Annealing Brass

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denton

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Here is an update to my video about annealing brass, showing improvements I've made to the system.



For those who want to duplicate this method, here's the shopping list: Lee lead melter, $38; lab stand and burrette holder, $21; one pound each potassium nitrate and sodium nitrate, $20 total; controller and solid state relay, $14; high temperature K thermocouple, $5.

If you're going to use this system, wear gloves and eye protection!
 
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I have a hard time believing them.

The rate at which annealing happens is linear with time, but exponential with temperature. Reloaders typically try to run at around 700F or so, which makes the process easy to control. Running at 820F makes the process happen a lot faster.

When you anneal with potassium+sodium nitrate, you can definitely feel the difference when you trim the brass. It trims like butter. In addition, I did the test that I described: Cut two identical pieces of brass, and flexed one back and forth with pliers until it failed. It only took about 8 90 degree bends back and forth. Then I annealed the other piece, flexed it back and forth 6 times, annealed again, and repeated until I had over 100 bends back and forth. I decided it was more durable than I am.

To believe the claim that salt bath annealing does not work, you have to believe that there is something special about the heat from the nitrate bath that makes it not anneal, while heat from induction or flame will anneal.
 
I dip mine in melted lead after dipping in oil. Nothing sticks and I am going to size and clean after anyway. If you are not casting this sounds like a great alternative for cheap.
 
denton said:
I have a hard time believing them.

The rate at which annealing happens is linear with time, but exponential with temperature. Reloaders typically try to run at around 700F or so, which makes the process easy to control. Running at 820F makes the process happen a lot faster.

When you anneal with potassium+sodium nitrate, you can definitely feel the difference when you trim the brass. It trims like butter. In addition, I did the test that I described: Cut two identical pieces of brass, and flexed one back and forth with pliers until it failed. It only took about 8 90 degree bends back and forth. Then I annealed the other piece, flexed it back and forth 6 times, annealed again, and repeated until I had over 100 bends back and forth. I decided it was more durable than I am.

To believe the claim that salt bath annealing does not work, you have to believe that there is something special about the heat from the nitrate bath that makes it not anneal, while heat from induction or flame will anneal.
Click to expand...

I agree. I haven't went to the extent of testing like you did but I do think the salt bath makes a difference and it is all about heat. I thought they may have been comparing brass straight out of the annealer against brass that was salt bath annealed and then sized. The sizing would raise the brass hardness considerably. I'm not trying to knock their extensive work in the field of annealing nor do I think salt bath annealing is for everyone but I do think it works.
 
denton said:
I have a hard time believing them.

The rate at which annealing happens is linear with time, but exponential with temperature. Reloaders typically try to run at around 700F or so, which makes the process easy to control. Running at 820F makes the process happen a lot faster.

When you anneal with potassium+sodium nitrate, you can definitely feel the difference when you trim the brass. It trims like butter. In addition, I did the test that I described: Cut two identical pieces of brass, and flexed one back and forth with pliers until it failed. It only took about 8 90 degree bends back and forth. Then I annealed the other piece, flexed it back and forth 6 times, annealed again, and repeated until I had over 100 bends back and forth. I decided it was more durable than I am.

To believe the claim that salt bath annealing does not work, you have to believe that there is something special about the heat from the nitrate bath that makes it not anneal, while heat from induction or flame will anneal.
Click to expand...

[edit- i misread denton's procedure, so removing my observation as it was irrelevant]

i haven't heard the claims from AMP that salt bath doesn't anneal but offhand i'd think any heat source is capable of annealing. the value of the AMP system is it results in the right hardness.
 
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@taliv

AMP Article: Salt Bath Annealing - Does it Work?

Their data suggests it doesn’t work under the prescribed method, 5-8 seconds at 500-550C, and if held long enough to significantly soften brass, it ends up producing an undesirable hardness profile through the neck, shoulder, and submerged case body. The equipment used in their testing and the methodology are quite different than the testing described here.

Trust in God, others, bring data.
 
very interesting. thanks for posting that varmint.

i suppose everyone is curious as to why their results so consistently show the neck doesn't get soft enough, while the body gets too soft.

denton said:
To believe the claim that salt bath annealing does not work, you have to believe that there is something special about the heat from the nitrate bath that makes it not anneal, while heat from induction or flame will anneal.
Click to expand...
no, that doesn't seem like the logical conclusion to me.

i could be wrong, as i majored in business, but it seems like you measured ductility and AMP measured malleability. ductility in our application is useful as it is involved in the brass expanding in the chamber without the neck splitting. malleability, is probably more relevant to how consistently "neck tension" is applied to a bullet.

i don't know if it's possible to anneal brass such that ductility is restored while malleability/hardness is not.
perhaps in this case, the word "anneal" doesn't sufficiently describe the objective.

going forward, i think rather than debating whether we have or have not "annealed" a piece of brass, we should rather state a goal in terms of hardness or ductility or whatever, measure it, and show whether we have achieved it.
 
Malleability and ductility are related, M is how well a material can be compressed/Flattened/shaped. D is how much the material can be stretched before breaking. Those properties are affected by the composition of the metal. Annealing brass restores the ductility because it has been work hardened by sizing and stretching to fit the chamber.
 
AMP measured hardness, which is a material's resistance to deformation. Probably the more important property to reloaders is ductility, which is the material's ability to be deformed without breaking.

In most cases, hard substances are less ductile than soft ones. Since ductility is more difficult to measure than hardness, it is common to measure hardness instead.
 
I do very little rifle shooting these days when I did a propane torch and pan of water served well or so it seemed. I guess we are talking different approaches. Then I was only interested in neck and shoulders. These threads often take a technical turn that is quite frankly over my head.
 
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