Annealing temperature and time.

[Cadtek]

For those of you who anneal your cases. What do you guys think of this brochure on case brass. As far as I understand, we can add 10°C when we halve the time, and subtract 10°C when we double the time. If we halve the time seven times (2 min. 1min. 30sec. 15secs. 7.5secs. 3.75secs. 1.875secs. 0.9375secs) we must add 70°C. If we look at the yellow line (which is the hardness we get after one firing 140 to 150 Hv), we see it cross 100HV. (desired hardness 90 to 110Hv) at 450°C. When we add 70°C we are at 520°C (968°F). AMP says 750°F is far too low and shows a graph on its sides showing a temp. above 1000°F. Maybe the time over the annealing temp. is shorter than 1sec., so we have to halve the time several more times.

 

[watercam]

For me it is easier to paint the inside of a neck with 750º Tempilac, heat until it melts and count the seconds it takes for that to happen. Then run all your brass at that time frame. As far as the AMP, good luck.

 

[RegionRat]

Are those plots for 1/4" pucks, or for 0.015" thick similar to necks?

 

[jimcasey01]

A few years ago I built a "Skip's Annealer". Using a regulated propane tank and Tempilac, I got very close to what I now achieve with the AMP annealer. I was very slightly over annealing near the end (as best as I can tell), as I achieved more consistent results by doing so, I thought. Consistency is what is important.

 

[Ned Ludd]

As RegionRat noted, what form of brass was tested to create the data in your brochure? If you don't know, the chances are good it wasn't that similar to a piece of cartridge brass in terms of its physical properties. The exact composition of the alloy, as well as its physical characteristics will have an impact on annealing, particularly on the minimum amount of time required at a given temperature to successfully anneal it. If you're interested in using an induction annealer, AMP probably has probably published the most data regarding annealing actual brass cases. I'd start at the following link for that, if you haven't already read their articles.

https://www.ampannealing.com/articles/

If you're interested in using a torch-based system, I can tell you that I have annealed tens of thousands of cases, maybe more, over a period of years. I use a Giraud annealing machine and have always set it such that the neck starts to glow a very dull red as visualized in a darkened room. Based on physical characteristics (incandescence) of heated materials, this is probably a temperature of around 750 to 850 degrees F. Years ago when I first started annealing, I tried the Tempilaq approach and found it to be a complete gong show in my hands. So I adopted the "dull red in a darkened room" approach and have used it ever since. I have been very satisfied with the results.

My main point here is that I wouldn't go out of my way to make annealing any more difficult than it already is. People have used a torch in combination with the "dull red in a darkened room" approach for many decades before induction annealers came along. For the most part, they probably never worried about the exact hardness or crystal structure of their brass, but [amazingly] it worked just fine anyway. If you wish to find more information about annealing brass, try searching the internet for articles about annealing brass that were generated by the military; they know a little bit about it. Also, I have come across a couple Material Science-type student dissertations that contained a lot of interesting and useful information about annealing brass. The only problem is that those articles require a bit more effort (Google-fu) to find. If I still had the links, I'd pass them on to you, but unfortunately I don't.

 

[KY_Windage]

My main point here is that I wouldn't go out of my way to make annealing any more difficult than it already is. People have used a torch in combination with the "dull red in a darkened room" approach for many decades before induction annealers came along.

Yup, drill with a socket and a propane torch -- seems to work fine to me, and it is cheap and fast.

 

[Cadtek]

I've read a lot about annealing brass, and one of the things that has been called for is a graph with shorter annealing time than half an hour. So I thought maybe this one with 2 minute annealing had some interest to someone. It also allows us to read the temperature by adding or subtracting degrees by halving or doubling the time. If we double the time four times up to 32 minutes we see where 750 ° F comes from.

 

[jepp2]

My experience is if you follow the advice of @Ned Ludd you will not go wrong.

 

[watercam]

I agree with Ned Ludd. Some brass is more consistent then others and I keep the lights low these days to watch for the 'glow'. The timing method is a good base to watch for but once in a while one finds a a piece that heats more or less quickly than the rest.

 

[Cadtek]

My experience is if you follow the advice of @Ned Ludd you will not go wrong.

I agree with that. Dull red in a darkened room is probably the right temperature and this graph also tells us he's right.

 

[Ned Ludd]

I've read a lot about annealing brass, and one of the things that has been called for is a graph with shorter annealing time than half an hour. So I thought maybe this one with 2 minute annealing had some interest to someone. It also allows us to read the temperature by adding or subtracting degrees by halving or doubling the time. If we double the time four times up to 32 minutes we see where 750 ° F comes from.

If you look through enough articles with annealing curves over time at a given temperature, what you will see is that you can actually effectively anneal brass even at a lower temperature than we typically use, but it takes a very long time. As you observed, when the temperature is increased, the amount of time required for effective annealing decreases. Once a certain annealing temperature has been reached, the response is very steep, as shown in the last graph of "hardness versus time" in the file you attached to the original post. This creates the issue of having a very large change in hardness (Y-value) over a very small change in time (x-axis). For that reason, making estimates of of the type, "If I increase the temperature by "X" amount, I can cut the annealing time in half" are more difficult because even a few seconds difference in either can have a big effect on the very steep hardness response.

Nonetheless, if you have such a graph prepared specifically with an induction annealer (which AMP probably does, but I haven't looked in a while), you should be able make fairly good estimates with respect to annealing time at a given temperature in the manner you described. The reason I point this out is because as was mentioned previously, we don't know for sure whether the data in the file you attached was for a [relatively] thick piece of brass, as compared to the thin neck/shoulder area we anneal on a piece of cartridge brass. It makes a difference. Because the hardness versus time curve is so steep in the region we typically want to use, you may have to be pretty quick working the cases in/out of the machine. If the calculated annealing time was pretty short and I had to make a judgement call, I'd probably be tempted to be conservative with the time so that no cases would come out under-annealed. I doubt at the temperatures we typically try to use that a few seconds extra would damage the brass.

 

[Webster]

For those of you who anneal your cases. What do you guys think of this brochure on case brass. As far as I understand, we can add 10°C when we halve the time, and subtract 10°C when we double the time. If we halve the time seven times (2 min. 1min. 30sec. 15secs. 7.5secs. 3.75secs. 1.875secs. 0.9375secs) we must add 70°C. If we look at the yellow line (which is the hardness we get after one firing 140 to 150 Hv), we see it cross 100HV. (desired hardness 90 to 110Hv) at 450°C. When we add 70°C we are at 520°C (968°F). AMP says 750°F is far too low and shows a graph on its sides showing a temp. above 1000°F. Maybe the time over the annealing temp. is shorter than 1sec., so we have to halve the time several more times.

All the data is annealing over one minute. The charts have no value for flash annealing.

 

[TC260]

https://www.ideals.illinois.edu/bit...9/engineeringexperv00000i00359.pdf?sequence=3

A wealth of information...

 

[TC260]

...and a description of flash annealing

https://www.sugawara-labs.co.jp/en/application_xenonflashes/semiconductor_annealing_heat_treatment

 

[Cadtek]

But a map with 1 hour annealing has value? This is probably why 750°F has been recognized as correct.

 

[rwj]

Here’s another good source of information. The 3D charts on page 23 illustrate that the change in hardness is a factor of time, temperature, and the % cold work present in the material.

https://www.academia.edu/21283133/Recrystallization_Behavior_of_70_30_Brass

Personal experience will dictate how often each of us anneals, but until the cold work present reaches 25%, very little change in hardness will be realized. FWIW, I anneal after 4 firing cycles.

Regarding temperature, little hardness change is realized at temperatures below 425 degrees C (~750 degrees F). Rapid change occurs when temperature nears 550 degrees C (~1000 degrees F). This is fortunate in that the necks can be quickly raised to an effective annealing temperature, this limiting the temperature of the case body which should not be annealed!

It should also be noted that the graph on page 15 for 550 degrees C indicates that the test coupons were subjected to this temperature for ~5 minutes to achieve the maximum hardness reduction. As the coupons measured 1” X 6” X .125 inches thick (see Section III on page 5), this time is likely that required for this mass to soak thru. A much shorter time would be needed for a ~.015” thick short length case neck. How much shorter is unknown, but the studies performed by AMP suggest it can measured in seconds.

The key to consistent hardness reduction/control is a consistent process. I’m a flame annealer and achieve an outcome that is acceptable to me. However, I do believe that case hardness variation within a lot would be less if they were annealed via a timer controlled induction machine. Whether less hardness variation would yield smaller groups and/or improved scores is certainly a debatable topic!