I'm no expert, but the high frequency energy in a tig welder is only a
low power provider; just enough enegy to ionize the air in the gap
between the electrode and the work.
An induction furnace would take thousands of times more energy than
the high frequency generator of the tig welder.
Think of the energy source for an induction heater or furnace as a Radio
station's transmitter, running at frequencies usually well below the AM
broadcast band, maybe as low as 1000 cycles per second.
If I missed the point of your question, email me for more info,
William Robert wrote:
As far as my understanding goes, an induction furnace is essentially an open
ended transformer. The load (metal charge) is the secondary loop. The size
of the charge affects the coupling. Larger loads couple easier than small
There are 2 approaches to building furnaces to match the coupling of the
load. You can either vary the frequency or capacitance to balance the
A small 10 lb furnace would need very high frequencies (couple of 1000Hz) to
get enough coupling to melt the charge. A very large furnace (ie. 15 tons)
could use line frequency - 60Hz to get the same result. The coupling also
varies based on the temperature of the charge.
Most new induction furnaces use variable frequency to balance the load
because of the availability of low cost, high power SCR's.
Short of going through the calculations to balance the load/inductive
coupling/frequencies using a welder as a power source, I was wondering if
anyone has gone down this garden path or am I wasting my time?
IIRC it was MIT that was using the microwave to melt small qty. metal
samples. Could be wrong. No different than an induction furnace on the
face of it. Just transferring energy with RF. Keeping the microwave from
overloading it's own circuits was stated as a problem...but the metal
was quite well contained by the time they had it wrapped in enough
insulation to avoid losing all the heat from radiation.
Or more conducive to angry relations with neighbours from causing RF
interference on their domestic (or business) electronics!
You could be causing aggro to everything from phones, radio, tv, satellite
reception etc, not to mention mains-borne interference getting into their house
wiring. Then you're into their PC, their hifi - the lot!
Not a good road to go down.
I have had some objects cast. The foundry that cast it for me used
induction furnaces. They could melt one ton of stainless steel in 20
I became interested and, with a bit of research, I built a small (very
small) induction furnace that will heat a small nail red hot. It uses an
18kv neon sign transformer, spark gap, a large voltage capacitor and a coil
of wire. The nail is inserted into the coil and in couple of seconds it is
red hot. This is not very optimal. Solid state switching and frequency
control would be the best. I have not continued with my experments.
I started with info from this page http://www.powerlabs.org/indheating.htm
I wonder if an induction rice cooker could be modified to serve as an
induction forge ?
Cool, thanks for the link.
I am actually debating on using a regular arc welder and a graphite crucible
to melt a small charge of iron. Using a copper watercooled coil can become
a pain, especially if it melts!
I do not think that the welder would work for the power supply of an
induction furnace. Arc furnaces use water cooled copper electrodes; a DC
arc welder or tig welder may work assuming it was capable of 100% duty
cycle. There would need to be some mechanism to maintain the arc.
induction heating starts with magnetic flux.
The flux flexes the atomic state and heats the metal.
One wants high current concentrated into a small area - using a flux
if possible or just a good tight design.
High voltage isn't needed. Remember the danger - but car batteries
can deliver high currents. They can explode when rapid discharging
and any ring on your finger or watch - that gets across the two wires -
THere are some really scary films on safety - melted rings/fingers
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer firstname.lastname@example.org
Copper coils and a few shunts work nicely.
I had a cool safety film showing what happens when molten metal and water
come into contact. 1kg molten Al was dropped into a tank of water - kaboom,
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.