Influence of Post Weld Heat Treatment on the Dynamic Strain Aging of C-Mn Steels

Abstract
Welded C-Mn steel structures are generally subjected to a post weld heat treatment (PWHT), consisting in a 100 minute isothermal holding at 600°C, whose major role is to reduce the residual stresses in the heat affected zone. Nevertheless, an associated decrease of the material sensitivity to Dynamic Strain Aging (DSA) seems to be observed. Since this DSA phenomenon, generally induces a large increase in the ultimate tensile strength and a ductility loss in the 100-300°C temperature range, with a view to practical design, it is important to accurately characterize the beneficial effect of PWHT on DSA. In order to study this influence of PWHT on the DSA in welded joints, tensile tests as well as internal friction tests were performed on C-Mn steels and manual metal arc welded joints, in the as-welded state or after PWHT. After PWHT, the decrease of both the Snoek and the Cold Work Peak heights, which are observed on the internal friction spectrum, can be clearly associated to the lowering of the sensitivity to DSA measured by tensile tests.