Abstract: A boiler tube having improved high temperature strength, improved high temperature corrosion resistance, and resistivity to embrittlement during the service thereof, comprising an outer surface layer and an inner part, the outer surface layer consisting essentially, by weight, of 0.03-0.20% carbon, 1.5-4.0% silicon, 0.1-3.0% manganese, 13-25% chromium, 13-40% nickel, 0.5-3.0% at least one kind selected from the group consisting of molybdenum and tungsten, 0.05-0.5% at least one kind selected from the group consisting of titanium, niobium and vanadium, and the balance iron and inevitable impurities, the inner part consisting essentially, by weight, of 0.03-0.20% carbon, 0.3-1.0% silicon, 0.1-3.0% manganese, 13-25% chromium, 13-40% nickel, 0.5-3.0% at least one kind selected from the group consisting of molybdenum and tungsten, 0.05-0.5% at least one kind selected from the group consisting of titanium, niobium and vanadium, and the balance iron and inevitable impurities. Boron of 0.001-0.

Abstract: A highly corrosion resistant ferritic stainless steel comprising;C .ltoreq. 0.015%Si .ltoreq. 0.30%Mn .ltoreq. 0.30%P .ltoreq. 0.040%S .ltoreq. 0.030%Cr : 18.00 to 25.00%Ni .ltoreq. 0.20%Cu .ltoreq. 0.20%Mo : 1.50 - 3.50%N .ltoreq. 0.015%Ti : 4 .times. (C + N)% to 0.50%, andNb : 8 .times. (C + N)% to 1.00%, whereinTi/Nb : 0.5 to 1.2(Ti + Nb)/(C + N) .gtoreq. 8.0 in case of (C + N) < 0.017%, and(Ti + Nb)/(C + N) .ltoreq. 16.0 in case of (C + N) .gtoreq. 0.017%with the balance being iron and unavoidable impurities.