Originally posted by Acer
The failed port a wrap I saw had been welded badly. But even if your welding is good, a home welder cannot avoid the effect of the heat affected zone. As the work cools down in air, the mechanical properties of the parent metal change, and this often leaves a brittle zone close to the weld. So even if your weld is spot on, you may have weakened the parent metal..that's why in manufacturing companies, fabrications will go through a heat treatment process to anneal the work and eliminate stresses due to welding, followed by controlled cooling to give the desired physical properties, something that could only be done in a kiln with temperature control.
If you know what you're doing, and are allowing for all this, then fine. If you're not sure, then don't put home made items in safety critical situations.