FERRITIC STAINLESS STEEL SHEET EXCELLENT IN DIFFUSION JOINABILITY AND ITS PRODUCTION

摘要

PURPOSE: To improve the diffusion joinability of an Al-contg. ferritic stainless steel by regulating the compsn. of a surface oxidized film. CONSTITUTION: A ferritic stainless steel contg. Al is used as a base material, and as to an oxidized film formed on the surface, either one or plural among (a) the concn. of N in the range of 100Åfrom the surface is regulated to <=7.0 atomic %, (b) metals constituting the oxides in the oxidized film satisfy, by atom, Al%/(Fe%+Cr%+Al%)<=0.75 and (c) metals constituting the oxides in the oxidized film satisfy Al%/0%<=0.5 is satisfied. Preferably, the thickness of the surface oxidized film is regulated to <=1000Å, and the 10-point average roughness R2 of the surface in accordance with the C direction orthogonally crossed to the rolling direction is regulated to <=1.0μm. This stainless steel is annealed in an H2 -N2 reducing atmosphere of >=70vol.% H2 concn. under the conditions of the annealing temp. of TDP=-60 to -40, TS=700 to 950 and TDP>=0.036×TS-90.6 in the case of defining the dew point as TDP( deg.C) and the steel sheet temp. as TS( deg.C).