wood burning stoves outdoor wood furnace outdoor wood boiler design WOOD BURNING STOVES Grade 304L stainless is less likely to crack after welding than 409 'titanium enhanced'. Ductility is a measure of the material's ability to bend permanently without breaking, measured by elongation. In wood burning stoves, the intense heat will cause immense expansion and distortion. This creates high stress on the walls and welds. The higher elongation 304L/ER308LSi will absorb these stresses much better than the 409 steel. In fact the areas next to welds on 409 stainless have reduced toughness and are more prone to cracking than the 304L/ER308LSi combination.