Induction Annealing vs. Gas-Fired Furnaces

Hello MechMatt.

A request for helpful references and a thoughtful posting that indicates your personal thought process and insight is always welcome. Asking to be spoon fed answers by lazy people is not.

Try this link:

http://www.ajaxtocco.com/default.asp?ID=2

Problem with Induction for annealling is time at temperature and atmosphere interactions. And penetration in very thick sections.

Personally, I believe induction is an optimum process for quench and tempering bar parts; I don't see it for anneal or normalize as the time to cool is so short that essentially an air quench happens in carbon and alloy grades. Its also ideal for putting a case on shallow hardening bars/parts as well, without all that messy diffusion business... as in carburizing. But as a bar guy, I could be successfully prosecuted for lack of imagination.

There are two t's involved, Temperature and Time. While you correctly point out the energy savings from induction rather than furnace processes, the issue of time to austenitize, and the effects of atmosphere on the workpiece during that time are problematic. My two cents.

PS As far as I know every half shaft on every front wheel drive car that I have supplied steel to has been induction heat treated; also many gears we've been supplier on.

go back to your hysteresis curve: relaxation, recrystalization, grain growth. And then lay out in parallel time Chemical activity in air at temperature...

your idea of "latent crush zones" is indeed novel; how do you propose to maintain mechanical properties to maintain engine safely securely in proper locus prior to crash? I am not aware of a method to use induction to create an anisotropic difference in the material. So if you use induction to lower say yield strength; the material will be lower yield strength as processed, not "latently triggerable," if you get my drift.

Good thinking. Now think of bar applications for this technology...

milo

Many many years ago I was peripherally involved with an induction process for making cross-bars for high power traction motors. This involved annealing copper bars to be able to cross and shape them for favorable electrical characteristics on the rotors of large DC motors. This was over 20 years ago and my memory is foggy about details but I do recall the annealing process allowed faster production and higher quality. (That is before I buggered things up with my lack of understanding how aggressive DI water is, . . . but that is a different story.)

DI water- OH Sh*T!!!

HA.. I think we all have a similar story to tell Reid. Thanks for sharing a glimpse at yours.

milo

I think as long we all realize we put on our pants one leg at a time, we get along quite well!

I have completed several projects using induction for PWHT and pre-weld & post-weld annealing.

Problems with Induction is control: It takes more skill to get proper control top, bottom and sides, different thickness requires adjusting the coils to provide better control.

Different white steels have more or less ferrite iron and react in unexpected ways.

You need a machine for each weld.

With combustion or resistance heating you have direct control of each zone.

I have a big project coming up annealing H800 but will have several machines for control of each weld. The problem is the rapid cooling required. The coils have to be loosened, moved off the insulation and the insulation stripped and forced cooling air with a water mist applied to the weld.

You should check out Millers induction machines along with their ads.

Thanks everyone for the excellent suggestions on resources and applications. I will be looking into them in the next few days, now that I have come out of midterm season...

This thread is still active, so please feel free contribute any new thoughts!

Thanks again,

-MechMatt

Thanks everyone for the great tips. I presented my findings today, and submit my paper tomorrow. The professor for the course is active in the open-source community, and decided on a new format for presenting our research: a website called Appropedia, which puts an 'appropriate technologies' twist on Wikipedia. All articles are free of copyright (although some references/sources may not be), and anyone can post. My paper can be found at: http://www.appropedia.org/Induction_Annealing. I recommend anyone thinking about induction heating processes at all (not just induction annealing) to take a look at my compilation of research. A very interesting technology. My favourite appication is 'levitation melting' (see http://www.youtube.com/watch?v=_uHoZI-ZWyE for a demo) where a metal object is suspended in air (supported by the magnetic field), and melted to a molten blob in mid air. Pretty cool if you ask me...

Once again, thanks for the help and advice. To our American friends, enjoy your holiday weekend.

Cheers,

-MechMatt