Corrosion-resistant alloy heat transfer tubes for heat-recovery boilers

摘要

A corrosion-resistant austenitic alloy suitable for use in heat transfer tubes for heat-recovery boilers which withstands uniform corrosion, intergranular corrosion, and stress corrosion cracking in refuse-fired boilers and black-liquor combustion boilers. The alloy consists essentially, on a weight basis, of C: not more than 0.05%, Si: not more than 4%, Mn: not more than 7.5%, Ni: 25-55%, Cr: more than 20% and not more than 35%, Mo: an amount satisfying the following inequality (1) when Mn(%)≦2.5 or inequality (2) when 2.5≦Mn(%)≦ 7.5, PPMo(%)≦5.8--[Ni(%)/10] (1)PP Mo(%)≦7.5- -[Ni(%)/10] (2)PPoptionally one or more of Nb, Ti, Zr, and V: 0.1-3% in total, one or more of Cu, Co, and W: 0.1- 5% in total, N: 0.1-0.3%, Al: not more than 0.5%, and at least one rare earth metal: 0. 01-0.1% in total, and the balance of Fe and incidental impurities in which the content of P is not more than 0.030% and that of S is not more than 0.010%.