Induction heating

Certainly. You could do it with a single turn and scan progressively or multi-turn and heat statically. Face hardening of valve faces or cams on a cam shaft are examples of it being done commercially. In those cases they achieve over 850 C. In your case you would need only a few watts. Obviously you must insulate the wire from the bar.

This is really an engineering question - but ultimately, it comes down to two questions:

1. What is the impedance of the system you propose - and is it similar to the impedance that the electronics was designed for?
2. Is the power that the electronics generates sufficient to heat the rebar (that really depends on the mechanism for cooling the rebar... if it's in still air, it probably won't lose a lot of heat when it's only 10°C hotter than the environment).

The key here is that most rebar is ferromagnetic - which means that the skin effect is very strong, and the RF current will flow in just the surface so that the impedance is quite high. But without a lot more details, one cannot say anything with certainty. And once you have the details, you're firmly in engineering territory.