Patent attributes
A duplex stainless steel containing C, Si, Mn, P, S, Al, Ni, Cr, Mo, N (nitrogen, O (oxygen), Ca, Mg, Cu, B, and W, and the balance Fe and impurities, where a number of oxide-based inclusions, which have a total content of Ca and Mg of 20 to 40% by mass and also have a long diameter of not less than 7 μm, is not more than a 10 per 1 mm2 of the cross section perpendicular to the working direction, or further, the number of oxide-based inclusions, which have a content of S of not less than 15% by mass and also have a long diameter of not less than 1 μm, is not more than 10 per 0.1 mm2 of the cross section perpendicular to the working direction. Particularly, the contents of Cu, B and W are desirably 0.2 to 2%, 0.001 to 0.01%, and 0.1 to 4% by mass, respectively.
