Annealing Question
- Thread starter dblinden
- Start date
Well, Norma believes it hardens with age. From their website under "cases": "The case neck is annealed to become softer. This prevents gas leaks and enables the case to hold the bullet firmly for at least 10 years without cracking as a result of AGING MATERIAL."Webster said:
Explain why shooting decades old factory cartridges invariably nets a lot split necks......ammo stored in cabinets and NOT horse stables.
Don't know if brass will get "harder" with age but I do know it will get "brittle". I have lots of experience with old Hornet, 25/20, and 30/06 brass. Reloads that were not annealed first--lots of split necks on firing. Loads that had the cases annealed first had no such problems. Had a bunch of split necks firing 35 year old Hornet factory loads. Those that survived were annealed and re-loaded and seem to be doing fine. I don't think a few weeks or even months will bother brass, but I do think a few years will. YMMV dedogs.
The reason old brass will crack is the same reason to anneal in the first place. The phenomenon is "stress corrosion cracking".
Two things must be present stress either applied or residual and it must have a tensile component (it usually does); and corrosion must be present. In today's world corrosion is present in all but a few places from atmospheric pollution. This is why the old brass cracked. The additional stresses of loading and firing were the final straw.
The oxide layer left from annealing helps to prevent corrosion, which is why the military leaves it on their ammo.
If you anneal brass today and place in a vacuum bag it won't get brittle or harden with age. Brass ONLY hardens with cold work. But it loves to corrode and is very susceptible to stress corrosion cracking.
Two things must be present stress either applied or residual and it must have a tensile component (it usually does); and corrosion must be present. In today's world corrosion is present in all but a few places from atmospheric pollution. This is why the old brass cracked. The additional stresses of loading and firing were the final straw.
The oxide layer left from annealing helps to prevent corrosion, which is why the military leaves it on their ammo.
If you anneal brass today and place in a vacuum bag it won't get brittle or harden with age. Brass ONLY hardens with cold work. But it loves to corrode and is very susceptible to stress corrosion cracking.
Age hardening of brass and other copper alloys is real, it is not caused from cold working, although this does happen too. Brass grain structure is complex, once it has been worked, say from being drawn into a cartridge case, the grain is transformed, hence the reason for annealing throughout the process of case forming. This process of grain movement over time, because it has been stressed, continues over time. The simplest way to describe it is known as 'springback'. This we all know about, how much brass deflects, then moves back some, this is the grain structure under stress, only annealing relieves it some, over annealing 'ruins' or 'burns' the brass to a point where the grain structure is too 'loose' to ever take a normal pattern and will remain too soft for further use. Also, quenching of brass, unlike carbon steels, does not change the grain structure, hardening it.riflewoman said:
It took an entire metallurgy book for me to get my head around the whys and whatfors in regard to annealing, case hardening and grain flow of certain alloys when being smeltered, to poured, stamped, drawn and annealed to get the final product.
It's not as simple as low carbon steel, as an example.
Cheers.
8)
Webster said:
No sir, this is not true. Brass gets hard just from sitting...time and exposure to air. But, it does take a lot of it, not months, more like years, decades. Example, I have found that brass untouched from around the late 70's to 80's and older will need annealed just because the age and sitting. I learned this in 91 when I got a batch of LC 58 308 cases. None of this brass had been worked. Run them through the size die and no matter how much or what kind of lube I would always get a "chirp" when the expander ball passed back out of the case. Was also getting inconsistent muzzle velocities on the chrono. At that time Redding was starting to make a carbide button for other brand dies. When I called them to order one {thought that would stop the chirp} the guy explained the need to anneal. He was right, it worked...stopped the chirp and fixed the velocity spread.
A guy gave me a box of brand new from the 50's, 35 Remington ammo...every neck in the box was split and they had never left the box.
Work hardening happens as the brass gets worked, right then...not much point in worrying about something that happens over a 30 year period, unless like me you get some old cases you want to use. I think it can happen a little faster if the brass lays around out in the weather.
Then please explain why some military brass date stamped 1964 is still fine and as soft as it was in 1992 when I loaded it last?
riflewoman said:
I agree with all of your statements. I have read on a website that someone was reloading military ammo with a 42 (1942) head stamp. reloaded many times without a problem. I was in the Army 1964-66, we fired 10-15 YO rounds at the range , no problem. I have a 45/70 black powder round that was probably made before 1900. Pulled the bullet out with pliers. The case had good ductility and no brittleness.
Two days ago I E-mailed a PHD Metallurgy Scientist I used to work with. He is a a consultant to the copper industry. He told me 70/30 brass is an extremely stable alloy and doesn't change with time. Waiting for a follow up E-mail and permission to use his name. You can Google his name and get well over 25 hits for technical articles he has published and books he has written or edited. The longer term problem must be stress corrosion. The more stress the more likely to get corrosion. Some chemicals and moisture should be present for corrosion to take place. It's unlikely to see stress corrosion except on a cross section on a microscope. Some nitrocellulose contains excess acid that wasn't removed during manufacture.
Some people on this website said they had problems with old unused brass. It cannot be from the brass properties changing with time and stored in a clean dry environment. You need to look somewhere else.
ADDED LATER:
Not really related. Some countries has chosen copper tanks to store nuclear waste because copper will stay unchanged for at least 100,000 years.
dedogs said:
I have had the same experience! Just completed annealing a lot of military 30-06 match brass from the early '60's. They are doing fine now. Had begun to process & had several split necks. Have loaded & fired approx. 100 without any further problems! My only advice is to be sure that you do the annealing process correctly! There are many opinions out there, but from my experience & what I have read, any process that involves heating the necks to a cherry red color is not correct!
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