Evaluation of creep damage in a welded joint of modified 9Cr-1Mo steel

Li, Y.; 門馬 義雄*; 本郷 宏通*; 田淵 正明*

Journal of Nuclear Materials, 405(1), p.44 - 49, 2010/10

https://doi.org/10.1016/j.jnucmat.2010.07.033

This paper aims to evaluate the creep damage of modified 9Cr-1Mo steel under 600C operating conditions, using constitutive equations based on the continuum damage mechanics. Specimens of base metal, a simulated fine-grained heat affected zone, and a thin (thick) welded joint were kept under stress from 80 to 160 MPa at 600C. During the creep tests of thick plate welded joint specimens, the application of stress was suspended several times, and the creep damage as indicated by the void distribution was examined quantitatively using a laser microscope. The combined effect of the equivalent creep strain and the stress triaxial factor was considered and introduced into the constitutive equations with the aid of a finite element method. The logarithms of m and 1/ in the continuum damage mechanics equations were determined to have a linear correlation with the ratio of the applied stress to the yield stress for homogeneous materials. In this way, the damage distribution and evolution in the fine-grained heat affected zone were evaluated successfully.