionals deal with the hassle getting Sb to blend initially with lead and also the toxicity of pure Sb.

It most likely is fine. The problem with Sb is initially getting it to blend with Pb. The entire purpose of Roto Metals Super Hard is that the professionals have already done that for you. Super Hard is an alloy of lead and antimony already blended, by using it you are merely diluting the concentration of Sb to suit your needs. No need to over think it, you'll be fine with it.
 
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Ian

Notorious member
Yup, that's what Mike was using and what I use now, I was just pointing out that he started this thread off with a couple of out-of-context quotes about trying to alloy with pure Sb chunks and that doesn't really mean much to what he's doing since he's using Superhard already.
 

Rick

Moderator
Staff member
As I understood the original post in this thread he was using Super Hard and not pure Sb. Guess I could have read it wrong but that's how I interpreted the post, that's how I replied. Roto Metals has done a tremendous service to casters by offering us Super Hard because it eliminates many problems, makes life much easier and safer.
 

Bisley

Member
Did I just luck out then?

As a teenager I ordered a 55 pound ingot of pure antimony from Art Green in California when I started casting. I formed about thirty pounds of it into half-pound ingots using Dad's plumber's furnace. For health and safety reasons I would not recommend this (Did everyone read TEENAGER?). In any case, the half-inch of depth I could not reach at the bottom of the pot I alloyed with some leftover scrap and it performed all right.

A few years ago, I located two of those pure ingots and put them into a Lee pot I wanted to harden up. I simply let them float atop the molten alloy with the 20-pound furnace on its highest setting and poured alloy over them until they dissolved. The bullets cast, sized, and shot okay, with no signs of leading. There's no way the Lee electric pot got to 1200 Fahrenheit to melt the antimony. But I have not encountered the situation Ian described where antimony will "fool" you.

Comments? Responses?
 

RicinYakima

High Steppes of Eastern Washington
You don't melt sugar in your coffee either. Antimony dissolves in lead, which is why you can't do it fast. If you chunk it up, it will dissolve faster.
 
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