ANNEALING

[Webster]

I hate to mention annealing ssince it starts a pissing match and 100 opinions. However the below website give good info on how hardness changes with various times and temperature. I will not comment on the data. Make what you want of the article.

https://vacaero.com/information-res...rmation-and-annealing-of-cartridge-brass.html

 

[jthor]

Great article thanks for sharing!! Also... AMP is doing 10% off now for the next 3 days.

 

[muleman69]

I hate to mention annealing ssince it starts a pissing match and 100 opinions. However the below website give good info on how hardness changes with various times and temperature. I will not comment on the data. Make what you want of the article.

https://vacaero.com/information-res...rmation-and-annealing-of-cartridge-brass.html

Great read

 

[riflewoman]

I wonder if he could be convinced to do some metallography on brass that has been “annealed” using the various techniques we’ve discussed?

 

[Bob L.]

I wonder if he could be convinced to do some metallography on brass that has been “annealed” using the various techniques we’ve discussed?

This would provide real value. All the literature I have been able to find uses samples that are considerably thicker than case necks/shoulders and/or heat for a much longer time. Our situation of heating at shorter times and higher temperatures (flash annealing) appears to not be researched except by AMP. Kudos to AMP for their work, but it would be nice to see research using the more traditional methods of case annealing.

 

[Webster]

This would provide real value. All the literature I have been able to find uses samples that are considerably thicker than case necks/shoulders and/or heat for a much longer time. Our situation of heating at shorter times and higher temperatures (flash annealing) appears to not be researched except by AMP. Kudos to AMP for their work, but it would be nice to see research using the more traditional methods of case annealing.

Without reviewing it's my take is that if recrystalizing isn't taking place at longer times than we anneal less is happening at 3-10 seconds. I think it's chart 9 that shows hardness after time and temp. Also the more you cold work brass the more energy is stored in it and recrystalizatin occurs at slightly lower temp for a given time. After looking at the data it looks like case necks probably have a cold work of about 15%. Amps gives hardness data on their website to show whats going on. Bottom line is that since we are flash annealing, not at temp for long times, we are stuck with the methods we use. The only question is whats the difference between flash annealing with a torch around 750F and annealing at a higher temp by induction. I put microhardness data on this website at least 4 times showing annealing on case necks at various temps at 15 seconds and 5 minutes. I see nothing wrong with a torch or an induction annealer. Neither method keeps the neck at temp more than a fraction of a second. The torch at 750F and an induuction annealer at 1100F shouldn't be at temp more that a few tenths of a seconds. Recrytallization takes time. Induction annealer may get you a few hardness units lower than a torch but they both accomplish stress relief and a slight reduction in hardness. As long as your method produces consistant repeatitive results don't worry about the metallurgy. Just keep annealing.

 

[dcali]

Interesting, but be careful - the times used are very different than the ones we use, which means the temperatures will be too.

 

[riflewoman]

Interesting, but be careful - the times used are very different than the ones we use, which means the temperatures will be too.

The temperatures reported in the document were most likely in a calibrated lab furnace. So pretty accurate.

 

[Webster]

Interesting, but be careful - the times used are very different than the ones we use, which means the temperatures will be too.

If not much happens at long times less happens at shorter times.

 

[dcali]

The temperatures reported in the document were most likely in a calibrated lab furnace. So pretty accurate.

I mean that if you're looking at 30 minute temperatures, 5 second temperatures aren't going to be the same.

 

[ToddKS]

As much as I enjoy a good annealing thread, it would be great if someone could get a Bench Source or Giraud torch annealer and do some lab testing using the times we typically run the brass through for. That would be relevant to my interests.

No criticism of this particular study, but 30 min dwell times are not the data points I am personally interested in.

 

[rammac]

"...don't worry about the metallurgy. Just keep annealing"

???

That's what I like, if it doesn't work then just keep doing it.

According to the Machinery's Handbook (the machinist's bible on metals)

"Annealing: A term denoting a treatment, consisting of heating to and holding at a suitable temperature followed by cooling at a suitable rate, used primarily to soften but also to simultaneously produce desired changes in other properties or in microstructure."

"When the term is used without qualification, full annealing is implied."

"When applied only for the relief of stress, the process is properly called stress relieving."

"Stress Relieving: A process to reduce internal residual stresses in a metal object by heating the object to a suitable temperature and holding for a proper time at that temperature. This treatment may be applied to relieve stresses induced by casting, quenching, normalizing, machining, cold working, or welding."


If what we do is actually stress relieving the metal rather than annealing then why call it annealing? And don't tell me that we are annealing to a half-hard condition, that's not what several reports show. According to several reports that I've read we don't use a high enough temperature or enough time to actually anneal the metal to any degree so let's quit calling it that and use a term that describes what we are actually accomplishing - stress relieving.

 

[Straightshooter1]

Seems to me that whatever the results of the process we do (e.g.. stress relieving), the term "annealing", as we typically use it, is a reference to the process rather than the result(s). Huh???

But it does help to understand just what we're actually doing. Otherwise, it's something hard to control to get the desired end results.

 

[rammac]

That's the problem, by definition the process we use isn't annealing, it's stress relieving. We may have come to using the word "annealing" incorrectly by abusing it for decades but the word doesn't describe the process any more than it describes what we accomplish.

 

[ToddKS]

At a generic level this is my understanding of these two processes.

Stress relieving is a process where the metal in heated to relieve stress in the material. The goal of stress relieving is not to change the hardness, it is to remove stress that can cause dimensional issues down stream in the manufacturing process or when the part is in use.

Annealing is heating a material with the objective of softening the material. The intent is specifically to soften the material and make it more workable.

Different temperatures and times are involved in the two processes for a given material.

Our goal is to soften the material and make it more workable, therefore we are attempting to anneal. What the end result is from that attempt is certainly debatable.

 

[dcali]

What we do is annealing. We're using the right terminology.

 

[Ned Ludd]

The keys to this article is that much longer times than we typically use are necessary to have any effect at lower annealing temperatures (i.e. ~700-800 degrees). The time necessary to anneal also appears to decrease as temperature increases.

However, the real question is whether any of the approaches we typically use are sufficient to properly anneal the brass at all (i.e. torch annealers, induction annealers, etc.). None of the annealer manufacturer's recommended annealing temps/times are likely coming anywhere close to the effect of 1000+ degrees for 30 minutes that seems to be both required and sufficient to anneal the brass. I think it would be important to know as the temperature reaches the 1200-1300 degree mark, how much shorter does the time required to anneal the brass become? If it still takes 20 to 30 minutes per case at much higher temperatures, I can imagine I might finish annealing my next 400 piece brass prep in time to shoot a match during the 2047 season.

 

[SGK]

Got to love this. We can't even agree on the goal let alone conduct proper analysis as to whether a particular technique achieves this goal. It's a crap shoot. Perhaps we need a little crowdfunding round to pay for some proper research/consultation. There's likely enough people just here on this forum annealing, or thinking they're annealing, to toss in a fiver each for some proper answers.

 

[dcali]

The keys to this article is that much longer times than we typically use are necessary to have any effect at lower annealing temperatures (i.e. ~700-800 degrees). The time necessary to anneal also appears to decrease as temperature increases.

However, the real question is whether any of the approaches we typically use are sufficient to properly anneal the brass at all (i.e. torch annealers, induction annealers, etc.). None of the annealer manufacturer's recommended annealing temps/times are likely coming anywhere close to the effect of 1000+ degrees for 30 minutes that seems to be both required and sufficient to anneal the brass. I think it would be important to know as the temperature reaches the 1200-1300 degree mark, how much shorter does the time required to anneal the brass become? If it still takes 20 to 30 minutes per case at much higher temperatures, I can imagine I might finish annealing my next 400 piece brass prep in time to shoot a match during the 2047 season.

It's hard to do. Most annealing data out there is for very large samples heated for very long times (compared to shooting flame over a case neck for a few seconds). The temperatures we require are significantly higher, but the heat transfer happens much faster - the ratio of surface area to thermal mass is much higher. In either case, it's hard to measure. The only pragmatic way is hardness testing like that done by AMP. I'm still waiting for someone to tell me what the appropriate annealed state of a piece of brass should be, which seems like a prerequisite for figuring out *how* to anneal. We've collectively skipped that step.

 

[rwj]

It's hard to do. Most annealing data out there is for very large samples heated for very long times (compared to shooting flame over a case neck for a few seconds). The temperatures we require are significantly higher, but the heat transfer happens much faster - the ratio of surface area to thermal mass is much higher. In either case, it's hard to measure. The only pragmatic way is hardness testing like that done by AMP. I'm still waiting for someone to tell me what the appropriate annealed state of a piece of brass should be, which seems like a prerequisite for figuring out *how* to anneal. We've collectively skipped that step.

If any case manufacturing engineers/metallurgists are following these annealing threads, they are no doubt laughing! They obviously understand their final anneal process and its effect. However, there is no reason for them to share the information with their customers and/or competitors!