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Old June 11, 2017, 04:38 PM   #1
JeepHammer
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Annealing, Grain Structure

This has never been cheaper, although it's not 'Easy'...

The idea is to cut a piece of brass, new in perfect shape from the manufacturer,
From different manufacturers,
And see what the factory is doing to the brass structure for 'Optimum' performance.
You will be surprised at the difference between brass from different manufacturers!

Then cutting & preparing samples of YOUR brass for comparison.
Both fully hard, then annealed to different temperatures & times....

Doing this gives you permanent reference samples.

This will allow you to directly see what you are getting for your efforts compared to what the factory is doing.

You CAN just polish a sample and throw it under magnification, but you won't see much.
Preparation is the key to directly see what's happening.

Now, you aren't preparing samples for NASA or an anal retentive government inspector, so you CAN do this much cheaper with good results!

First off, taking the sample,
You CAN NOT expect good results if you cut, sheer, hammer, chisel, grind (etc.) your sample,
Then look at the damaged area!

DO NOT hammer a rounded case section flat!
Simply mount the outside curve DOWN so you can sample the case section in it's natural state.

You want to COLD CUT the brass sample with as little heat/damage as possible.
If the brass discolors while cutting, you screwed up, not enough coolant.

You want to remove the damaged section far enough back to see the structure where it's NOT been damaged,
Wet saws prevent heat damage, good old hack saws with the highest tooth count as possible, or an abrasive edge.
GO SLOW so you don't heat the sample up, flex the sample (work Hardening when you flex it back & forth).

IF YOU DO BUTCHER THE SAMPLE, all is not lost,
Simply polish a spot away from the damaged area.

If your sample is big enough to get a good grip on, then resin block mounting (scientific standard) isn't necessary.
I often don't bother mounting case head cross sections, they are big enough to handle during polishing, while case side & neck samples are always mounted simply because they are crazy hard to hold onto or keep flat during polishing.

Resin block mounting makes small samples MUCH easier to grind/polish, and is the scientific standard way to handle samples.

Scientific GRADE mounting resin will set you back a pretty penny,
A MUCH cheaper alternative that's stupidly available is resin CRAFTS STORE encapsulation hobby kits.
We are talking anywhere your wife likes to browse for 'Crafts' stuff, from 'Jo Ann' fabrics to Hobby Lobby to Wally-World.

They usually come with a quart or more of the 2 part resin compound, often with little cups or stirring sticks & other goodies, some have mold release included if you want really professional looking samples without polishing all the outside of the sample.

I use flexible silicone candy/cupcake/icecube/soap molds, dirt cheap off eBay or Amazon, available everywhere from Walmart to any hobby shop.

----
Once sample is mounted (your choice of mounting),
Then you polish. This is the part I dislike most.

Using SILICONE CARBIDE (and silicone carbide ONLY!),
I repeat, silicone carbide only!

Aluminum oxide or other types of abrasives can & will mix into your brass sample!
And the WILL screw up your chemical treating & observable results!

Starting at about 180 to 320 grit (Depending on how much you need to 'Hog Off' getting to clean sample material),
Then reducing size of grit to about 1,200 grit WET!
Then finishing off with buffing wheel & polishing compound.

Unless you are completely useless, we have all sanded or polished something,
Same thing only in the extreme.

One tip,
Silicone carbide sanding discs come on rolls, adhesive backed, intended for wet sanding for anything from body shops to wood shops to metal/welding shops.
That gets you 50% the way to an effective wet sander/polished.

Adhesive backed water resistant sanding disks make for fast disk changes, either for a clean disk or finer grit.

The polishing compound should be silicone carbide also, but graded for size (so stray larger granules don't randomly scratch your sample) and suspended in a lubrication of some kind, like lapping compound.
DO NOT let the pad get dry!

-----

Then samples head for chemical etching...
Different chemicals make the chrystaline structure 'POP' and appear different colors under white light.

Again, I'm NOT working for NASA or trying to justify my existence in some government job,
I often use common household or easily available chemicals.
Swimming pool conditioners, toilet bowl cleaners, hydrogen peroxide, white vinegar, even liquor store for 'Everclear' for Ethel alcohol.

Other than taking a little longer than 'Scientific' grade chemicals, you get pretty much the same results.

------

Viewing,
This is where the cost has dropped like a rock!

Just 15 years ago, a 1,000X scientific grade, scaling graduated, stereo microscope started at $22,000.
Now you can buy a USB or blue tooth magnifier for $20 that will work pretty good.

2 mega pixel or higher (usually 2mp or 5mp), in the 200X to 500X range will make you as happy as a pig in a corn crib!
Most micrograph images are in the 200x to 300x range, but for $5 or $10 you can get into 500x to 800x ranges and REALLY see what's happening.

Just get one with a good FLOOR PLATE STAND!
No stand or lousy stand will drive you crazy, so instead of $10 or $20, spend $30 and get more megapixel, magnification and a good stand, or make one immediately!

Now that you can actually directly SEE grain structure, chrystaline structure, occlusions, voids, ect,
Annealing will make a crap ton more sense to you, and you will be able to change your process to get 'Optimum' results.

Just for the record, there simply isn't an 'Easy' or 'Cheap' way to hardness test.
Hardness testing requires a very specific (scientific) application of force under very specific & controlled conditions.
None of that is cheap or easy....

Last edited by JeepHammer; June 11, 2017 at 05:11 PM.
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Old June 11, 2017, 05:23 PM   #2
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One real eye opener is to cold/wet grind/sand an entire new brass down the side & mount it...
The difference from case head, which Dogma tells you is a BUNCH harder than the neck/shoulder will surprise you!

Most hardcore 'Talkers' don't believe it the first time around...

Then take a brass, section it longways again after it's been loaded/fired 5 times and compare the difference!

Again, the hardcore 'Talkers' will flip completely out!

I'm not going to let the cat out of the bag,
You will just have to try it for yourself or con someone into doing it for you...
If you do it yourself, you are going to have a GREAT conversation piece! Along with proof 99.9999% of 'Talkers' and magazine articles are dead wrong, or didn't know how to interpret hardness testing!

The difference has to do with the way pressure builds in the case, and what the slop in the chamber & what the sizing dies do to brass...

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Old June 11, 2017, 05:29 PM   #3
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Curious that silicone carbide is the abrasive of choice. It has sharp shards that embed easily in soft metals, which is why aluminum oxide is usually used on them instead (rounder grain). Silicon carbide is more inert, though, and tends to be higher in purity.

Yeah, the cheap USB microscopes are astonishing for the price.
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Old June 11, 2017, 05:55 PM   #4
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Silicone carbide cuts cleanly & quickly.
Most other compounds either don't cut cleanly, or they don't cut quickly and smear softer samples.
Saves a crap load of time trying to clean up 'Fuzzy' cuts and remove debris imbedded in the sample.

Even low budget silicone carbide is usually very uniform in size, others aren't, the manufacturing process can produce very specific size grains where others have to be broken & sifted/graded for size.

You will get horrendous scratches from common aluminum oxide abrasive sheets, little to no quality control.
Scientific grade will cost you serious cash.

Chemical treatment means as inert as possible!
The same chemicals that react with traces of aluminum in the brass also react with aluminum oxide imbedded in the brass giving false results.

The Scientific Standard is scientific grade silicone carbide for cartridge brass samples (and most other metals).
Although I'm not using quite scientific grade anything on annealed brass samples, I get VERY respectable results...
Almost as good as using scientific grade everything.
The resin isn't scientific grade for particle density, but who gives a crap when you are mounting for direct inspection samples and not looking through the resin in the first place!

Could be holding it with JB weld or Elmer's Glue and it wouldn't make a difference in the sample since you are looking directly at the brass!

I don't see a need for deionized water when polishing samples, distilled or clean tap water is fine.
Just need something to cool the grinding process and carry off loose particles.
One side note, the scientific grade polishers RECYCLE the water, crud and all!
You have to buy a filter kit if you don't want the crud recycled, and it's no longer 'deionized' after it touches ANYTHING....

Clean, filtered tap water is cheap enough you don't have to recycle or filter it again.
Use once, down the drain right along with loose abrasive & tailings from the sample.
Since I'm not grinding plutonium, it's not a hazard.

I don't care if the resin is dielectric, anti-static, ect since I'm not doing scanning electron microscope or electrical conductivity testing.
Just has to hold the sample firmly, and I like clear because it shows off my work... (Vanity)
And helps identify what the sample is, I often write on the inside of the sample before mounting so I don't mix things up.
You can also put a paper tag in the mount to identify the sample.
Once mounted, they all look alike.

Since I'm not doing refractometer testing or alternative light work, I don't need to grains to reflect at any given wave length, so cheap & common chemical sources are fine if not scientifically pure.

It's just some basic guidelines and tips to home/affordable DIY grain inspection!

It's my 'Quick & Dirty' way to see if I'm hopelessly lost, or heading in the right direction before I pay an approved lab to prepare & grade production samples.
Those $20,000 lab bills will kill you when you are trying to make a buck on some job or another...

And, this isn't mine, an actual brass engineer turned me into this stuff so I could do quick & dirty testing/inspection.
He cost me an arm & a leg, so I sucked his brain while I had him!

Last edited by JeepHammer; June 11, 2017 at 06:10 PM.
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Old June 11, 2017, 06:15 PM   #5
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Or you could find a thirsty metallurgy undergrad and bribe him. When I was in school, I would have run your samples for couple beers and a cheese steak.
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Old June 11, 2017, 06:21 PM   #6
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Ligon,
I need interns, or trained monkeys or something!
Right now all I have is two hands and 24 hours in a day...

Since you took metallurgy, is there anything you can add or correct?
Anything that might make this faster, cheaper or more accurate?
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Old June 11, 2017, 07:08 PM   #7
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I think formal methodology usually does the etching with nitric acid, but don't know why that particular choice. Ask board member Mete. He's a retired metallurgist.
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Old June 12, 2017, 07:42 AM   #8
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Do you know a common source for concentrated nitric acid?
Something that's fairly clean of other chemicals...

Grandpa made nitric acid from barnyard dirt when I was very young, it was a long involved process.

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Old June 12, 2017, 10:26 AM   #9
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I read about it everyday; a reloader starts by complaining about loose primers and then they condemn the manufacturer and they always have 'their' favorite case they insist others must use.

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Old June 12, 2017, 10:33 AM   #10
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Etching? I use vinegar, I use vinegar for a maximum of 15 minutes for the life of the case, I only use vinegar on the worst of cases. If I was rich I would use table vinegar, table vinegar is the good stuff, they say is 15%, the other stuff is 5 %.

What difference does it make? Time; if I increase the acid from 5% to 15% I have to reduce the time to 5 minutes, maybe.

That beats the stuff I was using in the beginning. in the old days the soak time was less than 2 minutes.

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Old June 12, 2017, 10:44 AM   #11
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I made a shop call, seems they had a problem removing a heavy metal ring that they thought was pressed onto a large shaft, they thought they had no way to remove it. I asked them if they had an arch welder, the answer was "YES!". like I did not know.

I grabbed my carbon torch and then took off. I hooked up my carbon torch to their arch welder and in a few seconds, like magic, the ring slipped off. I then asked them if they wanted me to install the new replacement part, the answer was "NO!' because they were scared.

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Old June 13, 2017, 12:33 PM   #12
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JeepHammer, I am truly in debt to you! The tip about the USB camera is priceless - a decent metallograph is indeed thousands of dollars, and even a cheap binocular inverted microscope is on the close order of $2k. I will be trying the USB magnifier for sure!

For etching, search the web for ASTM E407 - even an old version is fine, the compositions do not change, only get more numerous. For brass, potassium dichromate is standard, followed by ferric chloride - dilutions are in E407 but your vinegar (acetic acid) works, just takes minutes instead of seconds.

For steels, 2%- 5% nitric acid in alcohol (known as 'Nital') is pretty standard.

Nitric acid can be gotten from potassium nitrate. Spectracide stump remover is technical grade potassium nitrate (odd, you can get dusting sulfur at the garden store too; and some charcoal, and you have the fixin's for black powder).

And you are absolutely right about the cold-mount plastic. The stuff from the hobby store is precisely what most metallographers use for cold mount. Hot mount is phenolic + pressure + heat (~300ºF) - no need, it is just faster than cold mount, and a little harder (which keeps the edges flatter). Go to buehler.com - they are the best in the industry. Under "Solutions" click on TechNotes and you will find some useful tips and tricks.

Thank you! Now I need to go buy a USB magnifier.
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Old June 13, 2017, 02:58 PM   #13
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The guy I had to hire didn't use nitric acid, but that might have been a quirk of the parts I was making, brass springs aren't all that common and might have something going on firearms cases don't have.

Appreciate the tip!

What worked pretty well was industrial 'Pickleing' vinegar, the kind used to clean metals, not process food. Worked well and no one from the FBI showed up asking what I was using it for...

If you can buy it out of the regular tooling catalogs and from someplace like 'Granger' then you probably aren't on some terrorism watch list...
Well... not for that anyway! But you are still a reloader...
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Old June 13, 2017, 05:11 PM   #14
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Just for the record,
Silicone carbide self adhesive disks in both 5" & 6" are available for auto body sanders.
They come on a roll & are rated for wet sanding.

8", 12" & 20" are available commonly for wood working applications.
There are several sizes for lapidary applications,
Most available with or without adhesive backs.

A little dribbler on your work (garden hose/tap water) will keep you wet and flushed.

A quick hunt on eBay turns up the backing plates for face/belt grinders in all sizes if you want to make the face grinder yourself.
I found an old potters wheel on Craig's list for under $50 that serves the purpose....
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Old June 15, 2017, 02:28 PM   #15
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Board member BigCheese PM'd me to say he has a metallurgical background, and that nitric acid is only suitable for steel. He says they etched brass with ammonia with hydrogen peroxide added (that causes bubbles to clean the surface and it speeds up etching with acids, too). He says they used 1:1:1 water:ammonium hydroxide solution:3% hydrogen peroxide solution. He did not say what the ammonium hydroxide solution concentration was, but I have PM'd him back to ask. I let you know if he recalls the number.
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Old June 15, 2017, 08:44 PM   #16
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Ok, call me weird...
I'm sitting here anxiously awaiting to see the results of this grain structure testing!!

Still wondering how the grain structure would look if you turned a piece of brass on the lathe' as opposed to the stretching method currently in use for making cases.

Yeah Jeep, i'm still on that.. Lol
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Old June 15, 2017, 09:34 PM   #17
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I'm starting to think it may not work out well. BigCheese ran a metals testing laboratory. He says:

Quote:
Originally Posted by BigCheese
There is a lot more about sample preparation for brass. It is more difficult than for steel, since the softer the metal, the greater the possibility of distorting the true metal structure during grinding and polishing. Metal must be removed by cutting away atomic layers, and not polished as by burnishing. Metallographic polishing is almost as much an art as a science.
So I'm losing faith that the silicone carbide approach isn't too coarse and going to produce grain structure at the surface that's not really representative of what what was there before the polishing started. I'd expect much the same from the lathe tool, albeit on a different scale. It seems like some more research needs to be done on the surface preparation.

The ammonium hydroxide turns out to have been reagent grade 28%, not the 5% stuff you get at Ace Hardware for cleaning. The percent in the finished etching mix was 9.33%, so no juggling the water addition can get you there, starting from 5%. But perhaps the weaker solution would still work, but just more slowly.
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Old June 16, 2017, 06:00 AM   #18
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What about the surface structure, also?? If you looked at the grain of the outside, inside surfaces would they be indicative of the inside structure?

With the base/rim being pressed, and the flash hole being punched i would expect varying grain structure there.

Would be curious to see the grain for different alloys also. No 2 manufactures are the same.
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Old June 16, 2017, 08:19 AM   #19
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I never saw nitric acid used on brass here. Kind of threw me when someone suggested nitric acid, I had to ask for a source since I hadn't used it.

It's true the household chemicals take longer sometimes, but accomplish the same, or good results.
Sometimes the household stuff will introduce stuff you don't want, so it's trial & error...
I usually run with what the brass engineer recommended.

I also posted a misprint, I posted sodium hydroxide when I intended ammonium hydroxide.
Bleach will work, just crazy slow, but shows up some real colors.

This isn't gem stone or microscope lens polishing here, we aren't talking sub micron finishes,
We are talking 1,200 grit with a final finish buff, not 4,000 grit with a 0.2 micron fixed polish.
Some car finishes get 1,200 grit wet sand, so body shop equipment will get you there, with a final gem polish just to brighten things up a little...

I'm sure there will be people convincing themselves there is 'No Way!' the average guy can do this without years of training and $500,000 in scientific equipment,
They are talking themselves out of trying!

And, obviously, people are getting hold of metallurgy professionals and asking questions!
The replies a week or more later with specifics are proof of that.
Some say 'Right On! Good Idea!', others will have doubts, still others will crap on it outright...
It's the way of scientific progress to challenge everything, so I don't mind that.

Are you going to get top end results? NO.
Are you going to produce results a top end lab could get useful results from? YES.
I've done it with help from a brass engineer...

Like I said, you won't be doing 'No Fail' testing/inspection for NASA on a Mars mission, just seeing what's going on with your brass.
You are only looking with your own eyes in a visible light spectrum, this ain't rocket science!

Humans have been doing this since the 1870s, without highly refined chemicals, epoxy mounts, perfectly sized grit abrasives, and far worse magnification lenses...
And they produced useful results!

Last edited by JeepHammer; June 16, 2017 at 08:53 AM.
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Old June 16, 2017, 08:31 AM   #20
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STD7Mag,
I cut them longways, neck to head right through the flash hole sometimes and test the entire case for both hardness and grain structure...
That makes for a difficult mount & a lot of grinding, but they look cool (cutaways always do).

There are some serious surprises in that case from the manufacturer!

Most of what I've done in the shop is necks/shoulders, no need to section the case head since you aren't annealing/changing anything anyway,
I have to section samples when I run new manufacture brass, and it's a pain in the butt.
A water jet would have saved a TON of time, cold cutting is mandatory, nothing is faster than a water jet.
Simply mount the entire brass and cut sample block/brass at the same time before grinding.

If you try this, find someone you trust with a hardness tester! You won't believe the results even before you see the grain down the case length...
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Old June 16, 2017, 08:51 AM   #21
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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...
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Old June 16, 2017, 04:56 PM   #22
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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.
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Old June 16, 2017, 06:24 PM   #23
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-Poof-

That's what just happened to my brain! Thank you for the good read. Any one have pictures of samples to share?
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Old June 16, 2017, 07:10 PM   #24
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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.
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Old June 17, 2017, 08:30 AM   #25
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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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