Controversial Issues Concerning Development of Hi-Cr Ferrite Heat-resisting Steel Tube(Part I)

Discussed here in the essay are some controversial issues related to development of the hi-Cr ferrite heatresisting steel tube.Described is the critical reason for the early-stage damage of such tube, i.e., the IV type cracking as occurring in the welding HAZ.Also analyzed are the property of the transversal creep rupture of the base metal and the weld joint of a certain hi-Cr ferrite heat-resisting steel tube as imported from abroad, and the progress as made in localization of such tube, and the creep property of the similar tube as made at home.Analyses are carried out for the II type chemical composition design of T/P/G91 steels as well as relevant objections.Discussed are the macro mechanics law and micro dynamic evolution of the said steel, and the reasons for that the creep deterioration of the weld seam HAZ is faster than that of the base metal, and that the additional w(Mn+Ni)of the weld seam metal chemical composition of G91 steel is ≤ 1.4%.