Must be some pretty smart brass to know the difference between a flame and an induction coil when the temps are 700-750 degrees. LMAO
First I will state my bias, I have unanswered questions regarding the induction method and even though it has the potential to anneal in a more even manner than the heat method, I am as of yet unconvinced that the induction machines available are achieving this.
Is it significant? I do not know.
Response to post quoted above: Because of the way the heat is presented to the brass, the flame being a single (or two single) point(s) applied externally and then spreading through the brass by conduction the brass will always be heated less evenly that would be achieved by the induction method.
The induction method uses electromagnetic waves that cause the brass to become hotter by exciting the molecules of the brass whereby each individual molecule would become hotter. This would heat the brass in a significantly more uniform manner and even though the inner molecules would be exposed to a slightly weaker electromagnetic field, the induction method has the potential (no pun intended of course) to cause the brass to become heated in a much more evenly distributed manner.
Now to my concern about the induction method as presently available.
Here is a quote from the website of a manufacturer of an induction method annealer.
"
Thermal Protection
In common with any induction heater, with extended use, the output inductor will gradually heat up. Multiple fans are installed in our annealer to keep the circuitry and inductor cool. After 40 – 50 cases have been annealed, the top of the unit behind the pilot will start to feel warm to the touch. This is normal.
In the event that the output inductor should reach 190F/90C (inside the annealer), a thermal cut out will activate to protect the unit. If that occurs, leave the annealer turned on so the fans continue cooling. It will automatically reset after 30 minutes, once cooling is complete."
My question to the induction methodeers is this:
The output inductor (which has thermal mass) which is inside the annealer and would seem to need to be in immediate proximity to the case in order to function as intended is allowed to vary in temp from 70 deg F (ambient when you begin the annealing session) to 190 deg F (the point at which thermal protection cut off occurs). The annealing 'control' is a time and not a temperature function. How can the induced temperature of the brass not vary significantly when the temperature of the inductor is permitted to vary 120 deg F? If the ambient temperature of the 'annealing chamber' is 120 deg F hotter and the time for which the electromagnetic waves are applied does not change, simple physics (ambient heat of the inductor + electromagnetically induced heat) would indicate that the resulting temperature of the brass would be progressively higher for each successive piece of brass. The variation from piece to piece would be small but the variation from first piece to last piece of a 100 or 200 case batch could be quite large. How much higher? My proficiency in thermodynamics is not up to the task, perhaps someone else can take that on. Certainly more than that which could be achieved using Tempilaq which is advertised as +/- 1% or =?- 7.5 deg F for 750 deg F Tempilaq.
Perhaps an experiment would at least partially answer the question. Apply 760 degree Tempilaq to the cases and run cases though the induction annealer until the Tempilaq changes color or the thermal cutoff is reached. If none of them show this temperature was reached then it would seem not to be a problem.
