Patent ID: 6940056

Claim:
A method of induction heat treatment, comprising the steps of: selecting an article for heat treatment comprising a metal wall having an upper hub portion, a lower hub portion, a bell-shaped portion that is located between the upper hub portion and the lower hub portion and a longitudinal axis extending through each of the upper hub portion, lower hub portion and bell-shaped portion, the bell-shaped portion having a bell-shaped outer surface, an inner surface and a plurality of windows extending from the outer surface to the inner surface; selecting an induction coil comprising a hollow metal channel having a first termination portion, a second termination portion and a semi-rectangular inductor portion that is operably connected to the first termination portion and the second termination portion, said semi-rectangular inductor portion having a first semi-rectangular coil portion and a proportionally smaller second semi-rectangular coil portion; wherein the semi-rectangular inductor portion is adapted to receive the article and apply a plurality of magnetic fields to a heat treatment portion of the article; placing the article within the inductor portion of the induction coil; rotating the article within the induction coil at a selected speed; energizing the induction coil to apply the magnetic fields and produce induction currents within the heat treatment portion of the article for a time sufficient to induce heating of the heat treatment portion to a heat treatment temperature (T H ) to at least a selected case depth; and cooling the heat treatment portion of the article to a temperature (T C ) to the selected case depth.