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.
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.
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 <span style="text-decoration: underline">measuring</span> the spring back in the necks before and after, rather than just taking the info at face value or going by color alone.
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. 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.
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.
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 <span style="text-decoration: underline">measuring</span> the spring back in the necks before and after, rather than just taking the info at face value or going by color alone.
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. 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.
