Study on Mechanical Properties of P92 Steel Welded Joint of the Main SteamPipe of Ultra Supercritical Unit After 50,000 Hours Service

Abstract

Combined with a scanning electron microscope, this paper carried out a tensile test and a bending test to study the mechanical properties of P92 steel welded joint of the main stream pipe after the joint was in service for 50,000 hours. The results show that the tensile strength and hardness of the P92 steel weld metalare higher than those of the base metal after it was treated at a high temperaturefor 50,000 hours, but the plasticity is lower than that of the base metal. This is related to the precipitation and growth of Laves and M₂₃ C₆ phases in the steel during treatment; after the metal was treated at a high temperature for 50,000 hours, the number of Laves phases is larger and the size is bigger than that in the base metal. The Laves phases are precipitated rapidly along the austenite grain boundary and martensite lath boundaryand then distributed in the grain boundary, lath boundary, and plate strip boundary, reducing the strength and toughness of the matrix.