| 摘要 |
In order to make the depth of penetration in the weld bead portion uniform and obtain a bead shape having a flat bottom without spiking and meltdown during continuous hot rolling by bonding a plurality of hot-rolled steel materials using a laser beam, the following methods are employed: (A) a method of butt welding wherein center gas is blown against the welding portion asymmetrically to the optical axis of the laser beam while side gas is being blown thereagainst from the side, the method comprising conducting welding while the center of laser-induced plasma is shifted in the welding direction from the center of the laser beam by a distance 0.2 to 0.5 times as much as a reference plasma diameter determined from the laser output and the beam diameter, and the type and flow rate of the center gas; or (B) a method comprising scanning the butt line with the laser beam during the laser welding at a speed of 2 to 10 m/min, and simultaneously oscillating the laser beam in the direction vertical to the butt line at a frequency of 40 to 80 Hz at an amplitude of 0.4 to 1.0 mm. Alternatively, (C) in order to prevent formation of blow holes in the weld bead, to make the depth of penetration in the weld bead portion uniform, and to obtain a bead shape having a flat bottom without spiking and excessive penetration, laser welding is conducted while a filler wire of an iron series base material, containing from 0.05 to 3% of one or at least two elements selected from aluminum, silicon, titanium and manganese, is being supplied to the welding portion. Moreover, (D) in order to stably supply a filler wire to the butt portion with high supply accuracy, the filler wire W is passed through a wire supply nozzle having a curved portion, and the filler wire is supplied toward the welding point along the welding line. |
