Ferritic stainless steel for biofuel supply system part, biofuel supply system part, ferritic stainless steel for exhaust heat recovery unit, and exhaust heat recovery unit

摘要

An aspect of a ferritic stainless steel contains, by mass %: C: 0.03% or less; N: 0.03% or less; Si: more than 0.1% to 1% or less; Mn: 0.02% to 1.2%; Cr: 15% to 23%; Al: 0.002% to 0.5%; and either one or both of Nb and Ti, with the remainder being Fe and unavoidable impurities, wherein Expression (1) and Expression (2) illustrated below are satisfied, an oxide film is formed on a surface thereof, and the oxide film contains Cr, Si, Nb, Ti and Al in a total cationic fraction of 30% or more,
8(C+N)+0.03≦Nb+Ti≦0.6  (1)Si+Cr+Al+{Nb+Ti−8(C+N)}≧15.5  (2).

主权项

1. A ferritic stainless steel for a biofuel supply system part comprising, by mass %:
C: 0.03% or less; N: 0.03% or less; Si: more than 0.1% to 1% or less; Mn: 0.02% to 1.2%; Cr: 15% to 23%; Al: 0.002% to 0.5%; and either one or both of Nb and Ti, with the remainder being Fe and unavoidable impurities, wherein Expression (1) and Expression (2) illustrated below are satisfied, and wherein an oxide film is formed on a surface thereof and carbonitrides containing either one or both Nb and Ti are produced on the surface by heat treatment in a vacuum atmosphere containing N2 with a vacuum of 10−2 torr to 1 torr, and the oxide film contains Cr, Si, Nb, Ti and Al in a total cationic fraction of 30% or more and Cr in a cationic fraction of 20% or more,
8(C+N)+0.03≦Nb+Ti≦0.6  (1)Si+Cr+Al+{Nb+Ti−8(C+N)}≦15.5  (2) each element symbol represents the content (mass %) of the element in Expression (1) and Expression (2).