Why does annealing work?


Well-Known Member
Feb 3, 2009
Almost everyone who anneals their cases finishes the job by dropping it in water.. Isnt this the exact thing that a Blacksmith will do to harded steel. Get the metal red hot and then dip it in water? So why does this process soften brass? Im getting ready to start annealing because i have noticed the neck tention is not as constant as it used to be. But I couldn't help but question why it works?
the best answer will come from a metallurgist. Annealing brass softens it after it has been work hardened, which occurs during sizing, pulling the button through, firing, etc. Annealing basically re-establishes a better consistency of the metal.

If you want consistent neck tension, anneal frequently. I do it after every firing because it is so quick. I do not quench in water. That is done to keep the heat from traveling down the case below the shoulder. Most annealing machines I've seen have no quenching process.
Brass and steel, very different metals, very different properties. You're right that quenching is can be an important part of the heat treatment of various steels, but as Derek said, it's not a factor with brass. You can quench it or not, and it makes virtually no difference in the annealing itself. One's messier and involves an extra step (drying the brass), so why bother?
Kevin, I'm curious about Lapua's technique. Is it a big secret? I've been annealing for quite some time and it's only on occasion that I get cases that look just like a new Lapua case. Why is that?
As I recall, I believe it's an induction annealing process. Standing upright, the cases pass between a set of heating elements "aimed" at the neck area of the cases. The trip takes only a few seconds, but it's enough. Annealing is a combination of both time and temperature, and there's a very specific range of hardness and ductility that has to be achieved for the finished product to come out right. The typical discoloration is the result of that brief passage.

A word of clarification is in order here; we're not the only ones who anneal our production brass. ALL manufacturers (that I'm aware of, anyway) do the same thing, including military operations like Lake City. It's a virtual necessity, considering how much work hardening occurs when the neck and shoulders are formed on most bottle necked cases. Most go ahead and polish this discoloration out before selling he cases. The military doesn't because sales appeal makes absolutely no difference to them, and we don't because customers seem to like it. Either way, if it's a bottle necked case, it got annealed at some point.

The visual appearance can be duplicated, but it doesn't necessarily mean the annealing was done correctly. For that, you need to go to something like the tempil sticks, or some other means of measuring the actual temp transferred to the brass. Start with highly polished and very clean brass if you want to duplicate that appearance, but I'd say priorities are better directed at making sure the temp is right, regardless of the look. So no, no secret to the process, and it's pretty much the industry norm.
To begin, we don't actually desire to 'anneal' brass, but stress relieve it. Quenching doesn't affect the grain structor of brass. We quench after heating to stop the relieving process from affecting areas we don't desire to affect.
With proper technique the only time quenching would be needed is with deep body stress relieving(to produce big body/shoulder changes on wildcat fireforming). Quenching here would prevent stored heat from sinking into the case web.
So if you're talkin necks to neck-shoulder only, quenching can be skipped.

On a side note, don't attempt to do deep body treatments with torches. Don't even try induction heating for this, without high dollar process controls in place.
You'll just dramatically reduce brass life..
It's a task best suited for lead dip, followed by quenching.
Kevin, thanks for the post. I was aware that all bottleneck cases are annealed no matter the brand. I actually enjoy annealing the necks. I began with the first 5 or 600 rounds using temp liquid painted on the case until I found that repeatedly, it took roughly 6-7 seconds per case in my torch no matter the brass with the slight exception of Remington. That was about 7-8 seconds.
I tried a number of the manual annealing processes that are out there and never felt I was getting consistent results. I eventually gave up on the process.

When I finally decided to get serious about it I bought a Bench Source annealing machine and man what a difference. I saw an across the board improvement in groups and one rifle in particular (Shilen Barreled .204 Ruger) absolutely came alive. That rifle wit from shooting in the 6s to shooting in the 2s and 3s at 200 yards, amazing. Now it is so quick and easy I anneal after every firing in every caliber, there's just no reason not to keep that consistency advantage.

There are a number of good looking machines out there, but I have nothing but good things to say about the Bench-Source unit if you are shopping for one..
Brass work hardens with use.

If you have seen the brass being formed you will understand why the neck and shoulder
area is annealed. (The more you work it the harder it gets and the necks are worked the

Some factory brass is polished after it is annealed to look good. I prefer the as is look like
Kevin for several reasons. It is proof that it has been done, (Sometimes I wonder if this
step was left out to save money) If so the brass will probably split after one or two firings
and it tells me how far the annealing process was carried out.

The reason we quench the brass is to catch it at the right hardness. now that we have the
annealing machines it is not as important because of the consistency of the process. When
we did it by hand it was a way to keep from allowing the heat to reach the base and soften
it and if the water level was set right we annealed only the part of the case that received
the most working from expanding and then sizing back down.

Each time you size the brass you add stress and it hardens a little more. annealing removes
this stress and returns it to it's softer state so forming is easier,And splitting is less of a

There are different alloys used in brass and the looks will tell you that they are different but
not what they are. the results will look different depending on the alloy of the brass.

If you take a piece of steel wire and bend it back and forth enough it will break because it
has work hardened. Brass will also do the same thing.

I believe that "look" of annealed new lapua brass and some military brass comes with time and aging/oxidation while in storage. Some of the brass I have annealed if left long enough will get that look. Brass annealed at home may or may not look annealed, but will perform according to the uniformity and correctness of your annealing process.

I quench after annealing to insure that the process stops immediately and does not continue to heat the case web. Also H2O seems to cushion cases as they fall so I don't get a dinged case neck while hot. Heat travels very quickly down brass. If you want to see for yourself, grab a cull piece of brass, heat up the neck with a torch and see how long you can hold it by the base. Quenching sucks because cases have to dry. It's your choice.
Do i have to full lenth size after annealing ? Or can i just neck size. I use a bench source automatic annealing. Thanks for your input.
No need to full length size if that is not your normal practice.

I clean cases, anneal necks, then continue with normal brass prep for whatever caliber.
flr or neck size only as long as the shoulder gets bumped back, then reload as usual. just make sure there are no live primers in before you anneal!!!
Thanks for input. I knock out the primer with a universal die then i put the cases in a altrasonic cleaner. Then wash then. Then annealing. Then neck size. My brass is not as shinney as i would like. Is there something i can put in the altrasonic cleaner to make the brass shine better.
Warning! This thread is more than 13 years ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.