Case Hardening: Solid vs Hollow Shafts

Induction surface (case) hardening of hollow shafts has unique features compared with hardening of solid shafts. With solid shafts, the core temperature typically does not rise significantly during heating. The relatively cold core compliments spray quenching by increasing the cooling intensity of shaft surface (cold-sink effect). By comparison, with hollow shafts, the cold-sink effect is dramatically reduced or even can be reversed by reducing cooling severity during quenching. Numerical computer modeling helps reveal subtleties of induction case hardening by evaluating the shaft’s thermal conditions that are difficult to see or to measure.

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