INFLUENCE OF POST WELD HEAT-TREATMENT ON THE DYNAMIC STRAIN-AGING OF C-MN STEELS

Welded C-Mn steel structures are generally subjected to a post weld he at treatment (PWHT), consisting in a 100 minute isothermal holding at 600 degrees C, whose major role is to reduce the residual stresses in the heat affected zone. Nevertheless, an associated decrease of the ma terial 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 degrees C temperature range, with a view to practical design, it is important to accurately characterize the beneficial effect of PWHT on DSA. In or der to study this influence of PWHT on the DSA in welded joints, tensi le tests as well as internal friction tests were performed on C-Mn ste els and manual metal are welded joints, in the as-welded state or afte r PWHT. After PWHT, the decrease of both the Snoek and the Cold Work P eak heights, which are observed on the internal friction spectrum, can be clearly associated to the lowering of the sensitivity to DSA measu red by tensile tests.