About tin rich alloys...

[Any Cal.]

Ok, I was getting ready to mix some lead, and began thinking about tin heavy alloys. The general argument is that anything over 2% free tin will precipitate, right? If this is a big problem, why did 16-1 work for Elmer? Wouldn't any alloy over 40-1 have the same issues, if they existed? If there are actual problems w/ tin rich alloy, will they increase w/ increasing amounts of free tin?

I have read of tin rich alloys soldering onto the barrel, but wonder if that is just a tale, as paper patches don't burn in the barrel, nor does all the lube burn off a boolit. Any input? I am wanting to do some experimenting w/ some alloy that is only 58% lead, but want any kind of a head start that I can get.

[KYCaster]

Are you talking about binary alloys or ternary alloys containing Sb?.....big difference.

Jerry

[Any Cal.]

Sb,Sn,Pb, with excessive Sn.

What is the difference if there is more than 2% free tin in either alloy?

[sqlbullet]

As I recall the 2% rule relates to the solubility of tin in antimony/lead, not in pure lead. That is the difference.

[Defcon-One]

Lyman #2 is a ternary alloy with 5% Tin. My 25:1 is a binary alloy with 3.8% Tin. Neither has been raining Tin out my barrels or in my pot?

Please explain more on this theory: "anything over 2% free tin will precipitate"?

Thanks,

DC-1

[sqlbullet]

Maybe I am wrong, but I think the OP has been confused (somewhat easy to do) by the myriad of threads talking about "ideal" alloys of lead-tin-antimony.

In binary alloys, as we all know, lead and tin are infinitely soluble. The will cool to an even distribution of lead-tin regardless of percentage. This means there was no precipitation of tin or lead from the alloy as it cooled.

In ternary alloys or lead-tin-antimony, this is not the case. Only a certain amount of antimony is soluble in lead, after which any remaining antimony precipitates during cooling, forming large (microscopically) globs of antimony in a lead block.

Tin mitigates this by binding with both the lead and the antimony, allowing higher concentrations in solution at room temperature. However, in accomplishing this single goal, there is a limit to how much tin is useful, and in general a rule of thumb is no more tin than antimony by percentage.

Additionally tin lowers surface tension and provides oxidation protection at temps below 750°. But, these benefits reach there maximum at 2% tin and any additional tin does nothing to further enhance castability.

Since WW alloy has typically in the ball park of 2% antimony, our rule of thumb would dictate 2% tin. Taken with the castability benefits of tin, we now have to reference points that indicate 2% tin is plenty for our needs.

However, I think what is missing here is that tin can provide other benefits beyond antimony solubility and improving castability of the alloy. Tin increases the malleability of the alloy, making bullets that will both expand and hold together.

With regard to the concern about tinning the barrel, I think we would all agree that this was most likely caused by undersized bullets. Gas blow by generates more than sufficient temperature to melt the sides of a bullet, heat the barrel and cause adhesion of the tin to the steel. It is facilitated further by the lube, which acts as a flux under these conditions. But, it is in no way common.

With regard to useing a 42% tin alloy for casting, I think you will be very disappointed. I have not personally tried this, but I have over 100 lbs of 60/40 bar solder on my casting bench, and another 100 lbs of pure tin. I got these in trade 3-4 years ago from a gentleman who had purchased over 1000 lbs at auction. He thought solder would work fine for bullet alloy and found otherwise.

He did not articulate to me his specific problems, but I suspect age softening was a big one. The more tin you have the faster the alloy will soften. It is also possible he was having issues with tinning if his bullets were not properly sized to his guns. I no longer have his contact information or I would follow up and ask, as well as offer to trade some more isotope lead for his solder. He was so anxious for lead we traded 1:1, and I would gladly acquire several hundred more lbs of solder at that exchange rage.

OP, I would suggest your read the following two articles:

http://www.lasc.us/FryxellCommentsCBAlloys.htm

and

http://www.lasc.us/CastBulletAlloy.htm

[Any Cal.]

Thank you for the effort put into the response. It is not a matter of being confused, it is a matter of trying to understand why tin rich ratios are always argued against, and if there are any valid reasons for that other than cost.

It was here http://www.lasc.us/Fryxell_Book_Chapter_3_alloySelectionMetallurgy.ht m that it mentioned a binary lead-tin alloy only having 2% soluble lead at room temp. I understood that to mean that anything over 2% would form at grain boundaries in the solid lead.

If that was the case, wouldn't excessive lead do the same thing in a sd/sn/pb alloy, as in anything not alloyed with sb or soluble at room temps forming at grain boundaries on cooling?

[Defcon-One]

Sqlbullet: Great info. and just what I thought. It looks like I can go on using my current alloys without worry about it raining Tin.

I also agree, I would not use high Tin alloys like 60/40 or 50/50 for bullets. They are too valuable and I use them in small quantities just to up my Tin content.

FYI: 2% Tin, 3% Antimony, 95% Lead is my favorite pistol/revolver alloy! I use Lyman #2 for Rifles with and without gas checks!

[Any Cal.]

Well, expense is not an issue, as it would cost considerably more for me to use less tin. I have an alloy that is 60% lead, 25% tin, 10% antimony. Most of my alloys are tin rich, so no matter how I blend it, high tin is the common denominator. Right now I am trying to understand the hurdles I may face by using tin rich alloys, if any.

[Defcon-One]

I would consider trading some of your Solder type alloys for Isotope Lead (I love the large cores) or COWW Lead. It is easy to do here, there is a steady demand for Solder, Linotype or similar alloys, and a large supply of other alloys to trade for, Isotope Lead, COWW, SOWW, and Pure Lead too!

You could get a lot of lead for just a bit of Solder. Probably something like a 5:1 trade in your favor, maybe even better.

That is something to think about!

[Any Cal.]

If I could trade for anything remotely close to that I would do it in a heartbeat. That alloy and some superhard could make a lot of #2 or similar. Problem is I have tried that and not gotten anywhere. Everyone wants alloy material, but no one wants to pay for it. So, I can shoot 25% tin for considerably less money than .5% tin when all is said and done. Now I am trying to figure out how best to do so.

I do know that the high tin makes for lighter boolits, and that it fins easily if a mold isn't perfect. I haven't shot any yet though, nor have I added lead to cut the percentages any. Trying to learn how the tin precipitation will affect things, but may just have to go shoot the stuff and find out.

[shadowcaster]

I can shoot 25% tin for considerably less money than .5% tin when all is said and done. Now I am trying to figure out how best to do so.

I have always been one to advocate keeping the tin ratios down to around 1% (add tin only as needed) as the majority of the scrap that I gather up has some tin in it already. Thus my tin/solder supply is low. You are fortunate to have such an abundant commodity at your disposal. While I cannot offer you any advice on this, I am very much interested in seeing your results of shooting the high tin boolits and if indeed you do end up cutting your mix with lead.

Sqlbullet: Great information!! :-) Well thought out, you made it very easy to make sense out of an often confusing issue.

Shad

[jmort]

"Sqlbullet: Great information!!"

I agree with all the praise for Sqlbulle's post.

[Any Cal.]

Alright, have had time to collect my thoughts. My post in blue below.


Maybe I am wrong, but I think the OP has been confused (somewhat easy to do) by the myriad of threads talking about "ideal" alloys of lead-tin-antimony. I am confused, but by the difference in opinion between popular belief and this page...http://www.lasc.us/Fryxell_Book_Chapter_3_alloySelectionMetallurgy.ht m

In binary alloys, as we all know, lead and tin are infinitely soluble. The will cool to an even distribution of lead-tin regardless of percentage. This means there was no precipitation of tin or lead from the alloy as it cooled. According to my understanding of this page, this is incorrect. Tin is only totally soluble at melting pot temps. As it cools to eutectic, it is only 19% soluble, and only 2% soluble at room temp. Anything over this amount precipitates out of solution.

In ternary alloys or lead-tin-antimony, this is not the case. Only a certain amount of antimony is soluble in lead, after which any remaining antimony precipitates during cooling, forming large (microscopically) globs of antimony in a lead block. This is the same thing that happens to tin, except only .44% antimony is soluble in lead at room temp, according to my understanding of the above page. The only difference a ternary alloy makes is that the Sb and Sn will bind in equal parts, so the amount of free element in the lead is reduced.

Tin mitigates this by binding with both the lead and the antimony, allowing higher concentrations in solution at room temperature. However, in accomplishing this single goal, there is a limit to how much tin is useful, and in general a rule of thumb is no more tin than antimony by percentage. This is the rule I am trying to understand. Tin and antimony bind to each other in equal amounts, but why wouldn't any additional tin behave just as it would in pure lead?

Additionally tin lowers surface tension and provides oxidation protection at temps below 750°. But, these benefits reach there maximum at 2% tin and any additional tin does nothing to further enhance castability.

Since WW alloy has typically in the ball park of 2% antimony, our rule of thumb would dictate 2% tin. Taken with the castability benefits of tin, we now have to reference points that indicate 2% tin is plenty for our needs. Plenty, but is there a danger in using too much, other than cost?

However, I think what is missing here is that tin can provide other benefits beyond antimony solubility and improving castability of the alloy. Tin increases the malleability of the alloy, making bullets that will both expand and hold together.

With regard to the concern about tinning the barrel, I think we would all agree that this was most likely caused by undersized bullets. Gas blow by generates more than sufficient temperature to melt the sides of a bullet, heat the barrel and cause adhesion of the tin to the steel. It is facilitated further by the lube, which acts as a flux under these conditions. But, it is in no way common.

With regard to useing a 42% tin alloy for casting, I think you will be very disappointed. I have not personally tried this, but I have over 100 lbs of 60/40 bar solder on my casting bench, and another 100 lbs of pure tin. I got these in trade 3-4 years ago from a gentleman who had purchased over 1000 lbs at auction. He thought solder would work fine for bullet alloy and found otherwise.

He did not articulate to me his specific problems, but I suspect age softening was a big one. The more tin you have the faster the alloy will soften. It is also possible he was having issues with tinning if his bullets were not properly sized to his guns. I no longer have his contact information or I would follow up and ask, as well as offer to trade some more isotope lead for his solder. He was so anxious for lead we traded 1:1, and I would gladly acquire several hundred more lbs of solder at that exchange rage.

OP, I would suggest your read the following two articles:

http://www.lasc.us/FryxellCommentsCBAlloys.htm

and

http://www.lasc.us/CastBulletAlloy.htmThank you, I had already read these, but they don't have the information needed for a solid answer to the question as far as I can tell.

[sqlbullet]

Hence the confusion.

You are right. We can both site the LASC site and come up with both the answer that lead-tin is infinitely soluble (with no mention of temp) and that the solubility varies with temp.

While I accept that there is large particle formation as lead tin alloys cool if the percentage of tin is above 2%, it has no practical meaning for our purpose since additional tin does continue to harden, up to 40% or so, and quenching does not change this fact, since quenching does not prevent the formation of large particles.

As I said before, I don't know about any dangers in using high tin alloys other than to your wallet. I am aware of at least one person, as I mentioned, that was not happy with the results of using either pure tin or solder for bullet casting. I do not know the specifics of his concerns. And since I don't have deep pockets I don't plan on squandering my tin to find out. The articles we have both read give repeated reasons not to use more than 2%.

If you have tin rich alloys, it will be trivial for you to use them to obtain lead. Head to your nearest LGS that has a decent reloading section and put a card on their bulletin board. Or advertise here. Plenty of guys will trade you at very advantageous rates lead:tin.

[Any Cal.]

Well hmmm.. guess that puts me back at square one. I was hoping one of us could be positively correct, so I knew which way to play it. Anybody want to weigh in w/ guesses?:-)

[Larry Gibson]

As I recall the 2% rule relates to the solubility of tin in antimony/lead, not in pure lead. That is the difference.

That is correct. In 50/50 solder (50% lead/50% tin) the extra 48% tin does not "precipitate", it stays mixed in solution with the lead. Suggest a read of the "Metallurgy" articles in Lyman's #3 & #4 Cast Bullet Handbooks for a better understanding of how tin mixes with antimony for better solubility in lead up to a certain percentage. The article are an interesting read though a bit dry........

Larry Gibson

[runfiverun]

when antimony is present in the alloy the tin is more attracted to it than the lead.
if there is leftover tin it tries to rebond with the lead as the alloy cools it however does not have time to do so.
this means there is free spots of tin in the alloy which are surrounded by unalloyed lead.
causing hard and soft spots.
you can quite often see this appear as dark circles on the surface of the alloy.

if you can find them I have seen pictures of how free tin will glob up and flow on the surface of a lead boolit/ingot whatever.
that shiny surface tin is famous for is this happening where everything goes reflective smooth but it isn't a continuous surface the edges are rounded off from surface tension and the globs are on the surface and not part of the alloy itself.

put a torch on the alloy you have and see it sweat tin before it melts.
that is what is wrong with high tin [over tinned] alloys.

[Any Cal.]

I found a phase chart for the lead-tin alloy. Tin solubility in lead IS temp dependent. It would be nice if someone who could read the time/temp diagrams could chime in, as it has been years since I had a shaky understanding of them. Chart is here http://books.google.com/books?id=TL4j-jDXsk0C&pg=PA332&lpg=PA333&ots=4vDIvoQU-_&dq=solubility+of+tin+in+lead&output=html_text As best as I can tell, the first 2% of tin will go into solution, then anything beyond that will become a solid mechanical solution as the tin migrates to the grain boundaries, and the tin/lead globules just get larger with increasing amounts of tin. This is at room temp, at higher temps the tin is very soluble in lead.

Have to keep looking for Sb alloy info later.

-Edit- Here is a sb/sn diagram. https://sites.google.com/site/atdinsdale/sb-sn It appears that there is a big difference in structure between sb/sn and sn/sb, with a fairly narrow range not having any structure labeled.

I found a sb-sn-pb ternaryphase diagram but lost it. A readable diagram would be helpful.

-Edit- Here is too much info on some ternary alloys and various cooling rates, but they are all Sb rich. Lots of info and micrographs.http://www.doc88.com/p-074650022522.html Can anyone explain how fast the Δt rates are in °F?
.

[hickfu]

Wow, I wish I had some of that alloy..... I could use a little to up the tin and antimony of my existing alloy.

You could probably trade some of it to someone that has pure lead and mix it 25% your alloy to 75% Pure Lead and get a pretty good mix (a bit on the high side of Tin but still ok) If you had 100lbs of it and mixed it will 300lbs of pure you would have an alloy of 91.1 lead, 6.33 tin, 2.53 antimony... Add 1lb of bismuth from Rotometals and you are golden... Well I would be if I had that alloy.

Doc

[cbrick]

Chapter 3, pages 28, 29, 30 discusses the percentages and temps that tin is soluble in Pb/Sn and Pb/Sb/Sn alloys.

From Ingot To Target (http://www.lasc.us/Fryxell_Book_textonly2.pdf)

Rick

[303Guy]

I have a ready source of pewter and therefore am interested in tin rich alloy. I've found that too much tin makes for really bad casting from my bottom pour. I found some of my Babbit (or was it lino?) and made up a new mix and that casts well and has a 'hazy' surface appearance making for easy identification. It is very 'porridgy' as it freezes making for real easy sprue cutting. It hardens quickly as it cools and water quenching makes it pretty hard for me. It does have some copper in it and this makes me wonder whether you should be trying the addition of copper - perhaps 0.5%, maybe more just as a test, maybe less.

On gas cutting - only the thin layer the escaping gas contacts is heated which is why it cuts or erodes it so effectively.

[Any Cal.]

Well, my stuff has copper in it already. I had cast a few with it, and it was difficult to work with, but did get a few boolits. It wanted to let the alloy out of solution badly. I think if I cut it a bit w/ lead it will be OK. After looking at all the info I can find, there seems to be no good reason not to run high tin. My current hypothesis is that the high tin a) will make the bullets quite hard compared to the same alloy content w/ less tin, and b) the hardness varies a bit over the first week or two after casting due to age hardening and age softening happening in various elements of the alloy at the same time.

[Any Cal.]

I cleaned out my pot and ran 2 lbs of the high alloy and 5.5 of 40:1. It should give about 11.6% tin and 3.6% Antimony along with a smattering of copper, bismuth, and zinc...less than .5% each.

The alloy cast extremely well, but had to be run very hot. I had to slow down to keep my Lee 2 cav cool enough, even though I am only using one cavity. About 2-2.5 pours per minute. Running the alloy cooler gave lots of defects. The sprue would go from very soft to brittle hard very quickly, but stayed soft for a while due to the hot mold.-Edit- Old aloy cast at 255g, this alloy cast at 245, Lee 250g mold.

Sizing the boolits .010" for paper patch had me seriously wondering which part of my Lee Challenger press was going to give way, and it bent the boolits badly. (.379 250g). I have swaged ac scrap lead from .402 to .370 in one pass w/less force.

Sizing down a thou or two in the Lyman 45 was no major issue, but it was obvious the boolits were harder than my normal wd range scrap. I don't have a hardness tester to give any #s.

Will shoot some in the next few days and see what they do.

[badgeredd]

If I had the metals you have, I'd consider seriously buying some Superhard (high antimony) lead and using it to balance the alloy and bring the SB Sn ratio closer to 1:1. Also some pure lead in conjunction will alloy you to bring your alloy more in lines with Lyman #2, 90-5-5. You'll have a much better and consistent alloy for general purpose shooting. Too much free tin will definitely cause you problems (in the presence of antimony) with hardening consistently, air cooled or water dropped.

Edd

[Any Cal.]

I have considered the Superhard, but it adds $.30/lb plus to the cost of my lead. Alright if I must do it, but better is getting by without it...:-) Perhaps if I was working with a larger lead stash it would be more important.

I shot 12 .375 250g boolits w/ the mixed alloy mentioned above. Lubed w/ Tac1 there was no lead anywhere in the barrel. Chrono'd at 1992fps avg for 4 rds. After shooting the barrel was still shiny like I just finished shooting paper patched boolits. I can't speak to the accuracy as I am using a mold w/ serious issues, but at least I know the world won't start spinning backwards if there is more tin than Sb, at least in the alloy I currently have.