Please break down annealing for me from a metallurgical point

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WestKentucky

WestKentucky

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I understand that annealing and quenching makes metals harder, softer etc based primarily upon grain structure which is a function of heat. I do shoot a few calibers which cannot be purchased anymore and want to protect and preserve my "correct headstamp" brass so I know I need to anneal, but feel like I would be better served to understand the background before I jump into this feet first. I also understand that quenching changes things drastically so rapid air cool (dry ice fume) motor oil, water all will do different things. Which works best, why? I also see from another thread the how-tos but never any well explained reasoning on the why. Please educate me, link me to old threads, or otherwise dispell myth and get down to the meat (what to do) and taters (reasoning) of annealing cartridge brass.
 
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Quenching does nothing for cartridge brass.

Heat the necks with a micro torch for better temperature control until the brass changes color from shiny brass to a dull bluish brown like on military ammo. That's it.
 
Ferrous metals benefit from quenching, brass doesn't care as it can only be work hardened, i.e. hammering it or firing it in a gun. There is chemical hardening but it doesn't apply here unless you use a cleaner with ammonia in it.
 
Rapid cooling of steel after it is heated to the point that it has no magnetic properties hardens steel. It will do the same to brass but not to the point you'll notice it. The only reason you quench brass is to preserve the head, meaning not to anneal the head.

I'll equate annealing to full length sizing. If you only neck size, a full length size will eventually need to be done or the brass will be junk.

After too many sizings, if not annealed, the necks will crack and be made junk.

There are consistency benefits to annealing as well.
 
Annealing

http://heattreatment.linde.com/International/Web/LG/HT/like35lght.nsf/repositorybyalias/wp_semifnshd_22/$file/22.pdf annealingABC.jpg Note that the atmosphere is controlled in factory ovens. High temperature will deplete the zinc if not done correctly. There are Hornady Annealing Kits available & Tempilstik & Tempilaq that may help. But when you overheat the brass, there is no way to fix it.
Cartridge Brass-
Material is 70 copper/30 zinc with trace amounts of lead & iron , called C26000. Material starts to yield at 15,000 PSI when soft (annealed), and 63,000 PSI when hard.
Material yields, but continues to get stronger up to 47,000 PSI when soft, and 76,000 PSI
when work hardened.
Click to expand...
 
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A source of data for cartridge brass given to me by a metallurgist friend. See annealing temps in the second table, second row from bottom.

http://www.lfa-wire.com/70-30-brass-wire_c26000.htm

Most of my experience that I can quantify is from making .22 cal bullets from 22 lr brass with Corbin swaging dies. I can quantify my results by the percentage of points that split when forming the bullet. I've tried a 450 oven overnight (virtually no effect, a waste of time), oven cleaning cycle (minimal effect, turned the oven racks blue and got me in trouble with the missus), and finally a laboratory oven (1000 F for an hour gave 98%+ successful bullet points). The caveats are that I'm not sure that 22 brass is 70/30 cartridge brass and dead soft is best for bullet making.

Laphroaig
 
"it will do the same to brass"

Brass does not harden from quenching.
It serves to remove heat from the case to prevent it from softening the head.

Steel harden since its atomic arrangement changes as it is heated, and the 'hot' arrangement stays in place by quick cooling.

The heat capacity of the quenching material really maters.
Oil has a higher heat capacity than water.

Water hardening steels are designed to quench in water, oil hardening in oil.
Used motor oil works fine for small pieces, but be ready for some flames.
New 80W gear oil works for slightly larger pieces.
 
Yes it does. But like I said not at a noticeable level. Quenching any metal will harden it, some more than others. Heated to dead soft and heated to the same level then quenched will produce a slightly harder alloy. The reason being the metal has more volume being hot then then the subsequent cooling contracts. Think of it as micro work hardened.
 
Brass does not undergo an atomic structural arrangement variation when heated.
It will not harden.
 
More confused now than before. Maybe I opened Pandora's box of information.
Click to expand...

For me it was a matter of deciding there were rules,

F. Guffey
 
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I agree, full-length annealing with a hardening of the head afterward probably offers best chance for replicating original process and producing gorgeous brass. I'll settle for functional brass. Winxb you are a trip man. Cracked ammonia?
 
Excuse me, I should have said "I would agree..."

I also would agree that the case head is going to be the critical point. For the casual annealer, simply checking BHN and finding a repeatable process would suffice. I can't speak for commercial enterprises; corporate language and contracts are beyond me but it would probably involve periodic inspections with no room for error. Bummer.
 
That's it, everything a reloader ever wanted to know about annealing, but the answer to the OP's questions.

I would be better served to understand the background before I jump into this feet first. I also understand that quenching changes things drastically so rapid air cool (dry ice fume) motor oil, water all will do different things. Which works best, why? I also see from another thread the how-tos but never any well explained reasoning on the why.
Click to expand...

F. Guffey
 
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Water quenching only helps stop the heat from migrating down the case from where you want it. As posted, it doesn't matter if you air cool, quench etc. The water is to keep the bottom part cool, and knocking it over draws out the heat. Knock it over, pull it out, go to the next one. Change the water when it gets warm.

Water is only needed if you are heating the case so slowly that it could migrate down to the case head before the neck and shoulder are annealed.
Click to expand...
Exactly. Sort of like soldering a ball valve onto a piece of copper. Get on it with the flame, solder it, get off of it, with a water soaked rag laying over the body of the valve. Use enough heat to do it quickly, but not excessive heat. :)
 
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