Abstract
The uniaxial creep rupture strength of Mod. 9Cr-1Mo steel welded joints is lower than that of the base metal, due to the existence of the heat affected zone (HAZ) softening region which is formed by welding heat. In this paper, the multiaxial creep damage of welded joints is evaluated analytically using the Finite Element Method (FEM), so as to study the width of HAZ softening region that affects creep damage.
To begin with, creep strain equations were established based on the result of uniaxial creep tests. The uniaxial creep damage was evaluated analytically using these creep strain equations, and the result agreed with the experimental result. It was found from the uniaxial creep damage analysis that the effect of HAZ softening region on creep rupture strength is negligible, in the case of relatively narrow HAZ softening region compared with the diameter of welded joints.
The analytical result of internal pressure creep tests using the FEM was correlated well with the experimental result. Therefore, the creep damage of welded joints including HAZ softening region can be evaluated analytically.
