induction heating

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At work we have started to use induction heating to preheat and post heat treat weldments.  Previously we have used large propane torches or resistance heating pads.  The unit we are using is an older Miller.  If you have not seen one they are shown on the Miller site.  Search under induction heating.   The general procedure is to wrap the water cooled cables around the material then turn on the power.  The cables are like soft water hoses.   The conductor inside is much smaller than you would imagine.  The current is very high voltage and high frequency.  We are using kaowool batting for insulation.  We are learning something new each time we use the machine.  How you imagine the heat will travel through the weldment sometimes fools you.  Simple pipe joints heating is straightforward.  On irregular shapes you have to use your imagination a bit.   The rate of heating is extremely fast and efficient since you are inducing the heat in the metal.  The pulsing magnetic field near the cables causes the steel to heat up.  The hammer head was fully stress relieved at 1100 F.   The cables are some sort of high temp silicon rubber insulation.  You can touch the cables while they are carrying current.  I have not tried it while wearing a watch or ring though.... wouldn't want to try it thank you. Attached Images
Reply:Hey lotechman, so there is no additional insulation required between the cables and the piece being heated. They can have direct contact??
Reply:The cables are water cooled and rated to 500F with direct contact to the steel.  All there is is the layer of kaowool, compressed to about an inch thick.  It sorta scared me at first but I have run things up to 1100 F several times now and I expect we will be going as high as 1250 F with experience.
Reply:Kaowool is great, isn't it?Don't even think about wearing jewelery (ring,watch with a metal case or metal band, anything) around the induction heating gear. It can be really unpleasant. Something like a tounge stud wouldn't likely be a problem, since the closed paths for induced current are small.
Reply:Originally Posted by enlpck...Something like a tounge stud wouldn't likely be a problem, ...
Reply:Originally Posted by MAC702That reminds me I've been meaning to thank you for all the personal experience you bring to this website.