| 摘要 |
An electron-beam welded joint including, as a composition of a steel, by mass%, C: 0.02% to 0.1%, Si: 0.03% to 0.30%, Mn: 1.5% to 2.5%, Ti: 0.005 to 0.015%, N: 0.0020 to 0.0060%, Al: more than 0.004% to 0.05%, Nb: 0% to 0.020%, V: 0% to 0.030%, Cr: 0% to 0.50%, Mo: 0% to 0.50%, Cu: 0% to 0.25%, Ni: 0% to 0.50%, B: 0% to 0.0030%, Ca: 0% to 0.0050%, P: limited to 0.015% or less, S: limited to 0.010% or less, O: limited to 0.0035% or less, and a balance consisting of iron and unavoidable impurities, wherein an index value CeEB of hardenability after electron-beam welding obtained by the composition of the steel is 0.49% to 0.60%, a number of inclusion particles having an equivalent circle diameter of 1.0 µm or more is 20 pieces/mm 2 or less at a thickness center portion in a cross-section along a thickness direction of the steel, and a number of particles containing Ti of 10% or more and having an equivalent circle diameter of 0.05 µm or more and less than 0.5 µm is 1 x 10 3 pieces/mm 2 or more at the thickness center portion. |
