Induction heating uses a radio frequency signal to induce currents or magnetic effects in the target metal. The magnetic hysteresis in magnetic metals like iron generate heat when exposed to such RF magnetic fields. And eddy currents in these materials also heat up the metal. The trouble is, none of this helps very much with copper. Copper is not magnetic, so it will not have magnetic hysteresis heating. And it has very low resistivity, so it will not generate much heat from eddy currents - no more so than the copper coils generating the RF field in the first place. So unless your induction coils are made of superconducting materials, your coils will get as hot as the target metal. You might as well just use straight conduction heating by touching the target metal with a hot conductor - just like a soldering iron. Induction heating is not well-suited to heating copper.