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Why does annealing work?

 
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Old 11-19-2010, 12:37 PM
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Why does annealing work?

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?
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Old 11-19-2010, 12:56 PM
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Re: Why does annealing work?

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.
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Old 11-19-2010, 01:20 PM
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Re: Why does annealing work?

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?
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Old 11-19-2010, 01:27 PM
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Re: Why does annealing work?

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?
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Old 11-19-2010, 01:53 PM
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Re: Why does annealing work?

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.
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Old 11-19-2010, 02:14 PM
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Re: Why does annealing work?

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.
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Old 11-19-2010, 07:30 PM
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Re: Why does annealing work?

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.
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