| 摘要 |
<p>An electron-beam welded joint including, 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%, O: 0.0010% to 0.0035%, 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%, S: limited to 0.010% or less, P: limited to 0.015% or less, Al: limited to 0.004% or less, and a balance consisting of iron and unavoidable impurities, wherein an index value CeEB is 0.49% to 0.60%, a number of oxides having an equivalent circle diameter of 1.0 µm or more is 20 pieces/mm 2 or less, and a number of oxides having an equivalent circle diameter of 0.05 µm or more and less than 0.5 µm is 1 × 10 3 pieces/mm 2 to 1 × 10 5 pieces/mm 2 at a thickness center portion.</p> |
