Electron-beam welded joint, steel material for electron-beam welding, and manufacturing method therefor

Abstract

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.

Description

Technical field [0001] The present invention relates to a steel material for electron beam welding that is welded by irradiating a welded portion with an electron beam and a method for manufacturing the same, and further relates to an electron beam welding joint formed by irradiating a welded portion of the steel with an electron beam. [0002] This application claims priority based on the patent application No. 2010-260485 filed in Japan on November 22, 2010, and the content is incorporated herein. Background technique [0003] In recent years, in order to reduce CO, which is one of the causes of global warming, 2 Gas and to cope with the depletion of fossil fuels such as petroleum in the future, we are actively trying to use renewable natural energy. Wind power is also one of the promising renewable energy sources, and large-scale wind power plants are being built. [0004] The most suitable area for wind power generation is an area that can expect constant strong winds. Therefor...

AI Technical Summary

Problems solved by technology

Since the size of the test piece affects the fracture toughness, even if good results can be obtained by small tests such as the conventional V-notch Charpy impact test, it may not be possible to obtain good results in the CTOD test for welded joints of large steel structures. Get good fracture toughness values ​​δc

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