Patent ID: 6740174
Filing Date: 2004-05-25
Classification: C21D,C22C

Abstract:
A soft Cr-containing steel having a composition, on a % by mass basis, comprising:C: from about 0.001% to about 0.020%; Si: more than about 0.10% and less than about 0.50%; Mn: less than about 2.00%; P: less than about 0.060%; S: less than about 0.008%; Cr: from about 12.0% or more to about 16.0%; Ni: from about 0.05% to about 1.00%; N: less than about 0.020%; Nb: from about 0.30% to less than 1.00%; Mo: more than about 0.80% and less than about 3.00%; and Fe and incidental impurities, wherein the contents of alloying elements, silicon and molybdenum, represented by Si and Mo, respectively, on a % by mass basis, satisfy the following formula (1) Si&lE;1.2âˆ’0.4Moâ€ƒâ€ƒ(1) and, regarding the state of Mo in the steel, a ratio of (112) diffraction intensity of the Laves phase, (Fe,Cr)2(Mo,Nb), to (111) diffraction intensity of Nb carbonitride, Nb(C,N), A value =I{(Fe,Cr)2(Mo,Nb)}(112)/I{Nb(C,N)}(111), is less than 0.4 based on X-ray diffraction of extraction residues of precipitates in the steel.