Salt Bath Annealing - AMP Study
- Thread starter MikeMcCasland
- Start date
I believe that Salt Bath Annealing is cutting into Amp's market share. Just that simple. Many people are having great results with SBA for a very reasonable price. AMP needs to realize, at their price point, the market is really quite small for people with that much disposable income. 1850.00 will buy a lot of brass. Just my .02. 
Paul
Paul
There is a lot of money being spent on all of the components in Guns and the reloading bench. A set of electronic scales $1000 with powder thrower and trickler add another $600. Scopes for Competition probably min $1800. Labradar becoming common for the more upmarket shooter. Its big bucks to setup with the top equipment no disputing that.
I have used a lead bath in my Lee melting pot. Lead fumes are dangerous. The problem I had was lead sticking to the case. Sometimes you cannot remove it easily.
MikeMcCasland
Team Texas F-T/R
I think they just added that info/data in the past 24-36 hours. That is very interesting supplemental info, and answers some of the questions/concerns brought up here.
Thanks for bringing attention to the additional info.
jthor
USAF Shooting Team
No problem! I’m really hoping this gets some of the Salt Bath Annealers to test their brasses Vickers Hardness from before and after annealing with the same lot number fired the same amount of times. From my understanding from one of AMPs videos in the past, they stated part of the reason they anneal to the level they do is to prevent the hardness creep between each firing. I’ll go find it. I might be wrong on that, but I swear I’ve seen it in one of their articles or videos.
BoydAllen
Gold $$ Contributor
I make no claim to expertise in this area but I think that relating some experience with annealing might benefit this discussion.
Some years back, a friend was seeing quite a bit of variation in shoulder bump, from the same die setting, for a couple of magnums, that I was working with him on for load development, so I suggested that he purchase a two torch machine and several different "temperatures" of Templaq, 300, 400, and 500 degree. The machine brought the case into the flames where it paused for a time that was controlled by a rheostat.
We did the initial investigation with a single case, since it was based on the levels that the Templaq darkened down to. We just cooled the case and removed the residue from the previous test before reapplying, and retesting. The Tmplaq was applied in narrow stripes from the bottom of the shoulder to the case head.
What we found was that if we used a time in flames that burned the 500 degree down to about where the annealing colors are on Lapua brass that we were pretty close to where we wanted to be. After that we only used the 500 degree. Case necks were either skimmed for uniformity, or in the case of the .338 Lapua brass, un turned.
At that setting, we ran a few cases through and tested them by sizing them and did not get the improvement that we were looking for, so we increased the time by a second and that did what we were looking for. The shoulder bumps were much more uniform, and the neck hardness was high enough that we had no problems with the effects of feeding from a magazine for multiple shots. As we continued with our load testing, we discovered that after a couple of firings that the variations in shoulder bump reappeared, leading us to conclude that annealing every other firing would be required.
The reason for this story is to point out a previously un discussed way of evaluating the effect of flame annealing.
Another friend who used a simpler method, flame annealing with a single torch and case holder on a cordless drill, using a metronome for timing, with Templaq, found his seating force for Lapua .223 brass, which had been heavier than he wanted, and somewhat irregular, much improved.
I know that these methods of evaluation are much less impressive than hardness testing or grain size evaluations but I think that for most of us they could be useful. By combining a way to look at temperature, decent control of time in flame, and a way to evaluate the results that does not require special equipment we were able to achieve the goals that we were looking for.
Some years back, a friend was seeing quite a bit of variation in shoulder bump, from the same die setting, for a couple of magnums, that I was working with him on for load development, so I suggested that he purchase a two torch machine and several different "temperatures" of Templaq, 300, 400, and 500 degree. The machine brought the case into the flames where it paused for a time that was controlled by a rheostat.
We did the initial investigation with a single case, since it was based on the levels that the Templaq darkened down to. We just cooled the case and removed the residue from the previous test before reapplying, and retesting. The Tmplaq was applied in narrow stripes from the bottom of the shoulder to the case head.
What we found was that if we used a time in flames that burned the 500 degree down to about where the annealing colors are on Lapua brass that we were pretty close to where we wanted to be. After that we only used the 500 degree. Case necks were either skimmed for uniformity, or in the case of the .338 Lapua brass, un turned.
At that setting, we ran a few cases through and tested them by sizing them and did not get the improvement that we were looking for, so we increased the time by a second and that did what we were looking for. The shoulder bumps were much more uniform, and the neck hardness was high enough that we had no problems with the effects of feeding from a magazine for multiple shots. As we continued with our load testing, we discovered that after a couple of firings that the variations in shoulder bump reappeared, leading us to conclude that annealing every other firing would be required.
The reason for this story is to point out a previously un discussed way of evaluating the effect of flame annealing.
Another friend who used a simpler method, flame annealing with a single torch and case holder on a cordless drill, using a metronome for timing, with Templaq, found his seating force for Lapua .223 brass, which had been heavier than he wanted, and somewhat irregular, much improved.
I know that these methods of evaluation are much less impressive than hardness testing or grain size evaluations but I think that for most of us they could be useful. By combining a way to look at temperature, decent control of time in flame, and a way to evaluate the results that does not require special equipment we were able to achieve the goals that we were looking for.
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I anneal after every firing. I anneal so that bullet seating force is not excessive and consistent.
I shoot with folks that use induction annealing, torch annealing as well as hot salt annealing.
I believe that to a degree, it makes no difference how you do it, as long as you experiment enough to assure that your cases have uniform seating force, lower seating force and that the base of the case does NOT anneal.
I use an Induction annealer, specifically an Annie.
When you induction anneal, you use an oscillator frequency low enough that skin effect does not fail to anneal in the center of the neck. So, the actual heating is from a very high current induced in the neck by a high frequency AC drive which thinks the round, thin neck is a shorted turn of a transformer. This high current induced in the case neck causes internal heat in the case neck.
A torch annealer uses a high temperature flame to envelope the case neck and part of the body and that heats up the case material. As the neck is only 10-15 thousandths of an inch, it heats pretty quickly and consistently.
A hot salt bath transfers heat to the case material from a liquid medium that is way cooler than a flame and the salt -brass interface is of questionable efficiency in transferring heat to the brass. This causes the case to be immersed in the bath long enough to anneal the neck properly.
To me, any way you choose to anneal is not important as long as you develop a process that just gets the neck to the point where it allows consistent and effective annealing without damaging the other end of the case.
I like my Annie as it is as effective as an AMP but more than half as expensive. I don't like flames as most do not have pressure regulators on the gas flow so temperature is not closely controlled. Also, a flame annealer is big, needs gas bottles and has an open flame. A salt bath annealer has, to me, many reasons to not use this method. First, you need a vessel full of molten salt that is heated to a high temp. and must have some heat source to accomplish this as well. I don't know how salt bath units work, but I don't like the idea of a tub of ultra-hot molten salt sitting on my bench with either an electric heater of a gas burner.
And, yes, I'm an engineer, but not a metalurgist.
I shoot with folks that use induction annealing, torch annealing as well as hot salt annealing.
I believe that to a degree, it makes no difference how you do it, as long as you experiment enough to assure that your cases have uniform seating force, lower seating force and that the base of the case does NOT anneal.
I use an Induction annealer, specifically an Annie.
When you induction anneal, you use an oscillator frequency low enough that skin effect does not fail to anneal in the center of the neck. So, the actual heating is from a very high current induced in the neck by a high frequency AC drive which thinks the round, thin neck is a shorted turn of a transformer. This high current induced in the case neck causes internal heat in the case neck.
A torch annealer uses a high temperature flame to envelope the case neck and part of the body and that heats up the case material. As the neck is only 10-15 thousandths of an inch, it heats pretty quickly and consistently.
A hot salt bath transfers heat to the case material from a liquid medium that is way cooler than a flame and the salt -brass interface is of questionable efficiency in transferring heat to the brass. This causes the case to be immersed in the bath long enough to anneal the neck properly.
To me, any way you choose to anneal is not important as long as you develop a process that just gets the neck to the point where it allows consistent and effective annealing without damaging the other end of the case.
I like my Annie as it is as effective as an AMP but more than half as expensive. I don't like flames as most do not have pressure regulators on the gas flow so temperature is not closely controlled. Also, a flame annealer is big, needs gas bottles and has an open flame. A salt bath annealer has, to me, many reasons to not use this method. First, you need a vessel full of molten salt that is heated to a high temp. and must have some heat source to accomplish this as well. I don't know how salt bath units work, but I don't like the idea of a tub of ultra-hot molten salt sitting on my bench with either an electric heater of a gas burner.
And, yes, I'm an engineer, but not a metalurgist.
If you use a BernZomatic torch, the regulator is built into the torch.
I have some Hornady 6.5 creedmoor brass. When seating, I was getting 80-90 with some touching near 100 PSI on my 21st century arbor press.
After salt bath annealing, on the next load PSI dropped down to 60-80.
Didn't change anything else other than the salt bath annealing.
After salt bath annealing, on the next load PSI dropped down to 60-80.
Didn't change anything else other than the salt bath annealing.
I know this is a zombie thread. However just want to put more info up for those considering SBA, despite AMPs research.
Little history I work for a company that builds nuclear reactor parts, they actually use and have salt bath annealing tanks on site.
Here’s a Milspec Notice cold worked copper alloys. Hhhhmmmm isn’t brass a copper alloy, isn’t what we as shooters worry about is cold working induced stress.
MIL-S-10699B, MILITARY SPECIFICATION: SALT, HEAT TREATING (FOR METALS) (01-DEC-1977) [NO S/S DOCUMENT]., This specification covers crystalline heat-treating salts suitable for use in the molten state for normalizing, annealing, hardening and tempering cyclic annealing, process annealing, martempering and sustempering of carbon and alloy steels, hardening of high speed steel, heat-treatment of light alloys, annealing and stress-relieving of cold-worked copper and copper-based alloys.
A Magazine article about it.
Now I know AMP wants to sell their machines and fine as though they maybe there are other ways.
Canuckenstein
Little history I work for a company that builds nuclear reactor parts, they actually use and have salt bath annealing tanks on site.
Here’s a Milspec Notice cold worked copper alloys. Hhhhmmmm isn’t brass a copper alloy, isn’t what we as shooters worry about is cold working induced stress.
MIL-S-10699B, MILITARY SPECIFICATION: SALT, HEAT TREATING (FOR METALS) (01-DEC-1977) [NO S/S DOCUMENT]., This specification covers crystalline heat-treating salts suitable for use in the molten state for normalizing, annealing, hardening and tempering cyclic annealing, process annealing, martempering and sustempering of carbon and alloy steels, hardening of high speed steel, heat-treatment of light alloys, annealing and stress-relieving of cold-worked copper and copper-based alloys.
A Magazine article about it.
Use of molten salt in heat treatment | Thermal Processing Magazine
At the turn of the 20th century, the use of molten salt as a heating and quenching medium for steels was developed in England. It rapidly came into use in E ...
thermalprocessing.com
Now I know AMP wants to sell their machines and fine as though they maybe there are other ways.
Canuckenstein
RegionRat
Gold $$ Contributor
Yup, pretty much all of the methods are still in use.
When the right folks are making the decisions, there is a trade study with lots of parameters in consideration. That leads to a variety of methods still being used since there is a variety of parts and materials to be treated and no single method can be said to be the best at everything.
Your post caused me to go back and scan the thread again. I took away a different perspective as someone who was directly involved with the topic for a long time.
I will remind all who are reading about annealing for reloading, as compared to making the cartridges in the first place, that we use hardness as a proxy value, not that we are all that concerned with hardness.
As a weapon system designer, you look at a cartridge case in several ways. One way we look at it is to tie up and bring all the other parts to the party, but then when the time comes it is viewed as a part of a pressure vessel. When we design pressure vessels, we are deeply concerned with several mechanical material properties, and for now I will say the hardness isn't directly high on the list.
When you read technical papers on cartridge brass or general papers on thin walled brass annealing, try to keep in mind why you are looking at hardness, versus the other places where you will see grain structure or other properties measured. Grain structure is important in some ways, but it isn't really the concern.
Also, try to remember that we heat treat at several steps along the way from a little cup or puck to the finished cartridge. We allow some of that work hardening to build up in some places, and want it lower in others. It is relatively easy to measure sample hardness values, and not so easy to directly measure the properties we actually care about. The good news, is that the important properties are roughly coupled to hardness in this context, so we use one to infer another.
There are places in mechanics where hardness is specifically critical and the point of the heat treat is then specifically to harden, but not in the context of what we are discussing. We use hardness as a proxy for all the other properties we want like the modulus, ductility and strength values that come with it.
We often study the properties of bulky samples that have no resemblance to a thin walled cartridge in order to make lab study easier. The heat treatment of those bulky samples create differences that we must navigate to insure the results are still meaningful when we jump to thin walls like in cartridges.
Work hardening alpha phase brass changes many properties and some more than others. Getting bulk standardized samples work hardened to the same level as a thin walled tube is different, and so are the thermodynamics of getting thin walled tubes to temperature. The modulus and strength properties that are important as a pressure vessel between the two types of samples, are tied to each other by the hardness value.
For example, I can make standardized tensile test samples that are very easy to measure in terms of all those important properties I mentioned, but to work harden and heat treat them the process isn't the same as a little tube like a cartridge neck. And, since making direct measurements on tiny thin samples also creates difficulties that are expensive to solve, we accept hardness as a proxy.
In the end, we use the hardness value as a proxy to jump between what happens to cartridge brass that is tiny and difficult to measure and the bulky standardized samples that we think we understand.
Factories have produced brass cartridges for a long time now, and the deep draw and heat treat methods are pretty well understood. As hobby reloaders, we are only mimicking what has been done by factories and are lucky that the properties of cartridge brass allow us to do this with a fraction of those resources.
YMMV
When the right folks are making the decisions, there is a trade study with lots of parameters in consideration. That leads to a variety of methods still being used since there is a variety of parts and materials to be treated and no single method can be said to be the best at everything.
Your post caused me to go back and scan the thread again. I took away a different perspective as someone who was directly involved with the topic for a long time.
I will remind all who are reading about annealing for reloading, as compared to making the cartridges in the first place, that we use hardness as a proxy value, not that we are all that concerned with hardness.
As a weapon system designer, you look at a cartridge case in several ways. One way we look at it is to tie up and bring all the other parts to the party, but then when the time comes it is viewed as a part of a pressure vessel. When we design pressure vessels, we are deeply concerned with several mechanical material properties, and for now I will say the hardness isn't directly high on the list.
When you read technical papers on cartridge brass or general papers on thin walled brass annealing, try to keep in mind why you are looking at hardness, versus the other places where you will see grain structure or other properties measured. Grain structure is important in some ways, but it isn't really the concern.
Also, try to remember that we heat treat at several steps along the way from a little cup or puck to the finished cartridge. We allow some of that work hardening to build up in some places, and want it lower in others. It is relatively easy to measure sample hardness values, and not so easy to directly measure the properties we actually care about. The good news, is that the important properties are roughly coupled to hardness in this context, so we use one to infer another.
There are places in mechanics where hardness is specifically critical and the point of the heat treat is then specifically to harden, but not in the context of what we are discussing. We use hardness as a proxy for all the other properties we want like the modulus, ductility and strength values that come with it.
We often study the properties of bulky samples that have no resemblance to a thin walled cartridge in order to make lab study easier. The heat treatment of those bulky samples create differences that we must navigate to insure the results are still meaningful when we jump to thin walls like in cartridges.
Work hardening alpha phase brass changes many properties and some more than others. Getting bulk standardized samples work hardened to the same level as a thin walled tube is different, and so are the thermodynamics of getting thin walled tubes to temperature. The modulus and strength properties that are important as a pressure vessel between the two types of samples, are tied to each other by the hardness value.
For example, I can make standardized tensile test samples that are very easy to measure in terms of all those important properties I mentioned, but to work harden and heat treat them the process isn't the same as a little tube like a cartridge neck. And, since making direct measurements on tiny thin samples also creates difficulties that are expensive to solve, we accept hardness as a proxy.
In the end, we use the hardness value as a proxy to jump between what happens to cartridge brass that is tiny and difficult to measure and the bulky standardized samples that we think we understand.
Factories have produced brass cartridges for a long time now, and the deep draw and heat treat methods are pretty well understood. As hobby reloaders, we are only mimicking what has been done by factories and are lucky that the properties of cartridge brass allow us to do this with a fraction of those resources.
YMMV
Salt bath annealing is a poor way to anneal your brass.
Rick300
Gold $$ Contributor
I'm guessing you've never tried it because you are incorrect. I have achieved very satisfactory results with SBA. I have since moved on to the induction method, but only because I wanted to anneal in the house.
I would imagine as a reloaders ductility and elasticity has much more influence on our loads. IIRC from my college metallurgy class ductile is the metals ability to be cold worked, like when we resize brass. Elasticity is the ability to return to the original form after working.
Which is where we get spring back from? No?
However as you say values are tied to hardness. Hardness goes up ductility and elasticity goes down. If I am not mistaken I believe tensile strength and toughness go down as well. Hence why necks crack with out annealing after so many firing and loadings.
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