METHOD FOR IMPROVING WATER VAPOR OXIDATION RESISTANCE OF HIGH CHROMIUM FERRITIC HEAT RESISTANT STEEL FOR BOILER AND HIGH CHROMIUM FERRITIC HEAT RESISTANT STEEL FOR BOILER EXCELLENT IN WATER VAPOR OXIDATION RESISTANCE

摘要

PROBLEM TO BE SOLVED: To provide ferritic heat resistant steel for a boiler excellent in water vapor oxidation resistance. ;SOLUTION: In ferritic heat resistant steel contg. 8.0 to 13.5% Cr, respectively, the content of S is controlled to 0.002 to 0.04%, and that of Si is controlled to ≤0.7%. In particular, the relations among the contents of Cr, S and Si are desirably controlled so as to satisfy the following inequality: inequality I: [% Cr]+23×[%Si]+210×[%S]≥15. Moreover, desirably, the average Bo value determined by formula II and the average Md value determined by formula III lie in a region surrounded by the straight lines connecting the points A and B, B and C, C and D and D and A in the fig. (including the case of being on the lines): formula II: the average Bo value = ΣXi.(Bo)i, and formula III: the average Md value = ΣXi.(Md)i.;COPYRIGHT: (C)2000,JPO