Annealing with Hot Sand?

[JeepHammer]

BBs *Might* be too big, air gaps. The smaller the media, the tighter it packs and the more mass you get against the case. Smaller shot will get INTO smaller case necks, heated media IN the necks.
That's why I want to try shot peening media, I have some, it's real small (probably 10 or 12) and it doesn't rust when thrown by the peening machine, don't know how it will hold up against repeated 700*F - 1,200*F heating... That's why I say 'Try' instead of 'Use'.

Copper plated shot comes in a bunch of sizes, but BB is the cheapest/easiest by far. (Can anyone say 'Daisy'!)
I get the idea of thermal transfer, and you are correct, the faster it will conduct the better.
The issue is, the mass is hot, you are no longer trying to get heat into it, the brass will suck heat up since it's brass (70% copper), I'd have to try it to find out which works faster.

The smaller shot peening media gets into really small holes and cleans them up....
I have a crap ton of 'Bead blasting' shot so I'm trying to figure out how to clean out the lead pot or get another one...

Im trying to dig out the lower powered unit induction unit that heats steel really well but didn't heat brass well, with steel or stainless steel shot it should work like a lead pot.
Really low energy input and it will heat steel media in a crucible (I found the crucible! Which gave me the idea) and see how that works...

I'm REALLY excited about this! The more I think about it the better an idea it seems.
Crucible & low power (China surplus) induction unit, steel shot would be dirt cheap and real hard to screw up.
Scaling up with electrical resistance, common electrical stove heating elements & controls, same with deep fryer, will make great heat sources and cheap to free...

A longer unit would allow for a long rail doing several brass at a time making spacing between brass easy. The rail allows for all brass to hit the media at the same time, and a couple stops front & rear get the brass in the media correctly.
Rail makes for pulling out of the media (timing) easy as pie.

We are talking wood here since the rail isn't hitting the hot media and won't be over the heat for more than a few seconds.
Something like aluminum foil, old aluminum cans, home siding flashing etc can be used for a heat sink in the rail as a heat sink to keep case sides from overheating, simply clamp cases by their sides instead of trying to hold head/extraction grooves.

I had the idea of stripper clips since several will stick to a magnet.
Magnet on a handle and the production goes WAY up without burned fingers, handle being made to act as depth stop taking another issue out of the process.

The longer I think about this, the more possibilities I see. Electrical resistance heating has been around almost as long as harnessed electricity, so the heater is easy, free if you have a lead pot or electric stove, shot container could be a clay flower pot for crying out loud!
I don't recommend a flower pot for a crucible, but it's possible.
From 'Low Tech' sand, all the way up through a ton of materials for media.

If you do use sand, pea gravel, ceramic, I suggest heating that stuff OUTSIDE, and stay away from it until it's fully hot. If it retains ANY water, steam expansion can make anything from pops to outright explosions, throwing fragments and hot media all over...
If you have never seen a steam explosion, it's impressive so do it at a distance!

Going to the machine gun shoot on Sat, supposed to rain or snow sun. so I'm going to look for 'Stuff' for this on Sunday.

[JeepHammer]

I tried heat treating with salts, BE CAREFUL!

[hounddawg]

Good luck with the experiments Jeep, I am sure you will get it figured out. A watt meter is all you need to tell you what is the most efficient media. But I will say this, conduction and convection are not the only methods of heat transfer. When you get in operation you will have to do a thread with pics

[NWPilgrim]

Anyone have a picture of what a dipping jig would look like? I am having trouble imagining something that allows quick loading and unloading of cases but holds them firmly enough to push into sand or other media.

Also, why not heat the media to a much higher temp? My understanding is the faster the heat transfer happens the less heat makes it down the case body. Maybe heat the media to 1,000F?

Very interested in this idea, thanks for the inventive discussion!

[JeepHammer]

I don't know about sand, but shot (round balls) allow VERY easy access.
I've dropped parts from just a couple inches just to have them disappear.
Balls never pack down, don't have sharp edges.

[hounddawg]

Anyone have a picture of what a dipping jig would look like

Since Jeep brought up the stripper clip idea I am picturing something along the lines of a piece of T track fabricated from strip aluminum which could be slid down end posts at each end of the pot with a adjustable positive stop for the strips holding the cases. you could design it around a lead pot or scavenge some straight heating elements and make a series of long narrow insulated pans

[RC20]

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.

That would be wrong, 750 for a short time, 800 would be close to immediately.

[RC20]

One reason I totally discount lead is that its horribly dangerous stuff (in a lot of ways, vapors included)

I have poured bullets with it, its a focused operation and in my case we used multiple chambers to get as many bullets out of each pouring as we could.

Trying to dip 500 or 600 cases of brass into that, maintain concentration and not screw up and get lead on you, ergh.

[Unclenick]

Originally Posted by hounddawg

BTW heat always flows from the hotter to the colder object and the greater the delta T the faster the transfer

Yep. It’s energy flowing from high to lower concentrations and with it, the potential to move heat. It’s also the mechanism of entropy as described by the second law of thermodynamics. I have eleven issued patents in applied heat transfer thermodynamics, so this stuff is how I made my living for about 20 years. I'm still on the ASTM C16 committee (thermal insulation) contributing to creating standards.


Totalloser,

You're talking yourself into believing in a mechanism that isn't there and have happened upon a parallel that doesn’t actually work out. The sand grains have air between them and those spaces are too small for natural convection to occur in them. In that condition, air is actually a slightly better insulator than XPS (extruded polystyrene foam board; the blue and pink insulation boards you buy in Lowes or Home Depot). So, what will happen is the sand grains will have insulation around them and only pass heat easily through the relatively small areas of contact along edges and points and ends of grains that touch each other or the object being heated. But even if you moved to solid contact using fused silica, it only increases the conductivity by a factor of 2.8, and that imposes the conductivity limit you approach as contact is improved. Even with fused silica conductivity is still 143 times poorer than cartridge brass.

You are correct that you can be burned on your fingers by a hot board, but that's because your fingers are not great heat conductors either and have much less different thermal effusivity from the wood than brass does from sand. Heat, therefore, doesn't flow into your fingers fast enough to drop the temperature at the board surface enough to prevent a burn. I went through these calculations just last year to help a fellow create a standard for hard plastic drain and hot water pipe covers that are required under commercial sinks to protect the legs of people in wheelchairs from burns. So I have the thermal properties of the epidermis handy and will show you.

The Wikipedia article on thermal effusivity has the formula for calculating interface temperature using the temperatures of two materials and their thermal effusivity. It is for the steady state between two practically infinitely large samples, but it still gives you a pretty good sense of the kinds of differences you are up against.

T1 is the first material temperature
e1 is the first material thermal effusivity.
T2 is the second material temperature
e2 is the second material thermal effusivity.

Tm is the temperature where the two materials make contact:

Tm = T1+(T2-T1)e2/(e2+e1)

Where:
T1 the skin temperature is 98.6°F
e1 is skin thermal effusivity of 948 J/m²Ks⁰·⁵.

and,

T2 is the wood (white pine) temperature of 450°F
e2 is wood thermal effusivity of 383 J/m²Ks⁰·⁵.

(Note that even though the effusivity is in metric units, it doesn’t matter what scales the temperatures use as long as they are consistent.)

The magnitude of the interface temperature value converged on will be:

98.6°+(450°-98.6°)×383/(383+948) = 199.7°

199.7°F is hot enough to scald you pretty badly. But if we take brass and sand values:

Where:
T1 the brass temperature is 75°F
e1 is brass thermal effusivity of 19,592 J/m²Ks⁰·⁵.

and,

T2 is the sand temperature of 750°F
e2 is sand thermal effusivity of 619 J/m²Ks⁰·⁵.

The magnitude of the interface temperature value converged toward until the brass heat capacity is caught up will be:

75+(750-75)×619/(619+19592) = 95.7

95.7°F up from 75°F is not very much.

In real life, the brass not being infinite will mean the surface temperature dips and then rises again, but Tm calculations at least give a sense of the magnitude of the problem you are attacking as compared to heating skin.

[RC20]

Who says you can't get a PHD on a Gun Board, phewweee. Impressive.

If you do use sand, pea gravel, ceramic, I suggest heating that stuff OUTSIDE, and stay away from it until it's fully hot. If it retains ANY water, steam expansion can make anything from pops to outright explosions, throwing fragments and hot media all over...
If you have never seen a steam explosion, it's impressive so do it at a distance!

We had a camp fire rock blow one time, good thing no one was hurt.

If you want to see what 50 gallon water heater can do, there was a school in Oklahoma that had a botched safety put in it.

Entirely took out the corner class room (and killed some kids sadly). 2500 some dies after the Civil War when an overheated boiler went and took down the ship.

Unclenick will have the rough ration of pounds of TNT to a gallon of water flashing to steam, it pretty shocking.

[JeepHammer]

I saw the results of a rock chimney explosion, people thought it was a bomb but no explosive residue or parts could be found. Blew the mantle off the fireplace across the room and a hole in the wall big enough to step through.
EOD called in to look for other 'Devices' & clear the area for crime scene techs.
Lesson, don't let an 'Artistic' type build your fireplace!

I've seen small fire ring rocks 'Pop' but never explode. Don't want to be around if they do!

Virtually all sand is washed, so dry it carefully!
I don't need pieces of rock sharper than any kind flying at my eyes!
I've had refractory brick in the forges/furnaces pop/crack/blow apart. The manufacturer said it was most likely stored outside and rain allowed to soak it.
Some refractory cement is supposed to dry for 6 months before it's fired, and firing temps are supposed to increase gradually before the cement is fully 'Cured' for full temp use.

If I were to use 'Glass' media, I would heat it away from anything that could be damaged before I tried to anneal around it. Simply safety just in case anything decided to 'Pop' and throw hot/sharp stuff at me.
Glass has 'Thermal Shock' issues.

I'm connected to Mr. Murphy at the hip, if it can go wrong, it will go wrong, and it will go wrong when I'm in the line of fire!
Physics: Nothing happens until something MOVES, and that means heat energy too!

I'm thinking smaller round 'Shot' media since there is less air space between smaller balls, and smaller balls will get into the necks better.

As for what a brass fixture would look like, for the little round pot (to keep hands out of the burn zone),
A round clam shell with hinge.
Drop brass in lower with holes for brass, close clamshell top.
This would be super simple for rimmed rounds, drop them in, close the clamshell, annealing, open clamshell & dump out.

For rimless, there would need to be some sort of stop. A sheet metal 'Finger' to catch the extraction groove, that's why I suggested a stripper clip which would hold the brass by the groove.

There is also the round hole with slots to make 'Finger', push the brass in until the 'Fingers' catch the groove, then when done just push ahead through. (Push Nut)
This is as easy as an undersized hole, snip 3 or 4 place from inside hole into sheet metal for 'Fingers', and the clamshell could have 'Pins' or 'Pegs' to push brass ahead through when done.
Holes spaced on a paddle would keep spacing between brass, sheet metal on paddle.

When I say 'Sheet Metal', I mean aluminum can. I would darn sure start with something cheap to prove concept.

This is assuming you wanted to use a handle to keep fingers out of danger range...
Loading/unloading a fixture/handle would slow things down, so is your hide worth the extra time?

This will have to be an Up/Down operation.
Dragging brass through a heated media will allow the media to build up on the forward side, have a groove that doesn't make contact as high on the back side.
Dragging would also make a groove in the media making for mixed results.

An up/down rail would be the same idea for a longer media bed for higher production rates.
We have all seen loading blocks with holes for brass, with rimmed rounds, simply a cover to keep brass from backing out (clamshell).

With rimless rounds, some sort of spring to catch the groove and some sort of peg/pin board to punch the brass past the spring, or a stripper clip arrangement that is loose enough to simply allow shaking the brass out of the rails.

We all inspect brass out of the cleaner, so when sorting you simply put the brass in the fixture for annealing before sizing.
I haven't figured out how to get a common case feeder to turn brass over for automated loading of fixtures, and even if I did, Mr. Morris would figure out a way to do it 10 times more efficiently!

[totalloser]

Okay, let me be clear:

This does work. Simple as that.

All the theory in the world doesn't change that unless I'm lying. Which is exceedingly easy to determine, with some cheap or maybe free sand or bead media, and a melting pot that some folks may just have laying around. Understanding the process through theory? Seems useful- but I am running into quite a bit of skepticism based on theory which I have seen disproven in practice.

In short, I'm not interested in arguing- if that's where this is going. I am merely trying to reason out why it works based on empirical evidence I have observed, and a fairly complex number of physics factors in play.

As far as fixturing and such? I fiddled with it and decided it wasn't worth it. I am enjoying entertaining other processes, because who knows? Other problems might be solved or a better process might result. I have burnt fingers here and there as I have during a casting session. Raising the level of the media helped a lot, making a high temp insulated shield render this irrelevant.

What I have *not* worked out, is best processes. My goal was minimum annealing to allow me to size overworked brass. Most folks who anneal have different goals which will require higher dwell, and perhaps slightly higher temperatures and most likely a proper immersion probe.

I do apologize for my faux paux posting my new doodad. If it's gonna be a problem, I have other hobbies I can pursue.

[Unclenick]

No, no! This stuff is interesting. It's only trying things out that get us progress.

The theory only illustrates that your explanation didn't work out for sand and brass, not that it isn't working. You said yourself the blast media worked better and I haven't acquired properties for it at this point. I also pointed out the brass is nowhere near infinite in thickness, so you'll see a temperature drop followed by a rise. The only thing we haven't resolved is the timing of that and where it will land with convection off the case sinking some of the heat. That will produce a temperature gradient that gets warmer toward the case mouth, but, again, we haven't analyzed how much.

How long are you leaving the cases in the hot media?
How are you testing to show the annealing is complete?

[hounddawg]

aluminum oxide (Al2 O3) blast media has a high thermal conductivity. It would be a great medium and is cheap at about 2 dollars a pound in 25 lb buckets

[RC20]

Nope, full fledge admiration.

Bunch of geeks trying to explain it and understand it can sound like a cat fight though.

[HiBC]

I'm not actually doing any of this work,and I'm going to suggest something that may not work,...its just brainstorming.I have not tried any of it. I don't have an induction hot plate.
My idea might trigger someone elses better idea.
Small induction hot plates for cooking use are available for reasonable prices.
They heat ferrous metal pans well.
A cast iron fry pan would qualify.
I'm guessing a very fine grade of steel shot peen shot would also be heated if it was in the fry pan.
I'm not knocking the lead pot idea,but lead pot configuration suggests media depth far greater than necessary. A 4 in deep pot of media brings its own problems.
Why not go with ,say,1/2 in or so of the steel shot media depth? Use the bottom of the fry pan for a depth stop.
Media temp could be monitored with one of those $60 infa red non contact thermometers.
An occasional pan shake would level the media.

Like I said,its just brainstorming. Never tried it.

[Longshot4]

I like the way you think HiBC. So instead of a iron plate why not find the right diameter round steel stock 6''-12" cut a thick slice off to what works well for timing and to hold heat might be 2-3"... thick. bore out to depth for steal shot media and put it on a spindle. Turn it slowly until you reach the temp you find that will hold constant... propane should be good for heat.
Am I off track?

[hounddawg]

I don't think you can get the temp control fine enough with propane and the typical induction consumer hotplate has a temp range of less than 500 F

a $30 dollar lead pot is still the best option for the average home hobbyist. If you want to go north of one hundred that RCBS unit with the digital thermo and plus/minus 10F is tailor made for it

[Ledslnger]

Originally Posted by JeepHammer

I tried heat treating with salts, BE CAREFUL!

JH, besides keeping water away from the salt setup what else if anything should I watch out for? Lmk, appreciate your time. Thx!!

[HiBC]

Am I off track?

(Longshot)

I couldn't say.Its your track.

I agree a lead pot is a practical component that can be easily purchased.It will make the heat and it has temp control.
I'm not at all critical of that idea.I'm not raining on the parade.
I have used sand on a lab hot plate to draw back torch hardened small steel parts. A lead pot is a better idea.

My input was an attempt to address both the fixturing of the brass for depth control and the limited thermal conductivity of sand.Fine steel shot peen shot is more conductive.
The heating elements are in the bottom and/or sides of the pot.Liquid lead will conduct/distribute that heat a few inches easily.Sand,less so. I see no advantage in sending the heat through two or three inches of sand that is not really part of the process.The extra sand is there because the pot is designed for capacity to cast bullets.
The extra depth of sand is a compromise to make the lead pot work.
IMO,with a conductive,loose flowing round shot media,the media does not need to be deeper than deep enough.The bottom of the vessel,or a false bottom,can be the depth stop,assuming the shot will self level reasonably well.

With proper media depth and temp control,fixturing might be a welder's glove.

As far as how the pot is fabricated....If you choose to start with a large billet of steel and lathe turn a vessel,that can work...I'm lazier than that.
A flea market cast iron pan (even a warped or pitted one) would do.

Once again,this is all just thought. I'm not actually doing any of it. I'm the peanut gallery.
Full kudos and support for the OP who IS actually doing it.

[hounddawg]

Full kudos and support for the OP who IS actually doing it.

Have to correct this. The OP(me) is not doing this , at the moment at least. I am perfectly happy with my Anealeeze. I annealed about one hundred .260 cases with it this morning in about 30 minutes give or take

I may try this later on this year depending on the weather and my boredom factor but at the moment I have neither the time or the inclination. I just threw the idea out during a 3 beer brainstorm to see if anyone wanted to jump on it and refine it past the what if stage

[Ledslnger]

You could always try fracking sand as media. It is basically round, that’s why they use it for fracking.

[Bill DeShivs]

How would you keep lead from "soldering" itself to the brass?

[Unclenick]

The usual instructions have you dip the case into graphite powder before the hot lead to prevent soldering.

[rodfac]

How would you keep lead from "soldering" itself to the brass?

I use the lead pot method for all my .204 Ruger to .222 Magnum case conversions/annealing, and have never had any 'soldering problems'. Since this is just a minor 'neck up' case forming operation, I fire form first, then anneal. I think the carbon residue from that first firing, prevents any lead sticking to the brass. Incidentally, I leave the fired primer in place to prevent lead rising inside the case neck. Also, when I first started using the pot for annealing, I lightly wiped the inside and out side with an old gun cleaning rag...CLP on it...and had no problems with splashing molten lead...later, I dispensed with the oil treatment as it wasn't necessary.

When making .25-20 cases from .32-20, I use new brass, and do not anneal until I've fire formed. I have used a propane torch on occasion, but limit it's use to a 2-3 second twirl in the 1" flame. In this case I suspect that real annealing is not accomplished...I fire form next then go back to the lead pot method for subsequent annealings (every 4-5 shots).

Just one more shout out for safety...I wear a complete face mask and my impact resistant glasses, a very heavy shirt, buttoned to the neck, and also buttoned over leather work gloves. I have never had a visit from the "tinsel fairy", and will take all precautions to prevent a splash incident. I'm not annealing thousands of rounds, just 40-50 at a time and only in those two calibers; and I feel that the short time it takes me to process that many, allows me to maintain the concentration absolutely necessary to prevent accidents. It's molten lead, doncha know!!!

HTH's Rod