Patent Number: 
Section: description

With reference to the drawing, a preferred embodiment of the annealing apparatus 10 of the present invention is there shown and comprises an elongated tube 12 having a first end 14 secured to and supported by a base 16. The other or second end 18 of the tube 12 is open. The tube 12, furthermore, is constructed of a nonmetallic material capable of withstanding high temperatures, such as a quartz tube. A plate 20 is disposed across the tube 12 adjacent to, but spaced upwardly from, its end 14 thus forming a chamber 22 between the base 16, tube 12 and plate 20. The plate 20 also includes a plurality of through openings 24 for a purpose to be subsequently described. The tube 12 is dimensioned to receive a portion of an elongated tubular metal workpiece 26, such as an automotive fuel fill pipe, within its interior so that a first end 28 of the workpiece 26 is spaced upwardly from the plate 20. A cap 50 functionally engages the workpiece 26 and supports the workpiece 26 within the tube 12 so that the other or second end 30 of the workpiece 26 protrudes outwardly from the second end 18 of the tube 12. Alternatively, a support extending between the base 16 and workpiece 26 may be used to hold the workpiece 26 within the tube 12. The workpiece 26 includes a formed or expanded portion 32 which extends only partway along the longitudinal length of the workpiece 26 and this portion 32 is positioned within the tube 12. In practice, it is desired to only anneal the formed portion 32 of the workpiece 26 to thereby maintain the strength and hardness of the remainder or unformed portion of the workpiece 26. An induction coil 36 is coaxially disposed around only the formed portion 32 of the workpiece 26. Preferably, the induction coil 36 is positioned exteriorly of the tube 12. The induction coil 36 is electrically connected to any conventional energization source 38 so that, upon energization of the induction coil 36 by the source 38, the induction coil 36 induces localized heating only in the form or expanded portion 32 of the workpiece 26. In operation, in order to minimize discoloration of the workpiece 26 during the annealing process, particularly when the workpiece 26 is made of stainless steel, nitrogen and/or hydrogen is flowed both through and around the workpiece 26 both prior to and during the annealing process to create an oxygen-free environment within the tube during the annealing process. In the preferred embodiment of the invention, a valve 53 is opened to allow the hydrogen and/or nitrogen (hereinafter referred to as xe2x80x9cinertxe2x80x9d) gas to flow from an inert gas source into the interior of the workpiece 26 via the chamber 22 for about five seconds to fill the interior of the workpiece with the inert gas and exhaust through the second end of the workpiece 26. Thereafter, a second valve 51 is opened thus allowing the inert gas to flow from the inert gas source 40 through fluid ports formed in the cap 50 and downwardly along the sides of the workpiece 26. The inert gas flow through the second valve 51 is greater than through the first valve 53 so that the inert gas flows downwardly around the outer surface of the workpiece 26 and then up through the workpiece 26. The cap 50 preferably seals the tube 12 to the workpiece 26. After the second valve 51 is opened, the coil 36 is energized for about sixteen seconds thereby reaching the desired annealing temperature of about 1975xc2x0 F. Thereafter, the coil 36 is deenergized, and the inert gas continues to cool the workpiece 26. After cooling, the workpiece 26 is removed from the tube 12. A primary advantage of the present invention is that, since the induction coil is only disposed around the formed portion 32 of the workpiece 26, only the formed portion 32 of the workpiece 26 is annealed during the annealing process. This formed portion typically forms less than half of the longitudinal length of the workpiece 26 so that the hardness of the workpiece in its unformed portion is maintained and unaffected by the annealing process. Therefore, it can be seen that the present invention provides a simple and yet effective apparatus for annealing only a portion of a workpiece. Having described my invention, however, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.