Titanium micro-alloying effect

Titanium microalloys in steel ensure the formation of fine carbides and nitrides. These keep the grain in the heat-affected zone fine and prevent it from becoming coarse during welding. Coarse grain makes the weld brittle and prone to cracking. So you have to watch the heat input. Too much heat or slow cooling kills the effect because the particles then coarsen. Use filler materials that are matched to the titanium content of the base material, and keep the interpass temperature in check, then the structure stays nicely fine-grained.