25%Cr-28%Ni 耐熱鋼の高温諸性質におよぼす Mo, N および C の影響

概要

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Creep rupture strength has been measured at 700℃ and microstructure has been examined during aging at 700, 800, and 900℃ in 25Cr-28Ni steels containing up to 6%M, 0.54%N, and 0.35%C. Sigma phase is formed both at grain boundaries and within grains in the steels with low nitrogen and high molybdenum content. Precipitation of chromium nitride (Cr_2N) in addition to sigma phase takes place in the steels containing low nitrogen and low molybdenum content. Only chromium nitride (Cr_2N) is precipitated by grain boundary reaction, then grains become in being covered with that in the steels containing low molybdenum and high nitrogen content. A large amount of Cr_<23>C_6 is precipitated within all over the grain in the steels with high carbon content. Addition of up to 2%Mo increases remarkably the creep rupture strength, but further addition of molybdenum more than 2% does not increase so much the strength. Nitrogen without molybdenum improves on it slightly, but the molybdenum-bearing steels containing more than 0.2%N gives the highest strength. Carbon up to 0.2% with 2%Mo improves on high temperature strength, but further addition of carbon does not improve on it. Creep rupture strength of nitrogen-bearing steels with low carbon content is higher than that of steels with high carbon content. The steels with a higher recrystallization temperature give a higher creep rupture strength at 700℃.
社団法人日本鉄鋼協会の論文
1970-07-01