Gas Vs Induction Annealing

[SteveOak]

Norm,

Thanks for the response.

I probably should have mentioned that my day job is the protection of avionics that fly heavy commercial jets from the effects of electromagnetic interference and lighting.

You did not mention the measured resistance of the cases. What resistance do you typically measure on say a 6 BR case? 6.5 X 47 Lapua case? 308 case? Do you see much of a difference with cases from different manufacturers? Winchester, Remington, Lapua, Norma and so on.

So there are fans blowing air directly on the "work coil" and the case being annealed?

What is the temperature range of the "work coil"? How much does it vary from start up to having annealed 100 cases? 200 cases?

Pix would probably help me understand better.

 

[SteveOak]

First, you have to understand how induction heating works.

The induction heater contains a high powered oscillator operating at, say, 20 kHZ to 200 kHZ. Its output is an output voltage with high current capacity. This voltage source is connected to a coil commonly called the "work coil." the term "voltage source" must be explained, a voltage source by definition is a low impedance source of a fixed voltage with wide current capacity. When the brass case is inserted into the work coil, the case becomes the secondary of a transformer. By nature of the geometry of the case, this transformer has a "shorted secondary as the secondary is a tube . Some units use a work coil with the case inserted into it, others (like my Annie) use a ferrite core that the work coil is wound around. This core can be square or round, no significant difference. The core has a gap cut into it that the case is inserted into. When the heater is operating, the flux in the core is maximized in the gap due to the permeability difference between ferrite and air. Still, the work coil and the brass case make up a transformer with work coil primary and case secondary. The number of turns in the primary versus the single turn in the secondary (by nature of the "tube" being a single, shorted turn) transforms the voltage in the primary to a lesser voltage on the secondary by the ratio of pri to sec turns. My Annie has 4 turns in the primary so the voltage impressed on the secondary is 1/4 the primary. This turns ratio also increases the current in the secondary to 4 times the current in the primary. So, if the primary has an AC voltage of 100 Volts, the secondary voltage on the case will be 25 Volts. And, for a 1000 Watt unit, the primary can supply 10 Amps (10 Amps times 100 Volts equals 1000 Watts). This 10 amps in the primary is transformed into 40 Amps in the case secondary. The case has a finite resistance so the 40 Amps flowing in the neck of the case produces 1000 Watts (40 Amps times 25 Volts). The actual geometric split of the current in the case is complicated as the resistance of the neck (the hottest part) increases with temp while the case body stays cooler and has less resistance, but the farther you measure from the neck which is in the gap, the less current flows in the case due to spreading resistance from neck to body.
As the secondary is mostly a current source and the primary is driven by a voltage source, the increase in coil resistance makes less effect on secondary current. The internal work coil is cooled to keep it in one piece! The panel connector on my Annie is cooled by holes around it so the internal cooling air driven by a fan passes over it. Without cooling, the connector over-heats and melts the solder in the Litz wire termination which increases resistance even more and takes away power from the case. Cooling minimizes this problem. The AMP has the work coil inside the box so can directly cool it with fans.

See, nothing to it!

I had never looked at how induction heating works so I did some reading.

What you have described is not how an induction heater works. You have described a transformer which causes current to flow in through a secondary circuit. This is not how an induction heater works. Induction heating does not have a secondary circuit in the sense that you described. An induction heater induces eddy currents into the 'target'. There is no current flowing "through" the brass case. The eddy currents flow only within the case.

Think of a frying pan sitting on top of an induction range. Where is the "secondary circuit?" Where does current flow into the frying pan? Where does current flow out of the frying pan? It does not.

I am not saying that an induction annealer is not a possible, it seems to be, nor that it is inferior. It may be that an induction annealer is the superior method. I am looking for evidence to support one of those conclusions.

Now that I understand how induction heating works my questions on case resistance are no longer relevant. When we simulate the effects of indirect lightning we use copper wire in the primary of the transformer circuit because it has very low inherent resistance and therefore the least current loss and corresponding heating effect.

 

[dmoran]

Steve -
About the only website that I have ever been able to find resultants is AMP's website:
www.ampannealing.com Then surf there drop down's (like "About Brass Hardness").
Lots of interesting information, results, study, and instructions, through out there site.
Donovan

 

[SteveOak]

Donovan,

Thanks for the posting.

I am completely convinced of the absolute necessity of annealing, no problems there.

At this point I am following the question inherent in the thread title (although it appears to be rhetorical ) kicking over rocks until I find sufficient evidence that either gas or induction is the better method or if perhaps neither has an advantage over the other. Perhaps is comes down to the specifics of the methodology, that is to say the inherently better method is only superior if it is applied in a certain way.

Steve

 

[Jose_Luis_G]

I would like to give you further information.
I'm on my way to finish my own induction annealing machine, and let me say that mine is water cooled.
I mean that the coil has a permanent water flow through it, just to avoid overheating.
Despite this device, after a while of operation the temperature water rises and a water change is required.
To avoid that, I've ordered an electric cooler -12V Peltier, same as used in the PCs- together with a water radiator and a cooling grease to convey the cold to the radiator.
Even when mine is in prototype status, I have already annealed a few cases and it shows to be constant, to what the results is concerned, no matter if it is the first piece or the last.

 

[SteveOak]

Now we're getting somewhere. Thanks Jose!!!

The thermal conductivity of water is an order of magnitude greater than that of air. Air in fact is a commonly used insulator. Water cooling would also be much more consistent, especially if you monitored and controlled the temperature of the water.

You say that the annealing you are doing "shows to be constant". What do you mean by constant and how do you determine that?

Pix would be awesome!!

 

[normmatzen]

Steve, Guess again. Your comment is bases on semantics.
Certainly, the induction "work coil" does induce eddy currents in the target. But, the target is a brass case that to a first approximation is a brass tube. If you had studied a bit more, you would have found that when the "target" is a ferrous material, way more heat is generated than if the "target" is a copper alloy. It is a compound function with ferrous "targets."
I don't care weather you call it Eddy current or not (check the definition of "Eddy current) but current is induced in the brass "tube" proportional to the turns ratio of the work coil to the "tube" . In my Annie case that is 4:1 or the tube carries 4 times the current that the work coil does due to transformer action.

 

[Jose_Luis_G]

Now we're getting somewhere. Thanks Jose!!!

The thermal conductivity of water is an order of magnitude greater than that of air. Air in fact is a commonly used insulator. Water cooling would also be much more consistent, especially if you monitored and controlled the temperature of the water.

You say that the annealing you are doing "shows to be constant". What do you mean by constant and how do you determine that?

Pix would be awesome!!

Now I'm about to part for vacation, but I'll be back in a fortnight.
I will try to take some pics, but don't forget that this is a prototype and I've been using quite a few microwave oven parts as well as chineese components -I know you like the chineese stuff quite a lot- but I didn't want to spend a lot of money in UK components.
All in all, the complete budget for this one I'm working on, hardly goes above $120.

My device is time controlled with an accuracy of 0.1 sec, so it is very easy to set the right time for every type of case and, once you have found the time, it can be repeated as many times as needed.

 

[normmatzen]

Steve,
Sorry, I didn't finish answering your question.

The front terminal block on the Annie is connected internally to the two sides of a push-pull oscillator as well as a couple inductors supplying primary power and some capacitors to tune the external coil to the approximate correct frequency. There is no fan on the case or external coil, just a ring of holes in the chassis around the terminal block to aid in keeping the terminal block cool as it can heat up due to IR losses in the terminals. The attached photo (If I'm lucky) shows the top of the terminal block on Annie and the ferrite core with the Litz wire 4 turn coil on it. The case neck is placed in the gap in the core at the point of maximum flux density. The coil does get hot, but I have annealed up to 100 cases as quickly as I could and it never over-heated (i.e. smoked!) The internal fan keeps the electronics from over-heating. If it does over heat, there is an internal sensor that turns off primary power till it cools. My Annie has not done that yet.

Yes, I have different times for the different cases I anneal. I shoot mostly 6BRX and 284 WIN. For the 284 WIN I have both W-W cases and necked up 6.5-284 Lapua cases. These two brands need different times to anneal. I adjust the time based on experimenting with 750 deg Tempilac. As a metric, I shoot in the vicinity of 2000 to 5000 shots a year and I now anneal after every firing. I did have problems with my Annie but Fluxeon replaced it twice during their intro to manufacturing hiccups and the last 6-8 months it has been trouble free. I reload at least 150 to 250 cases a month with no problem, and Annie is quick!
I don't think water cooling is necessary unless you are using the Annie attached to a Giraud and are commercially annealing brass. The changes in resistance of the copper wire and Litz wire as well as the case resistance is not a first order problem as the current is relatively low in the work coil circuit and in the case it is constant as it is driven by what is essentially a current source.

 

[highlife]

Norm
What Gen you got ? I got a Gen 3. Ive had no probelms for 1 year. I know they Had probelms at the begning they upgraded to a 1200 watt unit that was a flaw that they firgured out. The AMP is rated at 750 which when they say it needs to be cooled down after so many rds Annealed.
Richard

 

[spclark]

Conceptually I agree with what you're suggesting. As a point of discussion consider the time a case is subjected to ambient temps varying from cold to the cut-out point in the area within the inductor. If that's kept to a practical minimum, the time it's affected by the variance in ambient temperature compared to the time interval it takes to reach an established set point for annealing is a very small percentage.

Starting anywhere from 70° - 190° (saturation temp if left in proximity to hot inductor for how long?) the time to rise to 750° is so short as to make the starting temperature irrelevant for all practical purposes.

Extended time at 190° has no discernible effect on brass temper. Whether a case starts the annealing cycle at 70° or 190° ought to have little to no discernible affect on the outcome I'd have to think.

 

[highlife]

Conceptually I agree with what you're suggesting. As a point of discussion consider the time a case is subjected to ambient temps varying from cold to the cut-out point in the area within the inductor. If that's kept to a practical minimum, the time it's affected by the variance in ambient temperature compared to the time interval it takes to reach an established set point for annealing is a very small percentage.

Starting anywhere from 70° - 190° (saturation temp if left in proximity to hot inductor for how long?) the time to rise to 750° is so short as to make the starting temperature irrelevant for all practical purposes.

Extended time at 190° has no discernible effect on brass temper. Whether a case starts the annealing cycle at 70° or 190° ought to have little to no discernible affect on the outcome I'd have to think.

AMP will get it firgured out! I talked to Garret alot about it before I dropped the coin on the Annie.
AMP haS done their homework, But they missed this IMO.

 

[normmatzen]

Highlife,

Mine says 2.3 on the label.

My first return would only let me do about 20 cases before it would shut off, the second one the timer quit and the third one is working great for the better part of a year. I am a happy camper. Garret was very prompt with correcting my problems. I felt it was worth working with him as I trusted the basic design, it just took him a while to de-bug it. Of course, his next product will be well vetted before he goes into volume production!

 

[SteveOak]

Conceptually I agree with what you're suggesting. As a point of discussion consider the time a case is subjected to ambient temps varying from cold to the cut-out point in the area within the inductor. If that's kept to a practical minimum, the time it's affected by the variance in ambient temperature compared to the time interval it takes to reach an established set point for annealing is a very small percentage.

Starting anywhere from 70° - 190° (saturation temp if left in proximity to hot inductor for how long?) the time to rise to 750° is so short as to make the starting temperature irrelevant for all practical purposes.

Extended time at 190° has no discernible effect on brass temper. Whether a case starts the annealing cycle at 70° or 190° ought to have little to no discernible affect on the outcome I'd have to think.

The point that I am making may or may not be significant but is not quite what you have described.

From the description of how the AMP annealer works I am assuming that the annealer applies a specified amount of energy, X voltage for Y time and would therefore cause a finite amount of energy (not temperature, energy) to be applied to the case. Applying a fixed amount of energy would (assuming for the sake of discussion that each case has identical mass, dimensions and metallurgical composition) cause an identical rise in temperature to each case. I am not saying that the induction would cause the temperature of the case to change to a certain temperature, I am saying that it would cause the temperature of the case to increase by a certain, fixed and repetitive amount.

If the annealer has been running for a while and you were to put a case in position but not fire the annealer, no energy applied, since the temperature of the internal components has risen and the Second Law of Thermodynamics would suggest that the heat of the internal components of the annealer would transfer to the case. This would cause the temperature of the case to rise by some amount, maybe a few degrees or, if the temperature of the core has risen significantly, up to 120 degrees F like my example, maybe the temperature of the case would rise 50 or 100 degrees F.

I understand the annealer to work only on time and not temperature, so it would still apply the same amount of energy as it did when the components of the annealer were cooler. My understanding of thermodynamics and energy transference leads me to believe that these two are additive. That the electrical energy of annealer would cause a fixed rise in the temperature of the case, regardless of the starting temperature of the case and that the heat soak from the internal components would cause an additional rise in the temperature of the case.

Will it make a difference? I don't know. Will the peak temperature that the case reaches be incrementally higher for each case annealed? I believe so.

One way of testing to see if the two sources are in fact additive would be to put a spot of Tempilaq that would indicate at a temperature 10 or 20 degrees higher than what the annealer is set for and run 100 or 200 cases through. If it melts then repeat the experiment with Tempilaq of a higher temperature.

 

[normmatzen]

Correct Steve, but I think practically, if the case increased 10 deg while in the machine prior to annealing, and the anneal increased it to 750 deg, the difference is ~1%. Hardly a significant difference. I would guess it is hard to program time that accurately.

I think the AMP not only programs annealing time, but annealing energy. My Annie only controls time and energy is what ever the power company produces relative to 120 VAC. This way, they can vary the incremental rate of change of temp vs time to assure adequate time allows correct metallurgical change. In other words , two different cases may need 3.0 seconds, but one may need 750 Watts and the other 850 to insure the proper Watt-Hours do the annealing.
That is one feature I think the AMP has going for it. It is much more precise than my Annie, but I still think the Annie beats flame annealing for the average reloader. It doesn't make any difference for a case manufacturer as they carefully set up the flame size and temp and it runs for long times. At home, the flame is controlled by a guess as to exact distance to case and the flame size and temp is largely unknown as the gas flow is proportional to valve opening and tank pressure. I have long felt that gas annealers would rise to their best capabilities if the owner would put a pressure regulator on the tank so not only would the valve operate against a constant pressure, it would operate in a mechanically more linear range of motion.

 

[dbduff]

I'm feeling lost.
D

 

[SteveOak]

I have an AMP, so let me put this out there.

Playing with different settings, I was somewhat surprised that it seems to not change the "time", but instead the intensity. I mean from *programs in the 30's all the way to the 90's, it basically takes 3-3.5 seconds or so. I don't necessarily have an opinion on if this is good bad or indifferent, they have the lab equipment and I don't.

Tom

Thanks for the info Tom. That puts a different spin on it. If the time is limited to a few seconds then the heat rise of the case due to the temperature of the surrounding components would be negligible.

Thank you for the interesting discussion Gentlemen.

 

[normmatzen]

Tom,
That's interesting about the time always being 3-3.5 seconds and the energy level changes. That is consistent with my Annie, I have two coils for mine one is the Litz wire coil and the other I made from #4 solid copper wire. The solid wire coil seems to supply more energy to the case than the Litz wire, but heats up faster.
Just last week I found I needed 1.8sec to anneal 6BRX cases to 750 deg back to include the neck. This with the Litz wire coil. Yesterday I annealed some 284 WIN cases. The W-W cases required 2.5 sec from the Litz wire coil. When I got to the Lapua cases I got to 3.5 sec without getting the necks hot enough. In fact, it seemed that above 3 seconds, any increase didn't heat farther down the neck. I put on the solid wire coil and found they annealed perfectly at 3.5 sec. I would not be surprised if the 6BRX cases would anneal even better with less energy and 2.5-3.0 seconds!

That I believe is the beauty of the AMP, programmable time AND energy level.

 

[sparky123321]

I love my Annie. I like that the cases are upright and I can observe the heating process. I have a small computer fan blowing across the work area and I can run as many cases as I like as fast as I want.

 

[Maxden]

Trouble is you can over anneal then your brass is junk, or under anneal and it does absolutely nothing.

I think Eric Cortina disproved that with a video account of over annealed brass