Patent ID: 7361236
Filing Date: 2008-04-22
Classification: C21D,C22C

Abstract:
1. A stainless steel having a microstructure of martensite, a yield strength of 759 MPa or higher and a brittle-to-ductile fracture transition temperature vTrs lower than −30° C., and consisting essentially of a C content of 0.02 to 0.1 mass %, a Si content of 0.05 to 1 mass %, a Mn content of 0.05 to 1.5 mass %, a P content of not more than 0.03 mass %, a S content of not more than 0.01 mass %, a Cr content of 9 to 15 mass %, a Ni content of 0.1 to 7.0 mass %, a N content of not more than 0.1 mass % an Al content of 0.0005 to 0.05 mass %, and at least one of Ti, V and Nb at a content of 0.005 to 0.5 mass %, at a content of 0.005 to 0.5 mass % and at a content of 0.005 to 0.5 mass %, respectively, the residual being Fe and impurities, and said microstructure of martensite contains carbides wherein the maximum length of M 3 C carbides in the steel is 10 to 200 nm in the direction of the minor axis.