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

Abstract

A steel material for an electron-beam welded joint, said steel material containing, by mass, at least the following: 0.02-0.10% carbon, 0.05-0.30% silicon, 1.5-2.5% manganese, more than 0.004% and no more than 0.05% aluminum, 0.005-0.015% titanium, and 0.0020-0.0060% nitrogen. The amounts of phosphorus, sulfur, and oxygen in said steel material are limited to at most 0.015%, at most 0.010%, and at most 0.0035% by mass, respectively, with the remainder of said steel material comprising iron and unavoidable impurities. Said steel material has an index (CeEBB) of 0.42% to 0.65%, and in the thicknesswise middle of a cross-section of said steel material parallel to the thickness direction of the steel material, the number of inclusion particles having equivalent circular diameters of at least 1.0 [mu]m is at most 20 per square millimeter and the number of inclusion particles that contain at least 10% titanium and have equivalent circular diameters of at least 0.05 [mu]m and less than 0.5 [mu]m is at least 103 per square millimeter.

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 portion to be welded with a plate-like or foil-like insert metal interposed on the groove surface, and a manufacturing method thereof, and further relates to a groove of the steel material. An electron beam welded joint formed by irradiating an electron beam to the welded part with embedded metal on the surface. [0002] This application claims priority based on Japanese Patent Application No. 2010-260531 for which it applied in Japan on November 22, 2010, and the content is incorporated herein by reference. Background technique [0003] In recent years, in response to CO, one of the causes of global warming, 2 The reduction of gas and the future depletion of fossil fuels such as petroleum are actively trying to utilize renewable natural energy. Wind power is also considered one of the promising renewable energy sources, an...

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Problems solved by technology

Regarding δc, since the size of the test piece affects the fracture toughness obtained by the CTOD (Crack Tip Opening Displacement: crack tip opening displacement) test, it can be obtained even in a small test such as the conventional V-notch Charpy impact test. Good results, in the CTOD test for welded joints of large steel structures, it may not be possible to obtain a good fracture toughness value δc of 0.5mm or more at 0°C

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