Apparatus for spot annealing tubing

Abstract

In the manufacture of tubing, and particularly finned tubing, for use by the heat transfer industry in the manufacture of heat exchangers, annealed ends and lands are desirable in certain applications to facilitate the assembly of the tubes to headers and baffles by expanding techniques. Such spot-annealed portions can be produced on a continuous basis by the described apparatus in which the moving tube is passed through a heating chamber which reciprocates on a carriage in the direction of tube movement. The heating chamber has a pair of spaced, power-actuated clamps which grip the tubing at the ends of a discrete length portion. The heating chamber and carriage are moved with the tube while it is clamped to provide sufficient heating time to anneal the discrete length portion. The carriage then returns to its starting position. Heating of the discrete clamped tubing portion can be by a resistance technique through the clamps or by other techniques such as induction heating or gas radiant heat. If desired, an inert gas can be supplied to the heating chamber to prevent oxidation and/or discoloration. Also, if desired, a quench can be supplied in a secondary chamber positioned on the carriage immediately downstream of the heating chamber to prevent post-oxidation of the annealed tube.