Patent ID: 8250966

Claim:
A method for manufacturing bellows, comprising the steps of: I: forming an untreated bellows from a flat base plate, the base plate comprising 15 to 30 wt % of Cr, 5 to 40 wt % of Ni, 0.9 to 6 wt % of Al, less than 1 wt % of Mo, less than 0.1 wt % of Mn, less than 0.1 wt % of C, less than 0.1 wt % of S, less than 0.1 wt % of P and a balance of Fe and an unavoidable impurity relative to 100 wt % of the base plate; and II: heating the untreated bellows at a temperature within a range of 750 to 895° C. in an atmosphere which contains water and hydrogen and in which the volume ratio of hydrogen to water (H 2 /H 2 O) is in the range of 2×10 3 to 1×10 12 , thereby forming an Al 2 O 3 passivation film on a surface of the untreated bellows.