Effect of Chromium Content on Creep Rupture Properties of a High Chromium Ferritic Heat Resisting Steel

Abstract

The effect of chromium content in the range of 10 to 13% on the mechanical properties has been investigated of a heat resisting steel for turbine rotors. It is revealed that increase in chromium content brings about increased amounts of dissolved chromium and the Cr2(C,N) type carbides, both of which enhance room temperature and elevated-temperature strengths. However, excessive addition of chromium to about 13% results in the formation of delta-ferrite, which is detrimental to creep rupture strength, especially on the long-term side. Thus, the optimum chromium content is considered to be at around 11.5%. © 1989, The Iron and Steel Institute of Japan. All rights reserved.