Patent ID: 8394212

Claim:
A high frequency induction heating treatment method employing induction heating to heat and thus quench and harden an object to be treated, comprising: a temperature controlling step of adjusting said object in temperature, and; a quench controlling step of determining when said object heated should be cooled, wherein: said temperature controlling step includes a heating step of heating said object through induction heating, a temperature measuring step involved in temperature control, of measuring in temperature a portion of said object that is heated, and a temperature adjusting step of outputting a temperature control signal, as based on information of said temperature measured, to control heating said object; and said quench controlling step includes a temperature measuring step involved in quenching, of measuring in temperature a portion located away from said portion of said object that is heated, and a heat treatment adjusting step of adjusting a heating time, as based on information of said temperature measured, and outputting a cooling start signal, wherein in said heat treatment adjusting step a diffusion length D ep of carbon is determined by: D ep =A× 2( Dt ) 1/2 where D: a diffusion constant, t: a holding time (in seconds), A: a correction coefficient; D=D 0 exp(− Q/RT ) where D 0 : an entropy term of said diffusion constant, Q: activation energy, R: a gas constant, T: absolute temperature (K); and erf ( A )=1−0.1573 C 1 /C 2 where C 1 : a solid solubility of carbon at 727° C., C 2 : a solid solubility of carbon at any temperature, and said diffusion length thus calculated is used to determine when said object should be cooled, and output said cooling start signal.