Design for a small shop 240-volt induction heater?
At Instructables, I found a project design that looks pretty viable, although it would be a lot of work.

This design is for a system nominally rated around 10 kilowatts at 50 amps, so it would potentially be viable on a dryer circuit. Alternatively it could be amped up to 80 amps or more by connecting to the house mains on a dedicated, high-amperage line. By doing this 15kw is probably possible.