annealing with moltenlead

[Unclenick]

The candle and lead methods both are things I first saw in metallurgist Fred Barker's article in Precision Shooting Magazine.

(1) Lead Pot Method: heat lead to 725°-750°F; dip neck into powdered graphite and then holding body of case in fingertips into molten lead: when case body becomes too hot to hold slap case into wet towel; or

(2) Candle-flame method: Hold case body in fingertips, place case neck in flame and twirl case back & forth until case body is too hot to hold, then slap case into wet towel; wipe soot off neck & shoulder with dry paper towel or 0000 steel wool.

Fred Barker, Precision Shooting Magazine (RIP), July 1996, pp. 90-92

The graphite prevents the lead from soldering to the brass. The wet towel chills the case so the heat won't spread to the head, but that would only be a potential issue with short cases. I once trapped a thermocouple in the primer pocket of a 30-06 case with the end of a wood dowel, then heated the neck with the burner flame from my gas stove. I kept it in the fire a long time, rolling the dowel back and forth between my fingers, but air convection was removing heat below the shoulder fast enough that I never saw the head get warm enough to stress-relieve it in less than several hours.

It needs to be understood that annealing actually has three stages: recovery, recrystallization, and grain growth. The candle flame or lead pot methods generally only accomplish the first stage, getting atoms dislocated from the crystal lattices back in place. This is generally just fine to prevent neck splits in cases that are not being reformed. However, reforming may require further softening because it will work the brass harder, introducing new dislocations and grain boundary slipping in the process. If you have identified the need to further anneal brass, then the question becomes, how much time at what temperatures do you need to get to that softer state without starting grain growth (which reduced the strength of the brass)? There isn't one right answer. The reason is that the higher the existing stress in the brass, the lower the combination of time and temperature required to initiate recrystallization. A piece of 50% work-hardened brass can take nearly ten times longer to start recrystallizing at a given temperature than a 75% hard piece of brass does. Given neck splits occur on firing, for which the total linear stretch is small, and given that % elongation at break decreases with hardness, it is likely the brass in the neck is well over 90% work hardened when that happens, which means it would anneal quickly at a comparatively modest temperature, making it easy to oversoften. It also means that applying just enough time and heat to soften 90%+ work-hardened brass may do nothing to a piece of brass that has only been fired once and isn't yet very hard. This brings into question whether the various annealing machines that are supposed to anneal brass to the same degree each time you fire them can really do that if the brass doesn't all have an identical loading and firing history, and even if it does, it may do nothing to any of the brass until is has gone through enough load cycles to get fairly hard. In other words, brass annealed at every load cycle may simply go up through a series of hardening steps at each load cycle, getting harder and harder and then suddenly drop back to a softer state when it finally got hard enough for the annealing time and temperature combination to trigger recrystallization. It's really quite a messy business.

The saving grace for brass is it work-hardens quickly. Eric Cortina has a video in which he grossly overheats some brass until a bullet practically falls in but then shows one firing and resizing cycle gets it hard enough to seem to be working again. However, what I've always heard and that he did not test is that over-annealed brass will need to be annealed again sooner. Norma, for example, tests that their brass can be reloaded and fired at least ten times without splitting. It is part of their standard QC process to pull samples periodically during a run and test that it will tolerate that. I think we've all heard of 308 and other standard cases that have gone 20 reloads without starting to split. However, someone I knew who always annealed by bringing the brass to the start of a red glow (as seen in a darkened room) said he annealed every three to five reloadings to prevent splitting, which would indicate he was overdoing it. This may be due to grain growth. I don't know. Grain growth takes time to occur, and I don't know how fast it goes when you get the brass over 1000°F as the glowing stuff was.

This paper has a lot of information in it if the subject interests you.

[deces]

[vikingsword7]

This is the method I use (salt bath), and it works flawlessly and is extremely consistent!

[imashooter2]

You don’t need a PID or thermocouple for salt bath. It works just fine with the analog thermometer you probably have now. The warning about overheating the salt is valid, but I’ll point out it is a long way to get 850° salt to over 1,000° in an electric casting furnace. It’s every bit as safe (and as dangerous) as molten lead.

[45workhorse]

The salt bath seems to work good for me. 6mm brass up to 7mm BR.

[vikingsword7]

For those curious about the salt bath technique, Low temp salts are what are used, and I heat mine to around 850 to 900 degrees. I count out 6 to 7 seconds on my 45-70 cases and I do drop them into water, but only to arrest the corrosive effects of the salts.

[3584ELK]

I tried annealing with glass beads and a Lee pot. Total waste of time- the glass beads never got warmer than 580 degrees F in that Lee pot.

Having ordered an E.P. 2.0 annealer, I dont see myself exploring these alternate methods any further.

[HWooldridge]

Oil or not, I would be seriously concerned about molten lead tinning a layer onto a brass case.

[Unclenick]

I've never figured out why salt annealing would be better than molten lead, which has higher thermal conductivity and higher specific heat density resulting in higher thermal diffusivity. In other words, it should heat the brass faster.

If you read all the way through this evaluation of salt annealing by the makers of the AMP device, you see weird annealing differences in different areas. That is due to the effect I mentioned earlier, where an area of the brass that starts out harder anneals faster in uniform temperature exposure. Note that this is likely a problem with lead, too.

Obviously, there is a potential conflict of interest when one annealing process maker reviews another. However, the AMP makers have been doing it a long time and have the test equipment, and I don't have any reason to think they would lie about it when someone else could repeat their experiment. I see that CShooter Solutions, the maker of the salt annealing product, ran his own tests to dispute the notion salt annealing doesn't work, but as he says himself, he doesn't have the right test equipment to challenge the AMP results. He does show neck splitting life delay, but as I mentioned earlier, going through restoration is adequate to accomplish that for simple reloading. The question is whether it will be adequate for reforming cases or not, and that seems less certain. He also shows a reduction in required resizing force. That's the only part that doesn't tally well with the AMP results until they get the exposure out to 20 seconds, at which point the harder part of the shoulder do anneal without the neck changing apreciably. It's a funny business.

[deces]

For $280 I would expect it to have a hopper. That guy is making a killing for how little work he put into making those.

$35