The prior austenite grain size was measured in a direction normal to the columnar grain structure. Ferrite grain size measurement was done with the image analysis software PAX-it ^TM.

The results obtained showed that the total nitrogen content of the weld metal, which ranged between 84 to 86 ppm is not affected by the welding current and speed an does not affect the subsequent microstructure development. On the other hand, the total weld oxygen content increased with welding current but reduced with increasing welding speed. There is however a considerable reduction in oxygen concentration with increasing welding speeds. The total oxygen content of the weld metal decreased from 827 to 153 ppm as welding speed increased from 5.3 to 15.3mm/s. The prior austenite grain size also showed a reduced from 150 to 108 µm with increase of welding speed from 9.3 to 15.3 mm/s. The prior austenite grain size appears to be controlled by pinning of the grain boundaries by fine non-metallic inclusions less than 0.3 mm whereas larger inclusion sizes favor nucleation of acicular ferrite.