Hardening lead and how it works

[Bret4207]

But aren't we using a BHN scale?isn't it a Brinnell hardness number which comes from a known scale?? I opened this can of worms not meaning to, but hard is not always strong look at glass it's hard until the hammer hits it.

I can take a given alloy and produce 3 widely different Bhn factors. Or I can take 3 different alloys and, given time to play with it, produce the exact same Bhn factor. Bhn is one part of the story. Whats in the alloy, how it's treated, how long ago it was treated, what it does after sizing or HTing or HP'd all affects the end product. The more you get into this, the more questions you have and the more you question the "facts" that people give you. "HARDCAST" is the most ambiguous term in use in this hobby/art/science. It means absolutely nothing, yet it's the most common term you'll see in use regarding cast bullets. It's been a peeve of mine for at least a decade now.

 

[Bret4207]

Could it be because the wheel is round,flip it over it's still round

Not if you flip it on it's side. A wheel isn't round, it's a disc. See? Incorrect terms and ambiguous meanings.


Sorry. I get like this in the depths of the frozen hell we know here as "winter"..........

 

[RBHarter]

I need the depths ....... I just couldn't find the words for not a ball.

I can take a given alloy and produce 3 widely different Bhn factors. Or I can take 3 different alloys and, given time to play with it, produce the exact same Bhn factor. Bhn is one part of the story. Whats in the alloy, how it's treated, how long ago it was treated, what it does after sizing or HTing or HP'd all affects the end product. The more you get into this, the more questions you have and the more you question the "facts" that people give you. "HARDCAST" is the most ambiguous term in use in this hobby/art/science. It means absolutely nothing, yet it's the most common term you'll see in use regarding cast bullets. It's been a peeve of mine for at least a decade now.

This is exactly correct.

All steel will flex and return some ,all steel is hard . Nobody thinking clearly would use hot rolled for armour , boilerplate for springs much less spring or boilerplate for a truck bed that hot rolled would be perfect for .

 

[Rick]

Well said, well written & spot on Bret. We had a thread going a few years back over at CB on this subject and never really got anyone to agree on much. The term hardcast is still one of my bigger pet peeves because it very incorrectly makes those new to casting believe that if they aren't shooting diamonds they'll ruin their barrel. The simple truth about the term hardcast is that it was coined by the commercial casters, bullets of a proper hardness don't ship well and by the time they got to the end user they would be hammered dog doo doo. Because of that they cast with hard alloys and try to make their customers believe it's for their benefit. Same reason they use a hard lube, it stays on the bullets during shipping. Neither hard bullets or hard lube are for the shooters benefit.

Hardness and BHN are here to stay I think, it's pretty much ingrained into the lexicon but it sure would help if those seeking advice would include the info on just what the alloy is and what was done with it to arrive at stated BHN numbers. To make things even harder to understand with BHN numbers is the wide variation in reported numbers using various tools to measure it. I had a conversation going with a guy once and never could convince him that his air cooled wheel weights weren't 22 BHN and his water quenched WW wasn't 40 BHN, he insisted he was right because his LEE tester said so. None of these hobby BHN testers are laboratory grade pieces of equipment and they vary between not only the testers but also how they are used.

 

[fiver]

it would be nice to discuss malleability versus shear strength, but I wouldn't understand most of what was being said.
it think it's a bit easier to say ww's and soft lead [I dunno what's in either one] but the point of ww alloy being too hard gets across.

 

[KHornet]

I am far to right brained to discuss the technical values of alloys. Sooooo-guess I will just continue on continuing on in my non tech ways, water dropping and hoping that they shoot to point of aim.

 

[JWFilips]

Rick,
After the quench: Is there any environmental conditions that would speed up or slow down the length of time for a heat treated bullet to reach it's max hardness?
For instance: after quenching if the bullets were placed in a deep freezer for a few day as opposed to room temperature would that quicken the the hardening process & Vsv. or If the quenched bullets were held at a higher temperature would that slow down the hardening process?

 

[Dusty Bannister]

I often see the comment that placing the quenched bullets in a freezer stops the process wether it be hardening or softening. Given this softening from quench hardness is so slow, I never gave it much concern, let alone tested it. Unless it is for a special purpose, I just prefer to work with the blends that will reach their normal and stay there.

 

[KHornet]

Being to old a dog to learn many new tricks, I will continue doing as I have been doing for many years, and that is water dropping most every thing and waiting until age hardens naturally.

 

[Rick]

I don't know that after quenching keeping them in the freezer would speed things up all that much but I have never given that a real test. Age softening that we hear so much about is quite slow. That I have tested. I heat treated CWW to 30 BHN, placed them in an old Sierra bullet box properly labeled with alloy, date, BHN etc. and put them under the bench and promptly forgot about them. One day I was cleaning out under the bench and there they were, 10 years old. I figured they would be putty by now but they tested 26 BHN. So yes they did age soften but . . .

.

 

[Brad]

I would have to go back and look but I think Veral mentions in his book that cold slows the process and heat increases it. How much is all relative.

 

[KHornet]

Agree with you Rick on the age softening, over periods of time, and by accident have tested some bullets that I forgot, and found them to drop some also. Like your analysis it was a relatively small percentage of hardness. Believe the ones I tested were about 7-8 years old.

 

[JWFilips]

Guys, Not to worry I'm not trying to speed things up…….Don't really care about doing it: I was just interested in the crystal structure process of how the lead hardens and if certain factors could alter it in any way.

Let us just say: If from the oven the alloy is dropped into ice water….would it benefit from being held at that temperature for a few days or so verses coming out of the ice bath and then warmed up to 170 deg and be held there for a day or so? Just wondering if environmental factors can alter this process or is it solely one of alloy composition ?
Guess I need so find someone with an electron microscope

 

[Rick]

There was a thread on CB some time ago where they used anti-freeze kept in the freezer and quenching in that. If I remember correctly they didn't achieve a lot for the effort required. They will only get so hard anyway dependent on the Sb percentage so the only thing you could change would be the time to final hardness. If you have at least 2% Sb in the alloy that time for practical purposes would be 2-3 days with only minor additional hardening after that for a couple of weeks.

.

 

[Rick]

Jim, if you took them out of the ice water and heated them to 170 degrees you would be annealing them. So yes, that would definitely effect them. 170 would not be enough heat to completely return them to their un-quenched BHN but would have an effect.

.

 

[JWFilips]

Rick,
So in essence ( If one experimented and had the data) one could draw back the hardness from a too hard a heat treated lead alloy with possible duplicatable results?

(Again no overly hard alloy here just in a mood for some Science stuff this morning

 

[Brad]

I know we can anneal a heat treated bullet. Boiling might work if done for long enough. Try using the same time and temp we use for heat treating but instead of quenching the bullets turn off the oven and let the bullets slowly cool.

If you want a specific hardness then see what temp is required with that alloy for heat treating. An over hard or softer bullet from that same alloy can be reheated to the preferred temp then quenched. Voila, the right hardness.

 

[Rick]

Jim, yes. If you re-heated a heat treated Pb/Sb alloy it will be annealed to a softer final BHN. How soft depends on the Sb percentage and the annealing temp. The process is the same as heating and quenching except don't quench, let them cool slowly to room temp. However, in no case can they be made softer than the initial air cooled BHN of the particular alloy. In other words if you drop the bullets from the mold on a towel and let them air cool the aged BHN is as soft as that alloy can be. By varying the anneal temp you can vary the final annealed BHN and yes, it is repeatable assuming using the same alloy and same anneal temp and same ambient room temp.

.

 

[fiver]

yeah you can draw them back.
just cut the heat and follow the same sequence.
instead of running the oven at 400-f drop the temp down to 350-f or 375-f.
the final bhn will chase the quench temp up and down the scale.

 

[Lost Dog]

Good grief! Yall sure do complicate things!
But now ya got me wondering about when I heat my Hi-Tek polymer coated bullets at 375f. Granted its only for 10 minutes but.... with my crappy luck I probably do something bad to em.