the opening and welding of the double t beam design, fine.
if, however, the external surfaces must be smoothed evenly, it is necessary to make the bevels on the two lembies, to make the welding material penetrate as much as possible.
there are three basic types of cianphrine, where it is always necessary to leave a few millimeters of frontal flat surface, to support the fusion bath and at the same time ensure complete penetration:
a v, where the two bevels are made only on the upper surface, with a maximum angle of 45°.
a x, where four bevels are performed, two above and two below, with a maximum angle of 45°.
a u, where the two bevels, performed only on the upper side, are radiated and form a u.
with all these cianfrinatures on the big thicknesses, you can and you must obtain complete continuity of the material, because the welding of carry, not only fills, but protrudes both above and below.