Abstract
High frequency induction heating was applied to the partial austenitization treatment of the Interior Permanent Magnetic (IPM) rotor using Fe-17.6mass%Cr-2.0 mass%Ni-1.0mass%Al-0.5mass%C alloy with ferromagnetic ferrite (α) and M23C6 carbide structures, and high saturation magnetization (J) of 1.46T. Twelve bridges at the outer edge of the circular rotors were simultaneously heated by high frequency induction heating due to the increase in eddy current and Joule's heat at the bridges. The heat-treated bridges mainly consisted of paramagnetic retained austenite (γR) and a small amount of ferromagnetic martensite (α') phases with Vickers hardness number (Hv) of 274-309. The retained austenite fraction, XγR, at the bridges was estimated to be 0.70-0.80 from the relation among austenitization temperature, Hv and XγR. In addition, the J value at the bridges was estimated to be 0.16-0.27T from the relation between XγR and J values: J = 0.72XγR2 -2.19XγR+1.45. This estimated J value was almost consistent with the experimental value of 0.20T.
