INDUCTOR AND METHOD FOR ANNEALING WORK HARDENED PORTIONS OF STRUCTURAL BEAMS

摘要

INDUCTOR AND METHOD FOR ANNEALING WORK HARDENED PORTIONS OF STRUCTURAL BEAMS A method and inductor are provided for annealing the corners of an elongate hollow structural beam in which the corners become work hardened when the beam is produced by cold working initially flat metal plate to the hollow beam configuration. The corners of the beam are inductively heated progressively along the length of the beam in a manner which concentrates heat in the corners and controls the spreading of heat into the sides of the beam from the corners so that the work hardened areas are annealed to provide for the corners and walls to be more uniform in hardness and strength in connection with use of the beam as a structural member. The inductor for so controlling the heating encircles the beam and has arcuate portions each magnetically coupled with a corner of the beam and progressively diverging with respect to the walls of the beam adjacent thereto, and portions between the arcuate portions which overlie the side walls of the beam and are offset radially outwardly with respect to the arcuate portions.