Annealing with Hot Sand?

[hounddawg]

Anyone here ever gave it a thought? All it would require is a lead pot and some playground sand. Heat it up to 750 or 800 dip the cases in up to the base of the shoulder for a few seconds. Time period could be determined with liquid Templaq, heating would be even and it would not be that hard to rig a jig to to 10 or more at a time. Make it adjustable and with a positive stop to make sure the cases are dipped to the bottom of the shoulder consistently. No flames and no explosive salts required


Thoughts and opinions ?

 

[totalloser]

I built a jig when I did it, and quickly concluded that the jig was a waste of time. I used glass bead blast media rather than sand which worked better for me. The jig I built was 1/4" aluminum discs with 6 holes for brass, and a bump stop disc for length. It was a pain to get depths correct and I got burnt fingers more often than no jig. It was also hard to get consistent timing on place and pull.

My takeaway was that placing depth was pretty easy manually. Aluminum was probably a *terrible* material choice due to conductivity, few materials will survive the temps involved, and settling the jig in the media correctly was not only tricky, but also obscured view of the media- which tended to shift around. Basically I used aluminum because cutting a disc was easy and I had it laying around.

This compared with just dropping in 3 depth by eyeball, then dropping 3 more and pulling the first 3- simply *worked*. At least for me.

I'm guessing you were watching this one:
https://thefiringline.com/forums/showthread.php?t=594883

I could tack my results on here later, but it might be more than a month.

Thoughts and opinions? I think it's a fantastic process- that needs some pioneering scientific experimentation to work out best practices.

 

[Jim Watson]

Any thought of sparging compressed air under the bed of sand for a fluidized bed of heat transfer medium?

 

[hounddawg]

for the jig I was thinking more along the lines of a ring of shellholders tack welded to 1/4 plate. Suspend the cases upside down and run a band around the heads to stabilize. A strap steel frame would straddle the lead pot. In the middle of the top of the frame a slot where you could slip in a piece of threaded rod tacked to the shellholder plate assembly. Stop nuts and washers on the rod could be used for depth control. Just dip them in and pull them out

A 3.25 inch diameter circle has a circumference of over 10 inches. With a 4 inch pot you could easily do 8 cases at a shot.

Also I think I would prefer plain old fine sand, dry fine sand would flow around the brass with minimal resistance and is available everywhere.

BTW I have no plans to attempt this I am just thinking outloud. I have an Annealeze which works perfectly well.

Edit - the spoiler could be the heat being radiated off the sand. There is a possibility the case body could be overheated before the neck and shoulder would anneal

 

[totalloser]

I *think* it will work with sand, and it sounds like your fixture concept wouldn't have some of the problems that mine did. Wiggling mine down through sand was impractical, but it would settle through bead media.

I was doing six at a time and just plunking them in batches of three into the media. I still like the bead media better, but without my type of (failed) fixture, sand is much less of a problem.

Most of the problems with the fixture I did, had to do with it sitting *in* the media.

But honestly, after doing it, I think it would be pretty difficult to find something that works better than simply placing them in the media and pulling them out. Even with slippery bead media they will stand up with minimal penetration past the shoulder. If I could make a magic fixture without any effort, it'd be something to keep my fingers from getting burnt on the pot. The case heads never got hot enough to be a problem for bare fingers. They just aren't in there long enough.

Essentially the process works pretty well with just a pot, some media and something like 750F tempilstik or tempilaq. A lead thermometer or thermocouple and gauge would be pretty instructive though- hence I decided to order one.

I do sort of wonder if some sands might have stuff that would cause grief when heated- but I don't know. Blast beads are nowhere near melting point, and will be impurity free. But sand will generally make them "stand" better.

Not sure on air, but fluidizing would cause serious problems the way I was doing it. But there may be other processes yet to be pointed out.

 

[hounddawg]

perhaps your are right with the glass media, you have actually tried this. For me it was just a 3 beer brainstorm.

While I still anneal after almost every firing, I am drifting back to the skeptics side on whether it does anything worthwhile so I am not going to put any time or effort into refining the idea. I am looking forward to Litz coming out with his next Modern Advancements book with extensive testing of annealing. His initial testing showed no benefits at all

 

[JeepHammer]

For case holder, anyone consider stripper clips mounted to something like wood?
Stripper clips load & unload pretty easy, if wood overheated try high temp fiber board?
If stripper clips work, it sure would be a cheap way to do things.

 

[Unclenick]

When I worked at YSI back in the 70's, the company built a fluidized bed of hot sand for testing high-temperature probes. The sand was heated and stirred by hot air forced up through it. That was necessary both to distribute heat throughout the sand for uniform temperature of the bed and also to prevent the stainless jackets of the probes under test from drawing enough heat from the sand around them to influence the measurement, as happened with static hot sand, though I don't recall the magnitude of the error. IIRC, the fluidized bed had to be run cold under a vent hood for a couple of weeks to round and dull the sand edges and eliminate the resulting dust.

Anyway, I think the bottom line is that it would be better to use a heated container of something that is a better heat conductor than silica. You could hollow out a large soldering iron's tip and fill it with tiny ball-bearings and stick the cases down into those. Temperature control would be easy with that, too.

Years ago I bought a couple of plates from Sinclair's room on Commercial Row at Camp Perry that had steel pegs welded in. The instructions were to heat the plate to about 700°F and start setting cases onto the pegs. It has 10 pegs. You set the pace so about 20 seconds have passed by the time you get back to the first one to remove and replace it. A 2-second pace is perfectly possible to keep up. It works fine to prevent neck splits, but if you want to stress-relieve shoulders, it doesn't do much there.

For contact annealing, the molten lead method or running a chamber reamer into the same fat soldering iron tip is probably better. Possibly, a coaxial post should be installed with it. But then you need a different tip for each chambering.

 

[totalloser]

Actually stripper clips were one of my first thoughts- I was thinking half moon clips or revolver quick loaders. In theory it made sense, but in practice it added an extra step for no tangible benefit. Having said that, if doing small volume and fear of the pot, it could protect from the occasional scalded hide. What I would most worry about, would be the extra weight making depth setting difficult. This might be where sand would be superior.

I'm pretty skeptical of liquid bath. Blast media works really well. From what I've read (*) about liquid baths, they are a pain. And *much* more hazardous. The lack of heat transfer is a *benefit* rather than a drawback. It allows a quick *but limited* (!!!) transfer of heat. This makes it an extremely fast and forgiving process compared to... well anything I've ever heard of.

edit: I take that back- magnetic low voltage high frequency induction would probably be more forgiving. And fully automated could be faster. But I don't think you could build that setup for less than ten grand. The media dip runs less than fifty bucks.

I used to do fluidized bath for powder coating motor armatures. We flowed a very minimal amount of air, and resonated the pot to the harmonics of the media. Running your hand through it felt more like gas than liquid. Shielded hot dip process, then finish bake.

 

[totalloser]

High temp fiberboard? !!! Might make an excellent burn shield to protect fingers from the pot! And also protect a tipped shell. They usually stand fine, but I have bumped them and then got burnt trying to prop them back up.

Just did a search- that stuff is SLICK! I wonder if I could get away with chucking it in a fixture support to lathe turn a ring for the pot edge?

And DUDE, that stuff looks like a fix for the pain in the butt refractory shielding woes on my foundry lid. Rock on!

 

[T. O'Heir]

Sounds like a great deal of fuss and bother for something as simple as annealing. Especially as annealing brass occurs at approximately 650-700 degrees Fahrenheit. 750 to 800F is too hot. Even if you could control the heat of sand well enough.

 

[hounddawg]

RCBS has a lead pot that promises plus or minus 10 degrees but Uncle Nick brought up a good point about keeping the temperatures even from to to bottom in a non liquid medium. I absolutely refuse to try salts, way too dangerous. Hot sand or glass beads at 700 + F is enough to get me to wear boots, goggles, a leather apron, and welders gloves

 

[totalloser]

750-800 media temps is not too hot for the brass. Keep in mind, this is merely the temp of the media- not the temp the brass will get to. We are, afterall, predominantly comparing this to a 3000F +- propane flame.

I really doubt being particularly accurate on the pot temps matters much. Why? Because the dwell time is going to be the important factor, and the media acts as a thermal bank to smooth out irregularities in temperature. Hotter media? Shorter dwell time. Heat through the media? Convection will move the heat via airflow in addition to conduction and even radiation (IR). Brass should only be dipped in about 1/4" and will be towards the center to avoid burnt fingers and irregular heat. Were I to guess, the minimal convection pattern pulls air through the center of the media since the perimeter is the location of highest heat around the much more conductive pot. In practice? These issues *seem* to not matter much. But I will eventually have some better answers.

Protection? I will tell you that hot sand or bead media is nowhere *near* as scary as molten materials. Glass isn't particularly conductive, won't stick to most protective gear, and can be brushed off. You could dump it on your cotton jeans and still make babies after doing a little dance, but you would NOT want a grain in your eyeball! I wore gloves at first but then quickly decided it was not necessary- though I did routinely burn a finger here and there. Not on the media though- it was the pot that would get me. Molten mediums can be pretty spectacular if they contact liquid too.

But the media is more than hot enough to ignite flammable materials like powder or lead styphnate. I'd absolutely keep this process where it cannot tip over anywhere near powder or primers.

Of course be especially wary of synthetic materials- like polyester pants for instance. Glass would *immediately* stick and melt the polyester which then would stick and burn the smokes out of things you'd rather not. Cotton? Might singe after a while, but brushes right off. A non synthetic whisk broom and metal dustpan might be a good idea. Tighty whities under the button fly is probably in order as well. Apron? Maybe so. If it managed to pour into a front pocket it would also be no fun!

But let me explain why I make some of these points: In my minimal experience playing with this process, it *appears* to not only be extremely forgiving, but also cheap and very fast. If a cheapo $35 Lee pot works, then this process is opened up to pretty much anybody who is willing to learn.

Give it a try and post some results. I have the gauge on order from Taiwan, so you guys have a month to beat me to it!

 

[totalloser]

One other random thought. Uncle Nick posted up the heated plate method- if the pegs had a ring around them, media could be put in each one. This would make it a precise fixtured process. Assuming the media stayed level (outside volume vs inside volume). But the quantity of media would be very little, and it would be more difficult to burn fingers. IE: safer.

Worth the hassle? I don't know. But I suspect it would work.

 

[hounddawg]

dog gone it, you guys about have me ready to give this thing a go next winter. There are some good ideas being thrown out. Stripper clips would certainly beat out the shell holders for the holder and the idea of using pipes filled with sand would help with the heat distribution. Get a copper round to fit the bottom of the pot then braze (not solder or sil braze) pieces of copper pipe to the round. All that would be left is a jig that would dip the cases to the right level and getting the timing. I am sure someone with a lot of ambition could tie in a case feeder with a bit of thought

I have to wonder why the big boys have not thought of this, or if they did think of it they did not follow through.

 

[Unclenick]

I agree that molten salts are a hazard, especially for those of us who sweat in the presence of heat.

The lack of heat transfer is a *benefit* rather than a drawback. It allows a quick *but limited* (!!!) transfer of heat.

Well, here's the fly in the ointment. Its either lacking thermal conductivity or it transfers heat quickly, but, by definition, those are mutually exclusive properties. In the case of sand, your first guess is correct: it lacks conductivity and therefore heat transfer is slow.

The thermal conductivity of cartridge brass (70:30 brass) is 120 W/mK, while for dry sand it is about 0.3 W/mK, or about twice what a pine 2×4 does across the grain. Another way to look at it is the thermal resistance of the sand is about 400 times greater than the brass. About 11 inches of dry sand is as good an insulator as 1 inch of styrene foam board. So you are looking at a significant temperature drop across some distance surrounding the interface surface. How big the drop will be trying to feed heat to the case sticking out of the sand will depend on its convection coefficient while losing heat to the air. Before you get to the steady state, you might argue the thermal inertia of the sand would dump enough heat into it to get where you want to go, but that has a problem, too. The thermal inertia, indicated by the thermal diffusivity of the material is 160 times smaller for sand than for brass. The ability of it to transfer head, measured by thermal effusivity, is 32 times smaller for sand than for brass.

So, to make it work, the sand will have to be kept at a higher temperature than the annealing temperature of the brass to make up the temperature drop. You'll have to allow time for the unstirred sand to reheat after you pull a case out, too. You've got a pile of measurements to make.

 

[hounddawg]

Good catch Nick. That was careless of me not to consider the thermal conductivity for the replenishment of the sand's heat. Copper BB's for the win. BTW heat always flows from the hotter to the colder object and the greater the delta T the faster the transfer

 

[totalloser]

Not mutually exclusive, these are two *different* properties. A 2x4 with heat applied to one side, say in the range of 450F- smoking hot- will not burn your hand on the other side. BUT touch the hot side and it might! The brass is touching the hot side so to speak. Both sides of the glass are the hot side, but lack of conductivity means that it can only transmit the surface heat promptly.

See what I mean? Contact with the hot side heats quickly, but lack of conductivity means it's not sustained at that level. I'd wager a logarithmic function, but to lay it out would require hard data, and I'm way to lazy to fool with such details just for the sport. I'd read about it though!

I have directly observed the process as being enough to anneal brass, and do so quickly. Heat loss from the process? I am doubtful that the brass could lose it enough heat to matter much considering what's being dumped into it from the element, but I wasn't watching for it either. I'll try and watch for that.

 

[totalloser]

Had to ponder your point of effusivity, but I think I know why it still works. Consider- the surface area of the media is absolutely enormous comparatively, and the depth of penetration to conduct this heat is extremely shallow (tiny little beads). Pretty easy to overcome the property differences by massive volume and surface area compared to the brass.

But that might be a reason that little cups around the studs on your hot plate method might not work. This ratio would be hugely diminished with a little thimble full of bead media. Enough so that the 32:1 ratio would be in the same order of magnitude mass for mass. IE 32 parts media to 1 part brass contact.

 

[JeepHammer]

High temp fiber material comes in about shape you can think of, square blocks, round bars, sheets, flat strips. I use a lot of it, as easy to work as hardwood.

There is glass mat you can shape, then add heat proof resin to, I've seen it but never used it.

Don't think I'd like to try and manage loose brass with them, but the anti-burn gloves like fast food workers wear around deep fryers would work if you brass was in stripper clips or some kind of jig...

Stripper clips loosen up, I thought they might be easy to load/unload.
Stripper clips have been around since the bolt action rifle and you might have to look around a little, but they are available for about every size case...
And if you can't find your size, they are pretty easy to make, just rolled tin.

Since the small pot seems to burn you a lot...
*IF* you were to expand this some, the heating rod/bar heating element from electric oven, deep fryer, and the oven/deep fryer current controller would allow you to scale this up.
The stripper clips/fixture with long rows (plural) would allow you to drop several dozen at a time.

Since brass doesn't need to be quenched/cooled, once loaded in fixture, heat them and just set the rack aside, do another rack, set it aside...
Since we all handle brass during processing, just rack them when you are already handling them, stopping an extra step.