Below is a list of Induction Heat Treating manufacturers from LONDONDERRY, New Hampshire. Induction heat treating uses induction heaters to perform the heat treating process. Induction heaters use electricity to run an AC, or alternating current, through a coil in order to heat various metals. Induction heat treatment, like other forms of heat treating is a process used to harden or soften metal by heating or cooling until it reaches the desired level of hardness.