Salt bath anealing

[WANTASHOOT]

Has anyone tried salt bath anealing? Seen it on Facebook a while back and seems pretty legit. Guy took a lead melting pot and heated a mix of Potassium nitrate and sodium nitrate. They melt at about 900F and he simply dips the case mouth into the solution for 6 seconds. He made a neat little case holder so he can do 2 cases at a time and it's kind of a heat shield so not to burn hands. Has anyone messed with this. Is there any negatives to this? Would a different salt be better like table salt (easier to get). Tell me what you all think?

 

[kvd]

This would certainly work. The potassium/sodium nitrate mixture is common for salt bath heat treating, which is use primarily for aluminum heat treating. Table salt - sodium chloride, would not work due the the fact it melts at over 1,400°F. At 900°F, I would adjust annealing time down to 3 to 4 seconds.

Quenching it in water, which is not necessary for annealing, will remove the salts.

Ken

 

[Mulligan]

Had never heard of this before this post, thanks I learned a thing or two.
The above video makes it look fairly straight forward.
CW

 

[Prose]

How much does a set-up like this cost?

 

[Texas10]

This looks to me like the perfect solution, no pun intended. However I am concerned about the temperature. Here's a quote from an article on this site.
http://www.6mmbr.com/annealing.html

"The critical time and temperature at which the grain structure reforms into something suitable for case necks is 662 degrees (F) for some 15 minutes. A higher temperature, say from 750 to 800 degrees, will do the same job in a few seconds. If brass is allowed to reach temperatures higher than this (regardless of the time), it will be made irretrievably and irrevocably too soft."

 

[mikecr]

This is great. Now I can drop lead dip for this
The most critical aspect of process annealing is temperature. So long as temperature is never allowed to be too high, timing doesn't matter -provided exposure is at least long enough. So you can leave a neck at 900degF all day long, and it won't 'over process anneal' or anything like that. Thing is though, you can't use 2000degF to try & do that.. The bath and temperature monitoring guarantee success.

 

[Highpower-FClass]

How much does a set-up like this cost?

Looking at the ballisticrecreations.ca site the costs are (presumed to be in Canadian dollars):
Salt - $10
Case Holder - $25
Thermocoupler - $25
Digital thermometer - $25

With the current exchange rate that gives ~66 USD

The Lee melter is $53 on the Lee Precision website, or $45 at Amazon.

A total of ~110 - 120 USD + shipping.

 

[TAJ45]

This looks to me like the perfect solution, no pun intended. However I am concerned about the temperature. Here's a quote from an article on this site.
http://www.6mmbr.com/annealing.html

"The critical time and temperature at which the grain structure reforms into something suitable for case necks is 662 degrees (F) for some 15 minutes. A higher temperature, say from 750 to 800 degrees, will do the same job in a few seconds. If brass is allowed to reach temperatures higher than this (regardless of the time), it will be made irretrievably and irrevocably too soft."

Interesting. I took the guided tour at Sierra's Sedalia plant two weeks back.
When we came to the annealing oven, he mentioned 1200°. I twigged to that but by this time, even with some die work in my Toolmaker history, I was in sensory overload. Apparentally, copper is a different kettle of fish. Seeing that the jackets all start on coiled rolls, different thicknesses, all abt 4-6" wide, it does undergo stress with the stamping, drawing and forming. Obviously, they have it down pat by now.

 

[kvd]

This is great. Now I can drop lead dip for this
The most critical aspect of process annealing is temperature. Provided your temperature is never allowed to be too high, timing doesn't matter -provided exposure is at least long enough. So you can leave a neck at 900degF all day long, and it won't 'over process anneal' or anything like that. Thing is though, you can't use 2000degF to try & do that.. The bath and temperature monitoring guarantee success.

Your statement is correct in that once the proper annealing temperature is obtained, no further change in hardness takes place with additional dwell time. There are a few things to consider though. One is that there is a temperature /time relationship to annealing brass. In other words, it may take 30 minutes at 500°F and only a few seconds at 800°F to accomplish the same annealed hardness in the brass. In addition, the longer one dwells at annealing temperature, the more the entire case is equilibrating to that same temperature. Remember, we only want to anneal the neck of the cartridge. To anneal the entire case would be disastrous. Thus, high temperature and short dwell times are the key to annealing only the neck and nothing else.

Ken

 

[mikecr]

Good deal, but don't ever trust Canadians with gun item sales/service..
I've been burned twice in a row with this, and have over $10,000 (US) worth of gun components hung up in canadian border warehouses somewhere(nobody knows where, for how long, how to get my stuff). Over 10yrs now..

Anyway, I have a lot of experience lead dipping. The greatest part about dipping temperatures is that they do not exceed ideal temperature.
For a batch of wssm cases I intended to fully improve, I was able to set 900deg(as measured) and dip cases to mid body, while holding the heads with bare fingers, 30sec total insertion time, and then quickly pull and drop in water to stop any heat migration. Below 450degF, nothing is happening with brass grain structure. The webs were fine, and I have over 60 reload cycles on these cases now. Pockets still tight.
It would be a disaster to try this with timed flame or induction annealing..

 

[mikecr]

Something we need to find out is how fast the salt cools/solidifies, as in -does it stick to cases without timing tricks and/or a release agent employed(like with lead).

 

[kvd]

Potassium Nitrate and sodium nitrate are readily soluble in water. If one were to anneal via molten salt, all that would be required is to drop the annealed cases in a bucket of water. The salts will dissolve with little or no effort.

Ken

 

[WANTASHOOT]

http://www.hightemptools.com/Salts.html This is one place you could buy the salts. $4.50 per pound. I have heard the shipping is pretty spendy but probably a one time expense.

I plan at some point to try this but work has all my time. When I do I will post all the details.

 

[WANTASHOOT]

Did a bit more searching and if you overheat the salt it can give off some bad fumes. Not sure if you have heard of smoking bath salts (google If you haven't) but I guess it is pretty nasty stuff. Not sure exactly what chemicals are given off but I wanted to let you guys know there appears to be some risk if you let the temp get too high.

 

[mikecr]

With any dip we should measure the temperature. The whole point of it is to have the temperature right.

 

[WANTASHOOT]

Nitre or niter blue from brownells (bleuing salts) are the exact same stuff as used in the video above or the link I posted earlier.

 

[Joe R]

I really like this method. It is fast, compact, very consistent and inexpensive, a tough combination to beat. At that price it is worth enduring the "one at the time" tedium. If I didn't already have an MRB annealer I would go for this.

Some of you may be interested in the Science of Annealing Brass paper attached.

Kindest regards,

Joe

 

[foxguy]

Just A question on this process?

Would the fumes from the heated salts be considered unhealthy?
Can this annealing process be done safely indoors.

 

[SheepDog]

Potassium, ammonium and sodium nitrate are oxidizers. The first thing they release when heated is oxygen. If there is any carbon in the crucible it will burn. They stabilize thermally as nitrites giving off free oxygen.

 

[dickn52]

Heated 'salt' baths are common in manufacturing for tempering metals.