______________________________________________________________________________________________ Question of the Month: What is the difference between auto-tempering and self-tempering? Answer: Sometimes the terms auto-tempering and self-tempering are incorrectly used interchangeably. Here we will explore the differences in what these two terms really mean (Materials of this article have been adapted from the 2nd Edition of the Handbook of Induction Heating, […]
Article discusses unique technology that allows the replacement of carburizing with induction contour hardening for a wide range of complex-shaped components, including parts previously thought to be impossible to induction harden. This includes but not limited to spiral bevel pinions, spiral bevel ring gears, journal and differential crosses, helical bull gears, shaft helical shafts, etc. […]
There are three ways to quench gears in spin hardening applications (Ref. 1): • Submerge the gear in a quench tank. This technique is particularly applicable for large gears. • Quench “in place” using an integrated spray quench. Small- and medium-size gears are usually quenched using this technique. • Use a separate, concentric spray-quench block […]
There are four popular heating concepts used for the induction spin hardening of gears that employ encircling-type coils: the conventional single-frequency (CSFC), pulsing single-frequency (PSFC), pulsing dual-frequency (PDFC) and simultaneous dual-frequency (SDFC) concepts. All four modes can apply either a single-shot or scanning approach. Click here for more information.
The gear is induction preheated to a temperature determined by the process features, typically being 350 to 100°C below the critical temperature Ac1. The pre- heat temperature depends on the type and size of the gear, tooth shape, prior mi- crostructure, required hardness pattern, acceptable distortion, and the available power source. Usually, preheating is ac- complished […]
Gears are induction hardened by either encircling the part with a coil (so-called spin hardening) or, for larger gears, hardening them “tooth-by-tooth” or “gap-by-gap.” Article concentrates on analyzing main coil failure modes of “gap-by-gap” inductors for hardening large and medium size gears. Several case studies are discussed including degradation of laminations, copper overheating, distortion, arcing, […]
As a rule, when it is necessary to harden only the tooth tips, a higher frequency and high power density should be applied; to harden the tooth roots, use a lower frequency. A hig power density in combination with the relatively short heat time generally results in a shallow pattern, while a low power density […]
Gear performance characteristics (including load condition and operating environment) dictate the required surface hardness, core hardness, hardness profile, residual stress distribution, grade of steel, and the prior microstructure of the steel 1. In contrast to carburizing and nitriding, induction hardening does not require heating the whole gear. With induction, heating can be localized to only […]
True contour gear hardening pattern can be obtained utilizing this technology. Single-shot hardening of several powertrain components utilizing dual frequency systems dramatically minimizes distortion of induction hardened parts and provides a superior hardness pattern with favorable distribution of residual stresses.
Some induction practitioners have heard about simultaneous dual frequency gear hardening. Coil current waveform comprises two appreciably different frequencies making effect of two single frequency inverters working on the same coil at the same time.