Mechanical properties on high Cr-Mo steels at elevated temperature (V); Tensile, creep and relaxation properties of Mod.9Cr-1Mo steel plate and tube for steam generator.

not registered; not registered; not registered; Yoshida, Eiichi; not registered

In this study, tensile, creep and relaxation test in air were performed in order to examine the mechanical properties of Mod.9Cr-1Mo steel which is a candidate material for once throuth type steam generator of large scale fast breeder reactor. Tested materials were plate(12mmt) simulating heat exchenger tube and heat exchenger tube of Mod.9Cr-1Mo steel and 9Cr-2Mo steel was also tested as reference material. Results obtained are summarized as follows. (1)Tensile properties (a)Ultimate tensile strength and 0.2% yield strength of Mod.9Cr-1Mo steels were higher than the tentative Su and Sy values of the design allowable stress in the test temperature below 600C. (b)Ultimate tensile strength of Mod.9Cr-1Mo steels plate and tube were higher than that of 9Cr-2Mo Steels. (3)The difference in ultimate tensile strength and 0.2% yield strength between steel plate and tube could not be found in these tests. (2)Creep properties (a)Creep rupture strength of Mod.9Cr-1Mo steel plate and tube was higher than the tentative S value of the design creep-rupture stress intensity at 500600C, and this tendency is significant in the range of longer rupture time. (b)For the relation between steady creep rate and creep rupture time, steady creep rates obtained in this study coincided well with the of tentative creep strain equation. (c)Creep rupture strength of Mod.9Cr-1Mo steel plate and tube was higher than that of 9Cr-2Mo steel. (3)Relaxation properties (a)In the strain range of 0.10.5%, stress rapidly relaxed during the short hold time, and stress relaxation tended to be saturate beyond 50hours. These relaxation stresses became large in higher temperature and higher strain level. (b)Stress relaxation behavior was predicted approximately by tentative creep equation of Mod.9Cr-1Mo steel. The analysis of these test results is continued to develop of evaluation method of material strength.