| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel having superior performance at a welded joint and particularly a structural steel for welding, and to provide a manufacturing method therefor. SOLUTION: This manufacturing method comprises deoxidizing a molten steel in a stage in which the steel contains dissolved oxygen, with Nb; casting it; and solidifying it. Then, Nb primarily deoxidizes the molten steel to a little extent because of having a low deoxidizing power, and leaves much dissolved oxygen in the molten steel after having been deoxidized with Nb. As a result, a large quantity of fine Nb oxides can be produced by secondary deoxidization in a casting and solidifying stage. Thus manufactured steel includes uniformly dispersed particles of a complex oxide mainly containing an oxide phase of Nb with particle diameters of 1 nm to 3μm, in an amount of 10μg or more and 1 mg or less per cubic centimeter of a steel product. The steel for welding with the use of such a steel as to contain Nb oxides greatly improves HAZ characteristics. COPYRIGHT: (C)2005,JPO&NCIPI
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