Effect of Carbon on Creep Rupture Strength and Toughness of 9Cr-2Mo Heat-resisting Steels with V and Nb

Abstract

The effect of carbon on creep rupture properties and room-temperature toughness of (910)Cr-(1.82)Mo heat resisting steels with V and Nb was studied. The amount of carbon content was varied from 0.02% to 0.23% in order to improve toughness without decrease in creep rupture strength. The difference in creep rupture strength and Charpy absorbed energy between 10Cr-2Mo steels and 9Cr-1.8Mo steels was studied with respect to the ratio of δ-ferrite to martensite, the precipitates, and the microstructure.
The results indicated that the 9Cr-1.8Mo-0.1V-0.05Nb steels with 0.05-0.14%C tempered at 800°C showed good toughness, and that 10⁴h rupture strength of the steel was as high as that of SUS 316 at 550°Cand SUS 304 austenitic stainless steel at 600°C. It was concluded that the optimum amount of δ-ferrite with respect to both creep rupture strength and Charpy absorbed energy was 1020%.