Heat treat low Sb alloy

popper

Well-Known Member
Interesting, maybe somebody has seen it before. Same mould, 1% vs 2% Sb. 2% HT was same harness as AC 1%. Low Sb about 1 month old, HT is 1 wk old. @ 1% HT appears to have NO effect, kinda expected! 2% thought it would, I'll wait another week and see. Oh, vice smash test for hardness. 4% is harder in a day. 2% is frosted - 1% never gets frosty so yes, higher Sb. Thoughts? Oh, so far, trying to push soft 145gr GC BO past 2200 doesn't work. 100 yds.
10923
 
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Ian

Notorious member
It takes at least THREE weeks to see where the hardness is going, should be about 95% by then. It takes about 3-6 months for it to fully stabilize.
 

fiver

Well-Known Member
the less you have the longer it takes.
2% is 3 weeks minimum.
1% could be 6 to 8 for the BHN to get close together as well as close to it's actual.

believe it or not the BHN of Ht alloys can go over their final long term BHN for short periods of time.
think about it like waiting for paint to cure not dry but come to a final cure.
 

popper

Well-Known Member
OK. Scoped the BO barrel this morning, don't see a lot of leading, just some streaks and spotty (dirt?). Guess the BLL really works at this pressure/fps. Needs a patch run through it anyway, been a long time.
 

hrpenley

Active Member
It takes at least THREE weeks to see where the hardness is going, should be about 95% by then. It takes about 3-6 months for it to fully stabilize.
Well, if you happen to have a cryo-chamber you can take them right from the cold bath then cool them down over a 12hr period with a few ramp and soak spots, hold at -310 for a couple hours then reverse the process, full cure of the alloy and fully developed crystallization, hardness and final size will be nicely achieved in about 24hr. Much better than stopping at room temp......Just saying
 

STIHL

Well-Known Member
hrpenley, can you elaborate a little more on this process as I am ignorant to cryo treating. I'm assuming this process is not cost effective or plausible for the majority of people. Just interested out of learning more.
 

hrpenley

Active Member
As Ian noted in a prior post it takes time for alloys to fully "cure" or achieve complete crystal growth, hence reaching a reliable size, hardness and toughness. Almost all alloys have this problem, crystal growth is generally near completion once the metal has reached room temperature however not quite,(That's why flash cooling in cold water does what it does) the metal will continue to crystalize for up to a month or longer. Using cryo temperatures this process can be sped up in virtually all alloys, (That we can get our hands on ) and will achieve 99%+ crystal growth around -310 F. Which happens to be just above the boiling point of liquid Nitrogen and that makes it the choice gas to achieve the desired temperatures. A process of ramp and soak cooling is used to lower the temperature of the desired alloy or objects over a period of time until they reach the preset temperature of -310 to -315F, then hold them there for aprox 24hrs, then slowly bring them back up to room temperature. This all varies by the material you are wanting to treat. You have to look at the mass and thermal property's of the alloy so that you do not cool it too fast and stress crack it but to slowly involves wasting gas, which is not real cheap, probably the cost of propane/lb last time I worked with it. The construction of the chamber is not that complicated, I have seen work posted here that takes more talent, your real cost is in the valves and temperature control, Wat-lo was a good mfg when I was in the business. The whole idea is to allow the alloy to cool completely thus allowing complete structural growth, something that can not be done under normal conditions. Something even time will not replicate, it comes close but nothing actually is finished even after a month. Put almost any alloy under a microscope, run a cryo-treatment and look at it again, even if it's already a year old, you will be able to see additional crystal growth, they will be larger and more defined, longer tendrils will increase the "toughness and wear factor" of the alloy. Now does this really make that much difference and is it worth the cost and trouble - No , Is it cool to do? Yes, and It will make your bullets ready to shoot in 48hrs if you really want to do it.
 
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fiver

Well-Known Member
if you wanted to give it a run at home I bet you could make quite a difference with some carbon dioxide ice and a good cooler.
your not gonna get to the nitrogen stage for sure, but you'd at least be able to do it half way.
 

STIHL

Well-Known Member
What effects would a deep feeze have on them? Say you wAter quench and then go into the deep freeze for 2-3 days or a week? Would that make a difference in crystal growth? Or speed it up my a couple weeks. Curiosity is getting the best of me now.
 

hrpenley

Active Member
R744 I believe will take you to around -100 or so but you would need to keep it under pressure the whole time to get any real cooling benefits, you would want it to stay in the liquid phase as long as possible using a double chamber and spray cooling, just a guess as I have not looked into this but that may speed up the cure time by 1/3 or so, but curing is not a linear progression, it slows with time, there would be some benefits but this is only a logical guess. It would be better than stopping at cold water however again we are back to cost and time vs benefit. Also before you try this you will need a lot of insulation - vacuum barrier is the best but hard to get without proper tools, your gas consumption is very high with good insulation, an average "run" used a couple hundred pounds of liquid nitrogen to complete the cycles. This was using a well made SS double wall vacuum insulated barrier and cover with maybe 6 cubic feet of chamber area.
 

hrpenley

Active Member
Deep freeze at an average of -20, again better than water, would need a few days, would speed it up some but not much more than cold water, you really have to get the temp down to make a significant change.
 

hrpenley

Active Member
Im not sure how well you can do it with dry ice, part of the process is temperature control it needs to be reduced slowly and evenly to avoid cracking, and pretty much anything will crack at these temps. Get enough differental between surface and core, or just 1 side vs the other and pop, I have seen it with alm/iron alloys/ titanium drill bits, pretty much anything when we were developing the system.
 

fiver

Well-Known Member
for your average home caster and not the lab setting.
the key is in the speed of the cooling and from what temp to what temp you can get the bullet the fastest.
as you broaden the window the more BHN you gain.
the thing is how much do you need?
and there is for sure an outer edge you can hit.

as far as just taking a water dropped bullet to the freezer and storing it, you will slow down the hardening process.
this is beneficial if you only have like a Saturday afternoon to cast and won't be able to size-lube them for 2 week to say a month.
this just puts off the process and doesn't stop it, your not gonna be able to deep freeze them for 3-4 months and have them come out at 12 BHN.
 

hrpenley

Active Member
Nope, I just leave mine sit after pc for about 4 weeks and load them up., usually I am that far behind anyway, got cast 9mm been sitting for almost a year now, I get around to it sooner or later......
 

STIHL

Well-Known Member
I am going to try and do a hardness test on some tonight, they have been sitting 2-3 years now some longer. Work has been crazy last 2-3 years, took a new job within the company and it keeps me in the road quite a bit. I've finally reached the point where work will be there tomorrow and if im not spending time with my family, I'm going to be working on my loading room and casting and prepping and loading. I've got a lot of stuff to tinker on.
IIRC the boolits water quenched to 10-12 BHN might be surprised at what they aged too. Might be surprised ant how much they grew too.
 
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STIHL

Well-Known Member
Checked 4 of the 3 year old with my Lee tester. High was 26 low was 16 and had 1 at 17and 1at 19, so I figurethrow the low and highs out and average. I'm call No them at 18BHN. So they have aged quite well from 10-12 I think.
 

fiver

Well-Known Member
a normal 10-12 BHN alloy will usually settle out at around 18 after a month, then you'll start to see a little antimonial growth after about 6 months, it generally settles down pretty quickly though.