Abstract
Characteristics of oxide inclusions in steel weld metals with varying acicular ferrite (AF) fractions, which were produced by gas metal arc welding using controlled CO2 (10%, 30%, and 50%) and titanium contents (by placing ultra-fine Ti wire), were statistically investigated. The correlation between identified phases in the oxide inclusions and AF formation was discussed from the viewpoint of AF formation mechanism. For high AF fraction samples, we confirmed that all oxide inclusions include Mn-Si-Al-Ti-O amorphous phases. By contrast, an amorphous phase was never observed for low AF fraction samples. Additionally, we confirmed that a few of the amorphous oxides created a Mn-depleted zone (MDZ), which suggested that the MDZ formed by Mn-Si-Al-Ti-O amorphous phase stimulates AF formation.
