Reheating old. Alloys

[GregLaROCHE]

As I understand, an alloy with antimony in it will get harder with time. Does it stop at a point?

If you melt an ingot with antimony in it that is thirty years old, will the boolits cast from it be be the same hardness as the ingot after thirty years, or will they revert back to the hardness of the ingot when it was first poured?

Thanks

[HangFireW8]

You need to read the lasc site and the stickys.

Short answer, if an agent like arsenic, sulphur or copper is present, the lead antimony alloy will be harder after casting, and continue to harden for a year to three, then slowly get softer again.

Water dropping will speed and increase the hardening process, oven hardening even more.

Actual rates depend on the precise alloy and casting temps as well.

[William Yanda]

Your last supposition is correct. Hardness is a function of crystal formation. Re-melting destroys the crystals. As the product solidifies, crystals are reformed. Small objects, bullets, may be different than large objects, ingots, because of different rates of cooling. Expecting bullets to compare exactly to ingots of the same material is not a wise expectation.

[GregLaROCHE]

I have found that boolits cast at the same time as ingots are harder a year later than the ingots.

[ioon44]

"Water dropping will speed and increase the hardening process, oven hardening even more."

I also found that water dropped bullets will return to the original alloy hardness after a few years.

[lightman]

When you melt a lead alloy you start all over on the hardness from what it started as. My experience is that bullets and ingots also don't age harden the same. Personally I don't pay much attention to hardness except as using it to guess at the composition of scrap.

[kevin c]

I recall that the instructions I got with my LBT hardness tester specifically said not to make the mistake of assuming a Brinell number from an ingot would be the same as that of a boolit cast from the same alloy, basically because the differences in cooling due to different mass and thickness.

[sqlbullet]

I saw this thread on the digest on my phone the other day but didn't have a chance to respond to the OP. I wanted to add some color here.

The base questions asked have been answered. The lead does not harden forever, and re-melting returns you to the starting point.

The experiments I have run seem to indicate that the initial temperature and treatment (air cooled, quenched from the mold, oven heated and quenched) create different base structures in the alloy, which then provide a foundation or framework for the age-hardening to utilize.

Depending on the alloy and the hardness obtained in the initial treatment I have seen the final hardness go both up and down.

Air cooled isotope tests at about 10-12 after a few days, but hardens over 24 months to between 13 and 17, influenced by how hot the lead was at the time of casting. Test samples cast from a 650° pot and air-cooled tested 10.5 after a few days and 14 after 24 months. Those cast at 700° were 11 and 16.5 and samples cast at 750° were 12 and 17.5.

Samples that were oven heated and allowed to air-cool from the oven were 9.5-11 after a few days and 12-13 after 24 months, again with higher initial casting temps resulting in harder bullets at the end of 24 months, though the amount of gained hardness was much smaller.

All of the samples that were quenched either from the mold or oven heated and quenched started out between 16.5 and 32.5 but finished 24 months with a hardness between 21 and 24.5, again with a bias to those that were cast from hotter lead. It was very interesting to me to see such an initial huge variance in hardness which culminated in a final numbers all clustered tightly around a value of 22.5.

The initial lead temperature and the choice to quench or not clearly create conditions which heavily influence the final hardness of the bullets. And a temperature variance of 100° in the pot can result in very different bullets after 24 months, especially if air-cooled.

[JonB_in_Glencoe]

I gotta ask, does your alloy contain any Tin? or maybe a trace amount of Copper, like 0.25%
those elements will change an answer to your question.

I recently posted about this in another thread.
http://castboolits.gunloads.com/showthread.php?374275-Another-Hardness-Question&highlight=


When I started casting, I had all kinds of questions about age hardening and work softening. While most lead alloys age harden and work soften, I learned that different alloys act/react differently and/or at different rates. Asking how a unspecified alloy may or may not react would be impossible to answer.

ALSO, Ingots and boolits will likely measure differently from each other and may age harden/soften differently.

[sqlbullet]

JonB_in_Glencoe, I don't know if you are asking me or the OP.

For me, yes. Isotope alloys that I used for the tests were tested by XFR and contained about 3% antimony and 1% tin. The rest was lead (≈96%) with traces (<.10% combined) of all kinds of stuff, as is common. Some of the trace are elements that are really there in very small amounts, and some is just backscatter from the nature of the testing.

And you are spot on that ingots and bullets measure differently, and I have considered re-running the tests using coupons of lead rather than bullets.

[JonB_in_Glencoe]

I was commenting to the OP. Sorry for the confusion.
Due to my technique of smelting (making ingots), I never test them for hardness, I only test boolits...I have been known to cast a few test boolits when smelting a unknown alloy...I have a Lee 2 cav 41 cal SWC just for that task.

[Conditor22]

You melt an old alloy, it will revert to it's softest state depending on what it is composed of.

water/ice quenching the newly cast boolits cam make the alloy harder than the age hardened alloy also depending on what it is composed of.
a trace amount of arsenic will greatly increase the hardening process