Patent ID: 8623154

Claim:
An electron-beam welded joint obtained by applying an electron-beam welding to a steel, the steel comprising as a composition, by mass %, C: 0.02% to 0.10%, 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 defined by a following Formula 1 is 0.49% to 0.60%, a C/CeEB, which is a ratio of an amount in mass % of C in the steel relative to the index value CeEB of the steel, is 0.04 to 0.18, a number of oxides 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 oxides 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 1×10 3 pieces/mm 2 to 1×10 5 pieces/mm 2 at the thickness center portion, the index value of hardenability after the electron-beam welding, CeEB=C+(9/40)Mn+(1/15)Cu+(1/15)Ni+(1/5)Cr+(1/5)Mo+(1/5)V (Formula I) where C, Mn, Cu, Ni, Cr, Mo and V represent amounts in mass % of each element contained in the composition of the steel.