Salt annealing, my journey

[Milligan]

I have recently dabbled in using the salt bath annealing process and thought i would share what i have learned. Usual caveats and warnings apply I.e don't blame me if you burn your face off or your house down.

Kit

• Lee melter
• M6 x 50mm bolts and nuts, stainless
• Sheet steel
• Thermocouple
• Digital thermometer
• Potassium nitrate
• Sodium nitrite

Both salts used in food curing so readily available. Research showed a ratio of 40% potassium 60% sodium.

PID controller not essential but fun to make and generally a little more precise.

Idea is to heat salt up to 500c and then dip the appropriate bit of brass for circa 6 sec then quench.

Supposedly it's more forgiving than flame as the salt cannot overheat the brass and you'd have to leave it in for a very long time to get the temp into the case head or web.

Main gripe so far is establishing and maintaining the correct level of salt as it's difficult to see, difficult to remove said 500c molten salt...

Timing is done via metronome, I am still coming to grips but it is supposedly quite forgiving.

Melting salt the first time is a bit squeaky bum as the impurities and melter burn off and settle. Not something you want to do without ventilation!

More pics to follow.

 

[Woodsmoke]

Now that's a labour of love! What made you decide to go down this route instead of just running a flame over the necks? Very cool project

 

[Milligan]

Now that's a labour of love! What made you decide to go down this route instead of just running a flame over the necks? Very cool project

Curiosity and price...

 

[CarlW]

Fascinating. What a great project. Can't decide whether you are ingenious, brave, or downright mental...?

 

[NigelM]

Awesome dedication to the cause. Not sure I'm going be changing away from my current method any time soon though.

You certainly get to become a member of the Anorak Club.

 

[Klenchblaize]

Maximum points to the Op for endeavour but frankly it's simpy too damn messy to see rollout in my Reloading Den.

K

 

[CarlW]

Maximum points to the Op for endeavour but frankly it's simpy too damn messy to see rollout in my Reloading Den.

K

You wouldn't want to get any of it on your label-maker, eh...? I like your thinking, KB!

 

[Milligan]

Maximum points to the Op for endeavour but frankly it's simpy too damn messy to see rollout in my Reloading Den.

K

Most of the mess is the base steel I use for welding... but no, not something you do inside

 

[Sharpie]

Molten lead works as well, maybe better, and is always present in my Lee melter. Doesn't stick to the cases if you have left the resizing lube on them. And is clean to work with.

K type thermocouple into a multimeter measures the temperature in the pot. The twiddly knob on the little Lee melter does not exactly regulate the temperature, rather the power input, same as on a basic £12 1000W electric ring (which I also use for casting lead bullets rather than the Lee pot, it's much better when you are working with several kilos of lead).

Dip the neck in up to the shoulder, pull out once the head starts to get too hot for bare fingers. Toss into cold water. Seems to work for me. Maybe I actually annealed them, I think I did, they certainly have consistent tension and seat very straight and don't split. Unlike the un-treated work-hardened ones.

Once you understand how these "simmerstats" work, it's easy to get the results (temperature) that you want, just by twiddling the knob carefully and observing the temperature. Up a bit, down a bit. No fancy PID controller required, unless that's your thing and you want to be accurate to within a few degrees, and why not ?

The brass doesn't care, as long as you have exceeded the annealing temp, for long enough, but not cooked the strong work-hardened parts towards the head. Skilful use of a blowtorch, and something to rotate the case smoothly also works, even just a toothpick up the primer hole. Lots of expensive machines available to automate something that you could do yourself with no more than a battery drill and some common sense.

The Lee pot has far more power than needed, turn it up full and it can get red hot, even boil the lead (not a good idea) I think it has a 750 Watt element (UK 240V) which is silly for such a small thing.

Infinite switch - Wikipedia

en.wikipedia.org

You could perhaps do an even better job with a £15 induction heater from China. My next project. Also might be useful for taking rusty nuts and bolts off cars without burning the surrounding parts with mapp gas or oxy-acetylene.

Full marks for effort. Don't fancy working with that hot salt myself, or keeping it away from stuff that it wants to oxidise, perhaps violently.

 

[Jon Smith]

15 quid chink tank oscillator will not be much use, you need to control the output a reasonable amount with a hard driven circuit.

 

[Milligan]

The pid controller was about 15 quid inc the ss relay. Keeps it very consistent.

With the cover on the pot there is minimal splash risk, which seems the main risk. Other than that I am not sure what you think it wants to oxidize?

 

[CarlW]

Is this a competition to see who can maim themselves most dramatically...?

 

[Longstrider]

I've seen what happens if even the teeny tiniest bit of moisture gets within a country mile of molten salts in a knife-makers forge, which had developed a new roof lining of salt, a new wall coating of salt and a new flooring of salt, all applied at over 800 degrees C and VERY quickly. Upon reflection and after deep thought I think I'd rather shove my backside into a garden chipper than muck about with molten salts !

 

[Milligan]

I've seen what happens if even the teeny tiniest bit of moisture gets within a country mile of molten salts in a knife-makers forge, which had developed a new roof lining of salt, a new wall coating of salt and a new flooring of salt, all applied at over 800 degrees C and VERY quickly. Upon reflection and after deep thought I think I'd rather shove my backside into a garden chipper than muck about with molten salts !

Nonsense. Unless you are talking about large introductions it's not different to hot oil and water or indeed lead.

 

[Klenchblaize]

You wouldn't want to get any of it on your label-maker, eh...? I like your thinking, KB!

And then there's need for a suitable forced air supply & extract system!

K

 

[CarlW]

And then there's need for a suitable forced air supply & extract system!

K

I do like fastidiousness in a fellow...

 

[Blobby159]

Curiosity and price...

GOOD FOR YOU 'Milligan'...!! We conversed about the possibilities, methodologies and initial gaining of the hardware apparatus a few weeks ago. No holding you back once there's that bee in your bonnet eh mate!!..

I would STILL like to go this route myself as the current gas torch and spinning spark-plug box spanner bit can be a bit of a pain and slow as it is needing constant management to ensure consistency.

I think this 'SaltBath' option takes a bit of this controlling worry away from the operator once set up properly, and it doesn't cost several hundred quid (or more, much more) if one goes the route of purchasing one of those lovely but costly mechanical turntable type devices to get this important annealing job completed successfully....!

"Well done that man' I say!

ATB ...... and shoot safely