Metalurgy question...

[montana_charlie]

Ok, I know that we have guys who are well-aquainted with some areas of firearms-related metalurgy. Taking lead alloys, I am aware of several methods of using heat (or quick cooling) to manipulate the hardness of bullets.
From discussions on that subject, it appears that after the manipulation is done, remelting the alloy and casting a new bullet returns everything to 'square 1'.

My question concerns brass cases.

After being fired enough times to have become 'work hardened', annealing a case makes it 'soft', again. How soft depends on the annealing temperature used.

If I have two cases which are identical in every way...except one has become quite hard, while the other has only gone half as far...

Will annealing those two cases (being carefully uniform) return them both to the same state of hardness/softness?

It seems to me that it should...whadayathink?
CM

[scb]

"It seems to me that it should...whadayathink?"

I agree.

[felix]

Yes, depending on time and temp together. Have to have a minimum temp to allow the process to begin. Threshold 300 degrees? I don't know; what do gaschecks do? For example, try, for kicks, 400 degree oven for 15 minutes exactly. Mash a case in some kind of feel good job, like a large pliars. Compare different cases at different PRODUCTS (temp*time) with same pliars. Water drop to get case down below the threshold pronto after oven. Do one case at a time until you get a feel of what is going on. When you find out, PLEASE TELL ME WHAT HAPPENS. I need to do several thousand pistol cases. ... felix

Hot flash: call Starline and ask them. Keep in mind their cases are thicker than normal, so cut that PRODUCT by 50 percent for trials for the thinner cases. You want the case head to stay close to the same hardness, but the uppers quite soft. ... felix

[Dale53]

I believe trying to anneal the whole case is a serious mistake and can potentially lead to disaster. You really only need to anneal the case mouth and you DO NOT WANT to anneal the case head AT ALL.

If you want the REAL story on case annealing, get a copy of Ken Howell's book "Designing and Forming Custom Cartridges". There is entirely too much BAD information out there on case annealing. My motto on case annealing is simple, "Either know exactly what you are doing or don't do it at all."

Dale53

[felix]

I agree with Dale, CM, across the board. But it appears you are an experienced person and won't do anything foolish with questionable results from the process. The BR folks don't anneal, but just throw the cases away. It must be extremely difficult to get uniform results, for BR work anyway, between all cases in a lot by using home techniques. Otherwise, the BR folks would be doing it in lieu of the work required to prep a brand new case. ... felix

[montana_charlie]

Well, I have read a lot of articles on annealing, and believe I have a good grasp of the requirements. And, I have annealed a particular 'set' of cases a couple of times with the desired results.

I have a second set of cases which is 'younger' than the other, but they are identical in all other ways...headstamp, lot #, and weight. I would like to combine the two sets into one large one, without erasing the consistency. I figure the best time to do that might be right after annealing both sets.

As to consistent annealing for those BR guys...
There is the Ken Light annealing machine that the BPCR crowd has come to love. At $350 a person might like to build his own, but it is a 'heavy metal design' that would be hard to duplicate in the home handyman's shop.

Then, there is this baby...
http://www.zephyrdynamics.com/page3.html

I expect the $400 price tag is to recover the cost of materials ruined while trying to get this working...because the final product certainly doesn't take that much to build.
But the design is so straightforward that most anybody with a sewing machine motor can build one.

Watch the videos to see how 'consistent' it is.
CM

[felix]

That is exactly the way Olin does it, but the circle itself is a half circle at the end of a long "assembly" line. Actually, the line has natural gas fired nipples where ever a half-circle exists (needed) during the draw stages. ... felix

[JIMinPHX]

With steel, heating then quenching hardens it & heating then slow cooling it anneals it. I think that cartridge brass responds the opposite way. I think that quenching anneals it. I need to go grab the Machinery's Handbook & look up the heat treat spec's for alloy 260 (cartridge brass). I've been away from heat treat for a while now & the info off the top of my head is getting a little thin.

[JIMinPHX]

The Machinery's Handbook is a little thin on that alloy. Solution hardening temperature is listed as 1450-1650 F with a precipitation temperature being listed as 600-900 F for copper alloys in general. There's no real good info that I can find on the annealing process in that book. I'm a little disappointed.

[montana_charlie]

That's Ok, Jim. I feel sufficiently well-informed about temperatures and heating/cooling times.
I'm just wondering if two pieces of brass, having different degrees of hardness, will both revert to the same softness if annealed identically.
CM

[felix]

Again, yes, CM. Just make sure the PRODUCT is large enough to cover the hardest one. ... felix

[montana_charlie]

Well, I have received one "I agree" and a couple of "Yes, if the PRODUCT is correct".

I guess I will go with that...and my product will be 650 degrees and an 'eight count'.
CM

[felix]

The RATE of cooling, heating has nothing to do with brass. Only the PRODUCT is significant after the minimum temp threshold has been exceeded. ... felix

[Bass Ackward]

I'm just wondering if two pieces of brass, having different degrees of hardness, will both revert to the same softness if annealed identically.
CM


Charlie,

From my experience, yes and no.

1. If you are talking the same lot of brass and some has just been reloaded more than the others or in other dies, then yes, assuming equal heat and time.

2. No, if you have brass from the same lot that has been fired the same number of times reloaded in the same dies, which should all still all be the same just harder. If it is not, then you have a problem that equal heat and equal time (annealing) probably won't correct. But it will be closer than it is now.

3. If you are trying to anneal pieces from different makes and manufacturers, the answer is clearly no, but it too will be a heck of a lot closer than it is now. The heavier the anneal, the closer it will all be, but you have to get good at it to tell without destroying the brass.

The way I look at it is if it ain't what you want now and your only option is to toss it, what do you have to lose? Consider it another form of education and as we know, all education costs. But as Felix said, method is everything. And the Hornady system is as good as any.

[montana_charlie]

Thanks Mr. Ackward. I described the identical nature of the cases in Posts 1 and 6.
CM

[JIMinPHX]

Yes & no on effects of previous hardness -
If you go all the way up to the hardening temperature for the proper soak time, then the previous hardness has no effect anymore. If you only go up to a tempering temperature, then the previous hardness makes all the difference in the world. That has been true for every metal that I have ever heat treated.

[sjohnson]

Here's a lengthy read from 6mmbr.com. These guys get serious about it and describe a home-built production system:

http://www.6mmbr.com/annealing.html

I do piece-wise annealing using a Lee case holder/spinner and Tempilaq to guage temperature.

[montana_charlie]

Thanks for the link, Mr. Johnson, but I have already absorbed that article. It features the Ken Light annealer that I mentioned earlier in the thread.

Thanks to all for their replies. I seem to have received confirmation (mostly) of what I already believed, so I will go with that for now. The total number of (my) cases that fit in this category is small enough that it won't mean financial ruin if the supposition is wrong.
CM