Annealing - Fast and Hot OR Slow and Warm

[NevadaZielmeister]

Gentlemen, a strange question. Do you prefer to get your case necks annealed with a very high flame (close, high PSI, etc.) for a short period of time (say 3 seconds) OR do you prefer to have a low flame for a longer period of time?

A friend of mine recently explained how the fast/hot method is better than the low/slow method. His reasoning was that you do not want to transfer a lot of heat down the cartridge wall towards the base. My contention was that the tempilaq was not indicating anything past 450 degrees Fahrenheit past half way down to the cartridge.

So what are your thoughts? I believe this might turn into a Giraud vs. Benchsource discussion, which is fine as well.

 

[BoydAllen]

Most annealing of cases, that I am aware of, is done with simple propane torches, so I do not understand the part about PSI, since they have no gauges. What annealing that I have done has been with a two torch machine with the flames near their highest setting and the inner flame about a half inch from the center of the case necks. It worked. With the correct amount of time dialed using a combination of templilaq and functional testing, sufficient neck tension was maintained for magazine feeding heavy magnum loads, and shoulder bump variation at a given die setting was minimized. IMO the options are greater than one extreme or the other, as long as case heads remain unsoftened.

 

[Dusty Stevens]

I hear the faster you get it done the better the molecules line back up.

 

[jlow]

It depends. Fast or slow has different meaning to different people.

For example, I use a BenchSource and I like mine to be done between 3-4 seconds which means I use 2 regular propane torches so get better/more even coverage. I like the 3-4 seconds because it is long enough so that slight differences in time would not cause any significant difference in the heating or more importantly the degree of annealing. At that duration, heat NEVER travels down significantly to the head as shown repeatedly with test using 400 degree Tempilaq. Of course, I have hear that some people like to do theirs with MAP gas which is much hotter and so result in significantly shorter time – that’s not for me.

 

[riflewoman]

There is a time at temperature element t annealing. So low and slow ends up being easier to control without overheating. YMMV

 

[NevadaZielmeister]

Most annealing of cases, that I am aware of, is done with simple propane torches, so I do not understand the part about PSI, since they have no gauges.

Boyd,

I have fitted my propane bottle with a regulator, allowing precise flame control. 9 PSI refers to pounds per square inch.

 

[NevadaZielmeister]

There is a time at temperature element t annealing. So low and slow ends up being easier to control without overheating. YMMV

This was my thought as well, that I can control the variables more when I have more time, but am just not sure if this is the best way or not. My results with 8 seconds at 9 PSI provided pretty decent accuracy.

Does anyone have any other experience?

 

[Brians356]

A friend of mine recently explained how the fast/hot method is better than the low/slow method. His reasoning was that you do not want to transfer a lot of heat down the cartridge wall towards the base. My contention was that the tempilaq was not indicating anything past 450 degrees Fahrenheit past half way down to the cartridge.

You are correct. Hotter simply means the heat will spread faster, but if you are monitoring the heat below the shoulder, it doesn't matter. I use a butane "kitchen torch" (ostensibly for making crème brûlée) and it takes a few seconds longer to anneal with than a propane torch, but I can still do a 6mm Rem case in under 15 seconds, a 223 Rem takes 11 seconds.

http://www.amazon.com/Master-Appliance-MT-76-Trigger-Soldering/dp/B000BHNYIW

 

[Scott Harris]

Annealing needs to be complete before the heat migrates to the base of the case and starts softening the base. I don't know what that maximum time limit is, but I'd guess anything over 8 seconds is getting into dangerous territory.

 

[jlow]

There is a time at temperature element t annealing. So low and slow ends up being easier to control without overheating. YMMV

This was my thought as well, that I can control the variables more when I have more time, but am just not sure if this is the best way or not. My results with 8 seconds at 9 PSI provided pretty decent accuracy.

Does anyone have any other experience?

With an automatic annealer like the BenchSource or Giraud, my own personal experience is the 4-5 seconds works perfectly well.

As with most things like this, what is best is to avoid the extremes i.e. too short or too long. We have already discussed the too short, but too long will indeed allow the heat to migrate down to the case head. Longer time also makes the work more of a chore as even with a Giraud, you will still have to keep an eye on it. If you are going to use an 8 second anneal, I would recommend that you test it out using the 400 degree Tempilaq before proceeding.

 

[jimcasey01]

For those using any form where metal (deep socket, pan or whatever) contacts the case near the head, that metal typically acts as a heat sink. As long as you monitor the temperature slightly below the shoulder down to the case head, and keep it below 400 degrees F, you should be fine. With a home built unit, I am running approx. 7.5 seconds, depending on the case. I actually slowed my unit down, checked for heat build up the length of the case, and had no problems until my dwell times exceeded 11 seconds. When I used a deep socket/drill unit, my times were typically 11-12 seconds, and because of the contact with the socket, the heat did not migrate to cause any concern. 400 degree and 700 or 750 degree Tempilaq I would think should be a part of any ones initial set up.

 

[Webster]

If the body below the shoulder gets to 500-600 F it's impossible to soften the brass at those temperatures. 700F should be stress relieving and not annealing. Annealing takes time at temp. I think it would be impossible to heat the neck area enough to soften the case head. Without hardness testing it's all guess work. I anneal with a single propane torch for about 8 seconds. I push the case into the very hot pointed area breaking it up into a wider cooler hot zone. I aim at the center of the neck moving the case back and forth about 1/8". The neck still has decent hardness so the shoulder and body cannot be annealed. I don't think annealing at 850F for 3 seconds would do any annealing. I have real data with hardness testing on case necks annealed in a lab quality temp controlled furnace. The bottom line is as long as you know you are not damaging the cases or making the neck area to soft keep doing it the same way. Do target results improve? I posted accurate annealing time vs temp charts on lapua cases several times on this website. If nothing else my data shows you cannot ruin cases if the necks are below any hint of red in a dark room and you don't see color traveling to far below the shoulder. Everyone is creating a different neck tension based on everything you do to a case. 2 thou neck tension does not relate to any actual amount of grip. It's a way of controlling grip. It means you are doing everything the same way and getting the same result. Annealing with Mapp gas seems scary. A very hot flame compared to propane. I like the idea of being above ~750F for a longer time. A red glow is about 1050F. Things happen very rapidly in that temp range.

 

[Webster]

You have point contact between a socket and the case. Not enough contact to get any reasonable heat transfer. People worry to much about getting the case heads to soft. I think the head would have to be above 800F for more than a minute to soften it.

 

[jlow]

Wow... Well in my books, anyone willing to put their face at risk (and only their own) to test something, can certainly do just about anything... ???

 

[Scott Harris]

You have point contact between a socket and the case. Not enough contact to get any reasonable heat transfer. People worry to much about getting the case heads to soft. I think the head would have to be above 800F for more than a minute to soften it.

That's wrong and flat out dangerous advice. At 800 degrees, brass is fully annealed in just a few seconds. Allow the base of the case to hit 800 for a few seconds and you're going to have problems.

http://www.6mmbr.com/annealing.html

 

[Brians356]

Several of us have repeated that we are stopping when the case about 3/8" below the shoulder gets to 450 or 475 degrees. So all this worry about softened heads is completely unwarranted. How long it takes to get there, whether 5 or 15 seconds, is irrelevant. But by using a locking case holder (Lee) clamped to the base, there is a definite heat sink effect anyway - FWIW.

 

[Webster]

You have point contact between a socket and the case. Not enough contact to get any reasonable heat transfer. People worry to much about getting the case heads to soft. I think the head would have to be above 800F for more than a minute to soften it.

That's wrong and flat out dangerous advice. At 800 degrees, brass is fully annealed in just a few seconds. Allow the base of the case to hit 800 for a few seconds and you're going to have problems.

http://www.6mmbr.com/annealing.html

Where do you get your info from. Attached for about the fifth time a graph showing temperature and time VS and hardness. I cut the necks off of once fired 6BR Lapua cases and heat treated them in a lab furnace that was accurate to about +/- 2F. I used a furnace because it's the only way you know the actual temperature of the sample. The necks where attached to a fine NiChrome wire and lowered into the furnace thru a 1/2" hole to eliminate temp loss from opening the door. After heat treating hardness was determined with a lab quality hardness tester. I didn't anneal at shorter times because I didn't know how long it would take the sample to reach temperature. Too many people making up facts! Looks like 15 seconds at 800F you only drop about 3 hardness units. Note the data is 15 seconds and 5 minutes.

 

[BoydAllen]

Interesting data. Lacking your equipment, when we set up my friend's two torch rotary case annealer, it was cut and try with three different temperatures of Tempilaq, applied on the case body, from head to shoulder. We soon learned that all we needed was the 500 degree, and its burn level, was approximately the same as where the color shows up on the annealed case. We instigated the program to deal with variation in shoulder bump of 7mm WSM and .339 Lapua brass. We wanted to retain as much of the original neck tension as possible, while at the same time uniforming shoulder bump. For the first small batch, we were a little conservative on time, which we increased slightly, perhaps a second, at which point our shoulder bumps became very uniform, and the necks were not too soft for use in the field, out of a magazine. The trouble with lab data is that unless you have the same equipment as was used to produce it, using it may be difficult. We generally have one or more simple propane torches, and the necks stay on the cases. My takeaway from your data was that even after the neck reaches a particular temperature, the dwell time at that temperature is a significant factor, evidently, the change is not instantaneous. This takes me back to the days when some people annealed necks by dipping them in molten lead. Like your furnace, the lead pot would be at a known and controllable temperature.

 

[Mozella]

Here http://www.nlrc.org/index_htm_files/Ryan%20Stevenson%20-%20Dissertation.pdf is a very interesting scientific study about cartridge brass. It's long and most people will not take the time to read it (even though serious reloaders should).

They used the hand held Drill-And-Torch method of annealing because that is what many reloaders use. The experimenters calibrated their procedure time using Tempilaq and then attempted to duplicate the same procedure for each case. This proved not to be a good approach. They concluded that: "The annealing process is not able to apply consistent amounts of heat to each cartridge that is annealed. ............cartridge brass (30% Zn) is usually well within the face centered cubic α phase of brass. Thus, the rate of cooling after the annealing process should not greatly affect the microstructure of the material as long as the cooling process can be kept consistent for all of the annealed cartridges. The variability in annealing results is therefore most likely caused by an inability to accurately control the temperature and time of the heat treatment process........"

They determined that (when examined under a microscope) the post-annealing grain structure of the sectioned cartridge necks varied from one side of the neck to the other. They went on to say: "The microstructure variability after annealing will have consequences for shooting accuracy as one round may react differently to another. Large variations in microstructure, with circumferential position, in a single cartridge may affect the way in which a bullet leaves the cartridge during firing and thus further affect shooting accuracy. ............................... the results suggest that an improvement in the neck annealing process could greatly increase the ability to control the material properties of the cartridge cases. A more controllable annealing process would decrease the variability of the annealing results achieved and could help to maintain accuracy when shooting."

They determined that it might be better not to anneal at all rather than use a less-than-optimum procedure, such as the drill-torch method.

After further discussion about neck hardness in cartridges fired and reloaded several times without annealing, the conclusion was: "This suggests that if annealing is to be carried out it should be done on a regular basis."
They made some careful measurements of hardness at a number of points along the length of the case and plotted that information for factory brass, fired brass, and fired brass, which was subsequently annealed. In short, they proved what most of already believe; i.e. necks get harder the more they are fired and reloaded. Necks can be returned to near-factory condition after DIY annealing. Down around the base, hardness remain pretty much the same and proper annealing does not dangerously soften the base. Resizing causes thinning of the cartridge just above the base. Improper neck turning can cause a notch and/or burr at the top of the shoulder and should be avoided. No real surprises here, but it is nice to have scientific confirmation.
The experiments relating to actual seating force and extraction force was flawed and the failed to produce useful information and that is a real shame in my opinion.

After reading the entire study, I confirmed my belief that a good annealing machine, such as my DIY "Skip Design" unit, carefully calibrated using Tempilaq, is better than using a hand held torch and "counting" the annealing time. I have confidence that my annealing machine is not damaging my cartridge bases and that the condition of my brass, which I anneal each time, is returned to near-factory condition, which is helping to make my neck tension more consistent.

 

[1066]

Using a single torch with a .308 case I typically run at about 7 seconds in my machine. I can pick up the cases by the head as they drop off.