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Popsbengo

Molten Salt Annealing Rig

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Here's my molten salt bath annealing rig.  Shameless rip-off of a great idea from Ballistic Recreations 😁.  I needed a set up to fit my Lyman pot so I set about making one for .338Lap cases.  About £8 in stainless from eBay and salts from APC Pure for about £24.  (It helps to have a lathe).

Early development yet but looking good.  5sec at 520deg C at 20mm depth of salt is too long.  I found 3 sec seems to give the desired affect for a .338 Lap case.  A lot better than gas burners I think (I built one of those too).

I must admit it puts the willies up me a bit having half a litre of 520deg C salt in front of me. 😟  When melting the salt mix for the first time there's a bit of scum and fizzing as impurities are burnt off, the second melt was much cleaner.

Pics of results soon

Anneal 1.jpg

Anneal 2.jpg

Anneal 3.jpg

Anneal 4.jpg

Anneal 5.jpg

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Reading about exploding salts from moisture etc worries me!

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It should worry any sensible person!  However if you're sensible why not consider it.  After all water in the chip pan is a bad idea too 😁

 

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Interesting, my gunsmith is in the process of assembling the components for one. The salts are arriving today I think. I like the idea that you have exact control of the temperature.

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2 hours ago, Chris-NZ said:

Interesting, my gunsmith is in the process of assembling the components for one. The salts are arriving today I think. I like the idea that you have exact control of the temperature.

Yep, the temperature control is near perfect. Once you have the right depth of insertion for the case set, the only variable is the time and that's easy to manage.

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Hi,

got the salts from APC in hyde. Got the thermometer from eBay at a fraction of the company selling the complete kit. Just fancy not paying through my nose for the privilege. 

Only now need the plate to take my cases. Again don’t fancy paying $47.00 shipping to uk. Final option is to make one !

 Nick 

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36 minutes ago, Nick 53 said:

Hi,

got the salts from APC in hyde. Got the thermometer from eBay at a fraction of the company selling the complete kit. Just fancy not paying through my nose for the privilege. 

Only now need the plate to take my cases. Again don’t fancy paying $47.00 shipping to uk. Final option is to make one !

 Nick 

Yep, I got some stainless discs from eBay including stainless pop rivets and screws.  Setting the case depth is a matter of suck it and see.  Don't be surprised the salt mix is really scummy as it melts, it does get clearer as it heats to the final temperature.  PS, the case in my pictures was just for setting up, the cases must be de-capped before processing.

Good luck

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Here's some .338 trial cases compared to a brand new Lapua out of the box. The black line is to show the colour change as the pic is a bit poor in that respect.

3 sec seems to give sufficient heating to anneal and moderate heat transfer up towards the head. 5sec seems a touch too long.  The neck 'springiness' seems to be the same as the new case and definitely softer than the fired cases I have to compare with so I conclude (admittedly in a less than scientific case study) that molten salts at 520C work very well and are very repeatable.

Not bad for under £100 for the metal, new Lyman lead pot and chemicals (including safety equipment😀)

 

IMG_2184.jpeg

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Are you dropping them into water as you go?

Pete

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Apparently after salt annealing the cases need to be dropped into water,I have seen the salt annealing been done a fellow shooter has this set up.

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12 minutes ago, Re-Pete said:

Are you dropping them into water as you go?

Pete

Yes, straight into a bucket full, kept well away from the salt pot as a splash of water into the salt would be unpleasant indeed!  Water cooling has no relevance to the annealing process, it's just to clean off the salt carry-over. It's also convenient to have somewhere to put the hot brass.

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How much salt did you buy? I have the same Lyman pot and I've been trying to guess how much I'd need to get a decent depth once melted.

Pete

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4 minutes ago, Re-Pete said:

How much salt did you buy? I have the same Lyman pot and I've been trying to guess how much I'd need to get a decent depth once melted.

Pete

I find a total mix of 500g to be about right.  I did buy extra because it was economic and useful to have top-up as some is lost due to carry-over.

When you do your first melt the salts combine in a eutectic mixture and solidify in one hard 'puck'.  I suggest not leaving the jig in the pot, remove while the salt is still hot.  When everything is cold I take the pot out of the heating element and knock the 'puck' out into a plastic bag for storage as the salts are hydroscopic.

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There is an article on salt annealing on a web site Target sport shooting? Bloody brain can’t remember the correct title! It gives the amount of salt required to be mixed. Article is by a Paul Parkinson cracking read.

 Nick 

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1 hour ago, Nick 53 said:

There is an article on salt annealing on a web site Target sport shooting? Bloody brain can’t remember the correct title! It gives the amount of salt required to be mixed. Article is by a Paul Parkinson cracking read.

 Nick 

I use 50% potassium nitrate;  45% sodium nitrite;  5% sodium nitrate -  by weight.  At 500C there is no fuming I can detect.   Be careful about going over 550C things start to get 'exciting'.

I accept no liability for the correct mixture🤔

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Thanks.

Since Paul lives around the corner me we will mix the salt together.

( Preferably not in the kitchen) !!

 

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Popsbengo - I was going to have a go at salt annealing this year, after reading the other thread on the topic. Any chance you could give us a list of the bits or dimensions needed to make the jig for the pot? The shoulders of giants, and all that :)

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3 minutes ago, nicklock said:

Popsbengo - I was going to have a go at salt annealing this year, after reading the other thread on the topic. Any chance you could give us a list of the bits or dimensions needed to make the jig for the pot? The shoulders of giants, and all that :)

Sure, it's simples if you have tools.  I used a Lyman dipping pot which is 100mm I.D. and 70mm deep.   No idea about the Lee pot dimensions but everything should scale.

I used stainless steel throughout as I didn't want to be cleaning corrosion off the jig.  The top plate is 3mm and the bottom plate is 1.5mm; if I was doing again I'd use 1.5mm throughout as it's plenty stiff enough.  Size isn't critical (oo-err) so get what's cheap and handy.  I would get the discs cut unless you have the tools.  Actually the top plate can be square if it's easier.

My top plate sits over the lip of the pot (everything hangs off that plate) so as long as it's bigger than the pot, size isn't critical.  The inner disc is a good fit to the inside of the pot (1mm undersize on diameter) and is spaced 5mm below the top disc. I used 6mm stainless rod, drilled as spacers and tapped M3 for the legs.  The 'legs' are not supporting anything they act to hold the jig secure in the pot, the last thing you want is the jig moving about with super hot salts !

The case 'holder' is 10thou stainless shim-stock, easy to cut with shears,  drilled and s.s. pop-riveted onto the lower disc,  the depth of the holder needs calculating dependant on depth of salt.  I have approximately 500g of salt mix in the pot to provide decent heat soak and a good depth for flexibility in setting up.

This is where I got the discs from:   eBay:  STAINLESS STEEL Blank Round DISCS 304 Grade Sheet Metal Precision Laser Cut  sold by 'sgs132'.   The shim-stock was from an engineers supplier, I don't recall who as I've had it years.  6mm rod is easy to get.  Don't forget that drilling and cutting stainless requires sharp tools, correct speeds (Google it if you need to) constant pressure on feed and don't dwell as s.s. work hardens like a bitch.  Tapping M3 can be expensive if you don't use good taps and technique 😄  If you know all this, apologies for teaching Granny to suck..

Drilling and tapping the rod is ok for those that can and have the kit, if not try model engineering or robotics supply websites.

I already had the type K thermocouple and thermometer.  You need a probe that's designed for over 500C - many on eBay are type K but are not suitable at +400C, the junction melts!

Best of luck, if you need anything further please ask.

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Excellent info mate, thanks for that! :)

Yes, SS is a bit of a bugger to machine compared to the normal stuff... I'm wondering if mild steel and a damn good coating of high-temp paint ( https://www.rawlinspaints.com/home/metal-paints/heat-resistant-paints/440-rust-oleum-heat-resistant-paint-750c.html ) might do the job just as well?

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20 minutes ago, nicklock said:

Excellent info mate, thanks for that! :)

Yes, SS is a bit of a bugger to machine compared to the normal stuff... I'm wondering if mild steel and a damn good coating of high-temp paint ( https://www.rawlinspaints.com/home/metal-paints/heat-resistant-paints/440-rust-oleum-heat-resistant-paint-750c.html ) might do the job just as well?

Maybe, I just don't like the idea of a potential combustable coating mixed with a super hot oxidising salt - for "fun" just try a splinter of wood when the salt's hot !! 😮😱

SS is best for immersed parts for sure.  I also like the fact that the SS is a relatively poor transmitter of heat and the top plate is farkin' hot but nowhere near the salt temperature.

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1 minute ago, nicklock said:

I should make a poached egg adapter as well then? ;)

Can you make a video of the first trial please ?  Such fun!

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Having ‘discovered’ Paul Parkins article last weekend I’ve been working on gettting the bits over the week and just waiting for stuff to arrive....

Salts ordered from apcpure, s’be delivered Monday;

Thermometer and thermocouple ordered Wednesday pm from thermosense... manufactured the thermocouple and despatched Thursday, received Friday! Really helpful, friendly advice.....highly recommend them!;

Desktop scales and check weight from ourweigh, received Friday;

caseholder from ballisticrecreations on it’s way.... but I have ordered some bits to make my own - I thought the fixed deck height c’be improved so I’m thinking I could adapt (bodge) an adjustable deck using a spring toggle plaster board fixing to raise and lower the deck height. Got some stainless mesh coming for that.

Also ordered a Lee melting pot but everything else might be here before that. Downer.

 

cheers

 

Fizz

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