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

Abstract

An electron-beam welded joint including, as a composition of a steel, by mass%, at least, 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%, Mg: 0.0003% to 0.0027%, Ca: 0.0003% to 0.0027%, 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%, Al: limited to 0.015% or less, P: limited to 0.015% or less, S: limited to 0.010% or less, a balance consisting of iron and unavoidable impurities, wherein amounts in mass% of Mg and Ca in the composition of the steel satisfy 0.0006% ‰¤ Mg + Ca ‰¤ 0.0040%, 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 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 Mg of 7% or more and having an equivalent circle diameter of 0.05 µm or more and less than 0.5 µm is 1 × 10 3 to 1 × 10 5 pieces / mm 2 at the thickness center portion.

Description

technical field [0001] The present invention relates to a steel material for electron beam welding which is welded by irradiating an electron beam to a welded part, and a manufacturing method thereof, and further relates to an electron beam welded joint formed by irradiating the welded part of the steel material with an electron beam. [0002] This application claims priority based on Patent Application No. 2010-260492 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 oil 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] Regions most suitable for wind power generation are regions where constant strong winds can be expected. Ther...

AI Technical Summary

Problems solved by technology

Therefore, conventionally, the thickness and size of steel plates that can be welded by high-energy-density beam welding have been limited by the capabilities of welding equipment and the size of the vacuum chamber.

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