Induction furnace

[Dane Bear]

Does anyone have any ideas on how to build an induction heat treat furnace? I am needing one for parts up to 8" wide 2" thick and 12" long and temperatures to 2000 F.

[ftransform]

There are several out there. Your best bet is the instructibles one because its pretty much all laid out with minimum design work required.

- pretty detailed documentation but expect alot of leg work, I think he sells plans/kits
http://hackaday.com/2010/06/04/1000w-induction-heater/

This one is small/prototype model I think, should be quick to put together but not for what you want, maybe as a introduction?
http://hackaday.com/2011/10/27/a-simple-induction-heater/

finally the one you want, with most of the design work done (and its powerful too)
http://www.instructables.com/id/30-kVA-Induction-Heater/?ALLSTEPS
I think it out performs the first link and its completely documented. The approach to solving the problem is different though, I think the first one has a bit more analog trickery in it.

[G7PSK]

If you need one for serious work it is probably best to buy one.

http://www.ebay.com/itm/15KW-30-80KHz-Mid-Frequency-Induction-Heater-Heating-Melting-Furnace-System-/190554903261

http://www.machinetools.com/us/listings/type/1664?condition=used

[Dane Bear]

I am looking for more powerful units (800 amps or so) because I am hardening sections of steel that weigh fifty or so pounds.

[codeboy2k]

I can make you a unit that draws 800A but cannot melt solder. 

Don't be fooled by current drawn = 800A; look only at the Watt ratings, then for the most efficiency choose the one that uses the least current at the same Wattage.

I hate the marketing of vacuum cleaners, 10A, 12A, 14A, it's all meaningless.

[Jay_Diddy_B]

Hi,
To the original poster.

I worked in induction heating for short period in the early 80s. I worked for a company called Radyne, which is now part of the inductotherm organization.
The fundamentals for induction have not changed since then:

1) Good conductor like copper, gold, silver are difficult heat. This is because they have low resistance.

2) High frequencies, around 50kHz are used for small components like the teeth on a saw blade. Power levels 10-20kW

3) Medium frequencies 10-20kHz are typically used for something like an alternator shaft, say 0.5 inches (1.25cm) diameter. Power levels 50kW

4) Lower frequencies are used for melting furnaces and billet feeders. Power levels 300kW to 3MW.

5) The higher the frequency the smaller the penetration of the heating, this comes from the skin depth.

6) For hardening applications, power density is important. You want to be able to heat the material fast enough to change the properties on the outside of the material without changing the properties of the inside.

Have a look at this website:

http://www.inductotherm-hwt.co.uk/content/home/#start

And this brochure:

http://inductotherm-hwt.co.uk/assets/content_pages/352593555_IHWT_Power_Supply_Brochure.pdf

For the size of material you are talking about, I suspect that your best plan is to outsource this to a company that specializes in this.

Good luck !!

Jay_Diddy_B

[Dane Bear]

Cool. I didn't know there were so much available for furnaces. I have a Lucifer electric furnace, but it is slow, and parts have to "soak" for a long time. I own a Tool and Die business, and sometimes we need parts treated the same day. Otherwise, we do outsource parts, but you never know what kind of quality you are really getting. Surface hardness may be ok, but if not allowed to core austenitize, parts can be substandard.

[DenzilPenberthy]

Excellent post Jay.

For my tuppence worth, I'd add  the book 'Foundations of Electroheat' by A. C. Metaxas and a warning to take off your wedding ring before you play with these things if you want to continue having a slightly higher than average number of fingers!