Butt-welded joint of welded structure, and method for manufacturing the same

A method for manufacturing a butt-welded joint of a welded structure, the method including:

• irradiating a first high-energy density beam to a butt portion between a pair of target metals to form a weld bead having a width of W on an irradiated side surface as a first irradiation step;
• and
• irradiating a second high-energy density beam, from a side of the butt-welded joint from which the first high-energy density beam is irradiated, to heat an irradiated portion to not less than Ac1 to form a pair of altered zones having a band shape extending in parallel to the weld bead as a second irradiation step, the pair of the altered zones consisting of a pair of heat-affected portions and molten and solidified metals located on a right side and a left side relative to the center of the weld bead in the width direction, wherein
• an amount of heat inputted in the second irradiation step is not less than 2% and not more than 30% of the amount of heat inputted in the first irradiation step,
• each of the pair of the altered zones has a width of not less than 0.1 W and not more than 10 W, and a thickness of not less than 0.1 mm and not more than 10 mm,
• a distance between each inner edge of the pair of the altered zones and the center of the weld bead in the width direction is not less than 0 and not more than 4 W, and
• a distance between each outer edge of the pair of the altered zones and the center of the weld bead in the width direction is not less than 0.6 W and not more than 14 W.