Patent ID: 7686897
Filing Date: 2010-03-30
Classification: C21D,C22C

Abstract:
1. A martensitic stainless steel seamless pipe, characterized by consisting of, by mass %, C: 0.15 to 0.22%, Si: 0.1 to 1.0%, Mn: 0.10 to 1.00%, Cr: 12.00 to 14.00%, P: 0.020% or less, S: 0.010% or less, N: 0.05% or less, O (Oxygen): 0.0060% or less, Al: 0 to 0.1%, Ni: 0 to 0.5%, Cu: 0 to 0.25%, Ca: 0 to 0.0050% and at least one element selected from at least one group mentioned below (in total 0.005 to 0.200 mass % in case of including two or more kinds of these elements), and the balance Fe and impurities: the first group: V: 0.005 to 0.200%, Nb; 0.005 to 0.200%, and Ti: 0.005 to 0.200 mass %, respectively, the second group: B: 0.0005 to 0.0100 mass %, and also characterized by satisfying either the following inequalities (1), (2), (4) and (5) or the following inequalities (1), (3), (4) and (5): wherein C* is an effective solute carbon content (mass %) defined by the following equation (6), N* is an effective solute nitrogen content (mass %) defined by equation (7), and Cr* is a Cr equivalent defined by equation (8), H1 of inequality (2) is the amount (mass %) of residual hydrogen in an as-rolled steel pipe, and H2 of inequality (3) is the amount (mass %) of residual hydrogen in the steel pipe after a heat treatment, and a symbol of element in each equation or inequality is a content (mass %) of the respective element: