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Apparatus and method are provided for inductively heat treating a circular surface of annular workpieces where at least one inductor pair is used to perform a scan induction heat treatment of the circular surface. Controlled movement of the inductors and application of quenchant is provided particul

Apparatus and method are provided for inductively heat treating a circular surface of annular workpieces where at least one inductor pair is used to perform a scan induction heat treatment of the circular surface. Controlled movement of the inductors and application of quenchant is provided particularly at the initial and final heat treatment locations on the circular surface to enhance metallurgical uniformity of the annular workpiece at these locations. In combination with controlled movement of the inductors, a simultaneous power-frequency control scheme can be applied to the inductors during the heat treatment process.

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1. A method of electric induction heat treatment of at least one circular surface of an annular workpiece, the method comprising the steps of: positioning side-by-side a first and a second inductor at an initial position adjacent to the at least one circular surface, the initial position located wit

1. A method of electric induction heat treatment of at least one circular surface of an annular workpiece, the method comprising the steps of: positioning side-by-side a first and a second inductor at an initial position adjacent to the at least one circular surface, the initial position located within an oscillatory arc zone of the at least one circular surface, the oscillatory arc zone having a first and a second arc boundary;supplying an oscillatory zone alternating current to the first and second inductors while circumferentially moving side-by-side the first and second inductors repeatedly between the first and second arc boundaries for a pre-heat period of time while adjacent to the at least one circular surface;supplying a steady state heat treatment power having a steady state power magnitude and frequency to the first and second inductors while separating the first and the second inductors in the oscillatory arc zone by moving the first inductor in a first circumferential direction adjacent to the at least one circular surface to a first inductor end steady state heat treatment position less than 180 degrees opposite the initial position at a steady state scan rate, and by moving the second inductor in a second circumferential direction adjacent to the at least one circular surface to a second inductor end steady state heat treatment position at the steady state scan rate, the second circumferential direction opposite to the first circumferential direction;directing a first quenchant spray from a first quench apparatus to impinge on a first inductor heated region of the at least one circular surface heated by the first inductor as the first inductor moves in the first circumferential direction to the first inductor end steady state heat treatment position after the first inductor separates from the second inductor by a spray interference distance, and directing a second quenchant spray from a second quench apparatus to impinge on a second inductor heated region of the at least one circular surface heated by the second inductor as the second inductor moves in the second circumferential direction to the second inductor end steady state heat treatment position after the second inductor separates from the first inductor by the spray interference distance;removing the steady state heat treatment power from the first inductor and terminating the first quenchant spray after the first inductor completes heat treatment at the first inductor end steady state heat treatment position;moving the second inductor in the second circumferential direction after the second inductor completes heat treatment at the second inductor end steady state heat treatment position to the end of an extended end scan region to heat treat the extended end scan region at an end of heat treatment scan rate faster than the steady state scan rate and at an end of heat treatment power magnitude and frequency; anddirecting the second quenchant spray to impinge on the extended end spray region by alternatively repositioning the second quench apparatus while the second inductor is at the end of the extended end scan region or moving the second quench apparatus through the extend end spray region. 2. The method of claim 1 wherein the step of supplying the oscillatory zone alternating current to the first and second inductors is initiated when the first and second inductors are located side-by-side at the first or second arc boundary. 3. The method of claim 1 wherein the separation of the first and second inductors in the oscillatory arc zone is initiated in the center of the oscillatory arc zone. 4. The method of claim 1 wherein the end of heat treatment frequency is greater than the steady state frequency, and the end of heat treatment power magnitude is greater than the steady state power magnitude. 5. The method of claim 1 wherein the step of supplying the oscillatory zone alternating current further comprises supplying the oscillatory zone alternating current at a pre-heat frequency less than the steady state frequency, and at a pre-heat power magnitude less than the steady state power magnitude. 6. The method of claim 5 wherein the end of heat treatment frequency is greater than the steady state frequency, and the end of heat treatment power magnitude is greater than the steady state power magnitude. 7. A method of electric induction heat treatment of at least one circular surface of an annular workpiece, the method comprising the steps of: positioning side-by-side a first and a second inductor at an initial position adjacent to the at least one circular surface, the initial position located within an oscillatory arc zone of the at least one circular surface, the oscillatory arc zone having a first and a second arc boundary;supplying an oscillatory zone alternating current to the first and second inductors while circumferentially moving side-by-side the first and second inductors repeatedly between the first and second arc boundaries for a pre-heat period of time while adjacent to the at least one circular surface;supplying a steady state heat treatment power having a steady state magnitude and frequency to the first and second inductors while separating the first and the second inductors in the oscillatory arc zone by moving the first inductor in a first circumferential direction adjacent to the at least one circular surface to a first inductor end of steady state heat treatment position less than 180 degrees opposite the initial position at a steady state scan rate, and by moving the second inductor in a second circumferential direction adjacent to the at least one circular surface to a second inductor end steady state heat treatment position at the steady state scan rate, the second circumferential direction opposite to the first circumferential direction;directing a first quenchant spray from a first quench apparatus to impinge on a first inductor heated region of the at least one circular surface heated by the first inductor as the first inductor moves in the first circumferential direction to the first inductor end steady state heat treatment position after the first inductor separates from the second inductor by a spray interference distance, and directing a second quenchant spray from a second quench apparatus to impinge on a second inductor heated region of the at least one circular surface heated by the second inductor as the second inductor moves in the second circumferential direction to the second inductor end steady state heat treatment position after the second inductor separates from the first inductor by the spray interference distance;removing the steady state heat treatment power from the first inductor and terminating the first quenchant spray after the first inductor completes heat treatment at the first inductor end steady state heat treatment position;moving the second inductor in the second circumferential direction after the second inductor completes heat treatment at the second inductor end steady state heat treatment position to the end of an extended end scan region to heat treat the extended end scan region at an end of heat treatment scan rate faster than the steady state scan rate and at an end of heat treatment power magnitude and frequency;moving the second inductor in the second circumferential direction after the second inductor completes heat treatment to the end of the extended end scan region to a distance beyond the end of the extended end spray region so that the second quenchant spray impinges on the extended end spray region. 8. The method of claim 7 wherein the step of supplying the oscillatory zone alternating current to the first and second inductors is initiated when the first and second inductors are located side-by-side at the first or second arc boundary. 9. The method of claim 7 wherein the separation of the first and second inductors in the oscillatory arc zone is initiated in the center of the oscillatory arc zone. 10. The method of claim 7 wherein the end of heat treatment frequency is greater than the steady state frequency, and the end of heat treatment power magnitude is greater than the steady state power magnitude. 11. The method of claim 7 wherein the step of supplying the oscillatory zone alternating current further comprises supplying the oscillatory zone alternating current at a pre-heat frequency less than the steady state frequency, and at a pre-heat power magnitude less than the steady state power magnitude. 12. The method of claim 11 wherein the end of heat treatment frequency is greater than the steady state frequency, and at the end of heat treatment power magnitude greater than the steady state power magnitude. 13. A method of electric induction heat treatment of at least one bearing race having an inner diameter of at least one meter, the method comprising the steps of: positioning side-by-side a first and a second inductor at an initial position adjacent to the at least one bearing race, the initial position located within an oscillatory arc zone of the at least one bearing race, the oscillatory arc zone having a first and a second arc boundary;supplying an oscillatory zone alternating current to the first and second inductors while circumferentially moving side-by-side the first and second inductors repeatedly between the first and second arc boundaries for a pre-heat period of time while adjacent to the at least one bearing race;supplying a steady state heat treatment power having a steady state power magnitude and frequency to the first and second inductors while separating the first and the second inductors in the oscillatory arc zone by moving the first inductor in a first circumferential direction adjacent to the at least one bearing race to a first inductor end steady state heat treatment position less than 180 degrees opposite the initial position at a steady state scan rate, and by moving the second inductor in a second circumferential direction adjacent to the at least one bearing race to a second inductor end steady state heat treatment position at the steady state scan rate, the second circumferential direction opposite to the first circumferential direction;directing a first quenchant spray from a first quench apparatus to impinge on a first inductor heated region of the at least one bearing race heated by the first inductor as the first inductor moves in the first circumferential direction to the first inductor end steady state heat treatment position after the first inductor separates from the second inductor by a spray interference distance, and directing a second quenchant spray from a second quench apparatus to impinge on a second inductor heated region of the at least one bearing race heated by the second inductor as the second inductor moves in the second circumferential direction to the second inductor end steady state heat treatment position after the second inductor separates from the first inductor by the spray interference distance;removing the steady state heat treatment power from the first inductor and terminating the first quenchant spray after the first inductor completes heat treatment at the first inductor end steady state heat treatment position;moving the second inductor in the second circumferential direction after the second inductor completes heat treatment at the second inductor end steady state heat treatment position to the end of an extended end scan region to heat treat the extended end scan region at an end of heat treatment scan rate faster than the steady state scan rate and at an end of heat treatment power magnitude and frequency; anddirecting the second quenchant spray to impinge on an extended quench region by repositioning the second quench apparatus while the second inductor is at the end of the extended end scan region. 14. The method of claim 13 wherein the step of supplying the oscillatory zone alternating current to the first and second inductors is initiated when the first and second inductors are located side-by-side at the first or second arc boundary. 15. The method of claim 13 wherein the separation of the first and second inductors in the oscillatory arc zone occurs in the center of the oscillatory arc zone. 16. The method of claim 13 wherein the end of heat treatment frequency is greater than the steady state frequency, and the end of heat treatment power magnitude is greater than the steady state power magnitude. 17. The method of claim 13 wherein the step of supplying the oscillatory zone alternating current further comprises supplying the oscillatory zone alternating current at a pre-heat frequency less than the steady state frequency, and at a pre-heat power magnitude less than the steady state power magnitude. 18. The method of claim 17 wherein the end of heat treatment frequency is supplied at a frequency greater than the steady state frequency, and the end of heat treatment power magnitude is greater than the steady state power magnitude. 19. A method of electric induction heat treatment of at least one bearing race having an inner diameter of at least one meter, the method comprising the steps of: positioning side-by-side a first and a second inductor at an initial position adjacent to the at least one bearing race, the initial position located within an oscillatory arc zone of the at least one bearing race, the oscillatory arc zone having a first and a second arc boundary;supplying an oscillatory zone alternating current to the first and second inductors while circumferentially moving side-by-side the first and second inductors repeatedly between the first and second arc boundaries for a pre-heat period of time while adjacent to the at least one bearing race;supplying a steady state heat treatment power having a steady state magnitude and frequency to the first and second inductors while separating the first and the second inductors in the oscillatory arc zone by moving the first inductor in a first circumferential direction adjacent to the at least one bearing race to a first inductor end steady state heat treatment position less than 180 degrees opposite the initial position at a steady state scan rate, and by moving the second inductor in a second circumferential direction adjacent to the at least one bearing race to a second inductor end steady state heat treatment position at the steady state scan rate, the second circumferential direction opposite to the first circumferential direction;directing a first quenchant spray from a first quench apparatus to impinge on a first inductor heated region of the at least one bearing race heated by the first inductor as the first inductor moves in the first circumferential direction to the first inductor end steady state heat treatment position after the first inductor separates from the second inductor by a spray interference distance, and directing a second quenchant spray from a second quench apparatus to impinge on a second inductor heated region of the at least one bearing race heated by the second inductor as the second inductor moves in the second circumferential direction to the second inductor end steady state heat treatment position after the second inductor separates from the first inductor by the spray interference distance;removing the steady state heat treatment power from the first inductor and terminating the first quenchant spray after the first inductor completes heat treatment at the first inductor end steady state heat treatment position;moving the second inductor in the second circumferential direction after the second inductor completes heat treatment at the second inductor end steady state heat treatment position to the end of an extended end scan region to heat treat the extended end scan region at an end of heat treatment scan rate faster than the steady state scan rate and at an end of heat treatment power magnitude and frequency; andmoving the second inductor in the second circumferential direction after the second inductor completes heat treatment to the end of the extended end scan region to a distance beyond the end of the extended quench region so that the second quenchant spray impinges on an extended end spray region. 20. The method of claim 19 wherein the step of supplying the oscillatory zone alternating current to the first and second inductors is initiated when the first and second inductors are located side-by-side at the first or second arc boundary. 21. The method of claim 19 wherein the separation of the first and second inductors in the oscillatory arc zone occurs in the center of the oscillatory arc zone. 22. The method of claim 19 wherein the end of heat treatment frequency is greater than the steady state heat treatment frequency, and the end of heat treatment power magnitude is greater than the steady state heat treatment power magnitude. 23. The method of claim 19 wherein the step of supplying the oscillatory zone alternating current further comprises supplying the oscillatory zone alternating current at a pre-heat frequency less than the steady state heat treatment frequency, and at a pre-heat power magnitude less than the steady state power magnitude. 24. The method of claim 23 wherein the end of heat treatment frequency is supplied at a frequency is greater than the steady state heat treatment frequency, and at the end of heat treatment power magnitude greater than the steady state heat treatment power magnitude.