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I was cruising youtube, and saw quite a few video's where a person would insert an item, which would be brought to yellow heat in a few seconds.. Is there a down side to using something like this for blacksmithing purposes? would the enviorment be oxidizing? carburizing? are there any dangers surrounding it, and how hard would it be to craft up a small one? I dont really understand it fully, but it sounds like they are just running a current through copper tubing, which creates a magnetic feild thus heating the metal somehow..

so ya, any possibilities?

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a lot of effort for a device with a very specialized heating potential
basically X length of some given cross section, reheating odd shapes becomes problematic
dimension flexibility isnt very cost effective

environmental controls could be whatever you want with an additional step in complexity, natively the rapid heating means less oxygen exposure

if your working a specific dimension again and again it might make sense

Induction heating
Induction furnace
High Frequency Induction Heating
Induction Heating - Amps, Volts, and Watts
Crucibles for Induction Melting

note magnetic fields obey the inverse square law the larger the area you have to heat (flexible space) the stronger the field strength and higher the energy cost will be, in addition exposure to heightened electromagnetic radiation at those frequencies is arguably hazardous while shielding is relatively easy its yet another level of complexity. Electromagnetic interference might be an issue with susceptible devices depending on how close they are.

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Traditional induction heating is generally not cost effective for heating complex, variable geometry, but some new types of induction heating can effectively work like a very low frequency microwave... with the induction heating power supply tuning itself to the load that is inserted. Given the high power and a bit of saturation time, a piece can be heated without gradients... or if desired, selectively heated with an electromagnetic wand. Some companies sell power supplies that allow the user to wind their own coils to suit any geometry. iTherm Technologies - Revolutionizing Induction Heating

As far as the efficiency goes, it is more efficient than gas, hands down. If there is no load present in the coil's field, there is little loss of energy (as there is nothing to heat) and the only energy disipated is from the coil and power supply switches.

Industrial heating recently published an article I wrote on such systems...
Embedded High-Power-Density Heating - Feature Article - Industrial Heating Not exacty what was described above, but the basic technology is the same.

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Induction heating is indeed the most effeicient heating method in a production shop. I have worked around these things for about 24 years. The speed and uniforminty is amazing. The big industrial machines need tuning to match the parts and the coils get complex and expensive. There is also the complexity and cost of cooling. The coils are water cooled, and in an industrial machine usually an evaporative cooling tower is needed.

In the small blacksmith size machines, the cooler is simple. The machine self adjusts frequency to match the billet. The coils are would from soft refrigeration copper.

If used in a small one man production shop on runs of a few hundred parts, I would think pay of would be quick, probably 6 months to a year.

Did some research and testing with Guass meters and the fields around the large industrial machines are above the limits set by the makers of medical devices like pacemakers. But then simple welding machines have the same issue.

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I was initially discouraged from trying induction heating when I first thought of using it for small shop metal heating years ago. I built and initially tested a converted automobile alternator to use it's 3 phase output without rectification, and while the AC output was a great frequency for through heating, max about 10 kilocycles per second, the transformers and coils required made the experiment unpractical.
Fast forward to the solid state modern electronic inverters... the initial units looked great and the phase locked loop frequency adjustment made them more practical, but the cost was HIGH. Now they are much more affordable.
The other knocks on them, which also kept me from trying them, was the engineering communities comments about efficiency and localized heating. While the mismatch of coil shape to the end product may be very important in an industrial application, it is much less so for small shop practice. A properly matched coil may heat a shape to useful temperatures in 3.155 seconds.... if mine takes 10 or 12 I don't mind. If the transfer efficiency is 89% for a properly matched coil and mine is 25% but still gets to the same temperature I'm down with that also. Building a coil can be done mathematically and my first efforts were calculated using some freeware I found to match the inductance of the factory coil. I have since become more empirical. I measure the coil that I make with the frequency meter in my Digital VOM, and if it falls within the range of the operating frequency of my heater I leave well enough alone.
It is certainly true that a coil may only heat a 3/4" length of a piece of 5/8" round to forging temperature, but it is equally true that by moving the piece back and forth through the coil that I could heat a 6" length as well, sort of like what would happen if you were heating a rod with a rosebud torch. And while less efficient, you can heat a piece of stock by placing it next to the coil in stead of thru it. To get a mental image of what I'm saying remove your ring from your finger and balance it on it's side on your finger. This is not as quick to heat as placing the stock through the coil but it does heat it.
Yes they are expensive to purchase, but in operation they draw very little power unless the unit is actually heating. I'd have to ask my wife about the power bills, but if we are billed at about 10 cents per Kilowatt hour, my 18KW heater uses about $2 running for an hour without turning off... my duty cycle isn't that high.
Paul

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I was cruising youtube, and saw quite a few video's where a person would insert an item, which would be brought to yellow heat in a few seconds.. Is there a down side to using something like this for blacksmithing purposes? would the enviorment be oxidizing? carburizing? are there any dangers surrounding it, and how hard would it be to craft up a small one? I dont really understand it fully, but it sounds like they are just running a current through copper tubing, which creates a magnetic feild thus heating the metal somehow..


so ya, any possibilities?


I know of at least three one person shops using induction forges and can say hands down that they are practical and effective for a small shop. Cost for doing small production runs are a fraction of fuel costs to heat any other way.. The equipment is relatively inexpensive and the units I am aware of have functioned flawlessly... im sure Grant will see this post and have a few things to say. The units he imports are really impressive and someday when I start making money again i plan to own one..

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