| 摘要 |
To form a welded joint having a sufficiently high fracture toughness value ´c by butting welding high strength steel plates having a yield strength of the 355 MPa class or more and a plate thickness of over 50 mm by electron beam welding, the butt welded joint is made one where the hardness of the weld metal is 110% to 220% of the hardness of the base material and where the width of the weld metal is 20%A or less of the base material plate thickness. More preferably, the amount of O in the weld metal of the welded joint is made 20 ppm or more and the amount of oxides of a grain size of 2.0 µm or more is made 10/mm 2 or less; the weld metal of the welded joint is made to contain Ni in an amount of 1 to 4 mass% and contain it in more than an amount of 0.2 mass% or more of the content of the base material; or, when using as the base material a steel material containing as Ni in an amount of 2.5 mass% or more, making the content of Ni contained in the weld metal of the welded joint, by mass%, over 4% to 8%. |
