PRACTICAL APPLICATION AND WELDABILITY OF FERRITIC HEAT RESISTANT MATERIALS FOR SUPER-CRITICAL ONCE-THROUGH BOILER

摘要

As a substitute material for conventional Mod.9Cr-lMo steel (ASME T91/P91), tungsten added ferritic heat resistance materials such as ASME T23/P23, ASME T92/P92, and ASME T122/P122 have been developed. Especially, ASME P122 has 1.3 times greater strength than ASME P91 at high temperature (approx. 600℃) and excellent steam oxidation resistance. In this study, characterization tests (Charpy impact test, creep rupture test et al) with ASME P122 welded joint prepared by several welding procedures (Gas tungsten arc welding; GTAW, Submerged arc welding; SAW) were conducted. As a result, it is concluded that: a) Each welding procedure shows good weldability and good mechanical characteristics. b) Charpy notch-toughness has good relation with the welded deposition rates and its heat input. c) On the welded joints with low heat input charpy notch-toughness is almost constant at the high deposition rates. d) Low heat input SAW is very applicable because of its high deposition rate.