Annealing/Drawing

[blackthorn]

On another thread I saw a reference to using molten lead to both 'anneal' and to 'draw' cartridge brass that was either over-worked or close to being so. Could someone please explain the difference between the two (and the process used) as it applies to brass cases?

[floodgate]

blackthorn:

They are really the same as applied to brass; both terms are "borrowed" from carbon steel metallurgy. If you start with piece of hardened carbon steel and wish to soften it, you "anneal" it to "dead soft" by heating it above the "critical" temperature (bright cherry red, IIRC), then let it cool slowly (packing it in hot ash or sand helps). If you are "tempering" steel (to get a specific combination of strength and flexibility), you heat it above the critical temperature and quench it FAST in cold water or oil. That takes it to maximum hardness, but leaves it very brittle. You then "temper" - or "draw" - it by heating it again, to an appropriate lower temperature (dark blue for springs), and letting it cool again. Brass (and alloy steels) all behave differently; brass hardens as it is "cold-worked" in shooting and re-sizing; heating it above a (much lower, 700 - 800* F) critical temperature, and then cooling it - fast or slowly - makes it soft again. You can speak of the process as either "annealing" or "drawing", and people will generally know what you mean. (Actually, you can "draw" it to an intermediate hardness level by careful manipulation of temperatures and heating/cooling rates; this is done in factory cartridge cases, but is a bit beyond most of us.)

(Tungsten, for a contrary example, is very hard and brittle as smelted, but "work softens", and has to be beaten and pummeled to make it malleable enough to be drawn into lamp filaments.)

There, you've exhausted my knowledge of metallurgy - and then some.

floodgate

[MtGun44]

Annealing is a process of removing hardness from a metal by heating it high
enough to untangle the accumulated dislocations in the crystal lattice. When
the dislocations (errors or mismatches in atomic stacking structures) are
minimized and not tangled up, the dislocations can move easily, so the metal can
permanently deform more easily (it is soft). As you permanently deform a metal, the
dislocations move and when they strike another dislocation the two tangle
and are stuck, so the metal cannot permanently deform as easily (it gets harder).

This hardening due to permanent deformation is called work hardening. Brass
can only harden by work hardening, unlike steel which can harden by rapid
cooling from high temperatures to freeze in harder microstructures, a process
called quenching. After rapid quenching, steel alloys are the hardest that they
can be, but are also at maximum brittleness for that alloy and quench rate.

Drawing is a term usually applied to steel alloys and is a process of heating to
a particular temperature after quenching to reduce hardness, with the primary
intent usually being to reduce brittleness. The correct technical term is tempering.
By tempering to different temperatures, the desired balance of hardness and
brittleness can be reached for the particular alloy.

Drawing is probably being used to refer to a partial annealing of brass as opposed
to a full anneal. A full anneal would take the brass all the way back to it's softest
condition, I presume drawing could (at least theoretically) take the brass to a
desired hardness between maximum work hardened condition (hard and brittle)
and maximum annealed condition (soft and malleable). I am very familiar with
the quenching and tempering of steel, but much less so with brass. I am not
absolutely certain that you can obtain intermediate hardness levels by heating
work hardened brass to specific temperatures, but it seems reasonable that you
could.

Bill

Edited - sorry for the redundancy, floodgate replied while I was typing mine!

[floodgate]

MtGun44;

That's just fine; two heads are better than one - especially when they agree. I was feeling sorta shakey, working from a 76-year old memory.

floodgate

[Single Shot]

So which is best for brass cases?

Two different reasons.

1. Want to soften work hardened cases.

2. Want to soften cases to run them into a different full length sizing die to form a different case. I plan on using the old 30 Remington, to form 5.45 X 39.

[montana_charlie]

So which is best for brass cases?
Heat it quickly to 650 degrees, then let it cool. It doesn't matter whether it cools fast, or slowly.
CM

[mike in co]

So which is best for brass cases?

Two different reasons.

1. Want to soften work hardened cases.

2. Want to soften cases to run them into a different full length sizing die to form a different case. I plan on using the old 30 Remington, to form 5.45 X 39.


ok i'll bite...why do you want to make cases that are available.....just cause you can ???

220 russian and 7.62 x39 are both available.....seems eaither would be simpler than the 30 rem.

mike

[HORNET]

You don't want to anneal more than the case neck and shoulder in either case. Annealed case heads are prone to primer pocket expansion, bulging, and other bad things. It's usually better to anneal AFTER forming down, keeps the shoulder from turning inside out. The old timers (no further comment [smilie=1:) used to recommend dipping the case mouth in graphite or oil, then sticking the case mouth into the molten lead until the case head got too hot to hang onto, then flicking it to remove any semiattached lead, then quenching it to limit annealing distance and prevent overheating the case head.

[kawalekm]

Dean Gennell mentions this in one of his ABC's of reloading books. Specifically he states that you want to anneal the mouth of the cartridge case only. The base, which holds the primer must remain hard. He described a specific procedure to do this. His instruction was to hold the case by the head (rim) with your fingertips and place the mouth only of the case into the molten lead and keep it there till you start to feel the heat reaching the case head. At that point immediately drop the annealed case into cold water to prevent the heat from annealing the casehead. As you dip the case in lead, count how many seconds it took for the heat to conduct into the head area. From that point onwards you can hold each case in the lead with tongs or forceps, counting off the same number of seconds as with the finger-held case. Using this technique you can safely and uniformly anneal all your casenecks.
Michael

[Ricochet]

I've tried the molten lead method of annealing case necks of work hardened brass that will no longer hold a bullet after collet sizing. Can't tell it makes any difference with the Lee pot turned up as high as it will go and equilibrated, dipping the neck only and holding till it gets too hot to hold with bare fingers at the case head (30-06). Looking at the specs for cartridge brass in the Metals Handbook, the lead ought to be above the minimum recrystallization temp for the brass, but the way I understand it that takes more time; annealing temperature's considerably higher. I don't have the book in front of me right now for the specific numbers.

[JohnH]

I've tried the molten lead method of annealing case necks of work hardened brass that will no longer hold a bullet after collet sizing. Can't tell it makes any difference with the Lee pot turned up as high as it will go and equilibrated, dipping the neck only and holding till it gets too hot to hold with bare fingers at the case head (30-06). Looking at the specs for cartridge brass in the Metals Handbook, the lead ought to be above the minimum recrystallization temp for the brass, but the way I understand it that takes more time; annealing temperature's considerably higher. I don't have the book in front of me right now for the specific numbers.


OK Ricochet, some plain language please. ( I understand most of what you and others have said) If you mean that you've experimented with annealing using the molten lead method and got no results, I agree. I've done the same and can't tell it made any difference. I'm headed toward making an annealing setup using an old record player, a bowl and a fine tip for a propane torch (search my name and annealing, there is an old thread on this in which some here share their tools of the craft) It is a skill I'd like to learn, as much to know it as to use it.