PURPOSE: To efficiently and surely remove beads in a stable state regardless of the sizes of a shape steel by specifying the angle between a flange and a plasma torch, the angle of the thread in the threaded part in the plasma torch and the shape of a nozzle.
CONSTITUTION: The angle θ1 between the flange 1a of the shape steel 1 in the progressing direction of gouging and the plasma torch 2 is specified to 20 to 40°. The angle θ2 between the flange 1a in the direction orthogonal with the progressing direction of gouging and the plasma torch is specified to 50 to 70°. The angle θ the thread in the threaded part 3 is specified to 6 to 7° and the shape of the threaded part is formed of one line to increase the intensity of swirling flow of the plasma operation gas. The shape of the nozzle 4 of the plasma torch is so formed as to cover the entire part of the bead part by specifying the diameter D of the nozzle injection port to 3.0 to 3.5 and the length L of the nozzle injection port to 8 to 10mm so as to blur the concentrating property of an arc to some extent.
SHIRAKAWA YOSHIHIKO
FUJIMOTO KUNIHARU
