Mikecr,
Thanks for the links, there's lots of good info in there.
I'm taking an excerpt from the Experiment pdf
This experiment deals with three very specific types of heat treatments. Each is concerned with producing the desired properties by means of producing the required microstructure. These heat treatments, their objectives and the resulting microstructure are:
Stress Relieving Stress relieving reduces or eliminates residual stress, thereby reducing the likelihood of failure during service, usually by stress-corrosion cracking. It can also be used to improve dimensional stability. Stress relieving temperatures are below the recrystallization temperature. While stress relieving near the recrystallization temperature will require shorter times and will be a more economical process there will be some loss of strength. Using lower temperatures and longer times will preserve strength and will even increase it slightly if the material had been severely cold worked.
Recrystallization Recrystallization is characterized by a rapid change in tensile properties and the formation of a new, strain-free microstructure. Between 35 and 60% cold work is required before recrystallization can occur with increasing amounts of cold working lowering the recrystallization temperature.
Softening, annealing Softening is achieved by heating to well above the recrystallization temperature and holding for whatever time is required to complete the recrystallization process and obtain the desired grain size. Annealing is often used when the material will receive further cold working.
To me, what it is saying about stress relieving is that you end up with brass that is less prone to stress-corrosion cracking. The same loss of strength is going to happen regardless if you anneal or SR. Your SR is done at a higher temp than the one in the datasheet anyhow, which says 500 for an hour. And of course you knew that already.
Recrystallization has no target temp to do is, but is going to change as the brass gets older. I happen to have a lot of very old brass that's been cold worked 30-60 times. Actually, you could say many more times over than that because I do multiple operations on them each firing.
Softening, Annealing if you take a look at the very last sentance says "Annealing is used when the material will receive further cold working."
Now, if you're shooting a PPC, or a very tight neck case, then by all means, the stress relief may be something to look into to make the brass last longer. Don't work that brass in a die. However, if the cases are going to get cold worked (grow in the chamber) and get cold worked in a die, then that is not what you're looking for if you want the longest life from them. For those of us who shoot chambers with more neck clearance, there's no way I can just stress relieve the brass and expect it to survive. It just won't. Also, the necks get so tough, you can't expand them without deforming the rest of the case. Even a few thou of expansion takes a LOT of force.
Last but not least, these temp sticks people use don't really tell you much about the neck. Most people say put the stuff on the shoulder and then anneal (/sr) and the fact is the neck is a TON hotter than that shoulder is. I'd bet that most folk who anneal that way have necks 300f or more higher than they think they do. I do not have any way to check it because a case changes in temp so fast, I don't know what instrument you could use to check it. I have seen thermocouples in heat treat ovens though, and over the years have gotten to where I can pretty much guess a temp pretty close most times. From 900-1800 anyhow. At 800, there is virtually no glow. Even at 900, it's very slight. At 1000f it's begining to get light in the oven. at 1200 things are clearly red, by 1500, they light up a dark room when you pull a large part from the oven and at 1750-1800, they're bright yellow and that parts get'n pretty toasty. You can see through a stainless steel bag there. When putting heat on a neck, I'd say I've seen mine get to 1400 before. Not often though, I don't like to go that high.
One other thing that nobody has said here. A great way to make cases anneal softer without taking the temp quite so high is to quench in icewater. That REALLY softens em up. So if you want a little more cold workability without all the temp and burn marks, use icewater.
. Now place the brass in the cylinder after you lit the torch.