6mmbr's annealing temperatures seem questionable...

I have thought of it. For it to work, you would need to jam the thermocouple tightly against the inside wall of the neck using something that would not act as a heat sink and perhaps "wet" it with a compound that would help to transfer the heat quickly.

You could not use an LCD display type instrument for reading the temperature values. These would need to be captured using a data logger. The kind of thing that records the values to a file that you open later. Any processing and displaying of the temperature in real-time adds way too much latency to the readings. We're looking for readings that are a few milliseconds apart. I had access to this type of equipment at the last place I worked, but not at this one, unfortunately. They also had a great Metrology lab that I miss for looking at stuff like this.
 
BattleRife, my cases look like the 450C you have in your pic. There is precious little colour change through the shoulder area of the case. I am glad that my observations agree with someone who can take more accurate temp readings.

When my cases look like the 550/600 cases, the necks are soft like taffy.

Tempilac is 'slow' as a temp indicator but it is consistent so as I said previously, I use it as a frame of reference and INFER the necks temp by a bit of trial and error.

I think the use of pins to determine the FORCE to move the neck ideal for reloaders to get a handle on how much/little annealing is being done. This makes a wonderful reference when setting up the annealer.

And the use of a mechanical annealer that will control the heat cycle is pretty much manditory if any degree of consistency is to be had. Time in flame is so critcial to our success as a very short period of time can push our temps beyond desired levels.

Colour change is a poor indicator - any of you try the same annealing with different brands of brass? I bet you will see different colour changes due to brand/alloy.

All of these tools and indicators will come in very handy when turning on that annealer next time. I reset the set up each time I use it due in large part to the inconsistencies of those torches. having flames that are repeatable would be a god send.

There is a some serious good tech in this post but for most accuracy minded reloaders, might be overkill. As long as the cases are annealed in a consistent and repeatable manner, they should be consistent neck tensions AND that is the goal for me.

Jerry
 
I think you could get a temperature map with a few different Tempilaq ratings and a thermocouple.

As various tempilaqs went off a reference reading could be taken with the thermocouple and a curve plotted so an actual temperature could be selected and reproduced. Repeated tests would confirm/debunk the accuracy of the curve.

I think the best bet would be to have the probe fitted in a machined insert to tightly match the neck.

All that said I think consistency will pay more dividends than perfected temperature.

Interesting thread!
 
mysticplayer said:
As long as the cases are annealed in a consistent and repeatable manner, they should be consistent neck tensions AND that is the goal for me.
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The key word here is "repeatable" for me. While I agree that if the cases are all annealed the same way in a given batch, they should all have the same neck tension and should all shoot the same way. However, if you've annealed to a different temperature than the previous session, the hardness will be different and that may change things like velocity, slightly. I want consistency from batch-to-batch as well because some of disciplines I shoot don't allow the luxury of sighter shots to zero out the differences.


The more I think about BR's salt bath method, the more I see its advantages. There are a few reasons why he probably chose potassium nitrate.

Unlike lead, it isn't toxic and impurities won't cause it to weld to the brass like solder. They used to use it for making beef jerky, some people still do. It's saltpeter.

According to Wikipedia: "It is also commonly used in the heat treatment of metals as a solvent in the post-wash. The oxidizing, water solubility and low cost make it an ideal short-term rust inhibitor."

If this dipping doesn't harm the brass (which is shouldn't), and the residue cleans off easily (which it should), he has every other method I've seen licked. The danger of overcooking the necks is completely removed and you won't anneal the body if the dip time is short. The annealing temperature is accurately known and completely repeatable, therefore, you will always get the same resulting hardness for a given batch of cases.

I'm seriously thinking of duplicating his setup and running my own experiments. I think it has a lot of merit.
 
A heated bath certainly has some very strong pluses but how would you handle the time in the pot?

Taking them in and out by hand creates an error.

Setting up a temp checking procedure each time I start up the annealer is really important. That is why I use the tempilac and will adjust the torches to get a similar result.

It is far from perfect but it has shown to be consistent enough that targets at 500m have not shown any problems with changes in group size.

I think neck ductility has a very wide useable range and as long as our brass falls within that range, consistent accuracy will result.

Look forward to seeing more testing and data.

This really is one of the last 'frontiers' of reloading. Except for "Xraying" our bullets, we have manipulated every facet of the reloading procedure to a very high level.

Controlling neck ductility for me is an area that needs to be understood and practised.

I really don't see huge gains in performance but if it stops that one flyer over the weekend, that is plenty good for me.

Jerry
 
mysticplayer said:
A heated bath certainly has some very strong pluses but how would you handle the time in the pot?

Taking them in and out by hand creates an error.

Setting up a temp checking procedure each time I start up the annealer is really important. That is why I use the tempilac and will adjust the torches to get a similar result.
Click to expand...

Nope, even doing it by hand, it will be far more accurate and repeatable that anything that can be done with a torch. The torch is much hotter that the temperature we are trying to hit, and we have to be precise in the soak time because there is a danger of overshooting the target temperature range and ruining the brass.

With a liquid that is at the temperature you are trying to hit, you can NEVER go over it. Any additional time beyond the time it takes for the brass to heat to that temperature and for the crystal structure to reform is only going to result in annealing further down the case body. But, you will always be annealing to the same temperature point, and thus, to the same hardness.

His method is in and of itself a better control that we will ever be able to achieve with a torch because his soak time is less critical that ours by orders of magnitude and we not only have to contend with the accuracy of the soak time, but with the accuracy of the torch's temperature as well.
 
That Wikipedia description makes it sound like the saltpeter has the same affect on the brass as stuff like Lemishine. Throwing the cases into to tumbler right after and running them in the SS media might actually result in nice and shiny cases.

No matter how clean I get the cases before annealing with the torch, there is always a film afterwards and I always end up burnishing the inside of the case necks with a brush with a bit of 0000 steel wool around it to keep bullet seating and bullet release silky smooth.
 
If brass cracks due to corrosion fatigue or stress corrosion cracking, I wonder if a salt bath would contribute to the corrosion aspect?
 
kombayotch said:
Nope, even doing it by hand, it will be far more accurate and repeatable that anything that can be done with a torch. The torch is much hotter that the temperature we are trying to hit, and we have to be precise in the soak time because there is a danger of overshooting the target temperature range and ruining the brass.

With a liquid that is at the temperature you are trying to hit, you can NEVER go over it. Any additional time beyond the time it takes for the brass to heat to that temperature and for the crystal structure to reform is only going to result in annealing further down the case body. But, you will always be annealing to the same temperature point, and thus, to the same hardness.

His method is in and of itself a better control that we will ever be able to achieve with a torch because his soak time is less critical that ours by orders of magnitude and we not only have to contend with the accuracy of the soak time, but with the accuracy of the torch's temperature as well.
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Yes, indeed it would be a much more stable temp product to use.

Any dangers with this material? flammability?

Sounds like a Lee lead cast pot would be the cat's meow.

Jerry
 
BattleRife said:
I don't have time to respond to (or even read all of) the comments here tonight, but I see there is some interest in some salt bath method. I uploaded a grainy-looking video shot under poor light of my current setup to show exactly how I do it.

http://s262.photobucket.com/albums/ii102/BattleRife/?action=view&current=Annealing_1.mp4
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Well, that told me everything I needed to know. That is a fantastic method and wins over the torch method by a country mile.

Have you found the time in pot to really matter that much. I see that you are pretty much going 2 to 3 seconds per case.

I love the idea of the lid with the holes. So simple and solves so many handling questions.

So what is the material you use and where can you find it?

Jerry
 
HOLY CRAP, I just came up with the idea a few days ago to use a salt bath to anneal brass. I look on the webernet and find out it has been done before.

We use saltbath heaters to heat up hydrocarbons in the processing of natural gas and liquids in gas plants. We only run the salt temp up to 320* C though.


What ever you do NEVER spill it on your self. The fluid retains it's heat so well the resulting burn will be very deep . One guy that works for a company that deals with molten salt once told me that a drop the size of a dime could burn a hole right through your hand. Don't know if that is true.
 
I am generally pleased with my setup, but I have not yet finished working out all the variables. I would like to do metallography on some of the cases that I photographed that were annealed at different temperatures. Once I had that as a baseline, I would next like to do some cases all at the ideal temperature, but soaked for say 1 second, 3s, 5s, 10s, 20s, 30s. My guess is that the structure will be little changed, but the annealed zone will extend further up the case and eventually get into the head.

Some info on the setup, with emphasis on the drawbacks so everyone is well informed:
- the heat shield is 2 layers of 304 stainless steel sheet, very thin stuff. The holes are drilled through both layers and a U-bracket is welded underneath that the cases stand on. Without the shield, I can't hold my hand over the bath long enough to anneal even a single case before it gets really uncomfortable.
- Once I began to explore the idea of using salts, supporting data was easy to come across. In particular, MIL-S-10699, a U.S. milspec published at least as far back as 1958, lists several compositions of salts for heat treating, including two potassium nitrate based baths for "annealing and stress relieving of cold worked copper and copper-based alloys". That made it a no-brainer. Shoulders of giants, and all that.
- The salt does stick to the cases, particularly at lower temperatures. If a guy didn't have a thermocouple, it would be fair to judge the bath temperature based on the point when the salt stops sticking.
- Sticking salt creates a couple of problems. 1- Where do you drop the hot case? That gob of molten salt will burn/melt/set fire to many things. 2- How do you get it off? 3- The salt level in the bath needs to be periodically replenished due to salt carried out on the cases. 4- Drips of salt collect on things, particularly the heat shield. In the video, towards the end you can see I am struggling getting the cases to seat all the way down in the shield, and have to twist them to get them out again. This is because salt build up on the rim of the holes is making them undersized.

My solution to Nos. 1 and 2 is to drop the cases into a bucket of water. The salt gobs cool immediately with a sharp, satisfying sizzle, and the salt eventually dissolves. The cases must now be rinsed thoroughly, or else you will find bits of crystallized salt here and there afterwards, particularly in primer pockets. And of course, you need to dry them. Speaking of which, definitely do deprime before annealing, to allow salt to rise into the neck and drain cleanly again, and to avoid salt becoming trapped in the front of the pocket.

- The MIL spec warns that the salts can become dangerously oxidizing at high temperatures (600C+). They also start to fume visibly at around 550C. This is with minimal sodium nitrate additions. Adding sodium nitrate lowers the point at which the salt melts, but also lowers the point at which it fumes.

-When I bought the salt, I got it at a Safeway pharmacy for something like $17 for a 2 kg bag. It has since been added to the federal government's list of controlled explosive precursors, and may not be available.

- I believe that long exposures of brass to molten salt probably does result in corrosion, and the MIL spec does have some mention of staining of cartridge cases, but I am not aware of any embrittlement or cracking issues, and exposure times of a few seconds are not going to cause any amount of general wastage.

I really like the controllability of the method, and the speed is good, approaching 1000 cases per hour without really trying. It has certainly been excellent for the experimentation. I must admit though, that given the setup, heat up and clean up times, not to mention the rinsing and drying of cases, I think it is best for those situations where I will be doing hundreds or thousands of cases in a sitting. I expect that once I have the ins and outs of annealing at home pinned down, I will work on a flame annealing method that does not require the soaking (and subsequent drying, which I hate) of the cases. Light the fire, anneal the cases, blow out the fire, done.
 
I'm a PhD student in chemistry so I've been following this thread with interest, even though I've never had the pleasure of taking a metallurgy course. We do a lot of synthesis in my lab, usually with silicone oil baths heated by IKA hotplate stirrers with thermocouple control. Silicone oil is only good to about 180 degC, however. Some of the people in my lab need 300-350 degC for nanoparticle synthesis, so they use heating mantles with a thermocouple-equipped controller. This works alright if you want to heat a round-bottom flask like we do, but isn't applicable to brass necks. We considered nitrate baths, but decided against it because of the oxidizer safety risk (being close to organic solvents and reagents).

Why not try a sand bath in the same setup? It won't transfer heat to the brass as quickly as the nitrate bath, and it might be an engineering problem to keep the sand level so that the necks are immersed to a reproducible depth, but the bath would be stable and inert, and I don't see how it would stick to the brass.
 
Ah, another option I forgot to mention is a dry aluminum heating bath. They are common in biological labs for heating samples to 37 degC. Essentially it's just a chunk of aluminum sitting in an enclosed heater, with holes drilled for a thermometer and plastic tubes that contain the sample.

It would require some fabrication, but imagine a block of aluminum sitting in an enclosed heater, with a small hole drilled for a thermocouple, and two shaped holes designed to cup the necks of a given caliber. Aluminum has a melting point of 660 degC, compared to the 400 degC required for annealing. (This aluminum mantle says 450 degC max temp. http://heatingqualitygoods.co.cc/) Some care would need to be taken to ensure the brass body isn't annealed by the hot air sure to surround the aluminum block. Additionally, I don't know whether this process would make the two metals want to stick together.
 
BR,

I think you have a good idea here with the salt bath. The control you are able to achieve, without the chance of overshoot is a huge advantage. Even with the CNC setup, there is no guarantee that I am getting the torches to the same temperature as the previous session. Even if I am, a different exposure time is required for each brand of cases or each caliber, and sometimes for different lots of the same brand and caliber, particularly if I have done things to them like turn the necks. It isn't a process that you can just turn on and use.

Each session requires a tuning and verification process, and each time I do it, I know that I am annealing to a different point. Although, that may not make much of a difference in practical terms. And, as I mentioned above, a bit of neck burnishing is still required due to the layer of oxide that you get after the cases pass through the flame. Many people ignore it, but there are noticeable advantages to removing it. So, I don't see a bit of post-processing as a huge drawback, especially if I can just throw the cases into the rotary tumbler with the SS media for 20 min. or so to remove any salt.

I think your issues can be addressed. Agent Mango may be going in the right direction tough. However, the idea of a solid block would not work because you are not going to get good thermal conductivity between the hole and the necks because you are not guaranteed good contact. However, fine aluminum powder may be an option. It would allow for better contact and heat transfer than a solid block. Other metals may work better though. The heavier and finer the metal powder is, the more it will behave like a liquid in terms of heat transfer.

Perhaps a metal (other than lead) with a low melting point can be used. Tin melts at 450F and pure tin should not adhere to the brass.
 
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BattleRife said:
I must admit though, that given the setup, heat up and clean up times, not to mention the rinsing and drying of cases, I think it is best for those situations where I will be doing hundreds or thousands of cases in a sitting.
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This is the justification for getting an annealing machine also. Even doing a batch of 300 manually is extremely tedious. It becomes very difficult to maintain the concentration and continue doing it consistently by the end. And many of us are processing thousands of cases.
 
kombayotch said:
I think your issues can be addressed. Agent Mango may be going in the right direction tough. However, the idea of a solid block would not work because you are not going to get good thermal conductivity between the hole and the necks because you are not guaranteed good contact. However, fine aluminum powder may be an option. It would allow for better contact and heat transfer than a solid block.
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Perhaps the solid aluminum idea could still work. I agree that there won't be full contact between the aluminum and brass, but I would expect the air very close (for instance 0.5 mm) from the aluminum surface would be close to the same temp as the aluminum block itself.

kombayotch said:
Other metals may work better though. The heavier and finer the metal powder is, the more it will behave like a liquid in terms of heat transfer.

Perhaps a metal (other than lead) with a low melting point can be used. Tin melts at 450F and pure tin should not adhere to the brass.
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I like the finely divided metal idea for heat transfer, but I worry about possible safety concerns. The more finely divided any reagent is, the more surface area to volume it has, and thus the more quickly it can react. For instance, the thermite reaction involves finely divided aluminum reacting with finely divided rust.

Mention of a tin bath reminds me of the Float Glass process, where glass sheets are made by floating on a molten tin bath. Wikipedia says this:

Tin is suitable for the float glass process because it has a high specific gravity, is cohesive, and immiscible into the molten glass. Tin, however, is highly[citation needed] reactive with oxygen and oxidises in a natural atmosphere to form Tin dioxide (SnO2). Known in the production process as dross, the tin dioxide adheres to the glass. To prevent oxidation, the tin bath is provided with a positive pressure protective atmosphere consisting of a mixture of nitrogen and hydrogen.
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So using Tin may be problematic. However, the float glass process is at 1100 degC, so the oxidization may be insubstantial at annealing temps of ca. 400 degC.
 
agent_mango said:
Why not try a sand bath in the same setup? It won't transfer heat to the brass as quickly as the nitrate bath, and it might be an engineering problem to keep the sand level so that the necks are immersed to a reproducible depth, but the bath would be stable and inert, and I don't see how it would stick to the brass.
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Hey, now there's an interesting idea. Particles of fine sand, in a container on a vibrating plate to produce a fluidized bed. Ideally, it would circulate sufficiently to homogenize the temperature. No sticking, no water quenching. Setup costs to get the heater/vibrator combination might be high, and heat up time might be on the long side, but after that, it could work like a charm.

I did look briefly at using metals other than lead for the bath, such as tin and bismuth, but decided that the salt was the way to go. It is long enough ago now (two years) that I forget what made me decide that all the metals were likely to have similar drawbacks, apart from the toxicity of lead, which, as a caster, I feel is badly exaggerated in most people's minds. I did try to dip a case or two into a bullet pot as I was casting, and noted that solder wetting the necks and tinning them was going to be an issue, and it may have put me off them entirely.
 
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