Induction heating: facts or sales talk? I need information!
Induction heating: facts or sales talk? I need information!
(OP)
I've been invited by a sales person to check out the new setup of a welding program, using induction heating.
Induction heating is new to the firm I work for and for me personally.
I vaguely know the principles, but not much more than that.
We always use flames (oxy/acetylene) and ceramic carpets (resistance heating) for preheating.
The guy baffled me today with eddy currents and Faucoult currents and molecular movement and such, so can anyone point me to somewhere where all of this is properly explained, preferably a bit more scientific than good ol' google seems to find?
Another question: is it true that, when a part is heated using induction, it keeps the heat "in itself" for longer than if it was preheated (to the same temp.) using flames or ceramics? I find this hard to believe, however he really tried to persuade me that is't like that...
Any insights much appreciated...
Induction heating is new to the firm I work for and for me personally.
I vaguely know the principles, but not much more than that.
We always use flames (oxy/acetylene) and ceramic carpets (resistance heating) for preheating.
The guy baffled me today with eddy currents and Faucoult currents and molecular movement and such, so can anyone point me to somewhere where all of this is properly explained, preferably a bit more scientific than good ol' google seems to find?
Another question: is it true that, when a part is heated using induction, it keeps the heat "in itself" for longer than if it was preheated (to the same temp.) using flames or ceramics? I find this hard to believe, however he really tried to persuade me that is't like that...
Any insights much appreciated...





RE: Induction heating: facts or sales talk? I need information!
http://www.manningsusa.com/industries.html
RE: Induction heating: facts or sales talk? I need information!
http://www.uie.org/webfm_send/441
RE: Induction heating: facts or sales talk? I need information!
If you consider the "part temperature" to be the surface temperature, then yes. Think of it as microwaving compared to toasting. Which are you going to use to cook the inside of a baked potato?
RE: Induction heating: facts or sales talk? I need information!
RE: Induction heating: facts or sales talk? I need information!
thanks for the pdf, I've printed it and will have a look at it this weekend.
@ 1gibson: when I said 'temp', I ment core temp, as of course surface temp isn't representable for a workpiece.
I rephrase: when 2 identical parts are fully heated to a certain temp, using flames for one part and induction for the other,
and conditions are the same (same ambient temp, no forced cooling, ...), will the induction heated part be warmer for a longer time?
I find this hard to believe, however the sales guy tried to explain this with molecular movements and a lot of technical verbiage but I am still not impressed.
RE: Induction heating: facts or sales talk? I need information!
and conditions are the same (same ambient temp, no forced cooling, ...), will the induction heated part be warmer for a longer time?"
No. If the internal temperatures are the same, the parts will cool at the same rate.
RE: Induction heating: facts or sales talk? I need information!
A flame-heated part will (usually) get passed through the flame, or the flame passed on over the outside surface, so areas of the outside are getting unevenly heated and cooled off at various times as the whole part gets up to temperature. An air oven, uniformly raised to some delta T over the desired final part internal temperature, will more uniformly raise temperatures. No part of the whole assembly can get higher than the air temperature - which can be regulated much smoother than an open flame that (by definition) is much, much higher than the surface.
RE: Induction heating: facts or sales talk? I need information!
Imagine a railroad track. That's similar to an I-beam, only much heavier.
When we need to (repair / clad) weld the upper surface (the "flange"?), we heat the middle part (the "web"?) until the surface of the contact area (with the train wheels) has the requested temp.
That means that the heat went upwards, coming from below.
The temp we measure at the top, is (only slightly) lower (due to losses of radiation) than the core temp.
Thus, the exact opposite of regular procedures.
But, as I understand the responses I got here, the sales talk that the railroad track will keep the heat longer than using flames, isn't true at all. There is no different cooling down curve for the metal, depending on the way you heat it up.
Thanks for your thoughts on this!
RE: Induction heating: facts or sales talk? I need information!
RE: Induction heating: facts or sales talk? I need information!
RE: Induction heating: facts or sales talk? I need information!
My point was that, for the same internal temperatures (perhaps I should have said bulk-averaged temperatures :), the flame-heated part won't cool faster because of some residual or latent heat produced by the induction process. I.e., an effect like superheating of water due to rotational frequency excitation of the water molecules by a microwave oven, does not occur in induction heating of metals. That I know of.
RE: Induction heating: facts or sales talk? I need information!
RE: Induction heating: facts or sales talk? I need information!