Induction Annealing Troubles

[Wheres-Waldo]

Before reading all this, Im stating that I'm assumeing there will always be a visual difference between clean, non-annealed brass and that same peice of brass having been properly annealed using induction heating.

OK, well I have had the equipment to anneal via induction heating for quite some time.

If a list of my equipment and set-up are revelant... it is as fallows.

GraLab 450 Timer
Mini-Duct Induction Heater
Tempil TempStick Complete Test Set (125* - 800* Range)

The heater, when plugged up to the GraLab, can be controled down to the 10th of a second.
The coil of the heater is set flat and center on the top of a single stage press.
The brass is ran up into the press.
Timer is started.
Once the time has elapsed, the heater shuts off and the brass comes out and goes into some water.

I determined the correct height the brass needs to be in the coil, and the appropirate time using the tempil test kit.
(Bottom 1/2 of the case does not go above 450*, the neck and shoulder are hotter than 700*, but cooler than 800*, for 6 seconds)

Bottom line is, after doing 100 cases, every one of them look as sparking shiney as before I started. I could care less if they look like factory Lapua brass, but I do care if they are being properly annealed. My Tempil test kit is saying Im in the right tempurature range, confined to the correct area of the case, for a suitable ammount of time (no more than a FEW (?) seconds (per the referance http://www.6mmbr.com/annealing.html)

So is the fact that they look no different afterwards indicating Im not accomplishing the task, or do I just not get the bonus of cool looking necks and shoulders...

If pictures are needed, let me know and Ill set up and take some...

As always guys, thanks in advance for any help, and happy Laybor Day weekend...

 

[mdmp5]

Re: Induction Annealing Troubles

Does the brass turn red while you are annealing? Why don't you try this...take a piece of expendable scrap brass and hold it in the coil for a much longer time. See if it glows or tarnishes.

 

[Wheres-Waldo]

Re: Induction Annealing Troubles

No, the brass doesnt glow (by turn red, Im guessing you mean glowing?), I know its not saposed to glow.

If by red you mean this...

Then no, its looking more like this...

And none of my 6.5x47 Lapua Imp. brass is expendable. I ran some .308 Win through the same setup and time and it was glowing red hot, so its not a fair comparison in my eyes. The .308 LOOKED annealed, but I know it was way too soft afterwards.

Here is how Im going about it...Timer not shown.

 

[Ratbert]

Re: Induction Annealing Troubles

The tempilaq should tell the tale. If you're getting up to the proper temperature then you should be good. The discoloration I get when annealing with propane tends to polish off in the tumbler, (as does what comes on my factory annealed Lapua brass) so I wouldn't worry about it.

I WOULD reconsider dropping the brass into the water. If you heat it up and then insta-cool it what you're doing is hardening, not annealing. But I'm not an expert on metallurgy. Most of the annealer manufactures I've seen just let it cool via ambient air exchange.

Are you raising it to 750 and holding it there for 6 seconds, or just taking 6 seconds to reach 750? Once you've reached 750 you should be done, no need to hold it (and let the heat creep further down the case.)

ETA: An interesting idea. If I hadn't already dropped $500 on a bench source this is definitely the sort of project I could be all over.

 

[WDL]

Re: Induction Annealing Troubles

I anneal with a cheap propane torch spinning the brass with a cordless screwdriver. I don't quench because every video of every annealing machine I have seen does not quench.

 

[mdmp5]

Re: Induction Annealing Troubles

I read a while back that there is no advantage to quenching over air cooling.

 

[Niles Coyote]

Re: Induction Annealing Troubles

I did some 308's back in December. I did not see any discoloration at the time... but some of these sat in a box for 6 months and they look very much like new Lapua brass now. If the Tempil is applied to the inside of the neck (750d paint is what I use) and it burns off/evaporates you are reaching the desired temps.

 

[Wheres-Waldo]

Re: Induction Annealing Troubles

I dont quench for any reason other than being able to handle the brass without waiting 5 minutes. I could probably omit this step and have identical results. Also, the only way to harden brass is through cold working, according to that same referance.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> The only way brass can be made harder is to "work" it. That is, the brass must be bent, hammered, shaped or otherwise formed. Once it has been made hard, it can be returned to its "soft" state by annealing. The hardness of brass can be controlled by annealing for a specified time and temperature.

Unlike steel, which will be made harder when it is cooled rapidly, brass is virtually unaffected when it is rapidly cooled. Annealing brass and suddenly quenching it in water will have no measurable effect on the brass
</div></div>

For Ratbert, the Tempil is melting in about 4-5 seconds at the 700* markings.

It seems the consensus is that discolouration doesnt make the annealed brass what it is, so Im happy with what I have.

Furthermore, I suspect that some, if not most of the discoloration in typical annealing comes from the flame. The referance also indicates that color should be of some importance in determining the proper annealing time/temp, though I trust my temp-sticks more than the color.

With the induction method, the heat itself can not be adjusted, only the time and position of the brass within the coil... the coil itself CAN be wound with more or less revolutions to control how fast it will heat whats inside it.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> If the cases do not develop any color at all, then increase the intensity of the flame or adjust the flames so that they play more directly on the case necks, or a combination of the two.

Do not expect that the color will be as dark as it appears on military cases. This darkness of the color on military cases occurs over a period of time, as do the delicate reds and purples around the dark color. If you leave one of your cases sitting out for a few months, it will begin to take on the same appearance that military cases have.

When you get the faint blue color and the shine remains on the case, you have everything adjusted to perfection.

</div></div>

If someone wants to spare a few cases of similar size for expirementation, as to be test subjects for dialing the time down, I would be more than happy to post my findings on what induction annealing to reach that color takes, tempurature wise. You can PM me on that if you wish.

Either way, thanks for the direction guys... much appreciated.

 

[mdmp5]

Re: Induction Annealing Troubles

How much did that mini ductor run you? And can you tell me a bit about that timer?
I really like your setup.

 

[MitchAlsup]

Re: Induction Annealing Troubles

I suspect that either a) the amount of heat inducted into the neck is insufficient, or b) the time the case spends in the coil is insufficient, or c) a bit of both.

The soldering iron equivalent wattage of a blue flame used for annealing is at least 1500+ Watts, and I doubt that your inductor is in that range.

Tempilaq will tell you how long you need to 'cook' wiht the inductor.

 

[Proarc]

Re: Induction Annealing Troubles

Water quenching will not harden the brass. But does stop case mouth dents from dropping when hot.

 

[Wheres-Waldo]

Re: Induction Annealing Troubles

Palmik, they certainly arent on the cheep side, if I remember correctly, somewhere in the $500.00 ballpark.

The timer is a GraLab 450 timer. Its just a timer they you plug into the wall, then plug what ever into the timer, set your time in .1 second intervals...and go at it. Its got a foot switch which is convenient.

Mitchlsup, Im not saying your wrong by any means, but Ide like to know what makes you think that?
Oh, and the Mini-Ductor.... 1000 watts with a single strand coil.
I doubled up the coil, which certianly made a BIG difference, but as far as comparison to a torch, I have no idea.
I know its capable of getting hot enough quick enough...

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> I ran some .308 Win through the same setup and time and it was glowing red hot</div></div>

 

[TexIndian]

Re: Induction Annealing Troubles

THIS ARTICLE may be helpful, especially on the question of quenching.

 

[Ericc]

Re: Induction Annealing Troubles


Induction heating is a different beast then flame heating. There is an important factor called skin depth which is determined by the frequency of the inverter running the induction coil. Based on the size of the unit I'd guess its running at a very high frequency. This reduces how "deep" the induced heating current penetrates the case wall.

Put your temperature sensing compound on the inside of a test case and run your test again and see if you are reaching your target temperature on the inside of the case.

You may find that the smaller induction unit has very shallow heating potential and you'll need to get the outside of the case considerably hotter to reach annealing temperature through the entire web of the case neck. There are other strategies like pulsing etc that can allow the case to heat more evenly.

Eric

 

[nfresquez]

Re: Induction Annealing Troubles

I have been interested in induction annealing for a while now and have been trying to think of a good way to automate one like the big guys use. In this search I watched a video (which I cant seem to locate now)that showed LAPUA annealing their brass and it seemed to have the discoloration right away.

 

[Wheres-Waldo]

Re: Induction Annealing Troubles

Eric, PM inbound....do you have a referance I can read to better familiarize myself with what your talking about? The more I can know about this, the better off I am.

Essential, if you do find that video, post it up!

 

[Kinsman]

Re: Induction Annealing Troubles

Based on my very limited knowledge of heating metals, I would surmise that the color change in the brass is caused by oxidation in the flame. Wouldn't happen in the inductor.

 

[memilanuk]

Re: Induction Annealing Troubles

Very interesting stuff. Just as an aside, from someone with a Brass-O-Matic annealer... you can literally watch the color change happen with a two-torch setup. It starts about the time the TempiLaq would melt, and then runs down the neck and shoulder and just starts down the body - at which point the shell plate rotates, etc. I'm not convinced its oxidation from the flame, because I've seen the color moving below where the torches are hitting (directly anyways - its still damn hot!).

 

[Sean the Nailer]

Re: Induction Annealing Troubles

As others before me have stated, this is a very interesting process. I too am interested in the viability of incorporating this into our 'regimen'.

To go further, I'm aiming more towards adding this to the trimming stage so that both steps are completed at once. hmmmmm.... This being possible because my trimmer is just 'a little bit' different than everyone else's.

 

[The Mechanic]

Re: Induction Annealing Troubles

Here is a shot in the dark on this. I think that the induction annealer gets to temp and stops addition of heat MUCH faster than propane or flame annealing.
As to brass.
http://www.lfa-wire.com/c26000.htm
It shows brass annealing temp is a min of 800F. My thought is that the templiq may be melting at 750 with flame but by the time it melts you have added more heat to the higher temp and time of 800. I think that the induction is just getting to the 750F and shutting off so fast that you don't get to the 800. I would experiment with adding a little more time in steps until you fry a few to get a good idea what is happening. Along with a nice little squeeze on the neck to see how much spring back you get. Maybe get a few new unfired cases to squeeze to compare a perfect case with what you are really getting. Once you have it perfect you will know you got it right every time.

 

[Wheres-Waldo]

Re: Induction Annealing Troubles

Apon talking to some other local reloaders, they gave me some advice and some junk brass to play with.

Im able to keep the necks under 800 but above 700 and the bodies (at about 1/2 length) below 425 for 9.8 seconds. They tolb me my problem was most likely that the inductor, since having to warm up for a second, is going to extend my annealing time just a tad.

I was able to get good results on some .260 brass... All tempuratures on the entire case are under detramental tempuratures, and some faint, yet noticable pinkinsh blue on the neck and shoulder, and a little rainbow-ish right below the shoulder. 9.8 seconds is where its at for .260 and 6.5 Lapuas'.

Im going to polish my entire lot up, do them all at 9.8 sec. and Ill post results/pictures tomorrow probably.

 

[Sean the Nailer]

Re: Induction Annealing Troubles

Really looking forward to this. Thanks.

 

[sidehill]

Re: Induction Annealing Troubles

Give this a try. As you practice on other pieces of brass that you are not going to use. Watch the inside of the case neck, you will see it turn a different color(it will be just a slight change but you will see it). Just as the color changes you want the timer to shut off.

I also pulled the switch out of the mini and spliced the wires together so I did not have to hold the button on the mini while the timer was running.

As soon as the timer shuts off pull the piece of brass out of the press and wipe with a wet towel. No water in the case to worry about and the case is cool enough to handle right away.

One other thing is that different diameters of brass will take different settings on the timer. The closer the neck is to the inside of the coil the faster it will it will anneal the case. My coil is sized to anneal the cheytac case, so if I anneal 223 brass I need to set the timer for a longer setting to anneal the 223 brass, as the case neck is further away from the inside of the coil.

Hope this helps you if you have any question shoot me a pm.

 

[Wheres-Waldo]

Re: Induction Annealing Troubles

Sidehill, have you found any correlation between the amount of coils in the "coil" I guess you would call it... and the speed at witch the miniductor will come up to temp?

The first few cases I do wont be near close enough to the right temp because the miniductor hasnt really warmed up yet. I starded just setting the timer for 1 minute of solid heat before I start timing any cases through it.

I appreciate the words of wisdom.

Im just waiting for the tumbler to get a good polish on before I run my brass through for a few pictures....

I pulled 3 decently clean ones and ran them through.... you can see the results.
This is after 1 minute of constant warm-up then 9.8 seconds per case.

 

[sidehill]

Re: Induction Annealing Troubles

The overall length of the coil would have a little influence, but the number of wraps would not. Two coils the same length will heat at the same speed. A single stacked wrap seams to be more consistent than overlapping wraps like you have. I formed my coil in a cone shape to match the brass so the shoulder and neck of the brass heat at the same speed. The tighter you make the coil to the brass, the faster it will heat the brass.

 

[Ericc]

Re: Induction Annealing Troubles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wheres-Waldo</div><div class="ubbcode-body">Eric, PM inbound....do you have a referance I can read to better familiarize myself with what your talking about? The more I can know about this, the better off I am.

Essential, if you do find that video, post it up! </div></div>

I don't have a reference link handy. I did design an induction heater two years ago that was going to target the reloading community. I couldn't get the price point down to something reasonable with the features I wanted. It was a 1700watt table top unit and would anneal a case in about one second. When the tank capacitor costs over 300 dollars, making the rest of the unit affordable becomes a challenge. At this power setting you're basically making a device comparable to a welder just at much higher voltages.

Here is an application note by fairchild that goes into the induction heating process. It's not really intended for the end user, rather the engineer. But it has some good fundamentals in it.

http://www.fairchildsemi.com/an/AN/AN-9012.pdf

Changing the coil can have a very significant impact on the power transfer to the item being heated. Too few loops and you get excessive heat in the inverter and too many can produce excessive voltages that blow up FET's and caps. The manufacturer should have recommendations for coil diameters, # turns etc.

Here is an article on your unit where someone tore into it.

http://www.johndearmond.com/2010/01/08/mini-ductor-induction-heater/

Eric