DIY Electrical Annealing Of Rifle Cases

Jeep hammer. I did have a gate just large enough to fit a piece of brass in. It did heat up brass very slowly but had no effect on steel. It was black ferrite. I have green on the way.

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Nvreloader,
I can't remember if I posted this before on this forum,
I posted it on an electronics forum a while back.

image_zpsewbwkiqu.jpg


Volts/Amps display, Volt/Amp control, timers for case drop through.
Nice door to keep little fingers from flipping switches, turning knobs, etc.
 
That looks great. Really nice job!

Just got back from NC bringing a friend up to house & dog sit. I did stop in Columbus and picked up the power supply I mentioned earlier. Once we get back from the trip I'll get things setup and see if things work.

Ron
 
I was able to get the 2 hp psu's wired in series for 24.8 volts. The worked quit well. Using a black ferrite core with 4 wraps of 12 gauge solid copper on each side I can heat a 30-06 case to 700 degrees in 15 seconds. I have some green ferrite on the way. I was hoping to get my time down to 1.5 seconds. Do you think switching to green ferrite rather than black will make that large of a difference? If not, what other methods can I use to get my heat time down?

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I honestly can't tell you.
I've experimented with 'Yellow', 'Red', 'Green' and an assortment of 'Not Marked' salvaged ferrite cores.
So far the 'Green' works best somewhere between 36 & 48 volts.

HP power supply modules in series is what I'm using.
There is a crap ton of them surplus since it's what they use for big servers & powering a lot of CNC/Digital controlled stuff.
I think I paid $12 each for mine off EBay, and once an I.T. Buddy saw them he brought me 4 more, the old ones when they updated a main server somewhere.

I'm thinking the 'China' units might not be the 'Right' switching frequancy, the more I read about this stuff.
Most of these things were made for solder melt pots or heating shafts/bearings for interference parts assembly,
And from what I'm reading brass *Might* need a different switching frequency to work at optimum.

I ordered a couple fine tuneable variable resistors to experament with that very thing.
The switching frequency is controlled by a resistor in the circuit, higher or lower value resistor changes the frequency.
This will let me make very slight changes to the resistor value and see if I can burn up another 'China' unit or two! :(

Being able to tune for 'Brass' instead of lead or tin or silver or steel -- *Should* (in theory anyway) let us use less expensive, commonly produced power supplies at lower voltages, bringing costs down and expanding capability & tuning ability...

SO! I'm off to inhale solder fumes in the name of a community project since my resistors came in today...
 
kriss6600,

The original frustration may be due to the core material. You may have got too much inductance from it and choked current flow into the tank circuit too much to get adequate energy from it. The main symptom would be the frequency being detuned too far. That, alone, may prevent it from heating thin metal as well as you want, even when it is coupling energy into it.

You can adjust the inductance down by spreading the coils out over more length of the inductor, reducing the number of turns, or wrapping the core with paper or something to create space between the coil and the ferrite.

The right material should be for your frequency range. It also needs to be thick enough to produce the magnetic flux density you want before it gets too close to saturation. It should not produce a lot of heat loss at your desired frequency.
 
I just checked what my amp draw is and it's 4.55. With the 24.8 volts I'm running that is only 112 watts. I'm wondering if I need to bite the bullet and buy another psu and go up to 36volts. I also took uncle nicks advice and reduced my wraps to 2 per side. The coils were already pretty well spaced. That reduced my time from 15 seconds to 10. It also made the coil itself heat up much faster. I'm curious as to why that is. I'm also curious as to what effect reducing or increasing the size of the wire used in the coil would have on the end result.

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Here is one for you, 'Litz' wire!
That may very well be what I've been missing...

https://en.m.wikipedia.org/wiki/Litz_wire

High frequency AC, which this basically is with the alternating polarity, use 'Litz' wire instead of solid conductor or tubing.
I ran onto a dissertation on induction (heating) with values for 'Litz' wire over solid core conductors.

It never occurred to me we were working with high frequency AC properties (using a DC power supply) so it makes sense to beat surface conduction/skin effect using a bunch of insulated smaller wires would work better than a solid conductor, which works best for DC.

I got some high temp Litz wire on order, something else to consider & test.
 
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Litz wire is often used in the power board but not for the heating coil. The copper tube is used because it has sufficient surface area and it can be cooled.You don't want to use the Litz wire for the heating coil unless you are heating from a flat coil where the coil can be mounted to a heat sink.
 
Shootist,
I've been reading (always dangerous for me!) that Litz wire is often used on low duty cycle (Switched On/Off) units,
The guys using timers to limit the amount of energy the case gets.

The 'One At A Time' guys might benifit from Litz wire, I just don't know yet, haven't messed with it yet. Supposed to be here next week.

The full time (100% duty cycle) guys that use case drop to limit energy into the case would see the wire heating to probably unacceptable temperature and burning the insulation off between strands.

What I have on order is supposed to be 'High Temp' insulation, but didn't give specifics about insulation temp tolerances.
That's the pain with small batch buying, no manufacturers information, you are stuck with whatever the seller posts...
 
Mr. Jeep hammer,
I have a few questions about annealing in general. First how far down the case towards the head is it safe to anneal to? If you were to pick a temperature at which you could safely say that no cartridge brass could be annealed below that temp what would it be. I was thinking 450 f. Basically I am using 750 and 700 tempilaq to make sure that I am hitting 700 degrees but not exceeding 750. But I am getting quite a bit of heat at the head. I want to put another tempilaq stripe on the parts of the case that must not be annealed just to make sure. Also have you had a chance to try the litz wire yet. As always thank you very much for letting me pick your brain.

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450*F is widely reguarded as 'Safe' for lower cases.

Keep in mind that there are folks that say dead soft cases are 'Dangerous', you should NEVER do anything that annealer the bottom of the case...

To this I usually reply,
"Have you Rockwell tested the bottom of factory civilian brass?"
There is always beating around the bush, quoting some arcane article written by an 'Outdoors' writer, then admission they haven't done any direct hardness testing at all...

Factory civilian cases usually come "1/4 Hard", Rockwell B scale of about 70-75, which is what most of the upper cases come in at,
And what most annealing is aiming towards.

As for being 'Unsafe', these same civilian brand new cases don't blow out in unsupported lower rifle chambers, like most semi-auto rifles have.
I'm positive in days past, when steel was questionable at best, a 'Hard', thick walled CASE helped support the chamber, no question about it...

Since most of the TENS OF THOUSANDS of steel alloys have been invented in the past 50 years or so,
And the forming of steel billets used to make barrels & recievers leave few voids, faults that can fail,
The older stories of 'Soft' cases leading to blown up firearms are in our past...

The case blanks, from 'Coins' being punched out of rolls of brass, all the way through the forming process, the brass is annealed AS A WHOLE several times.

The ONLY US manufacturer I'm aware of that produces 'Half Hard' lower cases is the US military production.
Since civilian cases don't have to stand up to machine gun links, get forced into machine gun chambers at a rate of up to 1,000 rounds a minute, rounds getting touched off or cook off before the bolt is in full locked battery, etc., I'm not as worried about lower case softening SLIGHTLY while I'm neck/shoulder annealing as some people are...
And I've never had a blow out, even when fired through machine guns.

When you heat to 'Dead Soft' (as in for forming the case for initial forming) you have to watch for overheating, both to keep alloy components from separating & to keep the brass from going 'Mono-Crystalline', removing the grain structure that allows brass to expand/contract without cracking.

You aren't getting close to that, so I don't see any big issues at all with hitting 700-750*F on the top end and keeping 450*F in the mid case.

With 700*F you aren't quite reaching the 'Full' annealing benifit, but you are annealing and if you are CONSISTANT with your cases they are seeing a very large benifit from annealing.
I'd rather do 700-730*F than overheat the cases,
So you are 5 Rockwell points off 'Optimum', big deal...
CONSISTANT is more important that the 'Perfect' Rockwell reading, and you have removed 80-85% of excessive 'Hardness' from the case at the same time!
 
Update on 'Litz' wire,

A FAST electrical annealer that switches On/Off (timed unit) works outstanding!
Delivers considerably more power to the brass heating it faster, so you will have to watch/adjust your time.

Constantly On units (timing the case exposure to the coil), 'Litz' wire doesn't work at all.
The coil heats up and destroys the insulation between strands of wire.
Looking more like a cooled tube is going to be the only way to do this one.
 
Litz wire is intended to have lower effective resistance than standard wire at high frequencies because it has a lower percentage of copper not carrying current due to skin effect. This raises the Q of coils, or else is used to reduce the wire diameter needed to achieve a given Q. However, that does not change the fact that heat is generated by running current through what resistance it has. And there you have the problem that the insulation around the individual strands interferes badly with their ability to pass heat to one another and out to the surface for air to carry it away. So, you may need smaller gauge litz wire for low resistance and hi Q in a low power coil, but in a high power coil, where heat dissipation is a factor, you have share the current out among a larger number of strands to avoid heat accumulation in the center.
 
You lost me at 'Q'...
Please explain.

This is Very high frequency reversing polarity application.
The reason I tried Litz wire in the first place...
The eBay 'High Temp' insulation on the wire isn't what I'm used to for 'High Temp' applications, doesn't last long (and smells horrendous) when it's heated with continuously 'On' units.

Dropped annealing time on .308 cases a full second with switched power units, implying more power is being applied to the magnetic field and not wasted as Resistance in the conductor/unit.
Using Templiq time dropped to melt the paint from 4.3 seconds with the cheap China unit to 3.1 seconds with no other changes to the unit or power supply.

I'm aware of surface or skin effect with high frequency AC, but since I was working with DC power supply, the polarity flip (AC) didn't enter my addled brain until I read a Stanley Zinn article about frequency response difference between solid inductors & Litz wire conductors, and the light bulb above my head fizzled a dim light on things...

I understand the principals, I just don't have the education to canculate the 'Optimum' arrangement/materials.

Circuit design isn't my chosen field of study, so I'm researching possible materials & options that will work with these $50 induction units...



It's trial & error sometimes, but with collaboration it's SLOWLY making progress...

I put from 'Experts' is always welcome, but not always forthcoming... (hint!)
 
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When my unit turns on the magnetic field tries to kick the brass out of the ferrite core. I find that odd considering that my brass is presumably non-ferrous. Has anyone else had this happen?

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Yes, I have observed the effect myself.
That's why I use a ceramic holder for the brass, and/or insulate the coils with fiberglass wrap.
 
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