6mmbr's annealing temperatures seem questionable...

kombayotch

kombayotch

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A friend was nice enough to lend me his collection of Tempilaq so that I could set up my CNC Annealer before ordering my own. Unfortunately, he needed it back, and I still haven't ordered some of my own. The reason for that is that I've been troubled by my observations not matching up with what is described in the 6mmbr Annealing Article and other information being thrown around in shooting forums, in terms of temperature values. Well, I decided to blow the dust off of the old Material Science book and look up the proper temperatures so that I could order the right temperature values of Tempilaq. Well, the numbers were completely different than what's written on 6mmbr, they were in every reference source, for every grade of brass similar to cartridge brass. The material science books all agreed with each other on one thing though: actual annealing BEGINS at 800 F, it doesn't end there.

Brass.jpg



I started thinking about it and realized that my annealer works quite a bit differently than the rotary ones... The computer controls the the exposure time to an accuracy of a few milliseconds. I push the case into the flame and pull it out of the flame much more quickly, without any pre-heating or post-heating from the rotation in the same axis of the flames. I thought about the differences, and then the obvious dawned on me: we're heating the cases with a torch and the flame is at a much higher temperature that we are trying to hit.

Propane.jpg


Its going to be even higher if you're forcing oxygen into it (which some torches do by design, without an addition tank) and higher with MAPP gas. So his assertions about holding the necks at any temperature for any lenght of time is not possible to do. Even being conservative about, you're still probably putting the case into an area of the flame that's over 2000 F. You're cases are going to shooting up in temperature until they either reach the same temperature as the flame, or you pull them out them. The heating is dynamic, there is no holding them at any temperature below the temperature of the flame, its always changing.

Now, brass isn't a perfect conductor, it takes time for it to heat up and for the grain structure to change once it does, but this still probably has a lot less of a lag to it than the time it takes for the heat to transfer to the Tempilaq and melt, which is much less thermally conductive than the brass. So, if you're using 750 F Tempilaq inside of the neck, the brass has probably exceeded 800 F when its only started to melt and has shot quite a ways past it when its fully melted. I saw this. If I put 750 F Tempilaq and 850 F Tempilaq in the same neck, it was not possible to get the 750 F Tempilaq to fully melt or even partially melt without the 850 F Tempilaq starting to melt. 800 F Tempilaq surely would have melted to some point in between. Parts of the brass itself were likely over 900 F. I could totally melt the 850 F Tempilaq without fully annealing the brass. I have to go a bit longer to succesfully do it. How do I know it wasn't fully annealed? Because it had the same spring back as the un-annealed brass does after resizing. I tests this with 0.0005" gage pins when I manually anneal (and whenever I resize) to know that the cases are actually holding consistent neck tension.

The numbers being put forth in that article are possibly based on his observations from heating with the torch while trying to measure temperatures in some way. But, he isn't taking the thermal lag of the measuring method into consideration, which is why the numbers don't agree with the science books. You aren't going to be able to accurately know what the temperature of the brass is heating it with a torch and trying measure it with an instrument or Tempilaq, due to these having much larger lags. The brass is changing temperature much faster than these can keep up with when you're sticking it in a torch. The only way to draw any kind of accurate description about things like what temperature glowing starts at are going to be to put the material in an oven, at a fixed known temperature and let it reach that temperature.

Its always bothered me that the setup instructions for these machines were only using one value of Tempilaq at a particular location. You can't put boundaries on a process from only one side, which is what you're doing of you're not putting a higher value of Tempilaq that shouldn't melt at the same location as one that should. This is what you should be doing if you're shooting for a certain temperature range. There will also be a lag and the true upper boundary will also be higher than the Tempilaq value though.

If the annealing of brass does happen above 800F. Then we're just overshooting the Tempilaq values due to the better conductivity of the brass under the fast heating of the torch. Its like controlling the Mars rover. It isn't going to stop where you see it on the screen when you tell it to. Its already gone past that point due to the lag in transmission. Maybe my machine has a different communication link than the other rovers, because if I go by 750 F Tempilaq melting, my brass isn't getting annealed. It would also explain why the 650 F Tempilaq works for some people. Different torches would make a difference too... This does make me wonder how many people actually verify their annealing by measuring the spring back in the necks before and after, rather than just taking the info at face value.

Maybe I'm way off here, but I'm having a lot of trouble buying that the shooting forums have it right and the metallurgists are wrong. Especially when my results and observations imply otherwise. The information and the results tend to agree with the guy claiming to be a metallurgist in this thread: http://www.canadiangunnutz.com/forum/showthread.php?t=489825&highlight=tempilaq&page=3

I would really like to fully understand this process so that I can control it accurately. So, if I am out to lunch here, please point me to a credible scientific/engineering/manufacturing source that can explain the discrepancy.
 
Really interesting read. the origional way i had learned how to anneal was to stand cases up in a metal cake pan full of water up to the shoulder of the brass, and torch the necks until they turned glowing red hot then tipping them over into the water to quench. one at a time of course. has always kept my necks malleable enough without getting too scientific about it.
 
I use two cheap torches like you have in the vid, but I hold the case by hand slowly rotating in the flame.
I anneal in the dark (pitch black room) and pull the case out at the first sign of colour (dark orange).

I doubt my method is up to BR standards and I would like to improve it, but cases stop splitting and accuracy is consistent.

You should send an email to the guy that builds the annealing machines at 6mmbr and get his opinion?
I suspect when we anneal cases we don't need or want to fully anneal them?
 
What it ends up being is that you aren't using the Tempilaq to setup or fine tune the process initially. You're fine tuning the process by trial-and-error and then finding the right Tempilaq values to use as boundary flags so that you can verify things without all of the trial-and-error each time. Its only valid if the flame is also set to the same temperature.

You can set the flame up to a consistent temperature by sticking a piece of tube stock in it and measuring its temperature at a fixed point above the flame once the temperature settles. That won't be the temperature of the flame, but if the temperature at that point is the same as the previous annealing session, the flame temperature should also be the same as it was if your room temperature is the same. I suppose with that, just using the same exposure time is enough, once I figure out what that needs to be...

Thinking I don't even need the Tempilaq anymore. But, it would still be useful with the rotary machines since the exposure time isn't as easy to set.
 
You can check whether or not you're annealing by checking the spring back of the brass. A Lee hand press with a sizing die and some gage pins are handy for doing this next to the annealer.
 
I use a seating depth tension scale on the press arm to judge neck tension consistency.

You have taken a rather quantitative approach to the issue and that is refreshing. I have literally thousands of pieces of 6BR brass that I had put aside because of their neck tension issues. I began experimenting with annealing after I took the approach that I can't screw up a piece of brass I don't use anymore anyway...

I simply anneal by judging the patina. It has made the brass amazingly more consistent, and i anneal after every firing. I have also found that it seems to take a whole lot of heat over a long period of time to make brass unusable.

Scientific? Not a chance. But it does seem to work.

i would like an annealing system that was a bit less laboutr intensive, but it is cheap.
 
It rejuvenates the brass, no question about it. The 14x fired Lapua 308 cases I did the other night look and shoot like new brass after tumbling in the SS and annealing them.

Switching to the swirl flame torches (not in the video) reduced the time to anneal a lot give a lot better results.

An inductive annealing system could be made extremely cheap in China. Its on the order of complexity, and has similar parts to a cheap welder. Press mounted would work well, but it would still be a bad idea to use it indoors.
 
"The material science books all agreed with each other on one thing though: actual annealing BEGINS at 800 F, it doesn't end there."

This quote is very interesting information. I wish the article by Kombayotch would have stated the temperature that brass starts to turn red. I used to anneal by some means of keeping the base of the cartridge cool, while heating the necks until they started to turn red.
I used the starting to turn red method, because I observed aircraft engineers doing this with thick copper gaskets. The spark plugs on aircraft engines have a thick, maybe a twelveth of an inch thick, copper gasket between the spark plug and the engine. Everytime an engineer takes a spark plug out of the engine, he anneals the gasket before replacing the plug. Aircraft engines have two spark plugs in every cylinder, so the engineers are dealing with quite a few gaskets.
They string the gaskets on a small horizontal metal rod, suspended over a pail of water. With some minor tool, they push the front gasket to near the end of the rod, heat it with a torch until it starts to turn red, then push it off the rod so it falls in the water.
I have seen not one, but several engineers all do the same thing. I have great faith in the knowledge and ability of aircraft engineers, including tricky welding and working with metals.
I once posted on these threads about heating the cases until they started to turn red, and I got taken to task for it. I was told that was far too hot to get them and that it would actually deteriorate the brass case. The cases I annealed this way were well softened and worked fine. I have also used this method to anneal copper pipe for forming and it to, worked great.
Thus, whether my heating method is right or wrong, it certainly works for me and will be the method I will continue to use.
 
you need an electric element you can heat to the temperature you want for annealing. Stand the case on the neck on the element and mark it with temp marker at the point you wish to anneal to. When it melts, drop it in the bucket.



or just keep standing them in a pan, heat em red and tip em over, works well, cheap and simple.

Plus i know the thought of doing it that uncontrolled with drive you up the wall. Engineers are funny:D
 
H-4831,
That is why I anneal in the dark....Much easier to spot the colour change.
I understand the only reason to use water it to expedite the cooling process.

kombayotch,
"You can check whether or not you're annealing by checking the spring back of the brass. A Lee hand press with a sizing die and some gage pins are handy for doing this next to the annealer."

Please explain?
 
With nice new cases, or cases that have been freshly annealed, you choose a bushing that is usually 0.001" in dia. less than your desired sized case neck OD (varies a bit with caliber). With the amount of spring the brass is supposed to have, the neck pops back to about 0.001" larger in dia. than the bushing when it comes out. This is how you set the neck tension with bushing dies.

I don't test neck tension by measuring the OD. I do it by measuring the ID with gage pins. These are precision ground pins that are accurate to 0.0005" +/- 0.00002". You can specify whether you're getting a pin with a '+' tolerance, or one with a '-' tolerance (I like -ve). You use them like GO / NO-GO gages to determine the size of a hole. With new cases, or freshly annealed cases, the IDs usually end up all within 0.0005" of each other and when seating, the vast majority of runouts are nice and low (<0.001").

As you work harden the case necks (fire and re-size them), they start to resist cold working (re-sizing) more and more. You eventually have to go down in bushing sizes and squeeze them more in order to get the same neck tension. You start to see larger variation in neck IDs and higher runouts.

Annealing them makes them soft and more malleable once again. So, if you take the bushing size you were originally using and size an properly annealed case with it, it should only spring back about 0.001". If it still springs back more, say +0.002", the case hasn't been annealed. I want to get my brass to the proper point and not over. So, I use a Lee hand press to test this when setting up my annealing process (manual or automated).

I believe annealing is very beneficial because the results don't just show up on the target, they are very measurable in the cases themselves.
 
Your the second proponent for pin gauges where their usefulness has really sunk in. The last was discussing Lee collet dies.
 
Excellent information kombayotch.

Where is the best (and most affordable) place to get pin sets?
Do they normally come in 10thou increments?
 
any shop that supplies tools to machine shops will be able to supply you any size. Don't pay for more the "b" or shop grade, you don't need to have pins registered at lab tolerances. KBC tools out of toronto is good and fast ussually
 
great info and why I made up a annealing turntable. that way the time in flame can be controlled to a precise level. the amount of heat is indicated by templiac and is a good point of reference.

For me, as long as the 'conditions' are consistent, the end result has shown to be consistent enough and the results on paper have verified my results.

Perfect, not in your life but the functional ductility of centerfire cases is very broad (why we can shoot them so many times without annealing).

As long as the cases are returned to a common baseline, I feel that baseline is not that important. Unless you overheat and they get too soft.

I have over annealed cases by leaving them in a flame a couple of seconds too long (did not remove after the tempilac puffed). they will turn soft like taffy and easily bent with your fingernails.

so the type of alloy is just as important as the heating cycle.

I use the Lee collet die and I can feel the ease which they size. Crude but you can really tell a difference. Seating properly annealed brass also has a certain feel.

seems to work.

Jerry
 
You have thought through the process very carefully. I agree annealing of cartridge brass STARTS at 800 F. Below that some annealing occurs but it takes many minutes, not seconds. You don't have that time if annealing with the head of the cartridges in air, or you start to anneal the head. That is not good at all.

Before retirement I was involved in heating processes of critical and very expensive components. We used flame heating, and eventually induction heating. The biggest issue is the thermal conductivity of the component being heated. If it is poor, and some stainless is poor, then you can cover it with a layer of copper, and heat the copper, so the stainless in turn is heated uniformly. This is commonly done now with copper plates on the bottom of pots and pans.

Fortunately brass is very conductive. Gas, even in a propane flame is a poor conductor of heat. So I really don't think you have to worry about the high flame temperature causing hot spots in the brass that you can't see, as long as the case is rotating at a decent speed.

I've been practicing annealing with some picked up range brass prior to doing my 6BR Lapua stuff. I'm convinced that working in the near dark, and observing the red glow is the best method of temperature control. Using 800F tempilsticks and published literature I'm convinced brass does glow a dull red at 800F.

This said, I think most under anneal their brass. I've compared polished then annealed brass at 800F to new Lapua annealed brass for look. The Lapua stuff appears to have seen much higher temperature or long time than my few seconds at 800F.

I think one issue is that annealed is annealed. Trying to half anneal on a consistent basis is probably impossible. My thought is than an over annealed case is really one where the head gets annealed (i.e. up to 800F for a few seconds), and then you have a major problem. There is no way that it is going to take the 60,000 psi it is going to see on firing.

Just my thoughts. For sure you are on the right track.
 
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