Salt Bath Annealing - AMP Study

[MikeMcCasland]

This article ought to cause some 'spirited' discussion.

https://www.ampannealing.com/articl...XMkCVKo04DVa1v4fJrLea6NmB0kvfUJu6Mb6R4qmitieA

"In the course of this study we tested a variety of cases, used multiple temperatures, and multiple times of insertion into molten salt. Not once did we observe correct annealing results. In particular, the necks, which are the most important section of the case for annealing, simply refused to anneal soft enough. If they did start to anneal with a long dwell time, the shoulder and body over-annealed. We do not believe that any combination of temperature and time can overcome this fundamental flaw.

What is the point of taking on all that risk, when the results are so poor? There are several ways to achieve correct annealing. Molten salt bath "annealing” isn’t one of them. For those reloaders considering getting started on annealing, and who are on a budget, we would recommend a gas flame-based option."

 

[Willie]

Oh yeah! I've had a lot of people tell me I'm crazy for spending money on the AMP & accessories, when I could get better results, for the cheaper salt bath system. I never tried it, cause I'm ugly enough and knew I would, sooner or later, anneal myself.

I figure most of the people using the salt bath method will continue to use it, especially if they are having reasonable results, or scream "fake news" at Alex.

 

[riflewoman]

Of course they’d find fault with a competitor...

And their statement that annealing can only be determined by hardness isn’t the whole story. The only true method of determining annealing is to look at the microstructure and compare it to annealed, and various levels of “hard” brass structure HAVING THE SAME TYPE of cold work applied. For cold worked rifle brass it isn’t easy to duplicate other than running a thin walled tube in a die and over a mandrel a number of times. (Hmmmm?) But hardness is at least an indicator.

 

[Webster]

Each box represents data for a particular starting deformation. Data from the University of ILL. P



21% starting deformation chart. We don't know the % deformation on a case neck. 21% may be high. Even at 700C the gs doesn't start increasing until some where after 30 sec at temp.




Above my data annealing necks only in a furnace. 9 years ago I don't remember seeing any grain size change on any of the samples. No GS change matches the University of ILL data. No GS change until much longer times. The chart is micro hardness converted to HRB scale. The chart show very little hardness drop for 15 seconds at 900F. The factories anneal wiith a torch.

Amps implies that a salt bath won't work. I believe the number they state. Why does a torch work? Question without an answer: Is stress relieving all that is needed? I know I am annealing to some degree with a torch because if I increase the time from 5 sec to a beginning of red glow (abt 1050F abt 10 sec.) I can sqeeze the necks oval shaped easily with little force with pliers. I know that 5 sec with a torch prevents split necks.

Bottom line why would an induction annealer work at temperatures and times that a salt bath or torch won't work? Is the induction annealing method closer to 1000-1100F?

Of course they’d find fault with a competitor...

And their statement that annealing can only be determined by hardness isn’t the whole story. The only true method of determining annealing is to look at the microstructure and compare it to annealed, and various levels of “hard” brass structure HAVING THE SAME TYPE of cold work applied. For cold worked rifle brass it isn’t easy to duplicate other than running a thin walled tube in a die and over a mandrel a number of times. (Hmmmm?) But hardness is at least an indicator.

 

[BoydAllen]

I believe that one has to judge the effectiveness of a process by actual performance. In the case of case annealing, that would mean how the cases that were done a particular way actually performed. We can hypothesize a correlation between lab measurements and performance, but to my mind the actual performance is the preferable standard. Some years ago I helped a friend pick out a two torch annealer and set it up. We used Tempilaq and did actual performance testing to evaluate our results. In our case we wanted more uniform shoulder bumping, with necks that were hard enough for hunting, feeding out of a magazine. We were able to produce exactly the results that we wanted. That is all that mattered. If I was evaluating any other process, I would state the performance goal and test for how that goal was met.

 

[Grimstod]

I remember When Hoyt came out with the can and a half system. Mathews produced a video attempting to show that it did not work. The video was total fake news by the way. Now Mathews uses the can and a half system themselves. I am glad that one worked out for the customers. As for this article. I am skeptical. Many numbers do not add up. I do have some brass annealed by electrolysis and will be sure to do my own test against the salt bath soon.

 

[David101]

I think it is more about the thermal conductivity of the Salt bath. Just like a person can walk on a bed of hot coals. The reason being the coals to not conduct heat very well from just surface touching. If they were going to have a go at any competitors the would go another method. Salt bath annealing is pretty down there on the uptake.

 

[Shinbone]

Due to the extreme conflict of interest, it seems inappropriate to me to personally conduct and then publish a detailed study squarely aimed at torpedoing one of your competitors.

JMHO

 

[MikeMcCasland]

I doubt they're trying to eliminate competition, when in the article they're telling you that if you want to anneal on a budget, a propane annealer is the way to go.

 

[Ccrider]

Due to the extreme conflict of interest, it seems inappropriate to me to personally conduct and then publish a detailed study squarely aimed at torpedoing one of your competitors.

JMHO

I think it’s called marketing. The American way. I see nothing wrong with it.

 

[Texas10]

I can only say that if all "research" were conducted in the way of that article, I would not be writing this on a my laptop computer, but rather charcoal on a cave wall.

 

[Pawnee Bill]

Give up my AMP annealer, hell no!!!

 

[mikecr]

Full annealing with a torch or induction works of course.
But all I do normally is a bit of stress relieving(which I refer to as 'process annealing'), and would only full anneal(with a torch) prior to reforming to a new cartridge.

If you look close at the prior posted red/blue lined hardness chart, it's easy to see that a ~10sec DIP at ~850-900deg puts your necks in a very flat region of resulting hardness. This region can provide easy & consistent results for most of us.
The only way to get back to flat further on is to go full anneal, hotter, longer.. That's not what we normally do or need.

I've been dip annealing for over 40yrs & always happy with the results. I'm not attempting to save or kill a business in saying so. It's just the way it is.

 

[ballisticdaddy]

I have been annealing with a torch powered unit from a very respectable manufacturer and have had good results. A friend of mine purchased an AMP Mark I and after doing some side by side comparison I was surprised how much more consistent the induction annealing was over the propane powered unit. I even had to change my die settings and neck bushings as the brass was noticeably softer than what I had been used to. My guess is the temperature is quite a bit higher and faster with the AMP unit versus my propane unit utilizing 750 degree tempilaq. Bottom line is if you are happy with the results you are currently getting then continue to do so but without doing a side by side comparison it is very difficult to say all annealing is the same.

 

[Webster]

I can only say that if all "research" were conducted in the way of that article, I would not be writing this on a my laptop computer, but rather charcoal on a cave wall.

The only way AMPS could get their accurate numbers is if induction annealing allows precise control of time and temperature thus allowing annealing at a very high temperature. It's obvious they are getting the necks softer than we can get safely with a torch. I'll stick with a torch. It cost me zero. A small tank of propane once a year.

 

[Rick300]

I am certainly no engineer, but salt bath annealing has greatly improved consistency when resizing. Is it as good as an AMP? Probably not. Is it good enough for the masses? Probably.

 

[TAJ45]

Justa FWIW: When I toured the Sierra plant in Sedalia, MO abt a year before they stopped giving tours, I was shown a sheet of copper making it's way through a "furnace/heating apparatus". He told me the temp which I maybe remember being in the 500° range....I think.
This seemed low from what I had read but not knowing the diff needed per application or the length of time involved at their temp, I just nodded and said "hmmm". ;-)
For once i had the presence of mind not to mention that "They were doing it all wrong".... ;-)

 

[riflewoman]

Different metal. Gilding metal is 95-5 (Cu-Zn) so the heat treatment is different.

 

[David101]

Im not promoting AMP in fact I made my own induction machine. With regards to
" if induction annealing allows precise control of time and temperature thus allowing annealing at a very high temperature."
Well most of the home made units are using timers that have a 0.01 second resolution so accurate and consistent timing is not a problem. They also have a very consistent power supply so being able to reach a certain temperature for a given time repeatability is very good.
As to what the factories do I know that ADI induction anneal a friend in the Rifle club used to work there in quality control. It was done on a production line imagine all the cases upright all next to each other traveling on some sort of belt. They just passed by a induction element.
Do they the factories and AMP reach higher temperatures I dont know at this point I have a friend with a amp so perhaps some tests with tempilaq will reveal that secret. At the moment I use 750 tempilaq and set the time to make a change in that but in a dark room show no sign of any heating. It will most often show a sign on the cases but not always despite having reached the 750 mark.

 

[Murray Brook]

I remember When Hoyt came out with the can and a half system. Mathews produced a video attempting to show that it did not work. The video was total fake news by the way. Now Mathews uses the can and a half system themselves. I am glad that one worked out for the customers. As for this article. I am skeptical. Many numbers do not add up. I do have some brass annealed by electrolysis and will be sure to do my own test against the salt bath soon.

Please let us know your results. TKS