Annealing, Grain Structure

Unclenick,
ALL cartridge brass micrograph samples MUST be ground at some point! PERIOD.
Simply no other way to prepare the sample.
Maybe check some of the text books & instructional videos.

Secondly, not to put too fine a point on this, since your buddy might have misspoken,
We ARE NOT looking into this brass anywhere near the atomic level, not even close!
That would take a super powered electron microscope!

Not even close to atomic level!

This is an ALLOY, we aren't even looking at the molecular level!
Inspection that shows molecular would entirely miss the grain structure, combining of copper with zinc, ect.

We are looking at the chrystals that are BILLIONS of molicules and countless TRILLIONS of atoms.
We are talking the size of some plant cells here, in the 'Micro' world, it's barely 'Micro', and we are looking at hundreds or thousands of chrystals at one time...

Smearing will happen when you don't use enough water when sanding, or you don't keep final polish wet.
This has been pretty well figured out already, by paint guys at the least, they are working with soft poly structure that smears MUCH easier than brass!
Gem stone polishers work with stones that are much softer than brass,
Lense polishers work with polycarbonates that are much softer than brass.

The industral science has already been laid down, I'm just taking advantage of it the exact same way everyone else does...
 
Nitric acid was my fault. I knew it was used in metallographic etching, but didn't realize that was only for steel. BigCheese pointed this out to me in a PM, since his lab used to do that kind of work.

There is no suggesting that we are trying to see atoms. The comment was meant to convey that the final lapping had to remove the material very slowly and had to avoid burnishing. That latter point is the tricky part, as I've read polishes all tend to burnish by smearing a surface some, rather than doing it by material removal alone.

The concern is not that we will fail to get a nice looking picture when grinding by any method, but rather that we may get one that's not representative of the actual grain structure underneath the surface we prepared if that surface has been too aggressively ground and polished. About the only way I can think to test that is to make your own photos and then send the same sample to a test lab and have them do it professionally and see if the the result tells you something different. Perhaps, short of that costly approach, would be to try some different methods of your own on different parts of the brass and see if you get different looking results.
 
While I'm not using a $22,000 microscope and equally expensive camera,
The samples look pretty much the same to an untrained eye.
The brass guy used my quickie samples saying there wasn't enough of a difference to worry about, results were good enough to tell exactly what was going on.

That's why I picked up the way he did quickie samples, because it works.

As for burnishing, that would be the reason for silicone carbide cutting material and a constant flow of water, nice wet sanding really brings up the grain with a good clean cut.
If you don't fuzz up the sample, you don't have to try & fix it.
 
The other thing people ask about is inside the case & outside the case...

Cutting the samples longways, a cut away, reveals both sides of the anneal,
The only time I've seen a difference between inside & outside is when the case is heated REALLY FAST.

The brass does not have time to fully thermally saturate, the outside will show signs of alloy separation & sheering, while the inside shows little help from the heating.

This is usually from me using a super hot flame, oxygen gorged 'Jet' torches.
The zinc starts to separate from the copper, and remember, cartridge brass contains lead, which can surface also.

I don't see this with electrical induction (magnetic) annealing since electrical annealing excites molicules on the atomic level all throughout the brass at the same time.

The biggest issue I (personally) have encountered with electrical annealing is TIME.
Electrical induction annealing CAN be fast enough the chrystals don't have time to form & expand to 'Optimum' for what we are doing.
I've actually had to SLOW the TIME, holding the temprature longer for proper grain structure & chrystal size to form.

That fact alone would explain why long does of gas nozzles & flame was used so successfully for so many years.
Long rows of gas nozzles (NOT super hot jets) would bring the brass up to proper temprature and HOLD it there for the TIME requirement for proper chrystal size & grain structure.

Electrical induction annealing is MUCH more efficient on every level, energy requirement, even energy application to the brass (can't beat even heating on the molecular level!),
And PRECISE time control,
But like everything else, you CAN apply too much too fast...

This would explain why production electrical annealing of cases are done in an OPEN, less efficient annealing coil...
MUCH easier to control time/maximum temprature in a longer, open coil.

I've posted this link before, but consider the TIME AT TEMPRATURE when watching.
Depending on intensity of the magnetic field, time at temprature is greatly increased while still being fairly precisely controlled, giving grain/chrystal size TIME to grow to 'Optimum'.

https://m.youtube.com/watch?v=Ira3dmlclQ4

The higher the energy imparted into the case, the more precisely you have to control time!
With an open row of flame nozzles or an open annealing coil, your exposure time could be +/- a few seconds, while in a concentrated 'Jet' flame or closed/focused induction coil it can be 1/10th or 1/100th second timing critical.

Something for the home annealer to consider...
 
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Now, ASM handbook set is $9,300 and is copyrighted, so according to the forum rules, I can't show you what the book actually shows...
Not even the small graph concerning recrystallization temprature of cartridge brass.

What I can tell you is,
Anyone I've ever seen quote the ASM book (the single best & most complete scientific standard ever written) makes the same MISTAKE every time!

That is the ASM samples tested & graph shown for shows 454*C (848*F) as grain growth temprature reference point...
That's a MISTAKE with firearms 'Cartridge Brass'!!!

The ASM book charts 40% Zinc brass alloy, while the biggest part of firearms cases are 28%-30% Zinc!
Heating to 850*F for any length of time CAN seriously damage the brass for our purposes putting it way outside of the 'Optimum' of what we want.

This was a MAJOR DEAL for me, I 'ASSUMED' ASM quick reference would be 'Correct', but it's NOT for 28% or 30% common firearms cases!
The testing simply didn't pan out, so I had to go back to the books & drawing board,
And it's probably why manufacturers guard their annealing processes so closely...

----

There is a reason people with some idea of what they are doing STRESS 700*F to 800*F,
Even if they don't know the specific reason or not, just find that brass annealed in that range are more consistent and seem to be OPTIMIZED for what we are doing....

Temps between 700*F & 750*F (no more than 800*F) will complete the FIRST of three steps of annealing, the STRESS RELIEF step...

The second step is 'HEALING' or 'RECRYSTALLIZATION'
The point where voids, gaps, stray molicules (dust), and slivers/shards of broken crystals are reabsorbed back into a coherent structure,

This is also the point where the brass becomes 'Soft' and brass Strength starts to weaken.

It's not all bad, DUCTILITY starts to go way up at this same temprature.
That means more consistent case out of your dies! (That 'Optimum' performance thing again...)

The third step in the PROCESS is Grain Growth, expanding grain size, larger grains gobbling up smaller grains...

This is where you very easily overheat the case, creating a MONO-CHRYSTALINE condition.
Mono-chrystaline doesn't mean one big chrystal, it just means the chrystals are getting too large to be useful, way too big for 'Optimum'.

ANY reasonable annealing is 'GOOD' simply because it removes the stresses all the broken shards, voids & stray molicules between grains, fitting them into places AT REST, instead of pulling and pushing every direction imaginable....

The second step, Recovery, allows the grain structure to absorb the stuff that causes stress in the first place, and you will usually get a few load & fire cycles before the case is so stressed again it won't resize consistently.

The third step, Grain Growth, is the most difficult since it has to be PRECISELY controlled,
But when it is precisely controlled, produces a case that is just like brand new (minus a few trace elements lost during heating).

This is NOT an 'Art', or magic, or anything other than science...
If you choose to do the science, you CAN hit 'OPTIMUM'.
If you don't want to do the science, then at least don't screw yourself by looking for 'Color' or 'Glow' from the case,
Use a temp indicator and work on getting the case out of the heat as quickly as that indicator shows the case is 'Done'...
 
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This is how I show what I'm trying to accomplish, showing the different properties of brass, and how they change with temp.

Hardness,
Strength,
Stress Relief,
DUCTILITY/Workability,
And finally Grain Growth.

http://i1298.photobucket.com/albums/ag58/JeepHammer1/IMG_1037_zpsnthgeo1c.jpg

This isn't to any specific scale, it's just to show the factors that change with heating,
And somewhere between verticals bar two & four is the 'Sweet Spot' where most things come into an acceptable range,

From just stress Relief before the case starts to soften very much,
To fully annealed and grain size (growth) starts to increase exponentally.
 
To answer email question,
*IF* you want the wonderful colors in your micrograph, you will need a 'Reagent' (chemical treatment) and a Polarized Filter for your magnifier.

Depending on your initial chemical treatment you will be able to see some colors, the longer you treat the sample the more defined lines between grains become, and the more the grains will stand out.
The -Standard- is,
25ml distilled water, (deionized for scientific grade)
25ml Ammonium hydroxide
10ml 3% Hydrogen Peroxide
You are looking at 3 seconds -Standard- , but up to 5-6 seconds actual time to get really clear lines.

You have to use a FRESH solution on each sample, so CUPS with a little squirt in each one.
If you aren't doing scientific grade samples and just want to see the grain structure, you CAN reuse the solution a few times before it stops working well.

Polarized filters will help those lines & colors show up.

Klemm's III reagent will make colors REALLY stand out & pop!
I have no idea how to backyard engineer Klemm's reagent formulas, someone else might know something that works.
$85 for 250ml so I use it sparingly since I'm a tight wad when it comes to stuff like this.

I do use distilled water, I do NOT use scientific grade deionized water.
Distilled water from the grocery store works just fine.
I use tap water when wet sanding, no sense in using distilled or deionized since I run a total loss (down the drain) instead of trying to filter the water to be used against, just too expensive to filter the larger grit out of the water supply.
The house has a 0.5 micron filter for drinking water, that's close enough...

Polarized filters can be had for about $20 (or less) that work fine with the USB magnifiers, or for just under $100 you can order a 5mp camera with stand & polarized filters.
A good stand is a GREAT thing to have!
 
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JeepHammer said:
The ASM book charts 40% Zinc brass alloy, while the biggest part of firearms cases are 28%-30% Zinc!
Click to expand...

I would put it at more like 20-30%. See this article. Keep in mind this stuff can change over time.

IIRC, the ASM plots are for a one-hour soak of the brass in the temperatures given. You can get a lot of grain growth and stress relief in an hour that doesn't have time to happen at the same temperatures in the few seconds we normally partially anneal cases in. You'd want graphs for numbers running from 2 to 20 seconds heat exposure. I wonder if anybody has ever done them? If not, it may be an opportunity for you to publish some original work.
 
Probably why manufacturers guard annealing secrets.

All I do is short duration, from about 30 seconds to under a second with reloading brass.
I have to hot soak new case manufacture several times during the manufacture, but that isn't home reloading related.

What I see from the factories is a pretty good grain structure in the head of the case, but the necks/shoulders are long, stretched, low angle grains with a bunch of faults.
The entire case is obviously properly annealed (long duration) previous to neck forming, but it's quick annealed, just some stress relief done in the neck/shoulder to enhance sizing control.

Doing hardness testing, then grain inspection yeilds surprises...
Straight walled cases don't have the issues necked down cases do, I have to assume straight walled cases are fully annealed (long duration) and don't need further working so the neck doesn't get stressed/work hardened again.

Something is telling me to keep this proprietary, since the information isn't common knowledge & it's closely guarded by manufacturers, it might actually be worth something...

I was looking for a manufacturers video showing gas annealing with a row of nozzles, but I couldn't find one from a major manufacturer.
Couldn't find a single gas annealer machine manufacturer advertisment, makes me wonder how many places even make gas annealers for cartridge cases anymore?

Not much to see with electrical induction annealing, you can't judge power by looking at the cases change color, but several manufacturers of annealing machines have advertisment videos on the web.
 
WOW!
Read the entire article, and references, and that's an eye opener!
That explains a TON about why Lapua cases anneal so much differently than what I do the most of, milbrass.

The report looks like a short version of what I paid full price for analysis.
I always thought they chemically & gas chromatography analyzed the brass formula...
Looks like they might have done a little X-ray also.
(Doesn't make me feel any better about what I had to pay them!)

I would REALLY like to do that and incorporate it into a spread sheet that included hardness, grain structure.
That would give a GREAT picture of what's needed, and where the limits would be when annealing, that's REALLY a missing piece!

20% spread in zinc content alone makes a HUGE difference in TIME at temprature, and that might be the huge difference I see in grain structure between brands of brass.

I got a new drip pan for my wet grinding table today, zinc plated, so just out of curiosity I had a look at the grain structure.
Don't know why I hadn't done that before since zinc plating is so common, but I hadn't...
Don't know what to make of it yet, but the high zinc grains look like high zinc brass grains, just MUCH larger. You don't even need a magnifier to see the grains...

Thanks again for the link!
I have more investigation to do, maybe even send off some milbrass for composition analysis, but I sure don't want the bills for a 'Hobby' business...
 
The differences in that report explain why the guys making that super expensive ultimate induction annealer feel the need to analyze hardness for every size and make of case to get settings that produce a match. The only question I have: is hardness is really the right measure? Having the same hardness would tend to give you consistent bullet pull across brands, provided all the neck walls were the same thickness, but the same degree of stress relief won't give the same hardness in different brass alloys.

If you outside neck turn all your brass and anneal every reloading cycle, then hardness is probably a good measure for controlling start pressure, though it ignores differences in case capacities, so it's not necessarily a guarantee the exact same loads will be best in all of them. But if you want the maximum number of reloads between annealings, then you want the stress relief optimized and would sort your brass by lot to avoid bullet pull variation and to limit the instances in which you need outside neck turning. But now you're looking at analyzing photomicrographs rather than the easier-to-perform hardness test.

So that's another one for the metallurgists: how close would hardness tend to be in optimally stress-relieved brass of the different alloys mentioned in that article?
 
I personally find,
(Stressing I'm NOT trying to sell this as the 'Ultimate' way to do things)

Having sectioned, hardness tested, then had a look at grain structure,
Having put the same lot through through the dyno to determine what the pressure for movement is,
I can equate hardness to a consistant neck on 2012 and newer Lake City brass,
Mostly because I see LC about 1,000:1 of anything else (like WCC headstaps).

*IF* I had ANY 'Spare Time' I would like to do more testing...
'Spare Time' is like 'Extra Money', I've heard about it, but I've actually never had any, so the concept is abstract to me.

Between the race car job, the solar gigs, my mostly one man machine shop, and keeping up
With the homestead & the NEVER ENDING HONEY DO list, I'm lucky to get time to eat!

The guy with the $1,800, one at a time annealer will hardness test your cases for around $40 each sample, which only tells one part of the story...
A couple one at a time annealer come with a cart for case/caliber types, I have no idea how they determined times.

I will start a spread sheet with as much information as I can glean from reputable sources.
Wonder what X-ray costs over gas cromatograph or chemical testing?
I can do Rockwell & metallography, but I'd SURE like to know precisely what's in the brass to include in a graph/spread sheet database.

Until someone builds an annealer with a built in thermal limiting pyrometer there will never be a comprehensive way to anneal...
 
IIRC, their video showed they use the micro hardness tester to ascertain how long to leave the power on.
Click to expand...

Just speculating but I would think they would do a random sample tests during a run or at the minimum with every new lot of brass ingots
 
The maker of the annealing machine we are discussing makes only that machine, not brass, so they have no runs to sample. The brass manufacturers, though, can do that. I don't know their QC procedure other than Norma mentioned in their manual that they periodically take samples of finished cases and expect them to tolerate being loaded and fired ten times each without splitting at the case mouth.

Getting a brass ingot hardness measurement would not be useful, as the cartridge case forming process changes the hardness of the brass. Also, the factories form cases from either brass sheet rolls or from slugs cut from brass wire, so they don't handle ingots at all. They leave that to sheet and wire makers.
 
Getting a brass ingot hardness measurement would not be useful, as the cartridge case forming process changes the hardness of the brass. Also, the factories form cases from either brass sheet rolls or from slugs cut from brass wire
Click to expand...


good to know but what I was getting at is that their hardness testing would not be a one time thing. Also I was referring to testing the case lots not the raw material
 
The annealing machine maker we are talking about does not make brass or necessarily have lots of it any more than someone who makes case trimmers would. This is just a home handloader's annealing machine, and not a case manufacturer's annealing setup.
 
My Rockwell tester is constantly calibrated, so I know it's up to snuff.
The Dyno is regularly tested, so I know it's up to snuff.
My process for grain samples is passable since ai learned it from an actual brass engineer, does nothing but brass, besides it's just looking at grain structure anyway...

When I did government DOD contracts, the coil was sampled every 4 feet, and samples were taken every step of the process, and it wasn't voluntary.
No records, something not documented and the entire production run was rejected.

I contracted to make 458 Socom brass and the buyer wanted DOD/Areospace documentation, which was a HUGE PITA, but you do what you have to so you get paid...
At least by that time I knew what to expect and knew some shortcuts.

I first got started making 45-120 Sharps brass, a bunch easier when the buyers aren't expecting a NASA mission to hinge on the quality of a black powder brass!
Very low volume and zero profit.

I had to relearn everything when I tried .22 LR rounds, it's a totally different brass alloy and processing method. There is money I'm never getting back...

I'm not a PhD metallurgist that works strictly in brass, so I had to pay (dearly) for one...
I would very much like to find someone with a gas chromatograph or X-ray that could tell me composition of the alloy, I think that would make all the difference in the world for a comprehensive picture of annealing.
Last time I was in the room with a gas chromatograph I was scared to breathe on it, it was upwards of $250,000...
I won't be getting one anytime soon unless I win one of those half billion dollar lotteries!
 
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