Brass Annealing Temperature... Anyone?

[Djstorm100]

You aren't going by temperature solely. Turn the lights down and watch for the orange flame, when you see this flame that means the brass has gotten to hot.

 

[Tozguy]

Thanks for the video Dj. Very instructive wrt reading colors. When visual observation is all we have to go on the video is a good guide for that.

However, I would not be comfortable using so much heat as in the video. If exposure time is only 3.5 to 4 seconds then the brass only reaches annealing temperature for a split second. If such little exposure is enough to anneal it then it had to get critically close to over heating. When a half second of exposure to the flame makes such a difference control of time in flame has to be very precise.

Since annealing is a question of duration at temperature, a slower heating rate would suit me better. I would either turn the torches down or use just one torch. Things would happen more slowly and if given more time in the heat the brass would not have to get as hot. But that is just me.

 

[Eddyde]

I would consider induction heating if precise, repeatable control is needed.

 

[Tozguy]

Since brass cartridges are relatively expensive and designing an annealing machine is a rare occasion for most of us, I find it worthwhile doing some research. This is a quote from page 30 of one of the better publications that have come to light:
http://www.nationalbronze.com/pub-117---the-brasses_whole_web-pdf.pdf

''Annealing

When cold worked brass is progressively heated, the first effect, at about 250C, is for the internal stresses to be relieved. This prevents stress corrosion cracking subsequently occurring and also minimises the amount of distortion which may occur during machining. This low temperature heat treatment, which should be applied for 1⁄2 to 1 hour, is known as ‘stress-relief annealing’ and has little, if any, measurable effect on the mechanical properties of the material. The improved strength due to the cold working is therefore retained.

As the temperature is increased further, a rather more fundamental change occurs at about 400C and above and the material starts to ‘anneal’ or soften with time at temperature. The strengthening effect of the cold working is progressively lost, until at about 500C the alloy is in the fully annealed condition. Restoration of the cold worked properties can then only be achieved by further cold work. Due to the volatility of the zinc at the surface of the brass, it is not easy to anneal in a batch furnace with a ‘bright’ finish solely by the use of a controlled furnace atmosphere,''

Please note that temperatures are in Celcius. Page 30 is particularly relevant to us here but I recommend perusing all of the article. Also note that p.10 has some diagrams of lathe tool geometry for cutting brass. Hope you like it.

 

[HotChips]

DJ. Thanks for posting the video. I had found it before but failed to bookmark it. I have been trying to locate it again without any luck! I think that's the best video I've seen on annealing!

I agree with Tozguy about heating the brass more slowly if possible. I know that increases the chance of getting the base of the cartridge too hot. Right now I'm working on longer rifle brass so it shouldn't be a problem.

Tozguy. Thanks for posting the article from national bronze. I will definitely read it through.

Thanks again to everyone for sharing your knowledge and thought on brass annealing!

 

[Djstorm100]

Thanks for the video Dj. Very instructive wrt reading colors. When visual observation is all we have to go on the video is a good guide for that.

However, I would not be comfortable using so much heat as in the video. If exposure time is only 3.5 to 4 seconds then the brass only reaches annealing temperature for a split second. If such little exposure is enough to anneal it then it had to get critically close to over heating. When a half second of exposure to the flame makes such a difference control of time in flame has to be very precise.

Since annealing is a question of duration at temperature, a slower heating rate would suit me better. I would either turn the torches down or use just one torch. Things would happen more slowly and if given more time in the heat the brass would not have to get as hot. But that is just me.

When the cases that got a little red inside the neck are still good as they were pulled out immdenitally. All brass has different make up of materials so no brass is alike even ones that are in the same batch from the factory. If you don't feel confortable use only one flame if you had the Bench Source annealer I did. It's no big deal. Try some .223 or some brass that you have alot of.

I started out with a torch in a vice and socket/drill setup. Used a adjustable zip tie to hold the trigger on drill.

I reload for preicison rifle for PRS style matches, although I haven't shot any this year due to school. But my load at 1200 yards given the extreme spread I have is only a 0.1 mil different. My extreme spread is 12-15 SD is 4.4-5.6. You'll notice that when you seat the bullet you'll have alot more consistent feel back to back.

 

[grizzly10x22]

you can purchase heat sticks that melt at a given temperature. it is better to under anneal than over doing it. making the case mouth to soft sometimes will allow the case to collapse when seating the bullet. I bought a heat stick from enco and really cant say how well it works as I haven't gotten around to using it yet. using one of those heat guns dosent work as the case is too hot by the time you get a reading. grizzly10x22

 

[Tozguy]

On page 30 of the publication mentioned in post 13 there is a paragraph on stress relieving. This occurs at temperatures below annealing temperatures and seems to have some benefit for reloaders. This would be a reason to go easy on the annealing temperature because 'under' annealing still has benefits but over annealing destroys the brass for our purposes.

 

[Djstorm100]

On page 30 of the publication mentioned in post 13 there is a paragraph on stress relieving. This occurs at temperatures below annealing temperatures and seems to have some benefit for reloaders. This would be a reason to go easy on the annealing temperature because 'under' annealing still has benefits but over annealing destroys the brass for our purposes.

Adding to much oil is just as bad as not adding enough. Are you going to process one case every 30 minutes? You want and need the brass to relax and soft my friend. Get some range brass and clean it. Practice with it.

 

[Djstorm100]

Here's my setup.