Induction hardening is a form of heat treatment in which a metal object or part is heated by induction heating and then quenched. The quenched metal undergoes a martensitic transformation, increasing the hardness and brittleness of the part. Generally, induction hardening is used to selectively harden areas of a part or assembly without affecting the properties of the part as a whole.
U.S. Pat. No. 2,454,039, issued to Cox, discloses a high-frequency induction heating apparatus for heating articles, such as gears and the like, for hardening purposes, and has for its object a completely automatic heater wherein the gears or other parts to be heated are moved separately upwardly into a heating position and then heated and discharged from the device. The apparatus includes a supporting structure provided with a horizontal rack or table at the top. In the table are mounted in spaced relation with each other two gear supports by means of which a gear is elevated to heating position with respect to a high frequency heating coil just above the support. Between the work supports on the table are provided supporting means for a stack of untreated gears, together with a pusher slidable on the table for pushing the lowermost gear of the stack onto one or the other of the work supports. Suitable driving motors are provided for the work supports and the pusher, together with automatic control means for causing the gears to be pushed one by one off the bottom of the stack alternately onto the supports where they are heated.
U.S. Pat. No. 3,502,310, issued to Coffman, discloses a hot plate billet heater and method of heating employing a billet heater having elongated hot plates which engage and heat an advancing line of billets at closely controlled temperature conditions, releasing the billets at predetermined intervals and, while released, feeding them forward to deliver a leading heated billet for processing. Means are provided for taking away the heated billets as delivered but at a higher travel speed to cause them to move the greater required distance while the main conveyor means is operating.
There is a need for further induction heating apparatus and methods, and more specifically, to induction heating apparatus, carriers, and methods for hardening metal objects and parts.