The hardening lager should be distribution along the profile for raising the fatigue strength of induction hardening gears

but it is difficult to get this type of distribution profile by the traditional induction hardening method.After years of efford

a SDF（Simultaneous Dual Frequency） induction hardening process is studied out and a corresponding set of equipment has been also developed

which would improve the induction hardening technology of gears to a new level.