Annealing with lead - process?

[tlk]

OK, I got updates...

Below 650 is no-man's land. The lead DOES cools substanially when you put a case in it, and below 650 I am finding that the lead has a tendency to solidify inside of the case (30 cal). I am thinking that it is doing this because there is enough space for the lead to cool inside of the case AND not reheat to melting temp inside at below this temperaure (i.e., the brass is insulating the lead inside the case from the hotter molten lead on the outside). Dunno if it will happen with smaller volumed cases, but it is something to be aware of and avoid. I have 9 fire formed and stress-relieved cases that I have to drill lead plugs out of, and that sucks. So the recommendation for a full pot of lead to keep the heat consistent has now been tested and found to be sound (duh).

Second, the anneal lines are the opposite of what we are used to seeing - the brass is shinier where it was dipped in the lead. I am susepcting that the oil is doing its thing and causing this. It proved to be fairly handy as I could get a firm guage on how deep each case was dipped, which greatly helped consistency.

On my 30-06 cases I dipped about 1/8" or so past the shoulder for 20 seconds (used a stopwatch). NO lead adhered to the brass. Temp was 709 - 650. Those that went below temp or were rushed in some way got lead plugs. I have bumped the shoulders and neck sized - the tension is back to where it needs to be so far and NONE of the cases were overdone. So far, so good. Will finish up some prep tonight hopefully and seat bullets tomorrow. So far though, they are better than they were than when we started (6x fired, never been annealed/stress relieved).

This is somewhat of a time consuming process, but I am also able to identify the values/ value ranges where things need to be, record them and repeat/tweak them.

So there you go, FWIW.

 

[Loner]

I think some reading needs to be done. 650 Degrees for a few seconds will not anneal
brass. Here's one article but you can find this information all over the net on educational,
scientific and industrial websites.


Cartridge case annealing. Properties of cartridge cases & factors affecting the annealing process, how & why of brass annealing

Here is an excerpt.


The critical time and temperature at which the grain structure reforms into something suitable for case necks is 662 degrees (F) for some 15 minutes. A higher temperature, say from 750 to 800 degrees, will do the same job in a few seconds. If brass is allowed to reach temperatures higher than this (regardless of the time), it will be made irretrievably and irrevocably too soft. Brass will begin to glow a faint orange at about 950 degrees (F). Even if the heating is stopped at a couple of hundred degrees below this temperature, the damage has been done -- it will be too soft. From this discussion we can see that there are four considerations concerning time and temperature:

1> Due to conduction, the amount of heat necessary to sufficiently anneal the case neck is great enough to ruin the rest of the case.
2> If the case necks are exposed to heat for a sufficient period of time, a lower temperature can be used.
3> The longer the case necks are exposed to heat, the greater the possibility that too much heat will be conducted into the body and head, thereby ruining the cases.
4> The higher the temperature, the less time the case necks will be exposed to heat, and there will be insufficient time for heat to be conducted into the body and head.
You can see that there are a couple of catch-22's involved in this annealing business. On the one hand, the brass conducts heat quite rapidly, and a fairly high temperature with sufficient time must be attained to do the job. On the other hand, too much time cancels the effect, and we will be left with a case that is too soft and not suitable for anything but scrap. Obviously, there must be a solution; otherwise, not even the cartridge manufacturers could get the job done.


If you read the full text on the link you will see his testing method. I just use my calipers and grip them right over the case neck and squeeze the .002 to .003
and watch my springback. No visegrips used.

 

[Mikecr]

I think some reading needs to be done. 650 Degrees for a few seconds will not anneal brass. .

This is true, and as pointed out in the article, we do not ever desire to 'anneal', but to attain "something suitable for case necks".
And my assertion all along is that we should not ANNEAL, but STRESS RELIEVE our cases.

Also, much in this article can be taken as experienced use with torches. It is conceded that there is ZERO lead dipping experience or testing done here.
I assure you, it takes little time to bring brass in contact(inside & out) with lead, to it's temperature. And given that this temp is lower than a typical flamepoint, sufficient timing is easily achieved with less risk(and profit forfeited).

And lastly, the 15min at 662deg appears stated without basis. Perhaps this was worked out using torches.. Same with +750 for a few seconds..
Our discussion here is leading to that needed with lead dipping.

 

[Loner]

I have no doubt that lead is a more consistent process. But temp. and time are clearly
understood by all in the metals industry. 45 seconds at 650 is giving you very little
annealing. And the time at 750 to 800 is 6 seconds to anneal case brass. A near
pitch black room, when it first glows maroon it is done. An IR will not work on clean
brass either, it has such a low emissivity that even most adjustable guns won't go
low enough to measure it. Dirty brass (oxidized) they will measure, but oxidized brass
is as hard as iron (literally) so who would want that in their chamber.

 

[Mikecr]

I'm glad you've joined the discussion Loner, and I'm not discounting what you're suggesting.

It may be beneficial to go a little higher in temps than I have. Maybe my temps used only SEEMED to work..
I'll need to do more testing of the resulting 'softening'. Shouldn't be too difficult.
This is a source I picked up somewhere way back, that doesn't really conflict with anything. But it does not mention times at temperature unfortunately.

 

[Loner]

You're temps are working some. It would seem from the charts you posted and the
general consensus of 750-800 for 6 seconds that we are looking for 100 or so in the
HRH hardness scale. I spin mine and heat with a single torch so I am more concerned
with over annealing. I use the spring back test. You can tell a lot as to how much
you have softened the brass with a hand crank trimmer. Hardened cases will even
squeak sometimes in my trimmer. Annealed I have to be careful on how much pressure
so the cutter doesn't tear the brass as it bites in.

 

[tlk]

Oooooooh, graphs.......me likey.......

OK, so this breeds a series of relevant questions (to me):

1. Mike's first chart is using C26000 alloy as the test - is that what current brass is, and is it consistent across all manufacturers? If not, can this chart be reliably used as a "generally specific" guideline?

2. Loner - where are you getting the 100 in hardness as the ideal to get to for a cartridge?

3. How can hardness of a case mouth be reliably measured at the bench? This one data element would probably help out in a great way with what we are doing here.

4. Can fired hardened brass be brought back to its original hardness?

5. Why does brass have to be brought back to its original hardness? Can't something along the scale work as long as it is consistent between cases AND grips the bullet? Because....when I take Mike's first graph, place in 650, 700, and 750 degrees it shows a hardness for each one of ~105, ~103, ~102 respectively. 800 is showing a hardness of 100. Honestly, how much diffference is there between a hardness of 102 and 103 (which is 50 degrees F). For that matter, what is the difference between that and 100? Is it really material? Do we even know?

If we can use this graph as a general guideline, it is trying to tell us something about the temp range we are working at, people! The slope (rate of change) of the hardness reduction is conveniently levelling out around the temps just past 650 - AND the hardness values are so close together within those ranges I wonder if we are making a mountain out of a molehill. Seems to me we could set the temp range for between 700 and 750, dip away and be pretty damned consistent (within 2 points of hardness).

Facts men, we need FACTS!!

Mike, thanks for the graphs.

 

[Mikecr]

Great things to wonder about...
But some yet to be measured, quantified, and set as standards for reloading.

I'm kickin around a [Pounds to recoverable yield, using a calibrated loadcell, installed in a mini-vise] type idea. I have a truckload of brass suited for testing.
But it'll take awhile to invent & I'm a very busy person...

 

[tlk]

Some of point #5, maybe - and #1 (proprietary). The rest should be answerable. Data points are being handed out and its a good thing. But where does this data come from, and is it valid for our purposes here is the question I have. Data without valid backup can cause bad results - and my Lapua brass aint cheap.

Your graph is a piece of information that is fairly high yield. BTW, it also shows why the 450 degree tempilaq is useful.


Are the other questions answerable by folks on this site? Dunno. I hope so.

 

[tlk]

Mike, what is the second set of graphs supposed to show? That there is really no point in going above 700 F? If so, that is what the first graph shows as well if you plug in the temps and hardness values, at least to me: 707F is the intersection of tensile strength and ductility (with tensile strength falling off rapidly thereafter), and ~700F is carrying a hardness value of about 103.

Appears that 700F is a balance point. Need more light.


Thanks.

 

[tlk]

OK Folks - I got some updates and DATA:

The Setup: I had 50 rounds of Lapua 30-06 brass that had been shot 10 times, had been annealed once and was in need to re-annealing. Like in a bad way. My last attempt at lead annealing worked OK, but I didn;t have a thermometer to keep everything in a tight range between brass and didn't use near enough lead to keep temperature variability to a minimum as the lead cooled inside of several pieces of brass inside the case body, making lead removal impossible and ruining several good cases.

The New Way: I bought a Lyman thermometer, stuck my pot on high and temped it. It pegged at 750 and dipped to 725 before turning on again. Based on the graphs that were provided earlier in this thread I decided that that temperature range would yield little in the way of variability in annealing differences between the brass. Basically higher than what Mike does but lower than Loner. And based on another thread elsewhere around here, about 300 degrees higher than others.

The overall process is was as Mike described, with the following differences:

1. temp was 725-750, trying to keep the dips at the higher portion of that range.
2. dip time was 20 seconds, longer than previously discussed.
3. dip depth was to the shoulder only - no dips past the neck, as the shoulder was going to get hot enough 20 seconds in to get the job done and the risk of lead turds in my brass was minimized.

Keep in mind too that the necks were trimmed to .014" thickness - all brass was uniform.

What came of this? Here are the post-shot results of the first four (only ones I have shot yet), 2880 fps:

The shot string had very little verticle, which is telling me that the velocity is also fairly constant between the brass. After annealing, the brass was cleaned and reasized. Case neck id was tested with a pin guage to ensure .306 before loading (i.e., tension was consistent), and bullets were measured for identical bearing surfaces; this was done to see what the results would be of brass that was annealed in this fashion.



The powder line is uniform across the necks, ending about 1/8" before the shoulder. This is exactly what I wanted, as this brass was beginning to have powders marks creep onto the shoulder. I think this uniformity is a function of both the identical thickness and paying close attention to the temperature range between cases. So it does seem that 750 degrees will not ruin a case and appears to do a fine job of annealing, even at an extreme of 20 seconds.

Hopefully this sheds some light on this process. Any helpful comments/advice that would make this better is very welcome. BTW - wear protective clothing and masks (just to be safe) !!

Thanks.

 

[Mikecr]

Thanks for the follow-up info TLK
I don't see how it can get more consistent, than you are doing here.

Now, could you picture a torch application being so precise?
I can't,, no way..

 

[DoubleUP]

MikeCr, you have certainly done a lot of work on using lead and obviously have given it lots of thought and effort. I think my basic rationale here is it seems to be a tremendous amount of effort for a very slow process. If I'm reading you right a total of about one minute per case is the best you can do. Maybe I misunderstood?

Even using a propone torch and drill, I can do about 8-10 cases per minute and they turn out very good and uniform. Thanks for the detailed explanations on how you arrived at your process. You really have been patient in answering questions, and since I am new here I appreciate it when folks take the time to explain what they are doing while using respect for one another.

 

[Mikecr]

I couldn't suggest that lead dipping is an easier or quicker process.
No, it's a PITA..
But it does work, and really well.

Many in reloading challenge themselves to gain a nickel, if it cost a quarter!
I'm just Happy that I'm not the only one