Effect of nitrogen on C-Mn steel welds containing titanium and boron

The effect of nitrogen in the range of 80 to 240 ppm on the microstructure and properties of C-Mn shielded metal arc welds containing Ti and B has been studied. It was found that nitrogen interacted with both elements and, by a combination of solute and microstructural changes, affected mechanical properties in either a positive or a negative manner. Toughness of a previously optimized composition (400 ppm Ti, 40 ppm B) was particularly degraded by nitrogen. It is concluded that nitrogen is an integral part of weld metal chemistry and should be considered of equal importance as the microalloying elements themselves.