Heiwa, you claim to have an engineering background from school, but this statement just proved that statement a lie. You see, there's a difference between engineering stress-strain behavior and true stress-strain behavior.
Engineering stress-strain behavior normalizes the stress-strain curve based on the original cross-sectional area of steel. This allows engineers to accurately asses the behavior of the element based on the original constructed dimensions of the shape.
True stress-strain behavior, what pure scientists and most of the writers of articles on wikipedia use, are only interested in the actual material itself, not engineering properties.
By using the latter, you've more than proven you don't use engineering on a daily basis and either forgot or never learned the engineering principles in the first place
Furthermore, heat is detrimental to full perimeter welds. This is because the perimeter of the steel increases and since steel and the weld material have different coefficients of thermal expansion it induces shear into the weld plane. It's not that hard to figure out. Do the math. Oh wait, you CANT.
