EFFECTS OF DEOXIDATION PRACTICE ON THE TRANSFORMATION BEHAVIOR AND TOUGHNESS OF STEEL WELDS.

The fundamental factors controlling the development of microstructures in C-Mn steel weldments were studied, with particular emphasis on gas metal arc (GMA) welding. We conclude that the major role of manganese in the weld metal transformation kinetics is to restrict the growth of the grain boundary ferrite allotriomorphs (and, indirectly, Widmanstaetten ferrite) until the degree of undercooling reaches the point where intergranular nucleation of acicular ferrite is energetically feasible. In the present investigation, a maximum in the impact properties was observed at about 1. 6 wt-% Mn in the weld metal, in agreement with that previously reported for shielded metal arc (SMA) welding with basic electrodes. This manganese content seems to represent the optimal manganese level for C-Mn steel weldments, particularly with respect to low-temperature toughness.