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Thread: Toughness Of Lead-tin-antimony Alloys

  1. #21
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    Quote Originally Posted by Ricochet View Post
    Thanks for the clarifications, Grumpy! I'm really looking forward to your further reports!

    As for antimony/tin ratios, looking down tables of type metal compositions it seems there are a lot of 2:1 or 3:1 ratios.

    I've read that arsenic is put in shot to make it round up better while falling in the shot tower. That sounds to me like something that increases surface tension, likely not something we want a lot of in our boolits.
    Nearly all typemetals are hypereutectic on antimony: they have more than 12% antimony. Hypereutectic alloys seem to act rather differently from hypoeutectic alloys, which are what we use for making cast bullets. As Weaver pointed out, hypereutectics consistently increase in hardness with increasing tin content, whereas hypoeutectics may not in some ranges. Prior to about 1934 only the pseudo-binary eutectic (10/10 in my notation) had been discovered; the low-tin eutectic, linotype (4/12) was essentially discovered by Iwase and Aoki, then demonstrated more rigorously by Weaver. Incidentally I made up a batch of 10/10 and considered making samples for test, but it ate the liner of my Lee pot so quickly that I'd have had to ladle-pour in my WW smelting pot over a gasoline stove, and I just wasn't that interested at this stage, since I know it is way, way above the optimum alloy for toughness.

    With regard to arsenic I've seen a summary article somewhere which asserted that while arsenic alone is a hardening agent, its use in most modern alloys in conjunction with antimony is because it allegedly increases the sensitivity of lead-antimony alloys to heat treatment. Looking into that is one of the things I hope to do eventually.

  2. #22
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    Yeah, Grumpy, sounds like a good idea. My contention is any poison injected into an eutectic anything will rock the alloy off any possible eutectic saturation, unless, of course, the new alloy can become an eutectic on its own accord. Prolly not possible with lead-tin-antimony in any realistic proportions for our use. Heat treating a true eutectic seems to be a waste of time. I don't think I have ever had a completely true eutectic in my pot; seems to always have had a slush stage somewhere, albeit small. ... felix
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  3. #23
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    Yes felix, it seems to me that any additional crystals in a eutectic would foul up the beautiful lamellar microstructure at best. That would be like throwing a few randomly-distributed rocks onto a perfect sand garden. Most likely it would disrupt the physical properties at least to some extent.

    I haven't been able to mix a perfect eutectic either so far, because all I can tell is that the outcome is not quite eutectic: I can't tell in which direction it is off. If I knew what is in my input alloys accurately though, and if my kitchen scales are any good, I should be able to hit it purely by calculation. On the other hand it is humbling to see that Weaver in her 1935 state-of-the-art laboratory, using the highest available purity grade of every constituent, sometimes missed by a whole percentage point in the composition of her test alloys when they were checked by chemical analysis. Perhaps she'd have done better to use analysed premixed constituent alloys instead of pure metals; melting antimony then adding other metals seems like a process that could result in losses.

    I'm not at all confident that arsenic issues can be properly resolved by my crude apparatus and methods. Some of the material I've seen says that trace amounts can have a major effect, so just getting the arsenic content down to say 0.1% may not be enough to make its influence negligible. However, all that is for the future, and if I continue to have no way to get actual samples analysed the whole investigation is already over anyway.

  4. #24
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    that's a very clever apparatus you've worked up there.....

    but...

    The Charpy V-notch toughness tester is just plain fun!

    Shooting those samples all over the lab. floor is one of my fonder memories

  5. #25
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    In a serious lab, rather than on my all-purpose workbench, I'd have used a pendulum impact test for toughness and either fitted an accelerometer to the pendulum, or done separate tensile tests to determine ductility by measuring the percentage elongation. However the vigorous scattering of pieces of samples that you mentioned when a true Charpy test is used, is a weakness of that test design: the kinetic energy imparted to those pieces is recorded as part of the toughness measurement. That is one of the reasons for my different approach. More importantly for our purposes on this board, it is essential that test specimens be cast, not machined, and be of a size and configuration fairly similar to cast bullets. So, if I were having all my druthers, I'd have used a modified instrumented Charpy test that used a small, cast, unmachined specimen.

    I'm getting underway with a new series of experiments to refine the previous results. This requires much closer control of the composition of the test alloys, so I can make more-specific observations. That is a never-ending story of course, but in the next increment I hope to be able to pin down the optimum antimony content. At this stage the idea of getting close enough metallurgical control to be able to investigate copper and/or arsenic is still way beyond the horizon.

  6. #26
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    Interesting in that it seems to bear out the traditional view of tin making lead alloys tougher. Well designed test! Seems to (in my understanding) define toughness correctly, and test it well. Many references to toughness that I've seen seemed to have it confused with hardness. Also very valuable to put a range for antimony content on peak toughness. Maybe a test with some copper?
    We need somebody/something to keep the government (cops and bureaucrats too) HONEST (by non government oversight).

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  7. #27
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    Leftiye, there is no good way to measure how much copper is good using home equipment because of the lack of a good flux to keep it in suspension long enough to cast "perfect" boolits. That would mean sporadic measurements for toughness and/or hardness. The only practical way to play with copper is to shoot the boolits for accuracy. Perhaps the best way is to make small lots which include copper and write exact notes about that lot. Compare boolit lots at the largest target at the longest range to ever be contemplated. Using copper suggests shooting at maximum accurate (enough) velocity with what mushrooming percentage obtained. Because copper inherently makes a boolit harder as far as we are concerned, there is good reason to reduce the antimony and arsenic to maximize mushroooming. ... felix
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  8. #28
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    However the vigorous scattering of pieces of samples that you mentioned when a true Charpy test is used, is a weakness of that test design: the kinetic energy imparted to those pieces is recorded as part of the toughness measurement
    Awe....

    What's a little KE among friends? Not to mention the energy imparted to a lab. full of undergrad. engineering geeks.

  9. #29
    Boolit Master in Heaven's Range Fleataxi's Avatar
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    Grumpy one:

    Wouldn't it be easier if Weaver used a smooth-sided slug for his tests?

    Seems all those bands add potential fracture zones, and wouldn't provide absolute measures, only relative.

    A major problem with experimenting is uncontrolled variables,and even only 1 major uncontrolled variable could invalidate the whole process.

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  10. #30
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    What you want is a copy of a jacketed bullet, but in lead. Very hard on the outside skin and dead soft in the middle when you water drop it. If you use a low antimony mix and find a way to increase the arsenic %, you will find something close to that.

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    first it makes me feel good about my preference for 5050 ww/lino. Its allways done extreamly well i penetration testing. the only doubt id put to your test though is the fact that the way your stressing the bullets is in no way typical of the types of strains a bullet is going to endure penetrating an animal. Im sure a bullet hitting nose first woiuld react alltogether differntly and give completely differnt results.

  12. #32
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    Leftiye, there is no good way to measure how much copper is good using home equipment because of the lack of a good flux to keep it in suspension long enough to cast "perfect" boolits. That would mean sporadic measurements for toughness and/or hardness. The only practical way to play with copper is to shoot the boolits for accuracy. Perhaps the best way is to make small lots which include copper and write exact notes about that lot. Compare boolit lots at the largest target at the longest range to ever be contemplated. Using copper suggests shooting at maximum accurate (enough) velocity with what mushrooming percentage obtained. Because copper inherently makes a boolit harder as far as we are concerned, there is good reason to reduce the antimony and arsenic to maximize mushroooming. ... felix
    Felix, Suspension? Is there not a percentage where a true alloy occurs? If there is, then carbon bearing fluxes should stop oxidation. If copper does not alloy, then forget it. Hell, don't they make lead bearing steel alloys?

    I'm just fine with lead/tin alloys (up to 10% tin will alloy), I'm not convinced the antimony has any desireable effect on toughness anyway. If it were 10% tin, then maybe it will "carry" more copper. I know copper and tin will alloy. In fact, how about putting in copper that is already alloyed with tin - as in brass?
    We need somebody/something to keep the government (cops and bureaucrats too) HONEST (by non government oversight).

    Every "freedom" (latitude) given to government is a loophole in the rule of law. Every loophole in the rule of law is another hole in our freedom. When they even obey the law that is. Too often government seems to feel itself above the law.

    We forgot to take out the trash in 2012, but 2016 was a charm! YESSS!

  13. #33
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    Quote Originally Posted by Fleataxi View Post
    Grumpy one:

    Wouldn't it be easier if Weaver used a smooth-sided slug for his tests?

    Seems all those bands add potential fracture zones, and wouldn't provide absolute measures, only relative.

    A major problem with experimenting is uncontrolled variables,and even only 1 major uncontrolled variable could invalidate the whole process.

    Fleataxi
    Weaver - a lady by the way - only did cooling tests and hardness tests, she didn't do any impact or strength tests. She also focused on typemetals, so she didn't go below 6% antimony (2/6 alloy, once known as electrotype in British industry, was the nearest she came to pure lead). The concept of using a bullet-sized specimen and impact testing it was mine, not hers.

    I was initially attracted to the idea of using a straight smooth specimen of 7mm diameter. I chose the 311466 for practical reasons, one of which was that I wanted the face-validity that goes with testing a real bullet. Another was that any bullet caster or metallurgist can acquire the same mould and duplicate my tests if he or she wishes; the whole issue of sample preparation disappears except for the matter of mould temperature and casting technique. So far as the issue of obtaining absolute measures is concerned, I don't know of any metallurgical test of physical properties that provides anything but relative measures - especially the Charpy test, with its notched specimen. The essential feature in this case is to get the right kind of grain structure. This depends on the specimen's surface configuration, diameter, length, pouring arrangement, metal temperature and mould temperature. The arbitrary feature of my approach was the use of a 30 caliber specimen rather than say 45 or 22 caliber. Rejecting the large caliber was easy: such bullets are way too short and fat to be fractured repeatably by transverse impact. The objection to the small caliber was partly that repeatability would have suffered due to absolute scale effects (shrinkage differences with different alloys would have mattered, as would casting quality), and partly that it is at one extreme of the range of specimen sizes likely to be of interest.

  14. #34
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    Quote Originally Posted by 45 2.1 View Post
    What you want is a copy of a jacketed bullet, but in lead. Very hard on the outside skin and dead soft in the middle when you water drop it. If you use a low antimony mix and find a way to increase the arsenic %, you will find something close to that.
    The straight smooth specimen concept has an attractive simplicity, but real cast bullets come with a range of built-in stress concentrations, so I decided to include some. Since the 311466 is a Loverin, I ended up including plenty rather than some. The alternative of two or three large lube grooves (which I tried in pilot experiments) seemed as if it might have been sensitive to longitudinal location of the impact point relative to the edges of the grooves, so my solution was just to have lots of small grooves and a fairly precise way of fixing the axial location as well.

    So far as skin-versus-core hardness is concerned, my heat-treated specimens were water quenched of course, so they would have had a variation in effective quench rate versus radial depth generally similar to water dropping. The real issue here though is specimen diameter; you can't expect the same hardness distribution between surface and core in a 30 caliber bullet that you get with a 45.

    In the series of tests I've just begun I'm trying to get considerably better control of alloy composition, and I hope I now have a way to get actual analysis results to include in my (eventual) report. This makes it possible to look at alloys only 0.5% apart in antimony content instead of 2% apart. (Since I now know from the first series of tests that I'm only interested in the range between about 3% antimony and just over 4%, the number of test alloys remains manageable.) Of course it does not make my variability in heat treatment or physical test parameters any less, so I don't know at this point whether the whole project will succeed this time; I may end up with a lot of wavy graphs that keep intersecting with each other. However that is the way it goes with experiments - if we knew the results we wouldn't need to perform them.

    So far as arsenic is concerned, the literature seems to say that it has little incremental effect above about 0.15% content if used in conjunction with antimony. Equally importantly the analyzer I hope to be able to access does not test for arsenic. I can get a proper lab analysis for $50 per test, but at this point I'm not greatly attracted to that option, given the number of tests likely to be required, so I'm hoping to get by using X-Ray Fluorescence with one of the ubiquitous Niton XLt scanners through the cooperation of a scrap dealer.

  15. #35
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    Quote Originally Posted by Lloyd Smale View Post
    first it makes me feel good about my preference for 5050 ww/lino. Its allways done extreamly well i penetration testing. the only doubt id put to your test though is the fact that the way your stressing the bullets is in no way typical of the types of strains a bullet is going to endure penetrating an animal. Im sure a bullet hitting nose first woiuld react alltogether differntly and give completely differnt results.
    Lloyd, if my results are valid your alloy has way too much antimony to have good toughness. You can see that by comparing my 0.9/4 graphs with my 2/6 graphs; 2/6 is a bit on the brittle side, and your alloy must be 7 or 8% antimony.

    There isn't any single, simple test that can duplicate all the things that might happen to a bullet under impact. What I hope to achieve is a valid, repeatable laboratory test that shows something about the metallurgical properties of these alloys. How that interacts with particular bullet designs, impact velocities, and sets of circumstances like how the bullet is oriented when it strikes bone, are a different line of inquiry. My expectation is that a bad alloy remains inferior to a good alloy regardless of how you apply it in practice - but the way you apply it may make more difference than the alloy properties do.

  16. #36
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    i guess i still believe the best test that is available now for the average man for comparing how bullet alloys differ in a hunting situation is a good heavy bone followed by wet news print. If a guy is not lazy and changes his paper and bone often enough it gives a pretty good look at how a bullet of a certain alloy compares to another. The results are surpisingly repeatable. It all depends on what a guy considers toughness to be. To me its not only the bullets ablility to keep from fracturing but also has to take into count the resistance to deform. Some alloys are very ductable and resist fracturing but arent worth a hoot because they will deform apon hitting bone. Something thats fine in a whitetail but if a guy has to rely on a bullet to put down a 1000lb animal you want as little deforming as possible. I guess my point is a flat nose bullet cast out of a slightly higher antiomy content will give a better compromise when it comes to holding together and not deforming. Now another thing you have to keep in mind with my thoughts is that they are for magnum handgun velocitys and bullets not rifles. To be honest ive never seen a bullet out of straight linotype fracture at handgun velocitys. I have though seen water dropped ww bullets, especialy sharp nose to driving band designs like swcs loose there noses.

  17. #37
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    Hiya grumpyone. I got a chance to read this, so I'm posting here instead of the other thread.

    First, a suggestion. Instead of mailing off your bullets to get their exact composition certified, why not order laboratory-grade lead, tin, and antimony - scale weigh each into the alloys you want to test - and cast a few sample bullets to test? Thus, you'd avoid all the issues of lab GCMS, as well as "contamination" (or maybe more accurately) variation in alloy. Just a suggestion.

    Second, I'll have to re-read your posts here several more times, but on our discussion on the other thread, you (very paraphrased) said that high-tin with low-antimony alloys have a poor quality consistency of hardness. I don't doubt that assertion, but I don't see the data here to support it. (Like I said, I'm going to re-read it a couple more times - being neither an engineer or chemist, you're going pretty fast for me... ) It SEEMS to me that most of Weaver's testing was done with very high concentrations of tin/antimony vs. what I was talking about with a low-BHN cowboy bullet. Could it be the conclusions with those "strong-alloy" bullets do not translate to the "weaker-alloy" bullets I was talking about? (Without any proof I assert that high-lead-content alloys display good ductility. This property may counter the fracturing/tearing action one would be worried about with the inconsistency of the alloy due to the higher tin content.)

    Third, I want to compliment you on your methodology. I see the scientific method often messed up, but you've done an excellent job. I believe results would be easy to correlate and proove by others.

    Fourth, you state at one point that the ideal level of antimony for hardening is around 4% (but you're not sure exactly where). Does that mean, you'd assert that the best alloy would be around 92-4-4 (depending on exactly where that antimony percentage falls)?

  18. #38
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    Quote Originally Posted by MakeMineA10mm View Post
    Hiya grumpyone. I got a chance to read this, so I'm posting here instead of the other thread.

    1. First, a suggestion. Instead of mailing off your bullets to get their exact composition certified, why not order laboratory-grade lead, tin, and antimony - scale weigh each into the alloys you want to test - and cast a few sample bullets to test? Thus, you'd avoid all the issues of lab GCMS, as well as "contamination" (or maybe more accurately) variation in alloy. Just a suggestion.


    2. Second, I'll have to re-read your posts here several more times, but on our discussion on the other thread, you (very paraphrased) said that high-tin with low-antimony alloys have a poor quality consistency of hardness. I don't doubt that assertion, but I don't see the data here to support it. (Like I said, I'm going to re-read it a couple more times - being neither an engineer or chemist, you're going pretty fast for me... ) It SEEMS to me that most of Weaver's testing was done with very high concentrations of tin/antimony vs. what I was talking about with a low-BHN cowboy bullet. Could it be the conclusions with those "strong-alloy" bullets do not translate to the "weaker-alloy" bullets I was talking about? (Without any proof I assert that high-lead-content alloys display good ductility. This property may counter the fracturing/tearing action one would be worried about with the inconsistency of the alloy due to the higher tin content.)

    3. Third, I want to compliment you on your methodology. I see the scientific method often messed up, but you've done an excellent job. I believe results would be easy to correlate and proove by others.

    4. Fourth, you state at one point that the ideal level of antimony for hardening is around 4% (but you're not sure exactly where). Does that mean, you'd assert that the best alloy would be around 92-4-4 (depending on exactly where that antimony percentage falls)?
    1. There are two reasons I didn't use lab grade ingredients and just mix them without verifying the outcome. First, it would be fairly expensive - I used up about 70 pounds of alloy in the experiments described so far. Second, Weaver used only the highest purity lab grade ingredients then analysed them anyway, and found deviations of 1% in some cases from what she had tried for. I think the only way to know what you've tested, is to analyze what you've tested.

    2. The issue of soft spots in alloys with more tin than antimony was raised and described by Dennis Marshall in the RCBS Cast Bullet Manual. He does not explain why it is so in any terms that I understand. Metallurgically I would expect that surplus tin would go into solid solution with the lead matrix, unless the tin level were extremely high - but I'm saying that without knowing what metallurgical mechanism Marshall was expecting and reporting.

    With regard to ductility of very high-lead alloys, as a starting point, pure lead is extremely ductile. Addition of fairly modest amounts of antimony or arsenic seem to reduce this ductility considerably. It is evident from my own results shown in this thread that ductility decreases considerably from 2% antimony, to 4% antimony, and then more rapidly to 6% antimony, and by 13% antimony ductility is pretty well negligible. However ductility seems to be higher for pseudo-binary alloys than it is for low-tin alloys with the same antimony level, and toughness is considerably higher for the pseudo-binary alloys. For your cowboy bullets I suggested in the other thread that you use something considerably less than 1.5/1.5 alloy. Without knowing what pressure you are using, I'd have thought pure lead would be adequate but isn't all that easy to cast, so you might consider lead with just 1% tin added.

    3. Thank you.

    4. I have started a series of experiments aimed at identifying the toughest-possible lead-tin-antimony alloy more precisely than just as approximately 4/4. I don't know if the experimental method I'm using will work or not; if it does, it will take a while yet. Until I've found the alloy that gives the highest peak toughness, then had it analyzed, I can't go any further than to say somewhere fairly near 4/4. It is highly frustrating not having ready access to an XLt scanner. More importantly though, I don't recommend 4/4 alloy as a general purpose bullet alloy because it is both more expensive and less ductile than say 2/2, 1.5/1.5, 1/1, and pure lead. I'm anticipating that the best solution is to only provide enough toughness to suit the energy level of your bullets, while maximizing ductility. That means use just enough alloying to heat treat to give the hardness and toughness you need for your application. That way you get the lowest cost and highest ductility together with the amount of toughness you have found you need. 4/4 alloy is my current estimate of what is the toughest possible alloy, which makes it a high-performance rifle alloy. Short of a bolt action handgun, it probably isn't needed for anything else. People who want low-energy hollow-point bullets to expand readily would probably be better-served by much lower degrees of alloying.

  19. #39
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    You're doin' good, Grumpy! Keep it up. ... felix
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  20. #40
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    Hello Grumpy,

    I just read your answer #20 from 5-26-2008 to my question, also the rest of this thread. I wanna say thank you for your work you made for all serious casters.

    Dirk

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