Induction Heater / Forges

J

JMJones

Joined
Jul 14, 2010
Messages
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I was looking around for an induction forge and found some on ebay and other places for about a grand. I remember them being quite a bit more expensive when I looked at them several years ago, like three or four grand. Does anyone have any experience with these cheaper models.
Example
http://www.ebay.com/itm/15KW-30-80-...085074?hash=item35c9b0f892:g:ZEsAAOSwknJXx~Id

Are these the right size for forging steel efficiently or doing crucible steel ingots?

Thanks

John
 
Using 30 kHz to 80 kHz results in a skin depth of 7 to 11 MICROMETERs of penetration. What that means is that the surface 10 micrometers (let's say) will actually heat up. In order to get the core hot, you will probably need to wait for thermal conduction. This is assuming that the alternating magnetic field won't continue to penetrate the material as the outer layer becomes non magnetic.
 
In the manual, it talks about heat treating sections over 2.5mm.
 
If the outer surface is no longer magnetic, would the magnetic field just penertate deeper & deeper until entirely heated ?
 
Thinking about this again, heating past the curie point of iron doesn't make it non magnetic, it simply removes its PERMANENT magnetism. When it is heated up via induction, the resistance should increase.

See the Temperature Coefficient (positive with increase in temperature)
http://www.engineeringtoolbox.com/resistivity-conductivity-d_418.html

Looking at the skin effect formula (https://en.wikipedia.org/wiki/Skin_effect#Formula), the depth increases with an increase in the electrical resistivity of the piece. I think that as it gets hotter, it should theoretically be easier to penetrate deeper into the core of the material but in any case, if that doesn't work, good ole thermal conduction will do the trick.

It should be a feasible way to heat up a piece rapidly for forging. How It's Made showed this company making chisels by stamping and pressing an induction heated piece. (https://www.youtube.com/watch?v=3JQFA0ECDKM)
 
They can definitely heat through to the core of the work piece. At one shop I used to work in, whenever we silver brazed carbide faces to tooling we used a small induction heater to do it. We would take a snip of leaf solder, place it between the two fluxed components then clamp them together with a vise grips or similar, stick them in the induction ring until you felt the clamp relieve or saw the braze sweat out.

Really neat and clean way to do that kind of thing. If you took them apart you could see the braze had sweat entirely through the joint, not just the edges.
 
My thoughts on that unit is it looks a lot like a cobbled together Chinese machine. Everything from the wording, the company name, to the "free gift" of a piece of copper tubing suggest the same. The location listed is one associated with Chinese imports. The shipping charge also indicates overseas source. Also, no where in the info do they suggest it will work for forging. You also have to buy their water chiller to use with the induction heater.
 
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